diff --git a/toolchain/check/convert.cpp b/toolchain/check/convert.cpp
index 24ee8e4711ce..435f9422f1d8 100644
--- a/toolchain/check/convert.cpp
+++ b/toolchain/check/convert.cpp
@@ -42,84 +42,91 @@
 
 namespace Carbon::Check {
 
-// Marks the initializer `init_id` as initializing `target.storage_id`.
-static auto MarkInitializerFor(SemIR::File& sem_ir, SemIR::InstId init_id,
-                               ConversionTarget& target) -> void {
-  if (!target.storage_id.has_value()) {
-    return;
-  }
+// Overwrites the contents of the storage arg of the initializing expression
+// `init_id` with the inst at `target.storage_id`, and returns the ID that
+// should now be used to refer to `init_id`'s storage. Has no effect and returns
+// `target.storage_id` unchanged if `target.storage_id` is None or `init_id`
+// doesn't have a storage arg.
+static auto OverwriteStorageArg(SemIR::File& sem_ir, SemIR::InstId init_id,
+                                const ConversionTarget& target)
+    -> SemIR::InstId {
   CARBON_CHECK(target.is_initializer());
-  auto return_slot_arg_id = FindReturnSlotArgForInitializer(sem_ir, init_id);
-  if (return_slot_arg_id.has_value()) {
-    // Replace the temporary in the return slot with a reference to our target.
-    CARBON_CHECK(sem_ir.insts().Get(return_slot_arg_id).kind() ==
-                     SemIR::TemporaryStorage::Kind,
-                 "Return slot for initializer does not contain a temporary; "
-                 "initialized multiple times? Have {0}",
-                 sem_ir.insts().Get(return_slot_arg_id));
-    target.storage_id = target.storage_access_block->MergeReplacing(
-        return_slot_arg_id, target.storage_id);
+  if (!target.storage_id.has_value()) {
+    return SemIR::InstId::None;
   }
+  auto storage_arg_id = FindStorageArgForInitializer(sem_ir, init_id);
+  if (!storage_arg_id.has_value()) {
+    return target.storage_id;
+  }
+  // Replace the temporary in the return slot with a reference to our target.
+  CARBON_CHECK(sem_ir.insts().Get(storage_arg_id).kind() ==
+                   SemIR::TemporaryStorage::Kind,
+               "Return slot for initializer does not contain a temporary; "
+               "initialized multiple times? Have {0}",
+               sem_ir.insts().Get(storage_arg_id));
+  return target.storage_access_block->MergeReplacing(storage_arg_id,
+                                                     target.storage_id);
 }
 
-// For a value or initializing expression using a copy value representation,
-// copy the value into a temporary object.
-static auto CopyValueToTemporary(Context& context, SemIR::InstId init_id)
+// Materializes and returns a temporary initialized from the initializer
+// `init_id`. If `init_id` has a storage arg, it must be a `TemporaryStorage`;
+// if not, this function allocates one for it.
+static auto MaterializeTemporary(Context& context, SemIR::InstId init_id)
     -> SemIR::InstId {
-  // TODO: Consider using `None` to mean that we immediately materialize and
-  // initialize a temporary, rather than two separate instructions.
-  auto init = context.insts().Get(init_id);
-  auto temporary_id = AddInst<SemIR::TemporaryStorage>(
-      context, SemIR::LocId(init_id), {.type_id = init.type_id()});
+  auto& sem_ir = context.sem_ir();
+  auto category = SemIR::GetExprCategory(sem_ir, init_id);
+  CARBON_CHECK(SemIR::IsInitializerCategory(category));
+  auto init = sem_ir.insts().Get(init_id);
+  auto storage_id = FindStorageArgForInitializer(sem_ir, init_id);
+  if (!storage_id.has_value()) {
+    CARBON_CHECK(category == SemIR::ExprCategory::ReprInitializing);
+    // The initializer has no storage arg, but we want to produce an ephemeral
+    // reference, so we need to allocate temporary storage.
+    storage_id = AddInst<SemIR::TemporaryStorage>(
+        context, SemIR::LocId(init_id), {.type_id = init.type_id()});
+  }
+
+  CARBON_CHECK(
+      sem_ir.insts().Get(storage_id).kind() == SemIR::TemporaryStorage::Kind,
+      "Storage arg for initializer does not contain a temporary; "
+      "initialized multiple times? Have {0}",
+      sem_ir.insts().Get(storage_id));
   return AddInstWithCleanup<SemIR::Temporary>(context, SemIR::LocId(init_id),
                                               {.type_id = init.type_id(),
-                                               .storage_id = temporary_id,
+                                               .storage_id = storage_id,
                                                .init_id = init_id});
 }
 
-// Commits to using a temporary to store the result of the initializing
-// expression described by `init_id`, and returns the location of the
-// temporary. If `discarded` is `true`, the result is discarded, and no
-// temporary will be created if possible; if no temporary is created, the
-// return value will be `SemIR::InstId::None`.
-static auto FinalizeTemporary(Context& context, SemIR::InstId init_id,
-                              bool discarded) -> SemIR::InstId {
+// Discards the initializer `init_id`. If `init_id` intrinsically writes to
+// memory, this materializes a temporary for it and starts its lifetime.
+//
+// TODO: We should probably start its lifetime unconditionally, because
+// types with by-copy representations can still have nontrivial destructors.
+static auto DiscardInitializer(Context& context, SemIR::InstId init_id)
+    -> void {
   auto& sem_ir = context.sem_ir();
-  auto return_slot_arg_id = FindReturnSlotArgForInitializer(sem_ir, init_id);
-  if (return_slot_arg_id.has_value()) {
-    // The return slot should already have a materialized temporary in it.
-    CARBON_CHECK(sem_ir.insts().Get(return_slot_arg_id).kind() ==
-                     SemIR::TemporaryStorage::Kind,
-                 "Return slot for initializer does not contain a temporary; "
-                 "initialized multiple times? Have {0}",
-                 sem_ir.insts().Get(return_slot_arg_id));
-    auto init = sem_ir.insts().Get(init_id);
-    return AddInstWithCleanup<SemIR::Temporary>(
-        context, SemIR::LocId(init_id),
-        {.type_id = init.type_id(),
-         .storage_id = return_slot_arg_id,
-         .init_id = init_id});
+  auto storage_id = FindStorageArgForInitializer(sem_ir, init_id);
+  if (!storage_id.has_value()) {
+    CARBON_CHECK(SemIR::GetExprCategory(sem_ir, init_id) ==
+                 SemIR::ExprCategory::ReprInitializing);
+    return;
   }
 
-  if (discarded) {
-    // Don't invent a temporary that we're going to discard.
-    return SemIR::InstId::None;
-  }
-
-  // The initializer has no return slot, but we want to produce a temporary
-  // object. Materialize one now.
-  return CopyValueToTemporary(context, init_id);
+  // init_id writes to temporary storage, so we need to materialize a temporary
+  // for it.
+  MaterializeTemporary(context, init_id);
 }
 
-// Materialize a temporary to hold the result of the given expression if it is
-// an initializing expression.
-static auto MaterializeIfInitializing(Context& context, SemIR::InstId expr_id)
+// If `expr_id` is an initializer, materializes it and returns the resulting
+// ephemeral reference expression. Otherwise, returns `expr_id`.
+static auto MaterializeIfInitializer(Context& context, SemIR::InstId expr_id)
     -> SemIR::InstId {
-  if (GetExprCategory(context.sem_ir(), expr_id) ==
-      SemIR::ExprCategory::Initializing) {
-    return FinalizeTemporary(context, expr_id, /*discarded=*/false);
+  if (SemIR::IsInitializerCategory(
+          SemIR::GetExprCategory(context.sem_ir(), expr_id))) {
+    return MaterializeTemporary(context, expr_id);
+  } else {
+    return expr_id;
   }
-  return expr_id;
 }
 
 // Helper to allow `MakeElementAccessInst` to call `AddInst` with either a
@@ -169,9 +176,9 @@ static auto GetAggregateElementConversionTargetKind(SemIR::File& sem_ir,
     CARBON_CHECK(init_repr.kind != SemIR::InitRepr::Dependent,
                  "Aggregate should not have dependent init kind");
     if (init_repr.kind == SemIR::InitRepr::InPlace) {
-      return ConversionTarget::FullInitializer;
+      return ConversionTarget::InPlaceInitializing;
     }
-    return ConversionTarget::Initializer;
+    return ConversionTarget::Initializing;
   }
 
   // Otherwise, we want a value representation for each element.
@@ -250,7 +257,7 @@ static auto ConvertTupleToArray(Context& context, SemIR::TupleType tuple_type,
   if (auto tuple_literal = value.TryAs<SemIR::TupleLiteral>()) {
     literal_elems = sem_ir.inst_blocks().Get(tuple_literal->elements_id);
   } else {
-    value_id = MaterializeIfInitializing(context, value_id);
+    value_id = MaterializeIfInitializer(context, value_id);
   }
 
   // Check that the tuple is the right size.
@@ -312,7 +319,7 @@ static auto ConvertTupleToArray(Context& context, SemIR::TupleType tuple_type,
     auto init_id =
         ConvertAggregateElement<SemIR::TupleAccess, SemIR::ArrayIndex>(
             context, value_loc_id, value_id, src_type_inst_id, literal_elems,
-            ConversionTarget::FullInitializer, return_slot_arg_id,
+            ConversionTarget::InPlaceInitializing, return_slot_arg_id,
             array_type.element_type_inst_id, target_block, i, i);
     if (init_id == SemIR::ErrorInst::InstId) {
       return SemIR::ErrorInst::InstId;
@@ -352,7 +359,7 @@ static auto ConvertTupleToTuple(Context& context, SemIR::TupleType src_type,
     literal_elems_id = tuple_literal->elements_id;
     literal_elems = sem_ir.inst_blocks().Get(literal_elems_id);
   } else {
-    value_id = MaterializeIfInitializing(context, value_id);
+    value_id = MaterializeIfInitializer(context, value_id);
   }
 
   // Check that the tuples are the same size.
@@ -496,7 +503,7 @@ static auto ConvertStructToStructOrClass(
     literal_elems_id = struct_literal->elements_id;
     literal_elems = sem_ir.inst_blocks().Get(literal_elems_id);
   } else {
-    value_id = MaterializeIfInitializing(context, value_id);
+    value_id = MaterializeIfInitializer(context, value_id);
   }
 
   // Check that the structs are the same size.
@@ -563,10 +570,10 @@ static auto ConvertStructToStructOrClass(
                             .GetAs<SemIR::VtableDecl>(canonical_vtable_decl_id)
                             .vtable_id,
            .specific_id = vtable_class_type->specific_id});
-      auto init_id = AddInst<SemIR::InitializeFrom>(context, value_loc_id,
-                                                    {.type_id = vptr_type_id,
-                                                     .src_id = vtable_ptr_id,
-                                                     .dest_id = dest_id});
+      auto init_id = AddInst<SemIR::InPlaceInit>(context, value_loc_id,
+                                                 {.type_id = vptr_type_id,
+                                                  .src_id = vtable_ptr_id,
+                                                  .dest_id = dest_id});
       new_block.Set(i, init_id);
       continue;
     }
@@ -677,7 +684,7 @@ static auto ConvertStructToClass(Context& context, SemIR::StructType src_type,
   // point to.
   bool need_temporary = !target.is_initializer();
   if (need_temporary) {
-    target.kind = ConversionTarget::Initializer;
+    target.kind = ConversionTarget::Initializing;
     target.storage_access_block = &target_block;
     target.storage_id = target_block.AddInst<SemIR::TemporaryStorage>(
         SemIR::LocId(value_id), {.type_id = target.type_id});
@@ -801,12 +808,12 @@ static auto IsValidExprCategoryForConversionTarget(
       return category == SemIR::ExprCategory::Value ||
              category == SemIR::ExprCategory::DurableRef ||
              category == SemIR::ExprCategory::EphemeralRef ||
-             category == SemIR::ExprCategory::Initializing;
+             category == SemIR::ExprCategory::ReprInitializing ||
+             category == SemIR::ExprCategory::InPlaceInitializing;
     case ConversionTarget::RefParam:
     case ConversionTarget::UnmarkedRefParam:
       return category == SemIR::ExprCategory::DurableRef ||
-             category == SemIR::ExprCategory::EphemeralRef ||
-             category == SemIR::ExprCategory::Initializing;
+             category == SemIR::ExprCategory::EphemeralRef;
     case ConversionTarget::DurableRef:
       return category == SemIR::ExprCategory::DurableRef;
     case ConversionTarget::CppThunkRef:
@@ -814,9 +821,10 @@ static auto IsValidExprCategoryForConversionTarget(
     case ConversionTarget::ExplicitAs:
     case ConversionTarget::ExplicitUnsafeAs:
       return true;
-    case ConversionTarget::Initializer:
-    case ConversionTarget::FullInitializer:
-      return category == SemIR::ExprCategory::Initializing;
+    case ConversionTarget::InPlaceInitializing:
+      return category == SemIR::ExprCategory::InPlaceInitializing;
+    case ConversionTarget::Initializing:
+      return category == SemIR::ExprCategory::ReprInitializing;
   }
 }
 
@@ -885,7 +893,7 @@ static auto CanRemoveQualifiers(SemIR::TypeQualifiers quals,
   }
 
   if (quals.HasAnyOf(SemIR::TypeQualifiers::Partial) &&
-      (!allow_unsafe || cat == SemIR::ExprCategory::Initializing)) {
+      (!allow_unsafe || SemIR::IsInitializerCategory(cat))) {
     // TODO: Allow removing `partial` for initializing expressions as a safe
     // conversion. `PerformBuiltinConversion` will need to initialize the vptr
     // as part of the conversion.
@@ -893,7 +901,7 @@ static auto CanRemoveQualifiers(SemIR::TypeQualifiers quals,
   }
 
   if (quals.HasAnyOf(SemIR::TypeQualifiers::MaybeUnformed) &&
-      (!allow_unsafe || cat == SemIR::ExprCategory::Initializing)) {
+      (!allow_unsafe || SemIR::IsInitializerCategory(cat))) {
     // As an unsafe conversion, `MaybeUnformed` can be removed from a value or
     // reference expression.
     return false;
@@ -976,18 +984,24 @@ static auto PerformBuiltinConversion(
 
     // If the source is an initializing expression, we may be able to pull a
     // value right out of it.
-    if (value_cat == SemIR::ExprCategory::Initializing &&
+    if (value_cat == SemIR::ExprCategory::ReprInitializing &&
         CanUseValueOfInitializer(sem_ir, value_type_id, target.kind)) {
       return AddInst<SemIR::ValueOfInitializer>(
           context, loc_id, {.type_id = value_type_id, .init_id = value_id});
     }
 
     // Materialization is handled as part of the enclosing conversion.
-    if (value_cat == SemIR::ExprCategory::Initializing &&
+    if (SemIR::IsInitializerCategory(value_cat) &&
         target.kind == ConversionTarget::ValueOrRef) {
       return value_id;
     }
 
+    // Final destination store is handled as part of the enclosing conversion.
+    if (value_cat == SemIR::ExprCategory::ReprInitializing &&
+        target.kind == ConversionTarget::InPlaceInitializing) {
+      return value_id;
+    }
+
     // PerformBuiltinConversion converts each part of a tuple or struct, even
     // when the types are the same. This is not done for classes since they have
     // to define their conversions as part of their api.
@@ -1370,7 +1384,7 @@ static auto IsCppEnum(Context& context, SemIR::TypeId type_id) -> bool {
 // Given a value expression, form a corresponding initializer that copies from
 // that value to the specified target, if it is possible to do so.
 static auto PerformCopy(Context& context, SemIR::InstId expr_id,
-                        ConversionTarget& target) -> SemIR::InstId {
+                        const ConversionTarget& target) -> SemIR::InstId {
   // TODO: We don't have a mechanism yet to generate `Copy` impls for each enum
   // type imported from C++. For now we fake it by providing a direct copy.
   auto type_id = context.insts().Get(expr_id).type_id();
@@ -1388,7 +1402,6 @@ static auto PerformCopy(Context& context, SemIR::InstId expr_id,
                           "cannot copy value of type {0}", TypeOfInstId);
         return context.emitter().Build(expr_id, CopyOfUncopyableType, expr_id);
       });
-  MarkInitializerFor(context.sem_ir(), copy_id, target);
   return copy_id;
 }
 
@@ -1503,14 +1516,17 @@ class CategoryConverter {
   Context& context_;
   SemIR::File& sem_ir_;
   SemIR::LocId loc_id_;
-  ConversionTarget& target_;
+  const ConversionTarget& target_;
   bool performed_builtin_conversion_;
 };
 
 auto CategoryConverter::DoStep(const SemIR::InstId expr_id,
                                const SemIR::ExprCategory category) const
     -> State {
-  CARBON_DCHECK(SemIR::GetExprCategory(sem_ir_, expr_id) == category);
+  CARBON_DCHECK(SemIR::GetExprCategory(sem_ir_, expr_id) == category ||
+                // TODO: Drop this special case once PerformCopy on C++ enums
+                // produces an initializing expression.
+                IsCppEnum(context_, target_.type_id));
   switch (category) {
     case SemIR::ExprCategory::NotExpr:
     case SemIR::ExprCategory::Mixed:
@@ -1521,15 +1537,33 @@ auto CategoryConverter::DoStep(const SemIR::InstId expr_id,
     case SemIR::ExprCategory::Error:
       return Done{SemIR::ErrorInst::InstId};
 
-    case SemIR::ExprCategory::Initializing:
+    case SemIR::ExprCategory::InPlaceInitializing:
+    case SemIR::ExprCategory::ReprInitializing:
       if (target_.is_initializer()) {
-        if (!performed_builtin_conversion_) {
-          // Don't fill in the return slot if we created the expression through
-          // a builtin conversion. In that case, we will have created it with
-          // the target already set.
-          // TODO: Find a better way to track whether we need to do this,
-          // and then make target_ immutable if possible.
-          MarkInitializerFor(sem_ir_, expr_id, target_);
+        // Overwrite the initializer's storage argument with the inst currently
+        // at target_.storage_id, if both are present. However, we skip this
+        // in certain cases:
+        // - If we created the expression through a builtin conversion, we
+        //   will have created it with the target already set.
+        // - If the type is a C++ enum, we don't actually have an initializing
+        //   expression, we're just pretending we do.
+        auto new_storage_id = target_.storage_id;
+        if (!performed_builtin_conversion_ &&
+            !IsCppEnum(context_, target_.type_id)) {
+          new_storage_id = OverwriteStorageArg(sem_ir_, expr_id, target_);
+        }
+
+        // If in-place initialization was requested, and it hasn't already
+        // happened, ensure it happens now.
+        if (target_.kind == ConversionTarget::InPlaceInitializing &&
+            category != SemIR::ExprCategory::InPlaceInitializing &&
+            SemIR::InitRepr::ForType(sem_ir_, target_.type_id)
+                .MightBeByCopy()) {
+          target_.storage_access_block->InsertHere();
+          return Done{AddInst<SemIR::InPlaceInit>(context_, loc_id_,
+                                                  {.type_id = target_.type_id,
+                                                   .src_id = expr_id,
+                                                   .dest_id = new_storage_id})};
         }
         return Done{expr_id};
       }
@@ -1540,10 +1574,10 @@ auto CategoryConverter::DoStep(const SemIR::InstId expr_id,
       // TODO: If the target is DurableRef, materialize a VarStorage instead of
       // a TemporaryStorage to lifetime-extend.
       if (target_.kind == ConversionTarget::Discarded) {
-        return Done{FinalizeTemporary(context_, expr_id, /*discarded=*/true)};
+        DiscardInitializer(context_, expr_id);
+        return Done{SemIR::InstId::None};
       } else {
-        return NextStep{.expr_id = FinalizeTemporary(context_, expr_id,
-                                                     /*discarded=*/false),
+        return NextStep{.expr_id = MaterializeTemporary(context_, expr_id),
                         .category = SemIR::ExprCategory::EphemeralRef};
       }
 
@@ -1627,7 +1661,31 @@ auto CategoryConverter::DoStep(const SemIR::InstId expr_id,
 
       // When initializing from a value, perform a copy.
       if (target_.is_initializer()) {
-        return Done{PerformCopy(context_, expr_id, target_)};
+        auto copy_id = PerformCopy(context_, expr_id, target_);
+        if (copy_id == SemIR::ErrorInst::InstId) {
+          return Done{SemIR::ErrorInst::InstId};
+        }
+        // Deal with special-case category behavior of PerformCopy.
+        switch (SemIR::GetExprCategory(sem_ir_, copy_id)) {
+          case SemIR::ExprCategory::Value:
+            // As a temporary workaround, PerformCopy on a C++ enum currently
+            // returns the unchanged value, but we treat it as an initializing
+            // expression.
+            // TODO: Drop this case once it's no longer applicable.
+            CARBON_CHECK(IsCppEnum(context_, target_.type_id));
+            [[fallthrough]];
+          case SemIR::ExprCategory::ReprInitializing:
+            // The common case: PerformCopy produces an initializing expression.
+            return NextStep{.expr_id = copy_id,
+                            .category = SemIR::ExprCategory::ReprInitializing};
+          case SemIR::ExprCategory::InPlaceInitializing:
+            // A C++ copy operation produces an ephemeral entire reference.
+            return NextStep{
+                .expr_id = copy_id,
+                .category = SemIR::ExprCategory::InPlaceInitializing};
+          default:
+            CARBON_FATAL("Unexpected category of copy operation {0}", category);
+        }
       }
 
       // When initializing a C++ thunk parameter, form a reference, creating a
@@ -1714,13 +1772,11 @@ auto Convert(Context& context, SemIR::LocId loc_id, SemIR::InstId expr_id,
     return SemIR::ErrorInst::InstId;
   }
 
-  if (target.kind != ConversionTarget::FullInitializer &&
-      (target.kind != ConversionTarget::Initializer ||
-       !SemIR::InitRepr::ForType(context.sem_ir(), target.type_id)
-            .MightBeInPlace())) {
-    // storage_id should only be used for a FullInitializer, or an Initializer
-    // if the type has an in-place init representation. This ensures we don't
-    // accidentally use it for anything else.
+  // Clear storage_id in cases where it's clearly meaningless, to avoid misuse
+  // and simplify the resulting SemIR.
+  if (!target.is_initializer() ||
+      SemIR::InitRepr::ForType(context.sem_ir(), target.type_id).kind ==
+          SemIR::InitRepr::None) {
     target.storage_id = SemIR::InstId::None;
   }
 
@@ -1830,27 +1886,21 @@ auto Convert(Context& context, SemIR::LocId loc_id, SemIR::InstId expr_id,
       CategoryConverter(context, loc_id, target, performed_builtin_conversion)
           .Convert(expr_id);
 
-  // Perform a final destination store, if necessary.
-  if (target.kind == ConversionTarget::FullInitializer) {
-    if (auto init_rep = SemIR::InitRepr::ForType(sem_ir, target.type_id);
-        init_rep.MightBeByCopy()) {
-      target.storage_access_block->InsertHere();
-      expr_id = AddInst<SemIR::InitializeFrom>(context, loc_id,
-                                               {.type_id = target.type_id,
-                                                .src_id = expr_id,
-                                                .dest_id = target.storage_id});
-    }
-  }
-
   return expr_id;
 }
 
 auto Initialize(Context& context, SemIR::LocId loc_id, SemIR::InstId storage_id,
-                SemIR::InstId value_id) -> SemIR::InstId {
+                SemIR::InstId value_id, bool for_return) -> SemIR::InstId {
+  auto type_id = context.insts().Get(storage_id).type_id();
+  if (for_return &&
+      !SemIR::InitRepr::ForType(context.sem_ir(), type_id).MightBeInPlace()) {
+    // TODO: is it safe to use storage_id when the init repr is dependent?
+    storage_id = SemIR::InstId::None;
+  }
   PendingBlock target_block(&context);
   return Convert(context, loc_id, value_id,
-                 {.kind = ConversionTarget::Initializer,
-                  .type_id = context.insts().Get(storage_id).type_id(),
+                 {.kind = ConversionTarget::Initializing,
+                  .type_id = type_id,
                   .storage_id = storage_id,
                   .storage_access_block = &target_block});
 }
diff --git a/toolchain/check/convert.h b/toolchain/check/convert.h
index f089beea0d0e..0e9a860450a2 100644
--- a/toolchain/check/convert.h
+++ b/toolchain/check/convert.h
@@ -44,17 +44,17 @@ struct ConversionTarget {
     // The result of the conversion is discarded. It can't be an initializing
     // expression, but can be anything else.
     Discarded,
-    // Convert to an initializing expression, which a subsequent operation (such
-    // as `InitializeFrom` or `Temporary`) can use to initialize `storage_id`.
-    // `storage_id` is only used if `type_id` has an in-place initializing
-    // representation; otherwise, `storage_id` can be `None`, and the resulting
-    // initializing expression can be used to initialize any object of the
-    // appropriate type.
-    Initializer,
-    // Convert to an initializing expression, and use it to initialize
-    // `storage_id` (which must not be `None`).
-    FullInitializer,
-    Last = FullInitializer
+    // Convert to an initializing expression that uses `type_id`'s initializing
+    // representation. The resulting expression will usually be a
+    // repr-initializing expression, but may be an in-place initializing
+    // expression if the source expression was. If `storage_id` is present, it
+    // is used as the storage argument for the converted expression, and it must
+    // be present if the initializing representation might be in-place.
+    Initializing,
+    // Convert to an in-place initializing expression whose storage is
+    // designated by `storage_id` (which must not be `None`)
+    InPlaceInitializing,
+    Last = InPlaceInitializing
   };
   // The kind of the target for this conversion.
   Kind kind;
@@ -72,7 +72,7 @@ struct ConversionTarget {
 
   // Are we converting this value into an initializer for an object?
   auto is_initializer() const -> bool {
-    return kind == Initializer || kind == FullInitializer;
+    return kind == Initializing || kind == InPlaceInitializing;
   }
   // Is this some kind of explicit `as` conversion?
   auto is_explicit_as() const -> bool {
@@ -91,16 +91,22 @@ auto Convert(Context& context, SemIR::LocId loc_id, SemIR::InstId expr_id,
              SemIR::ClassType* vtable_class_type = nullptr) -> SemIR::InstId;
 
 // Converts `value_id` to an initializing expression of the type of
-// `storage_id`, and returns the possibly-converted initializing expression. If
-// initialization is in-place, `storage_id` is used as the in-place storage;
-// otherwise it is used only to determine the target type. The caller is
-// responsible for assigning the returned initializing expression to the target
-// using a suitable node for the kind of initialization.
+// `storage_id`, and returns the possibly-converted initializing expression.
+// `storage_id` is used as the storage argument of the resulting expression
+// except as noted below. The caller is responsible for passing the result to an
+// inst that is documented as consuming it, such as `Assign`.
+//
+// `for_return` indicates that this conversion is initializing the operand of a
+// `return` statement. This means that `storage_id` will be the return slot
+// parameter, which isn't valid to access if the type's initializing
+// representation is not in-place, so in that case `storage_id` will be used
+// solely for its type.
 //
 // TODO: Consider making the target type a separate parameter, and making
 // storage_id optional.
 auto Initialize(Context& context, SemIR::LocId loc_id, SemIR::InstId storage_id,
-                SemIR::InstId value_id) -> SemIR::InstId;
+                SemIR::InstId value_id, bool for_return = false)
+    -> SemIR::InstId;
 
 // Convert the given expression to a value expression of the same type.
 auto ConvertToValueExpr(Context& context, SemIR::InstId expr_id)
diff --git a/toolchain/check/cpp/thunk.cpp b/toolchain/check/cpp/thunk.cpp
index fe09f3f347aa..06fde46ea7f5 100644
--- a/toolchain/check/cpp/thunk.cpp
+++ b/toolchain/check/cpp/thunk.cpp
@@ -731,10 +731,10 @@ auto PerformCppThunkCall(Context& context, SemIR::LocId loc_id,
 
   // Produce the result of the call, taking the value from the return storage.
   if (thunk_takes_return_address) {
-    result_id = AddInst<SemIR::InPlaceInit>(context, loc_id,
-                                            {.type_id = return_type_id,
-                                             .src_id = result_id,
-                                             .dest_id = return_slot_id});
+    result_id = AddInst<SemIR::MarkInPlaceInit>(context, loc_id,
+                                                {.type_id = return_type_id,
+                                                 .src_id = result_id,
+                                                 .dest_id = return_slot_id});
   }
 
   return result_id;
diff --git a/toolchain/check/cpp/type_mapping.cpp b/toolchain/check/cpp/type_mapping.cpp
index 92e9c252bf50..b79641f092e6 100644
--- a/toolchain/check/cpp/type_mapping.cpp
+++ b/toolchain/check/cpp/type_mapping.cpp
@@ -514,7 +514,8 @@ static auto InventPrimitiveClangArg(Context& context, FormInfo form)
       break;
 
     case SemIR::ExprCategory::Value:
-    case SemIR::ExprCategory::Initializing:
+    case SemIR::ExprCategory::ReprInitializing:
+    case SemIR::ExprCategory::InPlaceInitializing:
       value_kind = clang::ExprValueKind::VK_PRValue;
       break;
 
diff --git a/toolchain/check/eval_inst.cpp b/toolchain/check/eval_inst.cpp
index 84cb106f75e4..205d5607777b 100644
--- a/toolchain/check/eval_inst.cpp
+++ b/toolchain/check/eval_inst.cpp
@@ -442,7 +442,7 @@ auto EvalConstantInst(Context& /*context*/, SemIR::ImportRefUnloaded inst)
                inst);
 }
 
