diff --git a/toolchain/check/cpp/import.cpp b/toolchain/check/cpp/import.cpp
index e0b1d51189a0..c33688393a2c 100644
--- a/toolchain/check/cpp/import.cpp
+++ b/toolchain/check/cpp/import.cpp
@@ -1446,16 +1446,26 @@ static auto MakeParamPatternsBlockId(Context& context, SemIR::LocId loc_id,
 // TODO: Support more return types.
 static auto GetReturnTypeExpr(Context& context, SemIR::LocId loc_id,
                               clang::FunctionDecl* clang_decl) -> TypeExpr {
-  clang::QualType ret_type = clang_decl->getReturnType();
-  if (!ret_type->isVoidType()) {
-    TypeExpr mapped_type = MapType(context, loc_id, ret_type);
-    if (!mapped_type.inst_id.has_value()) {
+  clang::QualType orig_ret_type = clang_decl->getReturnType();
+  if (!orig_ret_type->isVoidType()) {
+    // We map `T&` return type to `addr param: T*`, and `T&&` parameters to
+    // `param: T`.
+    // TODO: Revisit this and decide what we really want to do here.
+    clang::QualType ret_type = orig_ret_type.getNonReferenceType();
+
+    auto [orig_type_inst_id, type_id] = MapType(context, loc_id, ret_type);
+    if (!orig_type_inst_id.has_value()) {
       context.TODO(loc_id, llvm::formatv("Unsupported: return type: {0}",
-                                         ret_type.getAsString()));
+                                         orig_ret_type.getAsString()));
       return {.inst_id = SemIR::ErrorInst::TypeInstId,
               .type_id = SemIR::ErrorInst::TypeId};
     }
-    return mapped_type;
+
+    if (orig_ret_type->isLValueReferenceType()) {
+      type_id = GetPointerType(context, orig_type_inst_id);
+    }
+
+    return {orig_type_inst_id, type_id};
   }
 
   auto* ctor = dyn_cast<clang::CXXConstructorDecl>(clang_decl);
diff --git a/toolchain/check/cpp/thunk.cpp b/toolchain/check/cpp/thunk.cpp
index 0cf43981dc58..0bf6f47d852e 100644
--- a/toolchain/check/cpp/thunk.cpp
+++ b/toolchain/check/cpp/thunk.cpp
@@ -241,6 +241,14 @@ static auto GetNonnullType(clang::ASTContext& ast_context,
                                        pointer_type, pointer_type);
 }
 
+// Given a type, returns the corresponding _Nonnull-qualified pointer type,
+// ignoring references.
+static auto GetNonNullablePointerType(clang::ASTContext& ast_context,
+                                      clang::QualType type) {
+  return GetNonnullType(ast_context,
+                        ast_context.getPointerType(type.getNonReferenceType()));
+}
+
 // Given the type of a callee parameter, returns the type to use for the
 // corresponding thunk parameter.
 static auto GetThunkParameterType(clang::ASTContext& ast_context,
@@ -249,8 +257,7 @@ static auto GetThunkParameterType(clang::ASTContext& ast_context,
   if (IsSimpleAbiType(ast_context, callee_type)) {
     return callee_type;
   }
-  return GetNonnullType(ast_context, ast_context.getPointerType(
-                                         callee_type.getNonReferenceType()));
+  return GetNonNullablePointerType(ast_context, callee_type);
 }
 
 // Creates the thunk parameter types given the callee function.
@@ -272,9 +279,8 @@ static auto BuildThunkParameterTypes(clang::ASTContext& ast_context,
   }
 
   if (!callee_info.has_simple_return_type) {
-    thunk_param_types.push_back(GetNonnullType(
-        ast_context,
-        ast_context.getPointerType(callee_info.effective_return_type)));
+    thunk_param_types.push_back(GetNonNullablePointerType(
+        ast_context, callee_info.effective_return_type));
   }
 
   CARBON_CHECK(thunk_param_types.size() == callee_info.num_thunk_params());
@@ -524,7 +530,7 @@ static auto BuildThunkBody(clang::Sema& sema,
 
   auto* return_object_addr = BuildThunkParamRef(
       sema, thunk_function_decl, callee_info.GetThunkReturnParamIndex());
-  auto return_type = callee_info.effective_return_type;
+  auto return_type = callee_info.effective_return_type.getNonReferenceType();
   auto* return_type_info =
       sema.Context.getTrivialTypeSourceInfo(return_type, clang_loc);
   auto placement_new = sema.BuildCXXNew(
diff --git a/toolchain/check/testdata/interop/cpp/function/reference.carbon b/toolchain/check/testdata/interop/cpp/function/reference.carbon
index 8758b87ebb2c..6b07514e8e17 100644
--- a/toolchain/check/testdata/interop/cpp/function/reference.carbon
+++ b/toolchain/check/testdata/interop/cpp/function/reference.carbon
@@ -223,22 +223,20 @@ fn F() {
 // Lvalue reference as return type
 // ============================================================================
 
