diff --git a/toolchain/lower/testdata/array/array_in_place.carbon b/toolchain/lower/testdata/array/array_in_place.carbon
index 7de8ee944519..9e3d59cc3957 100644
--- a/toolchain/lower/testdata/array/array_in_place.carbon
+++ b/toolchain/lower/testdata/array/array_in_place.carbon
@@ -13,7 +13,7 @@
 fn F() -> (i32, i32, i32);
 
 fn G() {
-  var v: array((i32, i32, i32), 2) = (F(), F());
+  var _: array((i32, i32, i32), 2) = (F(), F());
 }
 
 // CHECK:STDOUT: ; ModuleID = 'array_in_place.carbon'
@@ -24,11 +24,11 @@ fn G() {
 // CHECK:STDOUT: ; Function Attrs: nounwind
 // CHECK:STDOUT: define void @_CG.Main() #0 !dbg !4 {
 // CHECK:STDOUT: entry:
-// CHECK:STDOUT:   %v.var = alloca [2 x { i32, i32, i32 }], align 8, !dbg !7
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %v.var), !dbg !7
-// CHECK:STDOUT:   %.loc16_47.6.array.index = getelementptr inbounds [2 x { i32, i32, i32 }], ptr %v.var, i32 0, i64 0, !dbg !8
+// CHECK:STDOUT:   %_.var = alloca [2 x { i32, i32, i32 }], align 8, !dbg !7
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var), !dbg !7
+// CHECK:STDOUT:   %.loc16_47.6.array.index = getelementptr inbounds [2 x { i32, i32, i32 }], ptr %_.var, i32 0, i64 0, !dbg !8
 // CHECK:STDOUT:   call void @_CF.Main(ptr %.loc16_47.6.array.index), !dbg !9
-// CHECK:STDOUT:   %.loc16_47.5.array.index = getelementptr inbounds [2 x { i32, i32, i32 }], ptr %v.var, i32 0, i64 1, !dbg !8
+// CHECK:STDOUT:   %.loc16_47.5.array.index = getelementptr inbounds [2 x { i32, i32, i32 }], ptr %_.var, i32 0, i64 1, !dbg !8
 // CHECK:STDOUT:   call void @_CF.Main(ptr %.loc16_47.5.array.index), !dbg !10
 // CHECK:STDOUT:   ret void, !dbg !11
 // CHECK:STDOUT: }
diff --git a/toolchain/lower/testdata/array/assign_return_value.carbon b/toolchain/lower/testdata/array/assign_return_value.carbon
index a931de1cc27b..0776a107354b 100644
--- a/toolchain/lower/testdata/array/assign_return_value.carbon
+++ b/toolchain/lower/testdata/array/assign_return_value.carbon
@@ -13,7 +13,7 @@
 fn F() -> (i32, i32) { return (12, 24); }
 
 fn Run() {
-  var t: array(i32, 2) = F();
+  var _: array(i32, 2) = F();
 }
 
 // CHECK:STDOUT: ; ModuleID = 'assign_return_value.carbon'
@@ -33,18 +33,18 @@ fn Run() {
 // CHECK:STDOUT: ; Function Attrs: nounwind
 // CHECK:STDOUT: define void @main() #0 !dbg !10 {
 // CHECK:STDOUT: entry:
-// CHECK:STDOUT:   %t.var = alloca [2 x i32], align 4, !dbg !13
+// CHECK:STDOUT:   %_.var = alloca [2 x i32], align 4, !dbg !13
 // CHECK:STDOUT:   %.loc16_28.1.temp = alloca { i32, i32 }, align 8, !dbg !14
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %t.var), !dbg !13
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var), !dbg !13
 // CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %.loc16_28.1.temp), !dbg !14
 // CHECK:STDOUT:   call void @_CF.Main(ptr %.loc16_28.1.temp), !dbg !14
 // CHECK:STDOUT:   %tuple.elem0.tuple.elem = getelementptr inbounds nuw { i32, i32 }, ptr %.loc16_28.1.temp, i32 0, i32 0, !dbg !14
 // CHECK:STDOUT:   %.loc16_28.3 = load i32, ptr %tuple.elem0.tuple.elem, align 4, !dbg !14
-// CHECK:STDOUT:   %.loc16_28.4.array.index = getelementptr inbounds [2 x i32], ptr %t.var, i32 0, i64 0, !dbg !14
+// CHECK:STDOUT:   %.loc16_28.4.array.index = getelementptr inbounds [2 x i32], ptr %_.var, i32 0, i64 0, !dbg !14
 // CHECK:STDOUT:   store i32 %.loc16_28.3, ptr %.loc16_28.4.array.index, align 4, !dbg !14
 // CHECK:STDOUT:   %tuple.elem1.tuple.elem = getelementptr inbounds nuw { i32, i32 }, ptr %.loc16_28.1.temp, i32 0, i32 1, !dbg !14
 // CHECK:STDOUT:   %.loc16_28.6 = load i32, ptr %tuple.elem1.tuple.elem, align 4, !dbg !14
-// CHECK:STDOUT:   %.loc16_28.7.array.index = getelementptr inbounds [2 x i32], ptr %t.var, i32 0, i64 1, !dbg !14
+// CHECK:STDOUT:   %.loc16_28.7.array.index = getelementptr inbounds [2 x i32], ptr %_.var, i32 0, i64 1, !dbg !14
 // CHECK:STDOUT:   store i32 %.loc16_28.6, ptr %.loc16_28.7.array.index, align 4, !dbg !14
 // CHECK:STDOUT:   ret void, !dbg !15
 // CHECK:STDOUT: }
diff --git a/toolchain/lower/testdata/array/base.carbon b/toolchain/lower/testdata/array/base.carbon
index 18e3ca953e32..6f3cc78f0519 100644
--- a/toolchain/lower/testdata/array/base.carbon
+++ b/toolchain/lower/testdata/array/base.carbon
@@ -11,11 +11,11 @@
 // TIP:   bazel run //toolchain/testing:file_test -- --dump_output --file_tests=toolchain/lower/testdata/array/base.carbon
 