-auto EvalConstantInst(Context& context, SemIR::InitializeFrom inst)
+auto EvalConstantInst(Context& context, SemIR::InPlaceInit inst)
     -> ConstantEvalResult {
   // Initialization is not performed in-place during constant evaluation, so
   // just return the value of the initializer.
diff --git a/toolchain/check/return.cpp b/toolchain/check/return.cpp
index 0f0766186f7f..cf5997fb744b 100644
--- a/toolchain/check/return.cpp
+++ b/toolchain/check/return.cpp
@@ -179,7 +179,8 @@ auto BuildReturnWithExpr(Context& context, SemIR::LocId loc_id,
             GetCurrentFunctionForReturn(context).call_params_id);
         out_param_id = call_params[init_form.index.index];
         CARBON_CHECK(out_param_id.has_value());
-        expr_id = Initialize(context, loc_id, out_param_id, expr_id);
+        expr_id = Initialize(context, loc_id, out_param_id, expr_id,
+                             /*for_return=*/true);
         if (!SemIR::InitRepr::ForType(context.sem_ir(), return_type_id)
                  .MightBeInPlace()) {
           out_param_id = SemIR::InstId::None;
diff --git a/toolchain/check/testdata/alias/import_order.carbon b/toolchain/check/testdata/alias/import_order.carbon
index eaa11e7f81bd..7c2539e4379c 100644
--- a/toolchain/check/testdata/alias/import_order.carbon
+++ b/toolchain/check/testdata/alias/import_order.carbon
@@ -164,7 +164,7 @@ var a_val: a = {.v = b_val.v};
 // CHECK:STDOUT:   %.loc7_23.1: %empty_tuple.type = tuple_literal () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc7_24.1: %struct_type.v = struct_literal (%.loc7_23.1) [concrete = constants.%struct.5f2]
 // CHECK:STDOUT:   %.loc7_24.2: ref %empty_tuple.type = class_element_access file.%d_val.var, element0 [concrete = constants.%.cad]
-// CHECK:STDOUT:   %.loc7_23.2: init %empty_tuple.type to %.loc7_24.2 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc7_23.2: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc7_24.3: init %empty_tuple.type = converted %.loc7_23.1, %.loc7_23.2 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc7_24.4: init %C to file.%d_val.var = class_init (%.loc7_24.3) [concrete = constants.%C.val]
 // CHECK:STDOUT:   %.loc7_1: init %C = converted %.loc7_24.1, %.loc7_24.4 [concrete = constants.%C.val]
@@ -174,7 +174,7 @@ var a_val: a = {.v = b_val.v};
 // CHECK:STDOUT:   %.loc8_27.1: ref %empty_tuple.type = class_element_access %d_val.ref, element0 [concrete = constants.%.cad]
 // CHECK:STDOUT:   %.loc8_29.1: %struct_type.v = struct_literal (%.loc8_27.1) [concrete = constants.%struct.d07]
 // CHECK:STDOUT:   %.loc8_29.2: ref %empty_tuple.type = class_element_access file.%c_val.var, element0 [concrete = constants.%.da4]
-// CHECK:STDOUT:   %.loc8_27.2: init %empty_tuple.type to %.loc8_29.2 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc8_27.2: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc8_29.3: init %empty_tuple.type = converted %.loc8_27.1, %.loc8_27.2 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc8_29.4: init %C to file.%c_val.var = class_init (%.loc8_29.3) [concrete = constants.%C.val]
 // CHECK:STDOUT:   %.loc8_1: init %C = converted %.loc8_29.1, %.loc8_29.4 [concrete = constants.%C.val]
@@ -184,7 +184,7 @@ var a_val: a = {.v = b_val.v};
 // CHECK:STDOUT:   %.loc9_27.1: ref %empty_tuple.type = class_element_access %c_val.ref, element0 [concrete = constants.%.da4]
 // CHECK:STDOUT:   %.loc9_29.1: %struct_type.v = struct_literal (%.loc9_27.1) [concrete = constants.%struct.f0b]
 // CHECK:STDOUT:   %.loc9_29.2: ref %empty_tuple.type = class_element_access file.%b_val.var, element0 [concrete = constants.%.0f2]
-// CHECK:STDOUT:   %.loc9_27.2: init %empty_tuple.type to %.loc9_29.2 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc9_27.2: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc9_29.3: init %empty_tuple.type = converted %.loc9_27.1, %.loc9_27.2 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc9_29.4: init %C to file.%b_val.var = class_init (%.loc9_29.3) [concrete = constants.%C.val]
 // CHECK:STDOUT:   %.loc9_1: init %C = converted %.loc9_29.1, %.loc9_29.4 [concrete = constants.%C.val]
@@ -194,7 +194,7 @@ var a_val: a = {.v = b_val.v};
 // CHECK:STDOUT:   %.loc10_27.1: ref %empty_tuple.type = class_element_access %b_val.ref, element0 [concrete = constants.%.0f2]
 // CHECK:STDOUT:   %.loc10_29.1: %struct_type.v = struct_literal (%.loc10_27.1) [concrete = constants.%struct.938]
 // CHECK:STDOUT:   %.loc10_29.2: ref %empty_tuple.type = class_element_access file.%a_val.var, element0 [concrete = constants.%.851]
-// CHECK:STDOUT:   %.loc10_27.2: init %empty_tuple.type to %.loc10_29.2 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc10_27.2: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc10_29.3: init %empty_tuple.type = converted %.loc10_27.1, %.loc10_27.2 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc10_29.4: init %C to file.%a_val.var = class_init (%.loc10_29.3) [concrete = constants.%C.val]
 // CHECK:STDOUT:   %.loc10_1: init %C = converted %.loc10_29.1, %.loc10_29.4 [concrete = constants.%C.val]
diff --git a/toolchain/check/testdata/array/basics.carbon b/toolchain/check/testdata/array/basics.carbon
index b1fbe8478f68..d6a48ab4d325 100644
--- a/toolchain/check/testdata/array/basics.carbon
+++ b/toolchain/check/testdata/array/basics.carbon
@@ -147,17 +147,17 @@ var a: array(1, 1);
 // CHECK:STDOUT:   %tuple.elem0: ref %empty_tuple.type = tuple_access %a.ref, element0 [concrete = constants.%tuple.elem0]
 // CHECK:STDOUT:   %int_0: Core.IntLiteral = int_value 0 [concrete = constants.%int_0]
 // CHECK:STDOUT:   %.loc6_23.1: ref %empty_tuple.type = array_index file.%b.var, %int_0
-// CHECK:STDOUT:   %.loc6_23.2: init %empty_tuple.type to %.loc6_23.1 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc6_23.2: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc6_23.3: init %empty_tuple.type = converted %tuple.elem0, %.loc6_23.2 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %tuple.elem1: ref %empty_tuple.type = tuple_access %a.ref, element1 [concrete = constants.%tuple.elem1]
 // CHECK:STDOUT:   %int_1: Core.IntLiteral = int_value 1 [concrete = constants.%int_1]
 // CHECK:STDOUT:   %.loc6_23.4: ref %empty_tuple.type = array_index file.%b.var, %int_1
-// CHECK:STDOUT:   %.loc6_23.5: init %empty_tuple.type to %.loc6_23.4 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc6_23.5: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc6_23.6: init %empty_tuple.type = converted %tuple.elem1, %.loc6_23.5 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %tuple.elem2: ref %empty_tuple.type = tuple_access %a.ref, element2 [concrete = constants.%tuple.elem2]
 // CHECK:STDOUT:   %int_2: Core.IntLiteral = int_value 2 [concrete = constants.%int_2]
 // CHECK:STDOUT:   %.loc6_23.7: ref %empty_tuple.type = array_index file.%b.var, %int_2
-// CHECK:STDOUT:   %.loc6_23.8: init %empty_tuple.type to %.loc6_23.7 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc6_23.8: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc6_23.9: init %empty_tuple.type = converted %tuple.elem2, %.loc6_23.8 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc6_23.10: init %array_type to file.%b.var = array_init (%.loc6_23.3, %.loc6_23.6, %.loc6_23.9) [concrete = constants.%array]
 // CHECK:STDOUT:   %.loc6_1: init %array_type = converted %a.ref, %.loc6_23.10 [concrete = constants.%array]
@@ -325,7 +325,7 @@ var a: array(1, 1);
 // CHECK:STDOUT:   %tuple.elem0: ref %empty_tuple.type = tuple_access %.loc8_27.2, element0
 // CHECK:STDOUT:   %int_0: Core.IntLiteral = int_value 0 [concrete = constants.%int_0]
 // CHECK:STDOUT:   %.loc8_27.3: ref %empty_tuple.type = array_index %t.var, %int_0
-// CHECK:STDOUT:   %.loc8_27.4: init %empty_tuple.type to %.loc8_27.3 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc8_27.4: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc8_27.5: init %empty_tuple.type = converted %tuple.elem0, %.loc8_27.4 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc8_27.6: init %array_type to %t.var = array_init (%.loc8_27.5) [concrete = constants.%array]
 // CHECK:STDOUT:   %.loc8_3: init %array_type = converted %F.call, %.loc8_27.6 [concrete = constants.%array]
@@ -403,47 +403,47 @@ var a: array(1, 1);
 // CHECK:STDOUT:   %tuple.elem0.loc9: ref %empty_tuple.type = tuple_access %a.ref, element0 [concrete = constants.%tuple.elem0]
 // CHECK:STDOUT:   %int_0: Core.IntLiteral = int_value 0 [concrete = constants.%int_0]
 // CHECK:STDOUT:   %.loc9_23.1: ref %empty_tuple.type = array_index file.%b.var, %int_0
-// CHECK:STDOUT:   %.loc9_23.2: init %empty_tuple.type to %.loc9_23.1 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc9_23.2: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc9_23.3: init %empty_tuple.type = converted %tuple.elem0.loc9, %.loc9_23.2 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %tuple.elem1.loc9: ref %empty_tuple.type = tuple_access %a.ref, element1 [concrete = constants.%tuple.elem1]
 // CHECK:STDOUT:   %int_1: Core.IntLiteral = int_value 1 [concrete = constants.%int_1]
 // CHECK:STDOUT:   %.loc9_23.4: ref %empty_tuple.type = array_index file.%b.var, %int_1
-// CHECK:STDOUT:   %.loc9_23.5: init %empty_tuple.type to %.loc9_23.4 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc9_23.5: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc9_23.6: init %empty_tuple.type = converted %tuple.elem1.loc9, %.loc9_23.5 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %tuple.elem2.loc9: ref %empty_tuple.type = tuple_access %a.ref, element2 [concrete = constants.%tuple.elem2]
 // CHECK:STDOUT:   %int_2: Core.IntLiteral = int_value 2 [concrete = constants.%int_2]
 // CHECK:STDOUT:   %.loc9_23.7: ref %empty_tuple.type = array_index file.%b.var, %int_2
-// CHECK:STDOUT:   %.loc9_23.8: init %empty_tuple.type to %.loc9_23.7 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc9_23.8: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc9_23.9: init %empty_tuple.type = converted %tuple.elem2.loc9, %.loc9_23.8 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %tuple.elem3.loc9: ref %empty_tuple.type = tuple_access %a.ref, element3 [concrete = constants.%tuple.elem3]
 // CHECK:STDOUT:   %int_3: Core.IntLiteral = int_value 3 [concrete = constants.%int_3]
 // CHECK:STDOUT:   %.loc9_23.10: ref %empty_tuple.type = array_index file.%b.var, %int_3
-// CHECK:STDOUT:   %.loc9_23.11: init %empty_tuple.type to %.loc9_23.10 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc9_23.11: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc9_23.12: init %empty_tuple.type = converted %tuple.elem3.loc9, %.loc9_23.11 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %tuple.elem4.loc9: ref %empty_tuple.type = tuple_access %a.ref, element4 [concrete = constants.%tuple.elem4]
 // CHECK:STDOUT:   %int_4: Core.IntLiteral = int_value 4 [concrete = constants.%int_4]
 // CHECK:STDOUT:   %.loc9_23.13: ref %empty_tuple.type = array_index file.%b.var, %int_4
-// CHECK:STDOUT:   %.loc9_23.14: init %empty_tuple.type to %.loc9_23.13 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc9_23.14: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc9_23.15: init %empty_tuple.type = converted %tuple.elem4.loc9, %.loc9_23.14 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %tuple.elem5.loc9: ref %empty_tuple.type = tuple_access %a.ref, element5 [concrete = constants.%tuple.elem5]
 // CHECK:STDOUT:   %int_5: Core.IntLiteral = int_value 5 [concrete = constants.%int_5]
 // CHECK:STDOUT:   %.loc9_23.16: ref %empty_tuple.type = array_index file.%b.var, %int_5
-// CHECK:STDOUT:   %.loc9_23.17: init %empty_tuple.type to %.loc9_23.16 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc9_23.17: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc9_23.18: init %empty_tuple.type = converted %tuple.elem5.loc9, %.loc9_23.17 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %tuple.elem6.loc9: ref %empty_tuple.type = tuple_access %a.ref, element6 [concrete = constants.%tuple.elem6]
 // CHECK:STDOUT:   %int_6: Core.IntLiteral = int_value 6 [concrete = constants.%int_6]
 // CHECK:STDOUT:   %.loc9_23.19: ref %empty_tuple.type = array_index file.%b.var, %int_6
-// CHECK:STDOUT:   %.loc9_23.20: init %empty_tuple.type to %.loc9_23.19 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc9_23.20: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc9_23.21: init %empty_tuple.type = converted %tuple.elem6.loc9, %.loc9_23.20 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %tuple.elem7.loc9: ref %empty_tuple.type = tuple_access %a.ref, element7 [concrete = constants.%tuple.elem7]
 // CHECK:STDOUT:   %int_7: Core.IntLiteral = int_value 7 [concrete = constants.%int_7]
 // CHECK:STDOUT:   %.loc9_23.22: ref %empty_tuple.type = array_index file.%b.var, %int_7
-// CHECK:STDOUT:   %.loc9_23.23: init %empty_tuple.type to %.loc9_23.22 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc9_23.23: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc9_23.24: init %empty_tuple.type = converted %tuple.elem7.loc9, %.loc9_23.23 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %tuple.elem8.loc9: ref %empty_tuple.type = tuple_access %a.ref, element8 [concrete = constants.%tuple.elem8]
 // CHECK:STDOUT:   %int_8: Core.IntLiteral = int_value 8 [concrete = constants.%int_8]
 // CHECK:STDOUT:   %.loc9_23.25: ref %empty_tuple.type = array_index file.%b.var, %int_8
-// CHECK:STDOUT:   %.loc9_23.26: init %empty_tuple.type to %.loc9_23.25 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc9_23.26: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc9_23.27: init %empty_tuple.type = converted %tuple.elem8.loc9, %.loc9_23.26 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc9_23.28: init %array_type to file.%b.var = array_init (%.loc9_23.3, %.loc9_23.6, %.loc9_23.9, %.loc9_23.12, %.loc9_23.15, %.loc9_23.18, %.loc9_23.21, %.loc9_23.24, %.loc9_23.27) [concrete = constants.%array]
 // CHECK:STDOUT:   %.loc9_1: init %array_type = converted %a.ref, %.loc9_23.28 [concrete = constants.%array]
diff --git a/toolchain/check/testdata/array/index_not_literal.carbon b/toolchain/check/testdata/array/index_not_literal.carbon
index ca75744945d0..f9e17db36ed1 100644
--- a/toolchain/check/testdata/array/index_not_literal.carbon
+++ b/toolchain/check/testdata/array/index_not_literal.carbon
@@ -138,7 +138,7 @@ fn F(a: array({}, 3)) -> {} {
 // CHECK:STDOUT:   %.loc10_20.3: ref %array_type = temporary_storage
 // CHECK:STDOUT:   %int_0: Core.IntLiteral = int_value 0 [concrete = constants.%int_0]
 // CHECK:STDOUT:   %.loc10_20.4: ref %i32 = array_index %.loc10_20.3, %int_0
-// CHECK:STDOUT:   %.loc10_20.5: init %i32 to %.loc10_20.4 = initialize_from %.loc10_20.2 [concrete = constants.%int_1.5d2]
+// CHECK:STDOUT:   %.loc10_20.5: init %i32 to %.loc10_20.4 = in_place_init %.loc10_20.2 [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %impl.elem0.loc10_20.2: %.863 = impl_witness_access constants.%ImplicitAs.impl_witness.6bc, element0 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.0b5]
 // CHECK:STDOUT:   %bound_method.loc10_20.3: <bound method> = bound_method %int_2.loc10_16, %impl.elem0.loc10_20.2 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.bound.4e5]
 // CHECK:STDOUT:   %specific_fn.loc10_20.2: <specific function> = specific_function %impl.elem0.loc10_20.2, @Core.IntLiteral.as.ImplicitAs.impl.Convert(constants.%int_32) [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.specific_fn]
@@ -147,7 +147,7 @@ fn F(a: array({}, 3)) -> {} {
 // CHECK:STDOUT:   %.loc10_20.6: init %i32 = converted %int_2.loc10_16, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc10_20.2 [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %int_1.loc10_20: Core.IntLiteral = int_value 1 [concrete = constants.%int_1.5b8]
 // CHECK:STDOUT:   %.loc10_20.7: ref %i32 = array_index %.loc10_20.3, %int_1.loc10_20
-// CHECK:STDOUT:   %.loc10_20.8: init %i32 to %.loc10_20.7 = initialize_from %.loc10_20.6 [concrete = constants.%int_2.ef8]
+// CHECK:STDOUT:   %.loc10_20.8: init %i32 to %.loc10_20.7 = in_place_init %.loc10_20.6 [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %impl.elem0.loc10_20.3: %.863 = impl_witness_access constants.%ImplicitAs.impl_witness.6bc, element0 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.0b5]
 // CHECK:STDOUT:   %bound_method.loc10_20.5: <bound method> = bound_method %int_3, %impl.elem0.loc10_20.3 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.bound.061]
 // CHECK:STDOUT:   %specific_fn.loc10_20.3: <specific function> = specific_function %impl.elem0.loc10_20.3, @Core.IntLiteral.as.ImplicitAs.impl.Convert(constants.%int_32) [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.specific_fn]
@@ -156,7 +156,7 @@ fn F(a: array({}, 3)) -> {} {
 // CHECK:STDOUT:   %.loc10_20.9: init %i32 = converted %int_3, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc10_20.3 [concrete = constants.%int_3.822]
 // CHECK:STDOUT:   %int_2.loc10_20: Core.IntLiteral = int_value 2 [concrete = constants.%int_2.ecc]
 // CHECK:STDOUT:   %.loc10_20.10: ref %i32 = array_index %.loc10_20.3, %int_2.loc10_20
-// CHECK:STDOUT:   %.loc10_20.11: init %i32 to %.loc10_20.10 = initialize_from %.loc10_20.9 [concrete = constants.%int_3.822]
+// CHECK:STDOUT:   %.loc10_20.11: init %i32 to %.loc10_20.10 = in_place_init %.loc10_20.9 [concrete = constants.%int_3.822]
 // CHECK:STDOUT:   %.loc10_20.12: init %array_type to %.loc10_20.3 = array_init (%.loc10_20.5, %.loc10_20.8, %.loc10_20.11) [concrete = constants.%array]
 // CHECK:STDOUT:   %.loc10_20.13: init %array_type = converted %.loc10_20.1, %.loc10_20.12 [concrete = constants.%array]
 // CHECK:STDOUT:   %.loc10_20.14: ref %array_type = temporary %.loc10_20.3, %.loc10_20.13
diff --git a/toolchain/check/testdata/as/adapter_conversion.carbon b/toolchain/check/testdata/as/adapter_conversion.carbon
index 8ca58a104e27..c13b6b7da18d 100644
--- a/toolchain/check/testdata/as/adapter_conversion.carbon
+++ b/toolchain/check/testdata/as/adapter_conversion.carbon
@@ -406,7 +406,7 @@ var b: B = {.x = ()} as B;
 // CHECK:STDOUT:   %.loc14_34.2: init %i32 = converted %int_1, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc14_34.1 [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %.loc14_34.3: ref %A = temporary_storage
 // CHECK:STDOUT:   %.loc14_34.4: ref %i32 = class_element_access %.loc14_34.3, element0
-// CHECK:STDOUT:   %.loc14_34.5: init %i32 to %.loc14_34.4 = initialize_from %.loc14_34.2 [concrete = constants.%int_1.5d2]
+// CHECK:STDOUT:   %.loc14_34.5: init %i32 to %.loc14_34.4 = in_place_init %.loc14_34.2 [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %impl.elem0.loc14_34.2: %.863 = impl_witness_access constants.%ImplicitAs.impl_witness.6bc, element0 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.0b5]
 // CHECK:STDOUT:   %bound_method.loc14_34.3: <bound method> = bound_method %int_2, %impl.elem0.loc14_34.2 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.bound.4e5]
 // CHECK:STDOUT:   %specific_fn.loc14_34.2: <specific function> = specific_function %impl.elem0.loc14_34.2, @Core.IntLiteral.as.ImplicitAs.impl.Convert(constants.%int_32) [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.specific_fn]
@@ -414,7 +414,7 @@ var b: B = {.x = ()} as B;
 // CHECK:STDOUT:   %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc14_34.2: init %i32 = call %bound_method.loc14_34.4(%int_2) [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %.loc14_34.6: init %i32 = converted %int_2, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc14_34.2 [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %.loc14_34.7: ref %i32 = class_element_access %.loc14_34.3, element1
-// CHECK:STDOUT:   %.loc14_34.8: init %i32 to %.loc14_34.7 = initialize_from %.loc14_34.6 [concrete = constants.%int_2.ef8]
+// CHECK:STDOUT:   %.loc14_34.8: init %i32 to %.loc14_34.7 = in_place_init %.loc14_34.6 [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %.loc14_34.9: init %A to %.loc14_34.3 = class_init (%.loc14_34.5, %.loc14_34.8) [concrete = constants.%A.val]
 // CHECK:STDOUT:   %.loc14_34.10: ref %A = temporary %.loc14_34.3, %.loc14_34.9
 // CHECK:STDOUT:   %.loc14_36: ref %A = converted %.loc14_34.1, %.loc14_34.10
diff --git a/toolchain/check/testdata/as/basics.carbon b/toolchain/check/testdata/as/basics.carbon
index d42b914d45f5..95120e608804 100644
--- a/toolchain/check/testdata/as/basics.carbon
+++ b/toolchain/check/testdata/as/basics.carbon
@@ -160,11 +160,11 @@ let n: {.x: ()} = {.x = ()} as {.x = ()};
 // CHECK:STDOUT:   %.loc6_29.1: %struct_type.x.y = converted %.loc6_27.1, %struct [concrete = constants.%struct.005]
 // CHECK:STDOUT:   %.loc6_29.2: %empty_tuple.type = struct_access %.loc6_29.1, element0 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc6_29.3: ref %empty_tuple.type = struct_access %return.param, element0
-// CHECK:STDOUT:   %.loc6_29.4: init %empty_tuple.type to %.loc6_29.3 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc6_29.4: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc6_29.5: init %empty_tuple.type = converted %.loc6_29.2, %.loc6_29.4 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc6_29.6: %empty_tuple.type = struct_access %.loc6_29.1, element1 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc6_29.7: ref %empty_tuple.type = struct_access %return.param, element1
-// CHECK:STDOUT:   %.loc6_29.8: init %empty_tuple.type to %.loc6_29.7 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc6_29.8: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc6_29.9: init %empty_tuple.type = converted %.loc6_29.6, %.loc6_29.8 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc6_29.10: init %struct_type.x.y to %return.param = struct_init (%.loc6_29.5, %.loc6_29.9) [concrete = constants.%struct.005]
 // CHECK:STDOUT:   %.loc6_48: init %struct_type.x.y = converted %.loc6_29.1, %.loc6_29.10 [concrete = constants.%struct.005]
@@ -402,7 +402,7 @@ let n: {.x: ()} = {.x = ()} as {.x = ()};
 // CHECK:STDOUT:   %X.ref: type = name_ref X, file.%X.decl [concrete = constants.%X]
 // CHECK:STDOUT:   %.loc19_21.2: ref %X = temporary_storage
 // CHECK:STDOUT:   %.loc19_21.3: ref %empty_tuple.type = class_element_access %.loc19_21.2, element0
-// CHECK:STDOUT:   %.loc19_20.2: init %empty_tuple.type to %.loc19_21.3 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc19_20.2: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc19_21.4: init %empty_tuple.type = converted %.loc19_20.1, %.loc19_20.2 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc19_21.5: init %X to %.loc19_21.2 = class_init (%.loc19_21.4) [concrete = constants.%X.val]
 // CHECK:STDOUT:   %.loc19_21.6: ref %X = temporary %.loc19_21.2, %.loc19_21.5
diff --git a/toolchain/check/testdata/basics/raw_sem_ir/one_file.carbon b/toolchain/check/testdata/basics/raw_sem_ir/one_file.carbon
index 39b02c4e75df..e47bde3ff806 100644
--- a/toolchain/check/testdata/basics/raw_sem_ir/one_file.carbon
+++ b/toolchain/check/testdata/basics/raw_sem_ir/one_file.carbon
@@ -784,9 +784,9 @@ fn Foo[T:! type](p: T*) -> (T*, ()) {
 // CHECK:STDOUT:     inst6000016C:    {kind: BoundMethod, arg0: inst60000046, arg1: inst60000169, type: type(inst(BoundMethodType))}
 // CHECK:STDOUT:     inst6000016D:    {kind: RequireCompleteType, arg0: inst6000001C, type: type(inst(WitnessType))}
 // CHECK:STDOUT:     inst6000016E:    {kind: Call, arg0: inst6000016C, arg1: inst_block6000007F, type: type(symbolic_constant60000004)}
-// CHECK:STDOUT:     inst6000016F:    {kind: InitializeFrom, arg0: inst6000016E, arg1: inst6000004A, type: type(symbolic_constant60000004)}
+// CHECK:STDOUT:     inst6000016F:    {kind: InPlaceInit, arg0: inst6000016E, arg1: inst6000004A, type: type(symbolic_constant60000004)}
 // CHECK:STDOUT:     inst60000170:    {kind: TupleAccess, arg0: inst6000003A, arg1: element1, type: type(inst60000025)}
-// CHECK:STDOUT:     inst60000171:    {kind: TupleInit, arg0: inst_block_empty, arg1: inst60000170, type: type(inst60000025)}
+// CHECK:STDOUT:     inst60000171:    {kind: TupleInit, arg0: inst_block_empty, arg1: inst<none>, type: type(inst60000025)}
 // CHECK:STDOUT:     inst60000172:    {kind: Converted, arg0: inst60000047, arg1: inst60000171, type: type(inst60000025)}
 // CHECK:STDOUT:     inst60000173:    {kind: TupleInit, arg0: inst_block60000080, arg1: inst6000003A, type: type(symbolic_constant6000000A)}
 // CHECK:STDOUT:     inst60000174:    {kind: Converted, arg0: inst60000048, arg1: inst60000173, type: type(symbolic_constant6000000A)}
diff --git a/toolchain/check/testdata/basics/raw_sem_ir/one_file_with_textual_ir.carbon b/toolchain/check/testdata/basics/raw_sem_ir/one_file_with_textual_ir.carbon
index fc01247e24ed..08dedf7d050a 100644
--- a/toolchain/check/testdata/basics/raw_sem_ir/one_file_with_textual_ir.carbon
+++ b/toolchain/check/testdata/basics/raw_sem_ir/one_file_with_textual_ir.carbon
@@ -97,10 +97,10 @@ fn Foo(n: ()) -> ((), ()) {
 // CHECK:STDOUT:     inst6000002E:    {kind: TupleLiteral, arg0: inst_block_empty, type: type(inst60000010)}
 // CHECK:STDOUT:     inst6000002F:    {kind: TupleLiteral, arg0: inst_block60000010, type: type(inst6000001A)}
 // CHECK:STDOUT:     inst60000030:    {kind: TupleAccess, arg0: inst60000028, arg1: element0, type: type(inst60000010)}
-// CHECK:STDOUT:     inst60000031:    {kind: TupleInit, arg0: inst_block60000011, arg1: inst60000030, type: type(inst60000010)}
+// CHECK:STDOUT:     inst60000031:    {kind: TupleInit, arg0: inst_block60000011, arg1: inst<none>, type: type(inst60000010)}
 // CHECK:STDOUT:     inst60000032:    {kind: Converted, arg0: inst6000002D, arg1: inst60000031, type: type(inst60000010)}
 // CHECK:STDOUT:     inst60000033:    {kind: TupleAccess, arg0: inst60000028, arg1: element1, type: type(inst60000010)}
-// CHECK:STDOUT:     inst60000034:    {kind: TupleInit, arg0: inst_block_empty, arg1: inst60000033, type: type(inst60000010)}
+// CHECK:STDOUT:     inst60000034:    {kind: TupleInit, arg0: inst_block_empty, arg1: inst<none>, type: type(inst60000010)}
 // CHECK:STDOUT:     inst60000035:    {kind: Converted, arg0: inst6000002E, arg1: inst60000034, type: type(inst60000010)}
 // CHECK:STDOUT:     inst60000036:    {kind: TupleInit, arg0: inst_block60000012, arg1: inst60000028, type: type(inst6000001A)}
 // CHECK:STDOUT:     inst60000037:    {kind: Converted, arg0: inst6000002F, arg1: inst60000036, type: type(inst6000001A)}
@@ -271,10 +271,10 @@ fn Foo(n: ()) -> ((), ()) {
 // CHECK:STDOUT:   %.loc17_15.1: %empty_tuple.type = tuple_literal () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc17_16.1: %tuple.type = tuple_literal (%n.ref, %.loc17_15.1)
 // CHECK:STDOUT:   %tuple.elem0: ref %empty_tuple.type = tuple_access %return.param, element0
-// CHECK:STDOUT:   %.loc17_11: init %empty_tuple.type to %tuple.elem0 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc17_11: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc17_16.2: init %empty_tuple.type = converted %n.ref, %.loc17_11 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %tuple.elem1: ref %empty_tuple.type = tuple_access %return.param, element1
-// CHECK:STDOUT:   %.loc17_15.2: init %empty_tuple.type to %tuple.elem1 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc17_15.2: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc17_16.3: init %empty_tuple.type = converted %.loc17_15.1, %.loc17_15.2 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc17_16.4: init %tuple.type to %return.param = tuple_init (%.loc17_16.2, %.loc17_16.3) [concrete = constants.%tuple]
 // CHECK:STDOUT:   %.loc17_17: init %tuple.type = converted %.loc17_16.1, %.loc17_16.4 [concrete = constants.%tuple]
diff --git a/toolchain/check/testdata/choice/basic.carbon b/toolchain/check/testdata/choice/basic.carbon
index 894bee37d2b0..a90f0330b543 100644
--- a/toolchain/check/testdata/choice/basic.carbon
+++ b/toolchain/check/testdata/choice/basic.carbon
@@ -114,7 +114,7 @@ let never: Never = {};
 // CHECK:STDOUT:   %.loc6_1.3: %struct_type.discriminant = struct_literal (%.loc6_1.2) [concrete = constants.%struct]
 // CHECK:STDOUT:   %.loc6_1.4: ref %Always = temporary_storage
 // CHECK:STDOUT:   %.loc6_1.5: ref %empty_tuple.type = class_element_access %.loc6_1.4, element0
-// CHECK:STDOUT:   %.loc6_1.6: init %empty_tuple.type to %.loc6_1.5 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc6_1.6: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc6_1.7: init %empty_tuple.type = converted %.loc6_1.2, %.loc6_1.6 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc6_1.8: init %Always to %.loc6_1.4 = class_init (%.loc6_1.7) [concrete = constants.%Always.val]
 // CHECK:STDOUT:   %.loc6_1.9: ref %Always = temporary %.loc6_1.4, %.loc6_1.8
@@ -250,7 +250,7 @@ let never: Never = {};
 // CHECK:STDOUT:   %UInt.as.Copy.impl.Op.call.loc5: init %u2 = call %bound_method.loc5_7.4(%.loc5_7.2) [concrete = constants.%int_0.9fd]
 // CHECK:STDOUT:   %.loc5_7.4: ref %Ordering = temporary_storage
 // CHECK:STDOUT:   %.loc5_7.5: ref %u2 = class_element_access %.loc5_7.4, element0
-// CHECK:STDOUT:   %.loc5_7.6: init %u2 to %.loc5_7.5 = initialize_from %UInt.as.Copy.impl.Op.call.loc5 [concrete = constants.%int_0.9fd]
+// CHECK:STDOUT:   %.loc5_7.6: init %u2 to %.loc5_7.5 = in_place_init %UInt.as.Copy.impl.Op.call.loc5 [concrete = constants.%int_0.9fd]
 // CHECK:STDOUT:   %.loc5_7.7: init %Ordering to %.loc5_7.4 = class_init (%.loc5_7.6) [concrete = constants.%Ordering.val.9ea]
 // CHECK:STDOUT:   %.loc5_7.8: ref %Ordering = temporary %.loc5_7.4, %.loc5_7.7
 // CHECK:STDOUT:   %.loc5_7.9: ref %Ordering = converted %.loc5_7.3, %.loc5_7.8
@@ -272,7 +272,7 @@ let never: Never = {};
 // CHECK:STDOUT:   %UInt.as.Copy.impl.Op.call.loc6: init %u2 = call %bound_method.loc6_13.4(%.loc6_13.2) [concrete = constants.%int_1.b2c]
 // CHECK:STDOUT:   %.loc6_13.4: ref %Ordering = temporary_storage
 // CHECK:STDOUT:   %.loc6_13.5: ref %u2 = class_element_access %.loc6_13.4, element0
-// CHECK:STDOUT:   %.loc6_13.6: init %u2 to %.loc6_13.5 = initialize_from %UInt.as.Copy.impl.Op.call.loc6 [concrete = constants.%int_1.b2c]
+// CHECK:STDOUT:   %.loc6_13.6: init %u2 to %.loc6_13.5 = in_place_init %UInt.as.Copy.impl.Op.call.loc6 [concrete = constants.%int_1.b2c]
 // CHECK:STDOUT:   %.loc6_13.7: init %Ordering to %.loc6_13.4 = class_init (%.loc6_13.6) [concrete = constants.%Ordering.val.d41]
 // CHECK:STDOUT:   %.loc6_13.8: ref %Ordering = temporary %.loc6_13.4, %.loc6_13.7
 // CHECK:STDOUT:   %.loc6_13.9: ref %Ordering = converted %.loc6_13.3, %.loc6_13.8
@@ -294,7 +294,7 @@ let never: Never = {};
 // CHECK:STDOUT:   %UInt.as.Copy.impl.Op.call.loc7: init %u2 = call %bound_method.loc7_10.4(%.loc7_10.2) [concrete = constants.%int_2.788]
 // CHECK:STDOUT:   %.loc7_10.4: ref %Ordering = temporary_storage
 // CHECK:STDOUT:   %.loc7_10.5: ref %u2 = class_element_access %.loc7_10.4, element0
-// CHECK:STDOUT:   %.loc7_10.6: init %u2 to %.loc7_10.5 = initialize_from %UInt.as.Copy.impl.Op.call.loc7 [concrete = constants.%int_2.788]
+// CHECK:STDOUT:   %.loc7_10.6: init %u2 to %.loc7_10.5 = in_place_init %UInt.as.Copy.impl.Op.call.loc7 [concrete = constants.%int_2.788]
 // CHECK:STDOUT:   %.loc7_10.7: init %Ordering to %.loc7_10.4 = class_init (%.loc7_10.6) [concrete = constants.%Ordering.val.e86]
 // CHECK:STDOUT:   %.loc7_10.8: ref %Ordering = temporary %.loc7_10.4, %.loc7_10.7
 // CHECK:STDOUT:   %.loc7_10.9: ref %Ordering = converted %.loc7_10.3, %.loc7_10.8
@@ -316,7 +316,7 @@ let never: Never = {};
 // CHECK:STDOUT:   %UInt.as.Copy.impl.Op.call.loc9: init %u2 = call %bound_method.loc9_1.4(%.loc9_1.2) [concrete = constants.%int_3.975]
 // CHECK:STDOUT:   %.loc9_1.4: ref %Ordering = temporary_storage
 // CHECK:STDOUT:   %.loc9_1.5: ref %u2 = class_element_access %.loc9_1.4, element0
-// CHECK:STDOUT:   %.loc9_1.6: init %u2 to %.loc9_1.5 = initialize_from %UInt.as.Copy.impl.Op.call.loc9 [concrete = constants.%int_3.975]
+// CHECK:STDOUT:   %.loc9_1.6: init %u2 to %.loc9_1.5 = in_place_init %UInt.as.Copy.impl.Op.call.loc9 [concrete = constants.%int_3.975]
 // CHECK:STDOUT:   %.loc9_1.7: init %Ordering to %.loc9_1.4 = class_init (%.loc9_1.6) [concrete = constants.%Ordering.val.a17]
 // CHECK:STDOUT:   %.loc9_1.8: ref %Ordering = temporary %.loc9_1.4, %.loc9_1.7
 // CHECK:STDOUT:   %.loc9_1.9: ref %Ordering = converted %.loc9_1.3, %.loc9_1.8
diff --git a/toolchain/check/testdata/choice/generic.carbon b/toolchain/check/testdata/choice/generic.carbon
index 3eb5fa40b7ea..a18090840756 100644
--- a/toolchain/check/testdata/choice/generic.carbon
+++ b/toolchain/check/testdata/choice/generic.carbon
@@ -61,7 +61,7 @@ choice Always(T:! type) {
 // CHECK:STDOUT:     %.loc16_1.3: %struct_type.discriminant = struct_literal (%.loc16_1.2) [concrete = constants.%struct]
 // CHECK:STDOUT:     %.loc16_1.4: ref @Always.%Always (%Always) = temporary_storage
 // CHECK:STDOUT:     %.loc16_1.5: ref %empty_tuple.type = class_element_access %.loc16_1.4, element0
-// CHECK:STDOUT:     %.loc16_1.6: init %empty_tuple.type to %.loc16_1.5 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:     %.loc16_1.6: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:     %.loc16_1.7: init %empty_tuple.type = converted %.loc16_1.2, %.loc16_1.6 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:     %.loc16_1.8: init @Always.%Always (%Always) to %.loc16_1.4 = class_init (%.loc16_1.7) [symbolic = %Always.val (constants.%Always.val)]
 // CHECK:STDOUT:     %.loc16_1.9: ref @Always.%Always (%Always) = temporary %.loc16_1.4, %.loc16_1.8
diff --git a/toolchain/check/testdata/class/access_modifers.carbon b/toolchain/check/testdata/class/access_modifers.carbon
index eac2b01a7aa0..2ad542248e8b 100644
--- a/toolchain/check/testdata/class/access_modifers.carbon
+++ b/toolchain/check/testdata/class/access_modifers.carbon
@@ -300,7 +300,7 @@ class A {
 // CHECK:STDOUT:   %Core.IntLiteral.as.ImplicitAs.impl.Convert.call: init %i32 = call %bound_method.loc13_24.2(%int_5) [concrete = constants.%int_5.0f6]
 // CHECK:STDOUT:   %.loc13_24.2: init %i32 = converted %int_5, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call [concrete = constants.%int_5.0f6]
 // CHECK:STDOUT:   %.loc13_24.3: ref %i32 = class_element_access %return.param, element0
-// CHECK:STDOUT:   %.loc13_24.4: init %i32 to %.loc13_24.3 = initialize_from %.loc13_24.2 [concrete = constants.%int_5.0f6]
+// CHECK:STDOUT:   %.loc13_24.4: init %i32 to %.loc13_24.3 = in_place_init %.loc13_24.2 [concrete = constants.%int_5.0f6]
 // CHECK:STDOUT:   %.loc13_24.5: init %Circle to %return.param = class_init (%.loc13_24.4) [concrete = constants.%Circle.val]
 // CHECK:STDOUT:   %.loc13_25: init %Circle = converted %.loc13_24.1, %.loc13_24.5 [concrete = constants.%Circle.val]
 // CHECK:STDOUT:   return %.loc13_25 to %return.param
diff --git a/toolchain/check/testdata/class/adapter/adapt_copy.carbon b/toolchain/check/testdata/class/adapter/adapt_copy.carbon
index b6b251d5b377..c2accceb2d45 100644
--- a/toolchain/check/testdata/class/adapter/adapt_copy.carbon
+++ b/toolchain/check/testdata/class/adapter/adapt_copy.carbon
@@ -173,7 +173,6 @@ fn InTuple(c: (AdaptStruct, u32)) -> (AdaptStruct, u32) {
 // CHECK:STDOUT:   %Int.type: type = generic_class_type @Int [concrete]
 // CHECK:STDOUT:   %empty_tuple.type: type = tuple_type () [concrete]
 // CHECK:STDOUT:   %Int.generic: %Int.type = struct_value () [concrete]
-// CHECK:STDOUT:   %N: Core.IntLiteral = symbolic_binding N, 0 [symbolic]
 // CHECK:STDOUT:   %i32: type = class_type @Int, @Int(%int_32) [concrete]
 // CHECK:STDOUT:   %i32.builtin: type = int_type signed, %int_32 [concrete]
 // CHECK:STDOUT:   %complete_type.f8a: <witness> = complete_type_witness %i32.builtin [concrete]
@@ -182,7 +181,6 @@ fn InTuple(c: (AdaptStruct, u32)) -> (AdaptStruct, u32) {
 // CHECK:STDOUT:   %F.type: type = fn_type @F [concrete]
 // CHECK:STDOUT:   %F: %F.type = struct_value () [concrete]
 // CHECK:STDOUT:   %Copy.type: type = facet_type <@Copy> [concrete]
-// CHECK:STDOUT:   %Copy.Op.type: type = fn_type @Copy.Op [concrete]
 // CHECK:STDOUT:   %Destroy.type: type = facet_type <@Destroy> [concrete]
 // CHECK:STDOUT:   %DestroyOp.type.3e79c2.1: type = fn_type @DestroyOp.loc16 [concrete]
 // CHECK:STDOUT:   %DestroyOp.b0ebf8.1: %DestroyOp.type.3e79c2.1 = struct_value () [concrete]
@@ -196,14 +194,6 @@ fn InTuple(c: (AdaptStruct, u32)) -> (AdaptStruct, u32) {
 // CHECK:STDOUT:   %.25c: form = init_form %tuple.type.d78, call_param1 [concrete]
 // CHECK:STDOUT:   %InTuple.type: type = fn_type @InTuple [concrete]
 // CHECK:STDOUT:   %InTuple: %InTuple.type = struct_value () [concrete]
-// CHECK:STDOUT:   %UInt.as.Copy.impl.Op.type.68f: type = fn_type @UInt.as.Copy.impl.Op, @UInt.as.Copy.impl(%N) [symbolic]
-// CHECK:STDOUT:   %UInt.as.Copy.impl.Op.576: %UInt.as.Copy.impl.Op.type.68f = struct_value () [symbolic]
-// CHECK:STDOUT:   %Copy.impl_witness.514: <witness> = impl_witness imports.%Copy.impl_witness_table.bd0, @UInt.as.Copy.impl(%int_32) [concrete]
-// CHECK:STDOUT:   %UInt.as.Copy.impl.Op.type.2fc: type = fn_type @UInt.as.Copy.impl.Op, @UInt.as.Copy.impl(%int_32) [concrete]
-// CHECK:STDOUT:   %UInt.as.Copy.impl.Op.c10: %UInt.as.Copy.impl.Op.type.2fc = struct_value () [concrete]
-// CHECK:STDOUT:   %Copy.facet: %Copy.type = facet_value %u32, (%Copy.impl_witness.514) [concrete]
-// CHECK:STDOUT:   %.fcc: type = fn_type_with_self_type %Copy.Op.type, %Copy.facet [concrete]
-// CHECK:STDOUT:   %UInt.as.Copy.impl.Op.specific_fn: <specific function> = specific_function %UInt.as.Copy.impl.Op.c10, @UInt.as.Copy.impl.Op(%int_32) [concrete]
 // CHECK:STDOUT:   %DestroyOp.type.3e79c2.2: type = fn_type @DestroyOp.loc35 [concrete]
 // CHECK:STDOUT:   %DestroyOp.b0ebf8.2: %DestroyOp.type.3e79c2.2 = struct_value () [concrete]
 // CHECK:STDOUT: }
@@ -221,8 +211,6 @@ fn InTuple(c: (AdaptStruct, u32)) -> (AdaptStruct, u32) {
 // CHECK:STDOUT:   %Core.Copy: type = import_ref Core//prelude/parts/copy, Copy, loaded [concrete = constants.%Copy.type]
 // CHECK:STDOUT:   %Core.Destroy: type = import_ref Core//prelude/parts/destroy, Destroy, loaded [concrete = constants.%Destroy.type]
 // CHECK:STDOUT:   %Core.UInt: %UInt.type = import_ref Core//prelude/parts/uint, UInt, loaded [concrete = constants.%UInt.generic]
-// CHECK:STDOUT:   %Core.import_ref.c3c: @UInt.as.Copy.impl.%UInt.as.Copy.impl.Op.type (%UInt.as.Copy.impl.Op.type.68f) = import_ref Core//prelude/parts/uint, loc{{\d+_\d+}}, loaded [symbolic = @UInt.as.Copy.impl.%UInt.as.Copy.impl.Op (constants.%UInt.as.Copy.impl.Op.576)]
-// CHECK:STDOUT:   %Copy.impl_witness_table.bd0 = impl_witness_table (%Core.import_ref.c3c), @UInt.as.Copy.impl [concrete]
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: file {
@@ -313,20 +301,8 @@ fn InTuple(c: (AdaptStruct, u32)) -> (AdaptStruct, u32) {
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %d.var: ref %tuple.type.d78 = var %d.var_patt
 // CHECK:STDOUT:   %c.ref: %tuple.type.d78 = name_ref c, %c
-// CHECK:STDOUT:   %tuple.elem0.loc35_33.1: %AdaptCopyable = tuple_access %c.ref, element0
-// CHECK:STDOUT:   %tuple.elem0.loc35_33.2: ref %AdaptCopyable = tuple_access %d.var, element0
-// CHECK:STDOUT:   %.loc35_33.1: init %AdaptCopyable to %tuple.elem0.loc35_33.2 = initialize_from <error> [concrete = <error>]
-// CHECK:STDOUT:   %tuple.elem1.loc35_33.1: %u32 = tuple_access %c.ref, element1
-// CHECK:STDOUT:   %impl.elem0.loc35: %.fcc = impl_witness_access constants.%Copy.impl_witness.514, element0 [concrete = constants.%UInt.as.Copy.impl.Op.c10]
-// CHECK:STDOUT:   %bound_method.loc35_33.1: <bound method> = bound_method %tuple.elem1.loc35_33.1, %impl.elem0.loc35
-// CHECK:STDOUT:   %specific_fn.loc35: <specific function> = specific_function %impl.elem0.loc35, @UInt.as.Copy.impl.Op(constants.%int_32) [concrete = constants.%UInt.as.Copy.impl.Op.specific_fn]
-// CHECK:STDOUT:   %bound_method.loc35_33.2: <bound method> = bound_method %tuple.elem1.loc35_33.1, %specific_fn.loc35
-// CHECK:STDOUT:   %UInt.as.Copy.impl.Op.call.loc35: init %u32 = call %bound_method.loc35_33.2(%tuple.elem1.loc35_33.1)
-// CHECK:STDOUT:   %tuple.elem1.loc35_33.2: ref %u32 = tuple_access %d.var, element1
-// CHECK:STDOUT:   %.loc35_33.2: init %u32 to %tuple.elem1.loc35_33.2 = initialize_from %UInt.as.Copy.impl.Op.call.loc35
-// CHECK:STDOUT:   %.loc35_33.3: init %tuple.type.d78 to %d.var = tuple_init (%.loc35_33.1, %.loc35_33.2)
-// CHECK:STDOUT:   %.loc35_3: init %tuple.type.d78 = converted %c.ref, %.loc35_33.3
-// CHECK:STDOUT:   assign %d.var, %.loc35_3
+// CHECK:STDOUT:   %tuple.elem0.loc35: %AdaptCopyable = tuple_access %c.ref, element0
+// CHECK:STDOUT:   assign %d.var, <error>
 // CHECK:STDOUT:   %.loc35_29.1: type = splice_block %.loc35_29.3 [concrete = constants.%tuple.type.d78] {
 // CHECK:STDOUT:     %AdaptCopyable.ref.loc35: type = name_ref AdaptCopyable, file.%AdaptCopyable.decl [concrete = constants.%AdaptCopyable]
 // CHECK:STDOUT:     %int_32.loc35: Core.IntLiteral = int_value 32 [concrete = constants.%int_32]
@@ -336,24 +312,11 @@ fn InTuple(c: (AdaptStruct, u32)) -> (AdaptStruct, u32) {
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %d: ref %tuple.type.d78 = ref_binding d, %d.var
 // CHECK:STDOUT:   %d.ref: ref %tuple.type.d78 = name_ref d, %d
-// CHECK:STDOUT:   %tuple.elem0.loc43_10.1: ref %AdaptCopyable = tuple_access %d.ref, element0
-// CHECK:STDOUT:   %.loc43_10.1: %AdaptCopyable = acquire_value %tuple.elem0.loc43_10.1
-// CHECK:STDOUT:   %tuple.elem0.loc43_10.2: ref %AdaptCopyable = tuple_access %return.param, element0
-// CHECK:STDOUT:   %.loc43_10.2: init %AdaptCopyable to %tuple.elem0.loc43_10.2 = initialize_from <error> [concrete = <error>]
-// CHECK:STDOUT:   %tuple.elem1.loc43_10.1: ref %u32 = tuple_access %d.ref, element1
-// CHECK:STDOUT:   %.loc43_10.3: %u32 = acquire_value %tuple.elem1.loc43_10.1
-// CHECK:STDOUT:   %impl.elem0.loc43: %.fcc = impl_witness_access constants.%Copy.impl_witness.514, element0 [concrete = constants.%UInt.as.Copy.impl.Op.c10]
-// CHECK:STDOUT:   %bound_method.loc43_10.1: <bound method> = bound_method %.loc43_10.3, %impl.elem0.loc43
-// CHECK:STDOUT:   %specific_fn.loc43: <specific function> = specific_function %impl.elem0.loc43, @UInt.as.Copy.impl.Op(constants.%int_32) [concrete = constants.%UInt.as.Copy.impl.Op.specific_fn]
-// CHECK:STDOUT:   %bound_method.loc43_10.2: <bound method> = bound_method %.loc43_10.3, %specific_fn.loc43
-// CHECK:STDOUT:   %UInt.as.Copy.impl.Op.call.loc43: init %u32 = call %bound_method.loc43_10.2(%.loc43_10.3)
-// CHECK:STDOUT:   %tuple.elem1.loc43_10.2: ref %u32 = tuple_access %return.param, element1
-// CHECK:STDOUT:   %.loc43_10.4: init %u32 to %tuple.elem1.loc43_10.2 = initialize_from %UInt.as.Copy.impl.Op.call.loc43
-// CHECK:STDOUT:   %.loc43_10.5: init %tuple.type.d78 to %return.param = tuple_init (%.loc43_10.2, %.loc43_10.4)
-// CHECK:STDOUT:   %.loc43_11: init %tuple.type.d78 = converted %d.ref, %.loc43_10.5
+// CHECK:STDOUT:   %tuple.elem0.loc43: ref %AdaptCopyable = tuple_access %d.ref, element0
+// CHECK:STDOUT:   %.loc43: %AdaptCopyable = acquire_value %tuple.elem0.loc43
 // CHECK:STDOUT:   %DestroyOp.bound: <bound method> = bound_method %d.var, constants.%DestroyOp.b0ebf8.2
 // CHECK:STDOUT:   %DestroyOp.call: init %empty_tuple.type = call %DestroyOp.bound(%d.var)
-// CHECK:STDOUT:   return %.loc43_11 to %return.param
+// CHECK:STDOUT:   return <error> to %return.param
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: fn @DestroyOp.loc35(%self.param: %tuple.type.d78) = "no_op";
@@ -510,7 +473,7 @@ fn InTuple(c: (AdaptStruct, u32)) -> (AdaptStruct, u32) {
 // CHECK:STDOUT:   %Int.as.Copy.impl.Op.call.loc9_3.1: init %i32 = call %bound_method.loc9_3.2(%tuple.elem0.loc9_3.1)
 // CHECK:STDOUT:   %.loc9_3.2: ref %tuple.type.d07 = as_compatible %d.var
 // CHECK:STDOUT:   %tuple.elem0.loc9_3.2: ref %i32 = tuple_access %.loc9_3.2, element0
-// CHECK:STDOUT:   %.loc9_3.3: init %i32 to %tuple.elem0.loc9_3.2 = initialize_from %Int.as.Copy.impl.Op.call.loc9_3.1
+// CHECK:STDOUT:   %.loc9_3.3: init %i32 to %tuple.elem0.loc9_3.2 = in_place_init %Int.as.Copy.impl.Op.call.loc9_3.1
 // CHECK:STDOUT:   %tuple.elem1.loc9_3.1: %i32 = tuple_access %.loc9_3.1, element1
 // CHECK:STDOUT:   %impl.elem0.loc9_3.2: %.f79 = impl_witness_access constants.%Copy.impl_witness.f17, element0 [concrete = constants.%Int.as.Copy.impl.Op.664]
 // CHECK:STDOUT:   %bound_method.loc9_3.3: <bound method> = bound_method %tuple.elem1.loc9_3.1, %impl.elem0.loc9_3.2
@@ -518,7 +481,7 @@ fn InTuple(c: (AdaptStruct, u32)) -> (AdaptStruct, u32) {
 // CHECK:STDOUT:   %bound_method.loc9_3.4: <bound method> = bound_method %tuple.elem1.loc9_3.1, %specific_fn.loc9_3.2
 // CHECK:STDOUT:   %Int.as.Copy.impl.Op.call.loc9_3.2: init %i32 = call %bound_method.loc9_3.4(%tuple.elem1.loc9_3.1)
 // CHECK:STDOUT:   %tuple.elem1.loc9_3.2: ref %i32 = tuple_access %.loc9_3.2, element1
-// CHECK:STDOUT:   %.loc9_3.4: init %i32 to %tuple.elem1.loc9_3.2 = initialize_from %Int.as.Copy.impl.Op.call.loc9_3.2
+// CHECK:STDOUT:   %.loc9_3.4: init %i32 to %tuple.elem1.loc9_3.2 = in_place_init %Int.as.Copy.impl.Op.call.loc9_3.2
 // CHECK:STDOUT:   %.loc9_3.5: init %tuple.type.d07 to %.loc9_3.2 = tuple_init (%.loc9_3.3, %.loc9_3.4)
 // CHECK:STDOUT:   %.loc9_3.6: init %AdaptTuple = as_compatible %.loc9_3.5
 // CHECK:STDOUT:   %.loc9_3.7: init %AdaptTuple = converted %c.ref, %.loc9_3.6
@@ -536,7 +499,7 @@ fn InTuple(c: (AdaptStruct, u32)) -> (AdaptStruct, u32) {
 // CHECK:STDOUT:   %Int.as.Copy.impl.Op.call.loc10_11.1: init %i32 = call %bound_method.loc10_11.2(%.loc10_11.2)
 // CHECK:STDOUT:   %.loc10_11.3: ref %tuple.type.d07 = as_compatible %return.param
 // CHECK:STDOUT:   %tuple.elem0.loc10_11.2: ref %i32 = tuple_access %.loc10_11.3, element0
-// CHECK:STDOUT:   %.loc10_11.4: init %i32 to %tuple.elem0.loc10_11.2 = initialize_from %Int.as.Copy.impl.Op.call.loc10_11.1
+// CHECK:STDOUT:   %.loc10_11.4: init %i32 to %tuple.elem0.loc10_11.2 = in_place_init %Int.as.Copy.impl.Op.call.loc10_11.1
 // CHECK:STDOUT:   %tuple.elem1.loc10_11.1: ref %i32 = tuple_access %.loc10_11.1, element1
 // CHECK:STDOUT:   %.loc10_11.5: %i32 = acquire_value %tuple.elem1.loc10_11.1
 // CHECK:STDOUT:   %impl.elem0.loc10_11.2: %.f79 = impl_witness_access constants.%Copy.impl_witness.f17, element0 [concrete = constants.%Int.as.Copy.impl.Op.664]
@@ -545,7 +508,7 @@ fn InTuple(c: (AdaptStruct, u32)) -> (AdaptStruct, u32) {
 // CHECK:STDOUT:   %bound_method.loc10_11.4: <bound method> = bound_method %.loc10_11.5, %specific_fn.loc10_11.2
 // CHECK:STDOUT:   %Int.as.Copy.impl.Op.call.loc10_11.2: init %i32 = call %bound_method.loc10_11.4(%.loc10_11.5)
 // CHECK:STDOUT:   %tuple.elem1.loc10_11.2: ref %i32 = tuple_access %.loc10_11.3, element1
-// CHECK:STDOUT:   %.loc10_11.6: init %i32 to %tuple.elem1.loc10_11.2 = initialize_from %Int.as.Copy.impl.Op.call.loc10_11.2
+// CHECK:STDOUT:   %.loc10_11.6: init %i32 to %tuple.elem1.loc10_11.2 = in_place_init %Int.as.Copy.impl.Op.call.loc10_11.2
 // CHECK:STDOUT:   %.loc10_11.7: init %tuple.type.d07 to %.loc10_11.3 = tuple_init (%.loc10_11.4, %.loc10_11.6)
 // CHECK:STDOUT:   %.loc10_11.8: init %AdaptTuple = as_compatible %.loc10_11.7
 // CHECK:STDOUT:   %.loc10_11.9: init %AdaptTuple = converted %d.ref, %.loc10_11.8
@@ -575,7 +538,7 @@ fn InTuple(c: (AdaptStruct, u32)) -> (AdaptStruct, u32) {
 // CHECK:STDOUT:   %tuple.elem0.loc14_30.3: ref %AdaptTuple = tuple_access %d.var, element0
 // CHECK:STDOUT:   %.loc14_30.2: ref %tuple.type.d07 = as_compatible %tuple.elem0.loc14_30.3
 // CHECK:STDOUT:   %tuple.elem0.loc14_30.4: ref %i32 = tuple_access %.loc14_30.2, element0
-// CHECK:STDOUT:   %.loc14_30.3: init %i32 to %tuple.elem0.loc14_30.4 = initialize_from %Int.as.Copy.impl.Op.call.loc14_30.1
+// CHECK:STDOUT:   %.loc14_30.3: init %i32 to %tuple.elem0.loc14_30.4 = in_place_init %Int.as.Copy.impl.Op.call.loc14_30.1
 // CHECK:STDOUT:   %tuple.elem1.loc14_30.1: %i32 = tuple_access %.loc14_30.1, element1
 // CHECK:STDOUT:   %impl.elem0.loc14_30.2: %.f79 = impl_witness_access constants.%Copy.impl_witness.f17, element0 [concrete = constants.%Int.as.Copy.impl.Op.664]
 // CHECK:STDOUT:   %bound_method.loc14_30.3: <bound method> = bound_method %tuple.elem1.loc14_30.1, %impl.elem0.loc14_30.2
@@ -583,7 +546,7 @@ fn InTuple(c: (AdaptStruct, u32)) -> (AdaptStruct, u32) {
 // CHECK:STDOUT:   %bound_method.loc14_30.4: <bound method> = bound_method %tuple.elem1.loc14_30.1, %specific_fn.loc14_30.2
 // CHECK:STDOUT:   %Int.as.Copy.impl.Op.call.loc14_30.2: init %i32 = call %bound_method.loc14_30.4(%tuple.elem1.loc14_30.1)
 // CHECK:STDOUT:   %tuple.elem1.loc14_30.2: ref %i32 = tuple_access %.loc14_30.2, element1
-// CHECK:STDOUT:   %.loc14_30.4: init %i32 to %tuple.elem1.loc14_30.2 = initialize_from %Int.as.Copy.impl.Op.call.loc14_30.2
+// CHECK:STDOUT:   %.loc14_30.4: init %i32 to %tuple.elem1.loc14_30.2 = in_place_init %Int.as.Copy.impl.Op.call.loc14_30.2
 // CHECK:STDOUT:   %.loc14_30.5: init %tuple.type.d07 to %.loc14_30.2 = tuple_init (%.loc14_30.3, %.loc14_30.4)
 // CHECK:STDOUT:   %.loc14_30.6: init %AdaptTuple = as_compatible %.loc14_30.5
 // CHECK:STDOUT:   %.loc14_30.7: init %AdaptTuple = converted %tuple.elem0.loc14_30.1, %.loc14_30.6
@@ -594,7 +557,7 @@ fn InTuple(c: (AdaptStruct, u32)) -> (AdaptStruct, u32) {
 // CHECK:STDOUT:   %bound_method.loc14_30.6: <bound method> = bound_method %tuple.elem1.loc14_30.3, %specific_fn.loc14_30.3
 // CHECK:STDOUT:   %UInt.as.Copy.impl.Op.call.loc14: init %u32 = call %bound_method.loc14_30.6(%tuple.elem1.loc14_30.3)
 // CHECK:STDOUT:   %tuple.elem1.loc14_30.4: ref %u32 = tuple_access %d.var, element1
-// CHECK:STDOUT:   %.loc14_30.8: init %u32 to %tuple.elem1.loc14_30.4 = initialize_from %UInt.as.Copy.impl.Op.call.loc14
+// CHECK:STDOUT:   %.loc14_30.8: init %u32 to %tuple.elem1.loc14_30.4 = in_place_init %UInt.as.Copy.impl.Op.call.loc14
 // CHECK:STDOUT:   %.loc14_30.9: init %tuple.type.3c7 to %d.var = tuple_init (%.loc14_30.7, %.loc14_30.8)
 // CHECK:STDOUT:   %.loc14_3: init %tuple.type.3c7 = converted %c.ref, %.loc14_30.9
 // CHECK:STDOUT:   assign %d.var, %.loc14_3
@@ -619,7 +582,7 @@ fn InTuple(c: (AdaptStruct, u32)) -> (AdaptStruct, u32) {
 // CHECK:STDOUT:   %tuple.elem0.loc15_10.3: ref %AdaptTuple = tuple_access %return.param, element0
 // CHECK:STDOUT:   %.loc15_10.3: ref %tuple.type.d07 = as_compatible %tuple.elem0.loc15_10.3
 // CHECK:STDOUT:   %tuple.elem0.loc15_10.4: ref %i32 = tuple_access %.loc15_10.3, element0
-// CHECK:STDOUT:   %.loc15_10.4: init %i32 to %tuple.elem0.loc15_10.4 = initialize_from %Int.as.Copy.impl.Op.call.loc15_10.1
+// CHECK:STDOUT:   %.loc15_10.4: init %i32 to %tuple.elem0.loc15_10.4 = in_place_init %Int.as.Copy.impl.Op.call.loc15_10.1
 // CHECK:STDOUT:   %tuple.elem1.loc15_10.1: ref %i32 = tuple_access %.loc15_10.1, element1
 // CHECK:STDOUT:   %.loc15_10.5: %i32 = acquire_value %tuple.elem1.loc15_10.1
 // CHECK:STDOUT:   %impl.elem0.loc15_10.2: %.f79 = impl_witness_access constants.%Copy.impl_witness.f17, element0 [concrete = constants.%Int.as.Copy.impl.Op.664]
@@ -628,7 +591,7 @@ fn InTuple(c: (AdaptStruct, u32)) -> (AdaptStruct, u32) {
 // CHECK:STDOUT:   %bound_method.loc15_10.4: <bound method> = bound_method %.loc15_10.5, %specific_fn.loc15_10.2
 // CHECK:STDOUT:   %Int.as.Copy.impl.Op.call.loc15_10.2: init %i32 = call %bound_method.loc15_10.4(%.loc15_10.5)
 // CHECK:STDOUT:   %tuple.elem1.loc15_10.2: ref %i32 = tuple_access %.loc15_10.3, element1
-// CHECK:STDOUT:   %.loc15_10.6: init %i32 to %tuple.elem1.loc15_10.2 = initialize_from %Int.as.Copy.impl.Op.call.loc15_10.2
+// CHECK:STDOUT:   %.loc15_10.6: init %i32 to %tuple.elem1.loc15_10.2 = in_place_init %Int.as.Copy.impl.Op.call.loc15_10.2
 // CHECK:STDOUT:   %.loc15_10.7: init %tuple.type.d07 to %.loc15_10.3 = tuple_init (%.loc15_10.4, %.loc15_10.6)
 // CHECK:STDOUT:   %.loc15_10.8: init %AdaptTuple = as_compatible %.loc15_10.7
 // CHECK:STDOUT:   %.loc15_10.9: init %AdaptTuple = converted %tuple.elem0.loc15_10.1, %.loc15_10.8
@@ -640,7 +603,7 @@ fn InTuple(c: (AdaptStruct, u32)) -> (AdaptStruct, u32) {
 // CHECK:STDOUT:   %bound_method.loc15_10.6: <bound method> = bound_method %.loc15_10.10, %specific_fn.loc15_10.3
 // CHECK:STDOUT:   %UInt.as.Copy.impl.Op.call.loc15: init %u32 = call %bound_method.loc15_10.6(%.loc15_10.10)
 // CHECK:STDOUT:   %tuple.elem1.loc15_10.4: ref %u32 = tuple_access %return.param, element1
-// CHECK:STDOUT:   %.loc15_10.11: init %u32 to %tuple.elem1.loc15_10.4 = initialize_from %UInt.as.Copy.impl.Op.call.loc15
+// CHECK:STDOUT:   %.loc15_10.11: init %u32 to %tuple.elem1.loc15_10.4 = in_place_init %UInt.as.Copy.impl.Op.call.loc15
 // CHECK:STDOUT:   %.loc15_10.12: init %tuple.type.3c7 to %return.param = tuple_init (%.loc15_10.9, %.loc15_10.11)
 // CHECK:STDOUT:   %.loc15_11: init %tuple.type.3c7 = converted %d.ref, %.loc15_10.12
 // CHECK:STDOUT:   %DestroyOp.bound: <bound method> = bound_method %d.var, constants.%DestroyOp.b0ebf8.2
@@ -863,7 +826,7 @@ fn InTuple(c: (AdaptStruct, u32)) -> (AdaptStruct, u32) {
 // CHECK:STDOUT:   %Int.as.Copy.impl.Op.call.loc23: init %i32 = call %bound_method.loc23_3.2(%tuple.elem0.loc23_3.1)
 // CHECK:STDOUT:   %.loc23_3.2: ref %tuple.type.7f9 = as_compatible %b.var
 // CHECK:STDOUT:   %tuple.elem0.loc23_3.2: ref %i32 = tuple_access %.loc23_3.2, element0
-// CHECK:STDOUT:   %.loc23_3.3: init %i32 to %tuple.elem0.loc23_3.2 = initialize_from %Int.as.Copy.impl.Op.call.loc23
+// CHECK:STDOUT:   %.loc23_3.3: init %i32 to %tuple.elem0.loc23_3.2 = in_place_init %Int.as.Copy.impl.Op.call.loc23
 // CHECK:STDOUT:   %tuple.elem1.loc23: %Noncopyable = tuple_access %.loc23_3.1, element1
 // CHECK:STDOUT:   assign %b.var, <error>
 // CHECK:STDOUT:   %AdaptNoncopyableIndirect.ref.loc23: type = name_ref AdaptNoncopyableIndirect, file.%AdaptNoncopyableIndirect.decl [concrete = constants.%AdaptNoncopyableIndirect]
@@ -879,7 +842,7 @@ fn InTuple(c: (AdaptStruct, u32)) -> (AdaptStruct, u32) {
 // CHECK:STDOUT:   %Int.as.Copy.impl.Op.call.loc34: init %i32 = call %bound_method.loc34_11.2(%.loc34_11.2)
 // CHECK:STDOUT:   %.loc34_11.3: ref %tuple.type.7f9 = as_compatible %return.param
 // CHECK:STDOUT:   %tuple.elem0.loc34_11.2: ref %i32 = tuple_access %.loc34_11.3, element0
-// CHECK:STDOUT:   %.loc34_11.4: init %i32 to %tuple.elem0.loc34_11.2 = initialize_from %Int.as.Copy.impl.Op.call.loc34
+// CHECK:STDOUT:   %.loc34_11.4: init %i32 to %tuple.elem0.loc34_11.2 = in_place_init %Int.as.Copy.impl.Op.call.loc34
 // CHECK:STDOUT:   %tuple.elem1.loc34: ref %Noncopyable = tuple_access %.loc34_11.1, element1
 // CHECK:STDOUT:   %.loc34_11.5: %Noncopyable = acquire_value %tuple.elem1.loc34
 // CHECK:STDOUT:   %DestroyOp.bound: <bound method> = bound_method %b.var, constants.%DestroyOp
@@ -1039,7 +1002,7 @@ fn InTuple(c: (AdaptStruct, u32)) -> (AdaptStruct, u32) {
 // CHECK:STDOUT:   %Int.as.Copy.impl.Op.call.loc9_3.1: init %i32 = call %bound_method.loc9_3.2(%.loc9_3.2)
 // CHECK:STDOUT:   %.loc9_3.3: ref %struct_type.e.f = as_compatible %h.var
 // CHECK:STDOUT:   %.loc9_3.4: ref %i32 = struct_access %.loc9_3.3, element0
-// CHECK:STDOUT:   %.loc9_3.5: init %i32 to %.loc9_3.4 = initialize_from %Int.as.Copy.impl.Op.call.loc9_3.1
+// CHECK:STDOUT:   %.loc9_3.5: init %i32 to %.loc9_3.4 = in_place_init %Int.as.Copy.impl.Op.call.loc9_3.1
 // CHECK:STDOUT:   %.loc9_3.6: %i32 = struct_access %.loc9_3.1, element1
 // CHECK:STDOUT:   %impl.elem0.loc9_3.2: %.f79 = impl_witness_access constants.%Copy.impl_witness.f17, element0 [concrete = constants.%Int.as.Copy.impl.Op.664]
 // CHECK:STDOUT:   %bound_method.loc9_3.3: <bound method> = bound_method %.loc9_3.6, %impl.elem0.loc9_3.2
@@ -1047,7 +1010,7 @@ fn InTuple(c: (AdaptStruct, u32)) -> (AdaptStruct, u32) {
 // CHECK:STDOUT:   %bound_method.loc9_3.4: <bound method> = bound_method %.loc9_3.6, %specific_fn.loc9_3.2
 // CHECK:STDOUT:   %Int.as.Copy.impl.Op.call.loc9_3.2: init %i32 = call %bound_method.loc9_3.4(%.loc9_3.6)
 // CHECK:STDOUT:   %.loc9_3.7: ref %i32 = struct_access %.loc9_3.3, element1
-// CHECK:STDOUT:   %.loc9_3.8: init %i32 to %.loc9_3.7 = initialize_from %Int.as.Copy.impl.Op.call.loc9_3.2
+// CHECK:STDOUT:   %.loc9_3.8: init %i32 to %.loc9_3.7 = in_place_init %Int.as.Copy.impl.Op.call.loc9_3.2
 // CHECK:STDOUT:   %.loc9_3.9: init %struct_type.e.f to %.loc9_3.3 = struct_init (%.loc9_3.5, %.loc9_3.8)
 // CHECK:STDOUT:   %.loc9_3.10: init %AdaptStruct = as_compatible %.loc9_3.9
 // CHECK:STDOUT:   %.loc9_3.11: init %AdaptStruct = converted %g.ref, %.loc9_3.10
@@ -1065,7 +1028,7 @@ fn InTuple(c: (AdaptStruct, u32)) -> (AdaptStruct, u32) {
 // CHECK:STDOUT:   %Int.as.Copy.impl.Op.call.loc10_11.1: init %i32 = call %bound_method.loc10_11.2(%.loc10_11.3)
 // CHECK:STDOUT:   %.loc10_11.4: ref %struct_type.e.f = as_compatible %return.param
 // CHECK:STDOUT:   %.loc10_11.5: ref %i32 = struct_access %.loc10_11.4, element0
-// CHECK:STDOUT:   %.loc10_11.6: init %i32 to %.loc10_11.5 = initialize_from %Int.as.Copy.impl.Op.call.loc10_11.1
+// CHECK:STDOUT:   %.loc10_11.6: init %i32 to %.loc10_11.5 = in_place_init %Int.as.Copy.impl.Op.call.loc10_11.1
 // CHECK:STDOUT:   %.loc10_11.7: ref %i32 = struct_access %.loc10_11.1, element1
 // CHECK:STDOUT:   %.loc10_11.8: %i32 = acquire_value %.loc10_11.7
 // CHECK:STDOUT:   %impl.elem0.loc10_11.2: %.f79 = impl_witness_access constants.%Copy.impl_witness.f17, element0 [concrete = constants.%Int.as.Copy.impl.Op.664]
@@ -1074,7 +1037,7 @@ fn InTuple(c: (AdaptStruct, u32)) -> (AdaptStruct, u32) {
 // CHECK:STDOUT:   %bound_method.loc10_11.4: <bound method> = bound_method %.loc10_11.8, %specific_fn.loc10_11.2
 // CHECK:STDOUT:   %Int.as.Copy.impl.Op.call.loc10_11.2: init %i32 = call %bound_method.loc10_11.4(%.loc10_11.8)
 // CHECK:STDOUT:   %.loc10_11.9: ref %i32 = struct_access %.loc10_11.4, element1
-// CHECK:STDOUT:   %.loc10_11.10: init %i32 to %.loc10_11.9 = initialize_from %Int.as.Copy.impl.Op.call.loc10_11.2
+// CHECK:STDOUT:   %.loc10_11.10: init %i32 to %.loc10_11.9 = in_place_init %Int.as.Copy.impl.Op.call.loc10_11.2
 // CHECK:STDOUT:   %.loc10_11.11: init %struct_type.e.f to %.loc10_11.4 = struct_init (%.loc10_11.6, %.loc10_11.10)
 // CHECK:STDOUT:   %.loc10_11.12: init %AdaptStruct = as_compatible %.loc10_11.11
 // CHECK:STDOUT:   %.loc10_11.13: init %AdaptStruct = converted %h.ref, %.loc10_11.12
@@ -1104,7 +1067,7 @@ fn InTuple(c: (AdaptStruct, u32)) -> (AdaptStruct, u32) {
 // CHECK:STDOUT:   %tuple.elem0.loc14_31.2: ref %AdaptStruct = tuple_access %d.var, element0
 // CHECK:STDOUT:   %.loc14_31.3: ref %struct_type.e.f = as_compatible %tuple.elem0.loc14_31.2
 // CHECK:STDOUT:   %.loc14_31.4: ref %i32 = struct_access %.loc14_31.3, element0
-// CHECK:STDOUT:   %.loc14_31.5: init %i32 to %.loc14_31.4 = initialize_from %Int.as.Copy.impl.Op.call.loc14_31.1
+// CHECK:STDOUT:   %.loc14_31.5: init %i32 to %.loc14_31.4 = in_place_init %Int.as.Copy.impl.Op.call.loc14_31.1
 // CHECK:STDOUT:   %.loc14_31.6: %i32 = struct_access %.loc14_31.1, element1
 // CHECK:STDOUT:   %impl.elem0.loc14_31.2: %.f79 = impl_witness_access constants.%Copy.impl_witness.f17, element0 [concrete = constants.%Int.as.Copy.impl.Op.664]
 // CHECK:STDOUT:   %bound_method.loc14_31.3: <bound method> = bound_method %.loc14_31.6, %impl.elem0.loc14_31.2
@@ -1112,7 +1075,7 @@ fn InTuple(c: (AdaptStruct, u32)) -> (AdaptStruct, u32) {
 // CHECK:STDOUT:   %bound_method.loc14_31.4: <bound method> = bound_method %.loc14_31.6, %specific_fn.loc14_31.2
 // CHECK:STDOUT:   %Int.as.Copy.impl.Op.call.loc14_31.2: init %i32 = call %bound_method.loc14_31.4(%.loc14_31.6)
 // CHECK:STDOUT:   %.loc14_31.7: ref %i32 = struct_access %.loc14_31.3, element1
-// CHECK:STDOUT:   %.loc14_31.8: init %i32 to %.loc14_31.7 = initialize_from %Int.as.Copy.impl.Op.call.loc14_31.2
+// CHECK:STDOUT:   %.loc14_31.8: init %i32 to %.loc14_31.7 = in_place_init %Int.as.Copy.impl.Op.call.loc14_31.2
 // CHECK:STDOUT:   %.loc14_31.9: init %struct_type.e.f to %.loc14_31.3 = struct_init (%.loc14_31.5, %.loc14_31.8)
 // CHECK:STDOUT:   %.loc14_31.10: init %AdaptStruct = as_compatible %.loc14_31.9
 // CHECK:STDOUT:   %.loc14_31.11: init %AdaptStruct = converted %tuple.elem0.loc14_31.1, %.loc14_31.10
@@ -1123,7 +1086,7 @@ fn InTuple(c: (AdaptStruct, u32)) -> (AdaptStruct, u32) {
 // CHECK:STDOUT:   %bound_method.loc14_31.6: <bound method> = bound_method %tuple.elem1.loc14_31.1, %specific_fn.loc14_31.3
 // CHECK:STDOUT:   %UInt.as.Copy.impl.Op.call.loc14: init %u32 = call %bound_method.loc14_31.6(%tuple.elem1.loc14_31.1)
 // CHECK:STDOUT:   %tuple.elem1.loc14_31.2: ref %u32 = tuple_access %d.var, element1
-// CHECK:STDOUT:   %.loc14_31.12: init %u32 to %tuple.elem1.loc14_31.2 = initialize_from %UInt.as.Copy.impl.Op.call.loc14
+// CHECK:STDOUT:   %.loc14_31.12: init %u32 to %tuple.elem1.loc14_31.2 = in_place_init %UInt.as.Copy.impl.Op.call.loc14
 // CHECK:STDOUT:   %.loc14_31.13: init %tuple.type.691 to %d.var = tuple_init (%.loc14_31.11, %.loc14_31.12)
 // CHECK:STDOUT:   %.loc14_3: init %tuple.type.691 = converted %c.ref, %.loc14_31.13
 // CHECK:STDOUT:   assign %d.var, %.loc14_3
@@ -1148,7 +1111,7 @@ fn InTuple(c: (AdaptStruct, u32)) -> (AdaptStruct, u32) {
 // CHECK:STDOUT:   %tuple.elem0.loc15_10.2: ref %AdaptStruct = tuple_access %return.param, element0
 // CHECK:STDOUT:   %.loc15_10.4: ref %struct_type.e.f = as_compatible %tuple.elem0.loc15_10.2
 // CHECK:STDOUT:   %.loc15_10.5: ref %i32 = struct_access %.loc15_10.4, element0
-// CHECK:STDOUT:   %.loc15_10.6: init %i32 to %.loc15_10.5 = initialize_from %Int.as.Copy.impl.Op.call.loc15_10.1
+// CHECK:STDOUT:   %.loc15_10.6: init %i32 to %.loc15_10.5 = in_place_init %Int.as.Copy.impl.Op.call.loc15_10.1
 // CHECK:STDOUT:   %.loc15_10.7: ref %i32 = struct_access %.loc15_10.1, element1
 // CHECK:STDOUT:   %.loc15_10.8: %i32 = acquire_value %.loc15_10.7
 // CHECK:STDOUT:   %impl.elem0.loc15_10.2: %.f79 = impl_witness_access constants.%Copy.impl_witness.f17, element0 [concrete = constants.%Int.as.Copy.impl.Op.664]
@@ -1157,7 +1120,7 @@ fn InTuple(c: (AdaptStruct, u32)) -> (AdaptStruct, u32) {
 // CHECK:STDOUT:   %bound_method.loc15_10.4: <bound method> = bound_method %.loc15_10.8, %specific_fn.loc15_10.2
 // CHECK:STDOUT:   %Int.as.Copy.impl.Op.call.loc15_10.2: init %i32 = call %bound_method.loc15_10.4(%.loc15_10.8)
 // CHECK:STDOUT:   %.loc15_10.9: ref %i32 = struct_access %.loc15_10.4, element1
-// CHECK:STDOUT:   %.loc15_10.10: init %i32 to %.loc15_10.9 = initialize_from %Int.as.Copy.impl.Op.call.loc15_10.2
+// CHECK:STDOUT:   %.loc15_10.10: init %i32 to %.loc15_10.9 = in_place_init %Int.as.Copy.impl.Op.call.loc15_10.2
 // CHECK:STDOUT:   %.loc15_10.11: init %struct_type.e.f to %.loc15_10.4 = struct_init (%.loc15_10.6, %.loc15_10.10)
 // CHECK:STDOUT:   %.loc15_10.12: init %AdaptStruct = as_compatible %.loc15_10.11
 // CHECK:STDOUT:   %.loc15_10.13: init %AdaptStruct = converted %tuple.elem0.loc15_10.1, %.loc15_10.12
@@ -1169,7 +1132,7 @@ fn InTuple(c: (AdaptStruct, u32)) -> (AdaptStruct, u32) {
 // CHECK:STDOUT:   %bound_method.loc15_10.6: <bound method> = bound_method %.loc15_10.14, %specific_fn.loc15_10.3
 // CHECK:STDOUT:   %UInt.as.Copy.impl.Op.call.loc15: init %u32 = call %bound_method.loc15_10.6(%.loc15_10.14)
 // CHECK:STDOUT:   %tuple.elem1.loc15_10.2: ref %u32 = tuple_access %return.param, element1
-// CHECK:STDOUT:   %.loc15_10.15: init %u32 to %tuple.elem1.loc15_10.2 = initialize_from %UInt.as.Copy.impl.Op.call.loc15
+// CHECK:STDOUT:   %.loc15_10.15: init %u32 to %tuple.elem1.loc15_10.2 = in_place_init %UInt.as.Copy.impl.Op.call.loc15
 // CHECK:STDOUT:   %.loc15_10.16: init %tuple.type.691 to %return.param = tuple_init (%.loc15_10.13, %.loc15_10.15)
 // CHECK:STDOUT:   %.loc15_11: init %tuple.type.691 = converted %d.ref, %.loc15_10.16
 // CHECK:STDOUT:   %DestroyOp.bound: <bound method> = bound_method %d.var, constants.%DestroyOp.b0ebf8.2
diff --git a/toolchain/check/testdata/class/adapter/init_adapt.carbon b/toolchain/check/testdata/class/adapter/init_adapt.carbon
index 043138050d18..5a21044cdab9 100644
--- a/toolchain/check/testdata/class/adapter/init_adapt.carbon
+++ b/toolchain/check/testdata/class/adapter/init_adapt.carbon
@@ -183,7 +183,7 @@ var e: C = MakeAdaptC();
 // CHECK:STDOUT:   %.loc13_27.1: init %i32 = converted @__global_init.%int_1, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc13_27.1 [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %.loc13_27.2: ref %C = temporary_storage
 // CHECK:STDOUT:   %.loc13_27.3: ref %i32 = class_element_access %.loc13_27.2, element0
-// CHECK:STDOUT:   %.loc13_27.4: init %i32 to %.loc13_27.3 = initialize_from %.loc13_27.1 [concrete = constants.%int_1.5d2]
+// CHECK:STDOUT:   %.loc13_27.4: init %i32 to %.loc13_27.3 = in_place_init %.loc13_27.1 [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %impl.elem0.loc13_27.2: %.863 = impl_witness_access constants.%ImplicitAs.impl_witness.6bc, element0 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.0b5]
 // CHECK:STDOUT:   %bound_method.loc13_27.3: <bound method> = bound_method @__global_init.%int_2, %impl.elem0.loc13_27.2 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.bound.4e5]
 // CHECK:STDOUT:   %specific_fn.loc13_27.2: <specific function> = specific_function %impl.elem0.loc13_27.2, @Core.IntLiteral.as.ImplicitAs.impl.Convert(constants.%int_32) [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.specific_fn]
@@ -191,7 +191,7 @@ var e: C = MakeAdaptC();
 // CHECK:STDOUT:   %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc13_27.2: init %i32 = call %bound_method.loc13_27.4(@__global_init.%int_2) [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %.loc13_27.5: init %i32 = converted @__global_init.%int_2, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc13_27.2 [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %.loc13_27.6: ref %i32 = class_element_access %.loc13_27.2, element1
-// CHECK:STDOUT:   %.loc13_27.7: init %i32 to %.loc13_27.6 = initialize_from %.loc13_27.5 [concrete = constants.%int_2.ef8]
+// CHECK:STDOUT:   %.loc13_27.7: init %i32 to %.loc13_27.6 = in_place_init %.loc13_27.5 [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %.loc13_27.8: init %C to %.loc13_27.2 = class_init (%.loc13_27.4, %.loc13_27.7) [concrete = constants.%C.val]
 // CHECK:STDOUT:   %.loc13_27.9: ref %C = temporary %.loc13_27.2, %.loc13_27.8
 // CHECK:STDOUT:   %.loc13_27.10: ref %C = converted @__global_init.%.loc13, %.loc13_27.9
@@ -389,7 +389,7 @@ var e: C = MakeAdaptC();
 // CHECK:STDOUT:   %.loc13_27.1: init %i32 = converted @__global_init.%int_1, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc13_27.1 [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %.loc13_27.2: ref %C = temporary_storage
 // CHECK:STDOUT:   %.loc13_27.3: ref %i32 = class_element_access %.loc13_27.2, element0
-// CHECK:STDOUT:   %.loc13_27.4: init %i32 to %.loc13_27.3 = initialize_from %.loc13_27.1 [concrete = constants.%int_1.5d2]
+// CHECK:STDOUT:   %.loc13_27.4: init %i32 to %.loc13_27.3 = in_place_init %.loc13_27.1 [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %impl.elem0.loc13_27.2: %.863 = impl_witness_access constants.%ImplicitAs.impl_witness.6bc, element0 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.0b5]
 // CHECK:STDOUT:   %bound_method.loc13_27.3: <bound method> = bound_method @__global_init.%int_2, %impl.elem0.loc13_27.2 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.bound.4e5]
 // CHECK:STDOUT:   %specific_fn.loc13_27.2: <specific function> = specific_function %impl.elem0.loc13_27.2, @Core.IntLiteral.as.ImplicitAs.impl.Convert(constants.%int_32) [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.specific_fn]
@@ -397,7 +397,7 @@ var e: C = MakeAdaptC();
 // CHECK:STDOUT:   %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc13_27.2: init %i32 = call %bound_method.loc13_27.4(@__global_init.%int_2) [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %.loc13_27.5: init %i32 = converted @__global_init.%int_2, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc13_27.2 [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %.loc13_27.6: ref %i32 = class_element_access %.loc13_27.2, element1
-// CHECK:STDOUT:   %.loc13_27.7: init %i32 to %.loc13_27.6 = initialize_from %.loc13_27.5 [concrete = constants.%int_2.ef8]
+// CHECK:STDOUT:   %.loc13_27.7: init %i32 to %.loc13_27.6 = in_place_init %.loc13_27.5 [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %.loc13_27.8: init %C to %.loc13_27.2 = class_init (%.loc13_27.4, %.loc13_27.7) [concrete = constants.%C.val]
 // CHECK:STDOUT:   %.loc13_27.9: ref %C = temporary %.loc13_27.2, %.loc13_27.8
 // CHECK:STDOUT:   %.loc13_27.10: ref %C = converted @__global_init.%.loc13, %.loc13_27.9
diff --git a/toolchain/check/testdata/class/base.carbon b/toolchain/check/testdata/class/base.carbon
index c409310bb027..f30cf3d6ff0f 100644
--- a/toolchain/check/testdata/class/base.carbon
+++ b/toolchain/check/testdata/class/base.carbon
@@ -217,7 +217,7 @@ class Derived {
 // CHECK:STDOUT:   %.loc14_26.2: init %i32 = converted %int_4, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc14_26 [concrete = constants.%int_4.940]
 // CHECK:STDOUT:   %.loc14_35.2: ref %Base = class_element_access %return.param, element0
 // CHECK:STDOUT:   %.loc14_26.3: ref %i32 = class_element_access %.loc14_35.2, element0
-// CHECK:STDOUT:   %.loc14_26.4: init %i32 to %.loc14_26.3 = initialize_from %.loc14_26.2 [concrete = constants.%int_4.940]
+// CHECK:STDOUT:   %.loc14_26.4: init %i32 to %.loc14_26.3 = in_place_init %.loc14_26.2 [concrete = constants.%int_4.940]
 // CHECK:STDOUT:   %.loc14_26.5: init %Base to %.loc14_35.2 = class_init (%.loc14_26.4) [concrete = constants.%Base.val]
 // CHECK:STDOUT:   %.loc14_35.3: init %Base = converted %.loc14_26.1, %.loc14_26.5 [concrete = constants.%Base.val]
 // CHECK:STDOUT:   %impl.elem0.loc14_35: %.863 = impl_witness_access constants.%ImplicitAs.impl_witness.6bc, element0 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.0b5]
@@ -227,7 +227,7 @@ class Derived {
 // CHECK:STDOUT:   %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc14_35: init %i32 = call %bound_method.loc14_35.2(%int_7) [concrete = constants.%int_7.0b1]
 // CHECK:STDOUT:   %.loc14_35.4: init %i32 = converted %int_7, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc14_35 [concrete = constants.%int_7.0b1]
 // CHECK:STDOUT:   %.loc14_35.5: ref %i32 = class_element_access %return.param, element1
-// CHECK:STDOUT:   %.loc14_35.6: init %i32 to %.loc14_35.5 = initialize_from %.loc14_35.4 [concrete = constants.%int_7.0b1]
+// CHECK:STDOUT:   %.loc14_35.6: init %i32 to %.loc14_35.5 = in_place_init %.loc14_35.4 [concrete = constants.%int_7.0b1]
 // CHECK:STDOUT:   %.loc14_35.7: init %Derived to %return.param = class_init (%.loc14_35.3, %.loc14_35.6) [concrete = constants.%Derived.val]
 // CHECK:STDOUT:   %.loc14_36: init %Derived = converted %.loc14_35.1, %.loc14_35.7 [concrete = constants.%Derived.val]
 // CHECK:STDOUT:   return %.loc14_36 to %return.param
@@ -253,14 +253,14 @@ class Derived {
 // CHECK:STDOUT:   %bound_method.loc18_12.2: <bound method> = bound_method %.loc18_12.2, %specific_fn.loc18_12
 // CHECK:STDOUT:   %Int.as.Copy.impl.Op.call.loc18_12: init %i32 = call %bound_method.loc18_12.2(%.loc18_12.2)
 // CHECK:STDOUT:   %tuple.elem0: ref %i32 = tuple_access %return.param, element0
-// CHECK:STDOUT:   %.loc18_24.2: init %i32 to %tuple.elem0 = initialize_from %Int.as.Copy.impl.Op.call.loc18_12
+// CHECK:STDOUT:   %.loc18_24.2: init %i32 to %tuple.elem0 = in_place_init %Int.as.Copy.impl.Op.call.loc18_12
 // CHECK:STDOUT:   %impl.elem0.loc18_22: %.f79 = impl_witness_access constants.%Copy.impl_witness.f17, element0 [concrete = constants.%Int.as.Copy.impl.Op.664]
 // CHECK:STDOUT:   %bound_method.loc18_22.1: <bound method> = bound_method %.loc18_22.2, %impl.elem0.loc18_22
 // CHECK:STDOUT:   %specific_fn.loc18_22: <specific function> = specific_function %impl.elem0.loc18_22, @Int.as.Copy.impl.Op(constants.%int_32) [concrete = constants.%Int.as.Copy.impl.Op.specific_fn]
 // CHECK:STDOUT:   %bound_method.loc18_22.2: <bound method> = bound_method %.loc18_22.2, %specific_fn.loc18_22
 // CHECK:STDOUT:   %Int.as.Copy.impl.Op.call.loc18_22: init %i32 = call %bound_method.loc18_22.2(%.loc18_22.2)
 // CHECK:STDOUT:   %tuple.elem1: ref %i32 = tuple_access %return.param, element1
-// CHECK:STDOUT:   %.loc18_24.3: init %i32 to %tuple.elem1 = initialize_from %Int.as.Copy.impl.Op.call.loc18_22
+// CHECK:STDOUT:   %.loc18_24.3: init %i32 to %tuple.elem1 = in_place_init %Int.as.Copy.impl.Op.call.loc18_22
 // CHECK:STDOUT:   %.loc18_24.4: init %tuple.type.d07 to %return.param = tuple_init (%.loc18_24.2, %.loc18_24.3)
 // CHECK:STDOUT:   %.loc18_25: init %tuple.type.d07 = converted %.loc18_24.1, %.loc18_24.4
 // CHECK:STDOUT:   return %.loc18_25 to %return.param
diff --git a/toolchain/check/testdata/class/derived_to_base.carbon b/toolchain/check/testdata/class/derived_to_base.carbon
index 06ebca0cfc99..9c3a04aee04b 100644
--- a/toolchain/check/testdata/class/derived_to_base.carbon
+++ b/toolchain/check/testdata/class/derived_to_base.carbon
@@ -391,7 +391,7 @@ fn PassConstB(p: const B) {
 // CHECK:STDOUT:   %.loc32_57.3: ref %B = class_element_access %.loc32_57.2, element0
 // CHECK:STDOUT:   %.loc32_48.2: ref %A = class_element_access %.loc32_57.3, element0
 // CHECK:STDOUT:   %.loc32_39.3: ref %i32 = class_element_access %.loc32_48.2, element0
-// CHECK:STDOUT:   %.loc32_39.4: init %i32 to %.loc32_39.3 = initialize_from %.loc32_39.2 [concrete = constants.%int_1.5d2]
+// CHECK:STDOUT:   %.loc32_39.4: init %i32 to %.loc32_39.3 = in_place_init %.loc32_39.2 [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %.loc32_39.5: init %A to %.loc32_48.2 = class_init (%.loc32_39.4) [concrete = constants.%A.val]
 // CHECK:STDOUT:   %.loc32_48.3: init %A = converted %.loc32_39.1, %.loc32_39.5 [concrete = constants.%A.val]
 // CHECK:STDOUT:   %impl.elem0.loc32_48: %.863 = impl_witness_access constants.%ImplicitAs.impl_witness.6bc, element0 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.0b5]
@@ -401,7 +401,7 @@ fn PassConstB(p: const B) {
 // CHECK:STDOUT:   %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc32_48: init %i32 = call %bound_method.loc32_48.2(%int_2) [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %.loc32_48.4: init %i32 = converted %int_2, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc32_48 [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %.loc32_48.5: ref %i32 = class_element_access %.loc32_57.3, element1
-// CHECK:STDOUT:   %.loc32_48.6: init %i32 to %.loc32_48.5 = initialize_from %.loc32_48.4 [concrete = constants.%int_2.ef8]
+// CHECK:STDOUT:   %.loc32_48.6: init %i32 to %.loc32_48.5 = in_place_init %.loc32_48.4 [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %.loc32_48.7: init %B to %.loc32_57.3 = class_init (%.loc32_48.3, %.loc32_48.6) [concrete = constants.%B.val]
 // CHECK:STDOUT:   %.loc32_57.4: init %B = converted %.loc32_48.1, %.loc32_48.7 [concrete = constants.%B.val]
 // CHECK:STDOUT:   %impl.elem0.loc32_57: %.863 = impl_witness_access constants.%ImplicitAs.impl_witness.6bc, element0 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.0b5]
@@ -411,7 +411,7 @@ fn PassConstB(p: const B) {
 // CHECK:STDOUT:   %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc32_57: init %i32 = call %bound_method.loc32_57.2(%int_3) [concrete = constants.%int_3.822]
 // CHECK:STDOUT:   %.loc32_57.5: init %i32 = converted %int_3, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc32_57 [concrete = constants.%int_3.822]
 // CHECK:STDOUT:   %.loc32_57.6: ref %i32 = class_element_access %.loc32_57.2, element1
-// CHECK:STDOUT:   %.loc32_57.7: init %i32 to %.loc32_57.6 = initialize_from %.loc32_57.5 [concrete = constants.%int_3.822]
+// CHECK:STDOUT:   %.loc32_57.7: init %i32 to %.loc32_57.6 = in_place_init %.loc32_57.5 [concrete = constants.%int_3.822]
 // CHECK:STDOUT:   %.loc32_57.8: init %C to %.loc32_57.2 = class_init (%.loc32_57.4, %.loc32_57.7) [concrete = constants.%C.val]
 // CHECK:STDOUT:   %.loc32_57.9: ref %C = temporary %.loc32_57.2, %.loc32_57.8
 // CHECK:STDOUT:   %.loc32_59.1: ref %C = converted %.loc32_57.1, %.loc32_57.9
diff --git a/toolchain/check/testdata/class/generic/import.carbon b/toolchain/check/testdata/class/generic/import.carbon
index e174d6b18f30..31a5215a6097 100644
--- a/toolchain/check/testdata/class/generic/import.carbon
+++ b/toolchain/check/testdata/class/generic/import.carbon
@@ -426,7 +426,7 @@ class Class(U:! type) {
 // CHECK:STDOUT:   %Core.IntLiteral.as.ImplicitAs.impl.Convert.call: init %i32 = call %bound_method.loc9_17.2(%int_1) [concrete = constants.%int_1.47b]
 // CHECK:STDOUT:   %.loc9_17.2: init %i32 = converted %int_1, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call [concrete = constants.%int_1.47b]
 // CHECK:STDOUT:   %.loc9_17.3: ref %i32 = class_element_access %return.param, element0
-// CHECK:STDOUT:   %.loc9_17.4: init %i32 to %.loc9_17.3 = initialize_from %.loc9_17.2 [concrete = constants.%int_1.47b]
+// CHECK:STDOUT:   %.loc9_17.4: init %i32 to %.loc9_17.3 = in_place_init %.loc9_17.2 [concrete = constants.%int_1.47b]
 // CHECK:STDOUT:   %.loc9_17.5: init %CompleteClass.667 to %return.param = class_init (%.loc9_17.4) [concrete = constants.%CompleteClass.val]
 // CHECK:STDOUT:   %.loc9_18: init %CompleteClass.667 = converted %.loc9_17.1, %.loc9_17.5 [concrete = constants.%CompleteClass.val]
 // CHECK:STDOUT:   return %.loc9_18 to %return.param
diff --git a/toolchain/check/testdata/class/generic/init.carbon b/toolchain/check/testdata/class/generic/init.carbon
index f6257992c7c5..0834a83518f5 100644
--- a/toolchain/check/testdata/class/generic/init.carbon
+++ b/toolchain/check/testdata/class/generic/init.carbon
@@ -203,7 +203,7 @@ fn InitFromAdaptedSpecific(x: i32) -> i32 {
 // CHECK:STDOUT:     %bound_method.loc10_27.2: <bound method> = bound_method %x.ref, %specific_impl_fn.loc10_27.1
 // CHECK:STDOUT:     %.loc10_28.2: ref @InitFromStructGeneric.%T.binding.as_type (%T.binding.as_type) = class_element_access %v.var, element0
 // CHECK:STDOUT:     %Copy.Op.call.loc10: init @InitFromStructGeneric.%T.binding.as_type (%T.binding.as_type) to %.loc10_28.2 = call %bound_method.loc10_27.2(%x.ref)
-// CHECK:STDOUT:     %.loc10_28.3: init @InitFromStructGeneric.%T.binding.as_type (%T.binding.as_type) to %.loc10_28.2 = initialize_from %Copy.Op.call.loc10
+// CHECK:STDOUT:     %.loc10_28.3: init @InitFromStructGeneric.%T.binding.as_type (%T.binding.as_type) to %.loc10_28.2 = in_place_init %Copy.Op.call.loc10
 // CHECK:STDOUT:     %.loc10_28.4: init @InitFromStructGeneric.%Class.loc10_17.2 (%Class.316) to %v.var = class_init (%.loc10_28.3)
 // CHECK:STDOUT:     %.loc10_3.1: init @InitFromStructGeneric.%Class.loc10_17.2 (%Class.316) = converted %.loc10_28.1, %.loc10_28.4
 // CHECK:STDOUT:     assign %v.var, %.loc10_3.1
@@ -248,7 +248,7 @@ fn InitFromAdaptedSpecific(x: i32) -> i32 {
 // CHECK:STDOUT:   %bound_method.loc15_29.2: <bound method> = bound_method %x.ref, %specific_fn.loc15
 // CHECK:STDOUT:   %Int.as.Copy.impl.Op.call.loc15: init %i32 = call %bound_method.loc15_29.2(%x.ref)
 // CHECK:STDOUT:   %.loc15_30.2: ref %i32 = class_element_access %v.var, element0
-// CHECK:STDOUT:   %.loc15_30.3: init %i32 to %.loc15_30.2 = initialize_from %Int.as.Copy.impl.Op.call.loc15
+// CHECK:STDOUT:   %.loc15_30.3: init %i32 to %.loc15_30.2 = in_place_init %Int.as.Copy.impl.Op.call.loc15
 // CHECK:STDOUT:   %.loc15_30.4: init %Class.805 to %v.var = class_init (%.loc15_30.3)
 // CHECK:STDOUT:   %.loc15_3: init %Class.805 = converted %.loc15_30.1, %.loc15_30.4
 // CHECK:STDOUT:   assign %v.var, %.loc15_3
diff --git a/toolchain/check/testdata/class/generic/member_type.carbon b/toolchain/check/testdata/class/generic/member_type.carbon
index c28d6c66cc9e..56493a6891e3 100644
--- a/toolchain/check/testdata/class/generic/member_type.carbon
+++ b/toolchain/check/testdata/class/generic/member_type.carbon
@@ -282,7 +282,7 @@ fn Test() -> i32 {
 // CHECK:STDOUT:     %bound_method.loc9_38.2: <bound method> = bound_method %n.ref, %specific_impl_fn.loc9_38.1
 // CHECK:STDOUT:     %.loc9_39.2: ref @Outer.F.%T.binding.as_type (%T.binding.as_type) = class_element_access %return.param, element0
 // CHECK:STDOUT:     %Copy.Op.call: init @Outer.F.%T.binding.as_type (%T.binding.as_type) to %.loc9_39.2 = call %bound_method.loc9_38.2(%n.ref)
-// CHECK:STDOUT:     %.loc9_39.3: init @Outer.F.%T.binding.as_type (%T.binding.as_type) to %.loc9_39.2 = initialize_from %Copy.Op.call
+// CHECK:STDOUT:     %.loc9_39.3: init @Outer.F.%T.binding.as_type (%T.binding.as_type) to %.loc9_39.2 = in_place_init %Copy.Op.call
 // CHECK:STDOUT:     %.loc9_39.4: init @Outer.F.%Inner (%Inner.bcf) to %return.param = class_init (%.loc9_39.3)
 // CHECK:STDOUT:     %.loc9_40: init @Outer.F.%Inner (%Inner.bcf) = converted %.loc9_39.1, %.loc9_39.4
 // CHECK:STDOUT:     return %.loc9_40 to %return.param
diff --git a/toolchain/check/testdata/class/generic/stringify.carbon b/toolchain/check/testdata/class/generic/stringify.carbon
index 7fceda04696d..366c236db1fb 100644
--- a/toolchain/check/testdata/class/generic/stringify.carbon
+++ b/toolchain/check/testdata/class/generic/stringify.carbon
@@ -558,7 +558,7 @@ var g: E({.a = 1, .b = 2}) = {} as E({.a = 3, .b = 4} as D);
 // CHECK:STDOUT:     %.loc25_25.2: init %i32 = converted %int_1, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc25_25.1 [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:     %.loc25_25.3: ref %D = temporary_storage
 // CHECK:STDOUT:     %.loc25_25.4: ref %i32 = class_element_access %.loc25_25.3, element0
-// CHECK:STDOUT:     %.loc25_25.5: init %i32 to %.loc25_25.4 = initialize_from %.loc25_25.2 [concrete = constants.%int_1.5d2]
+// CHECK:STDOUT:     %.loc25_25.5: init %i32 to %.loc25_25.4 = in_place_init %.loc25_25.2 [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:     %impl.elem0.loc25_25.2: %.863 = impl_witness_access constants.%ImplicitAs.impl_witness.6bc, element0 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.0b5]
 // CHECK:STDOUT:     %bound_method.loc25_25.3: <bound method> = bound_method %int_2, %impl.elem0.loc25_25.2 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.bound.4e5]
 // CHECK:STDOUT:     %specific_fn.loc25_25.2: <specific function> = specific_function %impl.elem0.loc25_25.2, @Core.IntLiteral.as.ImplicitAs.impl.Convert(constants.%int_32) [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.specific_fn]
@@ -566,7 +566,7 @@ var g: E({.a = 1, .b = 2}) = {} as E({.a = 3, .b = 4} as D);
 // CHECK:STDOUT:     %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc25_25.2: init %i32 = call %bound_method.loc25_25.4(%int_2) [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:     %.loc25_25.6: init %i32 = converted %int_2, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc25_25.2 [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:     %.loc25_25.7: ref %i32 = class_element_access %.loc25_25.3, element1
-// CHECK:STDOUT:     %.loc25_25.8: init %i32 to %.loc25_25.7 = initialize_from %.loc25_25.6 [concrete = constants.%int_2.ef8]
+// CHECK:STDOUT:     %.loc25_25.8: init %i32 to %.loc25_25.7 = in_place_init %.loc25_25.6 [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:     %.loc25_25.9: init %D to %.loc25_25.3 = class_init (%.loc25_25.5, %.loc25_25.8) [concrete = constants.%D.val.525]
 // CHECK:STDOUT:     %.loc25_25.10: ref %D = temporary %.loc25_25.3, %.loc25_25.9
 // CHECK:STDOUT:     %.loc25_26.1: ref %D = converted %.loc25_25.1, %.loc25_25.10
@@ -621,7 +621,7 @@ var g: E({.a = 1, .b = 2}) = {} as E({.a = 3, .b = 4} as D);
 // CHECK:STDOUT:   %.loc25_53.2: init %i32 = converted %int_3, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc25_53.1 [concrete = constants.%int_3.822]
 // CHECK:STDOUT:   %.loc25_53.3: ref %D = temporary_storage
 // CHECK:STDOUT:   %.loc25_53.4: ref %i32 = class_element_access %.loc25_53.3, element0
-// CHECK:STDOUT:   %.loc25_53.5: init %i32 to %.loc25_53.4 = initialize_from %.loc25_53.2 [concrete = constants.%int_3.822]
+// CHECK:STDOUT:   %.loc25_53.5: init %i32 to %.loc25_53.4 = in_place_init %.loc25_53.2 [concrete = constants.%int_3.822]
 // CHECK:STDOUT:   %impl.elem0.loc25_53.2: %.863 = impl_witness_access constants.%ImplicitAs.impl_witness.6bc, element0 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.0b5]
 // CHECK:STDOUT:   %bound_method.loc25_53.3: <bound method> = bound_method %int_4, %impl.elem0.loc25_53.2 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.bound.f0c]
 // CHECK:STDOUT:   %specific_fn.loc25_53.2: <specific function> = specific_function %impl.elem0.loc25_53.2, @Core.IntLiteral.as.ImplicitAs.impl.Convert(constants.%int_32) [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.specific_fn]
@@ -629,7 +629,7 @@ var g: E({.a = 1, .b = 2}) = {} as E({.a = 3, .b = 4} as D);
 // CHECK:STDOUT:   %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc25_53.2: init %i32 = call %bound_method.loc25_53.4(%int_4) [concrete = constants.%int_4.940]
 // CHECK:STDOUT:   %.loc25_53.6: init %i32 = converted %int_4, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc25_53.2 [concrete = constants.%int_4.940]
 // CHECK:STDOUT:   %.loc25_53.7: ref %i32 = class_element_access %.loc25_53.3, element1
-// CHECK:STDOUT:   %.loc25_53.8: init %i32 to %.loc25_53.7 = initialize_from %.loc25_53.6 [concrete = constants.%int_4.940]
+// CHECK:STDOUT:   %.loc25_53.8: init %i32 to %.loc25_53.7 = in_place_init %.loc25_53.6 [concrete = constants.%int_4.940]
 // CHECK:STDOUT:   %.loc25_53.9: init %D to %.loc25_53.3 = class_init (%.loc25_53.5, %.loc25_53.8) [concrete = constants.%D.val.659]
 // CHECK:STDOUT:   %.loc25_53.10: ref %D = temporary %.loc25_53.3, %.loc25_53.9
 // CHECK:STDOUT:   %.loc25_55.1: ref %D = converted %.loc25_53.1, %.loc25_53.10
diff --git a/toolchain/check/testdata/class/import.carbon b/toolchain/check/testdata/class/import.carbon
index c3fb35ae1971..6f29a795b079 100644
--- a/toolchain/check/testdata/class/import.carbon
+++ b/toolchain/check/testdata/class/import.carbon
@@ -343,7 +343,7 @@ fn Run() {
 // CHECK:STDOUT:   %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc9: init %i32 = call %bound_method.loc9_25.2(%int_1) [concrete = constants.%int_1.47b]
 // CHECK:STDOUT:   %.loc9_25.2: init %i32 = converted %int_1, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc9 [concrete = constants.%int_1.47b]
 // CHECK:STDOUT:   %.loc9_25.3: ref %i32 = class_element_access %b.var, element0
-// CHECK:STDOUT:   %.loc9_25.4: init %i32 to %.loc9_25.3 = initialize_from %.loc9_25.2 [concrete = constants.%int_1.47b]
+// CHECK:STDOUT:   %.loc9_25.4: init %i32 to %.loc9_25.3 = in_place_init %.loc9_25.2 [concrete = constants.%int_1.47b]
 // CHECK:STDOUT:   %.loc9_25.5: init %Field to %b.var = class_init (%.loc9_25.4) [concrete = constants.%Field.val]
 // CHECK:STDOUT:   %.loc9_3: init %Field = converted %.loc9_25.1, %.loc9_25.5 [concrete = constants.%Field.val]
 // CHECK:STDOUT:   assign %b.var, %.loc9_3
diff --git a/toolchain/check/testdata/class/import_base.carbon b/toolchain/check/testdata/class/import_base.carbon
index 7ec711430337..87fde58250cf 100644
--- a/toolchain/check/testdata/class/import_base.carbon
+++ b/toolchain/check/testdata/class/import_base.carbon
@@ -266,7 +266,7 @@ fn Run() {
 // CHECK:STDOUT:   %.loc7_49.2: init %i32 = converted %int_0, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc7_49.1 [concrete = constants.%int_0.263]
 // CHECK:STDOUT:   %.loc7_50.2: ref %Base = class_element_access %a.var, element0
 // CHECK:STDOUT:   %.loc7_49.3: ref %i32 = class_element_access %.loc7_50.2, element0
-// CHECK:STDOUT:   %.loc7_49.4: init %i32 to %.loc7_49.3 = initialize_from %.loc7_49.2 [concrete = constants.%int_0.263]
+// CHECK:STDOUT:   %.loc7_49.4: init %i32 to %.loc7_49.3 = in_place_init %.loc7_49.2 [concrete = constants.%int_0.263]
 // CHECK:STDOUT:   %impl.elem0.loc7_49.2: %.952 = impl_witness_access constants.%ImplicitAs.impl_witness.58d, element0 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.5f4]
 // CHECK:STDOUT:   %bound_method.loc7_49.3: <bound method> = bound_method %int_1, %impl.elem0.loc7_49.2 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.bound.f07]
 // CHECK:STDOUT:   %specific_fn.loc7_49.2: <specific function> = specific_function %impl.elem0.loc7_49.2, @Core.IntLiteral.as.ImplicitAs.impl.Convert(constants.%int_32) [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.specific_fn]
@@ -274,7 +274,7 @@ fn Run() {
 // CHECK:STDOUT:   %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc7_49.2: init %i32 = call %bound_method.loc7_49.4(%int_1) [concrete = constants.%int_1.47b]
 // CHECK:STDOUT:   %.loc7_49.5: init %i32 = converted %int_1, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc7_49.2 [concrete = constants.%int_1.47b]
 // CHECK:STDOUT:   %.loc7_49.6: ref %i32 = class_element_access %.loc7_50.2, element1
-// CHECK:STDOUT:   %.loc7_49.7: init %i32 to %.loc7_49.6 = initialize_from %.loc7_49.5 [concrete = constants.%int_1.47b]
+// CHECK:STDOUT:   %.loc7_49.7: init %i32 to %.loc7_49.6 = in_place_init %.loc7_49.5 [concrete = constants.%int_1.47b]
 // CHECK:STDOUT:   %.loc7_49.8: init %Base to %.loc7_50.2 = class_init (%.loc7_49.4, %.loc7_49.7) [concrete = constants.%Base.val]
 // CHECK:STDOUT:   %.loc7_50.3: init %Base = converted %.loc7_49.1, %.loc7_49.8 [concrete = constants.%Base.val]
 // CHECK:STDOUT:   %.loc7_50.4: init %Child to %a.var = class_init (%.loc7_50.3) [concrete = constants.%Child.val]
diff --git a/toolchain/check/testdata/class/inheritance_access.carbon b/toolchain/check/testdata/class/inheritance_access.carbon
index afbf76ccdc01..ee9bb85c9f55 100644
--- a/toolchain/check/testdata/class/inheritance_access.carbon
+++ b/toolchain/check/testdata/class/inheritance_access.carbon
@@ -414,7 +414,7 @@ class B {
 // CHECK:STDOUT:   %bound_method.loc13_17.2: <bound method> = bound_method %.loc13_17.4, %specific_fn.loc13_17
 // CHECK:STDOUT:   %Int.as.Copy.impl.Op.call.loc13_17: init %i32 = call %bound_method.loc13_17.2(%.loc13_17.4)
 // CHECK:STDOUT:   %tuple.elem0: ref %i32 = tuple_access %return.param, element0
-// CHECK:STDOUT:   %.loc13_27.2: init %i32 to %tuple.elem0 = initialize_from %Int.as.Copy.impl.Op.call.loc13_17
+// CHECK:STDOUT:   %.loc13_27.2: init %i32 to %tuple.elem0 = in_place_init %Int.as.Copy.impl.Op.call.loc13_17
 // CHECK:STDOUT:   %.loc13_25.4: %i32 = acquire_value %.loc13_25.3
 // CHECK:STDOUT:   %impl.elem0.loc13_25: %.f79 = impl_witness_access constants.%Copy.impl_witness.f17, element0 [concrete = constants.%Int.as.Copy.impl.Op.664]
 // CHECK:STDOUT:   %bound_method.loc13_25.1: <bound method> = bound_method %.loc13_25.4, %impl.elem0.loc13_25
@@ -422,7 +422,7 @@ class B {
 // CHECK:STDOUT:   %bound_method.loc13_25.2: <bound method> = bound_method %.loc13_25.4, %specific_fn.loc13_25
 // CHECK:STDOUT:   %Int.as.Copy.impl.Op.call.loc13_25: init %i32 = call %bound_method.loc13_25.2(%.loc13_25.4)
 // CHECK:STDOUT:   %tuple.elem1: ref %i32 = tuple_access %return.param, element1
-// CHECK:STDOUT:   %.loc13_27.3: init %i32 to %tuple.elem1 = initialize_from %Int.as.Copy.impl.Op.call.loc13_25
+// CHECK:STDOUT:   %.loc13_27.3: init %i32 to %tuple.elem1 = in_place_init %Int.as.Copy.impl.Op.call.loc13_25
 // CHECK:STDOUT:   %.loc13_27.4: init %tuple.type.d07 to %return.param = tuple_init (%.loc13_27.2, %.loc13_27.3)
 // CHECK:STDOUT:   %.loc13_28: init %tuple.type.d07 = converted %.loc13_27.1, %.loc13_27.4
 // CHECK:STDOUT:   return %.loc13_28 to %return.param
diff --git a/toolchain/check/testdata/class/init.carbon b/toolchain/check/testdata/class/init.carbon
index 600b9357fae5..39158c0d9c72 100644
--- a/toolchain/check/testdata/class/init.carbon
+++ b/toolchain/check/testdata/class/init.carbon
@@ -173,14 +173,14 @@ fn MakeReorder(n: i32, next: Class*) -> Class {
 // CHECK:STDOUT:   %bound_method.loc21_16.2: <bound method> = bound_method %n.ref, %specific_fn.loc21_16
 // CHECK:STDOUT:   %Int.as.Copy.impl.Op.call: init %i32 = call %bound_method.loc21_16.2(%n.ref)
 // CHECK:STDOUT:   %.loc21_31.2: ref %i32 = class_element_access %return.param, element0
-// CHECK:STDOUT:   %.loc21_31.3: init %i32 to %.loc21_31.2 = initialize_from %Int.as.Copy.impl.Op.call
+// CHECK:STDOUT:   %.loc21_31.3: init %i32 to %.loc21_31.2 = in_place_init %Int.as.Copy.impl.Op.call
 // CHECK:STDOUT:   %impl.elem0.loc21_27: %.105 = impl_witness_access constants.%Copy.impl_witness.9d3, element0 [concrete = constants.%ptr.as.Copy.impl.Op.120]
 // CHECK:STDOUT:   %bound_method.loc21_27.1: <bound method> = bound_method %next.ref, %impl.elem0.loc21_27
 // CHECK:STDOUT:   %specific_fn.loc21_27: <specific function> = specific_function %impl.elem0.loc21_27, @ptr.as.Copy.impl.Op(constants.%Class) [concrete = constants.%ptr.as.Copy.impl.Op.specific_fn]
 // CHECK:STDOUT:   %bound_method.loc21_27.2: <bound method> = bound_method %next.ref, %specific_fn.loc21_27
 // CHECK:STDOUT:   %ptr.as.Copy.impl.Op.call: init %ptr.8e5 = call %bound_method.loc21_27.2(%next.ref)
 // CHECK:STDOUT:   %.loc21_31.4: ref %ptr.8e5 = class_element_access %return.param, element1
-// CHECK:STDOUT:   %.loc21_31.5: init %ptr.8e5 to %.loc21_31.4 = initialize_from %ptr.as.Copy.impl.Op.call
+// CHECK:STDOUT:   %.loc21_31.5: init %ptr.8e5 to %.loc21_31.4 = in_place_init %ptr.as.Copy.impl.Op.call
 // CHECK:STDOUT:   %.loc21_31.6: init %Class to %return.param = class_init (%.loc21_31.3, %.loc21_31.5)
 // CHECK:STDOUT:   %.loc21_32: init %Class = converted %.loc21_31.1, %.loc21_31.6
 // CHECK:STDOUT:   return %.loc21_32 to %return.param
@@ -197,14 +197,14 @@ fn MakeReorder(n: i32, next: Class*) -> Class {
 // CHECK:STDOUT:   %bound_method.loc25_30.2: <bound method> = bound_method %n.ref, %specific_fn.loc25_30
 // CHECK:STDOUT:   %Int.as.Copy.impl.Op.call: init %i32 = call %bound_method.loc25_30.2(%n.ref)
 // CHECK:STDOUT:   %.loc25_31.2: ref %i32 = class_element_access %return.param, element1
-// CHECK:STDOUT:   %.loc25_31.3: init %i32 to %.loc25_31.2 = initialize_from %Int.as.Copy.impl.Op.call
+// CHECK:STDOUT:   %.loc25_31.3: init %i32 to %.loc25_31.2 = in_place_init %Int.as.Copy.impl.Op.call
 // CHECK:STDOUT:   %impl.elem0.loc25_19: %.105 = impl_witness_access constants.%Copy.impl_witness.9d3, element0 [concrete = constants.%ptr.as.Copy.impl.Op.120]
 // CHECK:STDOUT:   %bound_method.loc25_19.1: <bound method> = bound_method %next.ref, %impl.elem0.loc25_19
 // CHECK:STDOUT:   %specific_fn.loc25_19: <specific function> = specific_function %impl.elem0.loc25_19, @ptr.as.Copy.impl.Op(constants.%Class) [concrete = constants.%ptr.as.Copy.impl.Op.specific_fn]
 // CHECK:STDOUT:   %bound_method.loc25_19.2: <bound method> = bound_method %next.ref, %specific_fn.loc25_19
 // CHECK:STDOUT:   %ptr.as.Copy.impl.Op.call: init %ptr.8e5 = call %bound_method.loc25_19.2(%next.ref)
 // CHECK:STDOUT:   %.loc25_31.4: ref %ptr.8e5 = class_element_access %return.param, element0
-// CHECK:STDOUT:   %.loc25_31.5: init %ptr.8e5 to %.loc25_31.4 = initialize_from %ptr.as.Copy.impl.Op.call
+// CHECK:STDOUT:   %.loc25_31.5: init %ptr.8e5 to %.loc25_31.4 = in_place_init %ptr.as.Copy.impl.Op.call
 // CHECK:STDOUT:   %.loc25_31.6: init %Class to %return.param = class_init (%.loc25_31.3, %.loc25_31.5)
 // CHECK:STDOUT:   %.loc25_32: init %Class = converted %.loc25_31.1, %.loc25_31.6
 // CHECK:STDOUT:   return %.loc25_32 to %return.param
diff --git a/toolchain/check/testdata/class/init_as.carbon b/toolchain/check/testdata/class/init_as.carbon
index ff8606ec99f8..b47ddee8ff42 100644
--- a/toolchain/check/testdata/class/init_as.carbon
+++ b/toolchain/check/testdata/class/init_as.carbon
@@ -146,7 +146,7 @@ fn F() -> i32 {
 // CHECK:STDOUT:   %.loc21_26.2: init %i32 = converted %int_1, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc21_26.1 [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %.loc21_26.3: ref %Class = temporary_storage
 // CHECK:STDOUT:   %.loc21_26.4: ref %i32 = class_element_access %.loc21_26.3, element0
-// CHECK:STDOUT:   %.loc21_26.5: init %i32 to %.loc21_26.4 = initialize_from %.loc21_26.2 [concrete = constants.%int_1.5d2]
+// CHECK:STDOUT:   %.loc21_26.5: init %i32 to %.loc21_26.4 = in_place_init %.loc21_26.2 [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %impl.elem0.loc21_26.2: %.863 = impl_witness_access constants.%ImplicitAs.impl_witness.6bc, element0 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.0b5]
 // CHECK:STDOUT:   %bound_method.loc21_26.3: <bound method> = bound_method %int_2, %impl.elem0.loc21_26.2 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.bound.4e5]
 // CHECK:STDOUT:   %specific_fn.loc21_26.2: <specific function> = specific_function %impl.elem0.loc21_26.2, @Core.IntLiteral.as.ImplicitAs.impl.Convert(constants.%int_32) [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.specific_fn]
@@ -154,7 +154,7 @@ fn F() -> i32 {
 // CHECK:STDOUT:   %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc21_26.2: init %i32 = call %bound_method.loc21_26.4(%int_2) [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %.loc21_26.6: init %i32 = converted %int_2, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc21_26.2 [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %.loc21_26.7: ref %i32 = class_element_access %.loc21_26.3, element1
-// CHECK:STDOUT:   %.loc21_26.8: init %i32 to %.loc21_26.7 = initialize_from %.loc21_26.6 [concrete = constants.%int_2.ef8]
+// CHECK:STDOUT:   %.loc21_26.8: init %i32 to %.loc21_26.7 = in_place_init %.loc21_26.6 [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %.loc21_26.9: init %Class to %.loc21_26.3 = class_init (%.loc21_26.5, %.loc21_26.8) [concrete = constants.%Class.val]
 // CHECK:STDOUT:   %.loc21_26.10: ref %Class = temporary %.loc21_26.3, %.loc21_26.9
 // CHECK:STDOUT:   %.loc21_28: ref %Class = converted %.loc21_26.1, %.loc21_26.10
diff --git a/toolchain/check/testdata/class/local.carbon b/toolchain/check/testdata/class/local.carbon
index 79ee86d5c751..b540c586335c 100644
--- a/toolchain/check/testdata/class/local.carbon
+++ b/toolchain/check/testdata/class/local.carbon
@@ -191,7 +191,7 @@ class A {
 // CHECK:STDOUT:   %Core.IntLiteral.as.ImplicitAs.impl.Convert.call: init %i32 = call %bound_method.loc19_39.2(%int_1) [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %.loc19_39.2: init %i32 = converted %int_1, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %.loc19_39.3: ref %i32 = class_element_access %return.param, element0
-// CHECK:STDOUT:   %.loc19_39.4: init %i32 to %.loc19_39.3 = initialize_from %.loc19_39.2 [concrete = constants.%int_1.5d2]
+// CHECK:STDOUT:   %.loc19_39.4: init %i32 to %.loc19_39.3 = in_place_init %.loc19_39.2 [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %.loc19_39.5: init %B to %return.param = class_init (%.loc19_39.4) [concrete = constants.%B.val]
 // CHECK:STDOUT:   %.loc19_18: init %B = converted %.loc19_39.1, %.loc19_39.5 [concrete = constants.%B.val]
 // CHECK:STDOUT:   assign %return.param, %.loc19_18
diff --git a/toolchain/check/testdata/class/method.carbon b/toolchain/check/testdata/class/method.carbon
index 772ad8f46b9b..be2b3e00d0b6 100644
--- a/toolchain/check/testdata/class/method.carbon
+++ b/toolchain/check/testdata/class/method.carbon
@@ -400,7 +400,7 @@ fn CallGOnInitializingExpr() -> i32 {
 // CHECK:STDOUT:   %.loc39_18.2: init %i32 = converted %int_1, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %.loc39_18.3: ref %Class = temporary_storage
 // CHECK:STDOUT:   %.loc39_18.4: ref %i32 = class_element_access %.loc39_18.3, element0
-// CHECK:STDOUT:   %.loc39_18.5: init %i32 to %.loc39_18.4 = initialize_from %.loc39_18.2 [concrete = constants.%int_1.5d2]
+// CHECK:STDOUT:   %.loc39_18.5: init %i32 to %.loc39_18.4 = in_place_init %.loc39_18.2 [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %.loc39_18.6: init %Class to %.loc39_18.3 = class_init (%.loc39_18.5) [concrete = constants.%Class.val]
 // CHECK:STDOUT:   %.loc39_18.7: ref %Class = temporary %.loc39_18.3, %.loc39_18.6
 // CHECK:STDOUT:   %.loc39_20.1: ref %Class = converted %.loc39_18.1, %.loc39_18.7
diff --git a/toolchain/check/testdata/class/raw_self.carbon b/toolchain/check/testdata/class/raw_self.carbon
index d28672db6aba..d6a93cdf91a1 100644
--- a/toolchain/check/testdata/class/raw_self.carbon
+++ b/toolchain/check/testdata/class/raw_self.carbon
@@ -212,14 +212,14 @@ fn Class.G[self: Self](r#self: i32) -> (i32, i32) {
 // CHECK:STDOUT:   %bound_method.loc26_15.2: <bound method> = bound_method %.loc26_15.2, %specific_fn.loc26_15
 // CHECK:STDOUT:   %Int.as.Copy.impl.Op.call.loc26_15: init %i32 = call %bound_method.loc26_15.2(%.loc26_15.2)
 // CHECK:STDOUT:   %tuple.elem0: ref %i32 = tuple_access %return.param.loc25, element0
-// CHECK:STDOUT:   %.loc26_25.2: init %i32 to %tuple.elem0 = initialize_from %Int.as.Copy.impl.Op.call.loc26_15
+// CHECK:STDOUT:   %.loc26_25.2: init %i32 to %tuple.elem0 = in_place_init %Int.as.Copy.impl.Op.call.loc26_15
 // CHECK:STDOUT:   %impl.elem0.loc26_19: %.f79 = impl_witness_access constants.%Copy.impl_witness.f17, element0 [concrete = constants.%Int.as.Copy.impl.Op.664]
 // CHECK:STDOUT:   %bound_method.loc26_19.1: <bound method> = bound_method %self.ref.loc26_19, %impl.elem0.loc26_19
 // CHECK:STDOUT:   %specific_fn.loc26_19: <specific function> = specific_function %impl.elem0.loc26_19, @Int.as.Copy.impl.Op(constants.%int_32) [concrete = constants.%Int.as.Copy.impl.Op.specific_fn]