-// --- fail_todo_call_return_lvalue_ref.carbon
+// --- return_lvalue_ref.h
 
-library "[[@TEST_NAME]]";
-
-import Cpp inline '''
 struct S {};
 
 auto ReturnsLValue() -> S&;
-''';
+
+// --- call_return_lvalue_ref.carbon
+
+library "[[@TEST_NAME]]";
+
+import Cpp library "return_lvalue_ref.h";
 
 fn F() {
   //@dump-sem-ir-begin
-  // CHECK:STDERR: fail_todo_call_return_lvalue_ref.carbon:[[@LINE+4]]:19: error: semantics TODO: `Unsupported: return type: S &` [SemanticsTodo]
-  // CHECK:STDERR:   let s: Cpp.S* = Cpp.ReturnsLValue();
-  // CHECK:STDERR:                   ^~~~~~~~~~~~~~~~~~~
-  // CHECK:STDERR:
   let s: Cpp.S* = Cpp.ReturnsLValue();
   //@dump-sem-ir-end
 }
@@ -247,22 +245,20 @@ fn F() {
 // Rvalue reference as return type
 // ============================================================================
 
-// --- fail_todo_call_return_rvalue_ref.carbon
+// --- return_rvalue_ref.h
 
-library "[[@TEST_NAME]]";
-
-import Cpp inline '''
 struct S {};
 
 auto ReturnsRValue() -> S&&;
-''';
+
+// --- call_return_rvalue_ref.carbon
+
+library "[[@TEST_NAME]]";
+
+import Cpp library "return_rvalue_ref.h";
 
 fn F() {
   //@dump-sem-ir-begin
-  // CHECK:STDERR: fail_todo_call_return_rvalue_ref.carbon:[[@LINE+4]]:18: error: semantics TODO: `Unsupported: return type: S &&` [SemanticsTodo]
-  // CHECK:STDERR:   var s: Cpp.S = Cpp.ReturnsRValue();
-  // CHECK:STDERR:                  ^~~~~~~~~~~~~~~~~~~
-  // CHECK:STDERR:
   var s: Cpp.S = Cpp.ReturnsRValue();
   //@dump-sem-ir-end
 }
@@ -271,26 +267,41 @@ fn F() {
 // Const reference as return type
 // ============================================================================
 
-// --- fail_todo_call_return_const_lvalue_ref.carbon
+// --- return_const_lvalue_ref.h
 
-library "[[@TEST_NAME]]";
-
-import Cpp inline '''
 struct S {};
 
 auto ReturnConstLValue() -> const S&;
-''';
+
+// --- call_return_const_lvalue_ref.carbon
+
+library "[[@TEST_NAME]]";
+
+import Cpp library "return_const_lvalue_ref.h";
 
 fn F() {
   //@dump-sem-ir-begin
-  // CHECK:STDERR: fail_todo_call_return_const_lvalue_ref.carbon:[[@LINE+4]]:24: error: semantics TODO: `Unsupported: return type: const S &` [SemanticsTodo]
-  // CHECK:STDERR:   var s: const Cpp.S = Cpp.ReturnConstLValue();
-  // CHECK:STDERR:                        ^~~~~~~~~~~~~~~~~~~~~~~
-  // CHECK:STDERR:
-  var s: const Cpp.S = Cpp.ReturnConstLValue();
+  var s: const Cpp.S* = Cpp.ReturnConstLValue();
   //@dump-sem-ir-end
 }
 