 fn Run() {
-  var a: array(i32, 1) = (1,);
-  var b: array(f64, 2) = (11.1, 2.2,);
-  var c: array((), 5) = ((), (), (), (), (),);
+  var _: array(i32, 1) = (1,);
+  var _: array(f64, 2) = (11.1, 2.2,);
+  var _: array((), 5) = ((), (), (), (), (),);
   var d: (i32, i32, i32) = (1, 2, 3);
-  var e: array(i32, 3) = d;
+  var _: array(i32, 3) = d;
 }
 
 // CHECK:STDOUT: ; ModuleID = 'base.carbon'
@@ -29,42 +29,42 @@ fn Run() {
 // CHECK:STDOUT: ; Function Attrs: nounwind
 // CHECK:STDOUT: define void @main() #0 !dbg !4 {
 // CHECK:STDOUT: entry:
-// CHECK:STDOUT:   %a.var = alloca [1 x i32], align 4, !dbg !7
-// CHECK:STDOUT:   %b.var = alloca [2 x double], align 8, !dbg !8
-// CHECK:STDOUT:   %c.var = alloca [5 x {}], align 8, !dbg !9
+// CHECK:STDOUT:   %_.var.loc14 = alloca [1 x i32], align 4, !dbg !7
+// CHECK:STDOUT:   %_.var.loc15 = alloca [2 x double], align 8, !dbg !8
+// CHECK:STDOUT:   %_.var.loc16 = alloca [5 x {}], align 8, !dbg !9
 // CHECK:STDOUT:   %d.var = alloca { i32, i32, i32 }, align 8, !dbg !10
-// CHECK:STDOUT:   %e.var = alloca [3 x i32], align 4, !dbg !11
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %a.var), !dbg !7
-// CHECK:STDOUT:   %.loc14_29.3.array.index = getelementptr inbounds [1 x i32], ptr %a.var, i32 0, i64 0, !dbg !12
-// CHECK:STDOUT:   call void @llvm.memcpy.p0.p0.i64(ptr align 4 %a.var, ptr align 4 @array.237.loc14_3, i64 4, i1 false), !dbg !7
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %b.var), !dbg !8
-// CHECK:STDOUT:   %.loc15_37.3.array.index = getelementptr inbounds [2 x double], ptr %b.var, i32 0, i64 0, !dbg !13
-// CHECK:STDOUT:   %.loc15_37.6.array.index = getelementptr inbounds [2 x double], ptr %b.var, i32 0, i64 1, !dbg !13
-// CHECK:STDOUT:   call void @llvm.memcpy.p0.p0.i64(ptr align 8 %b.var, ptr align 8 @array.b91.loc15_3, i64 16, i1 false), !dbg !8
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %c.var), !dbg !9
-// CHECK:STDOUT:   %.loc16_45.2.array.index = getelementptr inbounds [5 x {}], ptr %c.var, i32 0, i64 0, !dbg !14
-// CHECK:STDOUT:   %.loc16_45.4.array.index = getelementptr inbounds [5 x {}], ptr %c.var, i32 0, i64 1, !dbg !14
-// CHECK:STDOUT:   %.loc16_45.6.array.index = getelementptr inbounds [5 x {}], ptr %c.var, i32 0, i64 2, !dbg !14
-// CHECK:STDOUT:   %.loc16_45.8.array.index = getelementptr inbounds [5 x {}], ptr %c.var, i32 0, i64 3, !dbg !14
-// CHECK:STDOUT:   %.loc16_45.10.array.index = getelementptr inbounds [5 x {}], ptr %c.var, i32 0, i64 4, !dbg !14
-// CHECK:STDOUT:   call void @llvm.memcpy.p0.p0.i64(ptr align 1 %c.var, ptr align 1 @array.1cb.loc16_3, i64 0, i1 false), !dbg !9
+// CHECK:STDOUT:   %_.var.loc18 = alloca [3 x i32], align 4, !dbg !11
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var.loc14), !dbg !7
+// CHECK:STDOUT:   %.loc14_29.3.array.index = getelementptr inbounds [1 x i32], ptr %_.var.loc14, i32 0, i64 0, !dbg !12
+// CHECK:STDOUT:   call void @llvm.memcpy.p0.p0.i64(ptr align 4 %_.var.loc14, ptr align 4 @array.237.loc14_3, i64 4, i1 false), !dbg !7
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var.loc15), !dbg !8