 // CHECK:STDOUT:   %bound_method.loc26_19.2: <bound method> = bound_method %self.ref.loc26_19, %specific_fn.loc26_19
 // CHECK:STDOUT:   %Int.as.Copy.impl.Op.call.loc26_19: init %i32 = call %bound_method.loc26_19.2(%self.ref.loc26_19)
 // CHECK:STDOUT:   %tuple.elem1: ref %i32 = tuple_access %return.param.loc25, element1
-// CHECK:STDOUT:   %.loc26_25.3: init %i32 to %tuple.elem1 = initialize_from %Int.as.Copy.impl.Op.call.loc26_19
+// CHECK:STDOUT:   %.loc26_25.3: init %i32 to %tuple.elem1 = in_place_init %Int.as.Copy.impl.Op.call.loc26_19
 // CHECK:STDOUT:   %.loc26_25.4: init %tuple.type.d07 to %return.param.loc25 = tuple_init (%.loc26_25.2, %.loc26_25.3)
 // CHECK:STDOUT:   %.loc26_26: init %tuple.type.d07 = converted %.loc26_25.1, %.loc26_25.4
 // CHECK:STDOUT:   return %.loc26_26 to %return.param.loc25
diff --git a/toolchain/check/testdata/class/reorder_qualified.carbon b/toolchain/check/testdata/class/reorder_qualified.carbon
index 5ddb2edfd7ff..0b75980a0b70 100644
--- a/toolchain/check/testdata/class/reorder_qualified.carbon
+++ b/toolchain/check/testdata/class/reorder_qualified.carbon
@@ -266,7 +266,7 @@ class A {
 // CHECK:STDOUT:   %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc33: init %i32 = call %bound_method.loc33_25.2(%int_1) [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %.loc33_25.2: init %i32 = converted %int_1, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc33 [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %.loc33_25.3: ref %i32 = class_element_access %a.var, element0
-// CHECK:STDOUT:   %.loc33_25.4: init %i32 to %.loc33_25.3 = initialize_from %.loc33_25.2 [concrete = constants.%int_1.5d2]
+// CHECK:STDOUT:   %.loc33_25.4: init %i32 to %.loc33_25.3 = in_place_init %.loc33_25.2 [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %.loc33_25.5: init %A to %a.var = class_init (%.loc33_25.4) [concrete = constants.%A.val]
 // CHECK:STDOUT:   %.loc33_7: init %A = converted %.loc33_25.1, %.loc33_25.5 [concrete = constants.%A.val]
 // CHECK:STDOUT:   assign %a.var, %.loc33_7
@@ -286,7 +286,7 @@ class A {
 // CHECK:STDOUT:   %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc34: init %i32 = call %bound_method.loc34_25.2(%int_2) [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %.loc34_25.2: init %i32 = converted %int_2, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc34 [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %.loc34_25.3: ref %i32 = class_element_access %b.var, element0
-// CHECK:STDOUT:   %.loc34_25.4: init %i32 to %.loc34_25.3 = initialize_from %.loc34_25.2 [concrete = constants.%int_2.ef8]
+// CHECK:STDOUT:   %.loc34_25.4: init %i32 to %.loc34_25.3 = in_place_init %.loc34_25.2 [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %.loc34_25.5: init %B to %b.var = class_init (%.loc34_25.4) [concrete = constants.%B.val]
 // CHECK:STDOUT:   %.loc34_7: init %B = converted %.loc34_25.1, %.loc34_25.5 [concrete = constants.%B.val]
 // CHECK:STDOUT:   assign %b.var, %.loc34_7
@@ -306,7 +306,7 @@ class A {
 // CHECK:STDOUT:   %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc35: init %i32 = call %bound_method.loc35_25.2(%int_3) [concrete = constants.%int_3.822]
 // CHECK:STDOUT:   %.loc35_25.2: init %i32 = converted %int_3, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc35 [concrete = constants.%int_3.822]
 // CHECK:STDOUT:   %.loc35_25.3: ref %i32 = class_element_access %c.var, element0
-// CHECK:STDOUT:   %.loc35_25.4: init %i32 to %.loc35_25.3 = initialize_from %.loc35_25.2 [concrete = constants.%int_3.822]
+// CHECK:STDOUT:   %.loc35_25.4: init %i32 to %.loc35_25.3 = in_place_init %.loc35_25.2 [concrete = constants.%int_3.822]
 // CHECK:STDOUT:   %.loc35_25.5: init %C to %c.var = class_init (%.loc35_25.4) [concrete = constants.%C.val]
 // CHECK:STDOUT:   %.loc35_7: init %C = converted %.loc35_25.1, %.loc35_25.5 [concrete = constants.%C.val]
 // CHECK:STDOUT:   assign %c.var, %.loc35_7
@@ -326,7 +326,7 @@ class A {
 // CHECK:STDOUT:   %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc36: init %i32 = call %bound_method.loc36_25.2(%int_4) [concrete = constants.%int_4.940]
 // CHECK:STDOUT:   %.loc36_25.2: init %i32 = converted %int_4, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc36 [concrete = constants.%int_4.940]
 // CHECK:STDOUT:   %.loc36_25.3: ref %i32 = class_element_access %d.var, element0
-// CHECK:STDOUT:   %.loc36_25.4: init %i32 to %.loc36_25.3 = initialize_from %.loc36_25.2 [concrete = constants.%int_4.940]
+// CHECK:STDOUT:   %.loc36_25.4: init %i32 to %.loc36_25.3 = in_place_init %.loc36_25.2 [concrete = constants.%int_4.940]
 // CHECK:STDOUT:   %.loc36_25.5: init %D to %d.var = class_init (%.loc36_25.4) [concrete = constants.%D.val]
 // CHECK:STDOUT:   %.loc36_7: init %D = converted %.loc36_25.1, %.loc36_25.5 [concrete = constants.%D.val]
 // CHECK:STDOUT:   assign %d.var, %.loc36_7
diff --git a/toolchain/check/testdata/class/self_type.carbon b/toolchain/check/testdata/class/self_type.carbon
index 700b5015cdec..48650a8b8a82 100644
--- a/toolchain/check/testdata/class/self_type.carbon
+++ b/toolchain/check/testdata/class/self_type.carbon
@@ -166,7 +166,7 @@ fn Class.F[self: Self]() -> i32 {
 // CHECK:STDOUT:   %bound_method.loc19_15.2: <bound method> = bound_method %addr, %specific_fn
 // CHECK:STDOUT:   %ptr.as.Copy.impl.Op.call: init %ptr.8e5 = call %bound_method.loc19_15.2(%addr)
 // CHECK:STDOUT:   %.loc19_17.2: ref %ptr.8e5 = class_element_access %s.ref.loc19_5, element0
-// CHECK:STDOUT:   %.loc19_17.3: init %ptr.8e5 to %.loc19_17.2 = initialize_from %ptr.as.Copy.impl.Op.call
+// CHECK:STDOUT:   %.loc19_17.3: init %ptr.8e5 to %.loc19_17.2 = in_place_init %ptr.as.Copy.impl.Op.call
 // CHECK:STDOUT:   %.loc19_17.4: init %Class to %s.ref.loc19_5 = class_init (%.loc19_17.3)
 // CHECK:STDOUT:   %.loc19_7: init %Class = converted %.loc19_17.1, %.loc19_17.4
 // CHECK:STDOUT:   assign %s.ref.loc19_5, %.loc19_7
diff --git a/toolchain/check/testdata/class/virtual_modifiers.carbon b/toolchain/check/testdata/class/virtual_modifiers.carbon
index e74e341995c6..02c791b7a7d7 100644
--- a/toolchain/check/testdata/class/virtual_modifiers.carbon
+++ b/toolchain/check/testdata/class/virtual_modifiers.carbon
@@ -738,7 +738,7 @@ class T2(G2:! type) {
 // CHECK:STDOUT:   %.loc12_31.2: ref %Base = class_element_access %d.var, element0
 // CHECK:STDOUT:   %.loc12_30.2: ref %ptr.454 = class_element_access %.loc12_31.2, element0
 // CHECK:STDOUT:   %Derived.vtable_ptr: ref %ptr.454 = vtable_ptr @Derived.vtable [concrete = constants.%Derived.vtable_ptr]
-// CHECK:STDOUT:   %.loc12_30.3: init %ptr.454 to %.loc12_30.2 = initialize_from %Derived.vtable_ptr [concrete = constants.%Derived.vtable_ptr]
+// CHECK:STDOUT:   %.loc12_30.3: init %ptr.454 to %.loc12_30.2 = in_place_init %Derived.vtable_ptr [concrete = constants.%Derived.vtable_ptr]
 // CHECK:STDOUT:   %.loc12_30.4: init %Base to %.loc12_31.2 = class_init (%.loc12_30.3) [concrete = constants.%Base.val]
 // CHECK:STDOUT:   %.loc12_31.3: init %Base = converted %.loc12_30.1, %.loc12_30.4 [concrete = constants.%Base.val]
 // CHECK:STDOUT:   %.loc12_31.4: init %Derived to %d.var = class_init (%.loc12_31.3) [concrete = constants.%Derived.val]
@@ -922,7 +922,7 @@ class T2(G2:! type) {
 // CHECK:STDOUT:   %.loc7_28.1: %empty_struct_type = struct_literal () [concrete = constants.%empty_struct]
 // CHECK:STDOUT:   %.loc7_28.2: ref %ptr.454 = class_element_access %v.var, element0
 // CHECK:STDOUT:   %Base.vtable_ptr: ref %ptr.454 = vtable_ptr @Base.vtable [concrete = constants.%Base.vtable_ptr]
-// CHECK:STDOUT:   %.loc7_28.3: init %ptr.454 to %.loc7_28.2 = initialize_from %Base.vtable_ptr [concrete = constants.%Base.vtable_ptr]
+// CHECK:STDOUT:   %.loc7_28.3: init %ptr.454 to %.loc7_28.2 = in_place_init %Base.vtable_ptr [concrete = constants.%Base.vtable_ptr]
 // CHECK:STDOUT:   %.loc7_28.4: init %Base to %v.var = class_init (%.loc7_28.3) [concrete = constants.%Base.val]
 // CHECK:STDOUT:   %.loc7_3: init %Base = converted %.loc7_28.1, %.loc7_28.4 [concrete = constants.%Base.val]
 // CHECK:STDOUT:   assign %v.var, %.loc7_3
@@ -1207,7 +1207,7 @@ class T2(G2:! type) {
 // CHECK:STDOUT:   %.loc19_17.1: %empty_struct_type = struct_literal () [concrete = constants.%empty_struct]
 // CHECK:STDOUT:   %.loc19_17.2: ref %ptr.454 = class_element_access %b1.var, element0
 // CHECK:STDOUT:   %B1.vtable_ptr: ref %ptr.454 = vtable_ptr @B1.vtable [concrete = constants.%B1.vtable_ptr]
-// CHECK:STDOUT:   %.loc19_17.3: init %ptr.454 to %.loc19_17.2 = initialize_from %B1.vtable_ptr [concrete = constants.%B1.vtable_ptr]
+// CHECK:STDOUT:   %.loc19_17.3: init %ptr.454 to %.loc19_17.2 = in_place_init %B1.vtable_ptr [concrete = constants.%B1.vtable_ptr]
 // CHECK:STDOUT:   %.loc19_17.4: init %B1 to %b1.var = class_init (%.loc19_17.3) [concrete = constants.%B1.val.d17]
 // CHECK:STDOUT:   %.loc19_3: init %B1 = converted %.loc19_17.1, %.loc19_17.4 [concrete = constants.%B1.val.d17]
 // CHECK:STDOUT:   assign %b1.var, %.loc19_3
@@ -1223,7 +1223,7 @@ class T2(G2:! type) {
 // CHECK:STDOUT:   %.loc20_27.2: ref %B1 = class_element_access %b2.var, element0
 // CHECK:STDOUT:   %.loc20_26.2: ref %ptr.454 = class_element_access %.loc20_27.2, element0
 // CHECK:STDOUT:   %B2.vtable_ptr: ref %ptr.454 = vtable_ptr @B2.vtable [concrete = constants.%B2.vtable_ptr]
-// CHECK:STDOUT:   %.loc20_26.3: init %ptr.454 to %.loc20_26.2 = initialize_from %B2.vtable_ptr [concrete = constants.%B2.vtable_ptr]
+// CHECK:STDOUT:   %.loc20_26.3: init %ptr.454 to %.loc20_26.2 = in_place_init %B2.vtable_ptr [concrete = constants.%B2.vtable_ptr]
 // CHECK:STDOUT:   %.loc20_26.4: init %B1 to %.loc20_27.2 = class_init (%.loc20_26.3) [concrete = constants.%B1.val.f0b]
 // CHECK:STDOUT:   %.loc20_27.3: init %B1 = converted %.loc20_26.1, %.loc20_26.4 [concrete = constants.%B1.val.f0b]
 // CHECK:STDOUT:   %.loc20_27.4: init %B2 to %b2.var = class_init (%.loc20_27.3) [concrete = constants.%B2.val.e28]
@@ -1243,7 +1243,7 @@ class T2(G2:! type) {
 // CHECK:STDOUT:   %.loc21_34.2: ref %B1 = class_element_access %.loc21_35.2, element0
 // CHECK:STDOUT:   %.loc21_33.2: ref %ptr.454 = class_element_access %.loc21_34.2, element0
 // CHECK:STDOUT:   %C.vtable_ptr: ref %ptr.454 = vtable_ptr @C.vtable [concrete = constants.%C.vtable_ptr]
-// CHECK:STDOUT:   %.loc21_33.3: init %ptr.454 to %.loc21_33.2 = initialize_from %C.vtable_ptr [concrete = constants.%C.vtable_ptr]
+// CHECK:STDOUT:   %.loc21_33.3: init %ptr.454 to %.loc21_33.2 = in_place_init %C.vtable_ptr [concrete = constants.%C.vtable_ptr]
 // CHECK:STDOUT:   %.loc21_33.4: init %B1 to %.loc21_34.2 = class_init (%.loc21_33.3) [concrete = constants.%B1.val.dd4]
 // CHECK:STDOUT:   %.loc21_34.3: init %B1 = converted %.loc21_33.1, %.loc21_33.4 [concrete = constants.%B1.val.dd4]
 // CHECK:STDOUT:   %.loc21_34.4: init %B2 to %.loc21_35.2 = class_init (%.loc21_34.3) [concrete = constants.%B2.val.b52]
@@ -1475,7 +1475,7 @@ class T2(G2:! type) {
 // CHECK:STDOUT:   %.loc13_35.1: %struct_type.m2.m1.68c = struct_literal (%i.ref.loc13_25, %i.ref.loc13_34)
 // CHECK:STDOUT:   %.loc13_35.2: ref %ptr.454 = class_element_access %b1.var, element0
 // CHECK:STDOUT:   %Base.vtable_ptr.loc13: ref %ptr.454 = vtable_ptr @Base.vtable [concrete = constants.%Base.vtable_ptr]
-// CHECK:STDOUT:   %.loc13_35.3: init %ptr.454 to %.loc13_35.2 = initialize_from %Base.vtable_ptr.loc13 [concrete = constants.%Base.vtable_ptr]
+// CHECK:STDOUT:   %.loc13_35.3: init %ptr.454 to %.loc13_35.2 = in_place_init %Base.vtable_ptr.loc13 [concrete = constants.%Base.vtable_ptr]
 // CHECK:STDOUT:   %.loc13_34: %i32 = acquire_value %i.ref.loc13_34
 // CHECK:STDOUT:   %impl.elem0.loc13_34: %.f79 = impl_witness_access constants.%Copy.impl_witness.f17, element0 [concrete = constants.%Int.as.Copy.impl.Op.664]
 // CHECK:STDOUT:   %bound_method.loc13_34.1: <bound method> = bound_method %.loc13_34, %impl.elem0.loc13_34
@@ -1483,7 +1483,7 @@ class T2(G2:! type) {
 // CHECK:STDOUT:   %bound_method.loc13_34.2: <bound method> = bound_method %.loc13_34, %specific_fn.loc13_34
 // CHECK:STDOUT:   %Int.as.Copy.impl.Op.call.loc13_34: init %i32 = call %bound_method.loc13_34.2(%.loc13_34)
 // CHECK:STDOUT:   %.loc13_35.4: ref %i32 = class_element_access %b1.var, element2
-// CHECK:STDOUT:   %.loc13_35.5: init %i32 to %.loc13_35.4 = initialize_from %Int.as.Copy.impl.Op.call.loc13_34
+// CHECK:STDOUT:   %.loc13_35.5: init %i32 to %.loc13_35.4 = in_place_init %Int.as.Copy.impl.Op.call.loc13_34
 // CHECK:STDOUT:   %.loc13_25: %i32 = acquire_value %i.ref.loc13_25
 // CHECK:STDOUT:   %impl.elem0.loc13_25: %.f79 = impl_witness_access constants.%Copy.impl_witness.f17, element0 [concrete = constants.%Int.as.Copy.impl.Op.664]
 // CHECK:STDOUT:   %bound_method.loc13_25.1: <bound method> = bound_method %.loc13_25, %impl.elem0.loc13_25
@@ -1491,7 +1491,7 @@ class T2(G2:! type) {
 // CHECK:STDOUT:   %bound_method.loc13_25.2: <bound method> = bound_method %.loc13_25, %specific_fn.loc13_25
 // CHECK:STDOUT:   %Int.as.Copy.impl.Op.call.loc13_25: init %i32 = call %bound_method.loc13_25.2(%.loc13_25)
 // CHECK:STDOUT:   %.loc13_35.6: ref %i32 = class_element_access %b1.var, element1
-// CHECK:STDOUT:   %.loc13_35.7: init %i32 to %.loc13_35.6 = initialize_from %Int.as.Copy.impl.Op.call.loc13_25
+// CHECK:STDOUT:   %.loc13_35.7: init %i32 to %.loc13_35.6 = in_place_init %Int.as.Copy.impl.Op.call.loc13_25
 // CHECK:STDOUT:   %.loc13_35.8: init %Base to %b1.var = class_init (%.loc13_35.3, %.loc13_35.5, %.loc13_35.7)
 // CHECK:STDOUT:   %.loc13_3: init %Base = converted %.loc13_35.1, %.loc13_35.8
 // CHECK:STDOUT:   assign %b1.var, %.loc13_3
@@ -1507,7 +1507,7 @@ class T2(G2:! type) {
 // CHECK:STDOUT:   %.loc14_35.1: %struct_type.m2.m1.5f2 = struct_literal (%int_3.loc14, %int_5) [concrete = constants.%struct]
 // CHECK:STDOUT:   %.loc14_35.2: ref %ptr.454 = class_element_access %b2.var, element0
 // CHECK:STDOUT:   %Base.vtable_ptr.loc14: ref %ptr.454 = vtable_ptr @Base.vtable [concrete = constants.%Base.vtable_ptr]
-// CHECK:STDOUT:   %.loc14_35.3: init %ptr.454 to %.loc14_35.2 = initialize_from %Base.vtable_ptr.loc14 [concrete = constants.%Base.vtable_ptr]
+// CHECK:STDOUT:   %.loc14_35.3: init %ptr.454 to %.loc14_35.2 = in_place_init %Base.vtable_ptr.loc14 [concrete = constants.%Base.vtable_ptr]
 // CHECK:STDOUT:   %impl.elem0.loc14_35.1: %.863 = impl_witness_access constants.%ImplicitAs.impl_witness.6bc, element0 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.0b5]
 // CHECK:STDOUT:   %bound_method.loc14_35.1: <bound method> = bound_method %int_5, %impl.elem0.loc14_35.1 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.bound.005]
 // CHECK:STDOUT:   %specific_fn.loc14_35.1: <specific function> = specific_function %impl.elem0.loc14_35.1, @Core.IntLiteral.as.ImplicitAs.impl.Convert(constants.%int_32) [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.specific_fn]
@@ -1515,7 +1515,7 @@ class T2(G2:! type) {
 // CHECK:STDOUT:   %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc14_35.1: init %i32 = call %bound_method.loc14_35.2(%int_5) [concrete = constants.%int_5.0f6]
 // CHECK:STDOUT:   %.loc14_35.4: init %i32 = converted %int_5, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc14_35.1 [concrete = constants.%int_5.0f6]
 // CHECK:STDOUT:   %.loc14_35.5: ref %i32 = class_element_access %b2.var, element2
-// CHECK:STDOUT:   %.loc14_35.6: init %i32 to %.loc14_35.5 = initialize_from %.loc14_35.4 [concrete = constants.%int_5.0f6]
+// CHECK:STDOUT:   %.loc14_35.6: init %i32 to %.loc14_35.5 = in_place_init %.loc14_35.4 [concrete = constants.%int_5.0f6]
 // CHECK:STDOUT:   %impl.elem0.loc14_35.2: %.863 = impl_witness_access constants.%ImplicitAs.impl_witness.6bc, element0 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.0b5]
 // CHECK:STDOUT:   %bound_method.loc14_35.3: <bound method> = bound_method %int_3.loc14, %impl.elem0.loc14_35.2 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.bound.061]
 // CHECK:STDOUT:   %specific_fn.loc14_35.2: <specific function> = specific_function %impl.elem0.loc14_35.2, @Core.IntLiteral.as.ImplicitAs.impl.Convert(constants.%int_32) [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.specific_fn]
@@ -1523,7 +1523,7 @@ class T2(G2:! type) {
 // CHECK:STDOUT:   %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc14_35.2: init %i32 = call %bound_method.loc14_35.4(%int_3.loc14) [concrete = constants.%int_3.822]
 // CHECK:STDOUT:   %.loc14_35.7: init %i32 = converted %int_3.loc14, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc14_35.2 [concrete = constants.%int_3.822]
 // CHECK:STDOUT:   %.loc14_35.8: ref %i32 = class_element_access %b2.var, element1
-// CHECK:STDOUT:   %.loc14_35.9: init %i32 to %.loc14_35.8 = initialize_from %.loc14_35.7 [concrete = constants.%int_3.822]
+// CHECK:STDOUT:   %.loc14_35.9: init %i32 to %.loc14_35.8 = in_place_init %.loc14_35.7 [concrete = constants.%int_3.822]
 // CHECK:STDOUT:   %.loc14_35.10: init %Base to %b2.var = class_init (%.loc14_35.3, %.loc14_35.6, %.loc14_35.9) [concrete = constants.%Base.val]
 // CHECK:STDOUT:   %.loc14_3: init %Base = converted %.loc14_35.1, %.loc14_35.10 [concrete = constants.%Base.val]
 // CHECK:STDOUT:   assign %b2.var, %.loc14_3
@@ -4903,7 +4903,7 @@ class T2(G2:! type) {
 // CHECK:STDOUT:   %.loc7_20.1: %empty_struct_type = struct_literal () [concrete = constants.%empty_struct]
 // CHECK:STDOUT:   %.loc7_20.2: ref %ptr.454 = class_element_access file.%v.var, element0 [concrete = constants.%.ae5]
 // CHECK:STDOUT:   %Base.vtable_ptr: ref %ptr.454 = vtable_ptr @Base.vtable, @Base(constants.%T1) [concrete = constants.%Base.vtable_ptr]
-// CHECK:STDOUT:   %.loc7_20.3: init %ptr.454 to %.loc7_20.2 = initialize_from %Base.vtable_ptr [concrete = constants.%Base.vtable_ptr]
+// CHECK:STDOUT:   %.loc7_20.3: init %ptr.454 to %.loc7_20.2 = in_place_init %Base.vtable_ptr [concrete = constants.%Base.vtable_ptr]
 // CHECK:STDOUT:   %.loc7_20.4: init %Base.d5d to file.%v.var = class_init (%.loc7_20.3) [concrete = constants.%Base.val]
 // CHECK:STDOUT:   %.loc7_1: init %Base.d5d = converted %.loc7_20.1, %.loc7_20.4 [concrete = constants.%Base.val]
 // CHECK:STDOUT:   assign file.%v.var, %.loc7_1
diff --git a/toolchain/check/testdata/deduce/value_with_type_through_access.carbon b/toolchain/check/testdata/deduce/value_with_type_through_access.carbon
index 7023a6d66bba..5ea6ec3ee14e 100644
--- a/toolchain/check/testdata/deduce/value_with_type_through_access.carbon
+++ b/toolchain/check/testdata/deduce/value_with_type_through_access.carbon
@@ -736,7 +736,7 @@ fn G() {
 // CHECK:STDOUT:   %type.as.Copy.impl.Op.call: init type = call %bound_method(%C.ref) [concrete = constants.%C]
 // CHECK:STDOUT:   %.loc37_12.2: ref %Class = temporary_storage
 // CHECK:STDOUT:   %.loc37_12.3: ref type = class_element_access %.loc37_12.2, element0
-// CHECK:STDOUT:   %.loc37_12.4: init type to %.loc37_12.3 = initialize_from %type.as.Copy.impl.Op.call [concrete = constants.%C]
+// CHECK:STDOUT:   %.loc37_12.4: init type to %.loc37_12.3 = in_place_init %type.as.Copy.impl.Op.call [concrete = constants.%C]
 // CHECK:STDOUT:   %.loc37_12.5: init %Class to %.loc37_12.2 = class_init (%.loc37_12.4) [concrete = constants.%Class.val]
 // CHECK:STDOUT:   %.loc37_12.6: ref %Class = temporary %.loc37_12.2, %.loc37_12.5
 // CHECK:STDOUT:   %.loc37_13.1: ref %Class = converted %.loc37_12.1, %.loc37_12.6
@@ -963,7 +963,7 @@ fn G() {
 // CHECK:STDOUT:   %.loc24_25.2: ref %array_type = temporary_storage
 // CHECK:STDOUT:   %int_0: Core.IntLiteral = int_value 0 [concrete = constants.%int_0.5c6]
 // CHECK:STDOUT:   %.loc24_25.3: ref type = array_index %.loc24_25.2, %int_0
-// CHECK:STDOUT:   %.loc24_25.4: init type to %.loc24_25.3 = initialize_from %type.as.Copy.impl.Op.call [concrete = constants.%C]
+// CHECK:STDOUT:   %.loc24_25.4: init type to %.loc24_25.3 = in_place_init %type.as.Copy.impl.Op.call [concrete = constants.%C]
 // CHECK:STDOUT:   %.loc24_25.5: init %array_type to %.loc24_25.2 = array_init (%.loc24_25.4) [concrete = constants.%array]
 // CHECK:STDOUT:   %.loc24_27.1: init %array_type = converted %.loc24_25.1, %.loc24_25.5 [concrete = constants.%array]
 // CHECK:STDOUT:   %.loc24_27.2: ref %array_type = temporary %.loc24_25.2, %.loc24_27.1
diff --git a/toolchain/check/testdata/eval/aggregates.carbon b/toolchain/check/testdata/eval/aggregates.carbon
index 599c7e943456..aace79621ac4 100644
--- a/toolchain/check/testdata/eval/aggregates.carbon
+++ b/toolchain/check/testdata/eval/aggregates.carbon
@@ -232,7 +232,7 @@ fn G(N:! i32) {
 // CHECK:STDOUT:   %bound_method.loc4_37.2: <bound method> = bound_method %tuple.elem0.loc4_37.1, %specific_fn.loc4_37.1 [concrete = constants.%bound_method.4d7]
 // CHECK:STDOUT:   %Int.as.Copy.impl.Op.call.loc4_37.1: init %i32 = call %bound_method.loc4_37.2(%tuple.elem0.loc4_37.1) [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %tuple.elem0.loc4_37.2: ref %i32 = tuple_access file.%tuple_copy.var, element0 [concrete = constants.%tuple.elem0]
-// CHECK:STDOUT:   %.loc4_37.2: init %i32 to %tuple.elem0.loc4_37.2 = initialize_from %Int.as.Copy.impl.Op.call.loc4_37.1 [concrete = constants.%int_1.5d2]
+// CHECK:STDOUT:   %.loc4_37.2: init %i32 to %tuple.elem0.loc4_37.2 = in_place_init %Int.as.Copy.impl.Op.call.loc4_37.1 [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %tuple.elem1.loc4_37.1: %i32 = tuple_access %.loc4_37.1, element1 [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %impl.elem0.loc4_37.2: %.f79 = impl_witness_access constants.%Copy.impl_witness.f17, element0 [concrete = constants.%Int.as.Copy.impl.Op.664]
 // CHECK:STDOUT:   %bound_method.loc4_37.3: <bound method> = bound_method %tuple.elem1.loc4_37.1, %impl.elem0.loc4_37.2 [concrete = constants.%Int.as.Copy.impl.Op.bound.5e8]
@@ -240,7 +240,7 @@ fn G(N:! i32) {
 // CHECK:STDOUT:   %bound_method.loc4_37.4: <bound method> = bound_method %tuple.elem1.loc4_37.1, %specific_fn.loc4_37.2 [concrete = constants.%bound_method.f15]
 // CHECK:STDOUT:   %Int.as.Copy.impl.Op.call.loc4_37.2: init %i32 = call %bound_method.loc4_37.4(%tuple.elem1.loc4_37.1) [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %tuple.elem1.loc4_37.2: ref %i32 = tuple_access file.%tuple_copy.var, element1 [concrete = constants.%tuple.elem1]
-// CHECK:STDOUT:   %.loc4_37.3: init %i32 to %tuple.elem1.loc4_37.2 = initialize_from %Int.as.Copy.impl.Op.call.loc4_37.2 [concrete = constants.%int_2.ef8]
+// CHECK:STDOUT:   %.loc4_37.3: init %i32 to %tuple.elem1.loc4_37.2 = in_place_init %Int.as.Copy.impl.Op.call.loc4_37.2 [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %.loc4_37.4: init %tuple.type.d07 to file.%tuple_copy.var = tuple_init (%.loc4_37.2, %.loc4_37.3) [concrete = constants.%tuple.21c]
 // CHECK:STDOUT:   %.loc4_1: init %tuple.type.d07 = converted %.loc4_37.1, %.loc4_37.4 [concrete = constants.%tuple.21c]
 // CHECK:STDOUT:   assign file.%tuple_copy.var, %.loc4_1
@@ -285,7 +285,7 @@ fn G(N:! i32) {
 // CHECK:STDOUT:   %bound_method.loc6_73.2: <bound method> = bound_method %.loc6_73.2, %specific_fn.loc6_73.1 [concrete = constants.%bound_method.4d7]
 // CHECK:STDOUT:   %Int.as.Copy.impl.Op.call.loc6_73.1: init %i32 = call %bound_method.loc6_73.2(%.loc6_73.2) [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %.loc6_73.3: ref %i32 = struct_access file.%struct_copy.var, element1 [concrete = constants.%.460]
-// CHECK:STDOUT:   %.loc6_73.4: init %i32 to %.loc6_73.3 = initialize_from %Int.as.Copy.impl.Op.call.loc6_73.1 [concrete = constants.%int_1.5d2]
+// CHECK:STDOUT:   %.loc6_73.4: init %i32 to %.loc6_73.3 = in_place_init %Int.as.Copy.impl.Op.call.loc6_73.1 [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %.loc6_73.5: %i32 = struct_access %.loc6_73.1, element0 [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %impl.elem0.loc6_73.2: %.f79 = impl_witness_access constants.%Copy.impl_witness.f17, element0 [concrete = constants.%Int.as.Copy.impl.Op.664]
 // CHECK:STDOUT:   %bound_method.loc6_73.3: <bound method> = bound_method %.loc6_73.5, %impl.elem0.loc6_73.2 [concrete = constants.%Int.as.Copy.impl.Op.bound.5e8]
@@ -293,7 +293,7 @@ fn G(N:! i32) {
 // CHECK:STDOUT:   %bound_method.loc6_73.4: <bound method> = bound_method %.loc6_73.5, %specific_fn.loc6_73.2 [concrete = constants.%bound_method.f15]
 // CHECK:STDOUT:   %Int.as.Copy.impl.Op.call.loc6_73.2: init %i32 = call %bound_method.loc6_73.4(%.loc6_73.5) [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %.loc6_73.6: ref %i32 = struct_access file.%struct_copy.var, element0 [concrete = constants.%.61f]
-// CHECK:STDOUT:   %.loc6_73.7: init %i32 to %.loc6_73.6 = initialize_from %Int.as.Copy.impl.Op.call.loc6_73.2 [concrete = constants.%int_2.ef8]
+// CHECK:STDOUT:   %.loc6_73.7: init %i32 to %.loc6_73.6 = in_place_init %Int.as.Copy.impl.Op.call.loc6_73.2 [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %.loc6_73.8: %i32 = struct_access %.loc6_73.1, element2 [concrete = constants.%int_3.822]
 // CHECK:STDOUT:   %impl.elem0.loc6_73.3: %.f79 = impl_witness_access constants.%Copy.impl_witness.f17, element0 [concrete = constants.%Int.as.Copy.impl.Op.664]
 // CHECK:STDOUT:   %bound_method.loc6_73.5: <bound method> = bound_method %.loc6_73.8, %impl.elem0.loc6_73.3 [concrete = constants.%Int.as.Copy.impl.Op.bound.ecc]
@@ -301,7 +301,7 @@ fn G(N:! i32) {
 // CHECK:STDOUT:   %bound_method.loc6_73.6: <bound method> = bound_method %.loc6_73.8, %specific_fn.loc6_73.3 [concrete = constants.%bound_method.4f5]
 // CHECK:STDOUT:   %Int.as.Copy.impl.Op.call.loc6_73.3: init %i32 = call %bound_method.loc6_73.6(%.loc6_73.8) [concrete = constants.%int_3.822]
 // CHECK:STDOUT:   %.loc6_73.9: ref %i32 = struct_access file.%struct_copy.var, element2 [concrete = constants.%.f68]
-// CHECK:STDOUT:   %.loc6_73.10: init %i32 to %.loc6_73.9 = initialize_from %Int.as.Copy.impl.Op.call.loc6_73.3 [concrete = constants.%int_3.822]
+// CHECK:STDOUT:   %.loc6_73.10: init %i32 to %.loc6_73.9 = in_place_init %Int.as.Copy.impl.Op.call.loc6_73.3 [concrete = constants.%int_3.822]
 // CHECK:STDOUT:   %.loc6_73.11: init %struct_type.a.b.c to file.%struct_copy.var = struct_init (%.loc6_73.4, %.loc6_73.7, %.loc6_73.10) [concrete = constants.%struct.cff]
 // CHECK:STDOUT:   %.loc6_1: init %struct_type.a.b.c = converted %.loc6_73.1, %.loc6_73.11 [concrete = constants.%struct.cff]
 // CHECK:STDOUT:   assign file.%struct_copy.var, %.loc6_1
@@ -328,7 +328,7 @@ fn G(N:! i32) {
 // CHECK:STDOUT:   %.loc8_1: ref %array_type = splice_block file.%tuple_index.var [concrete = file.%tuple_index.var] {}
 // CHECK:STDOUT:   %int_0.loc8_37: Core.IntLiteral = int_value 0 [concrete = constants.%int_0.5c6]
 // CHECK:STDOUT:   %.loc8_37.3: ref %i32 = array_index %.loc8_1, %int_0.loc8_37
-// CHECK:STDOUT:   %.loc8_37.4: init %i32 to %.loc8_37.3 = initialize_from %.loc8_37.2 [concrete = constants.%int_0.6a9]
+// CHECK:STDOUT:   %.loc8_37.4: init %i32 to %.loc8_37.3 = in_place_init %.loc8_37.2 [concrete = constants.%int_0.6a9]
 // CHECK:STDOUT:   %.loc8_37.5: init %array_type to %.loc8_1 = array_init (%.loc8_37.4) [concrete = constants.%array]
 // CHECK:STDOUT:   %.loc8_39: init %array_type = converted %.loc8_37.1, %.loc8_37.5 [concrete = constants.%array]
 // CHECK:STDOUT:   assign file.%tuple_index.var, %.loc8_39
@@ -352,7 +352,7 @@ fn G(N:! i32) {
 // CHECK:STDOUT:   %.loc10_1: ref %array_type = splice_block file.%struct_access.var [concrete = file.%struct_access.var] {}
 // CHECK:STDOUT:   %int_0.loc10_39: Core.IntLiteral = int_value 0 [concrete = constants.%int_0.5c6]
 // CHECK:STDOUT:   %.loc10_39.3: ref %i32 = array_index %.loc10_1, %int_0.loc10_39
-// CHECK:STDOUT:   %.loc10_39.4: init %i32 to %.loc10_39.3 = initialize_from %.loc10_39.2 [concrete = constants.%int_0.6a9]
+// CHECK:STDOUT:   %.loc10_39.4: init %i32 to %.loc10_39.3 = in_place_init %.loc10_39.2 [concrete = constants.%int_0.6a9]
 // CHECK:STDOUT:   %.loc10_39.5: init %array_type to %.loc10_1 = array_init (%.loc10_39.4) [concrete = constants.%array]
 // CHECK:STDOUT:   %.loc10_41: init %array_type = converted %.loc10_39.1, %.loc10_39.5 [concrete = constants.%array]
 // CHECK:STDOUT:   assign file.%struct_access.var, %.loc10_41
@@ -452,7 +452,7 @@ fn G(N:! i32) {
 // CHECK:STDOUT:   %.loc9_65.3: ref %array_type.f32 = temporary_storage
 // CHECK:STDOUT:   %int_0.loc9_65: Core.IntLiteral = int_value 0 [concrete = constants.%int_0]
 // CHECK:STDOUT:   %.loc9_65.4: ref %i32 = array_index %.loc9_65.3, %int_0.loc9_65
-// CHECK:STDOUT:   %.loc9_65.5: init %i32 to %.loc9_65.4 = initialize_from %.loc9_65.2 [concrete = constants.%int_5.0f6]
+// CHECK:STDOUT:   %.loc9_65.5: init %i32 to %.loc9_65.4 = in_place_init %.loc9_65.2 [concrete = constants.%int_5.0f6]
 // CHECK:STDOUT:   %impl.elem0.loc9_65.2: %.863 = impl_witness_access constants.%ImplicitAs.impl_witness.6bc, element0 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.0b5]
 // CHECK:STDOUT:   %bound_method.loc9_65.3: <bound method> = bound_method %int_7, %impl.elem0.loc9_65.2 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.bound.1e0]
 // CHECK:STDOUT:   %specific_fn.loc9_65.2: <specific function> = specific_function %impl.elem0.loc9_65.2, @Core.IntLiteral.as.ImplicitAs.impl.Convert(constants.%int_32) [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.specific_fn]
@@ -461,7 +461,7 @@ fn G(N:! i32) {
 // CHECK:STDOUT:   %.loc9_65.6: init %i32 = converted %int_7, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc9_65.2 [concrete = constants.%int_7.0b1]
 // CHECK:STDOUT:   %int_1.loc9_65: Core.IntLiteral = int_value 1 [concrete = constants.%int_1.5b8]
 // CHECK:STDOUT:   %.loc9_65.7: ref %i32 = array_index %.loc9_65.3, %int_1.loc9_65
-// CHECK:STDOUT:   %.loc9_65.8: init %i32 to %.loc9_65.7 = initialize_from %.loc9_65.6 [concrete = constants.%int_7.0b1]
+// CHECK:STDOUT:   %.loc9_65.8: init %i32 to %.loc9_65.7 = in_place_init %.loc9_65.6 [concrete = constants.%int_7.0b1]
 // CHECK:STDOUT:   %impl.elem0.loc9_65.3: %.863 = impl_witness_access constants.%ImplicitAs.impl_witness.6bc, element0 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.0b5]
 // CHECK:STDOUT:   %bound_method.loc9_65.5: <bound method> = bound_method %int_1.loc9_61, %impl.elem0.loc9_65.3 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.bound.215]
 // CHECK:STDOUT:   %specific_fn.loc9_65.3: <specific function> = specific_function %impl.elem0.loc9_65.3, @Core.IntLiteral.as.ImplicitAs.impl.Convert(constants.%int_32) [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.specific_fn]
@@ -470,7 +470,7 @@ fn G(N:! i32) {
 // CHECK:STDOUT:   %.loc9_65.9: init %i32 = converted %int_1.loc9_61, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc9_65.3 [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %int_2.loc9_65: Core.IntLiteral = int_value 2 [concrete = constants.%int_2.ecc]
 // CHECK:STDOUT:   %.loc9_65.10: ref %i32 = array_index %.loc9_65.3, %int_2.loc9_65
-// CHECK:STDOUT:   %.loc9_65.11: init %i32 to %.loc9_65.10 = initialize_from %.loc9_65.9 [concrete = constants.%int_1.5d2]
+// CHECK:STDOUT:   %.loc9_65.11: init %i32 to %.loc9_65.10 = in_place_init %.loc9_65.9 [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %impl.elem0.loc9_65.4: %.863 = impl_witness_access constants.%ImplicitAs.impl_witness.6bc, element0 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.0b5]
 // CHECK:STDOUT:   %bound_method.loc9_65.7: <bound method> = bound_method %int_9, %impl.elem0.loc9_65.4 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.bound.87d]
 // CHECK:STDOUT:   %specific_fn.loc9_65.4: <specific function> = specific_function %impl.elem0.loc9_65.4, @Core.IntLiteral.as.ImplicitAs.impl.Convert(constants.%int_32) [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.specific_fn]
@@ -479,7 +479,7 @@ fn G(N:! i32) {
 // CHECK:STDOUT:   %.loc9_65.12: init %i32 = converted %int_9, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc9_65.4 [concrete = constants.%int_9.f88]
 // CHECK:STDOUT:   %int_3: Core.IntLiteral = int_value 3 [concrete = constants.%int_3]
 // CHECK:STDOUT:   %.loc9_65.13: ref %i32 = array_index %.loc9_65.3, %int_3
-// CHECK:STDOUT:   %.loc9_65.14: init %i32 to %.loc9_65.13 = initialize_from %.loc9_65.12 [concrete = constants.%int_9.f88]
+// CHECK:STDOUT:   %.loc9_65.14: init %i32 to %.loc9_65.13 = in_place_init %.loc9_65.12 [concrete = constants.%int_9.f88]
 // CHECK:STDOUT:   %.loc9_65.15: init %array_type.f32 to %.loc9_65.3 = array_init (%.loc9_65.5, %.loc9_65.8, %.loc9_65.11, %.loc9_65.14) [concrete = constants.%array]
 // CHECK:STDOUT:   %.loc9_67.1: init %array_type.f32 = converted %.loc9_65.1, %.loc9_65.15 [concrete = constants.%array]
 // CHECK:STDOUT:   %int_2.loc9_85: Core.IntLiteral = int_value 2 [concrete = constants.%int_2.ecc]
diff --git a/toolchain/check/testdata/for/actual.carbon b/toolchain/check/testdata/for/actual.carbon
index ff542cae5f0a..6dcc3c3f75bc 100644
--- a/toolchain/check/testdata/for/actual.carbon
+++ b/toolchain/check/testdata/for/actual.carbon
@@ -511,14 +511,14 @@ fn Read(y:! Core.IntLiteral()) {
 // CHECK:STDOUT:     %bound_method.loc6_22.2: <bound method> = bound_method %start.ref, %specific_impl_fn.loc6_22.1
 // CHECK:STDOUT:     %Copy.Op.call.loc6_22: init @IntRange.Make.%Int.loc5_28.1 (%Int.fc6021.1) = call %bound_method.loc6_22.2(%start.ref)
 // CHECK:STDOUT:     %.loc6_39.2: ref @IntRange.Make.%Int.loc5_28.1 (%Int.fc6021.1) = class_element_access %return.param, element0
-// CHECK:STDOUT:     %.loc6_39.3: init @IntRange.Make.%Int.loc5_28.1 (%Int.fc6021.1) to %.loc6_39.2 = initialize_from %Copy.Op.call.loc6_22
+// CHECK:STDOUT:     %.loc6_39.3: init @IntRange.Make.%Int.loc5_28.1 (%Int.fc6021.1) to %.loc6_39.2 = in_place_init %Copy.Op.call.loc6_22
 // CHECK:STDOUT:     %impl.elem0.loc6_36: @IntRange.Make.%.loc6_22.2 (%.3676) = impl_witness_access constants.%Copy.lookup_impl_witness.7a8, element0 [symbolic = %impl.elem0.loc6_22.2 (constants.%impl.elem0.053)]
 // CHECK:STDOUT:     %bound_method.loc6_36.1: <bound method> = bound_method %end.ref, %impl.elem0.loc6_36
 // CHECK:STDOUT:     %specific_impl_fn.loc6_36: <specific function> = specific_impl_function %impl.elem0.loc6_36, @Copy.Op(constants.%Copy.facet.3b9) [symbolic = %specific_impl_fn.loc6_22.2 (constants.%specific_impl_fn.62b)]
 // CHECK:STDOUT:     %bound_method.loc6_36.2: <bound method> = bound_method %end.ref, %specific_impl_fn.loc6_36
 // CHECK:STDOUT:     %Copy.Op.call.loc6_36: init @IntRange.Make.%Int.loc5_28.1 (%Int.fc6021.1) = call %bound_method.loc6_36.2(%end.ref)
 // CHECK:STDOUT:     %.loc6_39.4: ref @IntRange.Make.%Int.loc5_28.1 (%Int.fc6021.1) = class_element_access %return.param, element1
-// CHECK:STDOUT:     %.loc6_39.5: init @IntRange.Make.%Int.loc5_28.1 (%Int.fc6021.1) to %.loc6_39.4 = initialize_from %Copy.Op.call.loc6_36
+// CHECK:STDOUT:     %.loc6_39.5: init @IntRange.Make.%Int.loc5_28.1 (%Int.fc6021.1) to %.loc6_39.4 = in_place_init %Copy.Op.call.loc6_36
 // CHECK:STDOUT:     %.loc6_39.6: init @IntRange.Make.%IntRange (%IntRange.265) to %return.param = class_init (%.loc6_39.3, %.loc6_39.5)
 // CHECK:STDOUT:     %.loc6_40: init @IntRange.Make.%IntRange (%IntRange.265) = converted %.loc6_39.1, %.loc6_39.6
 // CHECK:STDOUT:     return %.loc6_40 to %return.param
diff --git a/toolchain/check/testdata/function/builtin/call_from_operator.carbon b/toolchain/check/testdata/function/builtin/call_from_operator.carbon
index fc04dcc01699..eeb8ef4e8a26 100644
--- a/toolchain/check/testdata/function/builtin/call_from_operator.carbon
+++ b/toolchain/check/testdata/function/builtin/call_from_operator.carbon
@@ -1062,17 +1062,17 @@ var arr: array(i32, (1 as i32) + (2 as i32)) = (3, 4, (3 as i32) + (4 as i32));
 // CHECK:STDOUT:   %.loc4_78.2: init %i32.builtin = converted %int_3.loc4_49, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc4_78.1 [concrete = constants.%int_3.a0f]
 // CHECK:STDOUT:   %int_0: Core.IntLiteral = int_value 0 [concrete = constants.%int_0]
 // CHECK:STDOUT:   %.loc4_78.3: ref %i32.builtin = array_index file.%arr.var, %int_0
-// CHECK:STDOUT:   %.loc4_78.4: init %i32.builtin to %.loc4_78.3 = initialize_from %.loc4_78.2 [concrete = constants.%int_3.a0f]
+// CHECK:STDOUT:   %.loc4_78.4: init %i32.builtin to %.loc4_78.3 = in_place_init %.loc4_78.2 [concrete = constants.%int_3.a0f]
 // CHECK:STDOUT:   %impl.elem0.loc4_78.2: %.7de = impl_witness_access constants.%ImplicitAs.impl_witness.586, element0 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert]
 // CHECK:STDOUT:   %bound_method.loc4_78.2: <bound method> = bound_method %int_4.loc4_52, %impl.elem0.loc4_78.2 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.bound.762]
 // CHECK:STDOUT:   %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc4_78.2: init %i32.builtin = call %bound_method.loc4_78.2(%int_4.loc4_52) [concrete = constants.%int_4.4f1]
 // CHECK:STDOUT:   %.loc4_78.5: init %i32.builtin = converted %int_4.loc4_52, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc4_78.2 [concrete = constants.%int_4.4f1]
 // CHECK:STDOUT:   %int_1: Core.IntLiteral = int_value 1 [concrete = constants.%int_1.5b8]
 // CHECK:STDOUT:   %.loc4_78.6: ref %i32.builtin = array_index file.%arr.var, %int_1
-// CHECK:STDOUT:   %.loc4_78.7: init %i32.builtin to %.loc4_78.6 = initialize_from %.loc4_78.5 [concrete = constants.%int_4.4f1]
+// CHECK:STDOUT:   %.loc4_78.7: init %i32.builtin to %.loc4_78.6 = in_place_init %.loc4_78.5 [concrete = constants.%int_4.4f1]
 // CHECK:STDOUT:   %int_2: Core.IntLiteral = int_value 2 [concrete = constants.%int_2.ecc]
 // CHECK:STDOUT:   %.loc4_78.8: ref %i32.builtin = array_index file.%arr.var, %int_2
-// CHECK:STDOUT:   %.loc4_78.9: init %i32.builtin to %.loc4_78.8 = initialize_from %i32.builtin.as.AddWith.impl.Op.call [concrete = constants.%int_7]
+// CHECK:STDOUT:   %.loc4_78.9: init %i32.builtin to %.loc4_78.8 = in_place_init %i32.builtin.as.AddWith.impl.Op.call [concrete = constants.%int_7]
 // CHECK:STDOUT:   %.loc4_78.10: init %array_type to file.%arr.var = array_init (%.loc4_78.4, %.loc4_78.7, %.loc4_78.9) [concrete = constants.%array]
 // CHECK:STDOUT:   %.loc4_1: init %array_type = converted %.loc4_78.1, %.loc4_78.10 [concrete = constants.%array]
 // CHECK:STDOUT:   assign file.%arr.var, %.loc4_1
diff --git a/toolchain/check/testdata/function/builtin/import.carbon b/toolchain/check/testdata/function/builtin/import.carbon
index 6a7a9cc120af..75f22fe514de 100644
--- a/toolchain/check/testdata/function/builtin/import.carbon
+++ b/toolchain/check/testdata/function/builtin/import.carbon
@@ -287,13 +287,13 @@ var arr: array(i32, Core.AsIntLiteral(Core.TestAdd(Core.AsI32(1), Core.AsI32(2))
 // CHECK:STDOUT:   %.loc4_130.1: %tuple.type = tuple_literal (%AsI32.call.loc4_99, %AsI32.call.loc4_114, %AsI32.call.loc4_129) [concrete = constants.%tuple]
 // CHECK:STDOUT:   %int_0: Core.IntLiteral = int_value 0 [concrete = constants.%int_0]
 // CHECK:STDOUT:   %.loc4_130.2: ref %i32.builtin = array_index file.%arr.var, %int_0
-// CHECK:STDOUT:   %.loc4_130.3: init %i32.builtin to %.loc4_130.2 = initialize_from %AsI32.call.loc4_99 [concrete = constants.%int_1.f38]
+// CHECK:STDOUT:   %.loc4_130.3: init %i32.builtin to %.loc4_130.2 = in_place_init %AsI32.call.loc4_99 [concrete = constants.%int_1.f38]
 // CHECK:STDOUT:   %int_1.loc4_130: Core.IntLiteral = int_value 1 [concrete = constants.%int_1.5b8]
 // CHECK:STDOUT:   %.loc4_130.4: ref %i32.builtin = array_index file.%arr.var, %int_1.loc4_130
-// CHECK:STDOUT:   %.loc4_130.5: init %i32.builtin to %.loc4_130.4 = initialize_from %AsI32.call.loc4_114 [concrete = constants.%int_2.5a1]
+// CHECK:STDOUT:   %.loc4_130.5: init %i32.builtin to %.loc4_130.4 = in_place_init %AsI32.call.loc4_114 [concrete = constants.%int_2.5a1]
 // CHECK:STDOUT:   %int_2.loc4_130: Core.IntLiteral = int_value 2 [concrete = constants.%int_2.ecc]
 // CHECK:STDOUT:   %.loc4_130.6: ref %i32.builtin = array_index file.%arr.var, %int_2.loc4_130
-// CHECK:STDOUT:   %.loc4_130.7: init %i32.builtin to %.loc4_130.6 = initialize_from %AsI32.call.loc4_129 [concrete = constants.%int_3.a0f]
+// CHECK:STDOUT:   %.loc4_130.7: init %i32.builtin to %.loc4_130.6 = in_place_init %AsI32.call.loc4_129 [concrete = constants.%int_3.a0f]
 // CHECK:STDOUT:   %.loc4_130.8: init %array_type to file.%arr.var = array_init (%.loc4_130.3, %.loc4_130.5, %.loc4_130.7) [concrete = constants.%array]
 // CHECK:STDOUT:   %.loc4_1: init %array_type = converted %.loc4_130.1, %.loc4_130.8 [concrete = constants.%array]
 // CHECK:STDOUT:   assign file.%arr.var, %.loc4_1
diff --git a/toolchain/check/testdata/function/call/more_param_ir.carbon b/toolchain/check/testdata/function/call/more_param_ir.carbon
index 754417f9fb33..aecf6d6537ae 100644
--- a/toolchain/check/testdata/function/call/more_param_ir.carbon
+++ b/toolchain/check/testdata/function/call/more_param_ir.carbon
@@ -131,7 +131,7 @@ fn Main() {
 // CHECK:STDOUT:   %bound_method.loc18_22.2: <bound method> = bound_method %int_1, %specific_fn.loc18 [concrete = constants.%bound_method.38b]
 // CHECK:STDOUT:   %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc18: init %i32 = call %bound_method.loc18_22.2(%int_1) [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %.loc18_22.2: init %i32 = converted %int_1, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc18 [concrete = constants.%int_1.5d2]
-// CHECK:STDOUT:   %.loc18_22.3: init %tuple.type.a1c = tuple_init (%.loc18_22.2) [concrete = constants.%tuple.246]
+// CHECK:STDOUT:   %.loc18_22.3: init %tuple.type.a1c to %x.var = tuple_init (%.loc18_22.2) [concrete = constants.%tuple.246]
 // CHECK:STDOUT:   %.loc18_3: init %tuple.type.a1c = converted %.loc18_22.1, %.loc18_22.3 [concrete = constants.%tuple.246]
 // CHECK:STDOUT:   assign %x.var, %.loc18_3
 // CHECK:STDOUT:   %.loc18_15.1: type = splice_block %.loc18_15.3 [concrete = constants.%tuple.type.a1c] {
diff --git a/toolchain/check/testdata/generic/local.carbon b/toolchain/check/testdata/generic/local.carbon
index 408068dea0f2..21602ee4055a 100644
--- a/toolchain/check/testdata/generic/local.carbon
+++ b/toolchain/check/testdata/generic/local.carbon
@@ -169,7 +169,7 @@ class C(C:! type) {
 // CHECK:STDOUT:   %Core.IntLiteral.as.ImplicitAs.impl.Convert.call: init %i32 = call %bound_method.loc8_26.2(%int_1) [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %.loc8_26.2: init %i32 = converted %int_1, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %.loc8_26.3: ref %i32 = class_element_access %v.var, element0
-// CHECK:STDOUT:   %.loc8_26.4: init %i32 to %.loc8_26.3 = initialize_from %.loc8_26.2 [concrete = constants.%int_1.5d2]
+// CHECK:STDOUT:   %.loc8_26.4: init %i32 to %.loc8_26.3 = in_place_init %.loc8_26.2 [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %.loc8_26.5: init %C.d45 to %v.var = class_init (%.loc8_26.4) [concrete = constants.%C.val]
 // CHECK:STDOUT:   %.loc8_3: init %C.d45 = converted %.loc8_26.1, %.loc8_26.5 [concrete = constants.%C.val]
 // CHECK:STDOUT:   assign %v.var, %.loc8_3
diff --git a/toolchain/check/testdata/if_expr/basic.carbon b/toolchain/check/testdata/if_expr/basic.carbon
index 9b59568582ad..7c6b59d92a5d 100644
--- a/toolchain/check/testdata/if_expr/basic.carbon
+++ b/toolchain/check/testdata/if_expr/basic.carbon
@@ -152,7 +152,7 @@ fn F(b: bool, n: i32, m: i32) -> i32 {
 // CHECK:STDOUT:   %.loc16_29.2: init %i32 = converted %int_0.loc16_27, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call [concrete = constants.%int_0.6a9]
 // CHECK:STDOUT:   %int_0.loc16_29: Core.IntLiteral = int_value 0 [concrete = constants.%int_0.5c6]
 // CHECK:STDOUT:   %.loc16_29.3: ref %i32 = array_index %x.var, %int_0.loc16_29
-// CHECK:STDOUT:   %.loc16_29.4: init %i32 to %.loc16_29.3 = initialize_from %.loc16_29.2 [concrete = constants.%int_0.6a9]
+// CHECK:STDOUT:   %.loc16_29.4: init %i32 to %.loc16_29.3 = in_place_init %.loc16_29.2 [concrete = constants.%int_0.6a9]
 // CHECK:STDOUT:   %.loc16_29.5: init %array_type to %x.var = array_init (%.loc16_29.4) [concrete = constants.%array]
 // CHECK:STDOUT:   %.loc16_3: init %array_type = converted %.loc16_29.1, %.loc16_29.5 [concrete = constants.%array]
 // CHECK:STDOUT:   assign %x.var, %.loc16_3
diff --git a/toolchain/check/testdata/if_expr/struct.carbon b/toolchain/check/testdata/if_expr/struct.carbon
index 58bdda01ebe3..2756853eae73 100644
--- a/toolchain/check/testdata/if_expr/struct.carbon
+++ b/toolchain/check/testdata/if_expr/struct.carbon
@@ -136,7 +136,7 @@ fn F(cond: bool) {
 // CHECK:STDOUT:   %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc18_46.1: init %i32 = call %bound_method.loc18_46.2(%int_1) [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %.loc18_46.2: init %i32 = converted %int_1, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc18_46.1 [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %.loc18_46.3: ref %i32 = struct_access %a.var, element0
-// CHECK:STDOUT:   %.loc18_46.4: init %i32 to %.loc18_46.3 = initialize_from %.loc18_46.2 [concrete = constants.%int_1.5d2]
+// CHECK:STDOUT:   %.loc18_46.4: init %i32 to %.loc18_46.3 = in_place_init %.loc18_46.2 [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %impl.elem0.loc18_46.2: %.863 = impl_witness_access constants.%ImplicitAs.impl_witness.6bc, element0 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.0b5]
 // CHECK:STDOUT:   %bound_method.loc18_46.3: <bound method> = bound_method %int_2, %impl.elem0.loc18_46.2 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.bound.4e5]
 // CHECK:STDOUT:   %specific_fn.loc18_46.2: <specific function> = specific_function %impl.elem0.loc18_46.2, @Core.IntLiteral.as.ImplicitAs.impl.Convert(constants.%int_32) [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.specific_fn]
@@ -144,7 +144,7 @@ fn F(cond: bool) {
 // CHECK:STDOUT:   %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc18_46.2: init %i32 = call %bound_method.loc18_46.4(%int_2) [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %.loc18_46.5: init %i32 = converted %int_2, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc18_46.2 [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %.loc18_46.6: ref %i32 = struct_access %a.var, element1
-// CHECK:STDOUT:   %.loc18_46.7: init %i32 to %.loc18_46.6 = initialize_from %.loc18_46.5 [concrete = constants.%int_2.ef8]
+// CHECK:STDOUT:   %.loc18_46.7: init %i32 to %.loc18_46.6 = in_place_init %.loc18_46.5 [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %.loc18_46.8: init %struct_type.a.b.501 to %a.var = struct_init (%.loc18_46.4, %.loc18_46.7) [concrete = constants.%struct.ed5]
 // CHECK:STDOUT:   %.loc18_3: init %struct_type.a.b.501 = converted %.loc18_46.1, %.loc18_46.8 [concrete = constants.%struct.ed5]
 // CHECK:STDOUT:   assign %a.var, %.loc18_3
diff --git a/toolchain/check/testdata/impl/extend_impl_generic.carbon b/toolchain/check/testdata/impl/extend_impl_generic.carbon
index d9ca9d2d8c44..3f1b3e38a623 100644
--- a/toolchain/check/testdata/impl/extend_impl_generic.carbon
+++ b/toolchain/check/testdata/impl/extend_impl_generic.carbon
@@ -284,7 +284,7 @@ class X(U:! type) {
 // CHECK:STDOUT:   %Core.IntLiteral.as.ImplicitAs.impl.Convert.call: init %i32 = call %bound_method.loc15_21.2(%int_2) [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %.loc15_21.2: init %i32 = converted %int_2, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %.loc15_21.3: ref %i32 = class_element_access %return.param, element0
-// CHECK:STDOUT:   %.loc15_21.4: init %i32 to %.loc15_21.3 = initialize_from %.loc15_21.2 [concrete = constants.%int_2.ef8]
+// CHECK:STDOUT:   %.loc15_21.4: init %i32 to %.loc15_21.3 = in_place_init %.loc15_21.2 [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %.loc15_21.5: init %Param to %return.param = class_init (%.loc15_21.4) [concrete = constants.%Param.val]
 // CHECK:STDOUT:   %.loc15_22: init %Param = converted %.loc15_21.1, %.loc15_21.5 [concrete = constants.%Param.val]
 // CHECK:STDOUT:   return %.loc15_22 to %return.param
diff --git a/toolchain/check/testdata/impl/impl_thunk.carbon b/toolchain/check/testdata/impl/impl_thunk.carbon
index 6b26f4da8634..d6ab3f39acd3 100644
--- a/toolchain/check/testdata/impl/impl_thunk.carbon
+++ b/toolchain/check/testdata/impl/impl_thunk.carbon
@@ -399,11 +399,11 @@ impl () as I({}) {
 // CHECK:STDOUT:   %.loc10_48.2: ref %struct_type.d.c.b36 = temporary %.loc10_48.1, %empty_tuple.type.as.I.impl.F.call
 // CHECK:STDOUT:   %.loc10_48.3: ref %empty_tuple.type = struct_access %.loc10_48.2, element1
 // CHECK:STDOUT:   %.loc10_48.4: ref %empty_tuple.type = struct_access %return.param, element1
-// CHECK:STDOUT:   %.loc10_48.5: init %empty_tuple.type to %.loc10_48.4 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc10_48.5: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc10_48.6: init %empty_tuple.type = converted %.loc10_48.3, %.loc10_48.5 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc10_48.7: ref %empty_struct_type = struct_access %.loc10_48.2, element0
 // CHECK:STDOUT:   %.loc10_48.8: ref %empty_struct_type = struct_access %return.param, element0
-// CHECK:STDOUT:   %.loc10_48.9: init %empty_struct_type to %.loc10_48.8 = struct_init () [concrete = constants.%empty_struct]
+// CHECK:STDOUT:   %.loc10_48.9: init %empty_struct_type = struct_init () [concrete = constants.%empty_struct]
 // CHECK:STDOUT:   %.loc10_48.10: init %empty_struct_type = converted %.loc10_48.7, %.loc10_48.9 [concrete = constants.%empty_struct]
 // CHECK:STDOUT:   %.loc10_48.11: init %struct_type.c.d.15a to %return.param = struct_init (%.loc10_48.6, %.loc10_48.10) [concrete = constants.%struct]
 // CHECK:STDOUT:   %.loc10_48.12: init %struct_type.c.d.15a = converted %empty_tuple.type.as.I.impl.F.call, %.loc10_48.11 [concrete = constants.%struct]
@@ -1217,11 +1217,11 @@ impl () as I({}) {
 // CHECK:STDOUT:   %.loc10_29.2: ref %struct_type.b.a.1b0 = temporary %.loc10_29.1, %empty_tuple.type.as.I.impl.F.call
 // CHECK:STDOUT:   %.loc10_29.3: ref %empty_struct_type = struct_access %.loc10_29.2, element1
 // CHECK:STDOUT:   %.loc10_29.4: ref %empty_struct_type = struct_access %return.param, element1
-// CHECK:STDOUT:   %.loc10_29.5: init %empty_struct_type to %.loc10_29.4 = struct_init () [concrete = constants.%empty_struct]
+// CHECK:STDOUT:   %.loc10_29.5: init %empty_struct_type = struct_init () [concrete = constants.%empty_struct]
 // CHECK:STDOUT:   %.loc10_29.6: init %empty_struct_type = converted %.loc10_29.3, %.loc10_29.5 [concrete = constants.%empty_struct]
 // CHECK:STDOUT:   %.loc10_29.7: ref %empty_struct_type = struct_access %.loc10_29.2, element0
 // CHECK:STDOUT:   %.loc10_29.8: ref %empty_struct_type = struct_access %return.param, element0
-// CHECK:STDOUT:   %.loc10_29.9: init %empty_struct_type to %.loc10_29.8 = struct_init () [concrete = constants.%empty_struct]
+// CHECK:STDOUT:   %.loc10_29.9: init %empty_struct_type = struct_init () [concrete = constants.%empty_struct]
 // CHECK:STDOUT:   %.loc10_29.10: init %empty_struct_type = converted %.loc10_29.7, %.loc10_29.9 [concrete = constants.%empty_struct]
 // CHECK:STDOUT:   %.loc10_29.11: init %struct_type.a.b.f95 to %return.param = struct_init (%.loc10_29.6, %.loc10_29.10) [concrete = constants.%struct]
 // CHECK:STDOUT:   %.loc10_29.12: init %struct_type.a.b.f95 = converted %empty_tuple.type.as.I.impl.F.call, %.loc10_29.11 [concrete = constants.%struct]
diff --git a/toolchain/check/testdata/impl/use_assoc_entity.carbon b/toolchain/check/testdata/impl/use_assoc_entity.carbon
index a138556f5926..f51cc8e86135 100644
--- a/toolchain/check/testdata/impl/use_assoc_entity.carbon
+++ b/toolchain/check/testdata/impl/use_assoc_entity.carbon
@@ -4189,13 +4189,13 @@ fn F() {
 // CHECK:STDOUT:   %bool.as.Copy.impl.Op.call.loc9_50: init bool = call %bound_method.loc9_50(%true) [concrete = constants.%true]
 // CHECK:STDOUT:   %int_0: Core.IntLiteral = int_value 0 [concrete = constants.%int_0]
 // CHECK:STDOUT:   %.loc9_61.2: ref bool = array_index %return.param, %int_0
-// CHECK:STDOUT:   %.loc9_61.3: init bool to %.loc9_61.2 = initialize_from %bool.as.Copy.impl.Op.call.loc9_50 [concrete = constants.%true]
+// CHECK:STDOUT:   %.loc9_61.3: init bool to %.loc9_61.2 = in_place_init %bool.as.Copy.impl.Op.call.loc9_50 [concrete = constants.%true]
 // CHECK:STDOUT:   %impl.elem0.loc9_56: %.56b = impl_witness_access constants.%Copy.impl_witness.348, element0 [concrete = constants.%bool.as.Copy.impl.Op]
 // CHECK:STDOUT:   %bound_method.loc9_56: <bound method> = bound_method %false, %impl.elem0.loc9_56 [concrete = constants.%bool.as.Copy.impl.Op.bound.082]
 // CHECK:STDOUT:   %bool.as.Copy.impl.Op.call.loc9_56: init bool = call %bound_method.loc9_56(%false) [concrete = constants.%false]
 // CHECK:STDOUT:   %int_1: Core.IntLiteral = int_value 1 [concrete = constants.%int_1]
 // CHECK:STDOUT:   %.loc9_61.4: ref bool = array_index %return.param, %int_1
-// CHECK:STDOUT:   %.loc9_61.5: init bool to %.loc9_61.4 = initialize_from %bool.as.Copy.impl.Op.call.loc9_56 [concrete = constants.%false]
+// CHECK:STDOUT:   %.loc9_61.5: init bool to %.loc9_61.4 = in_place_init %bool.as.Copy.impl.Op.call.loc9_56 [concrete = constants.%false]
 // CHECK:STDOUT:   %.loc9_61.6: init %array_type.c9b to %return.param = array_init (%.loc9_61.3, %.loc9_61.5) [concrete = constants.%array]
 // CHECK:STDOUT:   %.loc9_62: init %array_type.c9b = converted %.loc9_61.1, %.loc9_61.6 [concrete = constants.%array]
 // CHECK:STDOUT:   return %.loc9_62 to %return.param
diff --git a/toolchain/check/testdata/index/array_element_access.carbon b/toolchain/check/testdata/index/array_element_access.carbon
index beac8ab35210..c0157ac6f703 100644
--- a/toolchain/check/testdata/index/array_element_access.carbon
+++ b/toolchain/check/testdata/index/array_element_access.carbon
@@ -156,7 +156,7 @@ var d: i32 = a[b];
 // CHECK:STDOUT:   %.loc15_31.2: init %i32 = converted %int_12, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc15_31.1 [concrete = constants.%int_12.1e1]
 // CHECK:STDOUT:   %int_0.loc15: Core.IntLiteral = int_value 0 [concrete = constants.%int_0.5c6]
 // CHECK:STDOUT:   %.loc15_31.3: ref %i32 = array_index file.%a.var, %int_0.loc15
-// CHECK:STDOUT:   %.loc15_31.4: init %i32 to %.loc15_31.3 = initialize_from %.loc15_31.2 [concrete = constants.%int_12.1e1]
+// CHECK:STDOUT:   %.loc15_31.4: init %i32 to %.loc15_31.3 = in_place_init %.loc15_31.2 [concrete = constants.%int_12.1e1]
 // CHECK:STDOUT:   %impl.elem0.loc15_31.2: %.863 = impl_witness_access constants.%ImplicitAs.impl_witness.6bc, element0 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.0b5]
 // CHECK:STDOUT:   %bound_method.loc15_31.3: <bound method> = bound_method %int_24, %impl.elem0.loc15_31.2 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.bound.3b2]
 // CHECK:STDOUT:   %specific_fn.loc15_31.2: <specific function> = specific_function %impl.elem0.loc15_31.2, @Core.IntLiteral.as.ImplicitAs.impl.Convert(constants.%int_32) [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.specific_fn]
@@ -165,7 +165,7 @@ var d: i32 = a[b];
 // CHECK:STDOUT:   %.loc15_31.5: init %i32 = converted %int_24, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc15_31.2 [concrete = constants.%int_24.365]
 // CHECK:STDOUT:   %int_1.loc15: Core.IntLiteral = int_value 1 [concrete = constants.%int_1.5b8]
 // CHECK:STDOUT:   %.loc15_31.6: ref %i32 = array_index file.%a.var, %int_1.loc15
-// CHECK:STDOUT:   %.loc15_31.7: init %i32 to %.loc15_31.6 = initialize_from %.loc15_31.5 [concrete = constants.%int_24.365]
+// CHECK:STDOUT:   %.loc15_31.7: init %i32 to %.loc15_31.6 = in_place_init %.loc15_31.5 [concrete = constants.%int_24.365]
 // CHECK:STDOUT:   %.loc15_31.8: init %array_type to file.%a.var = array_init (%.loc15_31.4, %.loc15_31.7) [concrete = constants.%array]
 // CHECK:STDOUT:   %.loc15_1: init %array_type = converted %.loc15_31.1, %.loc15_31.8 [concrete = constants.%array]
 // CHECK:STDOUT:   assign file.%a.var, %.loc15_1
diff --git a/toolchain/check/testdata/index/expr_category.carbon b/toolchain/check/testdata/index/expr_category.carbon
index 327dcbaa53f7..ddb744cc3a4d 100644
--- a/toolchain/check/testdata/index/expr_category.carbon
+++ b/toolchain/check/testdata/index/expr_category.carbon
@@ -193,7 +193,7 @@ fn ValueBinding(b: array(i32, 3)) {
 // CHECK:STDOUT:   %.loc18_34.2: init %i32 = converted %int_1.loc18_27, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc18_34.1 [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %int_0.loc18: Core.IntLiteral = int_value 0 [concrete = constants.%int_0.5c6]
 // CHECK:STDOUT:   %.loc18_34.3: ref %i32 = array_index %a.var, %int_0.loc18
-// CHECK:STDOUT:   %.loc18_34.4: init %i32 to %.loc18_34.3 = initialize_from %.loc18_34.2 [concrete = constants.%int_1.5d2]
+// CHECK:STDOUT:   %.loc18_34.4: init %i32 to %.loc18_34.3 = in_place_init %.loc18_34.2 [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %impl.elem0.loc18_34.2: %.863 = impl_witness_access constants.%ImplicitAs.impl_witness.6bc, element0 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.0b5]
 // CHECK:STDOUT:   %bound_method.loc18_34.3: <bound method> = bound_method %int_2.loc18_30, %impl.elem0.loc18_34.2 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.bound.4e5]
 // CHECK:STDOUT:   %specific_fn.loc18_34.2: <specific function> = specific_function %impl.elem0.loc18_34.2, @Core.IntLiteral.as.ImplicitAs.impl.Convert(constants.%int_32) [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.specific_fn]
@@ -202,7 +202,7 @@ fn ValueBinding(b: array(i32, 3)) {
 // CHECK:STDOUT:   %.loc18_34.5: init %i32 = converted %int_2.loc18_30, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc18_34.2 [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %int_1.loc18_34: Core.IntLiteral = int_value 1 [concrete = constants.%int_1.5b8]
 // CHECK:STDOUT:   %.loc18_34.6: ref %i32 = array_index %a.var, %int_1.loc18_34
-// CHECK:STDOUT:   %.loc18_34.7: init %i32 to %.loc18_34.6 = initialize_from %.loc18_34.5 [concrete = constants.%int_2.ef8]
+// CHECK:STDOUT:   %.loc18_34.7: init %i32 to %.loc18_34.6 = in_place_init %.loc18_34.5 [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %impl.elem0.loc18_34.3: %.863 = impl_witness_access constants.%ImplicitAs.impl_witness.6bc, element0 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.0b5]
 // CHECK:STDOUT:   %bound_method.loc18_34.5: <bound method> = bound_method %int_3.loc18_33, %impl.elem0.loc18_34.3 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.bound.061]
 // CHECK:STDOUT:   %specific_fn.loc18_34.3: <specific function> = specific_function %impl.elem0.loc18_34.3, @Core.IntLiteral.as.ImplicitAs.impl.Convert(constants.%int_32) [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.specific_fn]
@@ -211,7 +211,7 @@ fn ValueBinding(b: array(i32, 3)) {
 // CHECK:STDOUT:   %.loc18_34.8: init %i32 = converted %int_3.loc18_33, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc18_34.3 [concrete = constants.%int_3.822]
 // CHECK:STDOUT:   %int_2.loc18_34: Core.IntLiteral = int_value 2 [concrete = constants.%int_2.ecc]
 // CHECK:STDOUT:   %.loc18_34.9: ref %i32 = array_index %a.var, %int_2.loc18_34
-// CHECK:STDOUT:   %.loc18_34.10: init %i32 to %.loc18_34.9 = initialize_from %.loc18_34.8 [concrete = constants.%int_3.822]
+// CHECK:STDOUT:   %.loc18_34.10: init %i32 to %.loc18_34.9 = in_place_init %.loc18_34.8 [concrete = constants.%int_3.822]
 // CHECK:STDOUT:   %.loc18_34.11: init %array_type to %a.var = array_init (%.loc18_34.4, %.loc18_34.7, %.loc18_34.10) [concrete = constants.%array]
 // CHECK:STDOUT:   %.loc18_3: init %array_type = converted %.loc18_34.1, %.loc18_34.11 [concrete = constants.%array]
 // CHECK:STDOUT:   assign %a.var, %.loc18_3
@@ -302,7 +302,7 @@ fn ValueBinding(b: array(i32, 3)) {
 // CHECK:STDOUT:   %.loc26_34.2: init %i32 = converted %int_1.loc26_27, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc26_34.1 [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %int_0.loc26: Core.IntLiteral = int_value 0 [concrete = constants.%int_0.5c6]
 // CHECK:STDOUT:   %.loc26_34.3: ref %i32 = array_index %a.var, %int_0.loc26
-// CHECK:STDOUT:   %.loc26_34.4: init %i32 to %.loc26_34.3 = initialize_from %.loc26_34.2 [concrete = constants.%int_1.5d2]
+// CHECK:STDOUT:   %.loc26_34.4: init %i32 to %.loc26_34.3 = in_place_init %.loc26_34.2 [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %impl.elem0.loc26_34.2: %.863 = impl_witness_access constants.%ImplicitAs.impl_witness.6bc, element0 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.0b5]
 // CHECK:STDOUT:   %bound_method.loc26_34.3: <bound method> = bound_method %int_2.loc26_30, %impl.elem0.loc26_34.2 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.bound.4e5]
 // CHECK:STDOUT:   %specific_fn.loc26_34.2: <specific function> = specific_function %impl.elem0.loc26_34.2, @Core.IntLiteral.as.ImplicitAs.impl.Convert(constants.%int_32) [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.specific_fn]
@@ -311,7 +311,7 @@ fn ValueBinding(b: array(i32, 3)) {
 // CHECK:STDOUT:   %.loc26_34.5: init %i32 = converted %int_2.loc26_30, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc26_34.2 [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %int_1.loc26_34: Core.IntLiteral = int_value 1 [concrete = constants.%int_1.5b8]
 // CHECK:STDOUT:   %.loc26_34.6: ref %i32 = array_index %a.var, %int_1.loc26_34
-// CHECK:STDOUT:   %.loc26_34.7: init %i32 to %.loc26_34.6 = initialize_from %.loc26_34.5 [concrete = constants.%int_2.ef8]
+// CHECK:STDOUT:   %.loc26_34.7: init %i32 to %.loc26_34.6 = in_place_init %.loc26_34.5 [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %impl.elem0.loc26_34.3: %.863 = impl_witness_access constants.%ImplicitAs.impl_witness.6bc, element0 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.0b5]
 // CHECK:STDOUT:   %bound_method.loc26_34.5: <bound method> = bound_method %int_3.loc26_33, %impl.elem0.loc26_34.3 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.bound.061]
 // CHECK:STDOUT:   %specific_fn.loc26_34.3: <specific function> = specific_function %impl.elem0.loc26_34.3, @Core.IntLiteral.as.ImplicitAs.impl.Convert(constants.%int_32) [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.specific_fn]
@@ -320,7 +320,7 @@ fn ValueBinding(b: array(i32, 3)) {
 // CHECK:STDOUT:   %.loc26_34.8: init %i32 = converted %int_3.loc26_33, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc26_34.3 [concrete = constants.%int_3.822]
 // CHECK:STDOUT:   %int_2.loc26_34: Core.IntLiteral = int_value 2 [concrete = constants.%int_2.ecc]
 // CHECK:STDOUT:   %.loc26_34.9: ref %i32 = array_index %a.var, %int_2.loc26_34
-// CHECK:STDOUT:   %.loc26_34.10: init %i32 to %.loc26_34.9 = initialize_from %.loc26_34.8 [concrete = constants.%int_3.822]
+// CHECK:STDOUT:   %.loc26_34.10: init %i32 to %.loc26_34.9 = in_place_init %.loc26_34.8 [concrete = constants.%int_3.822]
 // CHECK:STDOUT:   %.loc26_34.11: init %array_type to %a.var = array_init (%.loc26_34.4, %.loc26_34.7, %.loc26_34.10) [concrete = constants.%array]
 // CHECK:STDOUT:   %.loc26_3: init %array_type = converted %.loc26_34.1, %.loc26_34.11 [concrete = constants.%array]
 // CHECK:STDOUT:   assign %a.var, %.loc26_3
diff --git a/toolchain/check/testdata/index/fail_array_large_index.carbon b/toolchain/check/testdata/index/fail_array_large_index.carbon
index 93bcba496e5d..bfbc8a785d24 100644
--- a/toolchain/check/testdata/index/fail_array_large_index.carbon
+++ b/toolchain/check/testdata/index/fail_array_large_index.carbon
@@ -149,7 +149,7 @@ var c: i32 = a[0x7FFF_FFFF];
 // CHECK:STDOUT:   %.loc15_28.2: init %i32 = converted %int_12, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc15 [concrete = constants.%int_12.1e1]
 // CHECK:STDOUT:   %int_0: Core.IntLiteral = int_value 0 [concrete = constants.%int_0]
 // CHECK:STDOUT:   %.loc15_28.3: ref %i32 = array_index file.%a.var, %int_0
-// CHECK:STDOUT:   %.loc15_28.4: init %i32 to %.loc15_28.3 = initialize_from %.loc15_28.2 [concrete = constants.%int_12.1e1]
+// CHECK:STDOUT:   %.loc15_28.4: init %i32 to %.loc15_28.3 = in_place_init %.loc15_28.2 [concrete = constants.%int_12.1e1]
 // CHECK:STDOUT:   %.loc15_28.5: init %array_type to file.%a.var = array_init (%.loc15_28.4) [concrete = constants.%array]
 // CHECK:STDOUT:   %.loc15_1: init %array_type = converted %.loc15_28.1, %.loc15_28.5 [concrete = constants.%array]
 // CHECK:STDOUT:   assign file.%a.var, %.loc15_1
diff --git a/toolchain/check/testdata/index/fail_array_non_int_indexing.carbon b/toolchain/check/testdata/index/fail_array_non_int_indexing.carbon
index a78b85917bd5..bf9361930183 100644
--- a/toolchain/check/testdata/index/fail_array_non_int_indexing.carbon
+++ b/toolchain/check/testdata/index/fail_array_non_int_indexing.carbon
@@ -128,7 +128,7 @@ var b: i32 = a[2.6];
 // CHECK:STDOUT:   %.loc15_28.2: init %i32 = converted %int_12, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call [concrete = constants.%int_12.1e1]
 // CHECK:STDOUT:   %int_0: Core.IntLiteral = int_value 0 [concrete = constants.%int_0]
 // CHECK:STDOUT:   %.loc15_28.3: ref %i32 = array_index file.%a.var, %int_0
-// CHECK:STDOUT:   %.loc15_28.4: init %i32 to %.loc15_28.3 = initialize_from %.loc15_28.2 [concrete = constants.%int_12.1e1]
+// CHECK:STDOUT:   %.loc15_28.4: init %i32 to %.loc15_28.3 = in_place_init %.loc15_28.2 [concrete = constants.%int_12.1e1]
 // CHECK:STDOUT:   %.loc15_28.5: init %array_type to file.%a.var = array_init (%.loc15_28.4) [concrete = constants.%array]
 // CHECK:STDOUT:   %.loc15_1: init %array_type = converted %.loc15_28.1, %.loc15_28.5 [concrete = constants.%array]
 // CHECK:STDOUT:   assign file.%a.var, %.loc15_1
diff --git a/toolchain/check/testdata/index/fail_array_out_of_bound_access.carbon b/toolchain/check/testdata/index/fail_array_out_of_bound_access.carbon
index 697f921ec625..93f46331ff91 100644
--- a/toolchain/check/testdata/index/fail_array_out_of_bound_access.carbon
+++ b/toolchain/check/testdata/index/fail_array_out_of_bound_access.carbon
@@ -127,7 +127,7 @@ var b: i32 = a[1];
 // CHECK:STDOUT:   %.loc15_28.2: init %i32 = converted %int_12, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc15 [concrete = constants.%int_12.1e1]
 // CHECK:STDOUT:   %int_0: Core.IntLiteral = int_value 0 [concrete = constants.%int_0]
 // CHECK:STDOUT:   %.loc15_28.3: ref %i32 = array_index file.%a.var, %int_0
-// CHECK:STDOUT:   %.loc15_28.4: init %i32 to %.loc15_28.3 = initialize_from %.loc15_28.2 [concrete = constants.%int_12.1e1]
+// CHECK:STDOUT:   %.loc15_28.4: init %i32 to %.loc15_28.3 = in_place_init %.loc15_28.2 [concrete = constants.%int_12.1e1]
 // CHECK:STDOUT:   %.loc15_28.5: init %array_type to file.%a.var = array_init (%.loc15_28.4) [concrete = constants.%array]
 // CHECK:STDOUT:   %.loc15_1: init %array_type = converted %.loc15_28.1, %.loc15_28.5 [concrete = constants.%array]
 // CHECK:STDOUT:   assign file.%a.var, %.loc15_1
diff --git a/toolchain/check/testdata/index/fail_negative_indexing.carbon b/toolchain/check/testdata/index/fail_negative_indexing.carbon
index 44cd683cbaca..681a3637dc51 100644
--- a/toolchain/check/testdata/index/fail_negative_indexing.carbon
+++ b/toolchain/check/testdata/index/fail_negative_indexing.carbon
@@ -145,7 +145,7 @@ var d: i32 = c[-10];
 // CHECK:STDOUT:   %.loc15_31.2: init %i32 = converted %int_42.loc15_25, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc15_31.1 [concrete = constants.%int_42.c68]
 // CHECK:STDOUT:   %int_0: Core.IntLiteral = int_value 0 [concrete = constants.%int_0]
 // CHECK:STDOUT:   %.loc15_31.3: ref %i32 = array_index file.%c.var, %int_0
-// CHECK:STDOUT:   %.loc15_31.4: init %i32 to %.loc15_31.3 = initialize_from %.loc15_31.2 [concrete = constants.%int_42.c68]
+// CHECK:STDOUT:   %.loc15_31.4: init %i32 to %.loc15_31.3 = in_place_init %.loc15_31.2 [concrete = constants.%int_42.c68]
 // CHECK:STDOUT:   %impl.elem0.loc15_31.2: %.863 = impl_witness_access constants.%ImplicitAs.impl_witness.6bc, element0 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.0b5]
 // CHECK:STDOUT:   %bound_method.loc15_31.3: <bound method> = bound_method %int_42.loc15_29, %impl.elem0.loc15_31.2 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.bound.c83]
 // CHECK:STDOUT:   %specific_fn.loc15_31.2: <specific function> = specific_function %impl.elem0.loc15_31.2, @Core.IntLiteral.as.ImplicitAs.impl.Convert(constants.%int_32) [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.specific_fn]
@@ -154,7 +154,7 @@ var d: i32 = c[-10];
 // CHECK:STDOUT:   %.loc15_31.5: init %i32 = converted %int_42.loc15_29, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc15_31.2 [concrete = constants.%int_42.c68]
 // CHECK:STDOUT:   %int_1: Core.IntLiteral = int_value 1 [concrete = constants.%int_1]
 // CHECK:STDOUT:   %.loc15_31.6: ref %i32 = array_index file.%c.var, %int_1
-// CHECK:STDOUT:   %.loc15_31.7: init %i32 to %.loc15_31.6 = initialize_from %.loc15_31.5 [concrete = constants.%int_42.c68]
+// CHECK:STDOUT:   %.loc15_31.7: init %i32 to %.loc15_31.6 = in_place_init %.loc15_31.5 [concrete = constants.%int_42.c68]
 // CHECK:STDOUT:   %.loc15_31.8: init %array_type to file.%c.var = array_init (%.loc15_31.4, %.loc15_31.7) [concrete = constants.%array]
 // CHECK:STDOUT:   %.loc15_1: init %array_type = converted %.loc15_31.1, %.loc15_31.8 [concrete = constants.%array]
 // CHECK:STDOUT:   assign file.%c.var, %.loc15_1
diff --git a/toolchain/check/testdata/interface/generic_method.carbon b/toolchain/check/testdata/interface/generic_method.carbon
index 0e40a7ca84bf..1307266edb70 100644
--- a/toolchain/check/testdata/interface/generic_method.carbon
+++ b/toolchain/check/testdata/interface/generic_method.carbon
@@ -426,7 +426,7 @@ fn CallIndirect() {
 // CHECK:STDOUT:     %bound_method.loc17_21.2: <bound method> = bound_method %u.ref, %specific_impl_fn.loc17_21.1
 // CHECK:STDOUT:     %Copy.Op.call: init @Y.as.A.impl.F.%ptr.loc16_22.1 (%ptr.e8f8f9.1) = call %bound_method.loc17_21.2(%u.ref)
 // CHECK:STDOUT:     %tuple.elem2: ref @Y.as.A.impl.F.%ptr.loc16_22.1 (%ptr.e8f8f9.1) = tuple_access %return.param, element2
-// CHECK:STDOUT:     %.loc17_22.4: init @Y.as.A.impl.F.%ptr.loc16_22.1 (%ptr.e8f8f9.1) to %tuple.elem2 = initialize_from %Copy.Op.call
+// CHECK:STDOUT:     %.loc17_22.4: init @Y.as.A.impl.F.%ptr.loc16_22.1 (%ptr.e8f8f9.1) to %tuple.elem2 = in_place_init %Copy.Op.call
 // CHECK:STDOUT:     %.loc17_22.5: init @Y.as.A.impl.F.%tuple.type.loc16 (%tuple.type.244) to %return.param = tuple_init (%.loc17_22.2, %.loc17_22.3, %.loc17_22.4)
 // CHECK:STDOUT:     %.loc17_23: init @Y.as.A.impl.F.%tuple.type.loc16 (%tuple.type.244) = converted %.loc17_22.1, %.loc17_22.5
 // CHECK:STDOUT:     return %.loc17_23 to %return.param
diff --git a/toolchain/check/testdata/interop/cpp/builtins.llp64.carbon b/toolchain/check/testdata/interop/cpp/builtins.llp64.carbon
index 259679ac1b3c..35946a2c0048 100644
--- a/toolchain/check/testdata/interop/cpp/builtins.llp64.carbon
+++ b/toolchain/check/testdata/interop/cpp/builtins.llp64.carbon
@@ -841,7 +841,7 @@ fn CopyUnsignedLong() {
 // CHECK:STDOUT:   %.loc11_48.2: init %f32.97e = converted %float, %Core.FloatLiteral.as.ImplicitAs.impl.Convert.call [concrete = constants.%float.e3b]
 // CHECK:STDOUT:   %int_0: Core.IntLiteral = int_value 0 [concrete = constants.%int_0]
 // CHECK:STDOUT:   %.loc11_48.3: ref %f32.97e = array_index %a.var, %int_0
-// CHECK:STDOUT:   %.loc11_48.4: init %f32.97e to %.loc11_48.3 = initialize_from %.loc11_48.2 [concrete = constants.%float.e3b]
+// CHECK:STDOUT:   %.loc11_48.4: init %f32.97e to %.loc11_48.3 = in_place_init %.loc11_48.2 [concrete = constants.%float.e3b]
 // CHECK:STDOUT:   %.loc11_48.5: init %array_type to %a.var = array_init (%.loc11_48.4) [concrete = constants.%array]
 // CHECK:STDOUT:   %.loc11_3: init %array_type = converted %.loc11_48.1, %.loc11_48.5 [concrete = constants.%array]
 // CHECK:STDOUT:   assign %a.var, %.loc11_3
@@ -1007,7 +1007,7 @@ fn CopyUnsignedLong() {
 // CHECK:STDOUT:   %.loc11_57.2: init %f32.97e = converted %float, %Core.FloatLiteral.as.ImplicitAs.impl.Convert.call [concrete = constants.%float.e3b]
 // CHECK:STDOUT:   %int_0: Core.IntLiteral = int_value 0 [concrete = constants.%int_0]
 // CHECK:STDOUT:   %.loc11_57.3: ref %f32.97e = array_index %a.var, %int_0
-// CHECK:STDOUT:   %.loc11_57.4: init %f32.97e to %.loc11_57.3 = initialize_from %.loc11_57.2 [concrete = constants.%float.e3b]
+// CHECK:STDOUT:   %.loc11_57.4: init %f32.97e to %.loc11_57.3 = in_place_init %.loc11_57.2 [concrete = constants.%float.e3b]
 // CHECK:STDOUT:   %.loc11_57.5: init %array_type to %a.var = array_init (%.loc11_57.4) [concrete = constants.%array]
 // CHECK:STDOUT:   %.loc11_3: init %array_type = converted %.loc11_57.1, %.loc11_57.5 [concrete = constants.%array]
 // CHECK:STDOUT:   assign %a.var, %.loc11_3
@@ -1217,7 +1217,7 @@ fn CopyUnsignedLong() {
 // CHECK:STDOUT:   %.loc16_62.1: ref %LongResult = temporary_storage
 // CHECK:STDOUT:   %addr.loc16: %ptr.305 = addr_of %.loc16_62.1
 // CHECK:STDOUT:   %PassLong__carbon_thunk.call.loc16: init %empty_tuple.type = call imports.%PassLong__carbon_thunk.decl.d16229.1(%cpp_long.ref.loc16, %addr.loc16)
-// CHECK:STDOUT:   %.loc16_62.2: init %LongResult to %.loc16_62.1 = in_place_init %PassLong__carbon_thunk.call.loc16
+// CHECK:STDOUT:   %.loc16_62.2: init %LongResult to %.loc16_62.1 = mark_in_place_init %PassLong__carbon_thunk.call.loc16
 // CHECK:STDOUT:   %.loc16_27: type = splice_block %LongResult.ref.loc16 [concrete = constants.%LongResult] {
 // CHECK:STDOUT:     %Cpp.ref.loc16_24: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
 // CHECK:STDOUT:     %LongResult.ref.loc16: type = name_ref LongResult, imports.%LongResult.decl [concrete = constants.%LongResult]
@@ -1244,7 +1244,7 @@ fn CopyUnsignedLong() {
 // CHECK:STDOUT:   %.loc19_76.1: ref %LongResult = temporary_storage
 // CHECK:STDOUT:   %addr.loc19: %ptr.305 = addr_of %.loc19_76.1
 // CHECK:STDOUT:   %PassLong__carbon_thunk.call.loc19: init %empty_tuple.type = call imports.%PassLong__carbon_thunk.decl.d16229.1(%cpp_compat_long.ref, %addr.loc19)
-// CHECK:STDOUT:   %.loc19_76.2: init %LongResult to %.loc19_76.1 = in_place_init %PassLong__carbon_thunk.call.loc19
+// CHECK:STDOUT:   %.loc19_76.2: init %LongResult to %.loc19_76.1 = mark_in_place_init %PassLong__carbon_thunk.call.loc19
 // CHECK:STDOUT:   %.loc19_34: type = splice_block %LongResult.ref.loc19 [concrete = constants.%LongResult] {
 // CHECK:STDOUT:     %Cpp.ref.loc19_31: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
 // CHECK:STDOUT:     %LongResult.ref.loc19: type = name_ref LongResult, imports.%LongResult.decl [concrete = constants.%LongResult]
@@ -1274,7 +1274,7 @@ fn CopyUnsignedLong() {
 // CHECK:STDOUT:   %.loc22_65.1: ref %IntResult = temporary_storage
 // CHECK:STDOUT:   %addr.loc22: %ptr.3cb = addr_of %.loc22_65.1
 // CHECK:STDOUT:   %PassLong__carbon_thunk.call.loc22: init %empty_tuple.type = call imports.%PassLong__carbon_thunk.decl.d16229.2(%carbon_i32.ref, %addr.loc22)
-// CHECK:STDOUT:   %.loc22_65.2: init %IntResult to %.loc22_65.1 = in_place_init %PassLong__carbon_thunk.call.loc22
+// CHECK:STDOUT:   %.loc22_65.2: init %IntResult to %.loc22_65.1 = mark_in_place_init %PassLong__carbon_thunk.call.loc22
 // CHECK:STDOUT:   %.loc22_29: type = splice_block %IntResult.ref [concrete = constants.%IntResult] {
 // CHECK:STDOUT:     %Cpp.ref.loc22_26: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
 // CHECK:STDOUT:     %IntResult.ref: type = name_ref IntResult, imports.%IntResult.decl [concrete = constants.%IntResult]
@@ -1311,7 +1311,7 @@ fn CopyUnsignedLong() {
 // CHECK:STDOUT:   %.loc26_43.2: init %f32.97e = converted %float, %Core.FloatLiteral.as.ImplicitAs.impl.Convert.call [concrete = constants.%float.e3b]
 // CHECK:STDOUT:   %int_0: Core.IntLiteral = int_value 0 [concrete = constants.%int_0]
 // CHECK:STDOUT:   %.loc26_43.3: ref %f32.97e = array_index %a.var, %int_0
-// CHECK:STDOUT:   %.loc26_43.4: init %f32.97e to %.loc26_43.3 = initialize_from %.loc26_43.2 [concrete = constants.%float.e3b]
+// CHECK:STDOUT:   %.loc26_43.4: init %f32.97e to %.loc26_43.3 = in_place_init %.loc26_43.2 [concrete = constants.%float.e3b]
 // CHECK:STDOUT:   %.loc26_43.5: init %array_type to %a.var = array_init (%.loc26_43.4) [concrete = constants.%array]
 // CHECK:STDOUT:   %.loc26_3: init %array_type = converted %.loc26_43.1, %.loc26_43.5 [concrete = constants.%array]
 // CHECK:STDOUT:   assign %a.var, %.loc26_3
@@ -8208,7 +8208,7 @@ fn CopyUnsignedLong() {
 // CHECK:STDOUT:   %.loc16_82.1: ref %ULongResult = temporary_storage
 // CHECK:STDOUT:   %addr.loc16: %ptr.f5e = addr_of %.loc16_82.1
 // CHECK:STDOUT:   %PassULong__carbon_thunk.call.loc16: init %empty_tuple.type = call imports.%PassULong__carbon_thunk.decl.108234.1(%cpp_unsigned_long.ref.loc16, %addr.loc16)
-// CHECK:STDOUT:   %.loc16_82.2: init %ULongResult to %.loc16_82.1 = in_place_init %PassULong__carbon_thunk.call.loc16
+// CHECK:STDOUT:   %.loc16_82.2: init %ULongResult to %.loc16_82.1 = mark_in_place_init %PassULong__carbon_thunk.call.loc16
 // CHECK:STDOUT:   %.loc16_36: type = splice_block %ULongResult.ref.loc16 [concrete = constants.%ULongResult] {
 // CHECK:STDOUT:     %Cpp.ref.loc16_33: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
 // CHECK:STDOUT:     %ULongResult.ref.loc16: type = name_ref ULongResult, imports.%ULongResult.decl [concrete = constants.%ULongResult]
@@ -8235,7 +8235,7 @@ fn CopyUnsignedLong() {
 // CHECK:STDOUT:   %.loc19_80.1: ref %ULongResult = temporary_storage
 // CHECK:STDOUT:   %addr.loc19: %ptr.f5e = addr_of %.loc19_80.1
 // CHECK:STDOUT:   %PassULong__carbon_thunk.call.loc19: init %empty_tuple.type = call imports.%PassULong__carbon_thunk.decl.108234.1(%cpp_compat_ulong.ref, %addr.loc19)
-// CHECK:STDOUT:   %.loc19_80.2: init %ULongResult to %.loc19_80.1 = in_place_init %PassULong__carbon_thunk.call.loc19
+// CHECK:STDOUT:   %.loc19_80.2: init %ULongResult to %.loc19_80.1 = mark_in_place_init %PassULong__carbon_thunk.call.loc19
 // CHECK:STDOUT:   %.loc19_35: type = splice_block %ULongResult.ref.loc19 [concrete = constants.%ULongResult] {
 // CHECK:STDOUT:     %Cpp.ref.loc19_32: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
 // CHECK:STDOUT:     %ULongResult.ref.loc19: type = name_ref ULongResult, imports.%ULongResult.decl [concrete = constants.%ULongResult]
@@ -8266,7 +8266,7 @@ fn CopyUnsignedLong() {
 // CHECK:STDOUT:   %.loc22_67.1: ref %UIntResult = temporary_storage
 // CHECK:STDOUT:   %addr.loc22: %ptr.059 = addr_of %.loc22_67.1
 // CHECK:STDOUT:   %PassULong__carbon_thunk.call.loc22: init %empty_tuple.type = call imports.%PassULong__carbon_thunk.decl.108234.2(%carbon_u32.ref, %addr.loc22)
-// CHECK:STDOUT:   %.loc22_67.2: init %UIntResult to %.loc22_67.1 = in_place_init %PassULong__carbon_thunk.call.loc22
+// CHECK:STDOUT:   %.loc22_67.2: init %UIntResult to %.loc22_67.1 = mark_in_place_init %PassULong__carbon_thunk.call.loc22
 // CHECK:STDOUT:   %.loc22_29: type = splice_block %UIntResult.ref [concrete = constants.%UIntResult] {
 // CHECK:STDOUT:     %Cpp.ref.loc22_26: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
 // CHECK:STDOUT:     %UIntResult.ref: type = name_ref UIntResult, imports.%UIntResult.decl [concrete = constants.%UIntResult]
@@ -8289,7 +8289,7 @@ fn CopyUnsignedLong() {
 // CHECK:STDOUT:   %.loc24_52.2: init %f32.97e = converted %float, %Core.FloatLiteral.as.ImplicitAs.impl.Convert.call [concrete = constants.%float.e3b]
 // CHECK:STDOUT:   %int_0: Core.IntLiteral = int_value 0 [concrete = constants.%int_0]
 // CHECK:STDOUT:   %.loc24_52.3: ref %f32.97e = array_index %a.var, %int_0
-// CHECK:STDOUT:   %.loc24_52.4: init %f32.97e to %.loc24_52.3 = initialize_from %.loc24_52.2 [concrete = constants.%float.e3b]
+// CHECK:STDOUT:   %.loc24_52.4: init %f32.97e to %.loc24_52.3 = in_place_init %.loc24_52.2 [concrete = constants.%float.e3b]
 // CHECK:STDOUT:   %.loc24_52.5: init %array_type to %a.var = array_init (%.loc24_52.4) [concrete = constants.%array]
 // CHECK:STDOUT:   %.loc24_3: init %array_type = converted %.loc24_52.1, %.loc24_52.5 [concrete = constants.%array]
 // CHECK:STDOUT:   assign %a.var, %.loc24_3
diff --git a/toolchain/check/testdata/interop/cpp/builtins.lp64.carbon b/toolchain/check/testdata/interop/cpp/builtins.lp64.carbon
index 23f92ee7d21e..14d35caf52e6 100644
--- a/toolchain/check/testdata/interop/cpp/builtins.lp64.carbon
+++ b/toolchain/check/testdata/interop/cpp/builtins.lp64.carbon
@@ -791,7 +791,7 @@ fn CopyUnsignedLongLong() {
 // CHECK:STDOUT:   %.loc11_43.2: init %f32.97e = converted %float, %Core.FloatLiteral.as.ImplicitAs.impl.Convert.call [concrete = constants.%float.e3b]
 // CHECK:STDOUT:   %int_0: Core.IntLiteral = int_value 0 [concrete = constants.%int_0]
 // CHECK:STDOUT:   %.loc11_43.3: ref %f32.97e = array_index %a.var, %int_0
-// CHECK:STDOUT:   %.loc11_43.4: init %f32.97e to %.loc11_43.3 = initialize_from %.loc11_43.2 [concrete = constants.%float.e3b]
+// CHECK:STDOUT:   %.loc11_43.4: init %f32.97e to %.loc11_43.3 = in_place_init %.loc11_43.2 [concrete = constants.%float.e3b]
 // CHECK:STDOUT:   %.loc11_43.5: init %array_type to %a.var = array_init (%.loc11_43.4) [concrete = constants.%array]
 // CHECK:STDOUT:   %.loc11_3: init %array_type = converted %.loc11_43.1, %.loc11_43.5 [concrete = constants.%array]
 // CHECK:STDOUT:   assign %a.var, %.loc11_3
@@ -957,7 +957,7 @@ fn CopyUnsignedLongLong() {
 // CHECK:STDOUT:   %.loc11_52.2: init %f32.97e = converted %float, %Core.FloatLiteral.as.ImplicitAs.impl.Convert.call [concrete = constants.%float.e3b]
 // CHECK:STDOUT:   %int_0: Core.IntLiteral = int_value 0 [concrete = constants.%int_0]
 // CHECK:STDOUT:   %.loc11_52.3: ref %f32.97e = array_index %a.var, %int_0
-// CHECK:STDOUT:   %.loc11_52.4: init %f32.97e to %.loc11_52.3 = initialize_from %.loc11_52.2 [concrete = constants.%float.e3b]
+// CHECK:STDOUT:   %.loc11_52.4: init %f32.97e to %.loc11_52.3 = in_place_init %.loc11_52.2 [concrete = constants.%float.e3b]
 // CHECK:STDOUT:   %.loc11_52.5: init %array_type to %a.var = array_init (%.loc11_52.4) [concrete = constants.%array]
 // CHECK:STDOUT:   %.loc11_3: init %array_type = converted %.loc11_52.1, %.loc11_52.5 [concrete = constants.%array]
 // CHECK:STDOUT:   assign %a.var, %.loc11_3
@@ -1156,7 +1156,7 @@ fn CopyUnsignedLongLong() {
 // CHECK:STDOUT:   %.loc16_80.1: ref %LongLongResult = temporary_storage
 // CHECK:STDOUT:   %addr.loc16: %ptr.a95 = addr_of %.loc16_80.1
 // CHECK:STDOUT:   %PassLongLong__carbon_thunk.call.loc16: init %empty_tuple.type = call imports.%PassLongLong__carbon_thunk.decl.139b1c.1(%cpp_long_long.ref.loc16, %addr.loc16)
-// CHECK:STDOUT:   %.loc16_80.2: init %LongLongResult to %.loc16_80.1 = in_place_init %PassLongLong__carbon_thunk.call.loc16
+// CHECK:STDOUT:   %.loc16_80.2: init %LongLongResult to %.loc16_80.1 = mark_in_place_init %PassLongLong__carbon_thunk.call.loc16
 // CHECK:STDOUT:   %.loc16_32: type = splice_block %LongLongResult.ref.loc16 [concrete = constants.%LongLongResult] {
 // CHECK:STDOUT:     %Cpp.ref.loc16_29: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
 // CHECK:STDOUT:     %LongLongResult.ref.loc16: type = name_ref LongLongResult, imports.%LongLongResult.decl [concrete = constants.%LongLongResult]
@@ -1183,7 +1183,7 @@ fn CopyUnsignedLongLong() {
 // CHECK:STDOUT:   %.loc19_94.1: ref %LongLongResult = temporary_storage
 // CHECK:STDOUT:   %addr.loc19: %ptr.a95 = addr_of %.loc19_94.1
 // CHECK:STDOUT:   %PassLongLong__carbon_thunk.call.loc19: init %empty_tuple.type = call imports.%PassLongLong__carbon_thunk.decl.139b1c.1(%cpp_compat_long_long.ref, %addr.loc19)
-// CHECK:STDOUT:   %.loc19_94.2: init %LongLongResult to %.loc19_94.1 = in_place_init %PassLongLong__carbon_thunk.call.loc19
+// CHECK:STDOUT:   %.loc19_94.2: init %LongLongResult to %.loc19_94.1 = mark_in_place_init %PassLongLong__carbon_thunk.call.loc19
 // CHECK:STDOUT:   %.loc19_39: type = splice_block %LongLongResult.ref.loc19 [concrete = constants.%LongLongResult] {
 // CHECK:STDOUT:     %Cpp.ref.loc19_36: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
 // CHECK:STDOUT:     %LongLongResult.ref.loc19: type = name_ref LongLongResult, imports.%LongLongResult.decl [concrete = constants.%LongLongResult]
@@ -1213,7 +1213,7 @@ fn CopyUnsignedLongLong() {
 // CHECK:STDOUT:   %.loc22_70.1: ref %LongResult = temporary_storage
 // CHECK:STDOUT:   %addr.loc22: %ptr.305 = addr_of %.loc22_70.1
 // CHECK:STDOUT:   %PassLongLong__carbon_thunk.call.loc22: init %empty_tuple.type = call imports.%PassLongLong__carbon_thunk.decl.139b1c.2(%carbon_i64.ref, %addr.loc22)
-// CHECK:STDOUT:   %.loc22_70.2: init %LongResult to %.loc22_70.1 = in_place_init %PassLongLong__carbon_thunk.call.loc22
+// CHECK:STDOUT:   %.loc22_70.2: init %LongResult to %.loc22_70.1 = mark_in_place_init %PassLongLong__carbon_thunk.call.loc22
 // CHECK:STDOUT:   %.loc22_29: type = splice_block %LongResult.ref [concrete = constants.%LongResult] {
 // CHECK:STDOUT:     %Cpp.ref.loc22_26: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
 // CHECK:STDOUT:     %LongResult.ref: type = name_ref LongResult, imports.%LongResult.decl [concrete = constants.%LongResult]
@@ -1236,7 +1236,7 @@ fn CopyUnsignedLongLong() {
 // CHECK:STDOUT:   %.loc24_48.2: init %f32.97e = converted %float, %Core.FloatLiteral.as.ImplicitAs.impl.Convert.call [concrete = constants.%float.e3b]
 // CHECK:STDOUT:   %int_0: Core.IntLiteral = int_value 0 [concrete = constants.%int_0]
 // CHECK:STDOUT:   %.loc24_48.3: ref %f32.97e = array_index %a.var, %int_0
-// CHECK:STDOUT:   %.loc24_48.4: init %f32.97e to %.loc24_48.3 = initialize_from %.loc24_48.2 [concrete = constants.%float.e3b]
+// CHECK:STDOUT:   %.loc24_48.4: init %f32.97e to %.loc24_48.3 = in_place_init %.loc24_48.2 [concrete = constants.%float.e3b]
 // CHECK:STDOUT:   %.loc24_48.5: init %array_type to %a.var = array_init (%.loc24_48.4) [concrete = constants.%array]
 // CHECK:STDOUT:   %.loc24_3: init %array_type = converted %.loc24_48.1, %.loc24_48.5 [concrete = constants.%array]
 // CHECK:STDOUT:   assign %a.var, %.loc24_3
@@ -8100,7 +8100,7 @@ fn CopyUnsignedLongLong() {
 // CHECK:STDOUT:   %.loc16_100.1: ref %ULongLongResult = temporary_storage
 // CHECK:STDOUT:   %addr.loc16: %ptr.d19 = addr_of %.loc16_100.1
 // CHECK:STDOUT:   %PassULongLong__carbon_thunk.call.loc16: init %empty_tuple.type = call imports.%PassULongLong__carbon_thunk.decl.f0c073.1(%cpp_unsigned_long_long.ref.loc16, %addr.loc16)
-// CHECK:STDOUT:   %.loc16_100.2: init %ULongLongResult to %.loc16_100.1 = in_place_init %PassULongLong__carbon_thunk.call.loc16
+// CHECK:STDOUT:   %.loc16_100.2: init %ULongLongResult to %.loc16_100.1 = mark_in_place_init %PassULongLong__carbon_thunk.call.loc16
 // CHECK:STDOUT:   %.loc16_41: type = splice_block %ULongLongResult.ref.loc16 [concrete = constants.%ULongLongResult] {
 // CHECK:STDOUT:     %Cpp.ref.loc16_38: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
 // CHECK:STDOUT:     %ULongLongResult.ref.loc16: type = name_ref ULongLongResult, imports.%ULongLongResult.decl [concrete = constants.%ULongLongResult]
@@ -8127,7 +8127,7 @@ fn CopyUnsignedLongLong() {
 // CHECK:STDOUT:   %.loc19_98.1: ref %ULongLongResult = temporary_storage
 // CHECK:STDOUT:   %addr.loc19: %ptr.d19 = addr_of %.loc19_98.1
 // CHECK:STDOUT:   %PassULongLong__carbon_thunk.call.loc19: init %empty_tuple.type = call imports.%PassULongLong__carbon_thunk.decl.f0c073.1(%cpp_compat_ulong_long.ref, %addr.loc19)
-// CHECK:STDOUT:   %.loc19_98.2: init %ULongLongResult to %.loc19_98.1 = in_place_init %PassULongLong__carbon_thunk.call.loc19
+// CHECK:STDOUT:   %.loc19_98.2: init %ULongLongResult to %.loc19_98.1 = mark_in_place_init %PassULongLong__carbon_thunk.call.loc19
 // CHECK:STDOUT:   %.loc19_40: type = splice_block %ULongLongResult.ref.loc19 [concrete = constants.%ULongLongResult] {
 // CHECK:STDOUT:     %Cpp.ref.loc19_37: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
 // CHECK:STDOUT:     %ULongLongResult.ref.loc19: type = name_ref ULongLongResult, imports.%ULongLongResult.decl [concrete = constants.%ULongLongResult]
@@ -8158,7 +8158,7 @@ fn CopyUnsignedLongLong() {
 // CHECK:STDOUT:   %.loc22_72.1: ref %ULongResult = temporary_storage
 // CHECK:STDOUT:   %addr.loc22: %ptr.f5e = addr_of %.loc22_72.1
 // CHECK:STDOUT:   %PassULongLong__carbon_thunk.call.loc22: init %empty_tuple.type = call imports.%PassULongLong__carbon_thunk.decl.f0c073.2(%carbon_u64.ref, %addr.loc22)
-// CHECK:STDOUT:   %.loc22_72.2: init %ULongResult to %.loc22_72.1 = in_place_init %PassULongLong__carbon_thunk.call.loc22
+// CHECK:STDOUT:   %.loc22_72.2: init %ULongResult to %.loc22_72.1 = mark_in_place_init %PassULongLong__carbon_thunk.call.loc22
 // CHECK:STDOUT:   %.loc22_29: type = splice_block %ULongResult.ref [concrete = constants.%ULongResult] {
 // CHECK:STDOUT:     %Cpp.ref.loc22_26: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
 // CHECK:STDOUT:     %ULongResult.ref: type = name_ref ULongResult, imports.%ULongResult.decl [concrete = constants.%ULongResult]
@@ -8181,7 +8181,7 @@ fn CopyUnsignedLongLong() {
 // CHECK:STDOUT:   %.loc24_57.2: init %f32.97e = converted %float, %Core.FloatLiteral.as.ImplicitAs.impl.Convert.call [concrete = constants.%float.e3b]
 // CHECK:STDOUT:   %int_0: Core.IntLiteral = int_value 0 [concrete = constants.%int_0]
 // CHECK:STDOUT:   %.loc24_57.3: ref %f32.97e = array_index %a.var, %int_0
-// CHECK:STDOUT:   %.loc24_57.4: init %f32.97e to %.loc24_57.3 = initialize_from %.loc24_57.2 [concrete = constants.%float.e3b]
+// CHECK:STDOUT:   %.loc24_57.4: init %f32.97e to %.loc24_57.3 = in_place_init %.loc24_57.2 [concrete = constants.%float.e3b]
 // CHECK:STDOUT:   %.loc24_57.5: init %array_type to %a.var = array_init (%.loc24_57.4) [concrete = constants.%array]
 // CHECK:STDOUT:   %.loc24_3: init %array_type = converted %.loc24_57.1, %.loc24_57.5 [concrete = constants.%array]
 // CHECK:STDOUT:   assign %a.var, %.loc24_3
diff --git a/toolchain/check/testdata/interop/cpp/class/access.carbon b/toolchain/check/testdata/interop/cpp/class/access.carbon
index d6bfc0980df8..9bcd893feaaa 100644
--- a/toolchain/check/testdata/interop/cpp/class/access.carbon
+++ b/toolchain/check/testdata/interop/cpp/class/access.carbon
@@ -1998,7 +1998,7 @@ fn Call(var instance: Cpp.PublicPrivate) {
 // CHECK:STDOUT:   %.loc8_37.1: ref %PublicCall = temporary_storage
 // CHECK:STDOUT:   %addr.loc8_37: %ptr.dfa = addr_of %.loc8_37.1
 // CHECK:STDOUT:   %PublicCall__carbon_thunk.call.loc8: init %empty_tuple.type = call imports.%PublicCall__carbon_thunk.decl(%addr.loc8_37)
-// CHECK:STDOUT:   %.loc8_37.2: init %PublicCall to %.loc8_37.1 = in_place_init %PublicCall__carbon_thunk.call.loc8
+// CHECK:STDOUT:   %.loc8_37.2: init %PublicCall to %.loc8_37.1 = mark_in_place_init %PublicCall__carbon_thunk.call.loc8
 // CHECK:STDOUT:   %.loc8_38.1: ref %C = temporary_storage
 // CHECK:STDOUT:   %.loc8_37.3: ref %PublicCall = temporary %.loc8_37.1, %.loc8_37.2
 // CHECK:STDOUT:   %.loc8_37.4: %PublicCall = acquire_value %.loc8_37.3
@@ -2006,7 +2006,7 @@ fn Call(var instance: Cpp.PublicPrivate) {
 // CHECK:STDOUT:   %addr.loc8_38.1: %ptr.dfa = addr_of %.loc8_37.5
 // CHECK:STDOUT:   %addr.loc8_38.2: %ptr.d9e = addr_of %.loc8_38.1
 // CHECK:STDOUT:   %C__carbon_thunk.call: init %empty_tuple.type = call imports.%C__carbon_thunk.decl(%addr.loc8_38.1, %addr.loc8_38.2)
-// CHECK:STDOUT:   %.loc8_38.2: init %C to %.loc8_38.1 = in_place_init %C__carbon_thunk.call
+// CHECK:STDOUT:   %.loc8_38.2: init %C to %.loc8_38.1 = mark_in_place_init %C__carbon_thunk.call
 // CHECK:STDOUT:   %.loc8_38.3: ref %C = temporary %.loc8_38.1, %.loc8_38.2
 // CHECK:STDOUT:   %Cpp.ref.loc9_3: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
 // CHECK:STDOUT:   %C.ref.loc9: type = name_ref C, imports.%C.decl [concrete = constants.%C]
@@ -2017,7 +2017,7 @@ fn Call(var instance: Cpp.PublicPrivate) {
 // CHECK:STDOUT:   %.loc9_44.1: ref %PublicCall = temporary_storage
 // CHECK:STDOUT:   %addr.loc9_44: %ptr.dfa = addr_of %.loc9_44.1
 // CHECK:STDOUT:   %PublicCall__carbon_thunk.call.loc9: init %empty_tuple.type = call imports.%PublicCall__carbon_thunk.decl(%addr.loc9_44)
-// CHECK:STDOUT:   %.loc9_44.2: init %PublicCall to %.loc9_44.1 = in_place_init %PublicCall__carbon_thunk.call.loc9
+// CHECK:STDOUT:   %.loc9_44.2: init %PublicCall to %.loc9_44.1 = mark_in_place_init %PublicCall__carbon_thunk.call.loc9
 // CHECK:STDOUT:   %.loc9_44.3: ref %PublicCall = temporary %.loc9_44.1, %.loc9_44.2
 // CHECK:STDOUT:   %.loc9_44.4: %PublicCall = acquire_value %.loc9_44.3
 // CHECK:STDOUT:   %.loc9_44.5: ref %PublicCall = value_as_ref %.loc9_44.4
@@ -2146,7 +2146,7 @@ fn Call(var instance: Cpp.PublicPrivate) {
 // CHECK:STDOUT:   %.loc11_49.1: ref %PublicCall = temporary_storage
 // CHECK:STDOUT:   %addr.loc11_49: %ptr.dfa = addr_of %.loc11_49.1
 // CHECK:STDOUT:   %PublicCall__carbon_thunk.call: init %empty_tuple.type = call imports.%PublicCall__carbon_thunk.decl(%addr.loc11_49)
-// CHECK:STDOUT:   %.loc11_49.2: init %PublicCall to %.loc11_49.1 = in_place_init %PublicCall__carbon_thunk.call
+// CHECK:STDOUT:   %.loc11_49.2: init %PublicCall to %.loc11_49.1 = mark_in_place_init %PublicCall__carbon_thunk.call
 // CHECK:STDOUT:   %.loc11_51.1: ref %C = class_element_access %return.param, element0
 // CHECK:STDOUT:   %.loc11_49.3: ref %PublicCall = temporary %.loc11_49.1, %.loc11_49.2
 // CHECK:STDOUT:   %.loc11_49.4: %PublicCall = acquire_value %.loc11_49.3
@@ -2154,7 +2154,7 @@ fn Call(var instance: Cpp.PublicPrivate) {
 // CHECK:STDOUT:   %addr.loc11_50.1: %ptr.dfa = addr_of %.loc11_49.5
 // CHECK:STDOUT:   %addr.loc11_50.2: %ptr.d9e = addr_of %.loc11_51.1
 // CHECK:STDOUT:   %C__carbon_thunk.call: init %empty_tuple.type = call imports.%C__carbon_thunk.decl.8acdfe.1(%addr.loc11_50.1, %addr.loc11_50.2)
-// CHECK:STDOUT:   %.loc11_50: init %C to %.loc11_51.1 = in_place_init %C__carbon_thunk.call
+// CHECK:STDOUT:   %.loc11_50: init %C to %.loc11_51.1 = mark_in_place_init %C__carbon_thunk.call
 // CHECK:STDOUT:   %.loc11_51.2: %struct_type.base.7c3 = struct_literal (%.loc11_50)
 // CHECK:STDOUT:   %.loc11_51.3: init %D to %return.param = class_init (%.loc11_50)
 // CHECK:STDOUT:   %.loc11_52: init %D = converted %.loc11_51.2, %.loc11_51.3
@@ -2172,7 +2172,7 @@ fn Call(var instance: Cpp.PublicPrivate) {
 // CHECK:STDOUT:   %.loc17_55.1: ref %ProtectedCall = temporary_storage
 // CHECK:STDOUT:   %addr.loc17_55: %ptr.8e6 = addr_of %.loc17_55.1
 // CHECK:STDOUT:   %ProtectedCall__carbon_thunk.call: init %empty_tuple.type = call imports.%ProtectedCall__carbon_thunk.decl(%addr.loc17_55)
-// CHECK:STDOUT:   %.loc17_55.2: init %ProtectedCall to %.loc17_55.1 = in_place_init %ProtectedCall__carbon_thunk.call
+// CHECK:STDOUT:   %.loc17_55.2: init %ProtectedCall to %.loc17_55.1 = mark_in_place_init %ProtectedCall__carbon_thunk.call
 // CHECK:STDOUT:   %.loc17_57.1: ref %C = class_element_access %return.param, element0
 // CHECK:STDOUT:   %.loc17_55.3: ref %ProtectedCall = temporary %.loc17_55.1, %.loc17_55.2
 // CHECK:STDOUT:   %.loc17_55.4: %ProtectedCall = acquire_value %.loc17_55.3
@@ -2180,7 +2180,7 @@ fn Call(var instance: Cpp.PublicPrivate) {
 // CHECK:STDOUT:   %addr.loc17_56.1: %ptr.8e6 = addr_of %.loc17_55.5
 // CHECK:STDOUT:   %addr.loc17_56.2: %ptr.d9e = addr_of %.loc17_57.1
 // CHECK:STDOUT:   %C__carbon_thunk.call: init %empty_tuple.type = call imports.%C__carbon_thunk.decl.8acdfe.2(%addr.loc17_56.1, %addr.loc17_56.2)
-// CHECK:STDOUT:   %.loc17_56: init %C to %.loc17_57.1 = in_place_init %C__carbon_thunk.call
+// CHECK:STDOUT:   %.loc17_56: init %C to %.loc17_57.1 = mark_in_place_init %C__carbon_thunk.call
 // CHECK:STDOUT:   %.loc17_57.2: %struct_type.base.7c3 = struct_literal (%.loc17_56)
 // CHECK:STDOUT:   %.loc17_57.3: init %D to %return.param = class_init (%.loc17_56)
 // CHECK:STDOUT:   %.loc17_58: init %D = converted %.loc17_57.2, %.loc17_57.3
@@ -2198,7 +2198,7 @@ fn Call(var instance: Cpp.PublicPrivate) {
 // CHECK:STDOUT:   %.loc23_40.1: ref %PublicCall = temporary_storage
 // CHECK:STDOUT:   %addr.loc23_40: %ptr.dfa = addr_of %.loc23_40.1
 // CHECK:STDOUT:   %PublicCall__carbon_thunk.call: init %empty_tuple.type = call imports.%PublicCall__carbon_thunk.decl(%addr.loc23_40)
-// CHECK:STDOUT:   %.loc23_40.2: init %PublicCall to %.loc23_40.1 = in_place_init %PublicCall__carbon_thunk.call
+// CHECK:STDOUT:   %.loc23_40.2: init %PublicCall to %.loc23_40.1 = mark_in_place_init %PublicCall__carbon_thunk.call
 // CHECK:STDOUT:   %.loc23_40.3: ref %PublicCall = temporary %.loc23_40.1, %.loc23_40.2
 // CHECK:STDOUT:   %.loc23_40.4: %PublicCall = acquire_value %.loc23_40.3
 // CHECK:STDOUT:   %.loc23_40.5: ref %PublicCall = value_as_ref %.loc23_40.4
@@ -2218,7 +2218,7 @@ fn Call(var instance: Cpp.PublicPrivate) {
 // CHECK:STDOUT:   %.loc29_46.1: ref %ProtectedCall = temporary_storage
 // CHECK:STDOUT:   %addr.loc29_46: %ptr.8e6 = addr_of %.loc29_46.1
 // CHECK:STDOUT:   %ProtectedCall__carbon_thunk.call: init %empty_tuple.type = call imports.%ProtectedCall__carbon_thunk.decl(%addr.loc29_46)
-// CHECK:STDOUT:   %.loc29_46.2: init %ProtectedCall to %.loc29_46.1 = in_place_init %ProtectedCall__carbon_thunk.call
+// CHECK:STDOUT:   %.loc29_46.2: init %ProtectedCall to %.loc29_46.1 = mark_in_place_init %ProtectedCall__carbon_thunk.call
 // CHECK:STDOUT:   %.loc29_46.3: ref %ProtectedCall = temporary %.loc29_46.1, %.loc29_46.2
 // CHECK:STDOUT:   %.loc29_46.4: %ProtectedCall = acquire_value %.loc29_46.3
 // CHECK:STDOUT:   %.loc29_46.5: ref %ProtectedCall = value_as_ref %.loc29_46.4
@@ -2285,7 +2285,7 @@ fn Call(var instance: Cpp.PublicPrivate) {
 // CHECK:STDOUT:   %.loc8_49.1: ref %PublicCall = temporary_storage
 // CHECK:STDOUT:   %addr.loc8_49: %ptr.dfa = addr_of %.loc8_49.1
 // CHECK:STDOUT:   %PublicCall__carbon_thunk.call: init %empty_tuple.type = call imports.%PublicCall__carbon_thunk.decl(%addr.loc8_49)
-// CHECK:STDOUT:   %.loc8_49.2: init %PublicCall to %.loc8_49.1 = in_place_init %PublicCall__carbon_thunk.call
+// CHECK:STDOUT:   %.loc8_49.2: init %PublicCall to %.loc8_49.1 = mark_in_place_init %PublicCall__carbon_thunk.call
 // CHECK:STDOUT:   %.loc8_49.3: ref %PublicCall = temporary %.loc8_49.1, %.loc8_49.2
 // CHECK:STDOUT:   %.loc8_49.4: %PublicCall = acquire_value %.loc8_49.3
 // CHECK:STDOUT:   %.loc8_49.5: ref %PublicCall = value_as_ref %.loc8_49.4
@@ -2384,7 +2384,7 @@ fn Call(var instance: Cpp.PublicPrivate) {
 // CHECK:STDOUT:   %.loc11_40.1: ref %PublicCall = temporary_storage
 // CHECK:STDOUT:   %addr.loc11_40: %ptr.dfa = addr_of %.loc11_40.1
 // CHECK:STDOUT:   %PublicCall__carbon_thunk.call: init %empty_tuple.type = call imports.%PublicCall__carbon_thunk.decl(%addr.loc11_40)
-// CHECK:STDOUT:   %.loc11_40.2: init %PublicCall to %.loc11_40.1 = in_place_init %PublicCall__carbon_thunk.call
+// CHECK:STDOUT:   %.loc11_40.2: init %PublicCall to %.loc11_40.1 = mark_in_place_init %PublicCall__carbon_thunk.call
 // CHECK:STDOUT:   %.loc11_40.3: ref %PublicCall = temporary %.loc11_40.1, %.loc11_40.2
 // CHECK:STDOUT:   %.loc11_40.4: %PublicCall = acquire_value %.loc11_40.3
 // CHECK:STDOUT:   %.loc11_40.5: ref %PublicCall = value_as_ref %.loc11_40.4
@@ -2397,7 +2397,7 @@ fn Call(var instance: Cpp.PublicPrivate) {
 // CHECK:STDOUT:   %.loc12_46.1: ref %ProtectedCall = temporary_storage
 // CHECK:STDOUT:   %addr.loc12_46: %ptr.8e6 = addr_of %.loc12_46.1
 // CHECK:STDOUT:   %ProtectedCall__carbon_thunk.call: init %empty_tuple.type = call imports.%ProtectedCall__carbon_thunk.decl(%addr.loc12_46)
-// CHECK:STDOUT:   %.loc12_46.2: init %ProtectedCall to %.loc12_46.1 = in_place_init %ProtectedCall__carbon_thunk.call
+// CHECK:STDOUT:   %.loc12_46.2: init %ProtectedCall to %.loc12_46.1 = mark_in_place_init %ProtectedCall__carbon_thunk.call
 // CHECK:STDOUT:   %.loc12_46.3: ref %ProtectedCall = temporary %.loc12_46.1, %.loc12_46.2
 // CHECK:STDOUT:   %.loc12_46.4: %ProtectedCall = acquire_value %.loc12_46.3
 // CHECK:STDOUT:   %.loc12_46.5: ref %ProtectedCall = value_as_ref %.loc12_46.4
@@ -2500,7 +2500,7 @@ fn Call(var instance: Cpp.PublicPrivate) {
 // CHECK:STDOUT:   %.loc11_40.1: ref %PublicCall = temporary_storage
 // CHECK:STDOUT:   %addr.loc11_40: %ptr.dfa = addr_of %.loc11_40.1
 // CHECK:STDOUT:   %PublicCall__carbon_thunk.call: init %empty_tuple.type = call imports.%PublicCall__carbon_thunk.decl(%addr.loc11_40)
-// CHECK:STDOUT:   %.loc11_40.2: init %PublicCall to %.loc11_40.1 = in_place_init %PublicCall__carbon_thunk.call
+// CHECK:STDOUT:   %.loc11_40.2: init %PublicCall to %.loc11_40.1 = mark_in_place_init %PublicCall__carbon_thunk.call
 // CHECK:STDOUT:   %.loc11_40.3: ref %PublicCall = temporary %.loc11_40.1, %.loc11_40.2
 // CHECK:STDOUT:   %.loc11_40.4: %PublicCall = acquire_value %.loc11_40.3
 // CHECK:STDOUT:   %.loc11_40.5: ref %PublicCall = value_as_ref %.loc11_40.4
@@ -2513,7 +2513,7 @@ fn Call(var instance: Cpp.PublicPrivate) {
 // CHECK:STDOUT:   %.loc12_46.1: ref %ProtectedCall = temporary_storage
 // CHECK:STDOUT:   %addr.loc12_46: %ptr.8e6 = addr_of %.loc12_46.1
 // CHECK:STDOUT:   %ProtectedCall__carbon_thunk.call: init %empty_tuple.type = call imports.%ProtectedCall__carbon_thunk.decl(%addr.loc12_46)
-// CHECK:STDOUT:   %.loc12_46.2: init %ProtectedCall to %.loc12_46.1 = in_place_init %ProtectedCall__carbon_thunk.call
+// CHECK:STDOUT:   %.loc12_46.2: init %ProtectedCall to %.loc12_46.1 = mark_in_place_init %ProtectedCall__carbon_thunk.call
 // CHECK:STDOUT:   %.loc12_46.3: ref %ProtectedCall = temporary %.loc12_46.1, %.loc12_46.2