+// --- fail_call_return_const_lvalue_ref_const_correctness.carbon
+
+library "[[@TEST_NAME]]";
+
+import Cpp library "return_const_lvalue_ref.h";
+
+fn F() {
+  // CHECK:STDERR: fail_call_return_const_lvalue_ref_const_correctness.carbon:[[@LINE+7]]:3: error: cannot implicitly convert expression of type `const Cpp.S*` to `Cpp.S*` [ConversionFailure]
+  // CHECK:STDERR:   var s: Cpp.S* = Cpp.ReturnConstLValue();
+  // CHECK:STDERR:   ^~~~~~~~~~~~~
+  // CHECK:STDERR: fail_call_return_const_lvalue_ref_const_correctness.carbon:[[@LINE+4]]:3: note: type `const Cpp.S*` does not implement interface `Core.ImplicitAs(Cpp.S*)` [MissingImplInMemberAccessNote]
+  // CHECK:STDERR:   var s: Cpp.S* = Cpp.ReturnConstLValue();
+  // CHECK:STDERR:   ^~~~~~~~~~~~~
+  // CHECK:STDERR:
+  var s: Cpp.S* = Cpp.ReturnConstLValue();
+}
+
 // CHECK:STDOUT: --- call_param_lvalue_ref.carbon
 // CHECK:STDOUT:
 // CHECK:STDOUT: constants {
@@ -873,7 +884,7 @@ fn F() {
 // CHECK:STDOUT:   <elided>
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
-// CHECK:STDOUT: --- fail_todo_call_return_lvalue_ref.carbon
+// CHECK:STDOUT: --- call_return_lvalue_ref.carbon
 // CHECK:STDOUT:
 // CHECK:STDOUT: constants {
 // CHECK:STDOUT:   %S: type = class_type @S [concrete]
@@ -905,19 +916,21 @@ fn F() {
 // CHECK:STDOUT:   name_binding_decl {
 // CHECK:STDOUT:     %s.patt: %pattern_type = binding_pattern s [concrete]
 // CHECK:STDOUT:   }
-// CHECK:STDOUT:   %Cpp.ref.loc16_19: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
+// CHECK:STDOUT:   %Cpp.ref.loc8_19: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
 // CHECK:STDOUT:   %ReturnsLValue.ref: %ReturnsLValue.cpp_overload_set.type = name_ref ReturnsLValue, imports.%ReturnsLValue.cpp_overload_set.value [concrete = constants.%ReturnsLValue.cpp_overload_set.value]
-// CHECK:STDOUT:   %ReturnsLValue.call: init <error> = call imports.%ReturnsLValue.decl()
-// CHECK:STDOUT:   %.loc16: type = splice_block %ptr [concrete = constants.%ptr] {
-// CHECK:STDOUT:     %Cpp.ref.loc16_10: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
+// CHECK:STDOUT:   %ReturnsLValue.call: init %ptr = call imports.%ReturnsLValue.decl()
+// CHECK:STDOUT:   %.loc8_15: type = splice_block %ptr [concrete = constants.%ptr] {
+// CHECK:STDOUT:     %Cpp.ref.loc8_10: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
 // CHECK:STDOUT:     %S.ref: type = name_ref S, imports.%S.decl [concrete = constants.%S]
 // CHECK:STDOUT:     %ptr: type = ptr_type %S.ref [concrete = constants.%ptr]
 // CHECK:STDOUT:   }
-// CHECK:STDOUT:   %s: %ptr = bind_name s, <error> [concrete = <error>]
+// CHECK:STDOUT:   %.loc8_37.1: %ptr = value_of_initializer %ReturnsLValue.call
+// CHECK:STDOUT:   %.loc8_37.2: %ptr = converted %ReturnsLValue.call, %.loc8_37.1
+// CHECK:STDOUT:   %s: %ptr = bind_name s, %.loc8_37.2
 // CHECK:STDOUT:   <elided>
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
-// CHECK:STDOUT: --- fail_todo_call_return_rvalue_ref.carbon
+// CHECK:STDOUT: --- call_return_rvalue_ref.carbon
 // CHECK:STDOUT:
 // CHECK:STDOUT: constants {
 // CHECK:STDOUT:   %empty_tuple.type: type = tuple_type () [concrete]
@@ -925,13 +938,13 @@ fn F() {
 // CHECK:STDOUT:   %pattern_type.7da: type = pattern_type %S [concrete]
 // CHECK:STDOUT:   %ReturnsRValue.cpp_overload_set.type: type = cpp_overload_set_type @ReturnsRValue.cpp_overload_set [concrete]
 // CHECK:STDOUT:   %ReturnsRValue.cpp_overload_set.value: %ReturnsRValue.cpp_overload_set.type = cpp_overload_set_value @ReturnsRValue.cpp_overload_set [concrete]
-// CHECK:STDOUT:   %ReturnsRValue.type: type = fn_type @ReturnsRValue [concrete]
-// CHECK:STDOUT:   %ReturnsRValue: %ReturnsRValue.type = struct_value () [concrete]
+// CHECK:STDOUT:   %ptr.5c7: type = ptr_type %S [concrete]
+// CHECK:STDOUT:   %ReturnsRValue__carbon_thunk.type: type = fn_type @ReturnsRValue__carbon_thunk [concrete]
+// CHECK:STDOUT:   %ReturnsRValue__carbon_thunk: %ReturnsRValue__carbon_thunk.type = struct_value () [concrete]
 // CHECK:STDOUT:   %type_where: type = facet_type <type where .Self impls <CanDestroy>> [concrete]
 // CHECK:STDOUT:   %facet_value: %type_where = facet_value %S, () [concrete]
 // CHECK:STDOUT:   %DestroyT.binding.as_type.as.Destroy.impl.Op.type.34a: type = fn_type @DestroyT.binding.as_type.as.Destroy.impl.Op, @DestroyT.binding.as_type.as.Destroy.impl(%facet_value) [concrete]
 // CHECK:STDOUT:   %DestroyT.binding.as_type.as.Destroy.impl.Op.016: %DestroyT.binding.as_type.as.Destroy.impl.Op.type.34a = struct_value () [concrete]
-// CHECK:STDOUT:   %ptr.5c7: type = ptr_type %S [concrete]
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: imports {
@@ -942,7 +955,7 @@ fn F() {
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %S.decl: type = class_decl @S [concrete = constants.%S] {} {}