 // CHECK:STDOUT:   %.loc12_46.4: %ProtectedCall = acquire_value %.loc12_46.3
 // CHECK:STDOUT:   %.loc12_46.5: ref %ProtectedCall = value_as_ref %.loc12_46.4
diff --git a/toolchain/check/testdata/interop/cpp/class/constructor.carbon b/toolchain/check/testdata/interop/cpp/class/constructor.carbon
index 9cb35a3089d5..06432b379bb4 100644
--- a/toolchain/check/testdata/interop/cpp/class/constructor.carbon
+++ b/toolchain/check/testdata/interop/cpp/class/constructor.carbon
@@ -295,7 +295,7 @@ fn F() {
 // CHECK:STDOUT:   %.loc8_26.1: ref %C = temporary_storage
 // CHECK:STDOUT:   %addr: %ptr.d9e = addr_of %.loc8_26.1
 // CHECK:STDOUT:   %C__carbon_thunk.call: init %empty_tuple.type = call imports.%C__carbon_thunk.decl(%addr)
-// CHECK:STDOUT:   %.loc8_26.2: init %C to %.loc8_26.1 = in_place_init %C__carbon_thunk.call
+// CHECK:STDOUT:   %.loc8_26.2: init %C to %.loc8_26.1 = mark_in_place_init %C__carbon_thunk.call
 // CHECK:STDOUT:   %.loc8_13: type = splice_block %C.ref.loc8_13 [concrete = constants.%C] {
 // CHECK:STDOUT:     %Cpp.ref.loc8_10: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
 // CHECK:STDOUT:     %C.ref.loc8_13: type = name_ref C, imports.%C.decl [concrete = constants.%C]
@@ -389,7 +389,7 @@ fn F() {
 // CHECK:STDOUT:   %.loc8_31.2: %i32 = converted %int_456, %.loc8_31.1 [concrete = constants.%int_456.d17]
 // CHECK:STDOUT:   %addr: %ptr.d9e = addr_of %.loc8_34.1
 // CHECK:STDOUT:   %C__carbon_thunk.call: init %empty_tuple.type = call imports.%C__carbon_thunk.decl(%.loc8_26.2, %.loc8_31.2, %addr)
-// CHECK:STDOUT:   %.loc8_34.2: init %C to %.loc8_34.1 = in_place_init %C__carbon_thunk.call
+// CHECK:STDOUT:   %.loc8_34.2: init %C to %.loc8_34.1 = mark_in_place_init %C__carbon_thunk.call
 // CHECK:STDOUT:   %.loc8_13: type = splice_block %C.ref.loc8_13 [concrete = constants.%C] {
 // CHECK:STDOUT:     %Cpp.ref.loc8_10: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
 // CHECK:STDOUT:     %C.ref.loc8_13: type = name_ref C, imports.%C.decl [concrete = constants.%C]
@@ -474,7 +474,7 @@ fn F() {
 // CHECK:STDOUT:   %.loc8_27.1: ref %C = temporary_storage
 // CHECK:STDOUT:   %addr.loc8: %ptr.d9e = addr_of %.loc8_27.1
 // CHECK:STDOUT:   %C__carbon_thunk.call.loc8: init %empty_tuple.type = call imports.%C__carbon_thunk.decl.8acdfe.1(%addr.loc8)
-// CHECK:STDOUT:   %.loc8_27.2: init %C to %.loc8_27.1 = in_place_init %C__carbon_thunk.call.loc8
+// CHECK:STDOUT:   %.loc8_27.2: init %C to %.loc8_27.1 = mark_in_place_init %C__carbon_thunk.call.loc8
 // CHECK:STDOUT:   %.loc8_14: type = splice_block %C.ref.loc8_14 [concrete = constants.%C] {
 // CHECK:STDOUT:     %Cpp.ref.loc8_11: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
 // CHECK:STDOUT:     %C.ref.loc8_14: type = name_ref C, imports.%C.decl [concrete = constants.%C]
@@ -507,7 +507,7 @@ fn F() {
 // CHECK:STDOUT:   %.loc9_32.2: %i32 = converted %int_456, %.loc9_32.1 [concrete = constants.%int_456.d17]
 // CHECK:STDOUT:   %addr.loc9: %ptr.d9e = addr_of %.loc9_35.1
 // CHECK:STDOUT:   %C__carbon_thunk.call.loc9: init %empty_tuple.type = call imports.%C__carbon_thunk.decl.8acdfe.2(%.loc9_27.2, %.loc9_32.2, %addr.loc9)
-// CHECK:STDOUT:   %.loc9_35.2: init %C to %.loc9_35.1 = in_place_init %C__carbon_thunk.call.loc9
+// CHECK:STDOUT:   %.loc9_35.2: init %C to %.loc9_35.1 = mark_in_place_init %C__carbon_thunk.call.loc9
 // CHECK:STDOUT:   %.loc9_14: type = splice_block %C.ref.loc9_14 [concrete = constants.%C] {
 // CHECK:STDOUT:     %Cpp.ref.loc9_11: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
 // CHECK:STDOUT:     %C.ref.loc9_14: type = name_ref C, imports.%C.decl [concrete = constants.%C]
@@ -610,7 +610,7 @@ fn F() {
 // CHECK:STDOUT:   %.loc8_30.2: %i32 = converted %int_9, %.loc8_30.1 [concrete = constants.%int_9.f88]
 // CHECK:STDOUT:   %addr.loc8: %ptr.d9e = addr_of %.loc8_31.1
 // CHECK:STDOUT:   %C__carbon_thunk.call.loc8: init %empty_tuple.type = call imports.%C__carbon_thunk.decl.8acdfe.1(%.loc8_27.2, %.loc8_30.2, %addr.loc8)
-// CHECK:STDOUT:   %.loc8_31.2: init %C to %.loc8_31.1 = in_place_init %C__carbon_thunk.call.loc8
+// CHECK:STDOUT:   %.loc8_31.2: init %C to %.loc8_31.1 = mark_in_place_init %C__carbon_thunk.call.loc8
 // CHECK:STDOUT:   %.loc8_14: type = splice_block %C.ref.loc8_14 [concrete = constants.%C] {
 // CHECK:STDOUT:     %Cpp.ref.loc8_11: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
 // CHECK:STDOUT:     %C.ref.loc8_14: type = name_ref C, imports.%C.decl [concrete = constants.%C]
@@ -635,7 +635,7 @@ fn F() {
 // CHECK:STDOUT:   %.loc9_27.2: %i32 = converted %int_8.loc9, %.loc9_27.1 [concrete = constants.%int_8.98c]
 // CHECK:STDOUT:   %addr.loc9: %ptr.d9e = addr_of %.loc9_28.1
 // CHECK:STDOUT:   %C__carbon_thunk.call.loc9: init %empty_tuple.type = call imports.%C__carbon_thunk.decl.8acdfe.2(%.loc9_27.2, %addr.loc9)
-// CHECK:STDOUT:   %.loc9_28.2: init %C to %.loc9_28.1 = in_place_init %C__carbon_thunk.call.loc9
+// CHECK:STDOUT:   %.loc9_28.2: init %C to %.loc9_28.1 = mark_in_place_init %C__carbon_thunk.call.loc9
 // CHECK:STDOUT:   %.loc9_14: type = splice_block %C.ref.loc9_14 [concrete = constants.%C] {
 // CHECK:STDOUT:     %Cpp.ref.loc9_11: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
 // CHECK:STDOUT:     %C.ref.loc9_14: type = name_ref C, imports.%C.decl [concrete = constants.%C]
@@ -749,7 +749,7 @@ fn F() {
 // CHECK:STDOUT:   %.loc8_27.2: %i32 = converted %int_123, %.loc8_27.1 [concrete = constants.%int_123.f7f]
 // CHECK:STDOUT:   %addr.loc8: %ptr.d9e = addr_of %.loc8_3
 // CHECK:STDOUT:   %C__carbon_thunk.call.loc8: init %empty_tuple.type = call imports.%C__carbon_thunk.decl.8acdfe.1(%.loc8_27.2, %addr.loc8)
-// CHECK:STDOUT:   %.loc8_30: init %C to %.loc8_3 = in_place_init %C__carbon_thunk.call.loc8
+// CHECK:STDOUT:   %.loc8_30: init %C to %.loc8_3 = mark_in_place_init %C__carbon_thunk.call.loc8
 // CHECK:STDOUT:   assign %c1.var, %.loc8_30
 // CHECK:STDOUT:   %.loc8_14: type = splice_block %C.ref.loc8_14 [concrete = constants.%C] {
 // CHECK:STDOUT:     %Cpp.ref.loc8_11: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
@@ -774,7 +774,7 @@ fn F() {
 // CHECK:STDOUT:   %addr.loc9_31.1: %ptr.bb2 = addr_of %.loc9_27.2
 // CHECK:STDOUT:   %addr.loc9_31.2: %ptr.d9e = addr_of %.loc9_3
 // CHECK:STDOUT:   %C__carbon_thunk.call.loc9: init %empty_tuple.type = call imports.%C__carbon_thunk.decl.8acdfe.2(%addr.loc9_31.1, %addr.loc9_31.2)
-// CHECK:STDOUT:   %.loc9_31: init %C to %.loc9_3 = in_place_init %C__carbon_thunk.call.loc9
+// CHECK:STDOUT:   %.loc9_31: init %C to %.loc9_3 = mark_in_place_init %C__carbon_thunk.call.loc9
 // CHECK:STDOUT:   assign %c2.var, %.loc9_31
 // CHECK:STDOUT:   %.loc9_14: type = splice_block %C.ref.loc9_14 [concrete = constants.%C] {
 // CHECK:STDOUT:     %Cpp.ref.loc9_11: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
@@ -794,7 +794,7 @@ fn F() {
 // CHECK:STDOUT:   %.loc10_3: ref %C = splice_block %c3.var {}
 // CHECK:STDOUT:   %addr.loc10_30: %ptr.d9e = addr_of %.loc10_3
 // CHECK:STDOUT:   %C__carbon_thunk.call.loc10: init %empty_tuple.type = call imports.%C__carbon_thunk.decl.8acdfe.3(%addr.loc10_27, %addr.loc10_30)
-// CHECK:STDOUT:   %.loc10_30: init %C to %.loc10_3 = in_place_init %C__carbon_thunk.call.loc10
+// CHECK:STDOUT:   %.loc10_30: init %C to %.loc10_3 = mark_in_place_init %C__carbon_thunk.call.loc10
 // CHECK:STDOUT:   assign %c3.var, %.loc10_30
 // CHECK:STDOUT:   %.loc10_14: type = splice_block %C.ref.loc10_14 [concrete = constants.%C] {
 // CHECK:STDOUT:     %Cpp.ref.loc10_11: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
@@ -897,7 +897,7 @@ fn F() {
 // CHECK:STDOUT:   %.loc8_27.2: %i32 = converted %int_8.loc8, %.loc8_27.1 [concrete = constants.%int_8.98c]
 // CHECK:STDOUT:   %addr.loc8: %ptr.d9e = addr_of %.loc8_28.1
 // CHECK:STDOUT:   %C__carbon_thunk.call.loc8: init %empty_tuple.type = call imports.%C__carbon_thunk.decl(%.loc8_27.2, %addr.loc8)
-// CHECK:STDOUT:   %.loc8_28.2: init %C to %.loc8_28.1 = in_place_init %C__carbon_thunk.call.loc8
+// CHECK:STDOUT:   %.loc8_28.2: init %C to %.loc8_28.1 = mark_in_place_init %C__carbon_thunk.call.loc8
 // CHECK:STDOUT:   %.loc8_14: type = splice_block %C.ref.loc8_14 [concrete = constants.%C] {
 // CHECK:STDOUT:     %Cpp.ref.loc8_11: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
 // CHECK:STDOUT:     %C.ref.loc8_14: type = name_ref C, imports.%C.decl [concrete = constants.%C]
@@ -925,7 +925,7 @@ fn F() {
 // CHECK:STDOUT:   %.loc9_21.3: ref %C = temporary_storage
 // CHECK:STDOUT:   %addr.loc9: %ptr.d9e = addr_of %.loc9_21.3
 // CHECK:STDOUT:   %C__carbon_thunk.call.loc9: init %empty_tuple.type = call imports.%C__carbon_thunk.decl(%.loc9_21.2, %addr.loc9)
-// CHECK:STDOUT:   %.loc9_21.4: init %C to %.loc9_21.3 = in_place_init %C__carbon_thunk.call.loc9
+// CHECK:STDOUT:   %.loc9_21.4: init %C to %.loc9_21.3 = mark_in_place_init %C__carbon_thunk.call.loc9
 // CHECK:STDOUT:   %.loc9_21.5: init %C = converted %.loc9_21.2, %.loc9_21.4
 // CHECK:STDOUT:   %.loc9_21.6: ref %C = temporary %.loc9_21.3, %.loc9_21.5
 // CHECK:STDOUT:   %.loc9_21.7: %C = acquire_value %.loc9_21.6
@@ -1039,7 +1039,7 @@ fn F() {
 // CHECK:STDOUT:   %.loc8_30.2: %i32 = converted %int_9, %.loc8_30.1 [concrete = constants.%int_9.f88]
 // CHECK:STDOUT:   %addr.loc8: %ptr.d9e = addr_of %.loc8_31.1
 // CHECK:STDOUT:   %C__carbon_thunk.call.loc8: init %empty_tuple.type = call imports.%C__carbon_thunk.decl.8acdfe.1(%.loc8_27.2, %.loc8_30.2, %addr.loc8)
-// CHECK:STDOUT:   %.loc8_31.2: init %C to %.loc8_31.1 = in_place_init %C__carbon_thunk.call.loc8
+// CHECK:STDOUT:   %.loc8_31.2: init %C to %.loc8_31.1 = mark_in_place_init %C__carbon_thunk.call.loc8
 // CHECK:STDOUT:   %.loc8_14: type = splice_block %C.ref.loc8_14 [concrete = constants.%C] {
 // CHECK:STDOUT:     %Cpp.ref.loc8_11: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
 // CHECK:STDOUT:     %C.ref.loc8_14: type = name_ref C, imports.%C.decl [concrete = constants.%C]
@@ -1064,7 +1064,7 @@ fn F() {
 // CHECK:STDOUT:   %.loc9_27.2: %i32 = converted %int_8.loc9, %.loc9_27.1 [concrete = constants.%int_8.98c]
 // CHECK:STDOUT:   %addr.loc9: %ptr.d9e = addr_of %.loc9_28.1
 // CHECK:STDOUT:   %C__carbon_thunk.call.loc9: init %empty_tuple.type = call imports.%C__carbon_thunk.decl.8acdfe.2(%.loc9_27.2, %addr.loc9)
-// CHECK:STDOUT:   %.loc9_28.2: init %C to %.loc9_28.1 = in_place_init %C__carbon_thunk.call.loc9
+// CHECK:STDOUT:   %.loc9_28.2: init %C to %.loc9_28.1 = mark_in_place_init %C__carbon_thunk.call.loc9
 // CHECK:STDOUT:   %.loc9_14: type = splice_block %C.ref.loc9_14 [concrete = constants.%C] {
 // CHECK:STDOUT:     %Cpp.ref.loc9_11: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
 // CHECK:STDOUT:     %C.ref.loc9_14: type = name_ref C, imports.%C.decl [concrete = constants.%C]
@@ -1092,7 +1092,7 @@ fn F() {
 // CHECK:STDOUT:   %.loc10_21.3: ref %C = temporary_storage
 // CHECK:STDOUT:   %addr.loc10: %ptr.d9e = addr_of %.loc10_21.3
 // CHECK:STDOUT:   %C__carbon_thunk.call.loc10: init %empty_tuple.type = call imports.%C__carbon_thunk.decl.8acdfe.2(%.loc10_21.2, %addr.loc10)
-// CHECK:STDOUT:   %.loc10_21.4: init %C to %.loc10_21.3 = in_place_init %C__carbon_thunk.call.loc10
+// CHECK:STDOUT:   %.loc10_21.4: init %C to %.loc10_21.3 = mark_in_place_init %C__carbon_thunk.call.loc10
 // CHECK:STDOUT:   %.loc10_21.5: init %C = converted %.loc10_21.2, %.loc10_21.4
 // CHECK:STDOUT:   %.loc10_21.6: ref %C = temporary %.loc10_21.3, %.loc10_21.5
 // CHECK:STDOUT:   %.loc10_21.7: %C = acquire_value %.loc10_21.6
diff --git a/toolchain/check/testdata/interop/cpp/class/field.carbon b/toolchain/check/testdata/interop/cpp/class/field.carbon
index 32bec46b5eda..f3c055273a61 100644
--- a/toolchain/check/testdata/interop/cpp/class/field.carbon
+++ b/toolchain/check/testdata/interop/cpp/class/field.carbon
@@ -295,14 +295,14 @@ fn Test(m: Cpp.UnsupportedMembers*) {
 // CHECK:STDOUT:   %bound_method.loc8_12.2: <bound method> = bound_method %.loc8_12.2, %specific_fn.loc8_12
 // CHECK:STDOUT:   %Int.as.Copy.impl.Op.call.loc8_12: init %i32 = call %bound_method.loc8_12.2(%.loc8_12.2)
 // CHECK:STDOUT:   %tuple.elem0: ref %i32 = tuple_access %return.param, element0
-// CHECK:STDOUT:   %.loc8_43.2: init %i32 to %tuple.elem0 = initialize_from %Int.as.Copy.impl.Op.call.loc8_12
+// CHECK:STDOUT:   %.loc8_43.2: init %i32 to %tuple.elem0 = in_place_init %Int.as.Copy.impl.Op.call.loc8_12
 // CHECK:STDOUT:   %impl.elem0.loc8_17: %.f79 = impl_witness_access constants.%Copy.impl_witness.f17, element0 [concrete = constants.%Int.as.Copy.impl.Op.664]
 // CHECK:STDOUT:   %bound_method.loc8_17.1: <bound method> = bound_method %.loc8_17.2, %impl.elem0.loc8_17
 // CHECK:STDOUT:   %specific_fn.loc8_17: <specific function> = specific_function %impl.elem0.loc8_17, @Int.as.Copy.impl.Op(constants.%int_32) [concrete = constants.%Int.as.Copy.impl.Op.specific_fn]
 // CHECK:STDOUT:   %bound_method.loc8_17.2: <bound method> = bound_method %.loc8_17.2, %specific_fn.loc8_17
 // CHECK:STDOUT:   %Int.as.Copy.impl.Op.call.loc8_17: init %i32 = call %bound_method.loc8_17.2(%.loc8_17.2)
 // CHECK:STDOUT:   %tuple.elem1: ref %i32 = tuple_access %return.param, element1
-// CHECK:STDOUT:   %.loc8_43.3: init %i32 to %tuple.elem1 = initialize_from %Int.as.Copy.impl.Op.call.loc8_17
+// CHECK:STDOUT:   %.loc8_43.3: init %i32 to %tuple.elem1 = in_place_init %Int.as.Copy.impl.Op.call.loc8_17
 // CHECK:STDOUT:   %.loc8_21.2: %i32 = acquire_value %.loc8_21.1
 // CHECK:STDOUT:   %impl.elem0.loc8_21: %.f79 = impl_witness_access constants.%Copy.impl_witness.f17, element0 [concrete = constants.%Int.as.Copy.impl.Op.664]
 // CHECK:STDOUT:   %bound_method.loc8_21.1: <bound method> = bound_method %.loc8_21.2, %impl.elem0.loc8_21
@@ -310,7 +310,7 @@ fn Test(m: Cpp.UnsupportedMembers*) {
 // CHECK:STDOUT:   %bound_method.loc8_21.2: <bound method> = bound_method %.loc8_21.2, %specific_fn.loc8_21
 // CHECK:STDOUT:   %Int.as.Copy.impl.Op.call.loc8_21: init %i32 = call %bound_method.loc8_21.2(%.loc8_21.2)
 // CHECK:STDOUT:   %tuple.elem2: ref %i32 = tuple_access %return.param, element2
-// CHECK:STDOUT:   %.loc8_43.4: init %i32 to %tuple.elem2 = initialize_from %Int.as.Copy.impl.Op.call.loc8_21
+// CHECK:STDOUT:   %.loc8_43.4: init %i32 to %tuple.elem2 = in_place_init %Int.as.Copy.impl.Op.call.loc8_21
 // CHECK:STDOUT:   %.loc8_27.2: %i32 = acquire_value %.loc8_27.1
 // CHECK:STDOUT:   %impl.elem0.loc8_27: %.f79 = impl_witness_access constants.%Copy.impl_witness.f17, element0 [concrete = constants.%Int.as.Copy.impl.Op.664]
 // CHECK:STDOUT:   %bound_method.loc8_27.1: <bound method> = bound_method %.loc8_27.2, %impl.elem0.loc8_27
@@ -318,7 +318,7 @@ fn Test(m: Cpp.UnsupportedMembers*) {
 // CHECK:STDOUT:   %bound_method.loc8_27.2: <bound method> = bound_method %.loc8_27.2, %specific_fn.loc8_27
 // CHECK:STDOUT:   %Int.as.Copy.impl.Op.call.loc8_27: init %i32 = call %bound_method.loc8_27.2(%.loc8_27.2)
 // CHECK:STDOUT:   %tuple.elem3: ref %i32 = tuple_access %return.param, element3
-// CHECK:STDOUT:   %.loc8_43.5: init %i32 to %tuple.elem3 = initialize_from %Int.as.Copy.impl.Op.call.loc8_27
+// CHECK:STDOUT:   %.loc8_43.5: init %i32 to %tuple.elem3 = in_place_init %Int.as.Copy.impl.Op.call.loc8_27
 // CHECK:STDOUT:   %.loc8_39.2: %i32 = acquire_value %.loc8_39.1
 // CHECK:STDOUT:   %impl.elem0.loc8_39: %.f79 = impl_witness_access constants.%Copy.impl_witness.f17, element0 [concrete = constants.%Int.as.Copy.impl.Op.664]
 // CHECK:STDOUT:   %bound_method.loc8_39.1: <bound method> = bound_method %.loc8_39.2, %impl.elem0.loc8_39
@@ -326,7 +326,7 @@ fn Test(m: Cpp.UnsupportedMembers*) {
 // CHECK:STDOUT:   %bound_method.loc8_39.2: <bound method> = bound_method %.loc8_39.2, %specific_fn.loc8_39
 // CHECK:STDOUT:   %Int.as.Copy.impl.Op.call.loc8_39: init %i32 = call %bound_method.loc8_39.2(%.loc8_39.2)
 // CHECK:STDOUT:   %tuple.elem4: ref %i32 = tuple_access %return.param, element4
-// CHECK:STDOUT:   %.loc8_43.6: init %i32 to %tuple.elem4 = initialize_from %Int.as.Copy.impl.Op.call.loc8_39
+// CHECK:STDOUT:   %.loc8_43.6: init %i32 to %tuple.elem4 = in_place_init %Int.as.Copy.impl.Op.call.loc8_39
 // CHECK:STDOUT:   %.loc8_43.7: init %tuple.type.a78 to %return.param = tuple_init (%.loc8_43.2, %.loc8_43.3, %.loc8_43.4, %.loc8_43.5, %.loc8_43.6)
 // CHECK:STDOUT:   %.loc8_44: init %tuple.type.a78 = converted %.loc8_43.1, %.loc8_43.7
 // CHECK:STDOUT:   return %.loc8_44 to %return.param
diff --git a/toolchain/check/testdata/interop/cpp/enum/anonymous.carbon b/toolchain/check/testdata/interop/cpp/enum/anonymous.carbon
index 3ad8c5bf04b4..0d068bb60b21 100644
--- a/toolchain/check/testdata/interop/cpp/enum/anonymous.carbon
+++ b/toolchain/check/testdata/interop/cpp/enum/anonymous.carbon
@@ -117,7 +117,7 @@ fn G() {
 // CHECK:STDOUT:   %.loc10_11.1: ref %C = temporary_storage
 // CHECK:STDOUT:   %addr: %ptr.d9e = addr_of %.loc10_11.1
 // CHECK:STDOUT:   %C__carbon_thunk.call: init %empty_tuple.type = call imports.%C__carbon_thunk.decl(%addr)
-// CHECK:STDOUT:   %.loc10_11.2: init %C to %.loc10_11.1 = in_place_init %C__carbon_thunk.call
+// CHECK:STDOUT:   %.loc10_11.2: init %C to %.loc10_11.1 = mark_in_place_init %C__carbon_thunk.call
 // CHECK:STDOUT:   %.loc10_11.3: ref %C = temporary %.loc10_11.1, %.loc10_11.2
 // CHECK:STDOUT:   %F.ref.loc10: %C.F.cpp_overload_set.type = name_ref F, imports.%C.F.cpp_overload_set.value [concrete = constants.%C.F.cpp_overload_set.value]
 // CHECK:STDOUT:   %bound_method: <bound method> = bound_method %.loc10_11.3, %F.ref.loc10
diff --git a/toolchain/check/testdata/interop/cpp/function/arithmetic_types_bridged.carbon b/toolchain/check/testdata/interop/cpp/function/arithmetic_types_bridged.carbon
index 9178e62efbe5..63a2e481af97 100644
--- a/toolchain/check/testdata/interop/cpp/function/arithmetic_types_bridged.carbon
+++ b/toolchain/check/testdata/interop/cpp/function/arithmetic_types_bridged.carbon
@@ -2075,6 +2075,8 @@ fn F() {
 // CHECK:STDOUT:   %ptr: type = ptr_type bool [concrete]
 // CHECK:STDOUT:   %foo_bool__carbon_thunk.type: type = fn_type @foo_bool__carbon_thunk [concrete]
 // CHECK:STDOUT:   %foo_bool__carbon_thunk: %foo_bool__carbon_thunk.type = struct_value () [concrete]
+// CHECK:STDOUT:   %DestroyOp.type: type = fn_type @DestroyOp [concrete]
+// CHECK:STDOUT:   %DestroyOp: %DestroyOp.type = struct_value () [concrete]
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: imports {
@@ -2100,18 +2102,22 @@ fn F() {
 // CHECK:STDOUT:   %.loc8_30.1: ref bool = temporary_storage
 // CHECK:STDOUT:   %addr: %ptr = addr_of %.loc8_30.1
 // CHECK:STDOUT:   %foo_bool__carbon_thunk.call: init %empty_tuple.type = call imports.%foo_bool__carbon_thunk.decl(%addr)
-// CHECK:STDOUT:   %.loc8_30.2: init bool = in_place_init %foo_bool__carbon_thunk.call, %.loc8_30.1
+// CHECK:STDOUT:   %.loc8_30.2: init bool to %.loc8_30.1 = mark_in_place_init %foo_bool__carbon_thunk.call
 // CHECK:STDOUT:   %.loc8_10.1: type = splice_block %.loc8_10.3 [concrete = bool] {
 // CHECK:STDOUT:     %Bool.call: init type = call constants.%Bool() [concrete = bool]
 // CHECK:STDOUT:     %.loc8_10.2: type = value_of_initializer %Bool.call [concrete = bool]
 // CHECK:STDOUT:     %.loc8_10.3: type = converted %Bool.call, %.loc8_10.2 [concrete = bool]
 // CHECK:STDOUT:   }
-// CHECK:STDOUT:   %.loc8_30.3: bool = value_of_initializer %.loc8_30.2
-// CHECK:STDOUT:   %.loc8_30.4: bool = converted %.loc8_30.2, %.loc8_30.3
+// CHECK:STDOUT:   %.loc8_30.3: ref bool = temporary %.loc8_30.1, %.loc8_30.2
+// CHECK:STDOUT:   %.loc8_30.4: bool = acquire_value %.loc8_30.3
 // CHECK:STDOUT:   %x: bool = value_binding x, %.loc8_30.4
+// CHECK:STDOUT:   %DestroyOp.bound: <bound method> = bound_method %.loc8_30.3, constants.%DestroyOp
+// CHECK:STDOUT:   %DestroyOp.call: init %empty_tuple.type = call %DestroyOp.bound(%.loc8_30.3)
 // CHECK:STDOUT:   <elided>
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
+// CHECK:STDOUT: fn @DestroyOp(%self.param: bool) = "no_op";
+// CHECK:STDOUT:
 // CHECK:STDOUT: --- import_short_return.carbon
 // CHECK:STDOUT:
 // CHECK:STDOUT: constants {
@@ -2124,6 +2130,8 @@ fn F() {
 // CHECK:STDOUT:   %ptr: type = ptr_type %i16 [concrete]
 // CHECK:STDOUT:   %foo_short__carbon_thunk.type: type = fn_type @foo_short__carbon_thunk [concrete]
 // CHECK:STDOUT:   %foo_short__carbon_thunk: %foo_short__carbon_thunk.type = struct_value () [concrete]
+// CHECK:STDOUT:   %DestroyOp.type: type = fn_type @DestroyOp [concrete]
+// CHECK:STDOUT:   %DestroyOp: %DestroyOp.type = struct_value () [concrete]
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: imports {
@@ -2149,17 +2157,21 @@ fn F() {
 // CHECK:STDOUT:   %.loc8_30.1: ref %i16 = temporary_storage
 // CHECK:STDOUT:   %addr: %ptr = addr_of %.loc8_30.1
 // CHECK:STDOUT:   %foo_short__carbon_thunk.call: init %empty_tuple.type = call imports.%foo_short__carbon_thunk.decl(%addr)
-// CHECK:STDOUT:   %.loc8_30.2: init %i16 = in_place_init %foo_short__carbon_thunk.call, %.loc8_30.1
+// CHECK:STDOUT:   %.loc8_30.2: init %i16 to %.loc8_30.1 = mark_in_place_init %foo_short__carbon_thunk.call
 // CHECK:STDOUT:   %.loc8_10: type = splice_block %i16 [concrete = constants.%i16] {
 // CHECK:STDOUT:     %int_16: Core.IntLiteral = int_value 16 [concrete = constants.%int_16]
 // CHECK:STDOUT:     %i16: type = class_type @Int, @Int(constants.%int_16) [concrete = constants.%i16]
 // CHECK:STDOUT:   }
-// CHECK:STDOUT:   %.loc8_30.3: %i16 = value_of_initializer %.loc8_30.2
-// CHECK:STDOUT:   %.loc8_30.4: %i16 = converted %.loc8_30.2, %.loc8_30.3
+// CHECK:STDOUT:   %.loc8_30.3: ref %i16 = temporary %.loc8_30.1, %.loc8_30.2
+// CHECK:STDOUT:   %.loc8_30.4: %i16 = acquire_value %.loc8_30.3
 // CHECK:STDOUT:   %x: %i16 = value_binding x, %.loc8_30.4
+// CHECK:STDOUT:   %DestroyOp.bound: <bound method> = bound_method %.loc8_30.3, constants.%DestroyOp
+// CHECK:STDOUT:   %DestroyOp.call: init %empty_tuple.type = call %DestroyOp.bound(%.loc8_30.3)
 // CHECK:STDOUT:   <elided>
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
+// CHECK:STDOUT: fn @DestroyOp(%self.param: %i16) = "no_op";
+// CHECK:STDOUT:
 // CHECK:STDOUT: --- fail_todo_import_bit_int_24_param.carbon
 // CHECK:STDOUT:
 // CHECK:STDOUT: constants {
@@ -2196,6 +2208,8 @@ fn F() {
 // CHECK:STDOUT:   %ptr: type = ptr_type %f64.d77 [concrete]
 // CHECK:STDOUT:   %foo_double__carbon_thunk.type: type = fn_type @foo_double__carbon_thunk [concrete]
 // CHECK:STDOUT:   %foo_double__carbon_thunk: %foo_double__carbon_thunk.type = struct_value () [concrete]
+// CHECK:STDOUT:   %DestroyOp.type: type = fn_type @DestroyOp [concrete]
+// CHECK:STDOUT:   %DestroyOp: %DestroyOp.type = struct_value () [concrete]
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: imports {
@@ -2221,14 +2235,18 @@ fn F() {
 // CHECK:STDOUT:   %.loc8_31.1: ref %f64.d77 = temporary_storage
 // CHECK:STDOUT:   %addr: %ptr = addr_of %.loc8_31.1
 // CHECK:STDOUT:   %foo_double__carbon_thunk.call: init %empty_tuple.type = call imports.%foo_double__carbon_thunk.decl(%addr)
-// CHECK:STDOUT:   %.loc8_31.2: init %f64.d77 = in_place_init %foo_double__carbon_thunk.call, %.loc8_31.1
+// CHECK:STDOUT:   %.loc8_31.2: init %f64.d77 to %.loc8_31.1 = mark_in_place_init %foo_double__carbon_thunk.call
 // CHECK:STDOUT:   %.loc8_10: type = splice_block %f64 [concrete = constants.%f64.d77] {
 // CHECK:STDOUT:     %int_64: Core.IntLiteral = int_value 64 [concrete = constants.%int_64]
 // CHECK:STDOUT:     %f64: type = class_type @Float, @Float(constants.%int_64) [concrete = constants.%f64.d77]
 // CHECK:STDOUT:   }
-// CHECK:STDOUT:   %.loc8_31.3: %f64.d77 = value_of_initializer %.loc8_31.2
-// CHECK:STDOUT:   %.loc8_31.4: %f64.d77 = converted %.loc8_31.2, %.loc8_31.3
+// CHECK:STDOUT:   %.loc8_31.3: ref %f64.d77 = temporary %.loc8_31.1, %.loc8_31.2
+// CHECK:STDOUT:   %.loc8_31.4: %f64.d77 = acquire_value %.loc8_31.3
 // CHECK:STDOUT:   %x: %f64.d77 = value_binding x, %.loc8_31.4
+// CHECK:STDOUT:   %DestroyOp.bound: <bound method> = bound_method %.loc8_31.3, constants.%DestroyOp
+// CHECK:STDOUT:   %DestroyOp.call: init %empty_tuple.type = call %DestroyOp.bound(%.loc8_31.3)
 // CHECK:STDOUT:   <elided>
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
+// CHECK:STDOUT: fn @DestroyOp(%self.param: %f64.d77) = "no_op";
+// CHECK:STDOUT:
diff --git a/toolchain/check/testdata/interop/cpp/function/class.carbon b/toolchain/check/testdata/interop/cpp/function/class.carbon
index 0f05490a8cb9..8ee5d6516461 100644
--- a/toolchain/check/testdata/interop/cpp/function/class.carbon
+++ b/toolchain/check/testdata/interop/cpp/function/class.carbon
@@ -1006,7 +1006,7 @@ fn F() {
 // CHECK:STDOUT:   %.loc8_11.1: ref %C = temporary_storage
 // CHECK:STDOUT:   %addr: %ptr.d9e = addr_of %.loc8_11.1
 // CHECK:STDOUT:   %foo__carbon_thunk.call: init %empty_tuple.type = call imports.%foo__carbon_thunk.decl(%addr)
-// CHECK:STDOUT:   %.loc8_11.2: init %C to %.loc8_11.1 = in_place_init %foo__carbon_thunk.call
+// CHECK:STDOUT:   %.loc8_11.2: init %C to %.loc8_11.1 = mark_in_place_init %foo__carbon_thunk.call
 // CHECK:STDOUT:   %.loc8_11.3: ref %C = temporary %.loc8_11.1, %.loc8_11.2
 // CHECK:STDOUT:   %C.cpp_destructor.bound: <bound method> = bound_method %.loc8_11.3, constants.%C.cpp_destructor
 // CHECK:STDOUT:   %C.cpp_destructor.call: init %empty_tuple.type = call %C.cpp_destructor.bound(%.loc8_11.3)
diff --git a/toolchain/check/testdata/interop/cpp/function/extern_c.carbon b/toolchain/check/testdata/interop/cpp/function/extern_c.carbon
index ffb990d9fa60..0e28115fecf2 100644
--- a/toolchain/check/testdata/interop/cpp/function/extern_c.carbon
+++ b/toolchain/check/testdata/interop/cpp/function/extern_c.carbon
@@ -234,7 +234,7 @@ fn MyF(a: Cpp.X, b: Cpp.X) -> Cpp.X {
 // CHECK:STDOUT:   %addr.loc11_12.2: %ptr.1f9 = addr_of %.loc11_14
 // CHECK:STDOUT:   %addr.loc11_12.3: %ptr.1f9 = addr_of %.loc9_34.1
 // CHECK:STDOUT:   %operator_Plus__carbon_thunk.call: init %empty_tuple.type = call imports.%operator_Plus__carbon_thunk.decl(%addr.loc11_12.1, %addr.loc11_12.2, %addr.loc11_12.3)
-// CHECK:STDOUT:   %.loc11_12: init %X to %.loc9_34.1 = in_place_init %operator_Plus__carbon_thunk.call
+// CHECK:STDOUT:   %.loc11_12: init %X to %.loc9_34.1 = mark_in_place_init %operator_Plus__carbon_thunk.call
 // CHECK:STDOUT:   return %.loc11_12 to %return.param
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
diff --git a/toolchain/check/testdata/interop/cpp/function/full_semir.carbon b/toolchain/check/testdata/interop/cpp/function/full_semir.carbon
index 951923a73719..837900d8e548 100644
--- a/toolchain/check/testdata/interop/cpp/function/full_semir.carbon
+++ b/toolchain/check/testdata/interop/cpp/function/full_semir.carbon
@@ -309,11 +309,15 @@ fn F() {
 // CHECK:STDOUT:   %pattern_type.54c: type = pattern_type %ptr [concrete]
 // CHECK:STDOUT:   %foo_short__carbon_thunk.type: type = fn_type @foo_short__carbon_thunk [concrete]
 // CHECK:STDOUT:   %foo_short__carbon_thunk: %foo_short__carbon_thunk.type = struct_value () [concrete]
+// CHECK:STDOUT:   %Destroy.type: type = facet_type <@Destroy> [concrete]
+// CHECK:STDOUT:   %DestroyOp.type: type = fn_type @DestroyOp [concrete]
+// CHECK:STDOUT:   %DestroyOp: %DestroyOp.type = struct_value () [concrete]
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: imports {
 // CHECK:STDOUT:   %Core: <namespace> = namespace file.%Core.import, [concrete] {
 // CHECK:STDOUT:     .Int = %Core.Int
+// CHECK:STDOUT:     .Destroy = %Core.Destroy
 // CHECK:STDOUT:     import Core//prelude
 // CHECK:STDOUT:     import Core//prelude/...
 // CHECK:STDOUT:   }
@@ -334,6 +338,7 @@ fn F() {
 // CHECK:STDOUT:     }
 // CHECK:STDOUT:     %return: %ptr = value_binding r#return, %return.param
 // CHECK:STDOUT:   }
+// CHECK:STDOUT:   %Core.Destroy: type = import_ref Core//prelude/parts/destroy, Destroy, loaded [concrete = constants.%Destroy.type]
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: file {
@@ -359,14 +364,16 @@ fn F() {
 // CHECK:STDOUT:   %.loc7_30.1: ref %i16 = temporary_storage
 // CHECK:STDOUT:   %addr: %ptr = addr_of %.loc7_30.1
 // CHECK:STDOUT:   %foo_short__carbon_thunk.call: init %empty_tuple.type = call imports.%foo_short__carbon_thunk.decl(%addr)
-// CHECK:STDOUT:   %.loc7_30.2: init %i16 = in_place_init %foo_short__carbon_thunk.call, %.loc7_30.1
+// CHECK:STDOUT:   %.loc7_30.2: init %i16 to %.loc7_30.1 = mark_in_place_init %foo_short__carbon_thunk.call
 // CHECK:STDOUT:   %.loc7_10: type = splice_block %i16 [concrete = constants.%i16] {
 // CHECK:STDOUT:     %int_16: Core.IntLiteral = int_value 16 [concrete = constants.%int_16]
 // CHECK:STDOUT:     %i16: type = class_type @Int, @Int(constants.%int_16) [concrete = constants.%i16]
 // CHECK:STDOUT:   }
-// CHECK:STDOUT:   %.loc7_30.3: %i16 = value_of_initializer %.loc7_30.2
-// CHECK:STDOUT:   %.loc7_30.4: %i16 = converted %.loc7_30.2, %.loc7_30.3
+// CHECK:STDOUT:   %.loc7_30.3: ref %i16 = temporary %.loc7_30.1, %.loc7_30.2
+// CHECK:STDOUT:   %.loc7_30.4: %i16 = acquire_value %.loc7_30.3
 // CHECK:STDOUT:   %x: %i16 = value_binding x, %.loc7_30.4
+// CHECK:STDOUT:   %DestroyOp.bound: <bound method> = bound_method %.loc7_30.3, constants.%DestroyOp
+// CHECK:STDOUT:   %DestroyOp.call: init %empty_tuple.type = call %DestroyOp.bound(%.loc7_30.3)
 // CHECK:STDOUT:   return
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
@@ -374,3 +381,5 @@ fn F() {
 // CHECK:STDOUT:
 // CHECK:STDOUT: fn @foo_short__carbon_thunk(%return.param: %ptr);
 // CHECK:STDOUT:
+// CHECK:STDOUT: fn @DestroyOp(%self.param: %i16) = "no_op";
+// CHECK:STDOUT:
diff --git a/toolchain/check/testdata/interop/cpp/function/inline.carbon b/toolchain/check/testdata/interop/cpp/function/inline.carbon
index 043b6de2a36e..8d8f01188836 100644
--- a/toolchain/check/testdata/interop/cpp/function/inline.carbon
+++ b/toolchain/check/testdata/interop/cpp/function/inline.carbon
@@ -319,13 +319,13 @@ fn MyF() {
 // CHECK:STDOUT:   %.loc15_36.1: ref %i16 = temporary_storage
 // CHECK:STDOUT:   %addr.loc15: %ptr.251 = addr_of %.loc15_36.1
 // CHECK:STDOUT:   %ThunkOnReturn__carbon_thunk.call: init %empty_tuple.type = call imports.%ThunkOnReturn__carbon_thunk.decl(%.loc15_35.2, %addr.loc15)
-// CHECK:STDOUT:   %.loc15_36.2: init %i16 = in_place_init %ThunkOnReturn__carbon_thunk.call, %.loc15_36.1
+// CHECK:STDOUT:   %.loc15_36.2: init %i16 to %.loc15_36.1 = mark_in_place_init %ThunkOnReturn__carbon_thunk.call
 // CHECK:STDOUT:   %.loc15_11: type = splice_block %i16.loc15 [concrete = constants.%i16] {
 // CHECK:STDOUT:     %int_16.loc15: Core.IntLiteral = int_value 16 [concrete = constants.%int_16]
 // CHECK:STDOUT:     %i16.loc15: type = class_type @Int, @Int(constants.%int_16) [concrete = constants.%i16]
 // CHECK:STDOUT:   }
-// CHECK:STDOUT:   %.loc15_36.3: %i16 = value_of_initializer %.loc15_36.2
-// CHECK:STDOUT:   %.loc15_36.4: %i16 = converted %.loc15_36.2, %.loc15_36.3
+// CHECK:STDOUT:   %.loc15_36.3: ref %i16 = temporary %.loc15_36.1, %.loc15_36.2
+// CHECK:STDOUT:   %.loc15_36.4: %i16 = acquire_value %.loc15_36.3
 // CHECK:STDOUT:   %r3: %i16 = value_binding r3, %.loc15_36.4
 // CHECK:STDOUT:   name_binding_decl {
 // CHECK:STDOUT:     %r4.patt: %pattern_type.2f8 = value_binding_pattern r4 [concrete]
@@ -351,16 +351,20 @@ fn MyF() {
 // CHECK:STDOUT:   %.loc16_34.1: ref %i16 = temporary_storage
 // CHECK:STDOUT:   %addr.loc16_34.2: %ptr.251 = addr_of %.loc16_34.1
 // CHECK:STDOUT:   %ThunkOnBoth__carbon_thunk.call: init %empty_tuple.type = call imports.%ThunkOnBoth__carbon_thunk.decl(%addr.loc16_34.1, %addr.loc16_34.2)
-// CHECK:STDOUT:   %.loc16_34.2: init %i16 = in_place_init %ThunkOnBoth__carbon_thunk.call, %.loc16_34.1
+// CHECK:STDOUT:   %.loc16_34.2: init %i16 to %.loc16_34.1 = mark_in_place_init %ThunkOnBoth__carbon_thunk.call
 // CHECK:STDOUT:   %.loc16_11: type = splice_block %i16.loc16 [concrete = constants.%i16] {
 // CHECK:STDOUT:     %int_16.loc16: Core.IntLiteral = int_value 16 [concrete = constants.%int_16]
 // CHECK:STDOUT:     %i16.loc16: type = class_type @Int, @Int(constants.%int_16) [concrete = constants.%i16]
 // CHECK:STDOUT:   }
-// CHECK:STDOUT:   %.loc16_34.3: %i16 = value_of_initializer %.loc16_34.2
-// CHECK:STDOUT:   %.loc16_34.4: %i16 = converted %.loc16_34.2, %.loc16_34.3
+// CHECK:STDOUT:   %.loc16_34.3: ref %i16 = temporary %.loc16_34.1, %.loc16_34.2
+// CHECK:STDOUT:   %.loc16_34.4: %i16 = acquire_value %.loc16_34.3
 // CHECK:STDOUT:   %r4: %i16 = value_binding r4, %.loc16_34.4
-// CHECK:STDOUT:   %DestroyOp.bound.loc16: <bound method> = bound_method %.loc16_33.4, constants.%DestroyOp
-// CHECK:STDOUT:   %DestroyOp.call.loc16: init %empty_tuple.type = call %DestroyOp.bound.loc16(%.loc16_33.4)
+// CHECK:STDOUT:   %DestroyOp.bound.loc16_34: <bound method> = bound_method %.loc16_34.3, constants.%DestroyOp
+// CHECK:STDOUT:   %DestroyOp.call.loc16_34: init %empty_tuple.type = call %DestroyOp.bound.loc16_34(%.loc16_34.3)
+// CHECK:STDOUT:   %DestroyOp.bound.loc16_33: <bound method> = bound_method %.loc16_33.4, constants.%DestroyOp
+// CHECK:STDOUT:   %DestroyOp.call.loc16_33: init %empty_tuple.type = call %DestroyOp.bound.loc16_33(%.loc16_33.4)
+// CHECK:STDOUT:   %DestroyOp.bound.loc15: <bound method> = bound_method %.loc15_36.3, constants.%DestroyOp
+// CHECK:STDOUT:   %DestroyOp.call.loc15: init %empty_tuple.type = call %DestroyOp.bound.loc15(%.loc15_36.3)
 // CHECK:STDOUT:   %DestroyOp.bound.loc14: <bound method> = bound_method %.loc14_32.4, constants.%DestroyOp
 // CHECK:STDOUT:   %DestroyOp.call.loc14: init %empty_tuple.type = call %DestroyOp.bound.loc14(%.loc14_32.4)
 // CHECK:STDOUT:   <elided>
diff --git a/toolchain/check/testdata/interop/cpp/function/operators.carbon b/toolchain/check/testdata/interop/cpp/function/operators.carbon
index 5578b64299a0..b9195bf0465b 100644
--- a/toolchain/check/testdata/interop/cpp/function/operators.carbon
+++ b/toolchain/check/testdata/interop/cpp/function/operators.carbon
@@ -1118,7 +1118,7 @@ fn F() {
 // CHECK:STDOUT:   %.loc8_3: ref %C = splice_block %c.var {}
 // CHECK:STDOUT:   %addr.loc8: %ptr.d9e = addr_of %.loc8_3
 // CHECK:STDOUT:   %C__carbon_thunk.call: init %empty_tuple.type = call imports.%C__carbon_thunk.decl(%addr.loc8)
-// CHECK:STDOUT:   %.loc8_26: init %C to %.loc8_3 = in_place_init %C__carbon_thunk.call
+// CHECK:STDOUT:   %.loc8_26: init %C to %.loc8_3 = mark_in_place_init %C__carbon_thunk.call
 // CHECK:STDOUT:   assign %c.var, %.loc8_26
 // CHECK:STDOUT:   %.loc8_13: type = splice_block %C.ref.loc8_13 [concrete = constants.%C] {
 // CHECK:STDOUT:     %Cpp.ref.loc8_10: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
@@ -1139,7 +1139,7 @@ fn F() {
 // CHECK:STDOUT:   %addr.loc15_22.1: %ptr.d9e = addr_of %.loc15_23.2
 // CHECK:STDOUT:   %addr.loc15_22.2: %ptr.d9e = addr_of %.loc15_22.1
 // CHECK:STDOUT:   %operator_Minus__carbon_thunk.call: init %empty_tuple.type = call imports.%operator_Minus__carbon_thunk.decl(%addr.loc15_22.1, %addr.loc15_22.2)
-// CHECK:STDOUT:   %.loc15_22.2: init %C to %.loc15_22.1 = in_place_init %operator_Minus__carbon_thunk.call
+// CHECK:STDOUT:   %.loc15_22.2: init %C to %.loc15_22.1 = mark_in_place_init %operator_Minus__carbon_thunk.call
 // CHECK:STDOUT:   %.loc15_17: type = splice_block %C.ref.loc15 [concrete = constants.%C] {
 // CHECK:STDOUT:     %Cpp.ref.loc15: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
 // CHECK:STDOUT:     %C.ref.loc15: type = name_ref C, imports.%C.decl [concrete = constants.%C]
@@ -1157,7 +1157,7 @@ fn F() {
 // CHECK:STDOUT:   %addr.loc18_27.1: %ptr.d9e = addr_of %.loc18_28.2
 // CHECK:STDOUT:   %addr.loc18_27.2: %ptr.d9e = addr_of %.loc18_27.1
 // CHECK:STDOUT:   %operator_Tilde__carbon_thunk.call: init %empty_tuple.type = call imports.%operator_Tilde__carbon_thunk.decl(%addr.loc18_27.1, %addr.loc18_27.2)
-// CHECK:STDOUT:   %.loc18_27.2: init %C to %.loc18_27.1 = in_place_init %operator_Tilde__carbon_thunk.call
+// CHECK:STDOUT:   %.loc18_27.2: init %C to %.loc18_27.1 = mark_in_place_init %operator_Tilde__carbon_thunk.call
 // CHECK:STDOUT:   %.loc18_22: type = splice_block %C.ref.loc18 [concrete = constants.%C] {
 // CHECK:STDOUT:     %Cpp.ref.loc18: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
 // CHECK:STDOUT:     %C.ref.loc18: type = name_ref C, imports.%C.decl [concrete = constants.%C]
@@ -1271,6 +1271,8 @@ fn F() {
 // CHECK:STDOUT:   %Core.IntLiteral.as.ImplicitAs.impl.Convert.bound.c83: <bound method> = bound_method %int_42.20e, %Core.IntLiteral.as.ImplicitAs.impl.Convert.0b5 [concrete]
 // CHECK:STDOUT:   %bound_method.cb9: <bound method> = bound_method %int_42.20e, %Core.IntLiteral.as.ImplicitAs.impl.Convert.specific_fn [concrete]
 // CHECK:STDOUT:   %int_42.c68: %i32 = int_value 42 [concrete]
+// CHECK:STDOUT:   %DestroyOp.type.3e79c2.1: type = fn_type @DestroyOp.loc45 [concrete]
+// CHECK:STDOUT:   %DestroyOp.b0ebf8.1: %DestroyOp.type.3e79c2.1 = struct_value () [concrete]
 // CHECK:STDOUT:   %C.cpp_destructor.type: type = fn_type @C.cpp_destructor [concrete]
 // CHECK:STDOUT:   %C.cpp_destructor: %C.cpp_destructor.type = struct_value () [concrete]
 // CHECK:STDOUT: }
@@ -1444,7 +1446,7 @@ fn F() {
 // CHECK:STDOUT:   %.loc8_3: ref %C = splice_block %c1.var {}
 // CHECK:STDOUT:   %addr.loc8: %ptr.d9e = addr_of %.loc8_3
 // CHECK:STDOUT:   %C__carbon_thunk.call.loc8: init %empty_tuple.type = call imports.%C__carbon_thunk.decl(%addr.loc8)
-// CHECK:STDOUT:   %.loc8_27: init %C to %.loc8_3 = in_place_init %C__carbon_thunk.call.loc8
+// CHECK:STDOUT:   %.loc8_27: init %C to %.loc8_3 = mark_in_place_init %C__carbon_thunk.call.loc8
 // CHECK:STDOUT:   assign %c1.var, %.loc8_27
 // CHECK:STDOUT:   %.loc8_14: type = splice_block %C.ref.loc8_14 [concrete = constants.%C] {
 // CHECK:STDOUT:     %Cpp.ref.loc8_11: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
@@ -1462,7 +1464,7 @@ fn F() {
 // CHECK:STDOUT:   %.loc9_3: ref %C = splice_block %c2.var {}
 // CHECK:STDOUT:   %addr.loc9: %ptr.d9e = addr_of %.loc9_3
 // CHECK:STDOUT:   %C__carbon_thunk.call.loc9: init %empty_tuple.type = call imports.%C__carbon_thunk.decl(%addr.loc9)
-// CHECK:STDOUT:   %.loc9_27: init %C to %.loc9_3 = in_place_init %C__carbon_thunk.call.loc9
+// CHECK:STDOUT:   %.loc9_27: init %C to %.loc9_3 = mark_in_place_init %C__carbon_thunk.call.loc9
 // CHECK:STDOUT:   assign %c2.var, %.loc9_27
 // CHECK:STDOUT:   %.loc9_14: type = splice_block %C.ref.loc9_14 [concrete = constants.%C] {
 // CHECK:STDOUT:     %Cpp.ref.loc9_11: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
@@ -1483,7 +1485,7 @@ fn F() {
 // CHECK:STDOUT:   %addr.loc12_28.2: %ptr.d9e = addr_of %.loc12_30.2
 // CHECK:STDOUT:   %addr.loc12_28.3: %ptr.d9e = addr_of %.loc12_28.1
 // CHECK:STDOUT:   %operator_Plus__carbon_thunk.call: init %empty_tuple.type = call imports.%operator_Plus__carbon_thunk.decl(%addr.loc12_28.1, %addr.loc12_28.2, %addr.loc12_28.3)
-// CHECK:STDOUT:   %.loc12_28.2: init %C to %.loc12_28.1 = in_place_init %operator_Plus__carbon_thunk.call
+// CHECK:STDOUT:   %.loc12_28.2: init %C to %.loc12_28.1 = mark_in_place_init %operator_Plus__carbon_thunk.call
 // CHECK:STDOUT:   %.loc12_20: type = splice_block %C.ref.loc12 [concrete = constants.%C] {
 // CHECK:STDOUT:     %Cpp.ref.loc12: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
 // CHECK:STDOUT:     %C.ref.loc12: type = name_ref C, imports.%C.decl [concrete = constants.%C]
@@ -1505,7 +1507,7 @@ fn F() {
 // CHECK:STDOUT:   %addr.loc13_31.2: %ptr.d9e = addr_of %.loc13_33.2
 // CHECK:STDOUT:   %addr.loc13_31.3: %ptr.d9e = addr_of %.loc13_31.1
 // CHECK:STDOUT:   %operator_Minus__carbon_thunk.call: init %empty_tuple.type = call imports.%operator_Minus__carbon_thunk.decl(%addr.loc13_31.1, %addr.loc13_31.2, %addr.loc13_31.3)
-// CHECK:STDOUT:   %.loc13_31.2: init %C to %.loc13_31.1 = in_place_init %operator_Minus__carbon_thunk.call
+// CHECK:STDOUT:   %.loc13_31.2: init %C to %.loc13_31.1 = mark_in_place_init %operator_Minus__carbon_thunk.call
 // CHECK:STDOUT:   %.loc13_23: type = splice_block %C.ref.loc13 [concrete = constants.%C] {
 // CHECK:STDOUT:     %Cpp.ref.loc13: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
 // CHECK:STDOUT:     %C.ref.loc13: type = name_ref C, imports.%C.decl [concrete = constants.%C]
@@ -1527,7 +1529,7 @@ fn F() {
 // CHECK:STDOUT:   %addr.loc14_34.2: %ptr.d9e = addr_of %.loc14_36.2
 // CHECK:STDOUT:   %addr.loc14_34.3: %ptr.d9e = addr_of %.loc14_34.1
 // CHECK:STDOUT:   %operator_Star__carbon_thunk.call: init %empty_tuple.type = call imports.%operator_Star__carbon_thunk.decl(%addr.loc14_34.1, %addr.loc14_34.2, %addr.loc14_34.3)
-// CHECK:STDOUT:   %.loc14_34.2: init %C to %.loc14_34.1 = in_place_init %operator_Star__carbon_thunk.call
+// CHECK:STDOUT:   %.loc14_34.2: init %C to %.loc14_34.1 = mark_in_place_init %operator_Star__carbon_thunk.call
 // CHECK:STDOUT:   %.loc14_26: type = splice_block %C.ref.loc14 [concrete = constants.%C] {
 // CHECK:STDOUT:     %Cpp.ref.loc14: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
 // CHECK:STDOUT:     %C.ref.loc14: type = name_ref C, imports.%C.decl [concrete = constants.%C]
@@ -1549,7 +1551,7 @@ fn F() {
 // CHECK:STDOUT:   %addr.loc15_28.2: %ptr.d9e = addr_of %.loc15_30.2
 // CHECK:STDOUT:   %addr.loc15_28.3: %ptr.d9e = addr_of %.loc15_28.1
 // CHECK:STDOUT:   %operator_Slash__carbon_thunk.call: init %empty_tuple.type = call imports.%operator_Slash__carbon_thunk.decl(%addr.loc15_28.1, %addr.loc15_28.2, %addr.loc15_28.3)
-// CHECK:STDOUT:   %.loc15_28.2: init %C to %.loc15_28.1 = in_place_init %operator_Slash__carbon_thunk.call
+// CHECK:STDOUT:   %.loc15_28.2: init %C to %.loc15_28.1 = mark_in_place_init %operator_Slash__carbon_thunk.call
 // CHECK:STDOUT:   %.loc15_20: type = splice_block %C.ref.loc15 [concrete = constants.%C] {
 // CHECK:STDOUT:     %Cpp.ref.loc15: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
 // CHECK:STDOUT:     %C.ref.loc15: type = name_ref C, imports.%C.decl [concrete = constants.%C]
@@ -1571,7 +1573,7 @@ fn F() {
 // CHECK:STDOUT:   %addr.loc16_26.2: %ptr.d9e = addr_of %.loc16_28.2
 // CHECK:STDOUT:   %addr.loc16_26.3: %ptr.d9e = addr_of %.loc16_26.1
 // CHECK:STDOUT:   %operator_Percent__carbon_thunk.call: init %empty_tuple.type = call imports.%operator_Percent__carbon_thunk.decl(%addr.loc16_26.1, %addr.loc16_26.2, %addr.loc16_26.3)
-// CHECK:STDOUT:   %.loc16_26.2: init %C to %.loc16_26.1 = in_place_init %operator_Percent__carbon_thunk.call
+// CHECK:STDOUT:   %.loc16_26.2: init %C to %.loc16_26.1 = mark_in_place_init %operator_Percent__carbon_thunk.call
 // CHECK:STDOUT:   %.loc16_18: type = splice_block %C.ref.loc16 [concrete = constants.%C] {
 // CHECK:STDOUT:     %Cpp.ref.loc16: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
 // CHECK:STDOUT:     %C.ref.loc16: type = name_ref C, imports.%C.decl [concrete = constants.%C]
@@ -1593,7 +1595,7 @@ fn F() {
 // CHECK:STDOUT:   %addr.loc19_31.2: %ptr.d9e = addr_of %.loc19_33.2
 // CHECK:STDOUT:   %addr.loc19_31.3: %ptr.d9e = addr_of %.loc19_31.1
 // CHECK:STDOUT:   %operator_Amp__carbon_thunk.call: init %empty_tuple.type = call imports.%operator_Amp__carbon_thunk.decl(%addr.loc19_31.1, %addr.loc19_31.2, %addr.loc19_31.3)
-// CHECK:STDOUT:   %.loc19_31.2: init %C to %.loc19_31.1 = in_place_init %operator_Amp__carbon_thunk.call
+// CHECK:STDOUT:   %.loc19_31.2: init %C to %.loc19_31.1 = mark_in_place_init %operator_Amp__carbon_thunk.call
 // CHECK:STDOUT:   %.loc19_23: type = splice_block %C.ref.loc19 [concrete = constants.%C] {
 // CHECK:STDOUT:     %Cpp.ref.loc19: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
 // CHECK:STDOUT:     %C.ref.loc19: type = name_ref C, imports.%C.decl [concrete = constants.%C]
@@ -1615,7 +1617,7 @@ fn F() {
 // CHECK:STDOUT:   %addr.loc20_30.2: %ptr.d9e = addr_of %.loc20_32.2
 // CHECK:STDOUT:   %addr.loc20_30.3: %ptr.d9e = addr_of %.loc20_30.1
 // CHECK:STDOUT:   %operator_Pipe__carbon_thunk.call: init %empty_tuple.type = call imports.%operator_Pipe__carbon_thunk.decl(%addr.loc20_30.1, %addr.loc20_30.2, %addr.loc20_30.3)
-// CHECK:STDOUT:   %.loc20_30.2: init %C to %.loc20_30.1 = in_place_init %operator_Pipe__carbon_thunk.call
+// CHECK:STDOUT:   %.loc20_30.2: init %C to %.loc20_30.1 = mark_in_place_init %operator_Pipe__carbon_thunk.call
 // CHECK:STDOUT:   %.loc20_22: type = splice_block %C.ref.loc20 [concrete = constants.%C] {
 // CHECK:STDOUT:     %Cpp.ref.loc20: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
 // CHECK:STDOUT:     %C.ref.loc20: type = name_ref C, imports.%C.decl [concrete = constants.%C]
@@ -1637,7 +1639,7 @@ fn F() {
 // CHECK:STDOUT:   %addr.loc21_31.2: %ptr.d9e = addr_of %.loc21_33.2
 // CHECK:STDOUT:   %addr.loc21_31.3: %ptr.d9e = addr_of %.loc21_31.1
 // CHECK:STDOUT:   %operator_Caret__carbon_thunk.call: init %empty_tuple.type = call imports.%operator_Caret__carbon_thunk.decl(%addr.loc21_31.1, %addr.loc21_31.2, %addr.loc21_31.3)
-// CHECK:STDOUT:   %.loc21_31.2: init %C to %.loc21_31.1 = in_place_init %operator_Caret__carbon_thunk.call
+// CHECK:STDOUT:   %.loc21_31.2: init %C to %.loc21_31.1 = mark_in_place_init %operator_Caret__carbon_thunk.call
 // CHECK:STDOUT:   %.loc21_23: type = splice_block %C.ref.loc21 [concrete = constants.%C] {
 // CHECK:STDOUT:     %Cpp.ref.loc21: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
 // CHECK:STDOUT:     %C.ref.loc21: type = name_ref C, imports.%C.decl [concrete = constants.%C]
@@ -1663,7 +1665,7 @@ fn F() {
 // CHECK:STDOUT:   %addr.loc22_30.1: %ptr.d9e = addr_of %.loc22_27.2
 // CHECK:STDOUT:   %addr.loc22_30.2: %ptr.d9e = addr_of %.loc22_30.1
 // CHECK:STDOUT:   %operator_LessLess__carbon_thunk.call: init %empty_tuple.type = call imports.%operator_LessLess__carbon_thunk.decl(%addr.loc22_30.1, %.loc22_33.2, %addr.loc22_30.2)
-// CHECK:STDOUT:   %.loc22_30.2: init %C to %.loc22_30.1 = in_place_init %operator_LessLess__carbon_thunk.call
+// CHECK:STDOUT:   %.loc22_30.2: init %C to %.loc22_30.1 = mark_in_place_init %operator_LessLess__carbon_thunk.call
 // CHECK:STDOUT:   %.loc22_22: type = splice_block %C.ref.loc22 [concrete = constants.%C] {
 // CHECK:STDOUT:     %Cpp.ref.loc22: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
 // CHECK:STDOUT:     %C.ref.loc22: type = name_ref C, imports.%C.decl [concrete = constants.%C]
@@ -1689,7 +1691,7 @@ fn F() {
 // CHECK:STDOUT:   %addr.loc23_31.1: %ptr.d9e = addr_of %.loc23_28.2
 // CHECK:STDOUT:   %addr.loc23_31.2: %ptr.d9e = addr_of %.loc23_31.1
 // CHECK:STDOUT:   %operator_GreaterGreater__carbon_thunk.call: init %empty_tuple.type = call imports.%operator_GreaterGreater__carbon_thunk.decl(%addr.loc23_31.1, %.loc23_34.2, %addr.loc23_31.2)
-// CHECK:STDOUT:   %.loc23_31.2: init %C to %.loc23_31.1 = in_place_init %operator_GreaterGreater__carbon_thunk.call
+// CHECK:STDOUT:   %.loc23_31.2: init %C to %.loc23_31.1 = mark_in_place_init %operator_GreaterGreater__carbon_thunk.call
 // CHECK:STDOUT:   %.loc23_23: type = splice_block %C.ref.loc23 [concrete = constants.%C] {
 // CHECK:STDOUT:     %Cpp.ref.loc23: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
 // CHECK:STDOUT:     %C.ref.loc23: type = name_ref C, imports.%C.decl [concrete = constants.%C]
@@ -1779,14 +1781,14 @@ fn F() {
 // CHECK:STDOUT:   %.loc40_24.1: ref bool = temporary_storage
 // CHECK:STDOUT:   %addr.loc40_24.3: %ptr.bb2 = addr_of %.loc40_24.1
 // CHECK:STDOUT:   %operator_EqualEqual__carbon_thunk.call: init %empty_tuple.type = call imports.%operator_EqualEqual__carbon_thunk.decl(%addr.loc40_24.1, %addr.loc40_24.2, %addr.loc40_24.3)
-// CHECK:STDOUT:   %.loc40_24.2: init bool = in_place_init %operator_EqualEqual__carbon_thunk.call, %.loc40_24.1
+// CHECK:STDOUT:   %.loc40_24.2: init bool to %.loc40_24.1 = mark_in_place_init %operator_EqualEqual__carbon_thunk.call
 // CHECK:STDOUT:   %.loc40_14.1: type = splice_block %.loc40_14.3 [concrete = bool] {
 // CHECK:STDOUT:     %Bool.call.loc40: init type = call constants.%Bool() [concrete = bool]
 // CHECK:STDOUT:     %.loc40_14.2: type = value_of_initializer %Bool.call.loc40 [concrete = bool]
 // CHECK:STDOUT:     %.loc40_14.3: type = converted %Bool.call.loc40, %.loc40_14.2 [concrete = bool]
 // CHECK:STDOUT:   }
-// CHECK:STDOUT:   %.loc40_24.3: bool = value_of_initializer %.loc40_24.2
-// CHECK:STDOUT:   %.loc40_24.4: bool = converted %.loc40_24.2, %.loc40_24.3
+// CHECK:STDOUT:   %.loc40_24.3: ref bool = temporary %.loc40_24.1, %.loc40_24.2
+// CHECK:STDOUT:   %.loc40_24.4: bool = acquire_value %.loc40_24.3
 // CHECK:STDOUT:   %equal: bool = value_binding equal, %.loc40_24.4
 // CHECK:STDOUT:   name_binding_decl {
 // CHECK:STDOUT:     %not_equal.patt: %pattern_type.831 = value_binding_pattern not_equal [concrete]
@@ -1802,14 +1804,14 @@ fn F() {
 // CHECK:STDOUT:   %.loc41_28.1: ref bool = temporary_storage
 // CHECK:STDOUT:   %addr.loc41_28.3: %ptr.bb2 = addr_of %.loc41_28.1
 // CHECK:STDOUT:   %operator_ExclaimEqual__carbon_thunk.call: init %empty_tuple.type = call imports.%operator_ExclaimEqual__carbon_thunk.decl(%addr.loc41_28.1, %addr.loc41_28.2, %addr.loc41_28.3)
-// CHECK:STDOUT:   %.loc41_28.2: init bool = in_place_init %operator_ExclaimEqual__carbon_thunk.call, %.loc41_28.1
+// CHECK:STDOUT:   %.loc41_28.2: init bool to %.loc41_28.1 = mark_in_place_init %operator_ExclaimEqual__carbon_thunk.call
 // CHECK:STDOUT:   %.loc41_18.1: type = splice_block %.loc41_18.3 [concrete = bool] {
 // CHECK:STDOUT:     %Bool.call.loc41: init type = call constants.%Bool() [concrete = bool]
 // CHECK:STDOUT:     %.loc41_18.2: type = value_of_initializer %Bool.call.loc41 [concrete = bool]
 // CHECK:STDOUT:     %.loc41_18.3: type = converted %Bool.call.loc41, %.loc41_18.2 [concrete = bool]
 // CHECK:STDOUT:   }
-// CHECK:STDOUT:   %.loc41_28.3: bool = value_of_initializer %.loc41_28.2
-// CHECK:STDOUT:   %.loc41_28.4: bool = converted %.loc41_28.2, %.loc41_28.3
+// CHECK:STDOUT:   %.loc41_28.3: ref bool = temporary %.loc41_28.1, %.loc41_28.2
+// CHECK:STDOUT:   %.loc41_28.4: bool = acquire_value %.loc41_28.3
 // CHECK:STDOUT:   %not_equal: bool = value_binding not_equal, %.loc41_28.4
 // CHECK:STDOUT:   name_binding_decl {
 // CHECK:STDOUT:     %greater_than.patt: %pattern_type.831 = value_binding_pattern greater_than [concrete]
@@ -1825,14 +1827,14 @@ fn F() {
 // CHECK:STDOUT:   %.loc42_31.1: ref bool = temporary_storage
 // CHECK:STDOUT:   %addr.loc42_31.3: %ptr.bb2 = addr_of %.loc42_31.1
 // CHECK:STDOUT:   %operator_Greater__carbon_thunk.call: init %empty_tuple.type = call imports.%operator_Greater__carbon_thunk.decl(%addr.loc42_31.1, %addr.loc42_31.2, %addr.loc42_31.3)
-// CHECK:STDOUT:   %.loc42_31.2: init bool = in_place_init %operator_Greater__carbon_thunk.call, %.loc42_31.1
+// CHECK:STDOUT:   %.loc42_31.2: init bool to %.loc42_31.1 = mark_in_place_init %operator_Greater__carbon_thunk.call
 // CHECK:STDOUT:   %.loc42_21.1: type = splice_block %.loc42_21.3 [concrete = bool] {
 // CHECK:STDOUT:     %Bool.call.loc42: init type = call constants.%Bool() [concrete = bool]
 // CHECK:STDOUT:     %.loc42_21.2: type = value_of_initializer %Bool.call.loc42 [concrete = bool]
 // CHECK:STDOUT:     %.loc42_21.3: type = converted %Bool.call.loc42, %.loc42_21.2 [concrete = bool]
 // CHECK:STDOUT:   }
-// CHECK:STDOUT:   %.loc42_31.3: bool = value_of_initializer %.loc42_31.2
-// CHECK:STDOUT:   %.loc42_31.4: bool = converted %.loc42_31.2, %.loc42_31.3
+// CHECK:STDOUT:   %.loc42_31.3: ref bool = temporary %.loc42_31.1, %.loc42_31.2
+// CHECK:STDOUT:   %.loc42_31.4: bool = acquire_value %.loc42_31.3
 // CHECK:STDOUT:   %greater_than: bool = value_binding greater_than, %.loc42_31.4
 // CHECK:STDOUT:   name_binding_decl {
 // CHECK:STDOUT:     %less_than.patt: %pattern_type.831 = value_binding_pattern less_than [concrete]
@@ -1848,14 +1850,14 @@ fn F() {
 // CHECK:STDOUT:   %.loc43_28.1: ref bool = temporary_storage
 // CHECK:STDOUT:   %addr.loc43_28.3: %ptr.bb2 = addr_of %.loc43_28.1
 // CHECK:STDOUT:   %operator_Less__carbon_thunk.call: init %empty_tuple.type = call imports.%operator_Less__carbon_thunk.decl(%addr.loc43_28.1, %addr.loc43_28.2, %addr.loc43_28.3)
-// CHECK:STDOUT:   %.loc43_28.2: init bool = in_place_init %operator_Less__carbon_thunk.call, %.loc43_28.1
+// CHECK:STDOUT:   %.loc43_28.2: init bool to %.loc43_28.1 = mark_in_place_init %operator_Less__carbon_thunk.call
 // CHECK:STDOUT:   %.loc43_18.1: type = splice_block %.loc43_18.3 [concrete = bool] {
 // CHECK:STDOUT:     %Bool.call.loc43: init type = call constants.%Bool() [concrete = bool]
 // CHECK:STDOUT:     %.loc43_18.2: type = value_of_initializer %Bool.call.loc43 [concrete = bool]
 // CHECK:STDOUT:     %.loc43_18.3: type = converted %Bool.call.loc43, %.loc43_18.2 [concrete = bool]
 // CHECK:STDOUT:   }
-// CHECK:STDOUT:   %.loc43_28.3: bool = value_of_initializer %.loc43_28.2
-// CHECK:STDOUT:   %.loc43_28.4: bool = converted %.loc43_28.2, %.loc43_28.3
+// CHECK:STDOUT:   %.loc43_28.3: ref bool = temporary %.loc43_28.1, %.loc43_28.2
+// CHECK:STDOUT:   %.loc43_28.4: bool = acquire_value %.loc43_28.3
 // CHECK:STDOUT:   %less_than: bool = value_binding less_than, %.loc43_28.4
 // CHECK:STDOUT:   name_binding_decl {
 // CHECK:STDOUT:     %greater_than_or_equal.patt: %pattern_type.831 = value_binding_pattern greater_than_or_equal [concrete]
@@ -1871,14 +1873,14 @@ fn F() {
 // CHECK:STDOUT:   %.loc44_40.1: ref bool = temporary_storage
 // CHECK:STDOUT:   %addr.loc44_40.3: %ptr.bb2 = addr_of %.loc44_40.1
 // CHECK:STDOUT:   %operator_GreaterEqual__carbon_thunk.call: init %empty_tuple.type = call imports.%operator_GreaterEqual__carbon_thunk.decl(%addr.loc44_40.1, %addr.loc44_40.2, %addr.loc44_40.3)
-// CHECK:STDOUT:   %.loc44_40.2: init bool = in_place_init %operator_GreaterEqual__carbon_thunk.call, %.loc44_40.1
+// CHECK:STDOUT:   %.loc44_40.2: init bool to %.loc44_40.1 = mark_in_place_init %operator_GreaterEqual__carbon_thunk.call
 // CHECK:STDOUT:   %.loc44_30.1: type = splice_block %.loc44_30.3 [concrete = bool] {
 // CHECK:STDOUT:     %Bool.call.loc44: init type = call constants.%Bool() [concrete = bool]
 // CHECK:STDOUT:     %.loc44_30.2: type = value_of_initializer %Bool.call.loc44 [concrete = bool]
 // CHECK:STDOUT:     %.loc44_30.3: type = converted %Bool.call.loc44, %.loc44_30.2 [concrete = bool]
 // CHECK:STDOUT:   }
-// CHECK:STDOUT:   %.loc44_40.3: bool = value_of_initializer %.loc44_40.2
-// CHECK:STDOUT:   %.loc44_40.4: bool = converted %.loc44_40.2, %.loc44_40.3
+// CHECK:STDOUT:   %.loc44_40.3: ref bool = temporary %.loc44_40.1, %.loc44_40.2
+// CHECK:STDOUT:   %.loc44_40.4: bool = acquire_value %.loc44_40.3
 // CHECK:STDOUT:   %greater_than_or_equal: bool = value_binding greater_than_or_equal, %.loc44_40.4
 // CHECK:STDOUT:   name_binding_decl {
 // CHECK:STDOUT:     %less_than_or_equal.patt: %pattern_type.831 = value_binding_pattern less_than_or_equal [concrete]
@@ -1894,14 +1896,14 @@ fn F() {
 // CHECK:STDOUT:   %.loc45_37.1: ref bool = temporary_storage
 // CHECK:STDOUT:   %addr.loc45_37.3: %ptr.bb2 = addr_of %.loc45_37.1
 // CHECK:STDOUT:   %operator_LessEqual__carbon_thunk.call: init %empty_tuple.type = call imports.%operator_LessEqual__carbon_thunk.decl(%addr.loc45_37.1, %addr.loc45_37.2, %addr.loc45_37.3)
-// CHECK:STDOUT:   %.loc45_37.2: init bool = in_place_init %operator_LessEqual__carbon_thunk.call, %.loc45_37.1
+// CHECK:STDOUT:   %.loc45_37.2: init bool to %.loc45_37.1 = mark_in_place_init %operator_LessEqual__carbon_thunk.call
 // CHECK:STDOUT:   %.loc45_27.1: type = splice_block %.loc45_27.3 [concrete = bool] {
 // CHECK:STDOUT:     %Bool.call.loc45: init type = call constants.%Bool() [concrete = bool]
 // CHECK:STDOUT:     %.loc45_27.2: type = value_of_initializer %Bool.call.loc45 [concrete = bool]
 // CHECK:STDOUT:     %.loc45_27.3: type = converted %Bool.call.loc45, %.loc45_27.2 [concrete = bool]
 // CHECK:STDOUT:   }
-// CHECK:STDOUT:   %.loc45_37.3: bool = value_of_initializer %.loc45_37.2
-// CHECK:STDOUT:   %.loc45_37.4: bool = converted %.loc45_37.2, %.loc45_37.3
+// CHECK:STDOUT:   %.loc45_37.3: ref bool = temporary %.loc45_37.1, %.loc45_37.2
+// CHECK:STDOUT:   %.loc45_37.4: bool = acquire_value %.loc45_37.3
 // CHECK:STDOUT:   %less_than_or_equal: bool = value_binding less_than_or_equal, %.loc45_37.4
 // CHECK:STDOUT:   name_binding_decl {
 // CHECK:STDOUT:     %index.patt: %pattern_type.7ce = value_binding_pattern index [concrete]
@@ -1924,6 +1926,18 @@ fn F() {
 // CHECK:STDOUT:   %.loc48_25.1: %i32 = value_of_initializer %C.cpp_operator.call
 // CHECK:STDOUT:   %.loc48_25.2: %i32 = converted %C.cpp_operator.call, %.loc48_25.1
 // CHECK:STDOUT:   %index: %i32 = value_binding index, %.loc48_25.2
+// CHECK:STDOUT:   %DestroyOp.bound.loc45: <bound method> = bound_method %.loc45_37.3, constants.%DestroyOp.b0ebf8.1
+// CHECK:STDOUT:   %DestroyOp.call.loc45: init %empty_tuple.type = call %DestroyOp.bound.loc45(%.loc45_37.3)
+// CHECK:STDOUT:   %DestroyOp.bound.loc44: <bound method> = bound_method %.loc44_40.3, constants.%DestroyOp.b0ebf8.1
+// CHECK:STDOUT:   %DestroyOp.call.loc44: init %empty_tuple.type = call %DestroyOp.bound.loc44(%.loc44_40.3)
+// CHECK:STDOUT:   %DestroyOp.bound.loc43: <bound method> = bound_method %.loc43_28.3, constants.%DestroyOp.b0ebf8.1
+// CHECK:STDOUT:   %DestroyOp.call.loc43: init %empty_tuple.type = call %DestroyOp.bound.loc43(%.loc43_28.3)
+// CHECK:STDOUT:   %DestroyOp.bound.loc42: <bound method> = bound_method %.loc42_31.3, constants.%DestroyOp.b0ebf8.1
+// CHECK:STDOUT:   %DestroyOp.call.loc42: init %empty_tuple.type = call %DestroyOp.bound.loc42(%.loc42_31.3)
+// CHECK:STDOUT:   %DestroyOp.bound.loc41: <bound method> = bound_method %.loc41_28.3, constants.%DestroyOp.b0ebf8.1
+// CHECK:STDOUT:   %DestroyOp.call.loc41: init %empty_tuple.type = call %DestroyOp.bound.loc41(%.loc41_28.3)
+// CHECK:STDOUT:   %DestroyOp.bound.loc40: <bound method> = bound_method %.loc40_24.3, constants.%DestroyOp.b0ebf8.1
+// CHECK:STDOUT:   %DestroyOp.call.loc40: init %empty_tuple.type = call %DestroyOp.bound.loc40(%.loc40_24.3)
 // CHECK:STDOUT:   %C.cpp_destructor.bound.loc23: <bound method> = bound_method %.loc23_31.3, constants.%C.cpp_destructor
 // CHECK:STDOUT:   %C.cpp_destructor.call.loc23: init %empty_tuple.type = call %C.cpp_destructor.bound.loc23(%.loc23_31.3)
 // CHECK:STDOUT:   %C.cpp_destructor.bound.loc22: <bound method> = bound_method %.loc22_30.3, constants.%C.cpp_destructor
@@ -1951,7 +1965,9 @@ fn F() {
 // CHECK:STDOUT:   <elided>
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
-// CHECK:STDOUT: fn @DestroyOp(%self.param: %C) = "no_op";
+// CHECK:STDOUT: fn @DestroyOp.loc45(%self.param: bool) = "no_op";
+// CHECK:STDOUT:
+// CHECK:STDOUT: fn @DestroyOp.loc23(%self.param: %C) = "no_op";
 // CHECK:STDOUT:
 // CHECK:STDOUT: --- multiple_calls.carbon
 // CHECK:STDOUT:
@@ -2000,7 +2016,7 @@ fn F() {
 // CHECK:STDOUT:   %.loc8_27.1: ref %C = temporary_storage
 // CHECK:STDOUT:   %addr.loc8: %ptr.d9e = addr_of %.loc8_27.1
 // CHECK:STDOUT:   %C__carbon_thunk.call.loc8: init %empty_tuple.type = call imports.%C__carbon_thunk.decl(%addr.loc8)
-// CHECK:STDOUT:   %.loc8_27.2: init %C to %.loc8_27.1 = in_place_init %C__carbon_thunk.call.loc8
+// CHECK:STDOUT:   %.loc8_27.2: init %C to %.loc8_27.1 = mark_in_place_init %C__carbon_thunk.call.loc8
 // CHECK:STDOUT:   %.loc8_14: type = splice_block %C.ref.loc8_14 [concrete = constants.%C] {
 // CHECK:STDOUT:     %Cpp.ref.loc8_11: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
 // CHECK:STDOUT:     %C.ref.loc8_14: type = name_ref C, imports.%C.decl [concrete = constants.%C]
@@ -2017,7 +2033,7 @@ fn F() {
 // CHECK:STDOUT:   %.loc9_27.1: ref %C = temporary_storage
 // CHECK:STDOUT:   %addr.loc9: %ptr.d9e = addr_of %.loc9_27.1
 // CHECK:STDOUT:   %C__carbon_thunk.call.loc9: init %empty_tuple.type = call imports.%C__carbon_thunk.decl(%addr.loc9)
-// CHECK:STDOUT:   %.loc9_27.2: init %C to %.loc9_27.1 = in_place_init %C__carbon_thunk.call.loc9
+// CHECK:STDOUT:   %.loc9_27.2: init %C to %.loc9_27.1 = mark_in_place_init %C__carbon_thunk.call.loc9
 // CHECK:STDOUT:   %.loc9_14: type = splice_block %C.ref.loc9_14 [concrete = constants.%C] {
 // CHECK:STDOUT:     %Cpp.ref.loc9_11: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
 // CHECK:STDOUT:     %C.ref.loc9_14: type = name_ref C, imports.%C.decl [concrete = constants.%C]
@@ -2037,7 +2053,7 @@ fn F() {
 // CHECK:STDOUT:   %addr.loc10_22.2: %ptr.d9e = addr_of %.loc10_24
 // CHECK:STDOUT:   %addr.loc10_22.3: %ptr.d9e = addr_of %.loc10_22.1
 // CHECK:STDOUT:   %operator_Plus__carbon_thunk.call.loc10: init %empty_tuple.type = call imports.%operator_Plus__carbon_thunk.decl(%addr.loc10_22.1, %addr.loc10_22.2, %addr.loc10_22.3)
-// CHECK:STDOUT:   %.loc10_22.2: init %C to %.loc10_22.1 = in_place_init %operator_Plus__carbon_thunk.call.loc10
+// CHECK:STDOUT:   %.loc10_22.2: init %C to %.loc10_22.1 = mark_in_place_init %operator_Plus__carbon_thunk.call.loc10
 // CHECK:STDOUT:   %.loc10_14: type = splice_block %C.ref.loc10 [concrete = constants.%C] {
 // CHECK:STDOUT:     %Cpp.ref.loc10: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
 // CHECK:STDOUT:     %C.ref.loc10: type = name_ref C, imports.%C.decl [concrete = constants.%C]
@@ -2057,7 +2073,7 @@ fn F() {
 // CHECK:STDOUT:   %addr.loc11_22.2: %ptr.d9e = addr_of %.loc11_24
 // CHECK:STDOUT:   %addr.loc11_22.3: %ptr.d9e = addr_of %.loc11_22.1
 // CHECK:STDOUT:   %operator_Plus__carbon_thunk.call.loc11: init %empty_tuple.type = call imports.%operator_Plus__carbon_thunk.decl(%addr.loc11_22.1, %addr.loc11_22.2, %addr.loc11_22.3)
-// CHECK:STDOUT:   %.loc11_22.2: init %C to %.loc11_22.1 = in_place_init %operator_Plus__carbon_thunk.call.loc11
+// CHECK:STDOUT:   %.loc11_22.2: init %C to %.loc11_22.1 = mark_in_place_init %operator_Plus__carbon_thunk.call.loc11
 // CHECK:STDOUT:   %.loc11_14: type = splice_block %C.ref.loc11 [concrete = constants.%C] {
 // CHECK:STDOUT:     %Cpp.ref.loc11: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
 // CHECK:STDOUT:     %C.ref.loc11: type = name_ref C, imports.%C.decl [concrete = constants.%C]
@@ -2077,7 +2093,7 @@ fn F() {
 // CHECK:STDOUT:   %addr.loc12_22.2: %ptr.d9e = addr_of %.loc12_24
 // CHECK:STDOUT:   %addr.loc12_22.3: %ptr.d9e = addr_of %.loc12_22.1
 // CHECK:STDOUT:   %operator_Plus__carbon_thunk.call.loc12: init %empty_tuple.type = call imports.%operator_Plus__carbon_thunk.decl(%addr.loc12_22.1, %addr.loc12_22.2, %addr.loc12_22.3)
-// CHECK:STDOUT:   %.loc12_22.2: init %C to %.loc12_22.1 = in_place_init %operator_Plus__carbon_thunk.call.loc12
+// CHECK:STDOUT:   %.loc12_22.2: init %C to %.loc12_22.1 = mark_in_place_init %operator_Plus__carbon_thunk.call.loc12
 // CHECK:STDOUT:   %.loc12_14: type = splice_block %C.ref.loc12 [concrete = constants.%C] {
 // CHECK:STDOUT:     %Cpp.ref.loc12: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
 // CHECK:STDOUT:     %C.ref.loc12: type = name_ref C, imports.%C.decl [concrete = constants.%C]
@@ -2119,6 +2135,8 @@ fn F() {
 // CHECK:STDOUT:   %operator_Greater__carbon_thunk: %operator_Greater__carbon_thunk.type = struct_value () [concrete]
 // CHECK:STDOUT:   %operator_LessEqual__carbon_thunk.type: type = fn_type @operator_LessEqual__carbon_thunk [concrete]
 // CHECK:STDOUT:   %operator_LessEqual__carbon_thunk: %operator_LessEqual__carbon_thunk.type = struct_value () [concrete]
+// CHECK:STDOUT:   %DestroyOp.type.3e79c2.1: type = fn_type @DestroyOp.loc36 [concrete]
+// CHECK:STDOUT:   %DestroyOp.b0ebf8.1: %DestroyOp.type.3e79c2.1 = struct_value () [concrete]
 // CHECK:STDOUT:   %C.cpp_destructor.type: type = fn_type @C.cpp_destructor [concrete]
 // CHECK:STDOUT:   %C.cpp_destructor: %C.cpp_destructor.type = struct_value () [concrete]
 // CHECK:STDOUT: }
@@ -2160,7 +2178,7 @@ fn F() {
 // CHECK:STDOUT:   %.loc15_3: ref %C = splice_block %c1.var {}
 // CHECK:STDOUT:   %addr.loc15: %ptr.d9e = addr_of %.loc15_3
 // CHECK:STDOUT:   %C__carbon_thunk.call.loc15: init %empty_tuple.type = call imports.%C__carbon_thunk.decl(%addr.loc15)
-// CHECK:STDOUT:   %.loc15_27: init %C to %.loc15_3 = in_place_init %C__carbon_thunk.call.loc15
+// CHECK:STDOUT:   %.loc15_27: init %C to %.loc15_3 = mark_in_place_init %C__carbon_thunk.call.loc15
 // CHECK:STDOUT:   assign %c1.var, %.loc15_27
 // CHECK:STDOUT:   %.loc15_14: type = splice_block %C.ref.loc15_14 [concrete = constants.%C] {
 // CHECK:STDOUT:     %Cpp.ref.loc15_11: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
@@ -2178,7 +2196,7 @@ fn F() {
 // CHECK:STDOUT:   %.loc16_3: ref %C = splice_block %c2.var {}
 // CHECK:STDOUT:   %addr.loc16: %ptr.d9e = addr_of %.loc16_3
 // CHECK:STDOUT:   %C__carbon_thunk.call.loc16: init %empty_tuple.type = call imports.%C__carbon_thunk.decl(%addr.loc16)
-// CHECK:STDOUT:   %.loc16_27: init %C to %.loc16_3 = in_place_init %C__carbon_thunk.call.loc16
+// CHECK:STDOUT:   %.loc16_27: init %C to %.loc16_3 = mark_in_place_init %C__carbon_thunk.call.loc16
 // CHECK:STDOUT:   assign %c2.var, %.loc16_27
 // CHECK:STDOUT:   %.loc16_14: type = splice_block %C.ref.loc16_14 [concrete = constants.%C] {
 // CHECK:STDOUT:     %Cpp.ref.loc16_11: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
@@ -2199,14 +2217,14 @@ fn F() {
 // CHECK:STDOUT:   %.loc19_31.1: ref bool = temporary_storage
 // CHECK:STDOUT:   %addr.loc19_31.3: %ptr.bb2 = addr_of %.loc19_31.1
 // CHECK:STDOUT:   %operator_Greater__carbon_thunk.call: init %empty_tuple.type = call imports.%operator_Greater__carbon_thunk.decl(%addr.loc19_31.1, %addr.loc19_31.2, %addr.loc19_31.3)
-// CHECK:STDOUT:   %.loc19_31.2: init bool = in_place_init %operator_Greater__carbon_thunk.call, %.loc19_31.1
+// CHECK:STDOUT:   %.loc19_31.2: init bool to %.loc19_31.1 = mark_in_place_init %operator_Greater__carbon_thunk.call
 // CHECK:STDOUT:   %.loc19_21.1: type = splice_block %.loc19_21.3 [concrete = bool] {
 // CHECK:STDOUT:     %Bool.call.loc19: init type = call constants.%Bool() [concrete = bool]
 // CHECK:STDOUT:     %.loc19_21.2: type = value_of_initializer %Bool.call.loc19 [concrete = bool]
 // CHECK:STDOUT:     %.loc19_21.3: type = converted %Bool.call.loc19, %.loc19_21.2 [concrete = bool]
 // CHECK:STDOUT:   }
-// CHECK:STDOUT:   %.loc19_31.3: bool = value_of_initializer %.loc19_31.2
-// CHECK:STDOUT:   %.loc19_31.4: bool = converted %.loc19_31.2, %.loc19_31.3
+// CHECK:STDOUT:   %.loc19_31.3: ref bool = temporary %.loc19_31.1, %.loc19_31.2
+// CHECK:STDOUT:   %.loc19_31.4: bool = acquire_value %.loc19_31.3
 // CHECK:STDOUT:   %greater_than: bool = value_binding greater_than, %.loc19_31.4
 // CHECK:STDOUT:   name_binding_decl {
 // CHECK:STDOUT:     %less_than.patt: %pattern_type.831 = value_binding_pattern less_than [concrete]
@@ -2244,15 +2262,19 @@ fn F() {
 // CHECK:STDOUT:   %.loc36_37.1: ref bool = temporary_storage
 // CHECK:STDOUT:   %addr.loc36_37.3: %ptr.bb2 = addr_of %.loc36_37.1
 // CHECK:STDOUT:   %operator_LessEqual__carbon_thunk.call: init %empty_tuple.type = call imports.%operator_LessEqual__carbon_thunk.decl(%addr.loc36_37.1, %addr.loc36_37.2, %addr.loc36_37.3)
-// CHECK:STDOUT:   %.loc36_37.2: init bool = in_place_init %operator_LessEqual__carbon_thunk.call, %.loc36_37.1
+// CHECK:STDOUT:   %.loc36_37.2: init bool to %.loc36_37.1 = mark_in_place_init %operator_LessEqual__carbon_thunk.call
 // CHECK:STDOUT:   %.loc36_27.1: type = splice_block %.loc36_27.3 [concrete = bool] {
 // CHECK:STDOUT:     %Bool.call.loc36: init type = call constants.%Bool() [concrete = bool]
 // CHECK:STDOUT:     %.loc36_27.2: type = value_of_initializer %Bool.call.loc36 [concrete = bool]
 // CHECK:STDOUT:     %.loc36_27.3: type = converted %Bool.call.loc36, %.loc36_27.2 [concrete = bool]
 // CHECK:STDOUT:   }
-// CHECK:STDOUT:   %.loc36_37.3: bool = value_of_initializer %.loc36_37.2
-// CHECK:STDOUT:   %.loc36_37.4: bool = converted %.loc36_37.2, %.loc36_37.3
+// CHECK:STDOUT:   %.loc36_37.3: ref bool = temporary %.loc36_37.1, %.loc36_37.2
+// CHECK:STDOUT:   %.loc36_37.4: bool = acquire_value %.loc36_37.3
 // CHECK:STDOUT:   %less_than_or_equal: bool = value_binding less_than_or_equal, %.loc36_37.4
+// CHECK:STDOUT:   %DestroyOp.bound.loc36: <bound method> = bound_method %.loc36_37.3, constants.%DestroyOp.b0ebf8.1
+// CHECK:STDOUT:   %DestroyOp.call.loc36: init %empty_tuple.type = call %DestroyOp.bound.loc36(%.loc36_37.3)
+// CHECK:STDOUT:   %DestroyOp.bound.loc19: <bound method> = bound_method %.loc19_31.3, constants.%DestroyOp.b0ebf8.1
+// CHECK:STDOUT:   %DestroyOp.call.loc19: init %empty_tuple.type = call %DestroyOp.bound.loc19(%.loc19_31.3)
 // CHECK:STDOUT:   %C.cpp_destructor.bound.loc16: <bound method> = bound_method %c2.var, constants.%C.cpp_destructor
 // CHECK:STDOUT:   %C.cpp_destructor.call.loc16: init %empty_tuple.type = call %C.cpp_destructor.bound.loc16(%c2.var)
 // CHECK:STDOUT:   %C.cpp_destructor.bound.loc15: <bound method> = bound_method %c1.var, constants.%C.cpp_destructor
@@ -2260,7 +2282,9 @@ fn F() {
 // CHECK:STDOUT:   <elided>
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
-// CHECK:STDOUT: fn @DestroyOp(%self.param: %C) = "no_op";
+// CHECK:STDOUT: fn @DestroyOp.loc36(%self.param: bool) = "no_op";
+// CHECK:STDOUT:
+// CHECK:STDOUT: fn @DestroyOp.loc16(%self.param: %C) = "no_op";
 // CHECK:STDOUT:
 // CHECK:STDOUT: --- fail_todo_rewrite_equal.carbon
 // CHECK:STDOUT:
@@ -2279,6 +2303,8 @@ fn F() {
 // CHECK:STDOUT:   %ptr.bb2: type = ptr_type bool [concrete]
 // CHECK:STDOUT:   %operator_EqualEqual__carbon_thunk.type: type = fn_type @operator_EqualEqual__carbon_thunk [concrete]
 // CHECK:STDOUT:   %operator_EqualEqual__carbon_thunk: %operator_EqualEqual__carbon_thunk.type = struct_value () [concrete]
+// CHECK:STDOUT:   %DestroyOp.type.3e79c2.1: type = fn_type @DestroyOp.loc16 [concrete]
+// CHECK:STDOUT:   %DestroyOp.b0ebf8.1: %DestroyOp.type.3e79c2.1 = struct_value () [concrete]
 // CHECK:STDOUT:   %C.cpp_destructor.type: type = fn_type @C.cpp_destructor [concrete]
 // CHECK:STDOUT:   %C.cpp_destructor: %C.cpp_destructor.type = struct_value () [concrete]
 // CHECK:STDOUT: }
@@ -2315,7 +2341,7 @@ fn F() {
 // CHECK:STDOUT:   %.loc12_3: ref %C = splice_block %c1.var {}
 // CHECK:STDOUT:   %addr.loc12: %ptr.d9e = addr_of %.loc12_3
 // CHECK:STDOUT:   %C__carbon_thunk.call.loc12: init %empty_tuple.type = call imports.%C__carbon_thunk.decl(%addr.loc12)
-// CHECK:STDOUT:   %.loc12_27: init %C to %.loc12_3 = in_place_init %C__carbon_thunk.call.loc12
+// CHECK:STDOUT:   %.loc12_27: init %C to %.loc12_3 = mark_in_place_init %C__carbon_thunk.call.loc12
 // CHECK:STDOUT:   assign %c1.var, %.loc12_27
 // CHECK:STDOUT:   %.loc12_14: type = splice_block %C.ref.loc12_14 [concrete = constants.%C] {
 // CHECK:STDOUT:     %Cpp.ref.loc12_11: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
@@ -2333,7 +2359,7 @@ fn F() {
 // CHECK:STDOUT:   %.loc13_3: ref %C = splice_block %c2.var {}
 // CHECK:STDOUT:   %addr.loc13: %ptr.d9e = addr_of %.loc13_3
 // CHECK:STDOUT:   %C__carbon_thunk.call.loc13: init %empty_tuple.type = call imports.%C__carbon_thunk.decl(%addr.loc13)
-// CHECK:STDOUT:   %.loc13_27: init %C to %.loc13_3 = in_place_init %C__carbon_thunk.call.loc13
+// CHECK:STDOUT:   %.loc13_27: init %C to %.loc13_3 = mark_in_place_init %C__carbon_thunk.call.loc13
 // CHECK:STDOUT:   assign %c2.var, %.loc13_27
 // CHECK:STDOUT:   %.loc13_14: type = splice_block %C.ref.loc13_14 [concrete = constants.%C] {
 // CHECK:STDOUT:     %Cpp.ref.loc13_11: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
@@ -2354,14 +2380,14 @@ fn F() {
 // CHECK:STDOUT:   %.loc16_24.1: ref bool = temporary_storage
 // CHECK:STDOUT:   %addr.loc16_24.3: %ptr.bb2 = addr_of %.loc16_24.1
 // CHECK:STDOUT:   %operator_EqualEqual__carbon_thunk.call: init %empty_tuple.type = call imports.%operator_EqualEqual__carbon_thunk.decl(%addr.loc16_24.1, %addr.loc16_24.2, %addr.loc16_24.3)
-// CHECK:STDOUT:   %.loc16_24.2: init bool = in_place_init %operator_EqualEqual__carbon_thunk.call, %.loc16_24.1
+// CHECK:STDOUT:   %.loc16_24.2: init bool to %.loc16_24.1 = mark_in_place_init %operator_EqualEqual__carbon_thunk.call
 // CHECK:STDOUT:   %.loc16_14.1: type = splice_block %.loc16_14.3 [concrete = bool] {
 // CHECK:STDOUT:     %Bool.call.loc16: init type = call constants.%Bool() [concrete = bool]
 // CHECK:STDOUT:     %.loc16_14.2: type = value_of_initializer %Bool.call.loc16 [concrete = bool]
 // CHECK:STDOUT:     %.loc16_14.3: type = converted %Bool.call.loc16, %.loc16_14.2 [concrete = bool]
 // CHECK:STDOUT:   }
-// CHECK:STDOUT:   %.loc16_24.3: bool = value_of_initializer %.loc16_24.2
-// CHECK:STDOUT:   %.loc16_24.4: bool = converted %.loc16_24.2, %.loc16_24.3
+// CHECK:STDOUT:   %.loc16_24.3: ref bool = temporary %.loc16_24.1, %.loc16_24.2
+// CHECK:STDOUT:   %.loc16_24.4: bool = acquire_value %.loc16_24.3
 // CHECK:STDOUT:   %equal: bool = value_binding equal, %.loc16_24.4
 // CHECK:STDOUT:   name_binding_decl {
 // CHECK:STDOUT:     %not_equal.patt: %pattern_type.831 = value_binding_pattern not_equal [concrete]
@@ -2374,6 +2400,8 @@ fn F() {
 // CHECK:STDOUT:     %.loc23_18.3: type = converted %Bool.call.loc23, %.loc23_18.2 [concrete = bool]
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %not_equal: bool = value_binding not_equal, <error> [concrete = <error>]
+// CHECK:STDOUT:   %DestroyOp.bound: <bound method> = bound_method %.loc16_24.3, constants.%DestroyOp.b0ebf8.1
+// CHECK:STDOUT:   %DestroyOp.call: init %empty_tuple.type = call %DestroyOp.bound(%.loc16_24.3)
 // CHECK:STDOUT:   %C.cpp_destructor.bound.loc13: <bound method> = bound_method %c2.var, constants.%C.cpp_destructor
 // CHECK:STDOUT:   %C.cpp_destructor.call.loc13: init %empty_tuple.type = call %C.cpp_destructor.bound.loc13(%c2.var)
 // CHECK:STDOUT:   %C.cpp_destructor.bound.loc12: <bound method> = bound_method %c1.var, constants.%C.cpp_destructor
@@ -2381,7 +2409,9 @@ fn F() {
 // CHECK:STDOUT:   <elided>
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
-// CHECK:STDOUT: fn @DestroyOp(%self.param: %C) = "no_op";
+// CHECK:STDOUT: fn @DestroyOp.loc16(%self.param: bool) = "no_op";
+// CHECK:STDOUT:
+// CHECK:STDOUT: fn @DestroyOp.loc13(%self.param: %C) = "no_op";
 // CHECK:STDOUT:
 // CHECK:STDOUT: --- import_single_namespace.carbon
 // CHECK:STDOUT:
@@ -2435,7 +2465,7 @@ fn F() {
 // CHECK:STDOUT:   %.loc8_31.1: ref %C = temporary_storage
 // CHECK:STDOUT:   %addr.loc8: %ptr.838 = addr_of %.loc8_31.1
 // CHECK:STDOUT:   %C__carbon_thunk.call.loc8: init %empty_tuple.type = call imports.%C__carbon_thunk.decl(%addr.loc8)
-// CHECK:STDOUT:   %.loc8_31.2: init %C to %.loc8_31.1 = in_place_init %C__carbon_thunk.call.loc8
+// CHECK:STDOUT:   %.loc8_31.2: init %C to %.loc8_31.1 = mark_in_place_init %C__carbon_thunk.call.loc8
 // CHECK:STDOUT:   %.loc8_16: type = splice_block %C.ref.loc8_16 [concrete = constants.%C] {
 // CHECK:STDOUT:     %Cpp.ref.loc8_11: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
 // CHECK:STDOUT:     %N.ref.loc8_14: <namespace> = name_ref N, imports.%N [concrete = imports.%N]
@@ -2454,7 +2484,7 @@ fn F() {
 // CHECK:STDOUT:   %.loc9_31.1: ref %C = temporary_storage
 // CHECK:STDOUT:   %addr.loc9: %ptr.838 = addr_of %.loc9_31.1
 // CHECK:STDOUT:   %C__carbon_thunk.call.loc9: init %empty_tuple.type = call imports.%C__carbon_thunk.decl(%addr.loc9)
-// CHECK:STDOUT:   %.loc9_31.2: init %C to %.loc9_31.1 = in_place_init %C__carbon_thunk.call.loc9
+// CHECK:STDOUT:   %.loc9_31.2: init %C to %.loc9_31.1 = mark_in_place_init %C__carbon_thunk.call.loc9
 // CHECK:STDOUT:   %.loc9_16: type = splice_block %C.ref.loc9_16 [concrete = constants.%C] {
 // CHECK:STDOUT:     %Cpp.ref.loc9_11: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
 // CHECK:STDOUT:     %N.ref.loc9_14: <namespace> = name_ref N, imports.%N [concrete = imports.%N]
@@ -2475,7 +2505,7 @@ fn F() {
 // CHECK:STDOUT:   %addr.loc10_24.2: %ptr.838 = addr_of %.loc10_26
 // CHECK:STDOUT:   %addr.loc10_24.3: %ptr.838 = addr_of %.loc10_24.1
 // CHECK:STDOUT:   %operator_Plus__carbon_thunk.call: init %empty_tuple.type = call imports.%operator_Plus__carbon_thunk.decl(%addr.loc10_24.1, %addr.loc10_24.2, %addr.loc10_24.3)
-// CHECK:STDOUT:   %.loc10_24.2: init %C to %.loc10_24.1 = in_place_init %operator_Plus__carbon_thunk.call
+// CHECK:STDOUT:   %.loc10_24.2: init %C to %.loc10_24.1 = mark_in_place_init %operator_Plus__carbon_thunk.call
 // CHECK:STDOUT:   %.loc10_16: type = splice_block %C.ref.loc10 [concrete = constants.%C] {
 // CHECK:STDOUT:     %Cpp.ref.loc10: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
 // CHECK:STDOUT:     %N.ref.loc10: <namespace> = name_ref N, imports.%N [concrete = imports.%N]
@@ -2575,7 +2605,7 @@ fn F() {
 // CHECK:STDOUT:   %.loc8_36.1: ref %C1 = temporary_storage
 // CHECK:STDOUT:   %addr.loc8: %ptr.087 = addr_of %.loc8_36.1
 // CHECK:STDOUT:   %C1__carbon_thunk.call: init %empty_tuple.type = call imports.%C1__carbon_thunk.decl(%addr.loc8)
-// CHECK:STDOUT:   %.loc8_36.2: init %C1 to %.loc8_36.1 = in_place_init %C1__carbon_thunk.call
+// CHECK:STDOUT:   %.loc8_36.2: init %C1 to %.loc8_36.1 = mark_in_place_init %C1__carbon_thunk.call
 // CHECK:STDOUT:   %.loc8_17: type = splice_block %C1.ref.loc8_17 [concrete = constants.%C1] {
 // CHECK:STDOUT:     %Cpp.ref.loc8_11: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
 // CHECK:STDOUT:     %N1.ref.loc8_14: <namespace> = name_ref N1, imports.%N1 [concrete = imports.%N1]
@@ -2594,7 +2624,7 @@ fn F() {
 // CHECK:STDOUT:   %.loc9_36.1: ref %C2 = temporary_storage
 // CHECK:STDOUT:   %addr.loc9: %ptr.51f = addr_of %.loc9_36.1
 // CHECK:STDOUT:   %C2__carbon_thunk.call: init %empty_tuple.type = call imports.%C2__carbon_thunk.decl(%addr.loc9)
-// CHECK:STDOUT:   %.loc9_36.2: init %C2 to %.loc9_36.1 = in_place_init %C2__carbon_thunk.call
+// CHECK:STDOUT:   %.loc9_36.2: init %C2 to %.loc9_36.1 = mark_in_place_init %C2__carbon_thunk.call
 // CHECK:STDOUT:   %.loc9_17: type = splice_block %C2.ref.loc9_17 [concrete = constants.%C2] {
 // CHECK:STDOUT:     %Cpp.ref.loc9_11: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
 // CHECK:STDOUT:     %N2.ref.loc9_14: <namespace> = name_ref N2, imports.%N2 [concrete = imports.%N2]
@@ -2615,7 +2645,7 @@ fn F() {
 // CHECK:STDOUT:   %addr.loc10_26.2: %ptr.51f = addr_of %.loc10_28
 // CHECK:STDOUT:   %addr.loc10_26.3: %ptr.51f = addr_of %.loc10_26.1
 // CHECK:STDOUT:   %operator_Plus__carbon_thunk.call: init %empty_tuple.type = call imports.%operator_Plus__carbon_thunk.decl(%addr.loc10_26.1, %addr.loc10_26.2, %addr.loc10_26.3)
-// CHECK:STDOUT:   %.loc10_26.2: init %C2 to %.loc10_26.1 = in_place_init %operator_Plus__carbon_thunk.call
+// CHECK:STDOUT:   %.loc10_26.2: init %C2 to %.loc10_26.1 = mark_in_place_init %operator_Plus__carbon_thunk.call
 // CHECK:STDOUT:   %.loc10_17: type = splice_block %C2.ref.loc10 [concrete = constants.%C2] {
 // CHECK:STDOUT:     %Cpp.ref.loc10: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
 // CHECK:STDOUT:     %N2.ref.loc10: <namespace> = name_ref N2, imports.%N2 [concrete = imports.%N2]
@@ -2636,7 +2666,7 @@ fn F() {
 // CHECK:STDOUT:   %addr.loc11_26.2: %ptr.087 = addr_of %.loc11_28
 // CHECK:STDOUT:   %addr.loc11_26.3: %ptr.51f = addr_of %.loc11_26.1
 // CHECK:STDOUT:   %operator_Minus__carbon_thunk.call: init %empty_tuple.type = call imports.%operator_Minus__carbon_thunk.decl(%addr.loc11_26.1, %addr.loc11_26.2, %addr.loc11_26.3)
-// CHECK:STDOUT:   %.loc11_26.2: init %C2 to %.loc11_26.1 = in_place_init %operator_Minus__carbon_thunk.call
+// CHECK:STDOUT:   %.loc11_26.2: init %C2 to %.loc11_26.1 = mark_in_place_init %operator_Minus__carbon_thunk.call
 // CHECK:STDOUT:   %.loc11_17: type = splice_block %C2.ref.loc11 [concrete = constants.%C2] {
 // CHECK:STDOUT:     %Cpp.ref.loc11: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
 // CHECK:STDOUT:     %N2.ref.loc11: <namespace> = name_ref N2, imports.%N2 [concrete = imports.%N2]
@@ -2705,7 +2735,7 @@ fn F() {
 // CHECK:STDOUT:   %.loc8_31.1: ref %C = temporary_storage
 // CHECK:STDOUT:   %addr.loc8: %ptr.838 = addr_of %.loc8_31.1
 // CHECK:STDOUT:   %C__carbon_thunk.call.loc8: init %empty_tuple.type = call imports.%C__carbon_thunk.decl(%addr.loc8)
-// CHECK:STDOUT:   %.loc8_31.2: init %C to %.loc8_31.1 = in_place_init %C__carbon_thunk.call.loc8
+// CHECK:STDOUT:   %.loc8_31.2: init %C to %.loc8_31.1 = mark_in_place_init %C__carbon_thunk.call.loc8
 // CHECK:STDOUT:   %.loc8_16: type = splice_block %C.ref.loc8_16 [concrete = constants.%C] {
 // CHECK:STDOUT:     %Cpp.ref.loc8_11: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
 // CHECK:STDOUT:     %N.ref.loc8_14: <namespace> = name_ref N, imports.%N [concrete = imports.%N]
@@ -2724,7 +2754,7 @@ fn F() {
 // CHECK:STDOUT:   %.loc9_31.1: ref %C = temporary_storage
 // CHECK:STDOUT:   %addr.loc9: %ptr.838 = addr_of %.loc9_31.1
 // CHECK:STDOUT:   %C__carbon_thunk.call.loc9: init %empty_tuple.type = call imports.%C__carbon_thunk.decl(%addr.loc9)
-// CHECK:STDOUT:   %.loc9_31.2: init %C to %.loc9_31.1 = in_place_init %C__carbon_thunk.call.loc9
+// CHECK:STDOUT:   %.loc9_31.2: init %C to %.loc9_31.1 = mark_in_place_init %C__carbon_thunk.call.loc9
 // CHECK:STDOUT:   %.loc9_16: type = splice_block %C.ref.loc9_16 [concrete = constants.%C] {
 // CHECK:STDOUT:     %Cpp.ref.loc9_11: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
 // CHECK:STDOUT:     %N.ref.loc9_14: <namespace> = name_ref N, imports.%N [concrete = imports.%N]
@@ -2803,7 +2833,7 @@ fn F() {
 // CHECK:STDOUT:   %.loc8_31.1: ref %C = temporary_storage
 // CHECK:STDOUT:   %addr.loc8: %ptr.de2 = addr_of %.loc8_31.1
 // CHECK:STDOUT:   %C__carbon_thunk.call.loc8: init %empty_tuple.type = call imports.%C__carbon_thunk.decl(%addr.loc8)
-// CHECK:STDOUT:   %.loc8_31.2: init %C to %.loc8_31.1 = in_place_init %C__carbon_thunk.call.loc8
+// CHECK:STDOUT:   %.loc8_31.2: init %C to %.loc8_31.1 = mark_in_place_init %C__carbon_thunk.call.loc8
 // CHECK:STDOUT:   %.loc8_16: type = splice_block %C.ref.loc8_16 [concrete = constants.%C] {
 // CHECK:STDOUT:     %Cpp.ref.loc8_11: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
 // CHECK:STDOUT:     %O.ref.loc8_14: type = name_ref O, imports.%O.decl [concrete = constants.%O]
@@ -2822,7 +2852,7 @@ fn F() {
 // CHECK:STDOUT:   %.loc9_31.1: ref %C = temporary_storage
 // CHECK:STDOUT:   %addr.loc9: %ptr.de2 = addr_of %.loc9_31.1
 // CHECK:STDOUT:   %C__carbon_thunk.call.loc9: init %empty_tuple.type = call imports.%C__carbon_thunk.decl(%addr.loc9)
-// CHECK:STDOUT:   %.loc9_31.2: init %C to %.loc9_31.1 = in_place_init %C__carbon_thunk.call.loc9
+// CHECK:STDOUT:   %.loc9_31.2: init %C to %.loc9_31.1 = mark_in_place_init %C__carbon_thunk.call.loc9
 // CHECK:STDOUT:   %.loc9_16: type = splice_block %C.ref.loc9_16 [concrete = constants.%C] {
 // CHECK:STDOUT:     %Cpp.ref.loc9_11: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
 // CHECK:STDOUT:     %O.ref.loc9_14: type = name_ref O, imports.%O.decl [concrete = constants.%O]
@@ -2843,7 +2873,7 @@ fn F() {
 // CHECK:STDOUT:   %addr.loc10_24.2: %ptr.de2 = addr_of %.loc10_26
 // CHECK:STDOUT:   %addr.loc10_24.3: %ptr.de2 = addr_of %.loc10_24.1
 // CHECK:STDOUT:   %operator_Plus__carbon_thunk.call: init %empty_tuple.type = call imports.%operator_Plus__carbon_thunk.decl(%addr.loc10_24.1, %addr.loc10_24.2, %addr.loc10_24.3)
-// CHECK:STDOUT:   %.loc10_24.2: init %C to %.loc10_24.1 = in_place_init %operator_Plus__carbon_thunk.call
+// CHECK:STDOUT:   %.loc10_24.2: init %C to %.loc10_24.1 = mark_in_place_init %operator_Plus__carbon_thunk.call
 // CHECK:STDOUT:   %.loc10_16: type = splice_block %C.ref.loc10 [concrete = constants.%C] {
 // CHECK:STDOUT:     %Cpp.ref.loc10: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
 // CHECK:STDOUT:     %O.ref.loc10: type = name_ref O, imports.%O.decl [concrete = constants.%O]
@@ -2918,7 +2948,7 @@ fn F() {
 // CHECK:STDOUT:   %.loc8_35.1: ref %C = temporary_storage
 // CHECK:STDOUT:   %addr.loc8: %ptr.4b2 = addr_of %.loc8_35.1
 // CHECK:STDOUT:   %C__carbon_thunk.call.loc8: init %empty_tuple.type = call imports.%C__carbon_thunk.decl(%addr.loc8)
-// CHECK:STDOUT:   %.loc8_35.2: init %C to %.loc8_35.1 = in_place_init %C__carbon_thunk.call.loc8
+// CHECK:STDOUT:   %.loc8_35.2: init %C to %.loc8_35.1 = mark_in_place_init %C__carbon_thunk.call.loc8
 // CHECK:STDOUT:   %.loc8_18: type = splice_block %C.ref.loc8_18 [concrete = constants.%C] {
 // CHECK:STDOUT:     %Cpp.ref.loc8_11: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
 // CHECK:STDOUT:     %N.ref.loc8_14: <namespace> = name_ref N, imports.%N [concrete = imports.%N]
@@ -2939,7 +2969,7 @@ fn F() {
 // CHECK:STDOUT:   %.loc9_35.1: ref %C = temporary_storage
 // CHECK:STDOUT:   %addr.loc9: %ptr.4b2 = addr_of %.loc9_35.1
 // CHECK:STDOUT:   %C__carbon_thunk.call.loc9: init %empty_tuple.type = call imports.%C__carbon_thunk.decl(%addr.loc9)
-// CHECK:STDOUT:   %.loc9_35.2: init %C to %.loc9_35.1 = in_place_init %C__carbon_thunk.call.loc9
+// CHECK:STDOUT:   %.loc9_35.2: init %C to %.loc9_35.1 = mark_in_place_init %C__carbon_thunk.call.loc9
 // CHECK:STDOUT:   %.loc9_18: type = splice_block %C.ref.loc9_18 [concrete = constants.%C] {
 // CHECK:STDOUT:     %Cpp.ref.loc9_11: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
 // CHECK:STDOUT:     %N.ref.loc9_14: <namespace> = name_ref N, imports.%N [concrete = imports.%N]
@@ -2961,7 +2991,7 @@ fn F() {
 // CHECK:STDOUT:   %addr.loc10_26.2: %ptr.4b2 = addr_of %.loc10_28
 // CHECK:STDOUT:   %addr.loc10_26.3: %ptr.4b2 = addr_of %.loc10_26.1
 // CHECK:STDOUT:   %operator_Plus__carbon_thunk.call: init %empty_tuple.type = call imports.%operator_Plus__carbon_thunk.decl(%addr.loc10_26.1, %addr.loc10_26.2, %addr.loc10_26.3)
-// CHECK:STDOUT:   %.loc10_26.2: init %C to %.loc10_26.1 = in_place_init %operator_Plus__carbon_thunk.call
+// CHECK:STDOUT:   %.loc10_26.2: init %C to %.loc10_26.1 = mark_in_place_init %operator_Plus__carbon_thunk.call
 // CHECK:STDOUT:   %.loc10_18: type = splice_block %C.ref.loc10 [concrete = constants.%C] {
 // CHECK:STDOUT:     %Cpp.ref.loc10: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
 // CHECK:STDOUT:     %N.ref.loc10: <namespace> = name_ref N, imports.%N [concrete = imports.%N]
@@ -3060,7 +3090,7 @@ fn F() {
 // CHECK:STDOUT:   %.loc8_3: ref %C = splice_block %c1.var {}
 // CHECK:STDOUT:   %addr.loc8: %ptr.d9e = addr_of %.loc8_3
 // CHECK:STDOUT:   %C__carbon_thunk.call: init %empty_tuple.type = call imports.%C__carbon_thunk.decl(%addr.loc8)
-// CHECK:STDOUT:   %.loc8_27: init %C to %.loc8_3 = in_place_init %C__carbon_thunk.call
+// CHECK:STDOUT:   %.loc8_27: init %C to %.loc8_3 = mark_in_place_init %C__carbon_thunk.call
 // CHECK:STDOUT:   assign %c1.var, %.loc8_27
 // CHECK:STDOUT:   %.loc8_14: type = splice_block %C.ref.loc8_14 [concrete = constants.%C] {
 // CHECK:STDOUT:     %Cpp.ref.loc8_11: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
@@ -3077,7 +3107,7 @@ fn F() {
 // CHECK:STDOUT:   %.loc9_3: ref %C = splice_block %c2.var {}
 // CHECK:STDOUT:   %addr.loc9: %ptr.d9e = addr_of %.loc9_3
 // CHECK:STDOUT:   %operator_Minus__carbon_thunk.call: init %empty_tuple.type = call imports.%operator_Minus__carbon_thunk.decl(%c1.ref.loc9, %addr.loc9)
-// CHECK:STDOUT:   %.loc9_19: init %C to %.loc9_3 = in_place_init %operator_Minus__carbon_thunk.call
+// CHECK:STDOUT:   %.loc9_19: init %C to %.loc9_3 = mark_in_place_init %operator_Minus__carbon_thunk.call
 // CHECK:STDOUT:   assign %c2.var, %.loc9_19
 // CHECK:STDOUT:   %.loc9_14: type = splice_block %C.ref.loc9 [concrete = constants.%C] {
 // CHECK:STDOUT:     %Cpp.ref.loc9: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
@@ -3098,7 +3128,7 @@ fn F() {
 // CHECK:STDOUT:   %addr.loc10_22.1: %ptr.d9e = addr_of %.loc10_24.2
 // CHECK:STDOUT:   %addr.loc10_22.2: %ptr.d9e = addr_of %.loc10_3
 // CHECK:STDOUT:   %operator_Plus__carbon_thunk.call: init %empty_tuple.type = call imports.%operator_Plus__carbon_thunk.decl(%c1.ref.loc10, %addr.loc10_22.1, %addr.loc10_22.2)
-// CHECK:STDOUT:   %.loc10_22: init %C to %.loc10_3 = in_place_init %operator_Plus__carbon_thunk.call
+// CHECK:STDOUT:   %.loc10_22: init %C to %.loc10_3 = mark_in_place_init %operator_Plus__carbon_thunk.call
 // CHECK:STDOUT:   assign %c3.var, %.loc10_22
 // CHECK:STDOUT:   %.loc10_14: type = splice_block %C.ref.loc10 [concrete = constants.%C] {
 // CHECK:STDOUT:     %Cpp.ref.loc10: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
@@ -3188,7 +3218,7 @@ fn F() {
 // CHECK:STDOUT:   %addr.loc10_22.2: %ptr.d9e = addr_of %.loc10_24
 // CHECK:STDOUT:   %addr.loc10_22.3: %ptr.d9e = addr_of %.loc10_22.1
 // CHECK:STDOUT:   %operator_Plus__carbon_thunk.call: init %empty_tuple.type = call imports.%operator_Plus__carbon_thunk.decl(%addr.loc10_22.1, %addr.loc10_22.2, %addr.loc10_22.3)
-// CHECK:STDOUT:   %.loc10_22.2: init %C to %.loc10_22.1 = in_place_init %operator_Plus__carbon_thunk.call
+// CHECK:STDOUT:   %.loc10_22.2: init %C to %.loc10_22.1 = mark_in_place_init %operator_Plus__carbon_thunk.call
 // CHECK:STDOUT:   %.loc10_14: type = splice_block %C.ref.loc10 [concrete = constants.%C] {
 // CHECK:STDOUT:     %Cpp.ref.loc10: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
 // CHECK:STDOUT:     %C.ref.loc10: type = name_ref C, imports.%C.decl [concrete = constants.%C]
diff --git a/toolchain/check/testdata/interop/cpp/function/overloads.carbon b/toolchain/check/testdata/interop/cpp/function/overloads.carbon
index fc8bb6efcf1e..b4280afcfaa1 100644
--- a/toolchain/check/testdata/interop/cpp/function/overloads.carbon
+++ b/toolchain/check/testdata/interop/cpp/function/overloads.carbon
@@ -1651,13 +1651,13 @@ fn F() {
 // CHECK:STDOUT:   %.loc22_44.1: ref %i128 = temporary_storage
 // CHECK:STDOUT:   %addr.loc22_44.2: %ptr.974 = addr_of %.loc22_44.1
 // CHECK:STDOUT:   %foo__carbon_thunk.call.loc22: init %empty_tuple.type = call imports.%foo__carbon_thunk.decl(%addr.loc22_44.1, %addr.loc22_44.2)
-// CHECK:STDOUT:   %.loc22_44.2: init %i128 = in_place_init %foo__carbon_thunk.call.loc22, %.loc22_44.1
+// CHECK:STDOUT:   %.loc22_44.2: init %i128 to %.loc22_44.1 = mark_in_place_init %foo__carbon_thunk.call.loc22
 // CHECK:STDOUT:   %.loc22_10: type = splice_block %i128.loc22 [concrete = constants.%i128] {
 // CHECK:STDOUT:     %int_128.loc22: Core.IntLiteral = int_value 128 [concrete = constants.%int_128]
 // CHECK:STDOUT:     %i128.loc22: type = class_type @Int, @Int(constants.%int_128) [concrete = constants.%i128]
 // CHECK:STDOUT:   }
-// CHECK:STDOUT:   %.loc22_44.3: %i128 = value_of_initializer %.loc22_44.2
-// CHECK:STDOUT:   %.loc22_44.4: %i128 = converted %.loc22_44.2, %.loc22_44.3
+// CHECK:STDOUT:   %.loc22_44.3: ref %i128 = temporary %.loc22_44.1, %.loc22_44.2
+// CHECK:STDOUT:   %.loc22_44.4: %i128 = acquire_value %.loc22_44.3
 // CHECK:STDOUT:   %d: %i128 = value_binding d, %.loc22_44.4
 // CHECK:STDOUT:   name_binding_decl {
 // CHECK:STDOUT:     %e.patt: %pattern_type.57d = value_binding_pattern e [concrete]
@@ -1683,13 +1683,13 @@ fn F() {
 // CHECK:STDOUT:   %.loc25_45.1: ref %i128 = temporary_storage
 // CHECK:STDOUT:   %addr.loc25_45.2: %ptr.974 = addr_of %.loc25_45.1
 // CHECK:STDOUT:   %foo__carbon_thunk.call.loc25: init %empty_tuple.type = call imports.%foo__carbon_thunk.decl(%addr.loc25_45.1, %addr.loc25_45.2)
-// CHECK:STDOUT:   %.loc25_45.2: init %i128 = in_place_init %foo__carbon_thunk.call.loc25, %.loc25_45.1
+// CHECK:STDOUT:   %.loc25_45.2: init %i128 to %.loc25_45.1 = mark_in_place_init %foo__carbon_thunk.call.loc25
 // CHECK:STDOUT:   %.loc25_10: type = splice_block %i128.loc25 [concrete = constants.%i128] {
 // CHECK:STDOUT:     %int_128.loc25: Core.IntLiteral = int_value 128 [concrete = constants.%int_128]
 // CHECK:STDOUT:     %i128.loc25: type = class_type @Int, @Int(constants.%int_128) [concrete = constants.%i128]
 // CHECK:STDOUT:   }
-// CHECK:STDOUT:   %.loc25_45.3: %i128 = value_of_initializer %.loc25_45.2
-// CHECK:STDOUT:   %.loc25_45.4: %i128 = converted %.loc25_45.2, %.loc25_45.3
+// CHECK:STDOUT:   %.loc25_45.3: ref %i128 = temporary %.loc25_45.1, %.loc25_45.2
+// CHECK:STDOUT:   %.loc25_45.4: %i128 = acquire_value %.loc25_45.3
 // CHECK:STDOUT:   %e: %i128 = value_binding e, %.loc25_45.4
 // CHECK:STDOUT:   name_binding_decl {
 // CHECK:STDOUT:     %f.patt: %pattern_type.57d = value_binding_pattern f [concrete]
@@ -1715,13 +1715,13 @@ fn F() {
 // CHECK:STDOUT:   %.loc28_45.1: ref %i128 = temporary_storage
 // CHECK:STDOUT:   %addr.loc28_45.2: %ptr.974 = addr_of %.loc28_45.1
 // CHECK:STDOUT:   %foo__carbon_thunk.call.loc28: init %empty_tuple.type = call imports.%foo__carbon_thunk.decl(%addr.loc28_45.1, %addr.loc28_45.2)
-// CHECK:STDOUT:   %.loc28_45.2: init %i128 = in_place_init %foo__carbon_thunk.call.loc28, %.loc28_45.1
+// CHECK:STDOUT:   %.loc28_45.2: init %i128 to %.loc28_45.1 = mark_in_place_init %foo__carbon_thunk.call.loc28
 // CHECK:STDOUT:   %.loc28_10: type = splice_block %i128.loc28 [concrete = constants.%i128] {
 // CHECK:STDOUT:     %int_128.loc28: Core.IntLiteral = int_value 128 [concrete = constants.%int_128]
 // CHECK:STDOUT:     %i128.loc28: type = class_type @Int, @Int(constants.%int_128) [concrete = constants.%i128]
 // CHECK:STDOUT:   }
-// CHECK:STDOUT:   %.loc28_45.3: %i128 = value_of_initializer %.loc28_45.2
-// CHECK:STDOUT:   %.loc28_45.4: %i128 = converted %.loc28_45.2, %.loc28_45.3
+// CHECK:STDOUT:   %.loc28_45.3: ref %i128 = temporary %.loc28_45.1, %.loc28_45.2
+// CHECK:STDOUT:   %.loc28_45.4: %i128 = acquire_value %.loc28_45.3
 // CHECK:STDOUT:   %f: %i128 = value_binding f, %.loc28_45.4
 // CHECK:STDOUT:   name_binding_decl {
 // CHECK:STDOUT:     %g.patt: %pattern_type.57d = value_binding_pattern g [concrete]
@@ -1747,22 +1747,30 @@ fn F() {
 // CHECK:STDOUT:   %.loc31_64.1: ref %i128 = temporary_storage
 // CHECK:STDOUT:   %addr.loc31_64.2: %ptr.974 = addr_of %.loc31_64.1
 // CHECK:STDOUT:   %foo__carbon_thunk.call.loc31: init %empty_tuple.type = call imports.%foo__carbon_thunk.decl(%addr.loc31_64.1, %addr.loc31_64.2)
-// CHECK:STDOUT:   %.loc31_64.2: init %i128 = in_place_init %foo__carbon_thunk.call.loc31, %.loc31_64.1
+// CHECK:STDOUT:   %.loc31_64.2: init %i128 to %.loc31_64.1 = mark_in_place_init %foo__carbon_thunk.call.loc31
 // CHECK:STDOUT:   %.loc31_10: type = splice_block %i128.loc31 [concrete = constants.%i128] {
 // CHECK:STDOUT:     %int_128.loc31: Core.IntLiteral = int_value 128 [concrete = constants.%int_128]
 // CHECK:STDOUT:     %i128.loc31: type = class_type @Int, @Int(constants.%int_128) [concrete = constants.%i128]
 // CHECK:STDOUT:   }
-// CHECK:STDOUT:   %.loc31_64.3: %i128 = value_of_initializer %.loc31_64.2
-// CHECK:STDOUT:   %.loc31_64.4: %i128 = converted %.loc31_64.2, %.loc31_64.3
+// CHECK:STDOUT:   %.loc31_64.3: ref %i128 = temporary %.loc31_64.1, %.loc31_64.2
+// CHECK:STDOUT:   %.loc31_64.4: %i128 = acquire_value %.loc31_64.3
 // CHECK:STDOUT:   %g: %i128 = value_binding g, %.loc31_64.4
-// CHECK:STDOUT:   %DestroyOp.bound.loc31: <bound method> = bound_method %.loc31_25.4, constants.%DestroyOp
-// CHECK:STDOUT:   %DestroyOp.call.loc31: init %empty_tuple.type = call %DestroyOp.bound.loc31(%.loc31_25.4)
-// CHECK:STDOUT:   %DestroyOp.bound.loc28: <bound method> = bound_method %.loc28_25.4, constants.%DestroyOp
-// CHECK:STDOUT:   %DestroyOp.call.loc28: init %empty_tuple.type = call %DestroyOp.bound.loc28(%.loc28_25.4)
-// CHECK:STDOUT:   %DestroyOp.bound.loc25: <bound method> = bound_method %.loc25_25.4, constants.%DestroyOp
-// CHECK:STDOUT:   %DestroyOp.call.loc25: init %empty_tuple.type = call %DestroyOp.bound.loc25(%.loc25_25.4)
-// CHECK:STDOUT:   %DestroyOp.bound.loc22: <bound method> = bound_method %.loc22_25.4, constants.%DestroyOp
-// CHECK:STDOUT:   %DestroyOp.call.loc22: init %empty_tuple.type = call %DestroyOp.bound.loc22(%.loc22_25.4)
+// CHECK:STDOUT:   %DestroyOp.bound.loc31_64: <bound method> = bound_method %.loc31_64.3, constants.%DestroyOp
+// CHECK:STDOUT:   %DestroyOp.call.loc31_64: init %empty_tuple.type = call %DestroyOp.bound.loc31_64(%.loc31_64.3)
+// CHECK:STDOUT:   %DestroyOp.bound.loc31_25: <bound method> = bound_method %.loc31_25.4, constants.%DestroyOp
+// CHECK:STDOUT:   %DestroyOp.call.loc31_25: init %empty_tuple.type = call %DestroyOp.bound.loc31_25(%.loc31_25.4)
+// CHECK:STDOUT:   %DestroyOp.bound.loc28_45: <bound method> = bound_method %.loc28_45.3, constants.%DestroyOp
+// CHECK:STDOUT:   %DestroyOp.call.loc28_45: init %empty_tuple.type = call %DestroyOp.bound.loc28_45(%.loc28_45.3)
+// CHECK:STDOUT:   %DestroyOp.bound.loc28_25: <bound method> = bound_method %.loc28_25.4, constants.%DestroyOp
+// CHECK:STDOUT:   %DestroyOp.call.loc28_25: init %empty_tuple.type = call %DestroyOp.bound.loc28_25(%.loc28_25.4)
+// CHECK:STDOUT:   %DestroyOp.bound.loc25_45: <bound method> = bound_method %.loc25_45.3, constants.%DestroyOp
+// CHECK:STDOUT:   %DestroyOp.call.loc25_45: init %empty_tuple.type = call %DestroyOp.bound.loc25_45(%.loc25_45.3)
+// CHECK:STDOUT:   %DestroyOp.bound.loc25_25: <bound method> = bound_method %.loc25_25.4, constants.%DestroyOp
+// CHECK:STDOUT:   %DestroyOp.call.loc25_25: init %empty_tuple.type = call %DestroyOp.bound.loc25_25(%.loc25_25.4)
+// CHECK:STDOUT:   %DestroyOp.bound.loc22_44: <bound method> = bound_method %.loc22_44.3, constants.%DestroyOp
+// CHECK:STDOUT:   %DestroyOp.call.loc22_44: init %empty_tuple.type = call %DestroyOp.bound.loc22_44(%.loc22_44.3)
+// CHECK:STDOUT:   %DestroyOp.bound.loc22_25: <bound method> = bound_method %.loc22_25.4, constants.%DestroyOp
+// CHECK:STDOUT:   %DestroyOp.call.loc22_25: init %empty_tuple.type = call %DestroyOp.bound.loc22_25(%.loc22_25.4)
 // CHECK:STDOUT:   return
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
@@ -2194,16 +2202,18 @@ fn F() {
 // CHECK:STDOUT:   %.loc7_27.1: ref %f64.d77 = temporary_storage
 // CHECK:STDOUT:   %addr.loc7_27.2: %ptr.bcc = addr_of %.loc7_27.1
 // CHECK:STDOUT:   %foo__carbon_thunk.call: init %empty_tuple.type = call imports.%foo__carbon_thunk.decl(%addr.loc7_27.1, %addr.loc7_27.2)
-// CHECK:STDOUT:   %.loc7_27.2: init %f64.d77 = in_place_init %foo__carbon_thunk.call, %.loc7_27.1
+// CHECK:STDOUT:   %.loc7_27.2: init %f64.d77 to %.loc7_27.1 = mark_in_place_init %foo__carbon_thunk.call
 // CHECK:STDOUT:   %.loc7_10: type = splice_block %f64 [concrete = constants.%f64.d77] {
 // CHECK:STDOUT:     %int_64: Core.IntLiteral = int_value 64 [concrete = constants.%int_64]
 // CHECK:STDOUT:     %f64: type = class_type @Float, @Float(constants.%int_64) [concrete = constants.%f64.d77]
 // CHECK:STDOUT:   }
-// CHECK:STDOUT:   %.loc7_27.3: %f64.d77 = value_of_initializer %.loc7_27.2
-// CHECK:STDOUT:   %.loc7_27.4: %f64.d77 = converted %.loc7_27.2, %.loc7_27.3
+// CHECK:STDOUT:   %.loc7_27.3: ref %f64.d77 = temporary %.loc7_27.1, %.loc7_27.2
+// CHECK:STDOUT:   %.loc7_27.4: %f64.d77 = acquire_value %.loc7_27.3
 // CHECK:STDOUT:   %d: %f64.d77 = value_binding d, %.loc7_27.4
-// CHECK:STDOUT:   %DestroyOp.bound: <bound method> = bound_method %.loc7_24.4, constants.%DestroyOp
-// CHECK:STDOUT:   %DestroyOp.call: init %empty_tuple.type = call %DestroyOp.bound(%.loc7_24.4)
+// CHECK:STDOUT:   %DestroyOp.bound.loc7_27: <bound method> = bound_method %.loc7_27.3, constants.%DestroyOp
+// CHECK:STDOUT:   %DestroyOp.call.loc7_27: init %empty_tuple.type = call %DestroyOp.bound.loc7_27(%.loc7_27.3)
+// CHECK:STDOUT:   %DestroyOp.bound.loc7_24: <bound method> = bound_method %.loc7_24.4, constants.%DestroyOp
+// CHECK:STDOUT:   %DestroyOp.call.loc7_24: init %empty_tuple.type = call %DestroyOp.bound.loc7_24(%.loc7_24.4)
 // CHECK:STDOUT:   return
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
@@ -2340,9 +2350,12 @@ fn F() {
 // CHECK:STDOUT:   %.loc15_19.1: ref %f64.d77 = temporary_storage
 // CHECK:STDOUT:   %addr.loc15_19.2: %ptr.bcc = addr_of %.loc15_19.1
 // CHECK:STDOUT:   %foo__carbon_thunk.call: init %empty_tuple.type = call imports.%foo__carbon_thunk.decl(%addr.loc15_19.1, %addr.loc15_19.2)
-// CHECK:STDOUT:   %.loc15_19.2: init %f64.d77 = in_place_init %foo__carbon_thunk.call, %.loc15_19.1
-// CHECK:STDOUT:   %DestroyOp.bound: <bound method> = bound_method %.loc15_11.4, constants.%DestroyOp
-// CHECK:STDOUT:   %DestroyOp.call: init %empty_tuple.type = call %DestroyOp.bound(%.loc15_11.4)
+// CHECK:STDOUT:   %.loc15_19.2: init %f64.d77 to %.loc15_19.1 = mark_in_place_init %foo__carbon_thunk.call
+// CHECK:STDOUT:   %.loc15_19.3: ref %f64.d77 = temporary %.loc15_19.1, %.loc15_19.2
+// CHECK:STDOUT:   %DestroyOp.bound.loc15_19: <bound method> = bound_method %.loc15_19.3, constants.%DestroyOp
+// CHECK:STDOUT:   %DestroyOp.call.loc15_19: init %empty_tuple.type = call %DestroyOp.bound.loc15_19(%.loc15_19.3)
+// CHECK:STDOUT:   %DestroyOp.bound.loc15_11: <bound method> = bound_method %.loc15_11.4, constants.%DestroyOp
+// CHECK:STDOUT:   %DestroyOp.call.loc15_11: init %empty_tuple.type = call %DestroyOp.bound.loc15_11(%.loc15_11.4)
 // CHECK:STDOUT:   return
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
diff --git a/toolchain/check/testdata/interop/cpp/function/return.carbon b/toolchain/check/testdata/interop/cpp/function/return.carbon
index c01773e4108f..c0f68bcb2d28 100644
--- a/toolchain/check/testdata/interop/cpp/function/return.carbon
+++ b/toolchain/check/testdata/interop/cpp/function/return.carbon
@@ -2,7 +2,7 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
-// INCLUDE-FILE: toolchain/testing/testdata/min_prelude/primitives.carbon
+// INCLUDE-FILE: toolchain/testing/testdata/min_prelude/full.carbon
 //
 // AUTOUPDATE
 // TIP: To test this file alone, run:
@@ -55,6 +55,55 @@ fn Call() {
   Cpp.UndeducedReturn();
 }
 
+// ============================================================================
+// Initialize a variable from a thunk output parameter
+// ============================================================================
+
+// --- var_from_thunk_param.carbon
+
+library "[[@TEST_NAME]]";
+
+import Cpp inline '''
+using nullptr_t = decltype(nullptr);
+auto ReturnNullPtr() -> nullptr_t;
+''';
+
+fn InitializeFromReturn() {
+  //@dump-sem-ir-begin
+  var c: Cpp.nullptr_t = Cpp.ReturnNullPtr();
+  //@dump-sem-ir-end
+}
+
+// ============================================================================
+// Return from a thunk output parameter
+// ============================================================================
+
+// --- return_from_thunk_param.carbon
+//@include-in-dumps
+library "[[@TEST_NAME]]";
+
+import Cpp inline '''
+unsigned char ReturnU8();
+''';
+
+fn GetU8() -> u8 { return Cpp.ReturnU8(); }
+
+// ============================================================================
+// Initialize a variable from a thunk with no output parameter
+// ============================================================================
+
+// --- var_from_thunk_by_value.carbon
+//@include-in-dumps
+library "[[@TEST_NAME]]";
+
+import Cpp inline '''
+unsigned int ReturnU32();
+''';
+
+fn Var() {
+  var my_u32: u32 = Cpp.ReturnU32();
+}
+
 // CHECK:STDOUT: --- import_multiple.carbon
 // CHECK:STDOUT:
 // CHECK:STDOUT: constants {
@@ -76,6 +125,8 @@ fn Call() {
 // CHECK:STDOUT:   %foo2.cpp_overload_set.value: %foo2.cpp_overload_set.type = cpp_overload_set_value @foo2.cpp_overload_set [concrete]
 // CHECK:STDOUT:   %foo2.type: type = fn_type @foo2 [concrete]
 // CHECK:STDOUT:   %foo2: %foo2.type = struct_value () [concrete]
+// CHECK:STDOUT:   %DestroyOp.type: type = fn_type @DestroyOp [concrete]
+// CHECK:STDOUT:   %DestroyOp: %DestroyOp.type = struct_value () [concrete]
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: imports {
@@ -106,9 +157,9 @@ fn Call() {
 // CHECK:STDOUT:   %.loc11_22.1: ref %i16 = temporary_storage
 // CHECK:STDOUT:   %addr: %ptr = addr_of %.loc11_22.1
 // CHECK:STDOUT:   %foo1__carbon_thunk.call: init %empty_tuple.type = call imports.%foo1__carbon_thunk.decl(%addr)
-// CHECK:STDOUT:   %.loc11_22.2: init %i16 = in_place_init %foo1__carbon_thunk.call, %.loc11_22.1
-// CHECK:STDOUT:   %.loc11_22.3: %i16 = value_of_initializer %.loc11_22.2
-// CHECK:STDOUT:   %.loc11_22.4: %i16 = converted %.loc11_22.2, %.loc11_22.3
+// CHECK:STDOUT:   %.loc11_22.2: init %i16 to %.loc11_22.1 = mark_in_place_init %foo1__carbon_thunk.call
+// CHECK:STDOUT:   %.loc11_22.3: ref %i16 = temporary %.loc11_22.1, %.loc11_22.2
+// CHECK:STDOUT:   %.loc11_22.4: %i16 = acquire_value %.loc11_22.3
 // CHECK:STDOUT:   %IngestI16.call: init %empty_tuple.type = call %IngestI16.ref(%.loc11_22.4)
 // CHECK:STDOUT:   %IngestI32.ref: %IngestI32.type = name_ref IngestI32, file.%IngestI32.decl [concrete = constants.%IngestI32]
 // CHECK:STDOUT:   %Cpp.ref.loc12: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
@@ -117,6 +168,230 @@ fn Call() {
 // CHECK:STDOUT:   %.loc12_22.1: %i32 = value_of_initializer %foo2.call
 // CHECK:STDOUT:   %.loc12_22.2: %i32 = converted %foo2.call, %.loc12_22.1
 // CHECK:STDOUT:   %IngestI32.call: init %empty_tuple.type = call %IngestI32.ref(%.loc12_22.2)
+// CHECK:STDOUT:   %DestroyOp.bound: <bound method> = bound_method %.loc11_22.3, constants.%DestroyOp
+// CHECK:STDOUT:   %DestroyOp.call: init %empty_tuple.type = call %DestroyOp.bound(%.loc11_22.3)
 // CHECK:STDOUT:   <elided>
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
+// CHECK:STDOUT: fn @DestroyOp(%self.param: %i16) = "no_op";
+// CHECK:STDOUT:
+// CHECK:STDOUT: --- var_from_thunk_param.carbon
+// CHECK:STDOUT:
+// CHECK:STDOUT: constants {
+// CHECK:STDOUT:   %empty_tuple.type: type = tuple_type () [concrete]
+// CHECK:STDOUT:   %Cpp.nullptr_t: type = class_type @NullptrT [concrete]
+// CHECK:STDOUT:   %pattern_type.f05: type = pattern_type %Cpp.nullptr_t [concrete]
+// CHECK:STDOUT:   %ReturnNullPtr.cpp_overload_set.type: type = cpp_overload_set_type @ReturnNullPtr.cpp_overload_set [concrete]
+// CHECK:STDOUT:   %ReturnNullPtr.cpp_overload_set.value: %ReturnNullPtr.cpp_overload_set.type = cpp_overload_set_value @ReturnNullPtr.cpp_overload_set [concrete]
+// CHECK:STDOUT:   %ptr.142: type = ptr_type %Cpp.nullptr_t [concrete]
+// CHECK:STDOUT:   %ReturnNullPtr__carbon_thunk.type: type = fn_type @ReturnNullPtr__carbon_thunk [concrete]
+// CHECK:STDOUT:   %ReturnNullPtr__carbon_thunk: %ReturnNullPtr__carbon_thunk.type = struct_value () [concrete]
+// CHECK:STDOUT:   %DestroyOp.type.3e79c2.2: type = fn_type @DestroyOp.loc11 [concrete]
+// CHECK:STDOUT:   %DestroyOp.b0ebf8.2: %DestroyOp.type.3e79c2.2 = struct_value () [concrete]
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: imports {
+// CHECK:STDOUT:   %Cpp: <namespace> = namespace file.%Cpp.import_cpp, [concrete] {
+// CHECK:STDOUT:     .nullptr_t = constants.%Cpp.nullptr_t
+// CHECK:STDOUT:     .ReturnNullPtr = %ReturnNullPtr.cpp_overload_set.value
+// CHECK:STDOUT:     import Cpp//...
+// CHECK:STDOUT:   }
+// CHECK:STDOUT:   %ReturnNullPtr.cpp_overload_set.value: %ReturnNullPtr.cpp_overload_set.type = cpp_overload_set_value @ReturnNullPtr.cpp_overload_set [concrete = constants.%ReturnNullPtr.cpp_overload_set.value]
+// CHECK:STDOUT:   %ReturnNullPtr__carbon_thunk.decl: %ReturnNullPtr__carbon_thunk.type = fn_decl @ReturnNullPtr__carbon_thunk [concrete = constants.%ReturnNullPtr__carbon_thunk] {
+// CHECK:STDOUT:     <elided>
+// CHECK:STDOUT:   } {
+// CHECK:STDOUT:     <elided>
+// CHECK:STDOUT:   }
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: fn @InitializeFromReturn() {
+// CHECK:STDOUT: !entry:
+// CHECK:STDOUT:   name_binding_decl {
+// CHECK:STDOUT:     %c.patt: %pattern_type.f05 = ref_binding_pattern c [concrete]
+// CHECK:STDOUT:     %c.var_patt: %pattern_type.f05 = var_pattern %c.patt [concrete]
+// CHECK:STDOUT:   }
+// CHECK:STDOUT:   %c.var: ref %Cpp.nullptr_t = var %c.var_patt
+// CHECK:STDOUT:   %Cpp.ref.loc11_26: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
+// CHECK:STDOUT:   %ReturnNullPtr.ref: %ReturnNullPtr.cpp_overload_set.type = name_ref ReturnNullPtr, imports.%ReturnNullPtr.cpp_overload_set.value [concrete = constants.%ReturnNullPtr.cpp_overload_set.value]
+// CHECK:STDOUT:   %.loc11_3: ref %Cpp.nullptr_t = splice_block %c.var {}
+// CHECK:STDOUT:   %addr: %ptr.142 = addr_of %.loc11_3
+// CHECK:STDOUT:   %ReturnNullPtr__carbon_thunk.call: init %empty_tuple.type = call imports.%ReturnNullPtr__carbon_thunk.decl(%addr)
+// CHECK:STDOUT:   %.loc11_44: init %Cpp.nullptr_t to %.loc11_3 = mark_in_place_init %ReturnNullPtr__carbon_thunk.call
+// CHECK:STDOUT:   assign %c.var, %.loc11_44
+// CHECK:STDOUT:   %.loc11_13: type = splice_block %nullptr_t.ref [concrete = constants.%Cpp.nullptr_t] {
+// CHECK:STDOUT:     %Cpp.ref.loc11_10: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
+// CHECK:STDOUT:     %nullptr_t.ref: type = name_ref nullptr_t, constants.%Cpp.nullptr_t [concrete = constants.%Cpp.nullptr_t]
+// CHECK:STDOUT:   }
+// CHECK:STDOUT:   %c: ref %Cpp.nullptr_t = ref_binding c, %c.var
+// CHECK:STDOUT:   %DestroyOp.bound: <bound method> = bound_method %c.var, constants.%DestroyOp.b0ebf8.2
+// CHECK:STDOUT:   %DestroyOp.call: init %empty_tuple.type = call %DestroyOp.bound(%c.var)
+// CHECK:STDOUT:   <elided>
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: fn @DestroyOp.loc11(%self.param: %Cpp.nullptr_t) = "no_op";
+// CHECK:STDOUT:
+// CHECK:STDOUT: --- return_from_thunk_param.carbon
+// CHECK:STDOUT:
+// CHECK:STDOUT: constants {
+// CHECK:STDOUT:   %int_8: Core.IntLiteral = int_value 8 [concrete]
+// CHECK:STDOUT:   %UInt.type: type = generic_class_type @UInt [concrete]
+// CHECK:STDOUT:   %empty_tuple.type: type = tuple_type () [concrete]
+// CHECK:STDOUT:   %UInt.generic: %UInt.type = struct_value () [concrete]
+// CHECK:STDOUT:   %u8: type = class_type @UInt, @UInt(%int_8) [concrete]
+// CHECK:STDOUT:   %.98d: form = init_form %u8, call_param0 [concrete]
+// CHECK:STDOUT:   %pattern_type.8f3: type = pattern_type %u8 [concrete]
+// CHECK:STDOUT:   %GetU8.type: type = fn_type @GetU8 [concrete]
+// CHECK:STDOUT:   %GetU8: %GetU8.type = struct_value () [concrete]
+// CHECK:STDOUT:   %ReturnU8.cpp_overload_set.type: type = cpp_overload_set_type @ReturnU8.cpp_overload_set [concrete]
+// CHECK:STDOUT:   %ReturnU8.cpp_overload_set.value: %ReturnU8.cpp_overload_set.type = cpp_overload_set_value @ReturnU8.cpp_overload_set [concrete]
+// CHECK:STDOUT:   %ptr: type = ptr_type %u8 [concrete]
+// CHECK:STDOUT:   %pattern_type.a66: type = pattern_type %ptr [concrete]
+// CHECK:STDOUT:   %ReturnU8__carbon_thunk.type: type = fn_type @ReturnU8__carbon_thunk [concrete]
+// CHECK:STDOUT:   %ReturnU8__carbon_thunk: %ReturnU8__carbon_thunk.type = struct_value () [concrete]
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: imports {
+// CHECK:STDOUT:   %Core: <namespace> = namespace file.%Core.import, [concrete] {
+// CHECK:STDOUT:     .UInt = %Core.UInt
+// CHECK:STDOUT:     import Core//prelude
+// CHECK:STDOUT:     import Core//prelude/...
+// CHECK:STDOUT:   }
+// CHECK:STDOUT:   %Cpp: <namespace> = namespace file.%Cpp.import_cpp, [concrete] {
+// CHECK:STDOUT:     .ReturnU8 = %ReturnU8.cpp_overload_set.value
+// CHECK:STDOUT:     import Cpp//...
+// CHECK:STDOUT:   }
+// CHECK:STDOUT:   %Core.UInt: %UInt.type = import_ref Core//prelude/types/uint, UInt, loaded [concrete = constants.%UInt.generic]
+// CHECK:STDOUT:   %ReturnU8.cpp_overload_set.value: %ReturnU8.cpp_overload_set.type = cpp_overload_set_value @ReturnU8.cpp_overload_set [concrete = constants.%ReturnU8.cpp_overload_set.value]
+// CHECK:STDOUT:   %ReturnU8__carbon_thunk.decl: %ReturnU8__carbon_thunk.type = fn_decl @ReturnU8__carbon_thunk [concrete = constants.%ReturnU8__carbon_thunk] {
+// CHECK:STDOUT:     %return.patt: %pattern_type.a66 = value_binding_pattern r#return [concrete]
+// CHECK:STDOUT:     %return.param_patt: %pattern_type.a66 = value_param_pattern %return.patt, call_param0 [concrete]
+// CHECK:STDOUT:   } {
+// CHECK:STDOUT:     %return.param: %ptr = value_param call_param0
+// CHECK:STDOUT:     %.1: type = splice_block constants.%ptr [concrete = constants.%ptr] {
+// CHECK:STDOUT:       %int_8: Core.IntLiteral = int_value 8 [concrete = constants.%int_8]
+// CHECK:STDOUT:       %u8: type = class_type @UInt, @UInt(constants.%int_8) [concrete = constants.%u8]
+// CHECK:STDOUT:     }
+// CHECK:STDOUT:     %return: %ptr = value_binding r#return, %return.param
+// CHECK:STDOUT:   }
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: file {
+// CHECK:STDOUT:   package: <namespace> = namespace [concrete] {
+// CHECK:STDOUT:     .Core = imports.%Core
+// CHECK:STDOUT:     .Cpp = imports.%Cpp
+// CHECK:STDOUT:     .GetU8 = %GetU8.decl
+// CHECK:STDOUT:   }
+// CHECK:STDOUT:   %Core.import = import Core
+// CHECK:STDOUT:   %Cpp.import_cpp = import_cpp {
+// CHECK:STDOUT:     import Cpp inline
+// CHECK:STDOUT:   }
+// CHECK:STDOUT:   %GetU8.decl: %GetU8.type = fn_decl @GetU8 [concrete = constants.%GetU8] {
+// CHECK:STDOUT:     %return.patt: %pattern_type.8f3 = return_slot_pattern [concrete]
+// CHECK:STDOUT:     %return.param_patt: %pattern_type.8f3 = out_param_pattern %return.patt, call_param0 [concrete]
+// CHECK:STDOUT:   } {
+// CHECK:STDOUT:     %int_8: Core.IntLiteral = int_value 8 [concrete = constants.%int_8]
+// CHECK:STDOUT:     %u8: type = class_type @UInt, @UInt(constants.%int_8) [concrete = constants.%u8]
+// CHECK:STDOUT:     %.loc8_15: form = init_form %u8, call_param0 [concrete = constants.%.98d]
+// CHECK:STDOUT:     %return.param: ref %u8 = out_param call_param0
+// CHECK:STDOUT:     %return: ref %u8 = return_slot %return.param
+// CHECK:STDOUT:   }
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: fn @GetU8() -> out %return.param: %u8 {
+// CHECK:STDOUT: !entry:
+// CHECK:STDOUT:   %Cpp.ref: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
+// CHECK:STDOUT:   %ReturnU8.ref: %ReturnU8.cpp_overload_set.type = name_ref ReturnU8, imports.%ReturnU8.cpp_overload_set.value [concrete = constants.%ReturnU8.cpp_overload_set.value]
+// CHECK:STDOUT:   %.loc8_40.1: ref %u8 = temporary_storage
+// CHECK:STDOUT:   %addr: %ptr = addr_of %.loc8_40.1
+// CHECK:STDOUT:   %ReturnU8__carbon_thunk.call: init %empty_tuple.type = call imports.%ReturnU8__carbon_thunk.decl(%addr)
+// CHECK:STDOUT:   %.loc8_40.2: init %u8 to %.loc8_40.1 = mark_in_place_init %ReturnU8__carbon_thunk.call
+// CHECK:STDOUT:   return %.loc8_40.2
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: fn @ReturnU8() -> out %return.param: %u8;
+// CHECK:STDOUT:
+// CHECK:STDOUT: fn @ReturnU8__carbon_thunk(%return.param: %ptr);
+// CHECK:STDOUT:
+// CHECK:STDOUT: --- var_from_thunk_by_value.carbon
+// CHECK:STDOUT:
+// CHECK:STDOUT: constants {
+// CHECK:STDOUT:   %Var.type: type = fn_type @Var [concrete]
+// CHECK:STDOUT:   %empty_tuple.type: type = tuple_type () [concrete]
+// CHECK:STDOUT:   %Var: %Var.type = struct_value () [concrete]
+// CHECK:STDOUT:   %int_32: Core.IntLiteral = int_value 32 [concrete]
+// CHECK:STDOUT:   %UInt.type: type = generic_class_type @UInt [concrete]
+// CHECK:STDOUT:   %UInt.generic: %UInt.type = struct_value () [concrete]
+// CHECK:STDOUT:   %u32: type = class_type @UInt, @UInt(%int_32) [concrete]
+// CHECK:STDOUT:   %pattern_type.4a9: type = pattern_type %u32 [concrete]
+// CHECK:STDOUT:   %ReturnU32.cpp_overload_set.type: type = cpp_overload_set_type @ReturnU32.cpp_overload_set [concrete]
+// CHECK:STDOUT:   %ReturnU32.cpp_overload_set.value: %ReturnU32.cpp_overload_set.type = cpp_overload_set_value @ReturnU32.cpp_overload_set [concrete]
+// CHECK:STDOUT:   %ReturnU32.type: type = fn_type @ReturnU32 [concrete]
+// CHECK:STDOUT:   %ReturnU32: %ReturnU32.type = struct_value () [concrete]
+// CHECK:STDOUT:   %Destroy.type: type = facet_type <@Destroy> [concrete]
+// CHECK:STDOUT:   %DestroyOp.type: type = fn_type @DestroyOp [concrete]
+// CHECK:STDOUT:   %DestroyOp: %DestroyOp.type = struct_value () [concrete]
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: imports {
+// CHECK:STDOUT:   %Core: <namespace> = namespace file.%Core.import, [concrete] {
+// CHECK:STDOUT:     .UInt = %Core.UInt
+// CHECK:STDOUT:     .Destroy = %Core.Destroy
+// CHECK:STDOUT:     import Core//prelude
+// CHECK:STDOUT:     import Core//prelude/...
+// CHECK:STDOUT:   }
+// CHECK:STDOUT:   %Cpp: <namespace> = namespace file.%Cpp.import_cpp, [concrete] {
+// CHECK:STDOUT:     .ReturnU32 = %ReturnU32.cpp_overload_set.value
+// CHECK:STDOUT:     import Cpp//...
+// CHECK:STDOUT:   }
+// CHECK:STDOUT:   %Core.UInt: %UInt.type = import_ref Core//prelude/types/uint, UInt, loaded [concrete = constants.%UInt.generic]
+// CHECK:STDOUT:   %ReturnU32.cpp_overload_set.value: %ReturnU32.cpp_overload_set.type = cpp_overload_set_value @ReturnU32.cpp_overload_set [concrete = constants.%ReturnU32.cpp_overload_set.value]
+// CHECK:STDOUT:   %ReturnU32.decl: %ReturnU32.type = fn_decl @ReturnU32 [concrete = constants.%ReturnU32] {
+// CHECK:STDOUT:     %return.patt: %pattern_type.4a9 = return_slot_pattern [concrete]
+// CHECK:STDOUT:     %return.param_patt: %pattern_type.4a9 = out_param_pattern %return.patt, call_param0 [concrete]
+// CHECK:STDOUT:   } {
+// CHECK:STDOUT:     %int_32: Core.IntLiteral = int_value 32 [concrete = constants.%int_32]
+// CHECK:STDOUT:     %u32: type = class_type @UInt, @UInt(constants.%int_32) [concrete = constants.%u32]
+// CHECK:STDOUT:     %return.param: ref %u32 = out_param call_param0
+// CHECK:STDOUT:     %return: ref %u32 = return_slot %return.param
+// CHECK:STDOUT:   }
+// CHECK:STDOUT:   %Core.Destroy: type = import_ref Core//prelude/destroy, Destroy, loaded [concrete = constants.%Destroy.type]
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: file {
+// CHECK:STDOUT:   package: <namespace> = namespace [concrete] {
+// CHECK:STDOUT:     .Core = imports.%Core
+// CHECK:STDOUT:     .Cpp = imports.%Cpp
+// CHECK:STDOUT:     .Var = %Var.decl
+// CHECK:STDOUT:   }
+// CHECK:STDOUT:   %Core.import = import Core
+// CHECK:STDOUT:   %Cpp.import_cpp = import_cpp {
+// CHECK:STDOUT:     import Cpp inline
+// CHECK:STDOUT:   }
+// CHECK:STDOUT:   %Var.decl: %Var.type = fn_decl @Var [concrete = constants.%Var] {} {}
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: fn @Var() {
+// CHECK:STDOUT: !entry:
+// CHECK:STDOUT:   name_binding_decl {
+// CHECK:STDOUT:     %my_u32.patt: %pattern_type.4a9 = ref_binding_pattern my_u32 [concrete]
+// CHECK:STDOUT:     %my_u32.var_patt: %pattern_type.4a9 = var_pattern %my_u32.patt [concrete]
+// CHECK:STDOUT:   }
+// CHECK:STDOUT:   %my_u32.var: ref %u32 = var %my_u32.var_patt
+// CHECK:STDOUT:   %Cpp.ref: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
+// CHECK:STDOUT:   %ReturnU32.ref: %ReturnU32.cpp_overload_set.type = name_ref ReturnU32, imports.%ReturnU32.cpp_overload_set.value [concrete = constants.%ReturnU32.cpp_overload_set.value]
+// CHECK:STDOUT:   %ReturnU32.call: init %u32 = call imports.%ReturnU32.decl()
+// CHECK:STDOUT:   assign %my_u32.var, %ReturnU32.call
+// CHECK:STDOUT:   %.loc9: type = splice_block %u32 [concrete = constants.%u32] {
+// CHECK:STDOUT:     %int_32: Core.IntLiteral = int_value 32 [concrete = constants.%int_32]
+// CHECK:STDOUT:     %u32: type = class_type @UInt, @UInt(constants.%int_32) [concrete = constants.%u32]
+// CHECK:STDOUT:   }
+// CHECK:STDOUT:   %my_u32: ref %u32 = ref_binding my_u32, %my_u32.var
+// CHECK:STDOUT:   %DestroyOp.bound: <bound method> = bound_method %my_u32.var, constants.%DestroyOp
+// CHECK:STDOUT:   %DestroyOp.call: init %empty_tuple.type = call %DestroyOp.bound(%my_u32.var)
+// CHECK:STDOUT:   return
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: fn @ReturnU32() -> out %return.param: %u32;
+// CHECK:STDOUT:
+// CHECK:STDOUT: fn @DestroyOp(%self.param: %u32) = "no_op";
+// CHECK:STDOUT:
diff --git a/toolchain/check/testdata/interop/cpp/function/struct.carbon b/toolchain/check/testdata/interop/cpp/function/struct.carbon
index a175c2ddbad3..f26d6d18c553 100644
--- a/toolchain/check/testdata/interop/cpp/function/struct.carbon
+++ b/toolchain/check/testdata/interop/cpp/function/struct.carbon
@@ -1005,7 +1005,7 @@ fn F() {
 // CHECK:STDOUT:   %.loc8_11.1: ref %S = temporary_storage
 // CHECK:STDOUT:   %addr: %ptr.5c7 = addr_of %.loc8_11.1
 // CHECK:STDOUT:   %foo__carbon_thunk.call: init %empty_tuple.type = call imports.%foo__carbon_thunk.decl(%addr)
-// CHECK:STDOUT:   %.loc8_11.2: init %S to %.loc8_11.1 = in_place_init %foo__carbon_thunk.call
+// CHECK:STDOUT:   %.loc8_11.2: init %S to %.loc8_11.1 = mark_in_place_init %foo__carbon_thunk.call
 // CHECK:STDOUT:   %.loc8_11.3: ref %S = temporary %.loc8_11.1, %.loc8_11.2
 // CHECK:STDOUT:   %S.cpp_destructor.bound: <bound method> = bound_method %.loc8_11.3, constants.%S.cpp_destructor
 // CHECK:STDOUT:   %S.cpp_destructor.call: init %empty_tuple.type = call %S.cpp_destructor.bound(%.loc8_11.3)
diff --git a/toolchain/check/testdata/interop/cpp/function/union.carbon b/toolchain/check/testdata/interop/cpp/function/union.carbon
index c5d5948ba2d8..5954702666a5 100644
--- a/toolchain/check/testdata/interop/cpp/function/union.carbon
+++ b/toolchain/check/testdata/interop/cpp/function/union.carbon
@@ -930,7 +930,7 @@ fn F() {
 // CHECK:STDOUT:   %.loc8_11.1: ref %U = temporary_storage
 // CHECK:STDOUT:   %addr: %ptr.86f = addr_of %.loc8_11.1
 // CHECK:STDOUT:   %foo__carbon_thunk.call: init %empty_tuple.type = call imports.%foo__carbon_thunk.decl(%addr)
-// CHECK:STDOUT:   %.loc8_11.2: init %U to %.loc8_11.1 = in_place_init %foo__carbon_thunk.call
+// CHECK:STDOUT:   %.loc8_11.2: init %U to %.loc8_11.1 = mark_in_place_init %foo__carbon_thunk.call
 // CHECK:STDOUT:   %.loc8_11.3: ref %U = temporary %.loc8_11.1, %.loc8_11.2
 // CHECK:STDOUT:   %U.cpp_destructor.bound: <bound method> = bound_method %.loc8_11.3, constants.%U.cpp_destructor
 // CHECK:STDOUT:   %U.cpp_destructor.call: init %empty_tuple.type = call %U.cpp_destructor.bound(%.loc8_11.3)
diff --git a/toolchain/check/testdata/interop/cpp/impls/as.carbon b/toolchain/check/testdata/interop/cpp/impls/as.carbon
index 5a8d93187bc2..4f3b48f45eab 100644
--- a/toolchain/check/testdata/interop/cpp/impls/as.carbon
+++ b/toolchain/check/testdata/interop/cpp/impls/as.carbon
@@ -231,7 +231,7 @@ fn ConversionExplicit(s: Cpp.ConditionallyExplicitFalse) {
 // CHECK:STDOUT:   %.loc8_5.1: ref %Dest = temporary_storage
 // CHECK:STDOUT:   %addr: %ptr.551 = addr_of %.loc8_5.1
 // CHECK:STDOUT:   %Dest__carbon_thunk.call: init %empty_tuple.type = call imports.%Dest__carbon_thunk.decl.b58ecd.1(%s.ref, %addr)
-// CHECK:STDOUT:   %.loc8_5.2: init %Dest to %.loc8_5.1 = in_place_init %Dest__carbon_thunk.call
+// CHECK:STDOUT:   %.loc8_5.2: init %Dest to %.loc8_5.1 = mark_in_place_init %Dest__carbon_thunk.call
 // CHECK:STDOUT:   %.loc8_5.3: init %Dest = converted %s.ref, %.loc8_5.2
 // CHECK:STDOUT:   %.loc8_5.4: ref %Dest = temporary %.loc8_5.1, %.loc8_5.3
 // CHECK:STDOUT:   %Dest.cpp_destructor.bound: <bound method> = bound_method %.loc8_5.4, constants.%Dest.cpp_destructor
@@ -251,7 +251,7 @@ fn ConversionExplicit(s: Cpp.ConditionallyExplicitFalse) {
 // CHECK:STDOUT:   %addr.loc14_5.1: %ptr.472 = addr_of %.loc14_3
 // CHECK:STDOUT:   %addr.loc14_5.2: %ptr.9ae = addr_of %.loc14_5.1
 // CHECK:STDOUT:   %Dest2__carbon_thunk.call: init %empty_tuple.type = call imports.%Dest2__carbon_thunk.decl(%addr.loc14_5.1, %addr.loc14_5.2)
-// CHECK:STDOUT:   %.loc14_5.2: init %Dest2 to %.loc14_5.1 = in_place_init %Dest2__carbon_thunk.call
+// CHECK:STDOUT:   %.loc14_5.2: init %Dest2 to %.loc14_5.1 = mark_in_place_init %Dest2__carbon_thunk.call
 // CHECK:STDOUT:   %.loc14_5.3: init %Dest2 = converted %s.ref, %.loc14_5.2
 // CHECK:STDOUT:   %.loc14_5.4: ref %Dest2 = temporary %.loc14_5.1, %.loc14_5.3
 // CHECK:STDOUT:   %Dest2.cpp_destructor.bound: <bound method> = bound_method %.loc14_5.4, constants.%Dest2.cpp_destructor
@@ -271,7 +271,7 @@ fn ConversionExplicit(s: Cpp.ConditionallyExplicitFalse) {
 // CHECK:STDOUT:   %addr.loc20_5.1: %ptr.1fc = addr_of %.loc20_3
 // CHECK:STDOUT:   %addr.loc20_5.2: %ptr.5b5 = addr_of %.loc20_5.1
 // CHECK:STDOUT:   %ExplicitConstructor__carbon_thunk.call: init %empty_tuple.type = call imports.%ExplicitConstructor__carbon_thunk.decl(%addr.loc20_5.1, %addr.loc20_5.2)
-// CHECK:STDOUT:   %.loc20_5.2: init %ExplicitConstructor to %.loc20_5.1 = in_place_init %ExplicitConstructor__carbon_thunk.call
+// CHECK:STDOUT:   %.loc20_5.2: init %ExplicitConstructor to %.loc20_5.1 = mark_in_place_init %ExplicitConstructor__carbon_thunk.call
 // CHECK:STDOUT:   %.loc20_5.3: init %ExplicitConstructor = converted %s.ref, %.loc20_5.2
 // CHECK:STDOUT:   %.loc20_5.4: ref %ExplicitConstructor = temporary %.loc20_5.1, %.loc20_5.3
 // CHECK:STDOUT:   %ExplicitConstructor.cpp_destructor.bound: <bound method> = bound_method %.loc20_5.4, constants.%ExplicitConstructor.cpp_destructor
@@ -290,7 +290,7 @@ fn ConversionExplicit(s: Cpp.ConditionallyExplicitFalse) {
 // CHECK:STDOUT:   %.loc26_5.1: ref %Dest = temporary_storage
 // CHECK:STDOUT:   %addr: %ptr.551 = addr_of %.loc26_5.1
 // CHECK:STDOUT:   %Dest__carbon_thunk.call: init %empty_tuple.type = call imports.%Dest__carbon_thunk.decl.b58ecd.2(%s.ref, %addr)
-// CHECK:STDOUT:   %.loc26_5.2: init %Dest to %.loc26_5.1 = in_place_init %Dest__carbon_thunk.call
+// CHECK:STDOUT:   %.loc26_5.2: init %Dest to %.loc26_5.1 = mark_in_place_init %Dest__carbon_thunk.call
 // CHECK:STDOUT:   %.loc26_5.3: init %Dest = converted %s.ref, %.loc26_5.2
 // CHECK:STDOUT:   %.loc26_5.4: ref %Dest = temporary %.loc26_5.1, %.loc26_5.3
 // CHECK:STDOUT:   %Dest.cpp_destructor.bound: <bound method> = bound_method %.loc26_5.4, constants.%Dest.cpp_destructor
@@ -381,7 +381,7 @@ fn ConversionExplicit(s: Cpp.ConditionallyExplicitFalse) {
 // CHECK:STDOUT:   %addr.loc8_43.1: %ptr.1fc = addr_of %.loc8_43.2
 // CHECK:STDOUT:   %addr.loc8_43.2: %ptr.ca4178.1 = addr_of %.loc8_43.1
 // CHECK:STDOUT:   %ConditionallyExplicit__carbon_thunk.call.loc8: init %empty_tuple.type = call imports.%ConditionallyExplicit__carbon_thunk.decl.22daaa.1(%addr.loc8_43.1, %addr.loc8_43.2)
-// CHECK:STDOUT:   %.loc8_43.3: init %ConditionallyExplicit.c52b91.1 to %.loc8_43.1 = in_place_init %ConditionallyExplicit__carbon_thunk.call.loc8
+// CHECK:STDOUT:   %.loc8_43.3: init %ConditionallyExplicit.c52b91.1 to %.loc8_43.1 = mark_in_place_init %ConditionallyExplicit__carbon_thunk.call.loc8
 // CHECK:STDOUT:   %.loc8_43.4: init %ConditionallyExplicit.c52b91.1 = converted %s.ref.loc8, %.loc8_43.3
 // CHECK:STDOUT:   %.loc8_43.5: ref %ConditionallyExplicit.c52b91.1 = temporary %.loc8_43.1, %.loc8_43.4
 // CHECK:STDOUT:   %.loc8_43.6: %ConditionallyExplicit.c52b91.1 = acquire_value %.loc8_43.5
@@ -394,7 +394,7 @@ fn ConversionExplicit(s: Cpp.ConditionallyExplicitFalse) {
 // CHECK:STDOUT:   %addr.loc9_5.1: %ptr.1fc = addr_of %.loc9_3
 // CHECK:STDOUT:   %addr.loc9_5.2: %ptr.ca4178.1 = addr_of %.loc9_5.1
 // CHECK:STDOUT:   %ConditionallyExplicit__carbon_thunk.call.loc9: init %empty_tuple.type = call imports.%ConditionallyExplicit__carbon_thunk.decl.22daaa.1(%addr.loc9_5.1, %addr.loc9_5.2)
-// CHECK:STDOUT:   %.loc9_5.2: init %ConditionallyExplicit.c52b91.1 to %.loc9_5.1 = in_place_init %ConditionallyExplicit__carbon_thunk.call.loc9
+// CHECK:STDOUT:   %.loc9_5.2: init %ConditionallyExplicit.c52b91.1 to %.loc9_5.1 = mark_in_place_init %ConditionallyExplicit__carbon_thunk.call.loc9
 // CHECK:STDOUT:   %.loc9_5.3: init %ConditionallyExplicit.c52b91.1 = converted %s.ref.loc9, %.loc9_5.2
 // CHECK:STDOUT:   %.loc9_5.4: ref %ConditionallyExplicit.c52b91.1 = temporary %.loc9_5.1, %.loc9_5.3
 // CHECK:STDOUT:   %ConditionallyExplicit.cpp_destructor.bound.loc9: <bound method> = bound_method %.loc9_5.4, constants.%ConditionallyExplicit.cpp_destructor.1ba031.1
@@ -416,7 +416,7 @@ fn ConversionExplicit(s: Cpp.ConditionallyExplicitFalse) {
 // CHECK:STDOUT:   %addr.loc15_5.1: %ptr.1fc = addr_of %.loc15_3
 // CHECK:STDOUT:   %addr.loc15_5.2: %ptr.ca4178.2 = addr_of %.loc15_5.1
 // CHECK:STDOUT:   %ConditionallyExplicit__carbon_thunk.call: init %empty_tuple.type = call imports.%ConditionallyExplicit__carbon_thunk.decl.22daaa.2(%addr.loc15_5.1, %addr.loc15_5.2)
-// CHECK:STDOUT:   %.loc15_5.2: init %ConditionallyExplicit.c52b91.2 to %.loc15_5.1 = in_place_init %ConditionallyExplicit__carbon_thunk.call
+// CHECK:STDOUT:   %.loc15_5.2: init %ConditionallyExplicit.c52b91.2 to %.loc15_5.1 = mark_in_place_init %ConditionallyExplicit__carbon_thunk.call
 // CHECK:STDOUT:   %.loc15_5.3: init %ConditionallyExplicit.c52b91.2 = converted %s.ref, %.loc15_5.2
 // CHECK:STDOUT:   %.loc15_5.4: ref %ConditionallyExplicit.c52b91.2 = temporary %.loc15_5.1, %.loc15_5.3
 // CHECK:STDOUT:   %ConditionallyExplicit.cpp_destructor.bound: <bound method> = bound_method %.loc15_5.4, constants.%ConditionallyExplicit.cpp_destructor.1ba031.2
@@ -440,7 +440,7 @@ fn ConversionExplicit(s: Cpp.ConditionallyExplicitFalse) {
 // CHECK:STDOUT:   %.loc21_21.1: ref %Dest = temporary_storage
 // CHECK:STDOUT:   %addr.loc21: %ptr.551 = addr_of %.loc21_21.1
 // CHECK:STDOUT:   %Dest__carbon_thunk.call.loc21: init %empty_tuple.type = call imports.%Dest__carbon_thunk.decl(%s.ref.loc21, %addr.loc21)
-// CHECK:STDOUT:   %.loc21_21.2: init %Dest to %.loc21_21.1 = in_place_init %Dest__carbon_thunk.call.loc21
+// CHECK:STDOUT:   %.loc21_21.2: init %Dest to %.loc21_21.1 = mark_in_place_init %Dest__carbon_thunk.call.loc21
 // CHECK:STDOUT:   %.loc21_21.3: init %Dest = converted %s.ref.loc21, %.loc21_21.2
 // CHECK:STDOUT:   %.loc21_21.4: ref %Dest = temporary %.loc21_21.1, %.loc21_21.3
 // CHECK:STDOUT:   %.loc21_21.5: %Dest = acquire_value %.loc21_21.4
@@ -452,7 +452,7 @@ fn ConversionExplicit(s: Cpp.ConditionallyExplicitFalse) {
 // CHECK:STDOUT:   %.loc22_5.1: ref %Dest = temporary_storage
 // CHECK:STDOUT:   %addr.loc22: %ptr.551 = addr_of %.loc22_5.1
 // CHECK:STDOUT:   %Dest__carbon_thunk.call.loc22: init %empty_tuple.type = call imports.%Dest__carbon_thunk.decl(%s.ref.loc22, %addr.loc22)
-// CHECK:STDOUT:   %.loc22_5.2: init %Dest to %.loc22_5.1 = in_place_init %Dest__carbon_thunk.call.loc22
+// CHECK:STDOUT:   %.loc22_5.2: init %Dest to %.loc22_5.1 = mark_in_place_init %Dest__carbon_thunk.call.loc22
 // CHECK:STDOUT:   %.loc22_5.3: init %Dest = converted %s.ref.loc22, %.loc22_5.2
 // CHECK:STDOUT:   %.loc22_5.4: ref %Dest = temporary %.loc22_5.1, %.loc22_5.3
 // CHECK:STDOUT:   %Dest.cpp_destructor.bound.loc22: <bound method> = bound_method %.loc22_5.4, constants.%Dest.cpp_destructor
@@ -473,7 +473,7 @@ fn ConversionExplicit(s: Cpp.ConditionallyExplicitFalse) {
 // CHECK:STDOUT:   %.loc28_5.1: ref %Dest = temporary_storage
 // CHECK:STDOUT:   %addr: %ptr.551 = addr_of %.loc28_5.1
 // CHECK:STDOUT:   %Dest__carbon_thunk.call: init %empty_tuple.type = call imports.%Dest__carbon_thunk.decl(%s.ref, %addr)
-// CHECK:STDOUT:   %.loc28_5.2: init %Dest to %.loc28_5.1 = in_place_init %Dest__carbon_thunk.call
+// CHECK:STDOUT:   %.loc28_5.2: init %Dest to %.loc28_5.1 = mark_in_place_init %Dest__carbon_thunk.call
 // CHECK:STDOUT:   %.loc28_5.3: init %Dest = converted %s.ref, %.loc28_5.2
 // CHECK:STDOUT:   %.loc28_5.4: ref %Dest = temporary %.loc28_5.1, %.loc28_5.3
 // CHECK:STDOUT:   %Dest.cpp_destructor.bound: <bound method> = bound_method %.loc28_5.4, constants.%Dest.cpp_destructor
@@ -558,7 +558,7 @@ fn ConversionExplicit(s: Cpp.ConditionallyExplicitFalse) {
 // CHECK:STDOUT:   %.loc21_21.1: ref %Dest.5e7 = temporary_storage
 // CHECK:STDOUT:   %addr: %ptr.551 = addr_of %.loc21_21.1
 // CHECK:STDOUT:   %Dest__carbon_thunk.call: init %empty_tuple.type = call imports.%Dest__carbon_thunk.decl(%s.ref, %addr)
-// CHECK:STDOUT:   %.loc21_21.2: init %Dest.5e7 to %.loc21_21.1 = in_place_init %Dest__carbon_thunk.call
+// CHECK:STDOUT:   %.loc21_21.2: init %Dest.5e7 to %.loc21_21.1 = mark_in_place_init %Dest__carbon_thunk.call
 // CHECK:STDOUT:   %.loc21_21.3: init %Dest.5e7 = converted %s.ref, %.loc21_21.2
 // CHECK:STDOUT:   %.loc21_21.4: ref %Dest.5e7 = temporary %.loc21_21.1, %.loc21_21.3
 // CHECK:STDOUT:   %.loc21_21.5: %Dest.5e7 = acquire_value %.loc21_21.4
diff --git a/toolchain/check/testdata/interop/cpp/impls/copy.carbon b/toolchain/check/testdata/interop/cpp/impls/copy.carbon
index 370fdb580eb4..50837e9f4612 100644
--- a/toolchain/check/testdata/interop/cpp/impls/copy.carbon
+++ b/toolchain/check/testdata/interop/cpp/impls/copy.carbon
@@ -264,7 +264,7 @@ fn EqualWitnesses(p: Wrap(Cpp.Copyable)*) -> Wrap(Cpp.Copyable)* {
 // CHECK:STDOUT:   %.loc8_10.4: %ptr.29d = converted %addr.loc8_10.1, %.loc8_10.3
 // CHECK:STDOUT:   %addr.loc8_10.2: %ptr.e47 = addr_of %.loc6_40.1
 // CHECK:STDOUT:   %Copyable__carbon_thunk.call: init %empty_tuple.type = call imports.%Copyable__carbon_thunk.decl(%.loc8_10.4, %addr.loc8_10.2)
-// CHECK:STDOUT:   %.loc8_10.5: init %Copyable to %.loc6_40.1 = in_place_init %Copyable__carbon_thunk.call
+// CHECK:STDOUT:   %.loc8_10.5: init %Copyable to %.loc6_40.1 = mark_in_place_init %Copyable__carbon_thunk.call
 // CHECK:STDOUT:   return %.loc8_10.5 to %return.param
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
@@ -283,7 +283,7 @@ fn EqualWitnesses(p: Wrap(Cpp.Copyable)*) -> Wrap(Cpp.Copyable)* {
 // CHECK:STDOUT:   %.loc14_10.4: %ptr.093 = converted %addr.loc14_10.1, %.loc14_10.3
 // CHECK:STDOUT:   %addr.loc14_10.2: %ptr.84c = addr_of %.loc12_48.1
 // CHECK:STDOUT:   %ExplicitCopy__carbon_thunk.call: init %empty_tuple.type = call imports.%ExplicitCopy__carbon_thunk.decl(%.loc14_10.4, %addr.loc14_10.2)
-// CHECK:STDOUT:   %.loc14_10.5: init %ExplicitCopy to %.loc12_48.1 = in_place_init %ExplicitCopy__carbon_thunk.call
+// CHECK:STDOUT:   %.loc14_10.5: init %ExplicitCopy to %.loc12_48.1 = mark_in_place_init %ExplicitCopy__carbon_thunk.call
 // CHECK:STDOUT:   return %.loc14_10.5 to %return.param
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
diff --git a/toolchain/check/testdata/interop/cpp/impls/implicit_as.carbon b/toolchain/check/testdata/interop/cpp/impls/implicit_as.carbon
index ddd46e87c0b9..b4aedbb29705 100644
--- a/toolchain/check/testdata/interop/cpp/impls/implicit_as.carbon
+++ b/toolchain/check/testdata/interop/cpp/impls/implicit_as.carbon
@@ -512,7 +512,7 @@ fn InitFromStruct() {
 // CHECK:STDOUT:   %.loc8_21.1: ref %Dest = temporary_storage
 // CHECK:STDOUT:   %addr: %ptr.551 = addr_of %.loc8_21.1
 // CHECK:STDOUT:   %Dest__carbon_thunk.call: init %empty_tuple.type = call imports.%Dest__carbon_thunk.decl.b58ecd.1(%s.ref, %addr)
-// CHECK:STDOUT:   %.loc8_21.2: init %Dest to %.loc8_21.1 = in_place_init %Dest__carbon_thunk.call
+// CHECK:STDOUT:   %.loc8_21.2: init %Dest to %.loc8_21.1 = mark_in_place_init %Dest__carbon_thunk.call
 // CHECK:STDOUT:   %.loc8_21.3: init %Dest = converted %s.ref, %.loc8_21.2
 // CHECK:STDOUT:   %.loc8_21.4: ref %Dest = temporary %.loc8_21.1, %.loc8_21.3
 // CHECK:STDOUT:   %.loc8_21.5: %Dest = acquire_value %.loc8_21.4
@@ -538,7 +538,7 @@ fn InitFromStruct() {
 // CHECK:STDOUT:   %.loc14_21.1: ref %Dest = temporary_storage
 // CHECK:STDOUT:   %addr: %ptr.551 = addr_of %.loc14_21.1
 // CHECK:STDOUT:   %Dest__carbon_thunk.call: init %empty_tuple.type = call imports.%Dest__carbon_thunk.decl.b58ecd.2(%s.ref, %addr)
-// CHECK:STDOUT:   %.loc14_21.2: init %Dest to %.loc14_21.1 = in_place_init %Dest__carbon_thunk.call
+// CHECK:STDOUT:   %.loc14_21.2: init %Dest to %.loc14_21.1 = mark_in_place_init %Dest__carbon_thunk.call
 // CHECK:STDOUT:   %.loc14_21.3: init %Dest = converted %s.ref, %.loc14_21.2
 // CHECK:STDOUT:   %.loc14_21.4: ref %Dest = temporary %.loc14_21.1, %.loc14_21.3
 // CHECK:STDOUT:   %.loc14_21.5: %Dest = acquire_value %.loc14_21.4
@@ -563,7 +563,7 @@ fn InitFromStruct() {
 // CHECK:STDOUT:   %addr.loc20_22.1: %ptr.472 = addr_of %.loc20_22.2
 // CHECK:STDOUT:   %addr.loc20_22.2: %ptr.9ae = addr_of %.loc20_22.1
 // CHECK:STDOUT:   %Dest2__carbon_thunk.call: init %empty_tuple.type = call imports.%Dest2__carbon_thunk.decl(%addr.loc20_22.1, %addr.loc20_22.2)
-// CHECK:STDOUT:   %.loc20_22.3: init %Dest2 to %.loc20_22.1 = in_place_init %Dest2__carbon_thunk.call
+// CHECK:STDOUT:   %.loc20_22.3: init %Dest2 to %.loc20_22.1 = mark_in_place_init %Dest2__carbon_thunk.call
 // CHECK:STDOUT:   %.loc20_22.4: init %Dest2 = converted %s.ref, %.loc20_22.3
 // CHECK:STDOUT:   %.loc20_22.5: ref %Dest2 = temporary %.loc20_22.1, %.loc20_22.4
 // CHECK:STDOUT:   %.loc20_22.6: %Dest2 = acquire_value %.loc20_22.5
@@ -630,7 +630,7 @@ fn InitFromStruct() {
 // CHECK:STDOUT:   %.loc15_21.1: ref %Dest = temporary_storage
 // CHECK:STDOUT:   %addr: %ptr.551 = addr_of %.loc15_21.1
 // CHECK:STDOUT:   %Dest__carbon_thunk.call: init %empty_tuple.type = call imports.%Dest__carbon_thunk.decl(<error>, %addr)
-// CHECK:STDOUT:   %.loc15_21.2: init %Dest to %.loc15_21.1 = in_place_init %Dest__carbon_thunk.call
+// CHECK:STDOUT:   %.loc15_21.2: init %Dest to %.loc15_21.1 = mark_in_place_init %Dest__carbon_thunk.call
 // CHECK:STDOUT:   %.loc15_21.3: init %Dest = converted %s.ref, %.loc15_21.2
 // CHECK:STDOUT:   %.loc15_21.4: ref %Dest = temporary %.loc15_21.1, %.loc15_21.3
 // CHECK:STDOUT:   %.loc15_21.5: %Dest = acquire_value %.loc15_21.4
@@ -716,7 +716,7 @@ fn InitFromStruct() {
 // CHECK:STDOUT:   %addr.loc16_40.1: %ptr.1fc = addr_of %.loc16_40.2
 // CHECK:STDOUT:   %addr.loc16_40.2: %ptr.12d = addr_of %.loc16_40.1
 // CHECK:STDOUT:   %InaccessibleConstructor__carbon_thunk.call: init %empty_tuple.type = call imports.%InaccessibleConstructor__carbon_thunk.decl(%addr.loc16_40.1, %addr.loc16_40.2)
-// CHECK:STDOUT:   %.loc16_40.3: init %InaccessibleConstructor to %.loc16_40.1 = in_place_init %InaccessibleConstructor__carbon_thunk.call
+// CHECK:STDOUT:   %.loc16_40.3: init %InaccessibleConstructor to %.loc16_40.1 = mark_in_place_init %InaccessibleConstructor__carbon_thunk.call
 // CHECK:STDOUT:   %.loc16_40.4: init %InaccessibleConstructor = converted %s.ref, %.loc16_40.3
 // CHECK:STDOUT:   %.loc16_40.5: ref %InaccessibleConstructor = temporary %.loc16_40.1, %.loc16_40.4
 // CHECK:STDOUT:   %.loc16_40.6: %InaccessibleConstructor = acquire_value %.loc16_40.5
@@ -742,7 +742,7 @@ fn InitFromStruct() {
 // CHECK:STDOUT:   %.loc30_21.1: ref %Dest = temporary_storage
 // CHECK:STDOUT:   %addr: %ptr.551 = addr_of %.loc30_21.1
 // CHECK:STDOUT:   %Dest__carbon_thunk.call: init %empty_tuple.type = call imports.%Dest__carbon_thunk.decl(%s.ref, %addr)
-// CHECK:STDOUT:   %.loc30_21.2: init %Dest to %.loc30_21.1 = in_place_init %Dest__carbon_thunk.call
+// CHECK:STDOUT:   %.loc30_21.2: init %Dest to %.loc30_21.1 = mark_in_place_init %Dest__carbon_thunk.call
 // CHECK:STDOUT:   %.loc30_21.3: init %Dest = converted %s.ref, %.loc30_21.2
 // CHECK:STDOUT:   %.loc30_21.4: ref %Dest = temporary %.loc30_21.1, %.loc30_21.3
 // CHECK:STDOUT:   %.loc30_21.5: %Dest = acquire_value %.loc30_21.4
@@ -905,7 +905,7 @@ fn InitFromStruct() {
 // CHECK:STDOUT:   %.loc8_31.1: ref %IntConstructor.f49 = temporary_storage
 // CHECK:STDOUT:   %addr: %ptr.d59 = addr_of %.loc8_31.1
 // CHECK:STDOUT:   %IntConstructor__carbon_thunk.call: init %empty_tuple.type = call imports.%IntConstructor__carbon_thunk.decl(%i.ref, %addr)
-// CHECK:STDOUT:   %.loc8_31.2: init %IntConstructor.f49 to %.loc8_31.1 = in_place_init %IntConstructor__carbon_thunk.call
+// CHECK:STDOUT:   %.loc8_31.2: init %IntConstructor.f49 to %.loc8_31.1 = mark_in_place_init %IntConstructor__carbon_thunk.call
 // CHECK:STDOUT:   %.loc8_31.3: init %IntConstructor.f49 = converted %i.ref, %.loc8_31.2
 // CHECK:STDOUT:   %.loc8_31.4: ref %IntConstructor.f49 = temporary %.loc8_31.1, %.loc8_31.3
 // CHECK:STDOUT:   %.loc8_31.5: %IntConstructor.f49 = acquire_value %.loc8_31.4
@@ -960,7 +960,7 @@ fn InitFromStruct() {
 // CHECK:STDOUT:   %.loc19_31.2: %i32 = converted %u.ref, <error> [concrete = <error>]
 // CHECK:STDOUT:   %addr: %ptr.d59 = addr_of %.loc19_31.1
 // CHECK:STDOUT:   %IntConstructor__carbon_thunk.call: init %empty_tuple.type = call imports.%IntConstructor__carbon_thunk.decl(<error>, %addr)
-// CHECK:STDOUT:   %.loc19_31.3: init %IntConstructor to %.loc19_31.1 = in_place_init %IntConstructor__carbon_thunk.call
+// CHECK:STDOUT:   %.loc19_31.3: init %IntConstructor to %.loc19_31.1 = mark_in_place_init %IntConstructor__carbon_thunk.call
 // CHECK:STDOUT:   %.loc19_31.4: init %IntConstructor = converted %u.ref, %.loc19_31.3
 // CHECK:STDOUT:   %.loc19_31.5: ref %IntConstructor = temporary %.loc19_31.1, %.loc19_31.4
 // CHECK:STDOUT:   %.loc19_31.6: %IntConstructor = acquire_value %.loc19_31.5
@@ -1015,7 +1015,7 @@ fn InitFromStruct() {
 // CHECK:STDOUT:   %.loc9_36.2: ref %DefaultConstructor = temporary_storage
 // CHECK:STDOUT:   %addr: %ptr.3f7 = addr_of %.loc9_36.2
 // CHECK:STDOUT:   %DefaultConstructor__carbon_thunk.call: init %empty_tuple.type = call imports.%DefaultConstructor__carbon_thunk.decl(%addr)
-// CHECK:STDOUT:   %.loc9_36.3: init %DefaultConstructor to %.loc9_36.2 = in_place_init %DefaultConstructor__carbon_thunk.call
+// CHECK:STDOUT:   %.loc9_36.3: init %DefaultConstructor to %.loc9_36.2 = mark_in_place_init %DefaultConstructor__carbon_thunk.call
 // CHECK:STDOUT:   %.loc9_36.4: init %DefaultConstructor = converted %.loc9_36.1, %.loc9_36.3
 // CHECK:STDOUT:   %.loc9_36.5: ref %DefaultConstructor = temporary %.loc9_36.2, %.loc9_36.4
 // CHECK:STDOUT:   %.loc9_36.6: %DefaultConstructor = acquire_value %.loc9_36.5
@@ -1150,7 +1150,7 @@ fn InitFromStruct() {
 // CHECK:STDOUT:   %.loc8_24.2: %i32 = converted %int_2.loc8, %.loc8_24.1 [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %addr.loc8: %ptr.677 = addr_of %.loc8_25.2
 // CHECK:STDOUT:   %Two__carbon_thunk.call: init %empty_tuple.type = call imports.%Two__carbon_thunk.decl(%.loc8_21.2, %.loc8_24.2, %addr.loc8)
-// CHECK:STDOUT:   %.loc8_25.3: init %Two to %.loc8_25.2 = in_place_init %Two__carbon_thunk.call
+// CHECK:STDOUT:   %.loc8_25.3: init %Two to %.loc8_25.2 = mark_in_place_init %Two__carbon_thunk.call
 // CHECK:STDOUT:   %.loc8_25.4: init %Two = converted %.loc8_25.1, %.loc8_25.3
 // CHECK:STDOUT:   %.loc8_25.5: ref %Two = temporary %.loc8_25.2, %.loc8_25.4
 // CHECK:STDOUT:   %.loc8_25.6: %Two = acquire_value %.loc8_25.5
@@ -1182,7 +1182,7 @@ fn InitFromStruct() {
 // CHECK:STDOUT:   %.loc10_37.2: %i32 = converted %int_2.loc10, %.loc10_37.1 [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %addr.loc10: %ptr.ea4 = addr_of %.loc10_38.2
 // CHECK:STDOUT:   %ThreeWithDefault__carbon_thunk.call.loc10: init %empty_tuple.type = call imports.%ThreeWithDefault__carbon_thunk.decl.482856.1(%.loc10_34.2, %.loc10_37.2, %addr.loc10)
-// CHECK:STDOUT:   %.loc10_38.3: init %ThreeWithDefault to %.loc10_38.2 = in_place_init %ThreeWithDefault__carbon_thunk.call.loc10
+// CHECK:STDOUT:   %.loc10_38.3: init %ThreeWithDefault to %.loc10_38.2 = mark_in_place_init %ThreeWithDefault__carbon_thunk.call.loc10
 // CHECK:STDOUT:   %.loc10_38.4: init %ThreeWithDefault = converted %.loc10_38.1, %.loc10_38.3
 // CHECK:STDOUT:   %.loc10_38.5: ref %ThreeWithDefault = temporary %.loc10_38.2, %.loc10_38.4
 // CHECK:STDOUT:   %.loc10_38.6: %ThreeWithDefault = acquire_value %.loc10_38.5
@@ -1222,7 +1222,7 @@ fn InitFromStruct() {
 // CHECK:STDOUT:   %.loc12_40.2: %i32 = converted %int_3, %.loc12_40.1 [concrete = constants.%int_3.822]
 // CHECK:STDOUT:   %addr.loc12: %ptr.ea4 = addr_of %.loc12_41.2
 // CHECK:STDOUT:   %ThreeWithDefault__carbon_thunk.call.loc12: init %empty_tuple.type = call imports.%ThreeWithDefault__carbon_thunk.decl.482856.2(%.loc12_34.2, %.loc12_37.2, %.loc12_40.2, %addr.loc12)
-// CHECK:STDOUT:   %.loc12_41.3: init %ThreeWithDefault to %.loc12_41.2 = in_place_init %ThreeWithDefault__carbon_thunk.call.loc12
+// CHECK:STDOUT:   %.loc12_41.3: init %ThreeWithDefault to %.loc12_41.2 = mark_in_place_init %ThreeWithDefault__carbon_thunk.call.loc12
 // CHECK:STDOUT:   %.loc12_41.4: init %ThreeWithDefault = converted %.loc12_41.1, %.loc12_41.3
 // CHECK:STDOUT:   %.loc12_41.5: ref %ThreeWithDefault = temporary %.loc12_41.2, %.loc12_41.4
 // CHECK:STDOUT:   %.loc12_41.6: %ThreeWithDefault = acquire_value %.loc12_41.5
@@ -1443,7 +1443,7 @@ fn InitFromStruct() {
 // CHECK:STDOUT:   %.loc8_30.2: ref %NonAggregate = temporary_storage
 // CHECK:STDOUT:   %addr.loc8: %ptr.9b6 = addr_of %.loc8_30.2
 // CHECK:STDOUT:   %NonAggregate__carbon_thunk.call.loc8: init %empty_tuple.type = call imports.%NonAggregate__carbon_thunk.decl.712b28.1(%addr.loc8)
-// CHECK:STDOUT:   %.loc8_30.3: init %NonAggregate to %.loc8_30.2 = in_place_init %NonAggregate__carbon_thunk.call.loc8
+// CHECK:STDOUT:   %.loc8_30.3: init %NonAggregate to %.loc8_30.2 = mark_in_place_init %NonAggregate__carbon_thunk.call.loc8
 // CHECK:STDOUT:   %.loc8_30.4: init %NonAggregate = converted %.loc8_30.1, %.loc8_30.3
 // CHECK:STDOUT:   %.loc8_30.5: ref %NonAggregate = temporary %.loc8_30.2, %.loc8_30.4
 // CHECK:STDOUT:   %.loc8_30.6: %NonAggregate = acquire_value %.loc8_30.5
@@ -1467,7 +1467,7 @@ fn InitFromStruct() {
 // CHECK:STDOUT:   %.loc9_30.2: %i32 = converted %int_1.loc9, %.loc9_30.1 [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %addr.loc9: %ptr.9b6 = addr_of %.loc9_32.2
 // CHECK:STDOUT:   %NonAggregate__carbon_thunk.call.loc9: init %empty_tuple.type = call imports.%NonAggregate__carbon_thunk.decl.712b28.2(%.loc9_30.2, %addr.loc9)
-// CHECK:STDOUT:   %.loc9_32.3: init %NonAggregate to %.loc9_32.2 = in_place_init %NonAggregate__carbon_thunk.call.loc9
+// CHECK:STDOUT:   %.loc9_32.3: init %NonAggregate to %.loc9_32.2 = mark_in_place_init %NonAggregate__carbon_thunk.call.loc9
 // CHECK:STDOUT:   %.loc9_32.4: init %NonAggregate = converted %.loc9_32.1, %.loc9_32.3
 // CHECK:STDOUT:   %.loc9_32.5: ref %NonAggregate = temporary %.loc9_32.2, %.loc9_32.4
 // CHECK:STDOUT:   %.loc9_32.6: %NonAggregate = acquire_value %.loc9_32.5
@@ -1499,7 +1499,7 @@ fn InitFromStruct() {
 // CHECK:STDOUT:   %.loc10_33.2: %i32 = converted %int_2, %.loc10_33.1 [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %addr.loc10: %ptr.9b6 = addr_of %.loc10_34.2
 // CHECK:STDOUT:   %NonAggregate__carbon_thunk.call.loc10: init %empty_tuple.type = call imports.%NonAggregate__carbon_thunk.decl.712b28.3(%.loc10_30.2, %.loc10_33.2, %addr.loc10)
-// CHECK:STDOUT:   %.loc10_34.3: init %NonAggregate to %.loc10_34.2 = in_place_init %NonAggregate__carbon_thunk.call.loc10
+// CHECK:STDOUT:   %.loc10_34.3: init %NonAggregate to %.loc10_34.2 = mark_in_place_init %NonAggregate__carbon_thunk.call.loc10
 // CHECK:STDOUT:   %.loc10_34.4: init %NonAggregate = converted %.loc10_34.1, %.loc10_34.3
 // CHECK:STDOUT:   %.loc10_34.5: ref %NonAggregate = temporary %.loc10_34.2, %.loc10_34.4
 // CHECK:STDOUT:   %.loc10_34.6: %NonAggregate = acquire_value %.loc10_34.5
diff --git a/toolchain/check/testdata/interop/cpp/macros.carbon b/toolchain/check/testdata/interop/cpp/macros.carbon
index 2b26a7109577..e18dbe77d4b0 100644
--- a/toolchain/check/testdata/interop/cpp/macros.carbon
+++ b/toolchain/check/testdata/interop/cpp/macros.carbon
@@ -1045,7 +1045,7 @@ fn F() {
 // CHECK:STDOUT:   %.loc10_35.2: init %f32.97e = converted %float, %Core.FloatLiteral.as.ImplicitAs.impl.Convert.call [concrete = constants.%float.e3b]
 // CHECK:STDOUT:   %int_0: Core.IntLiteral = int_value 0 [concrete = constants.%int_0]
 // CHECK:STDOUT:   %.loc10_35.3: ref %f32.97e = array_index %a.var, %int_0
-// CHECK:STDOUT:   %.loc10_35.4: init %f32.97e to %.loc10_35.3 = initialize_from %.loc10_35.2 [concrete = constants.%float.e3b]
+// CHECK:STDOUT:   %.loc10_35.4: init %f32.97e to %.loc10_35.3 = in_place_init %.loc10_35.2 [concrete = constants.%float.e3b]
 // CHECK:STDOUT:   %.loc10_35.5: init %array_type to %a.var = array_init (%.loc10_35.4) [concrete = constants.%array]
 // CHECK:STDOUT:   %.loc10_3: init %array_type = converted %.loc10_35.1, %.loc10_35.5 [concrete = constants.%array]
 // CHECK:STDOUT:   assign %a.var, %.loc10_3
diff --git a/toolchain/check/testdata/interop/cpp/namespace.carbon b/toolchain/check/testdata/interop/cpp/namespace.carbon
index d41f0e669d7c..d93aad822743 100644
--- a/toolchain/check/testdata/interop/cpp/namespace.carbon
+++ b/toolchain/check/testdata/interop/cpp/namespace.carbon
@@ -396,7 +396,7 @@ fn Use(y: Cpp.Y) -> i32 {
 // CHECK:STDOUT:   %.loc8_11.1: ref %X = temporary_storage
 // CHECK:STDOUT:   %addr: %ptr.13d = addr_of %.loc8_11.1
 // CHECK:STDOUT:   %foo__carbon_thunk.call: init %empty_tuple.type = call imports.%foo__carbon_thunk.decl(%addr)
-// CHECK:STDOUT:   %.loc8_11.2: init %X to %.loc8_11.1 = in_place_init %foo__carbon_thunk.call
+// CHECK:STDOUT:   %.loc8_11.2: init %X to %.loc8_11.1 = mark_in_place_init %foo__carbon_thunk.call
 // CHECK:STDOUT:   %.loc8_11.3: ref %X = temporary %.loc8_11.1, %.loc8_11.2
 // CHECK:STDOUT:   %X.cpp_destructor.bound: <bound method> = bound_method %.loc8_11.3, constants.%X.cpp_destructor
 // CHECK:STDOUT:   %X.cpp_destructor.call: init %empty_tuple.type = call %X.cpp_destructor.bound(%.loc8_11.3)
diff --git a/toolchain/check/testdata/interop/cpp/stdlib/initializer_list.carbon b/toolchain/check/testdata/interop/cpp/stdlib/initializer_list.carbon
index 694422385f43..3351f33754eb 100644
--- a/toolchain/check/testdata/interop/cpp/stdlib/initializer_list.carbon
+++ b/toolchain/check/testdata/interop/cpp/stdlib/initializer_list.carbon
@@ -206,7 +206,7 @@ fn F() {
 // CHECK:STDOUT:   %.loc8_50.4: ref %array_type = temporary_storage
 // CHECK:STDOUT:   %int_0.loc8: Core.IntLiteral = int_value 0 [concrete = constants.%int_0]
 // CHECK:STDOUT:   %.loc8_50.5: ref %i32 = array_index %.loc8_50.4, %int_0.loc8
-// CHECK:STDOUT:   %.loc8_50.6: init %i32 to %.loc8_50.5 = initialize_from %.loc8_50.3 [concrete = constants.%int_1.5d2]
+// CHECK:STDOUT:   %.loc8_50.6: init %i32 to %.loc8_50.5 = in_place_init %.loc8_50.3 [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %impl.elem0.loc8_50.2: %.863 = impl_witness_access constants.%ImplicitAs.impl_witness.6bc, element0 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.0b5]
 // CHECK:STDOUT:   %bound_method.loc8_50.3: <bound method> = bound_method %int_2.loc8_46, %impl.elem0.loc8_50.2 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.bound.4e5]
 // CHECK:STDOUT:   %specific_fn.loc8_50.2: <specific function> = specific_function %impl.elem0.loc8_50.2, @Core.IntLiteral.as.ImplicitAs.impl.Convert(constants.%int_32) [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.specific_fn]
@@ -215,7 +215,7 @@ fn F() {
 // CHECK:STDOUT:   %.loc8_50.7: init %i32 = converted %int_2.loc8_46, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc8_50.2 [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %int_1.loc8_50: Core.IntLiteral = int_value 1 [concrete = constants.%int_1.5b8]
 // CHECK:STDOUT:   %.loc8_50.8: ref %i32 = array_index %.loc8_50.4, %int_1.loc8_50
-// CHECK:STDOUT:   %.loc8_50.9: init %i32 to %.loc8_50.8 = initialize_from %.loc8_50.7 [concrete = constants.%int_2.ef8]
+// CHECK:STDOUT:   %.loc8_50.9: init %i32 to %.loc8_50.8 = in_place_init %.loc8_50.7 [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %impl.elem0.loc8_50.3: %.863 = impl_witness_access constants.%ImplicitAs.impl_witness.6bc, element0 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.0b5]
 // CHECK:STDOUT:   %bound_method.loc8_50.5: <bound method> = bound_method %int_3.loc8_49, %impl.elem0.loc8_50.3 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.bound.061]
 // CHECK:STDOUT:   %specific_fn.loc8_50.3: <specific function> = specific_function %impl.elem0.loc8_50.3, @Core.IntLiteral.as.ImplicitAs.impl.Convert(constants.%int_32) [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.specific_fn]
@@ -224,7 +224,7 @@ fn F() {
 // CHECK:STDOUT:   %.loc8_50.10: init %i32 = converted %int_3.loc8_49, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc8_50.3 [concrete = constants.%int_3.822]
 // CHECK:STDOUT:   %int_2.loc8_50: Core.IntLiteral = int_value 2 [concrete = constants.%int_2.ecc]
 // CHECK:STDOUT:   %.loc8_50.11: ref %i32 = array_index %.loc8_50.4, %int_2.loc8_50
-// CHECK:STDOUT:   %.loc8_50.12: init %i32 to %.loc8_50.11 = initialize_from %.loc8_50.10 [concrete = constants.%int_3.822]
+// CHECK:STDOUT:   %.loc8_50.12: init %i32 to %.loc8_50.11 = in_place_init %.loc8_50.10 [concrete = constants.%int_3.822]
 // CHECK:STDOUT:   %.loc8_50.13: init %array_type to %.loc8_50.4 = array_init (%.loc8_50.6, %.loc8_50.9, %.loc8_50.12) [concrete = constants.%array]
 // CHECK:STDOUT:   %.loc8_50.14: init %array_type = converted %.loc8_50.1, %.loc8_50.13 [concrete = constants.%array]
 // CHECK:STDOUT:   %.loc8_50.15: ref %array_type = temporary %.loc8_50.4, %.loc8_50.14
@@ -253,7 +253,7 @@ fn F() {
 // CHECK:STDOUT:   %.loc10_23.4: ref %array_type = temporary_storage
 // CHECK:STDOUT:   %int_0.loc10: Core.IntLiteral = int_value 0 [concrete = constants.%int_0]
 // CHECK:STDOUT:   %.loc10_23.5: ref %i32 = array_index %.loc10_23.4, %int_0.loc10
-// CHECK:STDOUT:   %.loc10_23.6: init %i32 to %.loc10_23.5 = initialize_from %.loc10_23.3 [concrete = constants.%int_1.5d2]
+// CHECK:STDOUT:   %.loc10_23.6: init %i32 to %.loc10_23.5 = in_place_init %.loc10_23.3 [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %impl.elem0.loc10_23.2: %.863 = impl_witness_access constants.%ImplicitAs.impl_witness.6bc, element0 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.0b5]
 // CHECK:STDOUT:   %bound_method.loc10_23.3: <bound method> = bound_method %int_2.loc10_19, %impl.elem0.loc10_23.2 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.bound.4e5]
 // CHECK:STDOUT:   %specific_fn.loc10_23.2: <specific function> = specific_function %impl.elem0.loc10_23.2, @Core.IntLiteral.as.ImplicitAs.impl.Convert(constants.%int_32) [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.specific_fn]
@@ -262,7 +262,7 @@ fn F() {
 // CHECK:STDOUT:   %.loc10_23.7: init %i32 = converted %int_2.loc10_19, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc10_23.2 [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %int_1.loc10_23: Core.IntLiteral = int_value 1 [concrete = constants.%int_1.5b8]
 // CHECK:STDOUT:   %.loc10_23.8: ref %i32 = array_index %.loc10_23.4, %int_1.loc10_23
-// CHECK:STDOUT:   %.loc10_23.9: init %i32 to %.loc10_23.8 = initialize_from %.loc10_23.7 [concrete = constants.%int_2.ef8]
+// CHECK:STDOUT:   %.loc10_23.9: init %i32 to %.loc10_23.8 = in_place_init %.loc10_23.7 [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %impl.elem0.loc10_23.3: %.863 = impl_witness_access constants.%ImplicitAs.impl_witness.6bc, element0 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.0b5]
 // CHECK:STDOUT:   %bound_method.loc10_23.5: <bound method> = bound_method %int_3.loc10_22, %impl.elem0.loc10_23.3 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.bound.061]
 // CHECK:STDOUT:   %specific_fn.loc10_23.3: <specific function> = specific_function %impl.elem0.loc10_23.3, @Core.IntLiteral.as.ImplicitAs.impl.Convert(constants.%int_32) [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.specific_fn]
@@ -271,7 +271,7 @@ fn F() {
 // CHECK:STDOUT:   %.loc10_23.10: init %i32 = converted %int_3.loc10_22, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc10_23.3 [concrete = constants.%int_3.822]
 // CHECK:STDOUT:   %int_2.loc10_23: Core.IntLiteral = int_value 2 [concrete = constants.%int_2.ecc]
 // CHECK:STDOUT:   %.loc10_23.11: ref %i32 = array_index %.loc10_23.4, %int_2.loc10_23
-// CHECK:STDOUT:   %.loc10_23.12: init %i32 to %.loc10_23.11 = initialize_from %.loc10_23.10 [concrete = constants.%int_3.822]
+// CHECK:STDOUT:   %.loc10_23.12: init %i32 to %.loc10_23.11 = in_place_init %.loc10_23.10 [concrete = constants.%int_3.822]
 // CHECK:STDOUT:   %.loc10_23.13: init %array_type to %.loc10_23.4 = array_init (%.loc10_23.6, %.loc10_23.9, %.loc10_23.12) [concrete = constants.%array]
 // CHECK:STDOUT:   %.loc10_23.14: init %array_type = converted %.loc10_23.1, %.loc10_23.13 [concrete = constants.%array]
 // CHECK:STDOUT:   %.loc10_23.15: ref %array_type = temporary %.loc10_23.4, %.loc10_23.14
@@ -308,7 +308,7 @@ fn F() {
 // CHECK:STDOUT:   %.loc12_44.5: ref %array_type = temporary_storage
 // CHECK:STDOUT:   %int_0.loc12: Core.IntLiteral = int_value 0 [concrete = constants.%int_0]
 // CHECK:STDOUT:   %.loc12_44.6: ref %i32 = array_index %.loc12_44.5, %int_0.loc12
-// CHECK:STDOUT:   %.loc12_44.7: init %i32 to %.loc12_44.6 = initialize_from %.loc12_44.4 [concrete = constants.%int_1.5d2]
+// CHECK:STDOUT:   %.loc12_44.7: init %i32 to %.loc12_44.6 = in_place_init %.loc12_44.4 [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %impl.elem0.loc12_44.2: %.863 = impl_witness_access constants.%ImplicitAs.impl_witness.6bc, element0 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.0b5]
 // CHECK:STDOUT:   %bound_method.loc12_44.3: <bound method> = bound_method %int_2.loc12_40, %impl.elem0.loc12_44.2 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.bound.4e5]
 // CHECK:STDOUT:   %specific_fn.loc12_44.2: <specific function> = specific_function %impl.elem0.loc12_44.2, @Core.IntLiteral.as.ImplicitAs.impl.Convert(constants.%int_32) [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.specific_fn]
@@ -317,7 +317,7 @@ fn F() {
 // CHECK:STDOUT:   %.loc12_44.8: init %i32 = converted %int_2.loc12_40, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc12_44.2 [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %int_1.loc12_44: Core.IntLiteral = int_value 1 [concrete = constants.%int_1.5b8]
 // CHECK:STDOUT:   %.loc12_44.9: ref %i32 = array_index %.loc12_44.5, %int_1.loc12_44
-// CHECK:STDOUT:   %.loc12_44.10: init %i32 to %.loc12_44.9 = initialize_from %.loc12_44.8 [concrete = constants.%int_2.ef8]
+// CHECK:STDOUT:   %.loc12_44.10: init %i32 to %.loc12_44.9 = in_place_init %.loc12_44.8 [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %impl.elem0.loc12_44.3: %.863 = impl_witness_access constants.%ImplicitAs.impl_witness.6bc, element0 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.0b5]
 // CHECK:STDOUT:   %bound_method.loc12_44.5: <bound method> = bound_method %int_3.loc12_43, %impl.elem0.loc12_44.3 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.bound.061]
 // CHECK:STDOUT:   %specific_fn.loc12_44.3: <specific function> = specific_function %impl.elem0.loc12_44.3, @Core.IntLiteral.as.ImplicitAs.impl.Convert(constants.%int_32) [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.specific_fn]
@@ -326,7 +326,7 @@ fn F() {
 // CHECK:STDOUT:   %.loc12_44.11: init %i32 = converted %int_3.loc12_43, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc12_44.3 [concrete = constants.%int_3.822]
 // CHECK:STDOUT:   %int_2.loc12_44: Core.IntLiteral = int_value 2 [concrete = constants.%int_2.ecc]
 // CHECK:STDOUT:   %.loc12_44.12: ref %i32 = array_index %.loc12_44.5, %int_2.loc12_44
-// CHECK:STDOUT:   %.loc12_44.13: init %i32 to %.loc12_44.12 = initialize_from %.loc12_44.11 [concrete = constants.%int_3.822]
+// CHECK:STDOUT:   %.loc12_44.13: init %i32 to %.loc12_44.12 = in_place_init %.loc12_44.11 [concrete = constants.%int_3.822]
 // CHECK:STDOUT:   %.loc12_44.14: init %array_type to %.loc12_44.5 = array_init (%.loc12_44.7, %.loc12_44.10, %.loc12_44.13) [concrete = constants.%array]
 // CHECK:STDOUT:   %.loc12_44.15: init %array_type = converted %.loc12_44.1, %.loc12_44.14 [concrete = constants.%array]
 // CHECK:STDOUT:   %.loc12_44.16: ref %array_type = temporary %.loc12_44.5, %.loc12_44.15
@@ -339,7 +339,7 @@ fn F() {
 // CHECK:STDOUT:   %addr.loc12_44.1: %ptr.82f = addr_of %.loc12_44.21
 // CHECK:STDOUT:   %addr.loc12_44.2: %ptr.79d = addr_of %.loc12_44.2
 // CHECK:STDOUT:   %InitListConstructor__carbon_thunk.call: init %empty_tuple.type = call imports.%InitListConstructor__carbon_thunk.decl(%addr.loc12_44.1, %addr.loc12_44.2)
-// CHECK:STDOUT:   %.loc12_44.22: init %InitListConstructor to %.loc12_44.2 = in_place_init %InitListConstructor__carbon_thunk.call
+// CHECK:STDOUT:   %.loc12_44.22: init %InitListConstructor to %.loc12_44.2 = mark_in_place_init %InitListConstructor__carbon_thunk.call
 // CHECK:STDOUT:   %.loc12_44.23: init %InitListConstructor = converted %.loc12_44.1, %.loc12_44.22
 // CHECK:STDOUT:   %.loc12_44.24: ref %InitListConstructor = temporary %.loc12_44.2, %.loc12_44.23
 // CHECK:STDOUT:   %.loc12_44.25: %InitListConstructor = acquire_value %.loc12_44.24
diff --git a/toolchain/check/testdata/interop/cpp/stdlib/string_view.carbon b/toolchain/check/testdata/interop/cpp/stdlib/string_view.carbon
index d43c14faeb89..d6513da96191 100644
--- a/toolchain/check/testdata/interop/cpp/stdlib/string_view.carbon
+++ b/toolchain/check/testdata/interop/cpp/stdlib/string_view.carbon
@@ -154,7 +154,7 @@ fn StarstWith(a: str, b: str) -> bool {
 // CHECK:STDOUT:   %.loc13_11.1: ref %str.ee0 = splice_block %return.param {}
 // CHECK:STDOUT:   %addr: %ptr.85f = addr_of %.loc13_11.1
 // CHECK:STDOUT:   %Produce__carbon_thunk.call: init %empty_tuple.type = call imports.%Produce__carbon_thunk.decl(%addr)
-// CHECK:STDOUT:   %.loc14: init %str.ee0 to %.loc13_11.1 = in_place_init %Produce__carbon_thunk.call
+// CHECK:STDOUT:   %.loc14: init %str.ee0 to %.loc13_11.1 = mark_in_place_init %Produce__carbon_thunk.call
 // CHECK:STDOUT:   return %.loc14 to %return.param
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
@@ -228,7 +228,7 @@ fn StarstWith(a: str, b: str) -> bool {
 // CHECK:STDOUT:   %.loc8_53.1: ref bool = temporary_storage
 // CHECK:STDOUT:   %addr.loc8_53.2: %ptr.bb2 = addr_of %.loc8_53.1
 // CHECK:STDOUT:   %starts_with__carbon_thunk.call: init %empty_tuple.type = call imports.%starts_with__carbon_thunk.decl(%a.ref, %addr.loc8_53.1, %addr.loc8_53.2)
-// CHECK:STDOUT:   %.loc8_53.2: init bool = in_place_init %starts_with__carbon_thunk.call, %.loc8_53.1
+// CHECK:STDOUT:   %.loc8_53.2: init bool to %.loc8_53.1 = mark_in_place_init %starts_with__carbon_thunk.call
 // CHECK:STDOUT:   return %.loc8_53.2
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
diff --git a/toolchain/check/testdata/interop/cpp/template/alias_template.carbon b/toolchain/check/testdata/interop/cpp/template/alias_template.carbon
index aa529fb750a8..d1aaeaa61e68 100644
--- a/toolchain/check/testdata/interop/cpp/template/alias_template.carbon
+++ b/toolchain/check/testdata/interop/cpp/template/alias_template.carbon
@@ -116,7 +116,7 @@ var a2: Cpp.Second(Cpp.B, Cpp.A) = Cpp.A.A();
 // CHECK:STDOUT:   %.loc7_1: ref %A = splice_block file.%a1.var [concrete = file.%a1.var] {}
 // CHECK:STDOUT:   %addr.loc7: %ptr.270 = addr_of %.loc7_1
 // CHECK:STDOUT:   %A__carbon_thunk.call.loc7: init %empty_tuple.type = call imports.%A__carbon_thunk.decl(%addr.loc7)
-// CHECK:STDOUT:   %.loc7_43: init %A to %.loc7_1 = in_place_init %A__carbon_thunk.call.loc7
+// CHECK:STDOUT:   %.loc7_43: init %A to %.loc7_1 = mark_in_place_init %A__carbon_thunk.call.loc7
 // CHECK:STDOUT:   assign file.%a1.var, %.loc7_43
 // CHECK:STDOUT:   %Cpp.ref.loc8: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
 // CHECK:STDOUT:   %B.ref.loc8_38: type = name_ref B, imports.%B.decl [concrete = constants.%B]
@@ -124,7 +124,7 @@ var a2: Cpp.Second(Cpp.B, Cpp.A) = Cpp.A.A();
 // CHECK:STDOUT:   %.loc8_1: ref %B = splice_block file.%b1.var [concrete = file.%b1.var] {}
 // CHECK:STDOUT:   %addr.loc8: %ptr.a04 = addr_of %.loc8_1
 // CHECK:STDOUT:   %B__carbon_thunk.call.loc8: init %empty_tuple.type = call imports.%B__carbon_thunk.decl(%addr.loc8)
-// CHECK:STDOUT:   %.loc8_43: init %B to %.loc8_1 = in_place_init %B__carbon_thunk.call.loc8
+// CHECK:STDOUT:   %.loc8_43: init %B to %.loc8_1 = mark_in_place_init %B__carbon_thunk.call.loc8
 // CHECK:STDOUT:   assign file.%b1.var, %.loc8_43
 // CHECK:STDOUT:   %Cpp.ref.loc9: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
 // CHECK:STDOUT:   %B.ref.loc9_39: type = name_ref B, imports.%B.decl [concrete = constants.%B]
@@ -132,7 +132,7 @@ var a2: Cpp.Second(Cpp.B, Cpp.A) = Cpp.A.A();
 // CHECK:STDOUT:   %.loc9_1: ref %B = splice_block file.%b2.var [concrete = file.%b2.var] {}
 // CHECK:STDOUT:   %addr.loc9: %ptr.a04 = addr_of %.loc9_1
 // CHECK:STDOUT:   %B__carbon_thunk.call.loc9: init %empty_tuple.type = call imports.%B__carbon_thunk.decl(%addr.loc9)
-// CHECK:STDOUT:   %.loc9_44: init %B to %.loc9_1 = in_place_init %B__carbon_thunk.call.loc9
+// CHECK:STDOUT:   %.loc9_44: init %B to %.loc9_1 = mark_in_place_init %B__carbon_thunk.call.loc9
 // CHECK:STDOUT:   assign file.%b2.var, %.loc9_44
 // CHECK:STDOUT:   %Cpp.ref.loc10: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
 // CHECK:STDOUT:   %A.ref.loc10_39: type = name_ref A, imports.%A.decl [concrete = constants.%A]
@@ -140,7 +140,7 @@ var a2: Cpp.Second(Cpp.B, Cpp.A) = Cpp.A.A();
 // CHECK:STDOUT:   %.loc10_1: ref %A = splice_block file.%a2.var [concrete = file.%a2.var] {}
 // CHECK:STDOUT:   %addr.loc10: %ptr.270 = addr_of %.loc10_1
 // CHECK:STDOUT:   %A__carbon_thunk.call.loc10: init %empty_tuple.type = call imports.%A__carbon_thunk.decl(%addr.loc10)
-// CHECK:STDOUT:   %.loc10_44: init %A to %.loc10_1 = in_place_init %A__carbon_thunk.call.loc10
+// CHECK:STDOUT:   %.loc10_44: init %A to %.loc10_1 = mark_in_place_init %A__carbon_thunk.call.loc10
 // CHECK:STDOUT:   assign file.%a2.var, %.loc10_44
 // CHECK:STDOUT:   <elided>
 // CHECK:STDOUT: }
diff --git a/toolchain/check/testdata/interop/cpp/template/class_template.carbon b/toolchain/check/testdata/interop/cpp/template/class_template.carbon
index b907c4b87177..7edfd967409a 100644
--- a/toolchain/check/testdata/interop/cpp/template/class_template.carbon
+++ b/toolchain/check/testdata/interop/cpp/template/class_template.carbon
@@ -103,7 +103,7 @@ var a: Cpp.A = Cpp.X(Cpp.A, Cpp.B).f({} as Cpp.B);
 // CHECK:STDOUT:   %addr.loc7_49.1: %ptr.a04 = addr_of %.loc7_41.3
 // CHECK:STDOUT:   %addr.loc7_49.2: %ptr.270 = addr_of %.loc7_1
 // CHECK:STDOUT:   %f__carbon_thunk.call: init %empty_tuple.type = call imports.%f__carbon_thunk.decl(%addr.loc7_49.1, %addr.loc7_49.2)
-// CHECK:STDOUT:   %.loc7_49: init %A to %.loc7_1 = in_place_init %f__carbon_thunk.call
+// CHECK:STDOUT:   %.loc7_49: init %A to %.loc7_1 = mark_in_place_init %f__carbon_thunk.call
 // CHECK:STDOUT:   assign file.%a.var, %.loc7_49
 // CHECK:STDOUT:   <elided>
 // CHECK:STDOUT: }
diff --git a/toolchain/check/testdata/operators/builtin/assignment.carbon b/toolchain/check/testdata/operators/builtin/assignment.carbon
index 4f3460511bcc..6f8acb2a8176 100644
--- a/toolchain/check/testdata/operators/builtin/assignment.carbon
+++ b/toolchain/check/testdata/operators/builtin/assignment.carbon
@@ -196,7 +196,7 @@ fn Main() {
 // CHECK:STDOUT:   %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc19_28.1: init %i32 = call %bound_method.loc19_28.2(%int_1.loc19) [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %.loc19_28.2: init %i32 = converted %int_1.loc19, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc19_28.1 [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %tuple.elem0.loc19: ref %i32 = tuple_access %b.var, element0
-// CHECK:STDOUT:   %.loc19_28.3: init %i32 to %tuple.elem0.loc19 = initialize_from %.loc19_28.2 [concrete = constants.%int_1.5d2]
+// CHECK:STDOUT:   %.loc19_28.3: init %i32 to %tuple.elem0.loc19 = in_place_init %.loc19_28.2 [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %impl.elem0.loc19_28.2: %.863 = impl_witness_access constants.%ImplicitAs.impl_witness.6bc, element0 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.0b5]
 // CHECK:STDOUT:   %bound_method.loc19_28.3: <bound method> = bound_method %int_2.loc19, %impl.elem0.loc19_28.2 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.bound.4e5]
 // CHECK:STDOUT:   %specific_fn.loc19_28.2: <specific function> = specific_function %impl.elem0.loc19_28.2, @Core.IntLiteral.as.ImplicitAs.impl.Convert(constants.%int_32) [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.specific_fn]
@@ -204,7 +204,7 @@ fn Main() {
 // CHECK:STDOUT:   %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc19_28.2: init %i32 = call %bound_method.loc19_28.4(%int_2.loc19) [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %.loc19_28.4: init %i32 = converted %int_2.loc19, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc19_28.2 [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %tuple.elem1.loc19: ref %i32 = tuple_access %b.var, element1
-// CHECK:STDOUT:   %.loc19_28.5: init %i32 to %tuple.elem1.loc19 = initialize_from %.loc19_28.4 [concrete = constants.%int_2.ef8]
+// CHECK:STDOUT:   %.loc19_28.5: init %i32 to %tuple.elem1.loc19 = in_place_init %.loc19_28.4 [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %.loc19_28.6: init %tuple.type.d07 to %b.var = tuple_init (%.loc19_28.3, %.loc19_28.5) [concrete = constants.%tuple.21c]
 // CHECK:STDOUT:   %.loc19_3: init %tuple.type.d07 = converted %.loc19_28.1, %.loc19_28.6 [concrete = constants.%tuple.21c]
 // CHECK:STDOUT:   assign %b.var, %.loc19_3
@@ -254,7 +254,7 @@ fn Main() {
 // CHECK:STDOUT:   %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc23_46.1: init %i32 = call %bound_method.loc23_46.2(%int_1.loc23) [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %.loc23_46.2: init %i32 = converted %int_1.loc23, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc23_46.1 [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %.loc23_46.3: ref %i32 = struct_access %c.var, element0
-// CHECK:STDOUT:   %.loc23_46.4: init %i32 to %.loc23_46.3 = initialize_from %.loc23_46.2 [concrete = constants.%int_1.5d2]
+// CHECK:STDOUT:   %.loc23_46.4: init %i32 to %.loc23_46.3 = in_place_init %.loc23_46.2 [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %impl.elem0.loc23_46.2: %.863 = impl_witness_access constants.%ImplicitAs.impl_witness.6bc, element0 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.0b5]
 // CHECK:STDOUT:   %bound_method.loc23_46.3: <bound method> = bound_method %int_2.loc23, %impl.elem0.loc23_46.2 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.bound.4e5]
 // CHECK:STDOUT:   %specific_fn.loc23_46.2: <specific function> = specific_function %impl.elem0.loc23_46.2, @Core.IntLiteral.as.ImplicitAs.impl.Convert(constants.%int_32) [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.specific_fn]
@@ -262,7 +262,7 @@ fn Main() {
 // CHECK:STDOUT:   %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc23_46.2: init %i32 = call %bound_method.loc23_46.4(%int_2.loc23) [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %.loc23_46.5: init %i32 = converted %int_2.loc23, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc23_46.2 [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %.loc23_46.6: ref %i32 = struct_access %c.var, element1
-// CHECK:STDOUT:   %.loc23_46.7: init %i32 to %.loc23_46.6 = initialize_from %.loc23_46.5 [concrete = constants.%int_2.ef8]
+// CHECK:STDOUT:   %.loc23_46.7: init %i32 to %.loc23_46.6 = in_place_init %.loc23_46.5 [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %.loc23_46.8: init %struct_type.a.b.501 to %c.var = struct_init (%.loc23_46.4, %.loc23_46.7) [concrete = constants.%struct.ed5]
 // CHECK:STDOUT:   %.loc23_3: init %struct_type.a.b.501 = converted %.loc23_46.1, %.loc23_46.8 [concrete = constants.%struct.ed5]
 // CHECK:STDOUT:   assign %c.var, %.loc23_3
diff --git a/toolchain/check/testdata/operators/builtin/fail_assignment_to_non_assignable.carbon b/toolchain/check/testdata/operators/builtin/fail_assignment_to_non_assignable.carbon
index 774f483fb292..a30f6b881859 100644
--- a/toolchain/check/testdata/operators/builtin/fail_assignment_to_non_assignable.carbon
+++ b/toolchain/check/testdata/operators/builtin/fail_assignment_to_non_assignable.carbon
@@ -211,12 +211,12 @@ fn Main() {
 // CHECK:STDOUT:   %bound_method.loc32_13: <bound method> = bound_method %int_3.loc32, %impl.elem0.loc32_13 [concrete = constants.%Core.IntLiteral.as.Copy.impl.Op.bound.04c]
 // CHECK:STDOUT:   %Core.IntLiteral.as.Copy.impl.Op.call.loc32_13: init Core.IntLiteral = call %bound_method.loc32_13(%int_3.loc32) [concrete = constants.%int_3.1ba]
 // CHECK:STDOUT:   %tuple.elem0.loc32: Core.IntLiteral = tuple_access %.loc32_8.1, element0 [concrete = constants.%int_1.5b8]
-// CHECK:STDOUT:   %.loc32_17.2: init Core.IntLiteral to %tuple.elem0.loc32 = initialize_from %Core.IntLiteral.as.Copy.impl.Op.call.loc32_13 [concrete = constants.%int_3.1ba]
+// CHECK:STDOUT:   %.loc32_17.2: init Core.IntLiteral to %tuple.elem0.loc32 = in_place_init %Core.IntLiteral.as.Copy.impl.Op.call.loc32_13 [concrete = constants.%int_3.1ba]
 // CHECK:STDOUT:   %impl.elem0.loc32_16: %.6b5 = impl_witness_access constants.%Copy.impl_witness.98e, element0 [concrete = constants.%Core.IntLiteral.as.Copy.impl.Op]
 // CHECK:STDOUT:   %bound_method.loc32_16: <bound method> = bound_method %int_4.loc32, %impl.elem0.loc32_16 [concrete = constants.%Core.IntLiteral.as.Copy.impl.Op.bound.e8e]
 // CHECK:STDOUT:   %Core.IntLiteral.as.Copy.impl.Op.call.loc32_16: init Core.IntLiteral = call %bound_method.loc32_16(%int_4.loc32) [concrete = constants.%int_4]
 // CHECK:STDOUT:   %tuple.elem1.loc32: Core.IntLiteral = tuple_access %.loc32_8.1, element1 [concrete = constants.%int_2.ecc]
-// CHECK:STDOUT:   %.loc32_17.3: init Core.IntLiteral to %tuple.elem1.loc32 = initialize_from %Core.IntLiteral.as.Copy.impl.Op.call.loc32_16 [concrete = constants.%int_4]
+// CHECK:STDOUT:   %.loc32_17.3: init Core.IntLiteral to %tuple.elem1.loc32 = in_place_init %Core.IntLiteral.as.Copy.impl.Op.call.loc32_16 [concrete = constants.%int_4]
 // CHECK:STDOUT:   %.loc32_17.4: init %tuple.type.f94 to %.loc32_8.1 = tuple_init (%.loc32_17.2, %.loc32_17.3) [concrete = constants.%tuple.302]
 // CHECK:STDOUT:   %.loc32_10: init %tuple.type.f94 = converted %.loc32_17.1, %.loc32_17.4 [concrete = constants.%tuple.302]
 // CHECK:STDOUT:   assign %.loc32_8.1, %.loc32_10
@@ -253,7 +253,7 @@ fn Main() {
 // CHECK:STDOUT:   %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc38_17.1: init %i32 = call %bound_method.loc38_17.2(%int_1.loc38) [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %.loc38_17.2: init %i32 = converted %int_1.loc38, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc38_17.1 [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %tuple.elem0.loc38: %i32 = tuple_access %.loc38_8.1, element0
-// CHECK:STDOUT:   %.loc38_17.3: init %i32 to %tuple.elem0.loc38 = initialize_from %.loc38_17.2 [concrete = constants.%int_1.5d2]
+// CHECK:STDOUT:   %.loc38_17.3: init %i32 to %tuple.elem0.loc38 = in_place_init %.loc38_17.2 [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %impl.elem0.loc38_17.2: %.863 = impl_witness_access constants.%ImplicitAs.impl_witness.6bc, element0 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.0b5]
 // CHECK:STDOUT:   %bound_method.loc38_17.3: <bound method> = bound_method %int_2.loc38, %impl.elem0.loc38_17.2 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.bound.4e5]
 // CHECK:STDOUT:   %specific_fn.loc38_17.2: <specific function> = specific_function %impl.elem0.loc38_17.2, @Core.IntLiteral.as.ImplicitAs.impl.Convert(constants.%int_32) [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.specific_fn]
@@ -261,7 +261,7 @@ fn Main() {
 // CHECK:STDOUT:   %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc38_17.2: init %i32 = call %bound_method.loc38_17.4(%int_2.loc38) [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %.loc38_17.4: init %i32 = converted %int_2.loc38, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc38_17.2 [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %tuple.elem1.loc38: %i32 = tuple_access %.loc38_8.1, element1
-// CHECK:STDOUT:   %.loc38_17.5: init %i32 to %tuple.elem1.loc38 = initialize_from %.loc38_17.4 [concrete = constants.%int_2.ef8]
+// CHECK:STDOUT:   %.loc38_17.5: init %i32 to %tuple.elem1.loc38 = in_place_init %.loc38_17.4 [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %.loc38_17.6: init %tuple.type.d07 to %.loc38_8.1 = tuple_init (%.loc38_17.3, %.loc38_17.5) [concrete = constants.%tuple.21c]
 // CHECK:STDOUT:   %.loc38_10: init %tuple.type.d07 = converted %.loc38_17.1, %.loc38_17.6 [concrete = constants.%tuple.21c]
 // CHECK:STDOUT:   assign %.loc38_8.1, %.loc38_10
@@ -288,12 +288,12 @@ fn Main() {
 // CHECK:STDOUT:   %bound_method.loc48_28: <bound method> = bound_method %int_3.loc48, %impl.elem0.loc48_28 [concrete = constants.%Core.IntLiteral.as.Copy.impl.Op.bound.04c]
 // CHECK:STDOUT:   %Core.IntLiteral.as.Copy.impl.Op.call.loc48_28: init Core.IntLiteral = call %bound_method.loc48_28(%int_3.loc48) [concrete = constants.%int_3.1ba]
 // CHECK:STDOUT:   %.loc48_37.2: Core.IntLiteral = struct_access %.loc48_18.1, element0 [concrete = constants.%int_1.5b8]
-// CHECK:STDOUT:   %.loc48_37.3: init Core.IntLiteral to %.loc48_37.2 = initialize_from %Core.IntLiteral.as.Copy.impl.Op.call.loc48_28 [concrete = constants.%int_3.1ba]
+// CHECK:STDOUT:   %.loc48_37.3: init Core.IntLiteral to %.loc48_37.2 = in_place_init %Core.IntLiteral.as.Copy.impl.Op.call.loc48_28 [concrete = constants.%int_3.1ba]
 // CHECK:STDOUT:   %impl.elem0.loc48_36: %.6b5 = impl_witness_access constants.%Copy.impl_witness.98e, element0 [concrete = constants.%Core.IntLiteral.as.Copy.impl.Op]
 // CHECK:STDOUT:   %bound_method.loc48_36: <bound method> = bound_method %int_4.loc48, %impl.elem0.loc48_36 [concrete = constants.%Core.IntLiteral.as.Copy.impl.Op.bound.e8e]
 // CHECK:STDOUT:   %Core.IntLiteral.as.Copy.impl.Op.call.loc48_36: init Core.IntLiteral = call %bound_method.loc48_36(%int_4.loc48) [concrete = constants.%int_4]
 // CHECK:STDOUT:   %.loc48_37.4: Core.IntLiteral = struct_access %.loc48_18.1, element1 [concrete = constants.%int_2.ecc]
-// CHECK:STDOUT:   %.loc48_37.5: init Core.IntLiteral to %.loc48_37.4 = initialize_from %Core.IntLiteral.as.Copy.impl.Op.call.loc48_36 [concrete = constants.%int_4]
+// CHECK:STDOUT:   %.loc48_37.5: init Core.IntLiteral to %.loc48_37.4 = in_place_init %Core.IntLiteral.as.Copy.impl.Op.call.loc48_36 [concrete = constants.%int_4]
 // CHECK:STDOUT:   %.loc48_37.6: init %struct_type.x.y to %.loc48_18.1 = struct_init (%.loc48_37.3, %.loc48_37.5) [concrete = constants.%struct.a0d]
 // CHECK:STDOUT:   %.loc48_20: init %struct_type.x.y = converted %.loc48_37.1, %.loc48_37.6 [concrete = constants.%struct.a0d]
 // CHECK:STDOUT:   assign %.loc48_18.1, %.loc48_20
diff --git a/toolchain/check/testdata/operators/overloaded/implicit_as.carbon b/toolchain/check/testdata/operators/overloaded/implicit_as.carbon
index 3a2eeca14b87..eecfa88fc973 100644
--- a/toolchain/check/testdata/operators/overloaded/implicit_as.carbon
+++ b/toolchain/check/testdata/operators/overloaded/implicit_as.carbon
@@ -257,7 +257,7 @@ fn Test() {
 // CHECK:STDOUT:   %bound_method.loc20_47.2: <bound method> = bound_method %self.ref, %specific_fn
 // CHECK:STDOUT:   %Int.as.Copy.impl.Op.call: init %i32 = call %bound_method.loc20_47.2(%self.ref)
 // CHECK:STDOUT:   %.loc20_51.2: ref %i32 = class_element_access %return.param, element0
-// CHECK:STDOUT:   %.loc20_51.3: init %i32 to %.loc20_51.2 = initialize_from %Int.as.Copy.impl.Op.call
+// CHECK:STDOUT:   %.loc20_51.3: init %i32 to %.loc20_51.2 = in_place_init %Int.as.Copy.impl.Op.call
 // CHECK:STDOUT:   %.loc20_51.4: init %X to %return.param = class_init (%.loc20_51.3)
 // CHECK:STDOUT:   %.loc20_52: init %X = converted %.loc20_51.1, %.loc20_51.4
 // CHECK:STDOUT:   return %.loc20_52 to %return.param
diff --git a/toolchain/check/testdata/packages/cross_package_export.carbon b/toolchain/check/testdata/packages/cross_package_export.carbon
index ea10be68231f..eb0563981852 100644
--- a/toolchain/check/testdata/packages/cross_package_export.carbon
+++ b/toolchain/check/testdata/packages/cross_package_export.carbon
@@ -437,7 +437,7 @@ alias C = Other.C;
 // CHECK:STDOUT:   %.loc6_25.1: %empty_tuple.type = tuple_literal () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc6_26.1: %struct_type.x = struct_literal (%.loc6_25.1) [concrete = constants.%struct]
 // CHECK:STDOUT:   %.loc6_26.2: ref %empty_tuple.type = class_element_access file.%c.var, element0 [concrete = constants.%.dd7]
-// CHECK:STDOUT:   %.loc6_25.2: init %empty_tuple.type to %.loc6_26.2 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc6_25.2: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc6_26.3: init %empty_tuple.type = converted %.loc6_25.1, %.loc6_25.2 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc6_26.4: init %C to file.%c.var = class_init (%.loc6_26.3) [concrete = constants.%C.val]
 // CHECK:STDOUT:   %.loc6_1: init %C = converted %.loc6_26.1, %.loc6_26.4 [concrete = constants.%C.val]
@@ -503,7 +503,7 @@ alias C = Other.C;
 // CHECK:STDOUT:   %.loc7_25.1: %empty_tuple.type = tuple_literal () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc7_26.1: %struct_type.x = struct_literal (%.loc7_25.1) [concrete = constants.%struct]
 // CHECK:STDOUT:   %.loc7_26.2: ref %empty_tuple.type = class_element_access file.%c.var, element0 [concrete = constants.%.dd7]
-// CHECK:STDOUT:   %.loc7_25.2: init %empty_tuple.type to %.loc7_26.2 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc7_25.2: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc7_26.3: init %empty_tuple.type = converted %.loc7_25.1, %.loc7_25.2 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc7_26.4: init %C to file.%c.var = class_init (%.loc7_26.3) [concrete = constants.%C.val]
 // CHECK:STDOUT:   %.loc7_1: init %C = converted %.loc7_26.1, %.loc7_26.4 [concrete = constants.%C.val]
@@ -569,7 +569,7 @@ alias C = Other.C;
 // CHECK:STDOUT:   %.loc6_25.1: %empty_tuple.type = tuple_literal () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc6_26.1: %struct_type.x = struct_literal (%.loc6_25.1) [concrete = constants.%struct]
 // CHECK:STDOUT:   %.loc6_26.2: ref %empty_tuple.type = class_element_access file.%c.var, element0 [concrete = constants.%.dd7]
-// CHECK:STDOUT:   %.loc6_25.2: init %empty_tuple.type to %.loc6_26.2 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc6_25.2: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc6_26.3: init %empty_tuple.type = converted %.loc6_25.1, %.loc6_25.2 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc6_26.4: init %C to file.%c.var = class_init (%.loc6_26.3) [concrete = constants.%C.val]
 // CHECK:STDOUT:   %.loc6_1: init %C = converted %.loc6_26.1, %.loc6_26.4 [concrete = constants.%C.val]
@@ -633,7 +633,7 @@ alias C = Other.C;
 // CHECK:STDOUT:   %.loc6_25.1: %empty_tuple.type = tuple_literal () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc6_26.1: %struct_type.x = struct_literal (%.loc6_25.1) [concrete = constants.%struct]
 // CHECK:STDOUT:   %.loc6_26.2: ref %empty_tuple.type = class_element_access file.%c.var, element0 [concrete = constants.%.dd7]
-// CHECK:STDOUT:   %.loc6_25.2: init %empty_tuple.type to %.loc6_26.2 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc6_25.2: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc6_26.3: init %empty_tuple.type = converted %.loc6_25.1, %.loc6_25.2 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc6_26.4: init %C to file.%c.var = class_init (%.loc6_26.3) [concrete = constants.%C.val]
 // CHECK:STDOUT:   %.loc6_1: init %C = converted %.loc6_26.1, %.loc6_26.4 [concrete = constants.%C.val]
@@ -698,7 +698,7 @@ alias C = Other.C;
 // CHECK:STDOUT:   %.loc7_25.1: %empty_tuple.type = tuple_literal () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc7_26.1: %struct_type.x = struct_literal (%.loc7_25.1) [concrete = constants.%struct]
 // CHECK:STDOUT:   %.loc7_26.2: ref %empty_tuple.type = class_element_access file.%c.var, element0 [concrete = constants.%.dd7]
-// CHECK:STDOUT:   %.loc7_25.2: init %empty_tuple.type to %.loc7_26.2 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc7_25.2: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc7_26.3: init %empty_tuple.type = converted %.loc7_25.1, %.loc7_25.2 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc7_26.4: init %C to file.%c.var = class_init (%.loc7_26.3) [concrete = constants.%C.val]
 // CHECK:STDOUT:   %.loc7_1: init %C = converted %.loc7_26.1, %.loc7_26.4 [concrete = constants.%C.val]
@@ -762,7 +762,7 @@ alias C = Other.C;
 // CHECK:STDOUT:   %.loc6_25.1: %empty_tuple.type = tuple_literal () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc6_26.1: %struct_type.x = struct_literal (%.loc6_25.1) [concrete = constants.%struct]
 // CHECK:STDOUT:   %.loc6_26.2: ref %empty_tuple.type = class_element_access file.%c.var, element0 [concrete = constants.%.dd7]
-// CHECK:STDOUT:   %.loc6_25.2: init %empty_tuple.type to %.loc6_26.2 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc6_25.2: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc6_26.3: init %empty_tuple.type = converted %.loc6_25.1, %.loc6_25.2 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc6_26.4: init %C to file.%c.var = class_init (%.loc6_26.3) [concrete = constants.%C.val]
 // CHECK:STDOUT:   %.loc6_1: init %C = converted %.loc6_26.1, %.loc6_26.4 [concrete = constants.%C.val]
@@ -832,7 +832,7 @@ alias C = Other.C;
 // CHECK:STDOUT:   %.loc11_25.1: %empty_tuple.type = tuple_literal () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc11_26.1: %struct_type.x = struct_literal (%.loc11_25.1) [concrete = constants.%struct]
 // CHECK:STDOUT:   %.loc11_26.2: ref %empty_tuple.type = class_element_access file.%c.var, element0 [concrete = constants.%.dd7]
-// CHECK:STDOUT:   %.loc11_25.2: init %empty_tuple.type to %.loc11_26.2 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc11_25.2: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc11_26.3: init %empty_tuple.type = converted %.loc11_25.1, %.loc11_25.2 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc11_26.4: init %C to file.%c.var = class_init (%.loc11_26.3) [concrete = constants.%C.val]
 // CHECK:STDOUT:   %.loc11_1: init %C = converted %.loc11_26.1, %.loc11_26.4 [concrete = constants.%C.val]
diff --git a/toolchain/check/testdata/packages/export_import.carbon b/toolchain/check/testdata/packages/export_import.carbon
index 1a39cdca38a5..35559d6c856f 100644
--- a/toolchain/check/testdata/packages/export_import.carbon
+++ b/toolchain/check/testdata/packages/export_import.carbon
@@ -340,7 +340,7 @@ export Poison;
 // CHECK:STDOUT:   %.loc6_19.1: %empty_tuple.type = tuple_literal () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc6_20.1: %struct_type.x = struct_literal (%.loc6_19.1) [concrete = constants.%struct]
 // CHECK:STDOUT:   %.loc6_20.2: ref %empty_tuple.type = class_element_access file.%c.var, element0 [concrete = constants.%.1d2]
-// CHECK:STDOUT:   %.loc6_19.2: init %empty_tuple.type to %.loc6_20.2 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc6_19.2: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc6_20.3: init %empty_tuple.type = converted %.loc6_19.1, %.loc6_19.2 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc6_20.4: init %C to file.%c.var = class_init (%.loc6_20.3) [concrete = constants.%C.val]
 // CHECK:STDOUT:   %.loc6_1: init %C = converted %.loc6_20.1, %.loc6_20.4 [concrete = constants.%C.val]
@@ -400,7 +400,7 @@ export Poison;
 // CHECK:STDOUT:   %.loc4_19.1: %empty_tuple.type = tuple_literal () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc4_20.1: %struct_type.x = struct_literal (%.loc4_19.1) [concrete = constants.%struct]
 // CHECK:STDOUT:   %.loc4_20.2: ref %empty_tuple.type = class_element_access file.%c.var, element0 [concrete = constants.%.1d2]
-// CHECK:STDOUT:   %.loc4_19.2: init %empty_tuple.type to %.loc4_20.2 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc4_19.2: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc4_20.3: init %empty_tuple.type = converted %.loc4_19.1, %.loc4_19.2 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc4_20.4: init %C to file.%c.var = class_init (%.loc4_20.3) [concrete = constants.%C.val]
 // CHECK:STDOUT:   %.loc4_1: init %C = converted %.loc4_20.1, %.loc4_20.4 [concrete = constants.%C.val]
@@ -457,7 +457,7 @@ export Poison;
 // CHECK:STDOUT:   %.loc6_19.1: %empty_tuple.type = tuple_literal () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc6_20.1: %struct_type.x = struct_literal (%.loc6_19.1) [concrete = constants.%struct]
 // CHECK:STDOUT:   %.loc6_20.2: ref %empty_tuple.type = class_element_access file.%c.var, element0 [concrete = constants.%.1d2]
-// CHECK:STDOUT:   %.loc6_19.2: init %empty_tuple.type to %.loc6_20.2 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc6_19.2: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc6_20.3: init %empty_tuple.type = converted %.loc6_19.1, %.loc6_19.2 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc6_20.4: init %C to file.%c.var = class_init (%.loc6_20.3) [concrete = constants.%C.val]
 // CHECK:STDOUT:   %.loc6_1: init %C = converted %.loc6_20.1, %.loc6_20.4 [concrete = constants.%C.val]
@@ -514,7 +514,7 @@ export Poison;
 // CHECK:STDOUT:   %.loc6_19.1: %empty_tuple.type = tuple_literal () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc6_20.1: %struct_type.x = struct_literal (%.loc6_19.1) [concrete = constants.%struct]
 // CHECK:STDOUT:   %.loc6_20.2: ref %empty_tuple.type = class_element_access file.%c.var, element0 [concrete = constants.%.1d2]
-// CHECK:STDOUT:   %.loc6_19.2: init %empty_tuple.type to %.loc6_20.2 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc6_19.2: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc6_20.3: init %empty_tuple.type = converted %.loc6_19.1, %.loc6_19.2 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc6_20.4: init %C to file.%c.var = class_init (%.loc6_20.3) [concrete = constants.%C.val]
 // CHECK:STDOUT:   %.loc6_1: init %C = converted %.loc6_20.1, %.loc6_20.4 [concrete = constants.%C.val]
@@ -571,7 +571,7 @@ export Poison;
 // CHECK:STDOUT:   %.loc6_19.1: %empty_tuple.type = tuple_literal () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc6_20.1: %struct_type.x = struct_literal (%.loc6_19.1) [concrete = constants.%struct]
 // CHECK:STDOUT:   %.loc6_20.2: ref %empty_tuple.type = class_element_access file.%c.var, element0 [concrete = constants.%.1d2]
-// CHECK:STDOUT:   %.loc6_19.2: init %empty_tuple.type to %.loc6_20.2 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc6_19.2: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc6_20.3: init %empty_tuple.type = converted %.loc6_19.1, %.loc6_19.2 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc6_20.4: init %C to file.%c.var = class_init (%.loc6_20.3) [concrete = constants.%C.val]
 // CHECK:STDOUT:   %.loc6_1: init %C = converted %.loc6_20.1, %.loc6_20.4 [concrete = constants.%C.val]
@@ -628,7 +628,7 @@ export Poison;
 // CHECK:STDOUT:   %.loc7_19.1: %empty_tuple.type = tuple_literal () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc7_20.1: %struct_type.x = struct_literal (%.loc7_19.1) [concrete = constants.%struct]
 // CHECK:STDOUT:   %.loc7_20.2: ref %empty_tuple.type = class_element_access file.%c.var, element0 [concrete = constants.%.1d2]
-// CHECK:STDOUT:   %.loc7_19.2: init %empty_tuple.type to %.loc7_20.2 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc7_19.2: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc7_20.3: init %empty_tuple.type = converted %.loc7_19.1, %.loc7_19.2 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc7_20.4: init %C to file.%c.var = class_init (%.loc7_20.3) [concrete = constants.%C.val]
 // CHECK:STDOUT:   %.loc7_1: init %C = converted %.loc7_20.1, %.loc7_20.4 [concrete = constants.%C.val]
@@ -685,7 +685,7 @@ export Poison;
 // CHECK:STDOUT:   %.loc7_19.1: %empty_tuple.type = tuple_literal () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc7_20.1: %struct_type.x = struct_literal (%.loc7_19.1) [concrete = constants.%struct]
 // CHECK:STDOUT:   %.loc7_20.2: ref %empty_tuple.type = class_element_access file.%c.var, element0 [concrete = constants.%.1d2]
-// CHECK:STDOUT:   %.loc7_19.2: init %empty_tuple.type to %.loc7_20.2 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc7_19.2: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc7_20.3: init %empty_tuple.type = converted %.loc7_19.1, %.loc7_19.2 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc7_20.4: init %C to file.%c.var = class_init (%.loc7_20.3) [concrete = constants.%C.val]
 // CHECK:STDOUT:   %.loc7_1: init %C = converted %.loc7_20.1, %.loc7_20.4 [concrete = constants.%C.val]
@@ -742,7 +742,7 @@ export Poison;
 // CHECK:STDOUT:   %.loc7_19.1: %empty_tuple.type = tuple_literal () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc7_20.1: %struct_type.x = struct_literal (%.loc7_19.1) [concrete = constants.%struct]
 // CHECK:STDOUT:   %.loc7_20.2: ref %empty_tuple.type = class_element_access file.%c.var, element0 [concrete = constants.%.1d2]
-// CHECK:STDOUT:   %.loc7_19.2: init %empty_tuple.type to %.loc7_20.2 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc7_19.2: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc7_20.3: init %empty_tuple.type = converted %.loc7_19.1, %.loc7_19.2 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc7_20.4: init %C to file.%c.var = class_init (%.loc7_20.3) [concrete = constants.%C.val]
 // CHECK:STDOUT:   %.loc7_1: init %C = converted %.loc7_20.1, %.loc7_20.4 [concrete = constants.%C.val]
@@ -811,7 +811,7 @@ export Poison;
 // CHECK:STDOUT:   %.loc7_19.1: %empty_tuple.type = tuple_literal () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc7_20.1: %struct_type.x = struct_literal (%.loc7_19.1) [concrete = constants.%struct]
 // CHECK:STDOUT:   %.loc7_20.2: ref %empty_tuple.type = class_element_access file.%c.var, element0 [concrete = constants.%.1d2]
-// CHECK:STDOUT:   %.loc7_19.2: init %empty_tuple.type to %.loc7_20.2 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc7_19.2: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc7_20.3: init %empty_tuple.type = converted %.loc7_19.1, %.loc7_19.2 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc7_20.4: init %C to file.%c.var = class_init (%.loc7_20.3) [concrete = constants.%C.val]
 // CHECK:STDOUT:   %.loc7_1: init %C = converted %.loc7_20.1, %.loc7_20.4 [concrete = constants.%C.val]
@@ -870,7 +870,7 @@ export Poison;
 // CHECK:STDOUT:   %.loc6_28.1: %empty_tuple.type = tuple_literal () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc6_29.1: %struct_type.x = struct_literal (%.loc6_28.1) [concrete = constants.%struct]
 // CHECK:STDOUT:   %.loc6_29.2: ref %empty_tuple.type = class_element_access file.%indirect_c.var, element0 [concrete = constants.%.ef1]
-// CHECK:STDOUT:   %.loc6_28.2: init %empty_tuple.type to %.loc6_29.2 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc6_28.2: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc6_29.3: init %empty_tuple.type = converted %.loc6_28.1, %.loc6_28.2 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc6_29.4: init %C to file.%indirect_c.var = class_init (%.loc6_29.3) [concrete = constants.%C.val]
 // CHECK:STDOUT:   %.loc6_1: init %C = converted %.loc6_29.1, %.loc6_29.4 [concrete = constants.%C.val]
diff --git a/toolchain/check/testdata/packages/export_mixed.carbon b/toolchain/check/testdata/packages/export_mixed.carbon
index b77ee21f20e7..3f42fe46e4cb 100644
--- a/toolchain/check/testdata/packages/export_mixed.carbon
+++ b/toolchain/check/testdata/packages/export_mixed.carbon
@@ -311,7 +311,7 @@ var d: D = {.y = ()};
 // CHECK:STDOUT:   %.loc6_19.1: %empty_tuple.type = tuple_literal () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc6_20.1: %struct_type.x = struct_literal (%.loc6_19.1) [concrete = constants.%struct]
 // CHECK:STDOUT:   %.loc6_20.2: ref %empty_tuple.type = class_element_access file.%c.var, element0 [concrete = constants.%.1d2]
-// CHECK:STDOUT:   %.loc6_19.2: init %empty_tuple.type to %.loc6_20.2 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc6_19.2: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc6_20.3: init %empty_tuple.type = converted %.loc6_19.1, %.loc6_19.2 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc6_20.4: init %C to file.%c.var = class_init (%.loc6_20.3) [concrete = constants.%C.val]
 // CHECK:STDOUT:   %.loc6_1: init %C = converted %.loc6_20.1, %.loc6_20.4 [concrete = constants.%C.val]
@@ -368,7 +368,7 @@ var d: D = {.y = ()};
 // CHECK:STDOUT:   %.loc6_19.1: %empty_tuple.type = tuple_literal () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc6_20.1: %struct_type.x = struct_literal (%.loc6_19.1) [concrete = constants.%struct]
 // CHECK:STDOUT:   %.loc6_20.2: ref %empty_tuple.type = class_element_access file.%c.var, element0 [concrete = constants.%.1d2]
-// CHECK:STDOUT:   %.loc6_19.2: init %empty_tuple.type to %.loc6_20.2 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc6_19.2: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc6_20.3: init %empty_tuple.type = converted %.loc6_19.1, %.loc6_19.2 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc6_20.4: init %C to file.%c.var = class_init (%.loc6_20.3) [concrete = constants.%C.val]
 // CHECK:STDOUT:   %.loc6_1: init %C = converted %.loc6_20.1, %.loc6_20.4 [concrete = constants.%C.val]
@@ -425,7 +425,7 @@ var d: D = {.y = ()};
 // CHECK:STDOUT:   %.loc7_19.1: %empty_tuple.type = tuple_literal () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc7_20.1: %struct_type.x = struct_literal (%.loc7_19.1) [concrete = constants.%struct]
 // CHECK:STDOUT:   %.loc7_20.2: ref %empty_tuple.type = class_element_access file.%c.var, element0 [concrete = constants.%.1d2]
-// CHECK:STDOUT:   %.loc7_19.2: init %empty_tuple.type to %.loc7_20.2 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc7_19.2: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc7_20.3: init %empty_tuple.type = converted %.loc7_19.1, %.loc7_19.2 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc7_20.4: init %C to file.%c.var = class_init (%.loc7_20.3) [concrete = constants.%C.val]
 // CHECK:STDOUT:   %.loc7_1: init %C = converted %.loc7_20.1, %.loc7_20.4 [concrete = constants.%C.val]
@@ -519,7 +519,7 @@ var d: D = {.y = ()};
 // CHECK:STDOUT:   %.loc7_19.1: %empty_tuple.type = tuple_literal () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc7_20.1: %struct_type.x = struct_literal (%.loc7_19.1) [concrete = constants.%struct]
 // CHECK:STDOUT:   %.loc7_20.2: ref %empty_tuple.type = class_element_access file.%c.var, element0 [concrete = constants.%.1d2]
-// CHECK:STDOUT:   %.loc7_19.2: init %empty_tuple.type to %.loc7_20.2 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc7_19.2: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc7_20.3: init %empty_tuple.type = converted %.loc7_19.1, %.loc7_19.2 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc7_20.4: init %C to file.%c.var = class_init (%.loc7_20.3) [concrete = constants.%C.val]
 // CHECK:STDOUT:   %.loc7_1: init %C = converted %.loc7_20.1, %.loc7_20.4 [concrete = constants.%C.val]
@@ -604,7 +604,7 @@ var d: D = {.y = ()};
 // CHECK:STDOUT:   %.loc8_19.1: %empty_tuple.type = tuple_literal () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc8_20.1: %struct_type.x = struct_literal (%.loc8_19.1) [concrete = constants.%struct.948]
 // CHECK:STDOUT:   %.loc8_20.2: ref %empty_tuple.type = class_element_access file.%c.var, element0 [concrete = constants.%.1d2]
-// CHECK:STDOUT:   %.loc8_19.2: init %empty_tuple.type to %.loc8_20.2 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc8_19.2: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc8_20.3: init %empty_tuple.type = converted %.loc8_19.1, %.loc8_19.2 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc8_20.4: init %C to file.%c.var = class_init (%.loc8_20.3) [concrete = constants.%C.val]
 // CHECK:STDOUT:   %.loc8_1: init %C = converted %.loc8_20.1, %.loc8_20.4 [concrete = constants.%C.val]
@@ -612,7 +612,7 @@ var d: D = {.y = ()};
 // CHECK:STDOUT:   %.loc9_19.1: %empty_tuple.type = tuple_literal () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc9_20.1: %struct_type.y = struct_literal (%.loc9_19.1) [concrete = constants.%struct.8ce]
 // CHECK:STDOUT:   %.loc9_20.2: ref %empty_tuple.type = class_element_access file.%d.var, element0 [concrete = constants.%.0cf]
-// CHECK:STDOUT:   %.loc9_19.2: init %empty_tuple.type to %.loc9_20.2 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc9_19.2: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc9_20.3: init %empty_tuple.type = converted %.loc9_19.1, %.loc9_19.2 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc9_20.4: init %D to file.%d.var = class_init (%.loc9_20.3) [concrete = constants.%D.val]
 // CHECK:STDOUT:   %.loc9_1: init %D = converted %.loc9_20.1, %.loc9_20.4 [concrete = constants.%D.val]
diff --git a/toolchain/check/testdata/packages/export_name.carbon b/toolchain/check/testdata/packages/export_name.carbon
index 55939d2dceee..921687f8c401 100644
--- a/toolchain/check/testdata/packages/export_name.carbon
+++ b/toolchain/check/testdata/packages/export_name.carbon
@@ -471,7 +471,7 @@ private export C;
 // CHECK:STDOUT:   %.loc6_19.1: %empty_tuple.type = tuple_literal () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc6_20.1: %struct_type.x = struct_literal (%.loc6_19.1) [concrete = constants.%struct.948]
 // CHECK:STDOUT:   %.loc6_20.2: ref %empty_tuple.type = class_element_access file.%c.var, element0 [concrete = constants.%.1d2]
-// CHECK:STDOUT:   %.loc6_19.2: init %empty_tuple.type to %.loc6_20.2 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc6_19.2: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc6_20.3: init %empty_tuple.type = converted %.loc6_19.1, %.loc6_19.2 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc6_20.4: init %C to file.%c.var = class_init (%.loc6_20.3) [concrete = constants.%C.val]
 // CHECK:STDOUT:   %.loc6_1: init %C = converted %.loc6_20.1, %.loc6_20.4 [concrete = constants.%C.val]
@@ -479,7 +479,7 @@ private export C;
 // CHECK:STDOUT:   %.loc7_26.1: %empty_tuple.type = tuple_literal () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc7_27.1: %struct_type.y = struct_literal (%.loc7_26.1) [concrete = constants.%struct.8ce]
 // CHECK:STDOUT:   %.loc7_27.2: ref %empty_tuple.type = class_element_access file.%nsc.var, element0 [concrete = constants.%.160]
-// CHECK:STDOUT:   %.loc7_26.2: init %empty_tuple.type to %.loc7_27.2 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc7_26.2: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc7_27.3: init %empty_tuple.type = converted %.loc7_26.1, %.loc7_26.2 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc7_27.4: init %NSC to file.%nsc.var = class_init (%.loc7_27.3) [concrete = constants.%NSC.val]
 // CHECK:STDOUT:   %.loc7_1: init %NSC = converted %.loc7_27.1, %.loc7_27.4 [concrete = constants.%NSC.val]
@@ -572,7 +572,7 @@ private export C;
 // CHECK:STDOUT:   %.loc4_19.1: %empty_tuple.type = tuple_literal () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc4_20.1: %struct_type.x = struct_literal (%.loc4_19.1) [concrete = constants.%struct.948]
 // CHECK:STDOUT:   %.loc4_20.2: ref %empty_tuple.type = class_element_access file.%c.var, element0 [concrete = constants.%.1d2]
-// CHECK:STDOUT:   %.loc4_19.2: init %empty_tuple.type to %.loc4_20.2 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc4_19.2: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc4_20.3: init %empty_tuple.type = converted %.loc4_19.1, %.loc4_19.2 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc4_20.4: init %C to file.%c.var = class_init (%.loc4_20.3) [concrete = constants.%C.val]
 // CHECK:STDOUT:   %.loc4_1: init %C = converted %.loc4_20.1, %.loc4_20.4 [concrete = constants.%C.val]
@@ -580,7 +580,7 @@ private export C;
 // CHECK:STDOUT:   %.loc5_26.1: %empty_tuple.type = tuple_literal () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc5_27.1: %struct_type.y = struct_literal (%.loc5_26.1) [concrete = constants.%struct.8ce]
 // CHECK:STDOUT:   %.loc5_27.2: ref %empty_tuple.type = class_element_access file.%nsc.var, element0 [concrete = constants.%.2e1]
-// CHECK:STDOUT:   %.loc5_26.2: init %empty_tuple.type to %.loc5_27.2 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc5_26.2: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc5_27.3: init %empty_tuple.type = converted %.loc5_26.1, %.loc5_26.2 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc5_27.4: init %NSC to file.%nsc.var = class_init (%.loc5_27.3) [concrete = constants.%NSC.val]
 // CHECK:STDOUT:   %.loc5_1: init %NSC = converted %.loc5_27.1, %.loc5_27.4 [concrete = constants.%NSC.val]
@@ -672,7 +672,7 @@ private export C;
 // CHECK:STDOUT:   %.loc6_19.1: %empty_tuple.type = tuple_literal () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc6_20.1: %struct_type.x = struct_literal (%.loc6_19.1) [concrete = constants.%struct.948]
 // CHECK:STDOUT:   %.loc6_20.2: ref %empty_tuple.type = class_element_access file.%c.var, element0 [concrete = constants.%.1d2]
-// CHECK:STDOUT:   %.loc6_19.2: init %empty_tuple.type to %.loc6_20.2 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc6_19.2: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc6_20.3: init %empty_tuple.type = converted %.loc6_19.1, %.loc6_19.2 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc6_20.4: init %C to file.%c.var = class_init (%.loc6_20.3) [concrete = constants.%C.val]
 // CHECK:STDOUT:   %.loc6_1: init %C = converted %.loc6_20.1, %.loc6_20.4 [concrete = constants.%C.val]
@@ -680,7 +680,7 @@ private export C;
 // CHECK:STDOUT:   %.loc7_26.1: %empty_tuple.type = tuple_literal () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc7_27.1: %struct_type.y = struct_literal (%.loc7_26.1) [concrete = constants.%struct.8ce]
 // CHECK:STDOUT:   %.loc7_27.2: ref %empty_tuple.type = class_element_access file.%nsc.var, element0 [concrete = constants.%.2e1]
-// CHECK:STDOUT:   %.loc7_26.2: init %empty_tuple.type to %.loc7_27.2 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc7_26.2: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc7_27.3: init %empty_tuple.type = converted %.loc7_26.1, %.loc7_26.2 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc7_27.4: init %NSC to file.%nsc.var = class_init (%.loc7_27.3) [concrete = constants.%NSC.val]
 // CHECK:STDOUT:   %.loc7_1: init %NSC = converted %.loc7_27.1, %.loc7_27.4 [concrete = constants.%NSC.val]
@@ -851,7 +851,7 @@ private export C;
 // CHECK:STDOUT:   %.loc7_19.1: %empty_tuple.type = tuple_literal () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc7_20.1: %struct_type.x = struct_literal (%.loc7_19.1) [concrete = constants.%struct.948]
 // CHECK:STDOUT:   %.loc7_20.2: ref %empty_tuple.type = class_element_access file.%c.var, element0 [concrete = constants.%.1d2]
-// CHECK:STDOUT:   %.loc7_19.2: init %empty_tuple.type to %.loc7_20.2 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc7_19.2: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc7_20.3: init %empty_tuple.type = converted %.loc7_19.1, %.loc7_19.2 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc7_20.4: init %C to file.%c.var = class_init (%.loc7_20.3) [concrete = constants.%C.val]
 // CHECK:STDOUT:   %.loc7_1: init %C = converted %.loc7_20.1, %.loc7_20.4 [concrete = constants.%C.val]
@@ -859,7 +859,7 @@ private export C;
 // CHECK:STDOUT:   %.loc8_26.1: %empty_tuple.type = tuple_literal () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc8_27.1: %struct_type.y = struct_literal (%.loc8_26.1) [concrete = constants.%struct.8ce]
 // CHECK:STDOUT:   %.loc8_27.2: ref %empty_tuple.type = class_element_access file.%nsc.var, element0 [concrete = constants.%.b2f]
-// CHECK:STDOUT:   %.loc8_26.2: init %empty_tuple.type to %.loc8_27.2 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc8_26.2: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc8_27.3: init %empty_tuple.type = converted %.loc8_26.1, %.loc8_26.2 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc8_27.4: init %NSC to file.%nsc.var = class_init (%.loc8_27.3) [concrete = constants.%NSC.val]
 // CHECK:STDOUT:   %.loc8_1: init %NSC = converted %.loc8_27.1, %.loc8_27.4 [concrete = constants.%NSC.val]
@@ -951,7 +951,7 @@ private export C;
 // CHECK:STDOUT:   %.loc7_19.1: %empty_tuple.type = tuple_literal () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc7_20.1: %struct_type.x = struct_literal (%.loc7_19.1) [concrete = constants.%struct.948]
 // CHECK:STDOUT:   %.loc7_20.2: ref %empty_tuple.type = class_element_access file.%c.var, element0 [concrete = constants.%.1d2]
-// CHECK:STDOUT:   %.loc7_19.2: init %empty_tuple.type to %.loc7_20.2 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc7_19.2: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc7_20.3: init %empty_tuple.type = converted %.loc7_19.1, %.loc7_19.2 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc7_20.4: init %C to file.%c.var = class_init (%.loc7_20.3) [concrete = constants.%C.val]
 // CHECK:STDOUT:   %.loc7_1: init %C = converted %.loc7_20.1, %.loc7_20.4 [concrete = constants.%C.val]
@@ -959,7 +959,7 @@ private export C;
 // CHECK:STDOUT:   %.loc8_26.1: %empty_tuple.type = tuple_literal () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc8_27.1: %struct_type.y = struct_literal (%.loc8_26.1) [concrete = constants.%struct.8ce]
 // CHECK:STDOUT:   %.loc8_27.2: ref %empty_tuple.type = class_element_access file.%nsc.var, element0 [concrete = constants.%.160]
-// CHECK:STDOUT:   %.loc8_26.2: init %empty_tuple.type to %.loc8_27.2 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc8_26.2: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc8_27.3: init %empty_tuple.type = converted %.loc8_26.1, %.loc8_26.2 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc8_27.4: init %NSC to file.%nsc.var = class_init (%.loc8_27.3) [concrete = constants.%NSC.val]
 // CHECK:STDOUT:   %.loc8_1: init %NSC = converted %.loc8_27.1, %.loc8_27.4 [concrete = constants.%NSC.val]
@@ -1074,7 +1074,7 @@ private export C;
 // CHECK:STDOUT:   %.loc6_19.1: %empty_tuple.type = tuple_literal () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc6_20.1: %struct_type.x = struct_literal (%.loc6_19.1) [concrete = constants.%struct]
 // CHECK:STDOUT:   %.loc6_20.2: ref %empty_tuple.type = class_element_access file.%c.var, element0 [concrete = constants.%.1d2]
-// CHECK:STDOUT:   %.loc6_19.2: init %empty_tuple.type to %.loc6_20.2 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc6_19.2: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc6_20.3: init %empty_tuple.type = converted %.loc6_19.1, %.loc6_19.2 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc6_20.4: init %C to file.%c.var = class_init (%.loc6_20.3) [concrete = constants.%C.val]
 // CHECK:STDOUT:   %.loc6_1: init %C = converted %.loc6_20.1, %.loc6_20.4 [concrete = constants.%C.val]
diff --git a/toolchain/check/testdata/packages/raw_core.carbon b/toolchain/check/testdata/packages/raw_core.carbon
index de9079aa83e4..5d270db2547e 100644
--- a/toolchain/check/testdata/packages/raw_core.carbon
+++ b/toolchain/check/testdata/packages/raw_core.carbon
@@ -307,7 +307,7 @@ var c: r#Core = {.n = 0 as Core.Int(32)};
 // CHECK:STDOUT:   %bound_method.loc6_25.4: <bound method> = bound_method %.loc6_25.2, %specific_fn.loc6_25.2 [concrete = constants.%bound_method.5f6]
 // CHECK:STDOUT:   %Int.as.Copy.impl.Op.call: init %i32 = call %bound_method.loc6_25.4(%.loc6_25.2) [concrete = constants.%int_0.6a9]
 // CHECK:STDOUT:   %.loc6_40.2: ref %i32 = class_element_access file.%c.var, element0 [concrete = constants.%.cb0]
-// CHECK:STDOUT:   %.loc6_40.3: init %i32 to %.loc6_40.2 = initialize_from %Int.as.Copy.impl.Op.call [concrete = constants.%int_0.6a9]
+// CHECK:STDOUT:   %.loc6_40.3: init %i32 to %.loc6_40.2 = in_place_init %Int.as.Copy.impl.Op.call [concrete = constants.%int_0.6a9]
 // CHECK:STDOUT:   %.loc6_40.4: init %Core to file.%c.var = class_init (%.loc6_40.3) [concrete = constants.%Core.val]
 // CHECK:STDOUT:   %.loc6_1: init %Core = converted %.loc6_40.1, %.loc6_40.4 [concrete = constants.%Core.val]
 // CHECK:STDOUT:   assign file.%c.var, %.loc6_1
diff --git a/toolchain/check/testdata/pointer/address_of_lvalue.carbon b/toolchain/check/testdata/pointer/address_of_lvalue.carbon
index e139969fb9c9..825464e5dd22 100644
--- a/toolchain/check/testdata/pointer/address_of_lvalue.carbon
+++ b/toolchain/check/testdata/pointer/address_of_lvalue.carbon
@@ -145,7 +145,7 @@ fn F() {
 // CHECK:STDOUT:   %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc16_46.1: init %i32 = call %bound_method.loc16_46.2(%int_1.loc16) [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %.loc16_46.2: init %i32 = converted %int_1.loc16, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc16_46.1 [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %.loc16_46.3: ref %i32 = struct_access %s.var, element0
-// CHECK:STDOUT:   %.loc16_46.4: init %i32 to %.loc16_46.3 = initialize_from %.loc16_46.2 [concrete = constants.%int_1.5d2]
+// CHECK:STDOUT:   %.loc16_46.4: init %i32 to %.loc16_46.3 = in_place_init %.loc16_46.2 [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %impl.elem0.loc16_46.2: %.863 = impl_witness_access constants.%ImplicitAs.impl_witness.6bc, element0 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.0b5]
 // CHECK:STDOUT:   %bound_method.loc16_46.3: <bound method> = bound_method %int_2.loc16, %impl.elem0.loc16_46.2 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.bound.4e5]
 // CHECK:STDOUT:   %specific_fn.loc16_46.2: <specific function> = specific_function %impl.elem0.loc16_46.2, @Core.IntLiteral.as.ImplicitAs.impl.Convert(constants.%int_32) [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.specific_fn]
@@ -153,7 +153,7 @@ fn F() {
 // CHECK:STDOUT:   %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc16_46.2: init %i32 = call %bound_method.loc16_46.4(%int_2.loc16) [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %.loc16_46.5: init %i32 = converted %int_2.loc16, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc16_46.2 [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %.loc16_46.6: ref %i32 = struct_access %s.var, element1
-// CHECK:STDOUT:   %.loc16_46.7: init %i32 to %.loc16_46.6 = initialize_from %.loc16_46.5 [concrete = constants.%int_2.ef8]
+// CHECK:STDOUT:   %.loc16_46.7: init %i32 to %.loc16_46.6 = in_place_init %.loc16_46.5 [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %.loc16_46.8: init %struct_type.a.b.501 to %s.var = struct_init (%.loc16_46.4, %.loc16_46.7) [concrete = constants.%struct.ed5]
 // CHECK:STDOUT:   %.loc16_3: init %struct_type.a.b.501 = converted %.loc16_46.1, %.loc16_46.8 [concrete = constants.%struct.ed5]
 // CHECK:STDOUT:   assign %s.var, %.loc16_3
@@ -242,7 +242,7 @@ fn F() {
 // CHECK:STDOUT:   %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc22_28.1: init %i32 = call %bound_method.loc22_28.2(%int_1.loc22) [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %.loc22_28.2: init %i32 = converted %int_1.loc22, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc22_28.1 [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %tuple.elem0.loc22: ref %i32 = tuple_access %t.var, element0
-// CHECK:STDOUT:   %.loc22_28.3: init %i32 to %tuple.elem0.loc22 = initialize_from %.loc22_28.2 [concrete = constants.%int_1.5d2]
+// CHECK:STDOUT:   %.loc22_28.3: init %i32 to %tuple.elem0.loc22 = in_place_init %.loc22_28.2 [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %impl.elem0.loc22_28.2: %.863 = impl_witness_access constants.%ImplicitAs.impl_witness.6bc, element0 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.0b5]
 // CHECK:STDOUT:   %bound_method.loc22_28.3: <bound method> = bound_method %int_2.loc22, %impl.elem0.loc22_28.2 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.bound.4e5]
 // CHECK:STDOUT:   %specific_fn.loc22_28.2: <specific function> = specific_function %impl.elem0.loc22_28.2, @Core.IntLiteral.as.ImplicitAs.impl.Convert(constants.%int_32) [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.specific_fn]
@@ -250,7 +250,7 @@ fn F() {
 // CHECK:STDOUT:   %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc22_28.2: init %i32 = call %bound_method.loc22_28.4(%int_2.loc22) [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %.loc22_28.4: init %i32 = converted %int_2.loc22, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc22_28.2 [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %tuple.elem1.loc22: ref %i32 = tuple_access %t.var, element1
-// CHECK:STDOUT:   %.loc22_28.5: init %i32 to %tuple.elem1.loc22 = initialize_from %.loc22_28.4 [concrete = constants.%int_2.ef8]
+// CHECK:STDOUT:   %.loc22_28.5: init %i32 to %tuple.elem1.loc22 = in_place_init %.loc22_28.4 [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %.loc22_28.6: init %tuple.type.d07 to %t.var = tuple_init (%.loc22_28.3, %.loc22_28.5) [concrete = constants.%tuple.21c]
 // CHECK:STDOUT:   %.loc22_3: init %tuple.type.d07 = converted %.loc22_28.1, %.loc22_28.6 [concrete = constants.%tuple.21c]
 // CHECK:STDOUT:   assign %t.var, %.loc22_3
diff --git a/toolchain/check/testdata/return/fail_return_with_returned_var.carbon b/toolchain/check/testdata/return/fail_return_with_returned_var.carbon
index e8d738901f60..ec7140679bf0 100644
--- a/toolchain/check/testdata/return/fail_return_with_returned_var.carbon
+++ b/toolchain/check/testdata/return/fail_return_with_returned_var.carbon
@@ -195,7 +195,7 @@ fn G() -> C {
 // CHECK:STDOUT:   %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc29_38.1: init %i32 = call %bound_method.loc29_38.2(%int_1) [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %.loc29_38.2: init %i32 = converted %int_1, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc29_38.1 [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %.loc29_38.3: ref %i32 = class_element_access %return.param, element0
-// CHECK:STDOUT:   %.loc29_38.4: init %i32 to %.loc29_38.3 = initialize_from %.loc29_38.2 [concrete = constants.%int_1.5d2]
+// CHECK:STDOUT:   %.loc29_38.4: init %i32 to %.loc29_38.3 = in_place_init %.loc29_38.2 [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %impl.elem0.loc29_38.2: %.863 = impl_witness_access constants.%ImplicitAs.impl_witness.6bc, element0 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.0b5]
 // CHECK:STDOUT:   %bound_method.loc29_38.3: <bound method> = bound_method %int_2, %impl.elem0.loc29_38.2 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.bound.4e5]
 // CHECK:STDOUT:   %specific_fn.loc29_38.2: <specific function> = specific_function %impl.elem0.loc29_38.2, @Core.IntLiteral.as.ImplicitAs.impl.Convert(constants.%int_32) [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.specific_fn]
@@ -203,7 +203,7 @@ fn G() -> C {
 // CHECK:STDOUT:   %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc29_38.2: init %i32 = call %bound_method.loc29_38.4(%int_2) [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %.loc29_38.5: init %i32 = converted %int_2, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc29_38.2 [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %.loc29_38.6: ref %i32 = class_element_access %return.param, element1
-// CHECK:STDOUT:   %.loc29_38.7: init %i32 to %.loc29_38.6 = initialize_from %.loc29_38.5 [concrete = constants.%int_2.ef8]
+// CHECK:STDOUT:   %.loc29_38.7: init %i32 to %.loc29_38.6 = in_place_init %.loc29_38.5 [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %.loc29_38.8: init %C to %return.param = class_init (%.loc29_38.4, %.loc29_38.7) [concrete = constants.%C.val]
 // CHECK:STDOUT:   %.loc29_12: init %C = converted %.loc29_38.1, %.loc29_38.8 [concrete = constants.%C.val]
 // CHECK:STDOUT:   assign %return.param, %.loc29_12
diff --git a/toolchain/check/testdata/return/import_convert_function.carbon b/toolchain/check/testdata/return/import_convert_function.carbon
index f2bc8d478367..39789e13e256 100644
--- a/toolchain/check/testdata/return/import_convert_function.carbon
+++ b/toolchain/check/testdata/return/import_convert_function.carbon
@@ -576,7 +576,7 @@ fn F0(n: i32) -> P.D {
 // CHECK:STDOUT:   %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc6_40.1: init %i32 = call %bound_method.loc6_40.2(%int_0.loc6_31) [concrete = constants.%int_0.6a9]
 // CHECK:STDOUT:   %.loc6_40.2: init %i32 = converted %int_0.loc6_31, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc6_40.1 [concrete = constants.%int_0.6a9]
 // CHECK:STDOUT:   %.loc6_40.3: ref %i32 = class_element_access %return.param, element0
-// CHECK:STDOUT:   %.loc6_40.4: init %i32 to %.loc6_40.3 = initialize_from %.loc6_40.2 [concrete = constants.%int_0.6a9]
+// CHECK:STDOUT:   %.loc6_40.4: init %i32 to %.loc6_40.3 = in_place_init %.loc6_40.2 [concrete = constants.%int_0.6a9]
 // CHECK:STDOUT:   %impl.elem0.loc6_40.2: %.863 = impl_witness_access constants.%ImplicitAs.impl_witness.6bc, element0 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.0b5]
 // CHECK:STDOUT:   %bound_method.loc6_40.3: <bound method> = bound_method %int_0.loc6_39, %impl.elem0.loc6_40.2 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.bound.897]
 // CHECK:STDOUT:   %specific_fn.loc6_40.2: <specific function> = specific_function %impl.elem0.loc6_40.2, @Core.IntLiteral.as.ImplicitAs.impl.Convert(constants.%int_32) [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.specific_fn]
@@ -584,7 +584,7 @@ fn F0(n: i32) -> P.D {
 // CHECK:STDOUT:   %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc6_40.2: init %i32 = call %bound_method.loc6_40.4(%int_0.loc6_39) [concrete = constants.%int_0.6a9]
 // CHECK:STDOUT:   %.loc6_40.5: init %i32 = converted %int_0.loc6_39, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc6_40.2 [concrete = constants.%int_0.6a9]
 // CHECK:STDOUT:   %.loc6_40.6: ref %i32 = class_element_access %return.param, element1
-// CHECK:STDOUT:   %.loc6_40.7: init %i32 to %.loc6_40.6 = initialize_from %.loc6_40.5 [concrete = constants.%int_0.6a9]
+// CHECK:STDOUT:   %.loc6_40.7: init %i32 to %.loc6_40.6 = in_place_init %.loc6_40.5 [concrete = constants.%int_0.6a9]
 // CHECK:STDOUT:   %.loc6_40.8: init %D to %return.param = class_init (%.loc6_40.4, %.loc6_40.7) [concrete = constants.%D.val]
 // CHECK:STDOUT:   %.loc6_41: init %D = converted %.loc6_40.1, %.loc6_40.8 [concrete = constants.%D.val]
 // CHECK:STDOUT:   return %.loc6_41 to %return.param
diff --git a/toolchain/check/testdata/return/returned_var.carbon b/toolchain/check/testdata/return/returned_var.carbon
index 9b218f96f97c..fba47011c82f 100644
--- a/toolchain/check/testdata/return/returned_var.carbon
+++ b/toolchain/check/testdata/return/returned_var.carbon
@@ -157,7 +157,7 @@ fn G() -> i32 {
 // CHECK:STDOUT:   %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc21_43.1: init %i32 = call %bound_method.loc21_43.2(%int_1) [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %.loc21_43.2: init %i32 = converted %int_1, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc21_43.1 [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %.loc21_43.3: ref %i32 = class_element_access %return.param, element0
-// CHECK:STDOUT:   %.loc21_43.4: init %i32 to %.loc21_43.3 = initialize_from %.loc21_43.2 [concrete = constants.%int_1.5d2]
+// CHECK:STDOUT:   %.loc21_43.4: init %i32 to %.loc21_43.3 = in_place_init %.loc21_43.2 [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %impl.elem0.loc21_43.2: %.863 = impl_witness_access constants.%ImplicitAs.impl_witness.6bc, element0 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.0b5]
 // CHECK:STDOUT:   %bound_method.loc21_43.3: <bound method> = bound_method %int_2, %impl.elem0.loc21_43.2 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.bound.4e5]
 // CHECK:STDOUT:   %specific_fn.loc21_43.2: <specific function> = specific_function %impl.elem0.loc21_43.2, @Core.IntLiteral.as.ImplicitAs.impl.Convert(constants.%int_32) [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.specific_fn]
@@ -165,7 +165,7 @@ fn G() -> i32 {
 // CHECK:STDOUT:   %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc21_43.2: init %i32 = call %bound_method.loc21_43.4(%int_2) [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %.loc21_43.5: init %i32 = converted %int_2, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc21_43.2 [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %.loc21_43.6: ref %i32 = class_element_access %return.param, element1
-// CHECK:STDOUT:   %.loc21_43.7: init %i32 to %.loc21_43.6 = initialize_from %.loc21_43.5 [concrete = constants.%int_2.ef8]
+// CHECK:STDOUT:   %.loc21_43.7: init %i32 to %.loc21_43.6 = in_place_init %.loc21_43.5 [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %.loc21_43.8: init %C to %return.param = class_init (%.loc21_43.4, %.loc21_43.7) [concrete = constants.%C.val]
 // CHECK:STDOUT:   %.loc21_12: init %C = converted %.loc21_43.1, %.loc21_43.8 [concrete = constants.%C.val]
 // CHECK:STDOUT:   assign %return.param, %.loc21_12
diff --git a/toolchain/check/testdata/return/tuple.carbon b/toolchain/check/testdata/return/tuple.carbon
index 7f41f3e18273..2d364360a1ea 100644
--- a/toolchain/check/testdata/return/tuple.carbon
+++ b/toolchain/check/testdata/return/tuple.carbon
@@ -104,7 +104,7 @@ fn Main() -> (i32, i32) {
 // CHECK:STDOUT:   %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc17_17.1: init %i32 = call %bound_method.loc17_17.2(%int_15) [concrete = constants.%int_15.7f7]
 // CHECK:STDOUT:   %.loc17_17.2: init %i32 = converted %int_15, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc17_17.1 [concrete = constants.%int_15.7f7]
 // CHECK:STDOUT:   %tuple.elem0: ref %i32 = tuple_access %return.param, element0
-// CHECK:STDOUT:   %.loc17_17.3: init %i32 to %tuple.elem0 = initialize_from %.loc17_17.2 [concrete = constants.%int_15.7f7]
+// CHECK:STDOUT:   %.loc17_17.3: init %i32 to %tuple.elem0 = in_place_init %.loc17_17.2 [concrete = constants.%int_15.7f7]
 // CHECK:STDOUT:   %impl.elem0.loc17_17.2: %.863 = impl_witness_access constants.%ImplicitAs.impl_witness.6bc, element0 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.0b5]
 // CHECK:STDOUT:   %bound_method.loc17_17.3: <bound method> = bound_method %int_35, %impl.elem0.loc17_17.2 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.bound.4c2]
 // CHECK:STDOUT:   %specific_fn.loc17_17.2: <specific function> = specific_function %impl.elem0.loc17_17.2, @Core.IntLiteral.as.ImplicitAs.impl.Convert(constants.%int_32) [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.specific_fn]
@@ -112,7 +112,7 @@ fn Main() -> (i32, i32) {
 // CHECK:STDOUT:   %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc17_17.2: init %i32 = call %bound_method.loc17_17.4(%int_35) [concrete = constants.%int_35.c78]
 // CHECK:STDOUT:   %.loc17_17.4: init %i32 = converted %int_35, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc17_17.2 [concrete = constants.%int_35.c78]
 // CHECK:STDOUT:   %tuple.elem1: ref %i32 = tuple_access %return.param, element1
-// CHECK:STDOUT:   %.loc17_17.5: init %i32 to %tuple.elem1 = initialize_from %.loc17_17.4 [concrete = constants.%int_35.c78]
+// CHECK:STDOUT:   %.loc17_17.5: init %i32 to %tuple.elem1 = in_place_init %.loc17_17.4 [concrete = constants.%int_35.c78]
 // CHECK:STDOUT:   %.loc17_17.6: init %tuple.type.d07 to %return.param = tuple_init (%.loc17_17.3, %.loc17_17.5) [concrete = constants.%tuple.851]
 // CHECK:STDOUT:   %.loc17_18: init %tuple.type.d07 = converted %.loc17_17.1, %.loc17_17.6 [concrete = constants.%tuple.851]
 // CHECK:STDOUT:   return %.loc17_18 to %return.param
diff --git a/toolchain/check/testdata/struct/fail_member_access_type.carbon b/toolchain/check/testdata/struct/fail_member_access_type.carbon
index 5f5f39596f76..6d88143fb04b 100644
--- a/toolchain/check/testdata/struct/fail_member_access_type.carbon
+++ b/toolchain/check/testdata/struct/fail_member_access_type.carbon
@@ -110,7 +110,7 @@ var y: i32 = x.b;
 // CHECK:STDOUT:   %bound_method.loc15_29.2: <bound method> = bound_method %float, %specific_fn [concrete = constants.%bound_method]
 // CHECK:STDOUT:   %Core.FloatLiteral.as.ImplicitAs.impl.Convert.call: init %f64.d77 = call %bound_method.loc15_29.2(%float) [concrete = constants.%float.d15]
 // CHECK:STDOUT:   %.loc15_29.2: init %f64.d77 = converted %float, %Core.FloatLiteral.as.ImplicitAs.impl.Convert.call [concrete = constants.%float.d15]
-// CHECK:STDOUT:   %.loc15_29.3: init %struct_type.a.5e8 = struct_init (%.loc15_29.2) [concrete = constants.%struct.d6a]
+// CHECK:STDOUT:   %.loc15_29.3: init %struct_type.a.5e8 to file.%x.var = struct_init (%.loc15_29.2) [concrete = constants.%struct.d6a]
 // CHECK:STDOUT:   %.loc15_1: init %struct_type.a.5e8 = converted %.loc15_29.1, %.loc15_29.3 [concrete = constants.%struct.d6a]
 // CHECK:STDOUT:   assign file.%x.var, %.loc15_1
 // CHECK:STDOUT:   %x.ref: ref %struct_type.a.5e8 = name_ref x, file.%x [concrete = file.%x.var]
diff --git a/toolchain/check/testdata/struct/fail_non_member_access.carbon b/toolchain/check/testdata/struct/fail_non_member_access.carbon
index e37846104700..a602ac56f661 100644
--- a/toolchain/check/testdata/struct/fail_non_member_access.carbon
+++ b/toolchain/check/testdata/struct/fail_non_member_access.carbon
@@ -104,7 +104,7 @@ var y: i32 = x.b;
 // CHECK:STDOUT:   %bound_method.loc15_27.2: <bound method> = bound_method %int_4, %specific_fn [concrete = constants.%bound_method]
 // CHECK:STDOUT:   %Core.IntLiteral.as.ImplicitAs.impl.Convert.call: init %i32 = call %bound_method.loc15_27.2(%int_4) [concrete = constants.%int_4.940]
 // CHECK:STDOUT:   %.loc15_27.2: init %i32 = converted %int_4, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call [concrete = constants.%int_4.940]
-// CHECK:STDOUT:   %.loc15_27.3: init %struct_type.a.ba9 = struct_init (%.loc15_27.2) [concrete = constants.%struct.a51]
+// CHECK:STDOUT:   %.loc15_27.3: init %struct_type.a.ba9 to file.%x.var = struct_init (%.loc15_27.2) [concrete = constants.%struct.a51]
 // CHECK:STDOUT:   %.loc15_1: init %struct_type.a.ba9 = converted %.loc15_27.1, %.loc15_27.3 [concrete = constants.%struct.a51]
 // CHECK:STDOUT:   assign file.%x.var, %.loc15_1
 // CHECK:STDOUT:   %x.ref: ref %struct_type.a.ba9 = name_ref x, file.%x [concrete = file.%x.var]
diff --git a/toolchain/check/testdata/struct/import.carbon b/toolchain/check/testdata/struct/import.carbon
index 7c4d12be38a1..da0952c98f5e 100644
--- a/toolchain/check/testdata/struct/import.carbon
+++ b/toolchain/check/testdata/struct/import.carbon
@@ -232,7 +232,7 @@ fn F() -> {.x: i32} {
 // CHECK:STDOUT:   %specific_fn.loc5: <specific function> = specific_function %impl.elem0.loc5, @Int.as.Copy.impl.Op(constants.%int_32) [concrete = constants.%Int.as.Copy.impl.Op.specific_fn]
 // CHECK:STDOUT:   %bound_method.loc5_20.2: <bound method> = bound_method %.loc5_20.2, %specific_fn.loc5
 // CHECK:STDOUT:   %Int.as.Copy.impl.Op.call.loc5: init %i32 = call %bound_method.loc5_20.2(%.loc5_20.2)
-// CHECK:STDOUT:   %.loc5_20.3: init %struct_type.a = struct_init (%Int.as.Copy.impl.Op.call.loc5)
+// CHECK:STDOUT:   %.loc5_20.3: init %struct_type.a to file.%a.var = struct_init (%Int.as.Copy.impl.Op.call.loc5)
 // CHECK:STDOUT:   %.loc5_1: init %struct_type.a = converted %a_ref.ref, %.loc5_20.3
 // CHECK:STDOUT:   assign file.%a.var, %.loc5_1
 // CHECK:STDOUT:   %b_ref.ref: ref %struct_type.a.d.9db = name_ref b_ref, imports.%Implicit.b_ref [concrete = imports.%b_ref.var]
@@ -246,7 +246,7 @@ fn F() -> {.x: i32} {
 // CHECK:STDOUT:   %Int.as.Copy.impl.Op.call.loc6_47.1: init %i32 = call %bound_method.loc6_47.2(%.loc6_47.3)
 // CHECK:STDOUT:   %.loc6_47.4: ref %struct_type.b.c = struct_access file.%b.var, element0 [concrete = constants.%.273]
 // CHECK:STDOUT:   %.loc6_47.5: ref %i32 = struct_access %.loc6_47.4, element0 [concrete = constants.%.e4e]
-// CHECK:STDOUT:   %.loc6_47.6: init %i32 to %.loc6_47.5 = initialize_from %Int.as.Copy.impl.Op.call.loc6_47.1
+// CHECK:STDOUT:   %.loc6_47.6: init %i32 to %.loc6_47.5 = in_place_init %Int.as.Copy.impl.Op.call.loc6_47.1
 // CHECK:STDOUT:   %.loc6_47.7: ref %tuple.type.dd4 = struct_access %.loc6_47.1, element1 [concrete = constants.%.d35]
 // CHECK:STDOUT:   %tuple.elem0: ref %i32 = tuple_access %.loc6_47.7, element0 [concrete = constants.%tuple.elem0.4a3]
 // CHECK:STDOUT:   %.loc6_47.8: %i32 = acquire_value %tuple.elem0
@@ -258,7 +258,7 @@ fn F() -> {.x: i32} {
 // CHECK:STDOUT:   %.loc6_47.9: ref %tuple.type.dd4 = struct_access %.loc6_47.4, element1 [concrete = constants.%.de6]
 // CHECK:STDOUT:   %.loc6_47.10: init %tuple.type.dd4 to %.loc6_47.9 = tuple_init (%Int.as.Copy.impl.Op.call.loc6_47.2)
 // CHECK:STDOUT:   %.loc6_47.11: init %tuple.type.dd4 = converted %.loc6_47.7, %.loc6_47.10
-// CHECK:STDOUT:   %.loc6_47.12: init %tuple.type.dd4 to %.loc6_47.9 = initialize_from %.loc6_47.11
+// CHECK:STDOUT:   %.loc6_47.12: init %tuple.type.dd4 to %.loc6_47.9 = in_place_init %.loc6_47.11
 // CHECK:STDOUT:   %.loc6_47.13: init %struct_type.b.c to %.loc6_47.4 = struct_init (%.loc6_47.6, %.loc6_47.12)
 // CHECK:STDOUT:   %.loc6_47.14: init %struct_type.b.c = converted %.loc6_47.1, %.loc6_47.13
 // CHECK:STDOUT:   %.loc6_47.15: ref %i32 = struct_access %b_ref.ref, element1 [concrete = constants.%.7f4]
@@ -269,7 +269,7 @@ fn F() -> {.x: i32} {
 // CHECK:STDOUT:   %bound_method.loc6_47.6: <bound method> = bound_method %.loc6_47.16, %specific_fn.loc6_47.3
 // CHECK:STDOUT:   %Int.as.Copy.impl.Op.call.loc6_47.3: init %i32 = call %bound_method.loc6_47.6(%.loc6_47.16)
 // CHECK:STDOUT:   %.loc6_47.17: ref %i32 = struct_access file.%b.var, element1 [concrete = constants.%.440]
-// CHECK:STDOUT:   %.loc6_47.18: init %i32 to %.loc6_47.17 = initialize_from %Int.as.Copy.impl.Op.call.loc6_47.3
+// CHECK:STDOUT:   %.loc6_47.18: init %i32 to %.loc6_47.17 = in_place_init %Int.as.Copy.impl.Op.call.loc6_47.3
 // CHECK:STDOUT:   %.loc6_47.19: init %struct_type.a.d.9db to file.%b.var = struct_init (%.loc6_47.14, %.loc6_47.18)
 // CHECK:STDOUT:   %.loc6_1: init %struct_type.a.d.9db = converted %b_ref.ref, %.loc6_47.19
 // CHECK:STDOUT:   assign file.%b.var, %.loc6_1
diff --git a/toolchain/check/testdata/struct/member_access.carbon b/toolchain/check/testdata/struct/member_access.carbon
index 83ae27150d8f..3ad25f6aa76c 100644
--- a/toolchain/check/testdata/struct/member_access.carbon
+++ b/toolchain/check/testdata/struct/member_access.carbon
@@ -155,7 +155,7 @@ var z: i32 = y;
 // CHECK:STDOUT:   %Core.FloatLiteral.as.ImplicitAs.impl.Convert.call: init %f64.d77 = call %bound_method.loc15_46.2(%float) [concrete = constants.%float.0a8]
 // CHECK:STDOUT:   %.loc15_46.2: init %f64.d77 = converted %float, %Core.FloatLiteral.as.ImplicitAs.impl.Convert.call [concrete = constants.%float.0a8]
 // CHECK:STDOUT:   %.loc15_46.3: ref %f64.d77 = struct_access file.%x.var, element0 [concrete = constants.%.82d]
-// CHECK:STDOUT:   %.loc15_46.4: init %f64.d77 to %.loc15_46.3 = initialize_from %.loc15_46.2 [concrete = constants.%float.0a8]
+// CHECK:STDOUT:   %.loc15_46.4: init %f64.d77 to %.loc15_46.3 = in_place_init %.loc15_46.2 [concrete = constants.%float.0a8]
 // CHECK:STDOUT:   %impl.elem0.loc15_46.2: %.863 = impl_witness_access constants.%ImplicitAs.impl_witness.6bc, element0 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.0b5]
 // CHECK:STDOUT:   %bound_method.loc15_46.3: <bound method> = bound_method %int_1, %impl.elem0.loc15_46.2 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.bound]
 // CHECK:STDOUT:   %specific_fn.loc15_46.2: <specific function> = specific_function %impl.elem0.loc15_46.2, @Core.IntLiteral.as.ImplicitAs.impl.Convert(constants.%int_32) [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.specific_fn]
@@ -163,7 +163,7 @@ var z: i32 = y;
 // CHECK:STDOUT:   %Core.IntLiteral.as.ImplicitAs.impl.Convert.call: init %i32 = call %bound_method.loc15_46.4(%int_1) [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %.loc15_46.5: init %i32 = converted %int_1, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %.loc15_46.6: ref %i32 = struct_access file.%x.var, element1 [concrete = constants.%.b93]
-// CHECK:STDOUT:   %.loc15_46.7: init %i32 to %.loc15_46.6 = initialize_from %.loc15_46.5 [concrete = constants.%int_1.5d2]
+// CHECK:STDOUT:   %.loc15_46.7: init %i32 to %.loc15_46.6 = in_place_init %.loc15_46.5 [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %.loc15_46.8: init %struct_type.a.b.d2f to file.%x.var = struct_init (%.loc15_46.4, %.loc15_46.7) [concrete = constants.%struct.454]
 // CHECK:STDOUT:   %.loc15_1: init %struct_type.a.b.d2f = converted %.loc15_46.1, %.loc15_46.8 [concrete = constants.%struct.454]
 // CHECK:STDOUT:   assign file.%x.var, %.loc15_1
diff --git a/toolchain/check/testdata/struct/one_entry.carbon b/toolchain/check/testdata/struct/one_entry.carbon
index ea84c9d2b0ea..00fb8861f60c 100644
--- a/toolchain/check/testdata/struct/one_entry.carbon
+++ b/toolchain/check/testdata/struct/one_entry.carbon
@@ -28,6 +28,7 @@ var y: {.a: i32} = x;
 // CHECK:STDOUT:   %int_4.0c1: Core.IntLiteral = int_value 4 [concrete]
 // CHECK:STDOUT:   %struct_type.a.a6c: type = struct_type {.a: Core.IntLiteral} [concrete]
 // CHECK:STDOUT:   %struct.2cb: %struct_type.a.a6c = struct_value (%int_4.0c1) [concrete]
+// CHECK:STDOUT:   %.3cb: ref %i32 = struct_access file.%x.var, element0 [concrete]
 // CHECK:STDOUT:   %ImplicitAs.type.cc7: type = generic_interface_type @ImplicitAs [concrete]
 // CHECK:STDOUT:   %ImplicitAs.generic: %ImplicitAs.type.cc7 = struct_value () [concrete]
 // CHECK:STDOUT:   %ImplicitAs.type.e8c: type = facet_type <@ImplicitAs, @ImplicitAs(%i32)> [concrete]
@@ -45,7 +46,6 @@ var y: {.a: i32} = x;
 // CHECK:STDOUT:   %bound_method: <bound method> = bound_method %int_4.0c1, %Core.IntLiteral.as.ImplicitAs.impl.Convert.specific_fn [concrete]
 // CHECK:STDOUT:   %int_4.940: %i32 = int_value 4 [concrete]
 // CHECK:STDOUT:   %struct.a51: %struct_type.a.ba9 = struct_value (%int_4.940) [concrete]
-// CHECK:STDOUT:   %.3cb: ref %i32 = struct_access file.%x.var, element0 [concrete]
 // CHECK:STDOUT:   %Copy.type: type = facet_type <@Copy> [concrete]
 // CHECK:STDOUT:   %Copy.Op.type: type = fn_type @Copy.Op [concrete]
 // CHECK:STDOUT:   %Int.as.Copy.impl.Op.type.824: type = fn_type @Int.as.Copy.impl.Op, @Int.as.Copy.impl(%N) [symbolic]
@@ -116,7 +116,7 @@ var y: {.a: i32} = x;
 // CHECK:STDOUT:   %bound_method.loc15_27.2: <bound method> = bound_method %int_4, %specific_fn.loc15 [concrete = constants.%bound_method]
 // CHECK:STDOUT:   %Core.IntLiteral.as.ImplicitAs.impl.Convert.call: init %i32 = call %bound_method.loc15_27.2(%int_4) [concrete = constants.%int_4.940]
 // CHECK:STDOUT:   %.loc15_27.2: init %i32 = converted %int_4, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call [concrete = constants.%int_4.940]
-// CHECK:STDOUT:   %.loc15_27.3: init %struct_type.a.ba9 = struct_init (%.loc15_27.2) [concrete = constants.%struct.a51]
+// CHECK:STDOUT:   %.loc15_27.3: init %struct_type.a.ba9 to file.%x.var = struct_init (%.loc15_27.2) [concrete = constants.%struct.a51]
 // CHECK:STDOUT:   %.loc15_1: init %struct_type.a.ba9 = converted %.loc15_27.1, %.loc15_27.3 [concrete = constants.%struct.a51]
 // CHECK:STDOUT:   assign file.%x.var, %.loc15_1
 // CHECK:STDOUT:   %x.ref: ref %struct_type.a.ba9 = name_ref x, file.%x [concrete = file.%x.var]
@@ -127,7 +127,7 @@ var y: {.a: i32} = x;
 // CHECK:STDOUT:   %specific_fn.loc16: <specific function> = specific_function %impl.elem0.loc16, @Int.as.Copy.impl.Op(constants.%int_32) [concrete = constants.%Int.as.Copy.impl.Op.specific_fn]
 // CHECK:STDOUT:   %bound_method.loc16_20.2: <bound method> = bound_method %.loc16_20.2, %specific_fn.loc16
 // CHECK:STDOUT:   %Int.as.Copy.impl.Op.call: init %i32 = call %bound_method.loc16_20.2(%.loc16_20.2)
-// CHECK:STDOUT:   %.loc16_20.3: init %struct_type.a.ba9 = struct_init (%Int.as.Copy.impl.Op.call)
+// CHECK:STDOUT:   %.loc16_20.3: init %struct_type.a.ba9 to file.%y.var = struct_init (%Int.as.Copy.impl.Op.call)
 // CHECK:STDOUT:   %.loc16_1: init %struct_type.a.ba9 = converted %x.ref, %.loc16_20.3
 // CHECK:STDOUT:   assign file.%y.var, %.loc16_1
 // CHECK:STDOUT:   return
diff --git a/toolchain/check/testdata/struct/partially_const.carbon b/toolchain/check/testdata/struct/partially_const.carbon
index e43008801d87..7948ec3e8b92 100644
--- a/toolchain/check/testdata/struct/partially_const.carbon
+++ b/toolchain/check/testdata/struct/partially_const.carbon
@@ -121,14 +121,14 @@ fn Make(n: i32) -> {.a: i32, .b: i32, .c: i32} {
 // CHECK:STDOUT:   %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc16_33.1: init %i32 = call %bound_method.loc16_33.2(%int_0.loc16_16) [concrete = constants.%int_0.6a9]
 // CHECK:STDOUT:   %.loc16_33.2: init %i32 = converted %int_0.loc16_16, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc16_33.1 [concrete = constants.%int_0.6a9]
 // CHECK:STDOUT:   %.loc16_33.3: ref %i32 = struct_access %return.param, element0
-// CHECK:STDOUT:   %.loc16_33.4: init %i32 to %.loc16_33.3 = initialize_from %.loc16_33.2 [concrete = constants.%int_0.6a9]
+// CHECK:STDOUT:   %.loc16_33.4: init %i32 to %.loc16_33.3 = in_place_init %.loc16_33.2 [concrete = constants.%int_0.6a9]
 // CHECK:STDOUT:   %impl.elem0.loc16_24: %.f79 = impl_witness_access constants.%Copy.impl_witness.f17, element0 [concrete = constants.%Int.as.Copy.impl.Op.664]
 // CHECK:STDOUT:   %bound_method.loc16_24.1: <bound method> = bound_method %n.ref, %impl.elem0.loc16_24
 // CHECK:STDOUT:   %specific_fn.loc16_24: <specific function> = specific_function %impl.elem0.loc16_24, @Int.as.Copy.impl.Op(constants.%int_32) [concrete = constants.%Int.as.Copy.impl.Op.specific_fn]
 // CHECK:STDOUT:   %bound_method.loc16_24.2: <bound method> = bound_method %n.ref, %specific_fn.loc16_24
 // CHECK:STDOUT:   %Int.as.Copy.impl.Op.call: init %i32 = call %bound_method.loc16_24.2(%n.ref)
 // CHECK:STDOUT:   %.loc16_33.5: ref %i32 = struct_access %return.param, element1
-// CHECK:STDOUT:   %.loc16_33.6: init %i32 to %.loc16_33.5 = initialize_from %Int.as.Copy.impl.Op.call
+// CHECK:STDOUT:   %.loc16_33.6: init %i32 to %.loc16_33.5 = in_place_init %Int.as.Copy.impl.Op.call
 // CHECK:STDOUT:   %impl.elem0.loc16_33.2: %.863 = impl_witness_access constants.%ImplicitAs.impl_witness.6bc, element0 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.0b5]
 // CHECK:STDOUT:   %bound_method.loc16_33.3: <bound method> = bound_method %int_0.loc16_32, %impl.elem0.loc16_33.2 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.bound]
 // CHECK:STDOUT:   %specific_fn.loc16_33.2: <specific function> = specific_function %impl.elem0.loc16_33.2, @Core.IntLiteral.as.ImplicitAs.impl.Convert(constants.%int_32) [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.specific_fn]
@@ -136,7 +136,7 @@ fn Make(n: i32) -> {.a: i32, .b: i32, .c: i32} {
 // CHECK:STDOUT:   %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc16_33.2: init %i32 = call %bound_method.loc16_33.4(%int_0.loc16_32) [concrete = constants.%int_0.6a9]
 // CHECK:STDOUT:   %.loc16_33.7: init %i32 = converted %int_0.loc16_32, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc16_33.2 [concrete = constants.%int_0.6a9]
 // CHECK:STDOUT:   %.loc16_33.8: ref %i32 = struct_access %return.param, element2
-// CHECK:STDOUT:   %.loc16_33.9: init %i32 to %.loc16_33.8 = initialize_from %.loc16_33.7 [concrete = constants.%int_0.6a9]
+// CHECK:STDOUT:   %.loc16_33.9: init %i32 to %.loc16_33.8 = in_place_init %.loc16_33.7 [concrete = constants.%int_0.6a9]
 // CHECK:STDOUT:   %.loc16_33.10: init %struct_type.a.b.c.0b6 to %return.param = struct_init (%.loc16_33.4, %.loc16_33.6, %.loc16_33.9)
 // CHECK:STDOUT:   %.loc16_34: init %struct_type.a.b.c.0b6 = converted %.loc16_33.1, %.loc16_33.10
 // CHECK:STDOUT:   return %.loc16_34 to %return.param
diff --git a/toolchain/check/testdata/struct/reorder_fields.carbon b/toolchain/check/testdata/struct/reorder_fields.carbon
index c045d4e47d25..2a4ec098e587 100644
--- a/toolchain/check/testdata/struct/reorder_fields.carbon
+++ b/toolchain/check/testdata/struct/reorder_fields.carbon
@@ -180,7 +180,7 @@ fn F() -> {.a: i32, .b: f64} {
 // CHECK:STDOUT:   %bound_method.loc21_10.2: <bound method> = bound_method %.loc21_10.1, %specific_fn.loc21_10.1
 // CHECK:STDOUT:   %Int.as.Copy.impl.Op.call: init %i32 = call %bound_method.loc21_10.2(%.loc21_10.1)
 // CHECK:STDOUT:   %.loc21_10.2: ref %i32 = struct_access %return.param, element1
-// CHECK:STDOUT:   %.loc21_10.3: init %i32 to %.loc21_10.2 = initialize_from %Int.as.Copy.impl.Op.call
+// CHECK:STDOUT:   %.loc21_10.3: init %i32 to %.loc21_10.2 = in_place_init %Int.as.Copy.impl.Op.call
 // CHECK:STDOUT:   %.loc21_10.4: %f64.d77 = struct_access %y.ref, element0
 // CHECK:STDOUT:   %impl.elem0.loc21_10.2: %.c41 = impl_witness_access constants.%Copy.impl_witness.1e3, element0 [concrete = constants.%Float.as.Copy.impl.Op.f05]
 // CHECK:STDOUT:   %bound_method.loc21_10.3: <bound method> = bound_method %.loc21_10.4, %impl.elem0.loc21_10.2
@@ -188,7 +188,7 @@ fn F() -> {.a: i32, .b: f64} {
 // CHECK:STDOUT:   %bound_method.loc21_10.4: <bound method> = bound_method %.loc21_10.4, %specific_fn.loc21_10.2
 // CHECK:STDOUT:   %Float.as.Copy.impl.Op.call: init %f64.d77 = call %bound_method.loc21_10.4(%.loc21_10.4)
 // CHECK:STDOUT:   %.loc21_10.5: ref %f64.d77 = struct_access %return.param, element0
-// CHECK:STDOUT:   %.loc21_10.6: init %f64.d77 to %.loc21_10.5 = initialize_from %Float.as.Copy.impl.Op.call
+// CHECK:STDOUT:   %.loc21_10.6: init %f64.d77 to %.loc21_10.5 = in_place_init %Float.as.Copy.impl.Op.call
 // CHECK:STDOUT:   %.loc21_10.7: init %struct_type.a.b to %return.param = struct_init (%.loc21_10.3, %.loc21_10.6)
 // CHECK:STDOUT:   %.loc21_11: init %struct_type.a.b = converted %y.ref, %.loc21_10.7
 // CHECK:STDOUT:   return %.loc21_11 to %return.param
diff --git a/toolchain/check/testdata/struct/tuple_as_element.carbon b/toolchain/check/testdata/struct/tuple_as_element.carbon
index 73da01fb0ab1..1bf3bbb63751 100644
--- a/toolchain/check/testdata/struct/tuple_as_element.carbon
+++ b/toolchain/check/testdata/struct/tuple_as_element.carbon
@@ -141,7 +141,7 @@ var y: {.a: i32, .b: (i32,)} = x;
 // CHECK:STDOUT:   %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc15_50: init %i32 = call %bound_method.loc15_50.2(%int_1) [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %.loc15_50.2: init %i32 = converted %int_1, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc15_50 [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %.loc15_50.3: ref %i32 = struct_access file.%x.var, element0 [concrete = constants.%.ae3]
-// CHECK:STDOUT:   %.loc15_50.4: init %i32 to %.loc15_50.3 = initialize_from %.loc15_50.2 [concrete = constants.%int_1.5d2]
+// CHECK:STDOUT:   %.loc15_50.4: init %i32 to %.loc15_50.3 = in_place_init %.loc15_50.2 [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %impl.elem0.loc15_49: %.863 = impl_witness_access constants.%ImplicitAs.impl_witness.6bc, element0 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.0b5]
 // CHECK:STDOUT:   %bound_method.loc15_49.1: <bound method> = bound_method %int_2, %impl.elem0.loc15_49 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.bound.4e5]
 // CHECK:STDOUT:   %specific_fn.loc15_49: <specific function> = specific_function %impl.elem0.loc15_49, @Core.IntLiteral.as.ImplicitAs.impl.Convert(constants.%int_32) [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.specific_fn]
@@ -151,7 +151,7 @@ var y: {.a: i32, .b: (i32,)} = x;
 // CHECK:STDOUT:   %.loc15_50.5: ref %tuple.type.a1c = struct_access file.%x.var, element1 [concrete = constants.%.03e]
 // CHECK:STDOUT:   %.loc15_49.3: init %tuple.type.a1c to %.loc15_50.5 = tuple_init (%.loc15_49.2) [concrete = constants.%tuple.092]
 // CHECK:STDOUT:   %.loc15_50.6: init %tuple.type.a1c = converted %.loc15_49.1, %.loc15_49.3 [concrete = constants.%tuple.092]
-// CHECK:STDOUT:   %.loc15_50.7: init %tuple.type.a1c to %.loc15_50.5 = initialize_from %.loc15_50.6 [concrete = constants.%tuple.092]
+// CHECK:STDOUT:   %.loc15_50.7: init %tuple.type.a1c to %.loc15_50.5 = in_place_init %.loc15_50.6 [concrete = constants.%tuple.092]
 // CHECK:STDOUT:   %.loc15_50.8: init %struct_type.a.b.3d5 to file.%x.var = struct_init (%.loc15_50.4, %.loc15_50.7) [concrete = constants.%struct.646]
 // CHECK:STDOUT:   %.loc15_1: init %struct_type.a.b.3d5 = converted %.loc15_50.1, %.loc15_50.8 [concrete = constants.%struct.646]
 // CHECK:STDOUT:   assign file.%x.var, %.loc15_1
@@ -164,7 +164,7 @@ var y: {.a: i32, .b: (i32,)} = x;
 // CHECK:STDOUT:   %bound_method.loc16_32.2: <bound method> = bound_method %.loc16_32.2, %specific_fn.loc16_32.1
 // CHECK:STDOUT:   %Int.as.Copy.impl.Op.call.loc16_32.1: init %i32 = call %bound_method.loc16_32.2(%.loc16_32.2)
 // CHECK:STDOUT:   %.loc16_32.3: ref %i32 = struct_access file.%y.var, element0 [concrete = constants.%.a20]
-// CHECK:STDOUT:   %.loc16_32.4: init %i32 to %.loc16_32.3 = initialize_from %Int.as.Copy.impl.Op.call.loc16_32.1
+// CHECK:STDOUT:   %.loc16_32.4: init %i32 to %.loc16_32.3 = in_place_init %Int.as.Copy.impl.Op.call.loc16_32.1
 // CHECK:STDOUT:   %.loc16_32.5: ref %tuple.type.a1c = struct_access %x.ref, element1 [concrete = constants.%.03e]
 // CHECK:STDOUT:   %tuple.elem0: ref %i32 = tuple_access %.loc16_32.5, element0 [concrete = constants.%tuple.elem0.83d]
 // CHECK:STDOUT:   %.loc16_32.6: %i32 = acquire_value %tuple.elem0
@@ -176,7 +176,7 @@ var y: {.a: i32, .b: (i32,)} = x;
 // CHECK:STDOUT:   %.loc16_32.7: ref %tuple.type.a1c = struct_access file.%y.var, element1 [concrete = constants.%.07f]
 // CHECK:STDOUT:   %.loc16_32.8: init %tuple.type.a1c to %.loc16_32.7 = tuple_init (%Int.as.Copy.impl.Op.call.loc16_32.2)
 // CHECK:STDOUT:   %.loc16_32.9: init %tuple.type.a1c = converted %.loc16_32.5, %.loc16_32.8
-// CHECK:STDOUT:   %.loc16_32.10: init %tuple.type.a1c to %.loc16_32.7 = initialize_from %.loc16_32.9
+// CHECK:STDOUT:   %.loc16_32.10: init %tuple.type.a1c to %.loc16_32.7 = in_place_init %.loc16_32.9
 // CHECK:STDOUT:   %.loc16_32.11: init %struct_type.a.b.3d5 to file.%y.var = struct_init (%.loc16_32.4, %.loc16_32.10)
 // CHECK:STDOUT:   %.loc16_1: init %struct_type.a.b.3d5 = converted %x.ref, %.loc16_32.11
 // CHECK:STDOUT:   assign file.%y.var, %.loc16_1
diff --git a/toolchain/check/testdata/struct/two_entries.carbon b/toolchain/check/testdata/struct/two_entries.carbon
index e81864b266ce..d76253fed285 100644
--- a/toolchain/check/testdata/struct/two_entries.carbon
+++ b/toolchain/check/testdata/struct/two_entries.carbon
@@ -176,7 +176,7 @@ var y: {.a: i32, .b: i32} = x;
 // CHECK:STDOUT:   %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc18_44.1: init %i32 = call %bound_method.loc18_44.2(%int_1.loc18) [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %.loc18_44.2: init %i32 = converted %int_1.loc18, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc18_44.1 [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %.loc18_44.3: ref %i32 = struct_access file.%x.var, element0 [concrete = constants.%.61d]
-// CHECK:STDOUT:   %.loc18_44.4: init %i32 to %.loc18_44.3 = initialize_from %.loc18_44.2 [concrete = constants.%int_1.5d2]
+// CHECK:STDOUT:   %.loc18_44.4: init %i32 to %.loc18_44.3 = in_place_init %.loc18_44.2 [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %impl.elem0.loc18_44.2: %.863 = impl_witness_access constants.%ImplicitAs.impl_witness.6bc, element0 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.0b5]
 // CHECK:STDOUT:   %bound_method.loc18_44.3: <bound method> = bound_method %int_2.loc18, %impl.elem0.loc18_44.2 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.bound.4e5]
 // CHECK:STDOUT:   %specific_fn.loc18_44.2: <specific function> = specific_function %impl.elem0.loc18_44.2, @Core.IntLiteral.as.ImplicitAs.impl.Convert(constants.%int_32) [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.specific_fn]
@@ -184,7 +184,7 @@ var y: {.a: i32, .b: i32} = x;
 // CHECK:STDOUT:   %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc18_44.2: init %i32 = call %bound_method.loc18_44.4(%int_2.loc18) [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %.loc18_44.5: init %i32 = converted %int_2.loc18, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc18_44.2 [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %.loc18_44.6: ref %i32 = struct_access file.%x.var, element1 [concrete = constants.%.fe1]
-// CHECK:STDOUT:   %.loc18_44.7: init %i32 to %.loc18_44.6 = initialize_from %.loc18_44.5 [concrete = constants.%int_2.ef8]
+// CHECK:STDOUT:   %.loc18_44.7: init %i32 to %.loc18_44.6 = in_place_init %.loc18_44.5 [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %.loc18_44.8: init %struct_type.a.b.501 to file.%x.var = struct_init (%.loc18_44.4, %.loc18_44.7) [concrete = constants.%struct.ed5]
 // CHECK:STDOUT:   %.loc18_1: init %struct_type.a.b.501 = converted %.loc18_44.1, %.loc18_44.8 [concrete = constants.%struct.ed5]
 // CHECK:STDOUT:   assign file.%x.var, %.loc18_1
@@ -197,7 +197,7 @@ var y: {.a: i32, .b: i32} = x;
 // CHECK:STDOUT:   %bound_method.loc19_29.2: <bound method> = bound_method %.loc19_29.2, %specific_fn.loc19_29.1
 // CHECK:STDOUT:   %Int.as.Copy.impl.Op.call.loc19_29.1: init %i32 = call %bound_method.loc19_29.2(%.loc19_29.2)
 // CHECK:STDOUT:   %.loc19_29.3: ref %i32 = struct_access file.%y.var, element0 [concrete = constants.%.101]
-// CHECK:STDOUT:   %.loc19_29.4: init %i32 to %.loc19_29.3 = initialize_from %Int.as.Copy.impl.Op.call.loc19_29.1
+// CHECK:STDOUT:   %.loc19_29.4: init %i32 to %.loc19_29.3 = in_place_init %Int.as.Copy.impl.Op.call.loc19_29.1
 // CHECK:STDOUT:   %.loc19_29.5: ref %i32 = struct_access %x.ref, element1 [concrete = constants.%.fe1]
 // CHECK:STDOUT:   %.loc19_29.6: %i32 = acquire_value %.loc19_29.5
 // CHECK:STDOUT:   %impl.elem0.loc19_29.2: %.f79 = impl_witness_access constants.%Copy.impl_witness.f17, element0 [concrete = constants.%Int.as.Copy.impl.Op.664]
@@ -206,7 +206,7 @@ var y: {.a: i32, .b: i32} = x;
 // CHECK:STDOUT:   %bound_method.loc19_29.4: <bound method> = bound_method %.loc19_29.6, %specific_fn.loc19_29.2
 // CHECK:STDOUT:   %Int.as.Copy.impl.Op.call.loc19_29.2: init %i32 = call %bound_method.loc19_29.4(%.loc19_29.6)
 // CHECK:STDOUT:   %.loc19_29.7: ref %i32 = struct_access file.%y.var, element1 [concrete = constants.%.960]
-// CHECK:STDOUT:   %.loc19_29.8: init %i32 to %.loc19_29.7 = initialize_from %Int.as.Copy.impl.Op.call.loc19_29.2
+// CHECK:STDOUT:   %.loc19_29.8: init %i32 to %.loc19_29.7 = in_place_init %Int.as.Copy.impl.Op.call.loc19_29.2
 // CHECK:STDOUT:   %.loc19_29.9: init %struct_type.a.b.501 to file.%y.var = struct_init (%.loc19_29.4, %.loc19_29.8)
 // CHECK:STDOUT:   %.loc19_1: init %struct_type.a.b.501 = converted %x.ref, %.loc19_29.9
 // CHECK:STDOUT:   assign file.%y.var, %.loc19_1
diff --git a/toolchain/check/testdata/tuple/basics.carbon b/toolchain/check/testdata/tuple/basics.carbon
index c50a040bef46..8151b8fc0f19 100644
--- a/toolchain/check/testdata/tuple/basics.carbon
+++ b/toolchain/check/testdata/tuple/basics.carbon
@@ -138,15 +138,15 @@ var y: ((), ()) = x;
 // CHECK:STDOUT:   %.loc4_38.1: %tuple.type.6e8 = tuple_literal (%.loc4_33.1, %.loc4_37.1) [concrete = constants.%tuple.0ca]
 // CHECK:STDOUT:   %tuple.elem0.loc4_38: ref %tuple.type.bcd = tuple_access file.%x.var, element0 [concrete = constants.%tuple.elem0.876]
 // CHECK:STDOUT:   %tuple.elem0.loc4_33: ref %empty_tuple.type = tuple_access %tuple.elem0.loc4_38, element0 [concrete = constants.%tuple.elem0.b2a]
-// CHECK:STDOUT:   %.loc4_28.2: init %empty_tuple.type to %tuple.elem0.loc4_33 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc4_28.2: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc4_33.2: init %empty_tuple.type = converted %.loc4_28.1, %.loc4_28.2 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %tuple.elem1.loc4_33: ref %empty_tuple.type = tuple_access %tuple.elem0.loc4_38, element1 [concrete = constants.%tuple.elem1.894]
-// CHECK:STDOUT:   %.loc4_32.2: init %empty_tuple.type to %tuple.elem1.loc4_33 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc4_32.2: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc4_33.3: init %empty_tuple.type = converted %.loc4_32.1, %.loc4_32.2 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc4_33.4: init %tuple.type.bcd to %tuple.elem0.loc4_38 = tuple_init (%.loc4_33.2, %.loc4_33.3) [concrete = constants.%tuple.d8f]
 // CHECK:STDOUT:   %.loc4_38.2: init %tuple.type.bcd = converted %.loc4_33.1, %.loc4_33.4 [concrete = constants.%tuple.d8f]
 // CHECK:STDOUT:   %tuple.elem1.loc4_38: ref %empty_tuple.type = tuple_access file.%x.var, element1 [concrete = constants.%tuple.elem1.adb]
-// CHECK:STDOUT:   %.loc4_37.2: init %empty_tuple.type to %tuple.elem1.loc4_38 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc4_37.2: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc4_38.3: init %empty_tuple.type = converted %.loc4_37.1, %.loc4_37.2 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc4_38.4: init %tuple.type.6e8 to file.%x.var = tuple_init (%.loc4_38.2, %.loc4_38.3) [concrete = constants.%tuple.0ca]
 // CHECK:STDOUT:   %.loc4_1: init %tuple.type.6e8 = converted %.loc4_38.1, %.loc4_38.4 [concrete = constants.%tuple.0ca]
@@ -162,7 +162,8 @@ var y: ((), ()) = x;
 // CHECK:STDOUT:   %tuple.type: type = tuple_type (%empty_tuple.type) [concrete]
 // CHECK:STDOUT:   %tuple: %tuple.type = tuple_value (%empty_tuple) [concrete]
 // CHECK:STDOUT:   %pattern_type: type = pattern_type %tuple.type [concrete]
-// CHECK:STDOUT:   %tuple.elem0: ref %empty_tuple.type = tuple_access file.%x.var, element0 [concrete]
+// CHECK:STDOUT:   %tuple.elem0.129: ref %empty_tuple.type = tuple_access file.%x.var, element0 [concrete]
+// CHECK:STDOUT:   %tuple.elem0.b49: ref %empty_tuple.type = tuple_access file.%y.var, element0 [concrete]
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: file {
@@ -196,16 +197,18 @@ var y: ((), ()) = x;
 // CHECK:STDOUT: !entry:
 // CHECK:STDOUT:   %.loc4_18.1: %empty_tuple.type = tuple_literal () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc4_20.1: %tuple.type = tuple_literal (%.loc4_18.1) [concrete = constants.%tuple]
+// CHECK:STDOUT:   %tuple.elem0.loc4: ref %empty_tuple.type = tuple_access file.%x.var, element0 [concrete = constants.%tuple.elem0.129]
 // CHECK:STDOUT:   %.loc4_18.2: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc4_20.2: init %empty_tuple.type = converted %.loc4_18.1, %.loc4_18.2 [concrete = constants.%empty_tuple]
-// CHECK:STDOUT:   %.loc4_20.3: init %tuple.type = tuple_init (%.loc4_20.2) [concrete = constants.%tuple]
+// CHECK:STDOUT:   %.loc4_20.3: init %tuple.type to file.%x.var = tuple_init (%.loc4_20.2) [concrete = constants.%tuple]
 // CHECK:STDOUT:   %.loc4_1: init %tuple.type = converted %.loc4_20.1, %.loc4_20.3 [concrete = constants.%tuple]
 // CHECK:STDOUT:   assign file.%x.var, %.loc4_1
 // CHECK:STDOUT:   %x.ref: ref %tuple.type = name_ref x, file.%x [concrete = file.%x.var]
-// CHECK:STDOUT:   %tuple.elem0: ref %empty_tuple.type = tuple_access %x.ref, element0 [concrete = constants.%tuple.elem0]
+// CHECK:STDOUT:   %tuple.elem0.loc5_16.1: ref %empty_tuple.type = tuple_access %x.ref, element0 [concrete = constants.%tuple.elem0.129]
+// CHECK:STDOUT:   %tuple.elem0.loc5_16.2: ref %empty_tuple.type = tuple_access file.%y.var, element0 [concrete = constants.%tuple.elem0.b49]
 // CHECK:STDOUT:   %.loc5_16.1: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
-// CHECK:STDOUT:   %.loc5_16.2: init %empty_tuple.type = converted %tuple.elem0, %.loc5_16.1 [concrete = constants.%empty_tuple]
-// CHECK:STDOUT:   %.loc5_16.3: init %tuple.type = tuple_init (%.loc5_16.2) [concrete = constants.%tuple]
+// CHECK:STDOUT:   %.loc5_16.2: init %empty_tuple.type = converted %tuple.elem0.loc5_16.1, %.loc5_16.1 [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc5_16.3: init %tuple.type to file.%y.var = tuple_init (%.loc5_16.2) [concrete = constants.%tuple]
 // CHECK:STDOUT:   %.loc5_1: init %tuple.type = converted %x.ref, %.loc5_16.3 [concrete = constants.%tuple]
 // CHECK:STDOUT:   assign file.%y.var, %.loc5_1
 // CHECK:STDOUT:   <elided>
@@ -296,10 +299,10 @@ var y: ((), ()) = x;
 // CHECK:STDOUT:   %.loc7_25.1: %empty_tuple.type = tuple_literal () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc7_26.1: %tuple.type = tuple_literal (%.loc7_21.1, %.loc7_25.1) [concrete = constants.%tuple]
 // CHECK:STDOUT:   %tuple.elem0.loc7: ref %empty_tuple.type = tuple_access file.%x.var, element0 [concrete = constants.%tuple.elem0.f07]
-// CHECK:STDOUT:   %.loc7_21.2: init %empty_tuple.type to %tuple.elem0.loc7 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc7_21.2: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc7_26.2: init %empty_tuple.type = converted %.loc7_21.1, %.loc7_21.2 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %tuple.elem1.loc7: ref %empty_tuple.type = tuple_access file.%x.var, element1 [concrete = constants.%tuple.elem1.6f8]
-// CHECK:STDOUT:   %.loc7_25.2: init %empty_tuple.type to %tuple.elem1.loc7 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc7_25.2: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc7_26.3: init %empty_tuple.type = converted %.loc7_25.1, %.loc7_25.2 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc7_26.4: init %tuple.type to file.%x.var = tuple_init (%.loc7_26.2, %.loc7_26.3) [concrete = constants.%tuple]
 // CHECK:STDOUT:   %.loc7_1: init %tuple.type = converted %.loc7_26.1, %.loc7_26.4 [concrete = constants.%tuple]
@@ -307,11 +310,11 @@ var y: ((), ()) = x;
 // CHECK:STDOUT:   %x.ref: ref %tuple.type = name_ref x, file.%x [concrete = file.%x.var]
 // CHECK:STDOUT:   %tuple.elem0.loc8_19.1: ref %empty_tuple.type = tuple_access %x.ref, element0 [concrete = constants.%tuple.elem0.f07]
 // CHECK:STDOUT:   %tuple.elem0.loc8_19.2: ref %empty_tuple.type = tuple_access file.%y.var, element0 [concrete = constants.%tuple.elem0.2e2]
-// CHECK:STDOUT:   %.loc8_19.1: init %empty_tuple.type to %tuple.elem0.loc8_19.2 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc8_19.1: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc8_19.2: init %empty_tuple.type = converted %tuple.elem0.loc8_19.1, %.loc8_19.1 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %tuple.elem1.loc8_19.1: ref %empty_tuple.type = tuple_access %x.ref, element1 [concrete = constants.%tuple.elem1.6f8]
 // CHECK:STDOUT:   %tuple.elem1.loc8_19.2: ref %empty_tuple.type = tuple_access file.%y.var, element1 [concrete = constants.%tuple.elem1.a5b]
-// CHECK:STDOUT:   %.loc8_19.3: init %empty_tuple.type to %tuple.elem1.loc8_19.2 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc8_19.3: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc8_19.4: init %empty_tuple.type = converted %tuple.elem1.loc8_19.1, %.loc8_19.3 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc8_19.5: init %tuple.type to file.%y.var = tuple_init (%.loc8_19.2, %.loc8_19.4) [concrete = constants.%tuple]
 // CHECK:STDOUT:   %.loc8_1: init %tuple.type = converted %x.ref, %.loc8_19.5 [concrete = constants.%tuple]
diff --git a/toolchain/check/testdata/tuple/class_tuples.carbon b/toolchain/check/testdata/tuple/class_tuples.carbon
index 79ef250d7a2d..20526aaf457b 100644
--- a/toolchain/check/testdata/tuple/class_tuples.carbon
+++ b/toolchain/check/testdata/tuple/class_tuples.carbon
@@ -21,17 +21,10 @@ class D {}
 