 // CHECK:STDOUT:   %ReturnsRValue.cpp_overload_set.value: %ReturnsRValue.cpp_overload_set.type = cpp_overload_set_value @ReturnsRValue.cpp_overload_set [concrete = constants.%ReturnsRValue.cpp_overload_set.value]
-// CHECK:STDOUT:   %ReturnsRValue.decl: %ReturnsRValue.type = fn_decl @ReturnsRValue [concrete = constants.%ReturnsRValue] {
+// CHECK:STDOUT:   %ReturnsRValue__carbon_thunk.decl: %ReturnsRValue__carbon_thunk.type = fn_decl @ReturnsRValue__carbon_thunk [concrete = constants.%ReturnsRValue__carbon_thunk] {
 // CHECK:STDOUT:     <elided>
 // CHECK:STDOUT:   } {
 // CHECK:STDOUT:     <elided>
@@ -956,41 +969,45 @@ fn F() {
 // CHECK:STDOUT:     %s.var_patt: %pattern_type.7da = var_pattern %s.patt [concrete]
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %s.var: ref %S = var %s.var_patt
-// CHECK:STDOUT:   %Cpp.ref.loc16_18: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
+// CHECK:STDOUT:   %Cpp.ref.loc8_18: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
 // CHECK:STDOUT:   %ReturnsRValue.ref: %ReturnsRValue.cpp_overload_set.type = name_ref ReturnsRValue, imports.%ReturnsRValue.cpp_overload_set.value [concrete = constants.%ReturnsRValue.cpp_overload_set.value]
-// CHECK:STDOUT:   %ReturnsRValue.call: init <error> = call imports.%ReturnsRValue.decl()
-// CHECK:STDOUT:   assign %s.var, <error>
-// CHECK:STDOUT:   %.loc16_13: type = splice_block %S.ref [concrete = constants.%S] {
-// CHECK:STDOUT:     %Cpp.ref.loc16_10: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
+// CHECK:STDOUT:   %.loc8_3.1: ref %S = splice_block %s.var {}
+// CHECK:STDOUT:   %addr.loc8_36: %ptr.5c7 = addr_of %.loc8_3.1
+// CHECK:STDOUT:   %ReturnsRValue__carbon_thunk.call: init %empty_tuple.type = call imports.%ReturnsRValue__carbon_thunk.decl(%addr.loc8_36)
+// CHECK:STDOUT:   %.loc8_36: init %S = in_place_init %ReturnsRValue__carbon_thunk.call, %.loc8_3.1
+// CHECK:STDOUT:   assign %s.var, %.loc8_36
+// CHECK:STDOUT:   %.loc8_13: type = splice_block %S.ref [concrete = constants.%S] {
+// CHECK:STDOUT:     %Cpp.ref.loc8_10: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
 // CHECK:STDOUT:     %S.ref: type = name_ref S, imports.%S.decl [concrete = constants.%S]
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %s: ref %S = bind_name s, %s.var
 // CHECK:STDOUT:   %facet_value: %type_where = facet_value constants.%S, () [concrete = constants.%facet_value]
-// CHECK:STDOUT:   %.loc16_3: %type_where = converted constants.%S, %facet_value [concrete = constants.%facet_value]
+// CHECK:STDOUT:   %.loc8_3.2: %type_where = converted constants.%S, %facet_value [concrete = constants.%facet_value]
 // CHECK:STDOUT:   %DestroyT.binding.as_type.as.Destroy.impl.Op.bound: <bound method> = bound_method %s.var, constants.%DestroyT.binding.as_type.as.Destroy.impl.Op.016
 // CHECK:STDOUT:   <elided>
 // CHECK:STDOUT:   %bound_method: <bound method> = bound_method %s.var, %DestroyT.binding.as_type.as.Destroy.impl.Op.specific_fn
-// CHECK:STDOUT:   %addr: %ptr.5c7 = addr_of %s.var
-// CHECK:STDOUT:   %DestroyT.binding.as_type.as.Destroy.impl.Op.call: init %empty_tuple.type = call %bound_method(%addr)
+// CHECK:STDOUT:   %addr.loc8_3: %ptr.5c7 = addr_of %s.var
+// CHECK:STDOUT:   %DestroyT.binding.as_type.as.Destroy.impl.Op.call: init %empty_tuple.type = call %bound_method(%addr.loc8_3)
 // CHECK:STDOUT:   <elided>
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
-// CHECK:STDOUT: --- fail_todo_call_return_const_lvalue_ref.carbon
+// CHECK:STDOUT: --- call_return_const_lvalue_ref.carbon
 // CHECK:STDOUT:
 // CHECK:STDOUT: constants {
 // CHECK:STDOUT:   %empty_tuple.type: type = tuple_type () [concrete]
 // CHECK:STDOUT:   %S: type = class_type @S [concrete]
 // CHECK:STDOUT:   %const: type = const_type %S [concrete]
-// CHECK:STDOUT:   %pattern_type.9be: type = pattern_type %const [concrete]
+// CHECK:STDOUT:   %ptr.ff5: type = ptr_type %const [concrete]
+// CHECK:STDOUT:   %pattern_type.32f: type = pattern_type %ptr.ff5 [concrete]
 // CHECK:STDOUT:   %ReturnConstLValue.cpp_overload_set.type: type = cpp_overload_set_type @ReturnConstLValue.cpp_overload_set [concrete]
 // CHECK:STDOUT:   %ReturnConstLValue.cpp_overload_set.value: %ReturnConstLValue.cpp_overload_set.type = cpp_overload_set_value @ReturnConstLValue.cpp_overload_set [concrete]
 // CHECK:STDOUT:   %ReturnConstLValue.type: type = fn_type @ReturnConstLValue [concrete]
 // CHECK:STDOUT:   %ReturnConstLValue: %ReturnConstLValue.type = struct_value () [concrete]
 // CHECK:STDOUT:   %type_where: type = facet_type <type where .Self impls <CanDestroy>> [concrete]
-// CHECK:STDOUT:   %facet_value: %type_where = facet_value %const, () [concrete]