 var c: C;
 var d: D;
-// CHECK:STDERR: fail_element_type_mismatch.carbon:[[@LINE+14]]:19: error: cannot implicitly convert expression of type `C` to `C*` [ConversionFailure]
+// CHECK:STDERR: fail_element_type_mismatch.carbon:[[@LINE+7]]:19: error: cannot implicitly convert expression of type `C` to `C*` [ConversionFailure]
 // CHECK:STDERR: var x: (C*, C*) = (c, d);
 // CHECK:STDERR:                   ^~~~~~
-// CHECK:STDERR: fail_element_type_mismatch.carbon:[[@LINE+11]]:19: note: type `C` does not implement interface `Core.ImplicitAs(C*)` [MissingImplInMemberAccessNote]
-// CHECK:STDERR: var x: (C*, C*) = (c, d);
-// CHECK:STDERR:                   ^~~~~~
-// CHECK:STDERR:
-// CHECK:STDERR: fail_element_type_mismatch.carbon:[[@LINE+7]]:19: error: cannot implicitly convert expression of type `D` to `C*` [ConversionFailure]
-// CHECK:STDERR: var x: (C*, C*) = (c, d);
-// CHECK:STDERR:                   ^~~~~~
-// CHECK:STDERR: fail_element_type_mismatch.carbon:[[@LINE+4]]:19: note: type `D` does not implement interface `Core.ImplicitAs(C*)` [MissingImplInMemberAccessNote]
+// CHECK:STDERR: fail_element_type_mismatch.carbon:[[@LINE+4]]:19: note: type `C` does not implement interface `Core.ImplicitAs(C*)` [MissingImplInMemberAccessNote]
 // CHECK:STDERR: var x: (C*, C*) = (c, d);
 // CHECK:STDERR:                   ^~~~~~
 // CHECK:STDERR:
diff --git a/toolchain/check/testdata/tuple/element_access.carbon b/toolchain/check/testdata/tuple/element_access.carbon
index 7cf92d73fd0e..58b722cc7a50 100644
--- a/toolchain/check/testdata/tuple/element_access.carbon
+++ b/toolchain/check/testdata/tuple/element_access.carbon
@@ -209,6 +209,7 @@ var b: i32 = a.({.index = 2}.index);
 // CHECK:STDOUT:   %i32: type = class_type @Int, @Int(%int_32) [concrete]
 // CHECK:STDOUT:   %tuple.type.a1c: type = tuple_type (%i32) [concrete]
 // CHECK:STDOUT:   %pattern_type.7ce: type = pattern_type %i32 [concrete]
+// CHECK:STDOUT:   %tuple.elem0.aa1: ref %i32 = tuple_access file.%b.var, element0 [concrete]
 // CHECK:STDOUT:   %Copy.type: type = facet_type <@Copy> [concrete]
 // CHECK:STDOUT:   %Copy.Op.type: type = fn_type @Copy.Op [concrete]
 // CHECK:STDOUT:   %Int.as.Copy.impl.Op.type.824: type = fn_type @Int.as.Copy.impl.Op, @Int.as.Copy.impl(%N) [symbolic]
@@ -220,7 +221,6 @@ var b: i32 = a.({.index = 2}.index);
 // CHECK:STDOUT:   %.f79: type = fn_type_with_self_type %Copy.Op.type, %Copy.facet [concrete]
 // CHECK:STDOUT:   %Int.as.Copy.impl.Op.specific_fn: <specific function> = specific_function %Int.as.Copy.impl.Op.664, @Int.as.Copy.impl.Op(%int_32) [concrete]
 // CHECK:STDOUT:   %int_0: Core.IntLiteral = int_value 0 [concrete]
-// CHECK:STDOUT:   %tuple.elem0.aa1: ref %i32 = tuple_access file.%b.var, element0 [concrete]
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: imports {
diff --git a/toolchain/check/testdata/tuple/import.carbon b/toolchain/check/testdata/tuple/import.carbon
index cb3ac85e97ef..3a99cf750924 100644
--- a/toolchain/check/testdata/tuple/import.carbon
+++ b/toolchain/check/testdata/tuple/import.carbon
@@ -250,7 +250,7 @@ fn F() -> (i32,) {
 // CHECK:STDOUT:   %specific_fn.loc5: <specific function> = specific_function %impl.elem0.loc5, @Int.as.Copy.impl.Op(constants.%int_32) [concrete = constants.%Int.as.Copy.impl.Op.specific_fn]
 // CHECK:STDOUT:   %bound_method.loc5_17.2: <bound method> = bound_method %.loc5_17.1, %specific_fn.loc5
 // CHECK:STDOUT:   %Int.as.Copy.impl.Op.call.loc5: init %i32 = call %bound_method.loc5_17.2(%.loc5_17.1)
-// CHECK:STDOUT:   %.loc5_17.2: init %tuple.type.dd4 = tuple_init (%Int.as.Copy.impl.Op.call.loc5)
+// CHECK:STDOUT:   %.loc5_17.2: init %tuple.type.dd4 to file.%a.var = tuple_init (%Int.as.Copy.impl.Op.call.loc5)
 // CHECK:STDOUT:   %.loc5_1: init %tuple.type.dd4 = converted %a_ref.ref, %.loc5_17.2
 // CHECK:STDOUT:   assign file.%a.var, %.loc5_1
 // CHECK:STDOUT:   %b_ref.ref: ref %tuple.type.cfa = name_ref b_ref, imports.%Implicit.b_ref [concrete = imports.%b_ref.var]
@@ -267,7 +267,7 @@ fn F() -> (i32,) {
 // CHECK:STDOUT:   %tuple.elem0.loc6_38.5: ref %tuple.type.dd4 = tuple_access %tuple.elem0.loc6_38.4, element0 [concrete = constants.%tuple.elem0.021]
 // CHECK:STDOUT:   %.loc6_38.2: init %tuple.type.dd4 to %tuple.elem0.loc6_38.5 = tuple_init (%Int.as.Copy.impl.Op.call.loc6_38.1)
 // CHECK:STDOUT:   %.loc6_38.3: init %tuple.type.dd4 = converted %tuple.elem0.loc6_38.2, %.loc6_38.2
-// CHECK:STDOUT:   %.loc6_38.4: init %tuple.type.dd4 to %tuple.elem0.loc6_38.5 = initialize_from %.loc6_38.3
+// CHECK:STDOUT:   %.loc6_38.4: init %tuple.type.dd4 to %tuple.elem0.loc6_38.5 = in_place_init %.loc6_38.3
 // CHECK:STDOUT:   %tuple.elem1.loc6_38.1: ref %i32 = tuple_access %tuple.elem0.loc6_38.1, element1 [concrete = constants.%tuple.elem1.1c3]
 // CHECK:STDOUT:   %.loc6_38.5: %i32 = acquire_value %tuple.elem1.loc6_38.1
 // CHECK:STDOUT:   %impl.elem0.loc6_38.2: %.70e = impl_witness_access constants.%Copy.impl_witness.a2f, element0 [concrete = constants.%Int.as.Copy.impl.Op.2b1]
@@ -276,7 +276,7 @@ fn F() -> (i32,) {
 // CHECK:STDOUT:   %bound_method.loc6_38.4: <bound method> = bound_method %.loc6_38.5, %specific_fn.loc6_38.2
 // CHECK:STDOUT:   %Int.as.Copy.impl.Op.call.loc6_38.2: init %i32 = call %bound_method.loc6_38.4(%.loc6_38.5)
 // CHECK:STDOUT:   %tuple.elem1.loc6_38.2: ref %i32 = tuple_access %tuple.elem0.loc6_38.4, element1 [concrete = constants.%tuple.elem1.83b]
-// CHECK:STDOUT:   %.loc6_38.6: init %i32 to %tuple.elem1.loc6_38.2 = initialize_from %Int.as.Copy.impl.Op.call.loc6_38.2
+// CHECK:STDOUT:   %.loc6_38.6: init %i32 to %tuple.elem1.loc6_38.2 = in_place_init %Int.as.Copy.impl.Op.call.loc6_38.2
 // CHECK:STDOUT:   %.loc6_38.7: init %tuple.type.154 to %tuple.elem0.loc6_38.4 = tuple_init (%.loc6_38.4, %.loc6_38.6)
 // CHECK:STDOUT:   %.loc6_38.8: init %tuple.type.154 = converted %tuple.elem0.loc6_38.1, %.loc6_38.7
 // CHECK:STDOUT:   %tuple.elem1.loc6_38.3: ref %tuple.type.c2c = tuple_access %b_ref.ref, element1 [concrete = constants.%tuple.elem1.565]
@@ -289,7 +289,7 @@ fn F() -> (i32,) {
 // CHECK:STDOUT:   %Int.as.Copy.impl.Op.call.loc6_38.3: init %i32 = call %bound_method.loc6_38.6(%.loc6_38.9)
 // CHECK:STDOUT:   %tuple.elem1.loc6_38.4: ref %tuple.type.c2c = tuple_access file.%b.var, element1 [concrete = constants.%tuple.elem1.11d]
 // CHECK:STDOUT:   %tuple.elem0.loc6_38.7: ref %i32 = tuple_access %tuple.elem1.loc6_38.4, element0 [concrete = constants.%tuple.elem0.5bc]
-// CHECK:STDOUT:   %.loc6_38.10: init %i32 to %tuple.elem0.loc6_38.7 = initialize_from %Int.as.Copy.impl.Op.call.loc6_38.3
+// CHECK:STDOUT:   %.loc6_38.10: init %i32 to %tuple.elem0.loc6_38.7 = in_place_init %Int.as.Copy.impl.Op.call.loc6_38.3
 // CHECK:STDOUT:   %tuple.elem1.loc6_38.5: ref %i32 = tuple_access %tuple.elem1.loc6_38.3, element1 [concrete = constants.%tuple.elem1.7b5]
 // CHECK:STDOUT:   %.loc6_38.11: %i32 = acquire_value %tuple.elem1.loc6_38.5
 // CHECK:STDOUT:   %impl.elem0.loc6_38.4: %.70e = impl_witness_access constants.%Copy.impl_witness.a2f, element0 [concrete = constants.%Int.as.Copy.impl.Op.2b1]
@@ -298,7 +298,7 @@ fn F() -> (i32,) {
 // CHECK:STDOUT:   %bound_method.loc6_38.8: <bound method> = bound_method %.loc6_38.11, %specific_fn.loc6_38.4
 // CHECK:STDOUT:   %Int.as.Copy.impl.Op.call.loc6_38.4: init %i32 = call %bound_method.loc6_38.8(%.loc6_38.11)
 // CHECK:STDOUT:   %tuple.elem1.loc6_38.6: ref %i32 = tuple_access %tuple.elem1.loc6_38.4, element1 [concrete = constants.%tuple.elem1.240]
-// CHECK:STDOUT:   %.loc6_38.12: init %i32 to %tuple.elem1.loc6_38.6 = initialize_from %Int.as.Copy.impl.Op.call.loc6_38.4
+// CHECK:STDOUT:   %.loc6_38.12: init %i32 to %tuple.elem1.loc6_38.6 = in_place_init %Int.as.Copy.impl.Op.call.loc6_38.4
 // CHECK:STDOUT:   %.loc6_38.13: init %tuple.type.c2c to %tuple.elem1.loc6_38.4 = tuple_init (%.loc6_38.10, %.loc6_38.12)
 // CHECK:STDOUT:   %.loc6_38.14: init %tuple.type.c2c = converted %tuple.elem1.loc6_38.3, %.loc6_38.13
 // CHECK:STDOUT:   %.loc6_38.15: init %tuple.type.cfa to file.%b.var = tuple_init (%.loc6_38.8, %.loc6_38.14)
diff --git a/toolchain/check/testdata/tuple/in_place_tuple_init.carbon b/toolchain/check/testdata/tuple/in_place_tuple_init.carbon
index 4585d4986239..898d4877f52d 100644
--- a/toolchain/check/testdata/tuple/in_place_tuple_init.carbon
+++ b/toolchain/check/testdata/tuple/in_place_tuple_init.carbon
@@ -250,7 +250,7 @@ fn H() {
 // CHECK:STDOUT:   %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc13_50.1: init %i32 = call %bound_method.loc13_50.2(%int_1) [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %.loc13_50.2: init %i32 = converted %int_1, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc13_50.1 [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %tuple.elem0: ref %i32 = tuple_access %v.var, element0
-// CHECK:STDOUT:   %.loc13_50.3: init %i32 to %tuple.elem0 = initialize_from %.loc13_50.2 [concrete = constants.%int_1.5d2]
+// CHECK:STDOUT:   %.loc13_50.3: init %i32 to %tuple.elem0 = in_place_init %.loc13_50.2 [concrete = constants.%int_1.5d2]
 // CHECK:STDOUT:   %impl.elem0.loc13_50.2: %.863 = impl_witness_access constants.%ImplicitAs.impl_witness.6bc, element0 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.0b5]
 // CHECK:STDOUT:   %bound_method.loc13_50.3: <bound method> = bound_method %int_2, %impl.elem0.loc13_50.2 [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.bound.4e5]
 // CHECK:STDOUT:   %specific_fn.loc13_50.2: <specific function> = specific_function %impl.elem0.loc13_50.2, @Core.IntLiteral.as.ImplicitAs.impl.Convert(constants.%int_32) [concrete = constants.%Core.IntLiteral.as.ImplicitAs.impl.Convert.specific_fn]
@@ -258,7 +258,7 @@ fn H() {
 // CHECK:STDOUT:   %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc13_50.2: init %i32 = call %bound_method.loc13_50.4(%int_2) [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %.loc13_50.4: init %i32 = converted %int_2, %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc13_50.2 [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %tuple.elem2: ref %i32 = tuple_access %v.var, element2
-// CHECK:STDOUT:   %.loc13_50.5: init %i32 to %tuple.elem2 = initialize_from %.loc13_50.4 [concrete = constants.%int_2.ef8]
+// CHECK:STDOUT:   %.loc13_50.5: init %i32 to %tuple.elem2 = in_place_init %.loc13_50.4 [concrete = constants.%int_2.ef8]
 // CHECK:STDOUT:   %.loc13_50.6: init %tuple.type.516 to %v.var = tuple_init (%.loc13_50.3, %F.call, %.loc13_50.5)
 // CHECK:STDOUT:   %.loc13_3: init %tuple.type.516 = converted %.loc13_50.1, %.loc13_50.6
 // CHECK:STDOUT:   assign %v.var, %.loc13_3
diff --git a/toolchain/check/testdata/tuple/tuple_pattern.carbon b/toolchain/check/testdata/tuple/tuple_pattern.carbon
index 42a38ace6f13..83ddd7e90d6b 100644
--- a/toolchain/check/testdata/tuple/tuple_pattern.carbon
+++ b/toolchain/check/testdata/tuple/tuple_pattern.carbon
@@ -170,10 +170,10 @@ let (a: {}, b: {}) = ({}, {}, {});
 // CHECK:STDOUT:   %.loc8_30.1: %empty_struct_type = struct_literal () [concrete = constants.%empty_struct]
 // CHECK:STDOUT:   %.loc8_31.1: %tuple.type.b6b = tuple_literal (%.loc8_26.1, %.loc8_30.1) [concrete = constants.%tuple]
 // CHECK:STDOUT:   %tuple.elem0.loc8_31: ref %empty_struct_type = tuple_access %.var.loc8, element0
-// CHECK:STDOUT:   %.loc8_26.2: init %empty_struct_type to %tuple.elem0.loc8_31 = struct_init () [concrete = constants.%empty_struct]
+// CHECK:STDOUT:   %.loc8_26.2: init %empty_struct_type = struct_init () [concrete = constants.%empty_struct]
 // CHECK:STDOUT:   %.loc8_31.2: init %empty_struct_type = converted %.loc8_26.1, %.loc8_26.2 [concrete = constants.%empty_struct]
 // CHECK:STDOUT:   %tuple.elem1.loc8_31: ref %empty_struct_type = tuple_access %.var.loc8, element1
-// CHECK:STDOUT:   %.loc8_30.2: init %empty_struct_type to %tuple.elem1.loc8_31 = struct_init () [concrete = constants.%empty_struct]
+// CHECK:STDOUT:   %.loc8_30.2: init %empty_struct_type = struct_init () [concrete = constants.%empty_struct]
 // CHECK:STDOUT:   %.loc8_31.3: init %empty_struct_type = converted %.loc8_30.1, %.loc8_30.2 [concrete = constants.%empty_struct]
 // CHECK:STDOUT:   %.loc8_31.4: init %tuple.type.b6b to %.var.loc8 = tuple_init (%.loc8_31.2, %.loc8_31.3) [concrete = constants.%tuple]
 // CHECK:STDOUT:   %.loc8_3: init %tuple.type.b6b = converted %.loc8_31.1, %.loc8_31.4 [concrete = constants.%tuple]
@@ -229,10 +229,10 @@ let (a: {}, b: {}) = ({}, {}, {});
 // CHECK:STDOUT:   %.loc6_31.1: %empty_struct_type = struct_literal () [concrete = constants.%empty_struct]
 // CHECK:STDOUT:   %.loc6_32.1: %tuple.type.b6b = tuple_literal (%.loc6_27.1, %.loc6_31.1) [concrete = constants.%tuple]
 // CHECK:STDOUT:   %tuple.elem0.loc6: ref %empty_struct_type = tuple_access %tuple.var, element0
-// CHECK:STDOUT:   %.loc6_27.2: init %empty_struct_type to %tuple.elem0.loc6 = struct_init () [concrete = constants.%empty_struct]
+// CHECK:STDOUT:   %.loc6_27.2: init %empty_struct_type = struct_init () [concrete = constants.%empty_struct]
 // CHECK:STDOUT:   %.loc6_32.2: init %empty_struct_type = converted %.loc6_27.1, %.loc6_27.2 [concrete = constants.%empty_struct]
 // CHECK:STDOUT:   %tuple.elem1.loc6: ref %empty_struct_type = tuple_access %tuple.var, element1
-// CHECK:STDOUT:   %.loc6_31.2: init %empty_struct_type to %tuple.elem1.loc6 = struct_init () [concrete = constants.%empty_struct]
+// CHECK:STDOUT:   %.loc6_31.2: init %empty_struct_type = struct_init () [concrete = constants.%empty_struct]
 // CHECK:STDOUT:   %.loc6_32.3: init %empty_struct_type = converted %.loc6_31.1, %.loc6_31.2 [concrete = constants.%empty_struct]
 // CHECK:STDOUT:   %.loc6_32.4: init %tuple.type.b6b to %tuple.var = tuple_init (%.loc6_32.2, %.loc6_32.3) [concrete = constants.%tuple]
 // CHECK:STDOUT:   %.loc6_3: init %tuple.type.b6b = converted %.loc6_32.1, %.loc6_32.4 [concrete = constants.%tuple]
@@ -256,11 +256,11 @@ let (a: {}, b: {}) = ({}, {}, {});
 // CHECK:STDOUT:   %tuple.ref: ref %tuple.type.b6b = name_ref tuple, %tuple
 // CHECK:STDOUT:   %tuple.elem0.loc7_24.1: ref %empty_struct_type = tuple_access %tuple.ref, element0
 // CHECK:STDOUT:   %tuple.elem0.loc7_24.2: ref %empty_struct_type = tuple_access %.var, element0
-// CHECK:STDOUT:   %.loc7_24.1: init %empty_struct_type to %tuple.elem0.loc7_24.2 = struct_init () [concrete = constants.%empty_struct]
+// CHECK:STDOUT:   %.loc7_24.1: init %empty_struct_type = struct_init () [concrete = constants.%empty_struct]
 // CHECK:STDOUT:   %.loc7_24.2: init %empty_struct_type = converted %tuple.elem0.loc7_24.1, %.loc7_24.1 [concrete = constants.%empty_struct]
 // CHECK:STDOUT:   %tuple.elem1.loc7_24.1: ref %empty_struct_type = tuple_access %tuple.ref, element1
 // CHECK:STDOUT:   %tuple.elem1.loc7_24.2: ref %empty_struct_type = tuple_access %.var, element1
-// CHECK:STDOUT:   %.loc7_24.3: init %empty_struct_type to %tuple.elem1.loc7_24.2 = struct_init () [concrete = constants.%empty_struct]
+// CHECK:STDOUT:   %.loc7_24.3: init %empty_struct_type = struct_init () [concrete = constants.%empty_struct]
 // CHECK:STDOUT:   %.loc7_24.4: init %empty_struct_type = converted %tuple.elem1.loc7_24.1, %.loc7_24.3 [concrete = constants.%empty_struct]
 // CHECK:STDOUT:   %.loc7_24.5: init %tuple.type.b6b to %.var = tuple_init (%.loc7_24.2, %.loc7_24.4) [concrete = constants.%tuple]
 // CHECK:STDOUT:   %.loc7_3: init %tuple.type.b6b = converted %tuple.ref, %.loc7_24.5 [concrete = constants.%tuple]
@@ -319,11 +319,11 @@ let (a: {}, b: {}) = ({}, {}, {});
 // CHECK:STDOUT:   %tuple.ref: %tuple.type.b6b = name_ref tuple, %tuple.loc13_7
 // CHECK:STDOUT:   %tuple.elem0.loc14_24.1: %empty_struct_type = tuple_access %tuple.ref, element0
 // CHECK:STDOUT:   %tuple.elem0.loc14_24.2: ref %empty_struct_type = tuple_access %.var, element0
-// CHECK:STDOUT:   %.loc14_24.1: init %empty_struct_type to %tuple.elem0.loc14_24.2 = struct_init () [concrete = constants.%empty_struct]
+// CHECK:STDOUT:   %.loc14_24.1: init %empty_struct_type = struct_init () [concrete = constants.%empty_struct]
 // CHECK:STDOUT:   %.loc14_24.2: init %empty_struct_type = converted %tuple.elem0.loc14_24.1, %.loc14_24.1 [concrete = constants.%empty_struct]
 // CHECK:STDOUT:   %tuple.elem1.loc14_24.1: %empty_struct_type = tuple_access %tuple.ref, element1
 // CHECK:STDOUT:   %tuple.elem1.loc14_24.2: ref %empty_struct_type = tuple_access %.var, element1
-// CHECK:STDOUT:   %.loc14_24.3: init %empty_struct_type to %tuple.elem1.loc14_24.2 = struct_init () [concrete = constants.%empty_struct]
+// CHECK:STDOUT:   %.loc14_24.3: init %empty_struct_type = struct_init () [concrete = constants.%empty_struct]
 // CHECK:STDOUT:   %.loc14_24.4: init %empty_struct_type = converted %tuple.elem1.loc14_24.1, %.loc14_24.3 [concrete = constants.%empty_struct]
 // CHECK:STDOUT:   %.loc14_24.5: init %tuple.type.b6b to %.var = tuple_init (%.loc14_24.2, %.loc14_24.4) [concrete = constants.%tuple]
 // CHECK:STDOUT:   %.loc14_3: init %tuple.type.b6b = converted %tuple.ref, %.loc14_24.5 [concrete = constants.%tuple]
diff --git a/toolchain/check/testdata/var/global_decl_with_init.carbon b/toolchain/check/testdata/var/global_decl_with_init.carbon
index dfd46d486ca9..0e898138f1a7 100644
--- a/toolchain/check/testdata/var/global_decl_with_init.carbon
+++ b/toolchain/check/testdata/var/global_decl_with_init.carbon
@@ -38,6 +38,7 @@ var (x: (), y: ()) = ((), ());
 // CHECK:STDOUT:   %struct_type.v: type = struct_type {.v: %empty_tuple.type} [concrete]
 // CHECK:STDOUT:   %pattern_type: type = pattern_type %struct_type.v [concrete]
 // CHECK:STDOUT:   %struct: %struct_type.v = struct_value (%empty_tuple) [concrete]
+// CHECK:STDOUT:   %.c0c: ref %empty_tuple.type = struct_access file.%x.var, element0 [concrete]
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: file {
@@ -61,10 +62,11 @@ var (x: (), y: ()) = ((), ());
 // CHECK:STDOUT: !entry:
 // CHECK:STDOUT:   %.loc4_26.1: %empty_tuple.type = tuple_literal () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc4_27.1: %struct_type.v = struct_literal (%.loc4_26.1) [concrete = constants.%struct]
+// CHECK:STDOUT:   %.loc4_27.2: ref %empty_tuple.type = struct_access file.%x.var, element0 [concrete = constants.%.c0c]
 // CHECK:STDOUT:   %.loc4_26.2: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
-// CHECK:STDOUT:   %.loc4_27.2: init %empty_tuple.type = converted %.loc4_26.1, %.loc4_26.2 [concrete = constants.%empty_tuple]
-// CHECK:STDOUT:   %.loc4_27.3: init %struct_type.v = struct_init (%.loc4_27.2) [concrete = constants.%struct]
-// CHECK:STDOUT:   %.loc4_1: init %struct_type.v = converted %.loc4_27.1, %.loc4_27.3 [concrete = constants.%struct]
+// CHECK:STDOUT:   %.loc4_27.3: init %empty_tuple.type = converted %.loc4_26.1, %.loc4_26.2 [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc4_27.4: init %struct_type.v to file.%x.var = struct_init (%.loc4_27.3) [concrete = constants.%struct]
+// CHECK:STDOUT:   %.loc4_1: init %struct_type.v = converted %.loc4_27.1, %.loc4_27.4 [concrete = constants.%struct]
 // CHECK:STDOUT:   assign file.%x.var, %.loc4_1
 // CHECK:STDOUT:   return
 // CHECK:STDOUT: }
@@ -162,10 +164,10 @@ var (x: (), y: ()) = ((), ());
 // CHECK:STDOUT:   %.loc4_28.1: %empty_tuple.type = tuple_literal () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc4_29.1: %tuple.type = tuple_literal (%.loc4_24.1, %.loc4_28.1) [concrete = constants.%tuple]
 // CHECK:STDOUT:   %tuple.elem0: ref %empty_tuple.type = tuple_access file.%.var, element0 [concrete = constants.%tuple.elem0]
-// CHECK:STDOUT:   %.loc4_24.2: init %empty_tuple.type to %tuple.elem0 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc4_24.2: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc4_29.2: init %empty_tuple.type = converted %.loc4_24.1, %.loc4_24.2 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %tuple.elem1: ref %empty_tuple.type = tuple_access file.%.var, element1 [concrete = constants.%tuple.elem1]
-// CHECK:STDOUT:   %.loc4_28.2: init %empty_tuple.type to %tuple.elem1 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc4_28.2: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc4_29.3: init %empty_tuple.type = converted %.loc4_28.1, %.loc4_28.2 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc4_29.4: init %tuple.type to file.%.var = tuple_init (%.loc4_29.2, %.loc4_29.3) [concrete = constants.%tuple]
 // CHECK:STDOUT:   %.loc4_1: init %tuple.type = converted %.loc4_29.1, %.loc4_29.4 [concrete = constants.%tuple]
diff --git a/toolchain/check/testdata/var/global_lookup.carbon b/toolchain/check/testdata/var/global_lookup.carbon
index 0cf11fe3f565..7c06c56bea82 100644
--- a/toolchain/check/testdata/var/global_lookup.carbon
+++ b/toolchain/check/testdata/var/global_lookup.carbon
@@ -24,6 +24,7 @@ var y: {.v: ()} = x;
 // CHECK:STDOUT:   %pattern_type: type = pattern_type %struct_type.v [concrete]
 // CHECK:STDOUT:   %struct: %struct_type.v = struct_value (%empty_tuple) [concrete]
 // CHECK:STDOUT:   %.c0c: ref %empty_tuple.type = struct_access file.%x.var, element0 [concrete]
+// CHECK:STDOUT:   %.ff0: ref %empty_tuple.type = struct_access file.%y.var, element0 [concrete]
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: file {
@@ -59,17 +60,19 @@ var y: {.v: ()} = x;
 // CHECK:STDOUT: !entry:
 // CHECK:STDOUT:   %.loc15_26.1: %empty_tuple.type = tuple_literal () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc15_27.1: %struct_type.v = struct_literal (%.loc15_26.1) [concrete = constants.%struct]
+// CHECK:STDOUT:   %.loc15_27.2: ref %empty_tuple.type = struct_access file.%x.var, element0 [concrete = constants.%.c0c]
 // CHECK:STDOUT:   %.loc15_26.2: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
-// CHECK:STDOUT:   %.loc15_27.2: init %empty_tuple.type = converted %.loc15_26.1, %.loc15_26.2 [concrete = constants.%empty_tuple]
-// CHECK:STDOUT:   %.loc15_27.3: init %struct_type.v = struct_init (%.loc15_27.2) [concrete = constants.%struct]
-// CHECK:STDOUT:   %.loc15_1: init %struct_type.v = converted %.loc15_27.1, %.loc15_27.3 [concrete = constants.%struct]
+// CHECK:STDOUT:   %.loc15_27.3: init %empty_tuple.type = converted %.loc15_26.1, %.loc15_26.2 [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc15_27.4: init %struct_type.v to file.%x.var = struct_init (%.loc15_27.3) [concrete = constants.%struct]
+// CHECK:STDOUT:   %.loc15_1: init %struct_type.v = converted %.loc15_27.1, %.loc15_27.4 [concrete = constants.%struct]
 // CHECK:STDOUT:   assign file.%x.var, %.loc15_1
 // CHECK:STDOUT:   %x.ref: ref %struct_type.v = name_ref x, file.%x [concrete = file.%x.var]
 // CHECK:STDOUT:   %.loc16_19.1: ref %empty_tuple.type = struct_access %x.ref, element0 [concrete = constants.%.c0c]
-// CHECK:STDOUT:   %.loc16_19.2: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
-// CHECK:STDOUT:   %.loc16_19.3: init %empty_tuple.type = converted %.loc16_19.1, %.loc16_19.2 [concrete = constants.%empty_tuple]
-// CHECK:STDOUT:   %.loc16_19.4: init %struct_type.v = struct_init (%.loc16_19.3) [concrete = constants.%struct]
-// CHECK:STDOUT:   %.loc16_1: init %struct_type.v = converted %x.ref, %.loc16_19.4 [concrete = constants.%struct]
+// CHECK:STDOUT:   %.loc16_19.2: ref %empty_tuple.type = struct_access file.%y.var, element0 [concrete = constants.%.ff0]
+// CHECK:STDOUT:   %.loc16_19.3: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc16_19.4: init %empty_tuple.type = converted %.loc16_19.1, %.loc16_19.3 [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc16_19.5: init %struct_type.v to file.%y.var = struct_init (%.loc16_19.4) [concrete = constants.%struct]
+// CHECK:STDOUT:   %.loc16_1: init %struct_type.v = converted %x.ref, %.loc16_19.5 [concrete = constants.%struct]
 // CHECK:STDOUT:   assign file.%y.var, %.loc16_1
 // CHECK:STDOUT:   return
 // CHECK:STDOUT: }
diff --git a/toolchain/check/testdata/var/global_lookup_in_scope.carbon b/toolchain/check/testdata/var/global_lookup_in_scope.carbon
index ef54ba7e45ce..66b8b38a04cf 100644
--- a/toolchain/check/testdata/var/global_lookup_in_scope.carbon
+++ b/toolchain/check/testdata/var/global_lookup_in_scope.carbon
@@ -28,9 +28,9 @@ fn Main() {
 // CHECK:STDOUT:   %struct_type.v: type = struct_type {.v: %empty_tuple.type} [concrete]
 // CHECK:STDOUT:   %pattern_type.c4c: type = pattern_type %struct_type.v [concrete]
 // CHECK:STDOUT:   %struct: %struct_type.v = struct_value (%empty_tuple) [concrete]
+// CHECK:STDOUT:   %.c0c: ref %empty_tuple.type = struct_access file.%x.var, element0 [concrete]
 // CHECK:STDOUT:   %Main.type: type = fn_type @Main [concrete]
 // CHECK:STDOUT:   %Main: %Main.type = struct_value () [concrete]
-// CHECK:STDOUT:   %.c0c: ref %empty_tuple.type = struct_access file.%x.var, element0 [concrete]
 // CHECK:STDOUT:   %Destroy.type: type = facet_type <@Destroy> [concrete]
 // CHECK:STDOUT:   %DestroyOp.type: type = fn_type @DestroyOp [concrete]
 // CHECK:STDOUT:   %DestroyOp: %DestroyOp.type = struct_value () [concrete]
@@ -75,10 +75,11 @@ fn Main() {
 // CHECK:STDOUT:   %y.var: ref %struct_type.v = var %y.var_patt
 // CHECK:STDOUT:   %x.ref: ref %struct_type.v = name_ref x, file.%x [concrete = file.%x.var]
 // CHECK:STDOUT:   %.loc5_21.1: ref %empty_tuple.type = struct_access %x.ref, element0 [concrete = constants.%.c0c]
-// CHECK:STDOUT:   %.loc5_21.2: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
-// CHECK:STDOUT:   %.loc5_21.3: init %empty_tuple.type = converted %.loc5_21.1, %.loc5_21.2 [concrete = constants.%empty_tuple]
-// CHECK:STDOUT:   %.loc5_21.4: init %struct_type.v = struct_init (%.loc5_21.3) [concrete = constants.%struct]
-// CHECK:STDOUT:   %.loc5_3: init %struct_type.v = converted %x.ref, %.loc5_21.4 [concrete = constants.%struct]
+// CHECK:STDOUT:   %.loc5_21.2: ref %empty_tuple.type = struct_access %y.var, element0
+// CHECK:STDOUT:   %.loc5_21.3: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc5_21.4: init %empty_tuple.type = converted %.loc5_21.1, %.loc5_21.3 [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc5_21.5: init %struct_type.v to %y.var = struct_init (%.loc5_21.4) [concrete = constants.%struct]
+// CHECK:STDOUT:   %.loc5_3: init %struct_type.v = converted %x.ref, %.loc5_21.5 [concrete = constants.%struct]
 // CHECK:STDOUT:   assign %y.var, %.loc5_3
 // CHECK:STDOUT:   %.loc5_17: type = splice_block %struct_type.v [concrete = constants.%struct_type.v] {
 // CHECK:STDOUT:     %.loc5_16.1: %empty_tuple.type = tuple_literal () [concrete = constants.%empty_tuple]
@@ -97,10 +98,11 @@ fn Main() {
 // CHECK:STDOUT: !entry:
 // CHECK:STDOUT:   %.loc2_26.1: %empty_tuple.type = tuple_literal () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc2_27.1: %struct_type.v = struct_literal (%.loc2_26.1) [concrete = constants.%struct]
+// CHECK:STDOUT:   %.loc2_27.2: ref %empty_tuple.type = struct_access file.%x.var, element0 [concrete = constants.%.c0c]
 // CHECK:STDOUT:   %.loc2_26.2: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
-// CHECK:STDOUT:   %.loc2_27.2: init %empty_tuple.type = converted %.loc2_26.1, %.loc2_26.2 [concrete = constants.%empty_tuple]
-// CHECK:STDOUT:   %.loc2_27.3: init %struct_type.v = struct_init (%.loc2_27.2) [concrete = constants.%struct]
-// CHECK:STDOUT:   %.loc2_1: init %struct_type.v = converted %.loc2_27.1, %.loc2_27.3 [concrete = constants.%struct]
+// CHECK:STDOUT:   %.loc2_27.3: init %empty_tuple.type = converted %.loc2_26.1, %.loc2_26.2 [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc2_27.4: init %struct_type.v to file.%x.var = struct_init (%.loc2_27.3) [concrete = constants.%struct]
+// CHECK:STDOUT:   %.loc2_1: init %struct_type.v = converted %.loc2_27.1, %.loc2_27.4 [concrete = constants.%struct]
 // CHECK:STDOUT:   assign file.%x.var, %.loc2_1
 // CHECK:STDOUT:   return
 // CHECK:STDOUT: }
diff --git a/toolchain/check/testdata/var/var_pattern.carbon b/toolchain/check/testdata/var/var_pattern.carbon
index 6bbf9a2860c4..94467a5de379 100644
--- a/toolchain/check/testdata/var/var_pattern.carbon
+++ b/toolchain/check/testdata/var/var_pattern.carbon
@@ -314,10 +314,10 @@ fn G() {
 // CHECK:STDOUT:   %.loc5_30.1: %empty_tuple.type = tuple_literal () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc5_31.1: %tuple.type = tuple_literal (%.loc5_26.1, %.loc5_30.1) [concrete = constants.%tuple]
 // CHECK:STDOUT:   %tuple.elem0.loc5_31: ref %empty_tuple.type = tuple_access %.var, element0
-// CHECK:STDOUT:   %.loc5_26.2: init %empty_tuple.type to %tuple.elem0.loc5_31 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc5_26.2: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc5_31.2: init %empty_tuple.type = converted %.loc5_26.1, %.loc5_26.2 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %tuple.elem1.loc5_31: ref %empty_tuple.type = tuple_access %.var, element1
-// CHECK:STDOUT:   %.loc5_30.2: init %empty_tuple.type to %tuple.elem1.loc5_31 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc5_30.2: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc5_31.3: init %empty_tuple.type = converted %.loc5_30.1, %.loc5_30.2 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc5_31.4: init %tuple.type to %.var = tuple_init (%.loc5_31.2, %.loc5_31.3) [concrete = constants.%tuple]
 // CHECK:STDOUT:   %.loc5_3: init %tuple.type = converted %.loc5_31.1, %.loc5_31.4 [concrete = constants.%tuple]
@@ -388,10 +388,10 @@ fn G() {
 // CHECK:STDOUT:   %.loc5_34.1: %empty_tuple.type = tuple_literal () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc5_35.1: %tuple.type = tuple_literal (%.loc5_30.1, %.loc5_34.1) [concrete = constants.%tuple]
 // CHECK:STDOUT:   %tuple.elem0.loc5_35: ref %empty_tuple.type = tuple_access %.var, element0
-// CHECK:STDOUT:   %.loc5_30.2: init %empty_tuple.type to %tuple.elem0.loc5_35 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc5_30.2: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc5_35.2: init %empty_tuple.type = converted %.loc5_30.1, %.loc5_30.2 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %tuple.elem1.loc5_35: ref %empty_tuple.type = tuple_access %.var, element1
-// CHECK:STDOUT:   %.loc5_34.2: init %empty_tuple.type to %tuple.elem1.loc5_35 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc5_34.2: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc5_35.3: init %empty_tuple.type = converted %.loc5_34.1, %.loc5_34.2 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc5_35.4: init %tuple.type to %.var = tuple_init (%.loc5_35.2, %.loc5_35.3) [concrete = constants.%tuple]
 // CHECK:STDOUT:   %.loc5_7: init %tuple.type = converted %.loc5_35.1, %.loc5_35.4 [concrete = constants.%tuple]
@@ -742,10 +742,10 @@ fn G() {
 // CHECK:STDOUT:   %.loc9_43.2: %empty_tuple.type = converted %.loc9_43.1, %empty_tuple [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %x: %empty_tuple.type = value_binding x, %.loc9_43.2
 // CHECK:STDOUT:   %tuple.elem0.loc9_53: ref %empty_tuple.type = tuple_access %.var, element0
-// CHECK:STDOUT:   %.loc9_48.2: init %empty_tuple.type to %tuple.elem0.loc9_53 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc9_48.2: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc9_53.2: init %empty_tuple.type = converted %.loc9_48.1, %.loc9_48.2 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %tuple.elem1.loc9_53: ref %empty_tuple.type = tuple_access %.var, element1
-// CHECK:STDOUT:   %.loc9_52.2: init %empty_tuple.type to %tuple.elem1.loc9_53 = tuple_init () [concrete = constants.%empty_tuple]
+// CHECK:STDOUT:   %.loc9_52.2: init %empty_tuple.type = tuple_init () [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc9_53.3: init %empty_tuple.type = converted %.loc9_52.1, %.loc9_52.2 [concrete = constants.%empty_tuple]
 // CHECK:STDOUT:   %.loc9_53.4: init %tuple.type.bcd to %.var = tuple_init (%.loc9_53.2, %.loc9_53.3) [concrete = constants.%tuple.d8f]
 // CHECK:STDOUT:   %.loc9_15.1: init %tuple.type.bcd = converted %.loc9_53.1, %.loc9_53.4 [concrete = constants.%tuple.d8f]
diff --git a/toolchain/docs/check/README.md b/toolchain/docs/check/README.md
index b424e3a45959..df9f80d35f34 100644
--- a/toolchain/docs/check/README.md
+++ b/toolchain/docs/check/README.md
@@ -299,6 +299,17 @@ after the `ir_name` -- in this example the `name_id` is `N`. From this we find
 that the instruction corresponds to an associated constant declaration in an
 interface like `let N:! i32;`.
 