-// CHECK:STDOUT:   %DestroyT.binding.as_type.as.Destroy.impl.Op.type.56e: type = fn_type @DestroyT.binding.as_type.as.Destroy.impl.Op, @DestroyT.binding.as_type.as.Destroy.impl(%facet_value) [concrete]
-// CHECK:STDOUT:   %DestroyT.binding.as_type.as.Destroy.impl.Op.089: %DestroyT.binding.as_type.as.Destroy.impl.Op.type.56e = struct_value () [concrete]
-// CHECK:STDOUT:   %ptr.ff5: type = ptr_type %const [concrete]
+// CHECK:STDOUT:   %facet_value: %type_where = facet_value %ptr.ff5, () [concrete]
+// CHECK:STDOUT:   %DestroyT.binding.as_type.as.Destroy.impl.Op.type.40d: type = fn_type @DestroyT.binding.as_type.as.Destroy.impl.Op, @DestroyT.binding.as_type.as.Destroy.impl(%facet_value) [concrete]
+// CHECK:STDOUT:   %DestroyT.binding.as_type.as.Destroy.impl.Op.c44: %DestroyT.binding.as_type.as.Destroy.impl.Op.type.40d = struct_value () [concrete]
+// CHECK:STDOUT:   %ptr.dec: type = ptr_type %ptr.ff5 [concrete]
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: imports {
@@ -1011,26 +1028,27 @@ fn F() {
 // CHECK:STDOUT: fn @F() {
 // CHECK:STDOUT: !entry:
 // CHECK:STDOUT:   name_binding_decl {
-// CHECK:STDOUT:     %s.patt: %pattern_type.9be = binding_pattern s [concrete]
-// CHECK:STDOUT:     %s.var_patt: %pattern_type.9be = var_pattern %s.patt [concrete]
+// CHECK:STDOUT:     %s.patt: %pattern_type.32f = binding_pattern s [concrete]
+// CHECK:STDOUT:     %s.var_patt: %pattern_type.32f = var_pattern %s.patt [concrete]
 // CHECK:STDOUT:   }
-// CHECK:STDOUT:   %s.var: ref %const = var %s.var_patt
-// CHECK:STDOUT:   %Cpp.ref.loc16_24: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
+// CHECK:STDOUT:   %s.var: ref %ptr.ff5 = var %s.var_patt
+// CHECK:STDOUT:   %Cpp.ref.loc8_25: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
 // CHECK:STDOUT:   %ReturnConstLValue.ref: %ReturnConstLValue.cpp_overload_set.type = name_ref ReturnConstLValue, imports.%ReturnConstLValue.cpp_overload_set.value [concrete = constants.%ReturnConstLValue.cpp_overload_set.value]
-// CHECK:STDOUT:   %ReturnConstLValue.call: init <error> = call imports.%ReturnConstLValue.decl()
-// CHECK:STDOUT:   assign %s.var, <error>
-// CHECK:STDOUT:   %.loc16_10: type = splice_block %const [concrete = constants.%const] {
-// CHECK:STDOUT:     %Cpp.ref.loc16_16: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
+// CHECK:STDOUT:   %ReturnConstLValue.call: init %ptr.ff5 = call imports.%ReturnConstLValue.decl()
+// CHECK:STDOUT:   assign %s.var, %ReturnConstLValue.call
+// CHECK:STDOUT:   %.loc8_21: type = splice_block %ptr [concrete = constants.%ptr.ff5] {
+// CHECK:STDOUT:     %Cpp.ref.loc8_16: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
 // CHECK:STDOUT:     %S.ref: type = name_ref S, imports.%S.decl [concrete = constants.%S]
 // CHECK:STDOUT:     %const: type = const_type %S.ref [concrete = constants.%const]
+// CHECK:STDOUT:     %ptr: type = ptr_type %const [concrete = constants.%ptr.ff5]
 // CHECK:STDOUT:   }
-// CHECK:STDOUT:   %s: ref %const = bind_name s, %s.var
-// CHECK:STDOUT:   %facet_value: %type_where = facet_value constants.%const, () [concrete = constants.%facet_value]
-// CHECK:STDOUT:   %.loc16_3: %type_where = converted constants.%const, %facet_value [concrete = constants.%facet_value]
-// CHECK:STDOUT:   %DestroyT.binding.as_type.as.Destroy.impl.Op.bound: <bound method> = bound_method %s.var, constants.%DestroyT.binding.as_type.as.Destroy.impl.Op.089
+// CHECK:STDOUT:   %s: ref %ptr.ff5 = bind_name s, %s.var
+// CHECK:STDOUT:   %facet_value: %type_where = facet_value constants.%ptr.ff5, () [concrete = constants.%facet_value]
+// CHECK:STDOUT:   %.loc8_3: %type_where = converted constants.%ptr.ff5, %facet_value [concrete = constants.%facet_value]
+// CHECK:STDOUT:   %DestroyT.binding.as_type.as.Destroy.impl.Op.bound: <bound method> = bound_method %s.var, constants.%DestroyT.binding.as_type.as.Destroy.impl.Op.c44
 // CHECK:STDOUT:   <elided>
 // CHECK:STDOUT:   %bound_method: <bound method> = bound_method %s.var, %DestroyT.binding.as_type.as.Destroy.impl.Op.specific_fn
-// CHECK:STDOUT:   %addr: %ptr.ff5 = addr_of %s.var
+// CHECK:STDOUT:   %addr: %ptr.dec = addr_of %s.var
 // CHECK:STDOUT:   %DestroyT.binding.as_type.as.Destroy.impl.Op.call: init %empty_tuple.type = call %bound_method(%addr)
 // CHECK:STDOUT:   <elided>
 // CHECK:STDOUT: }
diff --git a/toolchain/lower/testdata/interop/cpp/reference.carbon b/toolchain/lower/testdata/interop/cpp/reference.carbon
index fc17e41fffdf..5f1cc90535f4 100644
--- a/toolchain/lower/testdata/interop/cpp/reference.carbon
+++ b/toolchain/lower/testdata/interop/cpp/reference.carbon
@@ -10,23 +10,25 @@
 // TIP: To dump output, run:
 // TIP:   bazel run //toolchain/testing:file_test -- --dump_output --file_tests=toolchain/lower/testdata/interop/cpp/reference.carbon
 