+In fact, the notation after the `:` records not just the instruction's type, but
+also some information about its category, and the storage argument if it's an
+initializer:
+
+-   `%N: i32 = ...`: a value expression of type `i32`.
+-   `%N: init i32 = ...`: an initializing expression of type `i32` with no
+    storage argument.
+-   `%N: init i32 to %s = ...`: an initializing expression of type `i32` that
+    uses `%s` as its backing storage if needed.
+-   `%N: ref i32 = ...`: a reference of type `i32`.
+
 Instructions producing a constant value, like `assoc_const_decl` above, are
 followed by their phase, either `[symbolic]` or `[template]`, and then `=` the
 value if it is the value of a different instruction.
@@ -339,6 +350,14 @@ formatter will combine instructions together to make the IR more readable:
     followed by a `StructType` instruction, is collapsed into a single
     `struct_type{.field1: %value1, ..., .fieldN: %valueN}` line.
 
+As noted above, initializer storage arguments are formatted with `... to %arg`
+in the type position. To parallel that, the destination argument of a `return`
+instruction is also formatted with `to`. For example:
+
+```
+return %N to %return.param
+```
+
 These exceptions may be found in
 [toolchain/sem_ir/formatter.cpp](/toolchain/sem_ir/formatter.cpp).
 
diff --git a/toolchain/lower/aggregate.cpp b/toolchain/lower/aggregate.cpp
index f592d52eb9ce..d65d8eb277b9 100644
--- a/toolchain/lower/aggregate.cpp
+++ b/toolchain/lower/aggregate.cpp
@@ -40,6 +40,9 @@ static auto GetElementIndex(FunctionContext::TypeInFile type,
   return idx.index;
 }
 