-// --- reference_params.h
-
-class C {};
-
-void TakeCRef(C&);
-void TakeCRRef(C&&);
-void TakeConstCRef(const C&);
-
-void TakeIntRef(int&);
-void TakeIntRRef(int&&);
-void TakeConstIntRef(const int&);
+// ============================================================================
+// Reference params
+// ============================================================================
 
 // --- pass_references.carbon
 
 library "[[@TEST_NAME]]";
 
-import Cpp library "reference_params.h";
+import Cpp inline '''
+class C {};
+
+auto TakeCRef(C&) -> void;
+auto TakeCRRef(C&&) -> void;
+auto TakeConstCRef(const C&) -> void;
+
+auto TakeIntRef(int&) -> void;
+auto TakeIntRRef(int&&) -> void;
+auto TakeConstIntRef(const int&) -> void;
+''';
 
 fn PassRefs() {
   var c: Cpp.C;
@@ -40,30 +42,60 @@ fn PassRefs() {
   Cpp.TakeConstIntRef(n);
 }
 
+// ============================================================================
+// Reference return values
+// ============================================================================
+
+// --- return_references.carbon
+
+library "[[@TEST_NAME]]";
+
+import Cpp inline '''
+class C {};
+
+auto ReturnCRef() -> C&;
+auto ReturnCRRef() -> C&&;
+auto ReturnConstCRef() -> const C&;
+
+auto ReturnIntRef() -> int&;
+auto ReturnIntRRef() -> int&&;
+auto ReturnConstIntRef() -> const int&;
+''';
+
+fn GetRefs() {
+  var c1: Cpp.C* = Cpp.ReturnCRef();
+  var c2: Cpp.C = Cpp.ReturnCRRef();
+  var c3: const Cpp.C* = Cpp.ReturnConstCRef();
+
+  var n1: i32* = Cpp.ReturnIntRef();
+  var n2: i32 = Cpp.ReturnIntRRef();
+  var n3: const i32* = Cpp.ReturnConstIntRef();
+}
+
 // CHECK:STDOUT: ; ModuleID = 'pass_references.carbon'
 // CHECK:STDOUT: source_filename = "pass_references.carbon"
 // CHECK:STDOUT: target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128"
 // CHECK:STDOUT: target triple = "x86_64-unknown-linux-gnu"
 // CHECK:STDOUT:
-// CHECK:STDOUT: @C.val.loc9_18.3 = internal constant {} zeroinitializer
+// CHECK:STDOUT: @C.val.loc19_18.3 = internal constant {} zeroinitializer
 // CHECK:STDOUT:
 // CHECK:STDOUT: define void @_CPassRefs.Main() !dbg !7 {
 // CHECK:STDOUT: entry:
 // CHECK:STDOUT:   %c.var = alloca {}, align 8, !dbg !10
-// CHECK:STDOUT:   %.loc9_18.2.temp = alloca {}, align 8, !dbg !11
+// CHECK:STDOUT:   %.loc19_18.2.temp = alloca {}, align 8, !dbg !11
 // CHECK:STDOUT:   %n.var = alloca i32, align 4, !dbg !12
-// CHECK:STDOUT:   %.loc14_22.3.temp = alloca i32, align 4, !dbg !13
+// CHECK:STDOUT:   %.loc24_22.3.temp = alloca i32, align 4, !dbg !13
 // CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %c.var), !dbg !10
 // CHECK:STDOUT:   call void @_Z8TakeCRefR1C.carbon_thunk(ptr %c.var), !dbg !14
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %.loc9_18.2.temp), !dbg !11
-// CHECK:STDOUT:   call void @llvm.memcpy.p0.p0.i64(ptr align 1 %.loc9_18.2.temp, ptr align 1 @C.val.loc9_18.3, i64 0, i1 false), !dbg !11
-// CHECK:STDOUT:   call void @_Z9TakeCRRefO1C.carbon_thunk(ptr %.loc9_18.2.temp), !dbg !15
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %.loc19_18.2.temp), !dbg !11
+// CHECK:STDOUT:   call void @llvm.memcpy.p0.p0.i64(ptr align 1 %.loc19_18.2.temp, ptr align 1 @C.val.loc19_18.3, i64 0, i1 false), !dbg !11
+// CHECK:STDOUT:   call void @_Z9TakeCRRefO1C.carbon_thunk(ptr %.loc19_18.2.temp), !dbg !15
 // CHECK:STDOUT:   call void @_Z13TakeConstCRefRK1C.carbon_thunk(ptr %c.var), !dbg !16
 // CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %n.var), !dbg !12
 // CHECK:STDOUT:   call void @_Z10TakeIntRefRi.carbon_thunk(ptr %n.var), !dbg !17
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %.loc14_22.3.temp), !dbg !13
-// CHECK:STDOUT:   store i32 42, ptr %.loc14_22.3.temp, align 4, !dbg !13
-// CHECK:STDOUT:   call void @_Z11TakeIntRRefOi.carbon_thunk(ptr %.loc14_22.3.temp), !dbg !18
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %.loc24_22.3.temp), !dbg !13
+// CHECK:STDOUT:   store i32 42, ptr %.loc24_22.3.temp, align 4, !dbg !13
+// CHECK:STDOUT:   call void @_Z11TakeIntRRefOi.carbon_thunk(ptr %.loc24_22.3.temp), !dbg !18