+// Extracts an element of an aggregate, such as a struct, tuple, or class, by
+// index. Depending on the expression category and value representation of the
+// aggregate input, this will either produce a value or a reference.
 auto GetAggregateElement(FunctionContext& context, SemIR::InstId aggr_inst_id,
                          SemIR::ElementIndex idx, SemIR::InstId result_inst_id,
                          llvm::Twine name) -> llvm::Value* {
@@ -50,7 +53,8 @@ auto GetAggregateElement(FunctionContext& context, SemIR::InstId aggr_inst_id,
     case SemIR::ExprCategory::Error:
     case SemIR::ExprCategory::NotExpr:
     case SemIR::ExprCategory::Pattern:
-    case SemIR::ExprCategory::Initializing:
+    case SemIR::ExprCategory::ReprInitializing:
+    case SemIR::ExprCategory::InPlaceInitializing:
     case SemIR::ExprCategory::Mixed:
       CARBON_FATAL(
           "Unexpected expression category for aggregate access into {0}",
@@ -194,10 +198,10 @@ auto EmitAggregateInitializer(FunctionContext& context,
       for (auto [i, ref_id] : llvm::enumerate(refs)) {
         if (context.sem_ir().constant_values().Get(ref_id).is_constant()) {
           auto dest_id =
-              SemIR::FindReturnSlotArgForInitializer(context.sem_ir(), ref_id);
+              SemIR::FindStorageArgForInitializer(context.sem_ir(), ref_id);
           auto src_id = ref_id;
           auto storage_type = context.GetTypeIdOfInst(dest_id);
-          context.FinishInit(storage_type, dest_id, src_id);
+          context.InitializeStorage(storage_type, dest_id, src_id);
         }
       }
       // TODO: Add a helper to poison a value slot.
diff --git a/toolchain/lower/file_context.cpp b/toolchain/lower/file_context.cpp
index c244226d4cef..f6ace4be4f45 100644
--- a/toolchain/lower/file_context.cpp
+++ b/toolchain/lower/file_context.cpp
@@ -181,7 +181,8 @@ auto FileContext::GetConstant(SemIR::ConstantId const_id,
   // initializing expressions, `FinishInit` will perform a copy if needed.
   switch (auto cat = SemIR::GetExprCategory(sem_ir(), const_inst_id)) {
     case SemIR::ExprCategory::Value:
-    case SemIR::ExprCategory::Initializing:
+    case SemIR::ExprCategory::ReprInitializing:
+    case SemIR::ExprCategory::InPlaceInitializing:
       break;
 
     case SemIR::ExprCategory::DurableRef:
diff --git a/toolchain/lower/function_context.cpp b/toolchain/lower/function_context.cpp
index 628b76d95f45..9ebc44ac6722 100644
--- a/toolchain/lower/function_context.cpp
+++ b/toolchain/lower/function_context.cpp
@@ -266,8 +266,8 @@ auto FunctionContext::GetDebugLoc(SemIR::InstId inst_id) -> llvm::DebugLoc {
                                loc.column_number, di_subprogram_);
 }
 
-auto FunctionContext::FinishInit(TypeInFile type, SemIR::InstId dest_id,
-                                 SemIR::InstId source_id) -> void {
+auto FunctionContext::InitializeStorage(TypeInFile type, SemIR::InstId dest_id,
+                                        SemIR::InstId source_id) -> void {
   switch (GetInitRepr(type).kind) {
     case SemIR::InitRepr::None:
       break;
diff --git a/toolchain/lower/function_context.h b/toolchain/lower/function_context.h
index 23cb8ad2e3b5..38d4f1b63e86 100644
--- a/toolchain/lower/function_context.h
+++ b/toolchain/lower/function_context.h
@@ -178,12 +178,13 @@ class FunctionContext {
   auto StoreObject(TypeInFile type, llvm::Value* value, llvm::Value* addr)
       -> void;
 
-  // After emitting an initializer `init_id`, finishes performing the
-  // initialization of `dest_id` from that initializer. This is a no-op if the
-  // initialization was performed in-place, and otherwise performs a store or a
-  // copy.
-  auto FinishInit(TypeInFile type, SemIR::InstId dest_id,
-                  SemIR::InstId source_id) -> void;
+  // Emits the instructions necessary to initialize the storage at `dest_id`
+  // from the repr-initializing expression `source_id`. This assumes the
+  // instructions for `source_id` have already been emitted, so it's a no-op if
+  // the initialization was performed in-place, and otherwise performs a store
+  // or a copy.
+  auto InitializeStorage(TypeInFile type, SemIR::InstId dest_id,
+                         SemIR::InstId source_id) -> void;
 
   // When fingerprinting for a specific, adds the call, found in the function
   // body, to <function_id, specific_id>. `function_id` and `specific_id` are
diff --git a/toolchain/lower/handle.cpp b/toolchain/lower/handle.cpp
index 3d7331ccdde1..fbced2f83a22 100644
--- a/toolchain/lower/handle.cpp
+++ b/toolchain/lower/handle.cpp
@@ -13,6 +13,7 @@
 #include "llvm/Support/Casting.h"
 #include "toolchain/lower/function_context.h"
 #include "toolchain/sem_ir/builtin_function_kind.h"
+#include "toolchain/sem_ir/expr_info.h"
 #include "toolchain/sem_ir/function.h"
 #include "toolchain/sem_ir/inst.h"
 #include "toolchain/sem_ir/typed_insts.h"
@@ -78,8 +79,11 @@ auto HandleInst(FunctionContext& context, SemIR::InstId inst_id,
 
 auto HandleInst(FunctionContext& context, SemIR::InstId /*inst_id*/,
                 SemIR::Assign inst) -> void {
-  context.FinishInit(context.GetTypeIdOfInst(inst.lhs_id), inst.lhs_id,
-                     inst.rhs_id);
+  if (SemIR::GetExprCategory(context.sem_ir(), inst.rhs_id) !=
+      SemIR::ExprCategory::InPlaceInitializing) {
+    context.InitializeStorage(context.GetTypeIdOfInst(inst.lhs_id), inst.lhs_id,
+                              inst.rhs_id);
+  }
 }
 
 auto HandleInst(FunctionContext& context, SemIR::InstId inst_id,
@@ -199,9 +203,9 @@ auto HandleInst(FunctionContext& context, SemIR::InstId inst_id,
 }
 
 auto HandleInst(FunctionContext& context, SemIR::InstId /*inst_id*/,
-                SemIR::InitializeFrom inst) -> void {
-  context.FinishInit(context.GetTypeIdOfInst(inst.dest_id), inst.dest_id,
-                     inst.src_id);
+                SemIR::InPlaceInit inst) -> void {
+  context.InitializeStorage(context.GetTypeIdOfInst(inst.dest_id), inst.dest_id,
+                            inst.src_id);
 }
 
 auto HandleInst(FunctionContext& /*context*/, SemIR::InstId /*inst_id*/,
@@ -264,13 +268,36 @@ auto HandleInst(FunctionContext& context, SemIR::InstId /*inst_id*/,
       context.builder().CreateRetVoid();
       return;
     case SemIR::InitRepr::InPlace:
-      context.FinishInit(result_type, inst.dest_id, inst.expr_id);
+      CARBON_CHECK(context.GetValueRepr(result_type).repr.kind ==
+                       SemIR::ValueRepr::Pointer,
+                   "TODO: Add support for ReturnExpr with custom value repr");
+      // TODO: find a way to avoid the redundant call to GetInitRepr inside
+      // InitializeStorage.
+      context.InitializeStorage(result_type, inst.dest_id, inst.expr_id);
       context.builder().CreateRetVoid();
       return;
-    case SemIR::InitRepr::ByCopy:
-      // The expression produces the value representation for the type.
-      context.builder().CreateRet(context.GetValue(inst.expr_id));
+    case SemIR::InitRepr::ByCopy: {
+      auto* value = context.GetValue(inst.expr_id);
+      switch (SemIR::GetExprCategory(context.sem_ir(), inst.expr_id)) {
+        case SemIR::ExprCategory::Value:
+        case SemIR::ExprCategory::ReprInitializing:
+        case SemIR::ExprCategory::EphemeralRef:
+        case SemIR::ExprCategory::DurableRef:
+          break;
+        case SemIR::ExprCategory::InPlaceInitializing:
+          value =
+              context.builder().CreateLoad(context.GetType(result_type), value);
+          break;
+        case SemIR::ExprCategory::Mixed:
+        case SemIR::ExprCategory::RefTagged:
+        case SemIR::ExprCategory::NotExpr:
+        case SemIR::ExprCategory::Error:
+        case SemIR::ExprCategory::Pattern:
+          CARBON_FATAL("Unexpected category for `return` expression");
+      }
+      context.builder().CreateRet(value);
       return;
+    }
     case SemIR::InitRepr::Abstract:
       CARBON_FATAL("Lowering return of abstract type {0}",
                    result_type.file->types().GetAsInst(result_type.type_id));
diff --git a/toolchain/lower/handle_expr_category.cpp b/toolchain/lower/handle_expr_category.cpp
index 4de7578cfcc4..37e32bb5fc3c 100644
--- a/toolchain/lower/handle_expr_category.cpp
+++ b/toolchain/lower/handle_expr_category.cpp
@@ -39,49 +39,17 @@ auto HandleInst(FunctionContext& context, SemIR::InstId inst_id,
 }
 
 auto HandleInst(FunctionContext& context, SemIR::InstId inst_id,
-                SemIR::InPlaceInit inst) -> void {
-  auto type = context.GetTypeIdOfInst(inst_id);
-  auto* value = context.GetValue(inst.dest_id);
-
-  // If the initializing representation is by-value, and the value
-  // representation is by-copy, then we need to load from the storage. Otherwise
-  // we want a pointer to the result.
-  switch (context.GetInitRepr(type).kind) {
-    case SemIR::InitRepr::None:
-    case SemIR::InitRepr::InPlace:
-      break;
-    case SemIR::InitRepr::ByCopy:
-      switch (context.GetValueRepr(type).repr.kind) {
-        case SemIR::ValueRepr::Unknown:
-          CARBON_FATAL("Unexpected incomplete type");
-        case SemIR::ValueRepr::Dependent:
-          CARBON_FATAL("Unexpected dependent type");
-        case SemIR::ValueRepr::None:
-        case SemIR::ValueRepr::Pointer:
-          break;
-        case SemIR::ValueRepr::Copy:
-          value = context.builder().CreateLoad(context.GetType(type), value);
-          break;
-        case SemIR::ValueRepr::Custom:
-          CARBON_FATAL(
-              "TODO: Add support for InPlaceInit with custom value rep");
-      }
-      break;
-    case SemIR::InitRepr::Abstract:
-      CARBON_FATAL("Unexpected abstract type");
-    case SemIR::InitRepr::Incomplete:
-      CARBON_FATAL("Unexpected incomplete type");
-    case SemIR::InitRepr::Dependent:
-      CARBON_FATAL("Unexpected dependent type");
-  }
-
-  context.SetLocal(inst_id, value);
+                SemIR::MarkInPlaceInit inst) -> void {
+  context.SetLocal(inst_id, context.GetValue(inst.dest_id));
 }
 
 auto HandleInst(FunctionContext& context, SemIR::InstId inst_id,
                 SemIR::Temporary inst) -> void {
-  context.FinishInit(context.GetTypeIdOfInst(inst_id), inst.storage_id,
-                     inst.init_id);
+  if (SemIR::GetExprCategory(context.sem_ir(), inst.init_id) !=
+      SemIR::ExprCategory::InPlaceInitializing) {
+    context.InitializeStorage(context.GetTypeIdOfInst(inst_id), inst.storage_id,
+                              inst.init_id);
+  }
   context.SetLocal(inst_id, context.GetValue(inst.storage_id));
 }
 
@@ -104,7 +72,7 @@ auto HandleInst(FunctionContext& context, SemIR::InstId inst_id,
 auto HandleInst(FunctionContext& context, SemIR::InstId inst_id,
                 SemIR::ValueOfInitializer inst) -> void {
   CARBON_CHECK(SemIR::GetExprCategory(context.sem_ir(), inst.init_id) ==
-               SemIR::ExprCategory::Initializing);
+               SemIR::ExprCategory::ReprInitializing);
   auto inst_type = context.GetTypeIdOfInst(inst_id);
   auto value_repr = context.GetValueRepr(inst_type);
   auto init_repr = context.GetInitRepr(inst_type);
diff --git a/toolchain/lower/testdata/interop/cpp/nullptr.carbon b/toolchain/lower/testdata/interop/cpp/nullptr.carbon
index 58fca65fa66a..f18315d418b4 100644
--- a/toolchain/lower/testdata/interop/cpp/nullptr.carbon
+++ b/toolchain/lower/testdata/interop/cpp/nullptr.carbon
@@ -123,12 +123,8 @@ fn ConvertNullptrConstant() -> Core.Optional(i32*) {
 // CHECK:STDOUT: define ptr @_CReturnConvertedNullptrIndirectly.Main() #2 !dbg !36 {
 // CHECK:STDOUT: entry:
 // CHECK:STDOUT:   %a.var = alloca ptr, align 8, !dbg !37
-// CHECK:STDOUT:   %.loc27_44.1.temp = alloca ptr, align 8, !dbg !38
 // CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %a.var), !dbg !37
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %.loc27_44.1.temp), !dbg !38
-// CHECK:STDOUT:   call void @_Z13ReturnNullptrv.carbon_thunk(ptr %.loc27_44.1.temp), !dbg !38
-// CHECK:STDOUT:   %.loc27_44.2 = load ptr, ptr %.loc27_44.1.temp, align 8, !dbg !38
-// CHECK:STDOUT:   store ptr %.loc27_44.2, ptr %a.var, align 8, !dbg !37
+// CHECK:STDOUT:   call void @_Z13ReturnNullptrv.carbon_thunk(ptr %a.var), !dbg !38
 // CHECK:STDOUT:   %.loc28_10 = load ptr, ptr %a.var, align 8, !dbg !39
 // CHECK:STDOUT:   %Cpp.nullptr_t.as.ImplicitAs.impl.Convert.call = call ptr @"_CConvert.NullptrT.CppCompat.Core:ImplicitAs.95db8d3a03540861.Core.b88d1103f417c6d4"(ptr %.loc28_10), !dbg !40
 // CHECK:STDOUT:   ret ptr %Cpp.nullptr_t.as.ImplicitAs.impl.Convert.call, !dbg !40
@@ -140,8 +136,8 @@ fn ConvertNullptrConstant() -> Core.Optional(i32*) {
 // CHECK:STDOUT:   %.loc32_28.1.temp = alloca ptr, align 8, !dbg !42
 // CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %.loc32_28.1.temp), !dbg !42
 // CHECK:STDOUT:   call void @_Z13ReturnNullptrv.carbon_thunk(ptr %.loc32_28.1.temp), !dbg !42
-// CHECK:STDOUT:   %.loc32_28.2 = load ptr, ptr %.loc32_28.1.temp, align 8, !dbg !42
-// CHECK:STDOUT:   %Cpp.nullptr_t.as.ImplicitAs.impl.Convert.call = call ptr @"_CConvert.NullptrT.CppCompat.Core:ImplicitAs.95db8d3a03540861.Core.b88d1103f417c6d4"(ptr %.loc32_28.2), !dbg !43
+// CHECK:STDOUT:   %.loc32_28.4 = load ptr, ptr %.loc32_28.1.temp, align 8, !dbg !42
+// CHECK:STDOUT:   %Cpp.nullptr_t.as.ImplicitAs.impl.Convert.call = call ptr @"_CConvert.NullptrT.CppCompat.Core:ImplicitAs.95db8d3a03540861.Core.b88d1103f417c6d4"(ptr %.loc32_28.4), !dbg !43
 // CHECK:STDOUT:   ret ptr %Cpp.nullptr_t.as.ImplicitAs.impl.Convert.call, !dbg !43
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
@@ -170,7 +166,7 @@ fn ConvertNullptrConstant() -> Core.Optional(i32*) {
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; uselistorder directives
 // CHECK:STDOUT: uselistorder ptr @"_CConvert.NullptrT.CppCompat.Core:ImplicitAs.95db8d3a03540861.Core.b88d1103f417c6d4", { 3, 2, 1, 0 }
-// CHECK:STDOUT: uselistorder ptr @llvm.lifetime.start.p0, { 5, 4, 3, 2, 1, 0 }
+// CHECK:STDOUT: uselistorder ptr @llvm.lifetime.start.p0, { 4, 3, 2, 1, 0 }
 // CHECK:STDOUT:
 // CHECK:STDOUT: attributes #0 = { alwaysinline mustprogress uwtable "min-legal-vector-width"="0" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+cmov,+cx8,+fxsr,+mmx,+sse,+sse2,+x87" "tune-cpu"="generic" }
 // CHECK:STDOUT: attributes #1 = { "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+cmov,+cx8,+fxsr,+mmx,+sse,+sse2,+x87" "tune-cpu"="generic" }
diff --git a/toolchain/lower/testdata/interop/cpp/return.carbon b/toolchain/lower/testdata/interop/cpp/return.carbon
index eb3982ae0d37..29f37c085270 100644
--- a/toolchain/lower/testdata/interop/cpp/return.carbon
+++ b/toolchain/lower/testdata/interop/cpp/return.carbon
@@ -175,8 +175,8 @@ fn Call(x: Cpp.D) -> Cpp.C {
 // CHECK:STDOUT:   %.loc6_40.1.temp = alloca i8, align 1, !dbg !24
 // CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %.loc6_40.1.temp), !dbg !24
 // CHECK:STDOUT:   call void @_Z8ReturnU8v.carbon_thunk(ptr %.loc6_40.1.temp), !dbg !24
-// CHECK:STDOUT:   %.loc6_40.2 = load i8, ptr %.loc6_40.1.temp, align 1, !dbg !24
-// CHECK:STDOUT:   ret i8 %.loc6_40.2, !dbg !25
+// CHECK:STDOUT:   %0 = load i8, ptr %.loc6_40.1.temp, align 1, !dbg !25
+// CHECK:STDOUT:   ret i8 %0, !dbg !25
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
@@ -185,8 +185,8 @@ fn Call(x: Cpp.D) -> Cpp.C {
 // CHECK:STDOUT:   %.loc7_43.1.temp = alloca i16, align 2, !dbg !30
 // CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %.loc7_43.1.temp), !dbg !30
 // CHECK:STDOUT:   call void @_Z9ReturnU16v.carbon_thunk(ptr %.loc7_43.1.temp), !dbg !30
-// CHECK:STDOUT:   %.loc7_43.2 = load i16, ptr %.loc7_43.1.temp, align 2, !dbg !30
-// CHECK:STDOUT:   ret i16 %.loc7_43.2, !dbg !31
+// CHECK:STDOUT:   %0 = load i16, ptr %.loc7_43.1.temp, align 2, !dbg !31
+// CHECK:STDOUT:   ret i16 %0, !dbg !31
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
@@ -213,8 +213,8 @@ fn Call(x: Cpp.D) -> Cpp.C {
 // CHECK:STDOUT:   %.loc11_40.1.temp = alloca i8, align 1, !dbg !48
 // CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %.loc11_40.1.temp), !dbg !48
 // CHECK:STDOUT:   call void @_Z8ReturnI8v.carbon_thunk(ptr %.loc11_40.1.temp), !dbg !48
-// CHECK:STDOUT:   %.loc11_40.2 = load i8, ptr %.loc11_40.1.temp, align 1, !dbg !48
-// CHECK:STDOUT:   ret i8 %.loc11_40.2, !dbg !49
+// CHECK:STDOUT:   %0 = load i8, ptr %.loc11_40.1.temp, align 1, !dbg !49
+// CHECK:STDOUT:   ret i8 %0, !dbg !49
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
@@ -223,8 +223,8 @@ fn Call(x: Cpp.D) -> Cpp.C {
 // CHECK:STDOUT:   %.loc12_43.1.temp = alloca i16, align 2, !dbg !54
 // CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %.loc12_43.1.temp), !dbg !54
 // CHECK:STDOUT:   call void @_Z9ReturnI16v.carbon_thunk(ptr %.loc12_43.1.temp), !dbg !54
-// CHECK:STDOUT:   %.loc12_43.2 = load i16, ptr %.loc12_43.1.temp, align 2, !dbg !54
-// CHECK:STDOUT:   ret i16 %.loc12_43.2, !dbg !55
+// CHECK:STDOUT:   %0 = load i16, ptr %.loc12_43.1.temp, align 2, !dbg !55
+// CHECK:STDOUT:   ret i16 %0, !dbg !55
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
@@ -256,21 +256,21 @@ fn Call(x: Cpp.D) -> Cpp.C {
 // CHECK:STDOUT:   %.loc25_35.1.temp = alloca i16, align 2, !dbg !74
 // CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %.loc19_32.1.temp), !dbg !71
 // CHECK:STDOUT:   call void @_Z8ReturnU8v.carbon_thunk(ptr %.loc19_32.1.temp), !dbg !71
-// CHECK:STDOUT:   %.loc19_32.2 = load i8, ptr %.loc19_32.1.temp, align 1, !dbg !71
+// CHECK:STDOUT:   %.loc19_32.4 = load i8, ptr %.loc19_32.1.temp, align 1, !dbg !71
 // CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %.loc20_35.1.temp), !dbg !72
 // CHECK:STDOUT:   call void @_Z9ReturnU16v.carbon_thunk(ptr %.loc20_35.1.temp), !dbg !72
-// CHECK:STDOUT:   %.loc20_35.2 = load i16, ptr %.loc20_35.1.temp, align 2, !dbg !72
+// CHECK:STDOUT:   %.loc20_35.4 = load i16, ptr %.loc20_35.1.temp, align 2, !dbg !72
 // CHECK:STDOUT:   %ReturnU32.call = call i32 @_Z9ReturnU32v(), !dbg !75
 // CHECK:STDOUT:   %ReturnU64.call = call i64 @_Z9ReturnU64v(), !dbg !76
 // CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %.loc24_32.1.temp), !dbg !73
 // CHECK:STDOUT:   call void @_Z8ReturnI8v.carbon_thunk(ptr %.loc24_32.1.temp), !dbg !73
-// CHECK:STDOUT:   %.loc24_32.2 = load i8, ptr %.loc24_32.1.temp, align 1, !dbg !73
+// CHECK:STDOUT:   %.loc24_32.4 = load i8, ptr %.loc24_32.1.temp, align 1, !dbg !73
 // CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %.loc25_35.1.temp), !dbg !74
 // CHECK:STDOUT:   call void @_Z9ReturnI16v.carbon_thunk(ptr %.loc25_35.1.temp), !dbg !74
-// CHECK:STDOUT:   %.loc25_35.2 = load i16, ptr %.loc25_35.1.temp, align 2, !dbg !74
+// CHECK:STDOUT:   %.loc25_35.4 = load i16, ptr %.loc25_35.1.temp, align 2, !dbg !74
 // CHECK:STDOUT:   %ReturnI32.call = call i32 @_Z9ReturnI32v(), !dbg !77
 // CHECK:STDOUT:   %ReturnI64.call = call i64 @_Z9ReturnI64v(), !dbg !78
-// CHECK:STDOUT:   call void @_CUse.Main(i8 %.loc19_32.2, i16 %.loc20_35.2, i32 %ReturnU32.call, i64 %ReturnU64.call, i8 %.loc24_32.2, i16 %.loc25_35.2, i32 %ReturnI32.call, i64 %ReturnI64.call), !dbg !79
+// CHECK:STDOUT:   call void @_CUse.Main(i8 %.loc19_32.4, i16 %.loc20_35.4, i32 %ReturnU32.call, i64 %ReturnU64.call, i8 %.loc24_32.4, i16 %.loc25_35.4, i32 %ReturnI32.call, i64 %ReturnI64.call), !dbg !79
 // CHECK:STDOUT:   ret void, !dbg !80
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
@@ -278,49 +278,33 @@ fn Call(x: Cpp.D) -> Cpp.C {
 // CHECK:STDOUT: define void @_CVars.Main() #2 !dbg !81 {
 // CHECK:STDOUT: entry:
 // CHECK:STDOUT:   %my_u8.var = alloca i8, align 1, !dbg !82
-// CHECK:STDOUT:   %.loc33_32.1.temp = alloca i8, align 1, !dbg !83
-// CHECK:STDOUT:   %my_u16.var = alloca i16, align 2, !dbg !84
-// CHECK:STDOUT:   %.loc34_35.1.temp = alloca i16, align 2, !dbg !85
-// CHECK:STDOUT:   %my_u32.var = alloca i32, align 4, !dbg !86
-// CHECK:STDOUT:   %my_u64.var = alloca i64, align 8, !dbg !87
-// CHECK:STDOUT:   %my_i8.var = alloca i8, align 1, !dbg !88
-// CHECK:STDOUT:   %.loc38_32.1.temp = alloca i8, align 1, !dbg !89
-// CHECK:STDOUT:   %my_i16.var = alloca i16, align 2, !dbg !90
-// CHECK:STDOUT:   %.loc39_35.1.temp = alloca i16, align 2, !dbg !91
-// CHECK:STDOUT:   %my_i32.var = alloca i32, align 4, !dbg !92
-// CHECK:STDOUT:   %my_i64.var = alloca i64, align 8, !dbg !93
+// CHECK:STDOUT:   %my_u16.var = alloca i16, align 2, !dbg !83
+// CHECK:STDOUT:   %my_u32.var = alloca i32, align 4, !dbg !84
+// CHECK:STDOUT:   %my_u64.var = alloca i64, align 8, !dbg !85
+// CHECK:STDOUT:   %my_i8.var = alloca i8, align 1, !dbg !86
+// CHECK:STDOUT:   %my_i16.var = alloca i16, align 2, !dbg !87
+// CHECK:STDOUT:   %my_i32.var = alloca i32, align 4, !dbg !88
+// CHECK:STDOUT:   %my_i64.var = alloca i64, align 8, !dbg !89
 // CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %my_u8.var), !dbg !82
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %.loc33_32.1.temp), !dbg !83
-// CHECK:STDOUT:   call void @_Z8ReturnU8v.carbon_thunk(ptr %.loc33_32.1.temp), !dbg !83
-// CHECK:STDOUT:   %.loc33_32.2 = load i8, ptr %.loc33_32.1.temp, align 1, !dbg !83
-// CHECK:STDOUT:   store i8 %.loc33_32.2, ptr %my_u8.var, align 1, !dbg !82
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %my_u16.var), !dbg !84
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %.loc34_35.1.temp), !dbg !85
-// CHECK:STDOUT:   call void @_Z9ReturnU16v.carbon_thunk(ptr %.loc34_35.1.temp), !dbg !85
-// CHECK:STDOUT:   %.loc34_35.2 = load i16, ptr %.loc34_35.1.temp, align 2, !dbg !85
-// CHECK:STDOUT:   store i16 %.loc34_35.2, ptr %my_u16.var, align 2, !dbg !84
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %my_u32.var), !dbg !86
-// CHECK:STDOUT:   %ReturnU32.call = call i32 @_Z9ReturnU32v(), !dbg !94
-// CHECK:STDOUT:   store i32 %ReturnU32.call, ptr %my_u32.var, align 4, !dbg !86
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %my_u64.var), !dbg !87
-// CHECK:STDOUT:   %ReturnU64.call = call i64 @_Z9ReturnU64v(), !dbg !95
-// CHECK:STDOUT:   store i64 %ReturnU64.call, ptr %my_u64.var, align 8, !dbg !87
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %my_i8.var), !dbg !88
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %.loc38_32.1.temp), !dbg !89
-// CHECK:STDOUT:   call void @_Z8ReturnI8v.carbon_thunk(ptr %.loc38_32.1.temp), !dbg !89
-// CHECK:STDOUT:   %.loc38_32.2 = load i8, ptr %.loc38_32.1.temp, align 1, !dbg !89
-// CHECK:STDOUT:   store i8 %.loc38_32.2, ptr %my_i8.var, align 1, !dbg !88
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %my_i16.var), !dbg !90
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %.loc39_35.1.temp), !dbg !91
-// CHECK:STDOUT:   call void @_Z9ReturnI16v.carbon_thunk(ptr %.loc39_35.1.temp), !dbg !91
-// CHECK:STDOUT:   %.loc39_35.2 = load i16, ptr %.loc39_35.1.temp, align 2, !dbg !91
-// CHECK:STDOUT:   store i16 %.loc39_35.2, ptr %my_i16.var, align 2, !dbg !90
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %my_i32.var), !dbg !92
+// CHECK:STDOUT:   call void @_Z8ReturnU8v.carbon_thunk(ptr %my_u8.var), !dbg !90
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %my_u16.var), !dbg !83
+// CHECK:STDOUT:   call void @_Z9ReturnU16v.carbon_thunk(ptr %my_u16.var), !dbg !91
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %my_u32.var), !dbg !84
+// CHECK:STDOUT:   %ReturnU32.call = call i32 @_Z9ReturnU32v(), !dbg !92
+// CHECK:STDOUT:   store i32 %ReturnU32.call, ptr %my_u32.var, align 4, !dbg !84
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %my_u64.var), !dbg !85
+// CHECK:STDOUT:   %ReturnU64.call = call i64 @_Z9ReturnU64v(), !dbg !93
+// CHECK:STDOUT:   store i64 %ReturnU64.call, ptr %my_u64.var, align 8, !dbg !85
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %my_i8.var), !dbg !86
+// CHECK:STDOUT:   call void @_Z8ReturnI8v.carbon_thunk(ptr %my_i8.var), !dbg !94
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %my_i16.var), !dbg !87
+// CHECK:STDOUT:   call void @_Z9ReturnI16v.carbon_thunk(ptr %my_i16.var), !dbg !95
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %my_i32.var), !dbg !88
 // CHECK:STDOUT:   %ReturnI32.call = call i32 @_Z9ReturnI32v(), !dbg !96
-// CHECK:STDOUT:   store i32 %ReturnI32.call, ptr %my_i32.var, align 4, !dbg !92
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %my_i64.var), !dbg !93
+// CHECK:STDOUT:   store i32 %ReturnI32.call, ptr %my_i32.var, align 4, !dbg !88
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %my_i64.var), !dbg !89
 // CHECK:STDOUT:   %ReturnI64.call = call i64 @_Z9ReturnI64v(), !dbg !97
-// CHECK:STDOUT:   store i64 %ReturnI64.call, ptr %my_i64.var, align 8, !dbg !93
+// CHECK:STDOUT:   store i64 %ReturnI64.call, ptr %my_i64.var, align 8, !dbg !89
 // CHECK:STDOUT:   %.loc43_7 = load i8, ptr %my_u8.var, align 1, !dbg !98
 // CHECK:STDOUT:   %.loc43_14 = load i16, ptr %my_u16.var, align 2, !dbg !99
 // CHECK:STDOUT:   %.loc43_22 = load i32, ptr %my_u32.var, align 4, !dbg !100
@@ -337,7 +321,7 @@ fn Call(x: Cpp.D) -> Cpp.C {
 // CHECK:STDOUT: declare void @llvm.lifetime.start.p0(ptr captures(none)) #3
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; uselistorder directives
-// CHECK:STDOUT: uselistorder ptr @llvm.lifetime.start.p0, { 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0 }
+// CHECK:STDOUT: uselistorder ptr @llvm.lifetime.start.p0, { 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0 }
 // CHECK:STDOUT:
 // CHECK:STDOUT: attributes #0 = { alwaysinline mustprogress uwtable "min-legal-vector-width"="0" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+cmov,+cx8,+fxsr,+mmx,+sse,+sse2,+x87" "tune-cpu"="generic" }
 // CHECK:STDOUT: attributes #1 = { "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+cmov,+cx8,+fxsr,+mmx,+sse,+sse2,+x87" "tune-cpu"="generic" }
@@ -431,19 +415,19 @@ fn Call(x: Cpp.D) -> Cpp.C {
 // CHECK:STDOUT: !80 = !DILocation(line: 18, column: 1, scope: !68)
 // CHECK:STDOUT: !81 = distinct !DISubprogram(name: "Vars", linkageName: "_CVars.Main", scope: null, file: !7, line: 32, type: !69, spFlags: DISPFlagDefinition, unit: !6)
 // CHECK:STDOUT: !82 = !DILocation(line: 33, column: 3, scope: !81)
-// CHECK:STDOUT: !83 = !DILocation(line: 33, column: 19, scope: !81)
-// CHECK:STDOUT: !84 = !DILocation(line: 34, column: 3, scope: !81)
-// CHECK:STDOUT: !85 = !DILocation(line: 34, column: 21, scope: !81)
-// CHECK:STDOUT: !86 = !DILocation(line: 35, column: 3, scope: !81)
-// CHECK:STDOUT: !87 = !DILocation(line: 36, column: 3, scope: !81)
-// CHECK:STDOUT: !88 = !DILocation(line: 38, column: 3, scope: !81)
-// CHECK:STDOUT: !89 = !DILocation(line: 38, column: 19, scope: !81)
-// CHECK:STDOUT: !90 = !DILocation(line: 39, column: 3, scope: !81)
-// CHECK:STDOUT: !91 = !DILocation(line: 39, column: 21, scope: !81)
-// CHECK:STDOUT: !92 = !DILocation(line: 40, column: 3, scope: !81)
-// CHECK:STDOUT: !93 = !DILocation(line: 41, column: 3, scope: !81)
-// CHECK:STDOUT: !94 = !DILocation(line: 35, column: 21, scope: !81)
-// CHECK:STDOUT: !95 = !DILocation(line: 36, column: 21, scope: !81)
+// CHECK:STDOUT: !83 = !DILocation(line: 34, column: 3, scope: !81)
+// CHECK:STDOUT: !84 = !DILocation(line: 35, column: 3, scope: !81)
+// CHECK:STDOUT: !85 = !DILocation(line: 36, column: 3, scope: !81)
+// CHECK:STDOUT: !86 = !DILocation(line: 38, column: 3, scope: !81)
+// CHECK:STDOUT: !87 = !DILocation(line: 39, column: 3, scope: !81)
+// CHECK:STDOUT: !88 = !DILocation(line: 40, column: 3, scope: !81)
+// CHECK:STDOUT: !89 = !DILocation(line: 41, column: 3, scope: !81)
+// CHECK:STDOUT: !90 = !DILocation(line: 33, column: 19, scope: !81)
+// CHECK:STDOUT: !91 = !DILocation(line: 34, column: 21, scope: !81)
+// CHECK:STDOUT: !92 = !DILocation(line: 35, column: 21, scope: !81)
+// CHECK:STDOUT: !93 = !DILocation(line: 36, column: 21, scope: !81)
+// CHECK:STDOUT: !94 = !DILocation(line: 38, column: 19, scope: !81)
+// CHECK:STDOUT: !95 = !DILocation(line: 39, column: 21, scope: !81)
 // CHECK:STDOUT: !96 = !DILocation(line: 40, column: 21, scope: !81)
 // CHECK:STDOUT: !97 = !DILocation(line: 41, column: 21, scope: !81)
 // CHECK:STDOUT: !98 = !DILocation(line: 43, column: 7, scope: !81)
diff --git a/toolchain/sem_ir/expr_info.cpp b/toolchain/sem_ir/expr_info.cpp
index 3c669442ad6b..6f7fdb898c80 100644
--- a/toolchain/sem_ir/expr_info.cpp
+++ b/toolchain/sem_ir/expr_info.cpp
@@ -69,12 +69,12 @@ static auto GetExprCategoryImpl(const File* ir, InstId inst_id)
                 *ir, callee_function.resolved_specific_id);
             if (!return_form_id.has_value()) {
               // Treat as equivalent to `-> ()`.
-              return ExprCategory::Initializing;
+              return ExprCategory::ReprInitializing;
             }
             auto return_form = ir->insts().Get(return_form_id);
             CARBON_KIND_SWITCH(return_form) {
               case CARBON_KIND(InitForm _):
-                return ExprCategory::Initializing;
+                return ExprCategory::ReprInitializing;
               case CARBON_KIND(RefForm _):
                 return ExprCategory::DurableRef;
               case CARBON_KIND(ErrorInst _):
@@ -88,7 +88,7 @@ static auto GetExprCategoryImpl(const File* ir, InstId inst_id)
           }
           case CARBON_KIND(SemIR::CalleeCppOverloadSet _): {
             // TODO: support `ref` returns from C++.
-            return ExprCategory::Initializing;
+            return ExprCategory::ReprInitializing;
           }
         }
       } else {
@@ -140,8 +140,8 @@ auto GetExprCategory(const File& file, InstId inst_id) -> ExprCategory {
   return GetExprCategoryImpl(&file, inst_id);
 }
 
-auto FindReturnSlotArgForInitializer(const File& sem_ir, InstId init_id,
-                                     bool allow_transitive) -> InstId {
+auto FindStorageArgForInitializer(const File& sem_ir, InstId init_id,
+                                  bool allow_transitive) -> InstId {
   while (true) {
     Inst init_untyped = sem_ir.insts().Get(init_id);
     CARBON_KIND_SWITCH(init_untyped) {
@@ -171,13 +171,10 @@ auto FindReturnSlotArgForInitializer(const File& sem_ir, InstId init_id,
       case CARBON_KIND(TupleInit init): {
         return init.dest_id;
       }
-      case CARBON_KIND(InitializeFrom init): {
+      case CARBON_KIND(InPlaceInit init): {
         return init.dest_id;
       }
-      case CARBON_KIND(InPlaceInit init): {
-        if (!InitRepr::ForType(sem_ir, init.type_id).MightBeInPlace()) {
-          return InstId::None;
-        }
+      case CARBON_KIND(MarkInPlaceInit init): {
         return init.dest_id;
       }
       case CARBON_KIND(Call call): {
diff --git a/toolchain/sem_ir/expr_info.h b/toolchain/sem_ir/expr_info.h
index 81136b362963..f4f91a3032ce 100644
--- a/toolchain/sem_ir/expr_info.h
+++ b/toolchain/sem_ir/expr_info.h
@@ -21,13 +21,23 @@ inline auto IsRefCategory(ExprCategory cat) -> bool {
   return cat == ExprCategory::DurableRef || cat == ExprCategory::EphemeralRef;
 }
 
-// Given a primitive-form initializing expression, find its return slot
-// argument. If `allow_transitive` is true, the result may be an argument to
-// some other inst whose outcome is forwarded by `init_id`; otherwise the result
-// must be an argument to `init_id` itself. Returns `None` if no such return
-// slot is found.
-auto FindReturnSlotArgForInitializer(const File& sem_ir, InstId init_id,
-                                     bool allow_transitive = true) -> InstId;
+// Returns whether the given expression category is for an initializer
+// (see inst_kind.h for background).
+inline auto IsInitializerCategory(ExprCategory cat) -> bool {
+  return cat == ExprCategory::ReprInitializing ||
+         cat == ExprCategory::InPlaceInitializing;
+}
+
+// If `init_id` is an initializer, find the inst ID that specifies the storage
+// to initialize, if any. If `allow_transitive` is true, the result may be an
+// argument to some other inst whose outcome is forwarded by `init_id`;
+// otherwise the result must be an argument to `init_id` itself. Returns `None`
+// if there is no such storage argument. When `allow_transitive` is true, this
+// can only return `None` if `init_id` is known not to perform in-place
+// initialization; i.e. its type's initializing representation is not in-place,
+// and its category is `Initializing`.
+auto FindStorageArgForInitializer(const File& sem_ir, InstId init_id,
+                                  bool allow_transitive = true) -> InstId;
 
 }  // namespace Carbon::SemIR
 
diff --git a/toolchain/sem_ir/formatter.cpp b/toolchain/sem_ir/formatter.cpp
index 7551edca4acb..7d553f34777c 100644
--- a/toolchain/sem_ir/formatter.cpp
+++ b/toolchain/sem_ir/formatter.cpp
@@ -1029,10 +1029,11 @@ auto Formatter::FormatInstLhs(InstId inst_id, Inst inst) -> void {
         out_ << "ref ";
         FormatTypeOfInst(inst_id);
         break;
-      case ExprCategory::Initializing: {
+      case ExprCategory::InPlaceInitializing:
+      case ExprCategory::ReprInitializing: {
         out_ << "init ";
         FormatTypeOfInst(inst_id);
-        auto init_target_id = FindReturnSlotArgForInitializer(
+        auto init_target_id = FindStorageArgForInitializer(
             *sem_ir_, inst_id, /*allow_transitive=*/false);
         FormatReturnSlotArg(init_target_id);
         break;
@@ -1159,7 +1160,7 @@ auto Formatter::FormatInstRhs(Inst inst) -> void {
       return;
     }
 
-    case CARBON_KIND(InitializeFrom init): {
+    case CARBON_KIND(InPlaceInit init): {
       FormatArgs(init.src_id);
       return;
     }
@@ -1267,21 +1268,6 @@ auto Formatter::FormatInstRhs(Inst inst) -> void {
       return;
     }
 
-    case CARBON_KIND(InPlaceInit in_place): {
-      // Omit dest_id if it will be part of the expression form.
-      //
-      // TODO: should it always be part of the expression form? If so, fix
-      // FindReturnSlotArgForInitializer to always return it, and then
-      // FormatInstRhsDefault will do the right thing.
-      if (SemIR::InitRepr::ForType(*sem_ir_, in_place.type_id)
-              .MightBeInPlace()) {
-        FormatArgs(in_place.src_id);
-      } else {
-        FormatArgs(in_place.src_id, in_place.dest_id);
-      }
-      return;
-    }
-
     default:
       FormatInstRhsDefault(inst);
       return;
diff --git a/toolchain/sem_ir/inst_kind.def b/toolchain/sem_ir/inst_kind.def
index 971321edd449..96bc79e552a5 100644
--- a/toolchain/sem_ir/inst_kind.def
+++ b/toolchain/sem_ir/inst_kind.def
@@ -86,9 +86,9 @@ CARBON_SEM_IR_INST_KIND(ImportCppDecl)
 CARBON_SEM_IR_INST_KIND(ImportDecl)
 CARBON_SEM_IR_INST_KIND(ImportRefLoaded)
 CARBON_SEM_IR_INST_KIND(ImportRefUnloaded)
-CARBON_SEM_IR_INST_KIND(InPlaceInit)
+CARBON_SEM_IR_INST_KIND(MarkInPlaceInit)
 CARBON_SEM_IR_INST_KIND(InitForm)
-CARBON_SEM_IR_INST_KIND(InitializeFrom)
+CARBON_SEM_IR_INST_KIND(InPlaceInit)
 CARBON_SEM_IR_INST_KIND(InstType)
 CARBON_SEM_IR_INST_KIND(InstValue)
 CARBON_SEM_IR_INST_KIND(IntLiteralType)
diff --git a/toolchain/sem_ir/inst_kind.h b/toolchain/sem_ir/inst_kind.h
index d3974782d2f1..62a69a7d7504 100644
--- a/toolchain/sem_ir/inst_kind.h
+++ b/toolchain/sem_ir/inst_kind.h
@@ -17,7 +17,47 @@ namespace Carbon::SemIR {
 struct TypeId;
 
 // The expression category of an instruction. See /docs/design/values.md for
-// details.
+// background.
+//
+// Several categories are concerned with object initialization. At the SemIR
+// level, initialization consists of several phase transitions:
+// 1. A _repr-initializing_ expression forms an initializing representation of
+//    the object's eventual contents.
+// 2. An _in-place initializing_ expression commits to writing an object
+//    representation to memory.
+// 3. An _ephemeral entire reference_ expression commits to a particular memory
+//    location for the object.
+// 4. Finally, the owner/lifetime for that object is specified. This need not be
+//    an expression, so it doesn't correspond to a particular expression
+//    category. Instead, the inst kinds that perform this role are marked with
+//    has_cleanup = true.`
+//
+// If an inst combines more than one of those transitions, its category is
+// determined by the last one it performs (which means a non-expression inst may
+// perform some of the first three steps). Note that the language-level category
+// "initializing expression" is the union of the repr-initializing and in-place
+// initializing categories, which exist only in the implementation.
+//
+// An _initializer_ is an inst in any of those three categories. An inst that
+// directly depends on it is said to _consume_ it, and typically an initializer
+// must be consumed by exactly one inst.
+//
+// Thus, the key distinction between an initializing expression and a reference
+// expression is that the storage location of a reference expression is fixed as
+// soon as it is evaluated, but the storage location of an initializing
+// expression is notionally set by the inst that consumes it. "Notionally",
+// because that distinction is obscured by two optimizations:
+// - The storage location inst is always a direct or indirect argument of the
+//   in-place initializing inst. The ID of the storage argument inst is fixed
+//   when the initializing inst is created, and can be found with
+//   `FindStorageArgForInitializer`, but the inst stored at that ID may be
+//   overwritten when the consumer is created. This makes the final SemIR appear
+//   as though the location was set by the initializing inst.
+// - When the initializing inst and its consumer are created together, the
+//   initializing inst is typically created with its storage argument already
+//   set, rather than creating and then immediately overwriting a placeholder.
+//
+// TODO: Add an enumerator for ephemeral entire references, when needed.
 enum class ExprCategory : int8_t {
   // This instruction does not correspond to an expression, and as such has no
   // category.
@@ -28,15 +68,21 @@ enum class ExprCategory : int8_t {
   Pattern,
   // This instruction represents a value expression.
   Value,
-  // This instruction represents a durable reference expression, that denotes an
-  // object that outlives the current full expression context.
-  DurableRef,
-  // This instruction represents an ephemeral reference expression, that denotes
+  // This instruction represents a repr-initializing expression (see above),
+  // which initializes an object using the type's initializing representation.
+  // It must be consumed exactly once unless the type's initializing
+  // representation is known not to be in-place.
+  ReprInitializing,
+  // This instruction represents an in-place initializing expression (see
+  // above), which initializes an object in-place, regardless of the type's
+  // initializing representation. It must be consumed exactly once.
+  InPlaceInitializing,
+  // This instruction represents a ephemeral non-entire reference, which denotes
   // an object that does not outlive the current full expression context.
   EphemeralRef,
-  // This instruction represents an initializing expression, that describes how
-  // to initialize an object.
-  Initializing,
+  // This instruction represents a durable reference expression, which denotes
+  // an object that outlives the current full expression context.
+  DurableRef,
   // This instruction represents a syntactic combination of expressions that are
   // permitted to have different expression categories. This is used for tuple
   // and struct literals, where the subexpressions for different elements can
diff --git a/toolchain/sem_ir/type_info.cpp b/toolchain/sem_ir/type_info.cpp
index 8c301a12d9e2..25f8e2e8dd77 100644
--- a/toolchain/sem_ir/type_info.cpp
+++ b/toolchain/sem_ir/type_info.cpp
@@ -56,6 +56,8 @@ auto ValueRepr::IsCopyOfObjectRepr(const File& file, TypeId orig_type_id) const
 auto InitRepr::ForType(const File& file, TypeId type_id) -> InitRepr {
   auto type_info = file.types().GetCompleteTypeInfo(type_id);
   if (type_info.abstract_class_id.has_value()) {
+    CARBON_CHECK(type_info.value_repr.kind == ValueRepr::Pointer, "{0}",
+                 type_info.value_repr.kind);
     return {.kind = InitRepr::Abstract};
   }
   switch (type_info.value_repr.kind) {
diff --git a/toolchain/sem_ir/typed_insts.h b/toolchain/sem_ir/typed_insts.h
index 77295bbd4524..926d2e5e79f1 100644
--- a/toolchain/sem_ir/typed_insts.h
+++ b/toolchain/sem_ir/typed_insts.h
@@ -166,7 +166,8 @@ struct ArrayIndex {
 // `dest_id` is the destination array object for the initialization.
 struct ArrayInit {
   static constexpr auto Kind = InstKind::ArrayInit.Define<Parse::NodeId>(
-      {.ir_name = "array_init", .expr_category = ExprCategory::Initializing});
+      {.ir_name = "array_init",
+       .expr_category = ExprCategory::ReprInitializing});
 
   TypeId type_id;
   InstBlockId inits_id;
@@ -197,9 +198,9 @@ struct AsCompatible {
   InstId source_id;
 };
 
-// Performs a source-level initialization or assignment of `lhs_id` from
-// `rhs_id`. This finishes initialization of `lhs_id` in the same way as
-// `InitializeFrom`.
+// Consumes the initializer `rhs_id`, and uses it to performs a source-level
+// initialization or assignment of `lhs_id`. If `rhs_id` has a storage argument,
+// it is required to already be `lhs_id`.
 struct Assign {
   // TODO: Make Parse::NodeId more specific.
   static constexpr auto Kind = InstKind::Assign.Define<Parse::NodeId>(
@@ -435,7 +436,8 @@ struct ClassElementAccess {
 // Initializes a class object at dest_id with the contents of elements_id.
 struct ClassInit {
   static constexpr auto Kind = InstKind::ClassInit.Define<Parse::NodeId>(
-      {.ir_name = "class_init", .expr_category = ExprCategory::Initializing});
+      {.ir_name = "class_init",
+       .expr_category = ExprCategory::ReprInitializing});
 
   TypeId type_id;
   InstBlockId elements_id;
@@ -1023,19 +1025,21 @@ struct ImportRefLoaded {
   EntityNameId entity_name_id;
 };
 
-// Tracks that an object has been initialized in-place to form the result of
-// this expression, even if its type's initializing representation is not
-// normally in-place. If the type does not use in-place initialization,
-// initialization from this expression will copy the value out of the
-// destination.
+// DO NOT SUBMIT until this file and inst_kind.def are re-alphabetized.
+
+// Records that evaluation of the expression `src_id` will initialize the
+// storage identified by `dest_id` (even if its type's initializing
+// representation is not normally in-place), and forms an in-place initializing
+// expression to represent it. Note that `src_id` must find its target storage
+// using the exact ID `dest_id`, not another ID that aliases it.
 //
 // This is used to model the initialization performed by C++ thunks, where
 // in-place initialization is used even for types that would normally have a
 // copy initializing representation.
-struct InPlaceInit {
-  static constexpr auto Kind = InstKind::InPlaceInit.Define<Parse::NodeId>(
-      {.ir_name = "in_place_init",
-       .expr_category = ExprCategory::Initializing,
+struct MarkInPlaceInit {
+  static constexpr auto Kind = InstKind::MarkInPlaceInit.Define<Parse::NodeId>(
+      {.ir_name = "mark_in_place_init",
+       .expr_category = ExprCategory::InPlaceInitializing,
        .constant_kind = InstConstantKind::Never});
 
   TypeId type_id;
@@ -1061,16 +1065,17 @@ struct InitForm {
   CallParamIndex index;
 };
 
-// Finalizes the initialization of `dest_id` from the initializer expression
-// `src_id`, by performing a final copy from source to destination, for types
-// whose initialization is not in-place.
-struct InitializeFrom {
-  // Note this Parse::NodeId is unused. InitializeFrom is only constructed by
+// Consumes the repr-initializing expression `src_id` and forms an in-place
+// initializing expression that initializes the storage at `dest_id`, by
+// performing a final copy from source to destination for types whose
+// initialization is not in-place.
+struct InPlaceInit {
+  // Note this Parse::NodeId is unused. InPlaceInit is only constructed by
   // reusing locations.
   // TODO: Figure out if there's a better way to handle this case.
-  static constexpr auto Kind = InstKind::InitializeFrom.Define<Parse::NodeId>(
-      {.ir_name = "initialize_from",
-       .expr_category = ExprCategory::Initializing});
+  static constexpr auto Kind = InstKind::InPlaceInit.Define<Parse::NodeId>(
+      {.ir_name = "in_place_init",
+       .expr_category = ExprCategory::InPlaceInitializing});
 
   TypeId type_id;
   InstId src_id;
@@ -1546,6 +1551,9 @@ struct Return {
 };
 
 // A `return expr;` statement.
+//
+// If `expr_id` is an initializer, this consumes it. If `dest_id` is not `None`
+// and `expr_id` has a storage argument, the storage argument must be `dest_id`.
 struct ReturnExpr {
   static constexpr auto Kind = InstKind::ReturnExpr.Define<Parse::NodeId>(
       {.ir_name = "return",
@@ -1729,7 +1737,8 @@ struct StructAccess {
 // Initializes a dest struct with the provided elements.
 struct StructInit {
   static constexpr auto Kind = InstKind::StructInit.Define<Parse::NodeId>(
-      {.ir_name = "struct_init", .expr_category = ExprCategory::Initializing});
+      {.ir_name = "struct_init",
+       .expr_category = ExprCategory::ReprInitializing});
 
   TypeId type_id;
   InstBlockId elements_id;
@@ -1817,7 +1826,9 @@ struct SymbolicBindingType {
   InstId facet_value_inst_id;
 };
 
-// A temporary value.
+// Consumes the initializer `init_id`, uses it to initialize a temporary
+// object, and forms an ephemeral reference to it. If `init_id` has a
+// storage arg, it must be a `TemporaryStorage` inst.
 struct Temporary {
   static constexpr auto Kind = InstKind::Temporary.Define<Parse::NodeId>(
       {.ir_name = "temporary",
@@ -1858,7 +1869,8 @@ struct TupleAccess {
 // Initializes the destination tuple with the given elements.
 struct TupleInit {
   static constexpr auto Kind = InstKind::TupleInit.Define<Parse::NodeId>(
-      {.ir_name = "tuple_init", .expr_category = ExprCategory::Initializing});
+      {.ir_name = "tuple_init",
+       .expr_category = ExprCategory::ReprInitializing});
 
   TypeId type_id;
   InstBlockId elements_id;