 // CHECK:STDOUT:   call void @_Z15TakeConstIntRefRKi.carbon_thunk(ptr %n.var), !dbg !19
 // CHECK:STDOUT:   ret void, !dbg !20
 // CHECK:STDOUT: }
@@ -164,17 +196,108 @@ fn PassRefs() {
 // CHECK:STDOUT: !4 = !{i32 7, !"PIE Level", i32 2}
 // CHECK:STDOUT: !5 = distinct !DICompileUnit(language: DW_LANG_C, file: !6, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !6 = !DIFile(filename: "pass_references.carbon", directory: "")
-// CHECK:STDOUT: !7 = distinct !DISubprogram(name: "PassRefs", linkageName: "_CPassRefs.Main", scope: null, file: !6, line: 6, type: !8, spFlags: DISPFlagDefinition, unit: !5)
+// CHECK:STDOUT: !7 = distinct !DISubprogram(name: "PassRefs", linkageName: "_CPassRefs.Main", scope: null, file: !6, line: 16, type: !8, spFlags: DISPFlagDefinition, unit: !5)
 // CHECK:STDOUT: !8 = !DISubroutineType(types: !9)
 // CHECK:STDOUT: !9 = !{}
-// CHECK:STDOUT: !10 = !DILocation(line: 7, column: 3, scope: !7)
-// CHECK:STDOUT: !11 = !DILocation(line: 9, column: 17, scope: !7)
-// CHECK:STDOUT: !12 = !DILocation(line: 12, column: 3, scope: !7)
-// CHECK:STDOUT: !13 = !DILocation(line: 14, column: 19, scope: !7)
-// CHECK:STDOUT: !14 = !DILocation(line: 8, column: 3, scope: !7)
-// CHECK:STDOUT: !15 = !DILocation(line: 9, column: 3, scope: !7)
-// CHECK:STDOUT: !16 = !DILocation(line: 10, column: 3, scope: !7)
-// CHECK:STDOUT: !17 = !DILocation(line: 13, column: 3, scope: !7)
-// CHECK:STDOUT: !18 = !DILocation(line: 14, column: 3, scope: !7)
-// CHECK:STDOUT: !19 = !DILocation(line: 15, column: 3, scope: !7)
-// CHECK:STDOUT: !20 = !DILocation(line: 6, column: 1, scope: !7)
+// CHECK:STDOUT: !10 = !DILocation(line: 17, column: 3, scope: !7)
+// CHECK:STDOUT: !11 = !DILocation(line: 19, column: 17, scope: !7)
+// CHECK:STDOUT: !12 = !DILocation(line: 22, column: 3, scope: !7)
+// CHECK:STDOUT: !13 = !DILocation(line: 24, column: 19, scope: !7)
+// CHECK:STDOUT: !14 = !DILocation(line: 18, column: 3, scope: !7)
+// CHECK:STDOUT: !15 = !DILocation(line: 19, column: 3, scope: !7)
+// CHECK:STDOUT: !16 = !DILocation(line: 20, column: 3, scope: !7)
+// CHECK:STDOUT: !17 = !DILocation(line: 23, column: 3, scope: !7)
+// CHECK:STDOUT: !18 = !DILocation(line: 24, column: 3, scope: !7)
+// CHECK:STDOUT: !19 = !DILocation(line: 25, column: 3, scope: !7)
+// CHECK:STDOUT: !20 = !DILocation(line: 16, column: 1, scope: !7)
+// CHECK:STDOUT: ; ModuleID = 'return_references.carbon'
+// CHECK:STDOUT: source_filename = "return_references.carbon"
+// CHECK:STDOUT: target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128"
+// CHECK:STDOUT: target triple = "x86_64-unknown-linux-gnu"
+// CHECK:STDOUT:
+// CHECK:STDOUT: define void @_CGetRefs.Main() !dbg !7 {
+// CHECK:STDOUT: entry:
+// CHECK:STDOUT:   %c1.var = alloca ptr, align 8, !dbg !10
+// CHECK:STDOUT:   %c2.var = alloca {}, align 8, !dbg !11
+// CHECK:STDOUT:   %c3.var = alloca ptr, align 8, !dbg !12
+// CHECK:STDOUT:   %n1.var = alloca ptr, align 8, !dbg !13
+// CHECK:STDOUT:   %n2.var = alloca i32, align 4, !dbg !14
+// CHECK:STDOUT:   %n3.var = alloca ptr, align 8, !dbg !15
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %c1.var), !dbg !10
+// CHECK:STDOUT:   %ReturnCRef.call = call ptr @_Z10ReturnCRefv(), !dbg !16
+// CHECK:STDOUT:   store ptr %ReturnCRef.call, ptr %c1.var, align 8, !dbg !10
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %c2.var), !dbg !11
+// CHECK:STDOUT:   call void @_Z11ReturnCRRefv.carbon_thunk(ptr %c2.var), !dbg !17
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %c3.var), !dbg !12
+// CHECK:STDOUT:   %ReturnConstCRef.call = call ptr @_Z15ReturnConstCRefv(), !dbg !18
+// CHECK:STDOUT:   store ptr %ReturnConstCRef.call, ptr %c3.var, align 8, !dbg !12
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %n1.var), !dbg !13
+// CHECK:STDOUT:   %ReturnIntRef.call = call ptr @_Z12ReturnIntRefv(), !dbg !19
+// CHECK:STDOUT:   store ptr %ReturnIntRef.call, ptr %n1.var, align 8, !dbg !13
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %n2.var), !dbg !14
+// CHECK:STDOUT:   %ReturnIntRRef.call = call i32 @_Z13ReturnIntRRefv(), !dbg !20
+// CHECK:STDOUT:   store i32 %ReturnIntRRef.call, ptr %n2.var, align 4, !dbg !14
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %n3.var), !dbg !15
+// CHECK:STDOUT:   %ReturnConstIntRef.call = call ptr @_Z17ReturnConstIntRefv(), !dbg !21
+// CHECK:STDOUT:   store ptr %ReturnConstIntRef.call, ptr %n3.var, align 8, !dbg !15
+// CHECK:STDOUT:   ret void, !dbg !22
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: declare ptr @_Z10ReturnCRefv()
+// CHECK:STDOUT:
+// CHECK:STDOUT: declare ptr @_Z15ReturnConstCRefv()
+// CHECK:STDOUT:
+// CHECK:STDOUT: declare ptr @_Z12ReturnIntRefv()
+// CHECK:STDOUT:
+// CHECK:STDOUT: declare i32 @_Z13ReturnIntRRefv()
+// CHECK:STDOUT:
+// CHECK:STDOUT: declare ptr @_Z17ReturnConstIntRefv()
+// CHECK:STDOUT:
+// CHECK:STDOUT: ; Function Attrs: nocallback nofree nosync nounwind willreturn memory(argmem: readwrite)
+// CHECK:STDOUT: declare void @llvm.lifetime.start.p0(ptr captures(none)) #0
+// CHECK:STDOUT:
+// CHECK:STDOUT: ; Function Attrs: alwaysinline mustprogress
+// CHECK:STDOUT: define dso_local void @_Z11ReturnCRRefv.carbon_thunk(ptr %return) #1 {
+// CHECK:STDOUT: entry:
+// CHECK:STDOUT:   %return.addr = alloca ptr, align 8
+// CHECK:STDOUT:   store ptr %return, ptr %return.addr, align 8
+// CHECK:STDOUT:   %0 = load ptr, ptr %return.addr, align 8
+// CHECK:STDOUT:   %call = call nonnull align 1 dereferenceable(1) ptr @_Z11ReturnCRRefv()
+// CHECK:STDOUT:   ret void
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: declare nonnull align 1 dereferenceable(1) ptr @_Z11ReturnCRRefv() #2
+// CHECK:STDOUT:
+// CHECK:STDOUT: ; uselistorder directives
+// CHECK:STDOUT: uselistorder ptr @llvm.lifetime.start.p0, { 5, 4, 3, 2, 1, 0 }
+// CHECK:STDOUT:
+// CHECK:STDOUT: attributes #0 = { nocallback nofree nosync nounwind willreturn memory(argmem: readwrite) }
+// CHECK:STDOUT: attributes #1 = { alwaysinline mustprogress "min-legal-vector-width"="0" "no-trapping-math"="true" "stack-protector-buffer-size"="0" "target-cpu"="x86-64" "target-features"="+cmov,+cx8,+fxsr,+mmx,+sse,+sse2,+x87" "tune-cpu"="generic" }
+// CHECK:STDOUT: attributes #2 = { "no-trapping-math"="true" "stack-protector-buffer-size"="0" "target-cpu"="x86-64" "target-features"="+cmov,+cx8,+fxsr,+mmx,+sse,+sse2,+x87" "tune-cpu"="generic" }
+// CHECK:STDOUT:
+// CHECK:STDOUT: !llvm.module.flags = !{!0, !1, !2, !3, !4}
+// CHECK:STDOUT: !llvm.dbg.cu = !{!5}
+// CHECK:STDOUT:
+// CHECK:STDOUT: !0 = !{i32 7, !"Dwarf Version", i32 5}
+// CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
+// CHECK:STDOUT: !2 = !{i32 1, !"wchar_size", i32 4}
+// CHECK:STDOUT: !3 = !{i32 8, !"PIC Level", i32 0}
+// CHECK:STDOUT: !4 = !{i32 7, !"PIE Level", i32 2}
+// CHECK:STDOUT: !5 = distinct !DICompileUnit(language: DW_LANG_C, file: !6, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
+// CHECK:STDOUT: !6 = !DIFile(filename: "return_references.carbon", directory: "")
+// CHECK:STDOUT: !7 = distinct !DISubprogram(name: "GetRefs", linkageName: "_CGetRefs.Main", scope: null, file: !6, line: 16, type: !8, spFlags: DISPFlagDefinition, unit: !5)
+// CHECK:STDOUT: !8 = !DISubroutineType(types: !9)
+// CHECK:STDOUT: !9 = !{}
+// CHECK:STDOUT: !10 = !DILocation(line: 17, column: 3, scope: !7)
+// CHECK:STDOUT: !11 = !DILocation(line: 18, column: 3, scope: !7)
+// CHECK:STDOUT: !12 = !DILocation(line: 19, column: 3, scope: !7)
+// CHECK:STDOUT: !13 = !DILocation(line: 21, column: 3, scope: !7)
+// CHECK:STDOUT: !14 = !DILocation(line: 22, column: 3, scope: !7)
+// CHECK:STDOUT: !15 = !DILocation(line: 23, column: 3, scope: !7)
+// CHECK:STDOUT: !16 = !DILocation(line: 17, column: 20, scope: !7)
+// CHECK:STDOUT: !17 = !DILocation(line: 18, column: 19, scope: !7)
+// CHECK:STDOUT: !18 = !DILocation(line: 19, column: 26, scope: !7)
+// CHECK:STDOUT: !19 = !DILocation(line: 21, column: 18, scope: !7)
+// CHECK:STDOUT: !20 = !DILocation(line: 22, column: 17, scope: !7)
+// CHECK:STDOUT: !21 = !DILocation(line: 23, column: 24, scope: !7)
+// CHECK:STDOUT: !22 = !DILocation(line: 16, column: 1, scope: !7)