+// CHECK:STDOUT:   %.loc15_37.3.array.index = getelementptr inbounds [2 x double], ptr %_.var.loc15, i32 0, i64 0, !dbg !13
+// CHECK:STDOUT:   %.loc15_37.6.array.index = getelementptr inbounds [2 x double], ptr %_.var.loc15, i32 0, i64 1, !dbg !13
+// CHECK:STDOUT:   call void @llvm.memcpy.p0.p0.i64(ptr align 8 %_.var.loc15, ptr align 8 @array.b91.loc15_3, i64 16, i1 false), !dbg !8
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var.loc16), !dbg !9
+// CHECK:STDOUT:   %.loc16_45.2.array.index = getelementptr inbounds [5 x {}], ptr %_.var.loc16, i32 0, i64 0, !dbg !14
+// CHECK:STDOUT:   %.loc16_45.4.array.index = getelementptr inbounds [5 x {}], ptr %_.var.loc16, i32 0, i64 1, !dbg !14
+// CHECK:STDOUT:   %.loc16_45.6.array.index = getelementptr inbounds [5 x {}], ptr %_.var.loc16, i32 0, i64 2, !dbg !14
+// CHECK:STDOUT:   %.loc16_45.8.array.index = getelementptr inbounds [5 x {}], ptr %_.var.loc16, i32 0, i64 3, !dbg !14
+// CHECK:STDOUT:   %.loc16_45.10.array.index = getelementptr inbounds [5 x {}], ptr %_.var.loc16, i32 0, i64 4, !dbg !14
+// CHECK:STDOUT:   call void @llvm.memcpy.p0.p0.i64(ptr align 1 %_.var.loc16, ptr align 1 @array.1cb.loc16_3, i64 0, i1 false), !dbg !9
 // CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %d.var), !dbg !10
 // CHECK:STDOUT:   %tuple.elem0.loc17.tuple.elem = getelementptr inbounds nuw { i32, i32, i32 }, ptr %d.var, i32 0, i32 0, !dbg !15
 // CHECK:STDOUT:   %tuple.elem1.loc17.tuple.elem = getelementptr inbounds nuw { i32, i32, i32 }, ptr %d.var, i32 0, i32 1, !dbg !15
 // CHECK:STDOUT:   %tuple.elem2.loc17.tuple.elem = getelementptr inbounds nuw { i32, i32, i32 }, ptr %d.var, i32 0, i32 2, !dbg !15
 // CHECK:STDOUT:   call void @llvm.memcpy.p0.p0.i64(ptr align 4 %d.var, ptr align 4 @tuple.ee6.loc17_3, i64 12, i1 false), !dbg !10
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %e.var), !dbg !11
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var.loc18), !dbg !11
 // CHECK:STDOUT:   %tuple.elem0.loc18.tuple.elem = getelementptr inbounds nuw { i32, i32, i32 }, ptr %d.var, i32 0, i32 0, !dbg !16
 // CHECK:STDOUT:   %.loc18_26.1 = load i32, ptr %tuple.elem0.loc18.tuple.elem, align 4, !dbg !16
-// CHECK:STDOUT:   %.loc18_26.2.array.index = getelementptr inbounds [3 x i32], ptr %e.var, i32 0, i64 0, !dbg !16
+// CHECK:STDOUT:   %.loc18_26.2.array.index = getelementptr inbounds [3 x i32], ptr %_.var.loc18, i32 0, i64 0, !dbg !16
 // CHECK:STDOUT:   store i32 %.loc18_26.1, ptr %.loc18_26.2.array.index, align 4, !dbg !16
 // CHECK:STDOUT:   %tuple.elem1.loc18.tuple.elem = getelementptr inbounds nuw { i32, i32, i32 }, ptr %d.var, i32 0, i32 1, !dbg !16
 // CHECK:STDOUT:   %.loc18_26.4 = load i32, ptr %tuple.elem1.loc18.tuple.elem, align 4, !dbg !16
-// CHECK:STDOUT:   %.loc18_26.5.array.index = getelementptr inbounds [3 x i32], ptr %e.var, i32 0, i64 1, !dbg !16
+// CHECK:STDOUT:   %.loc18_26.5.array.index = getelementptr inbounds [3 x i32], ptr %_.var.loc18, i32 0, i64 1, !dbg !16
 // CHECK:STDOUT:   store i32 %.loc18_26.4, ptr %.loc18_26.5.array.index, align 4, !dbg !16
 // CHECK:STDOUT:   %tuple.elem2.loc18.tuple.elem = getelementptr inbounds nuw { i32, i32, i32 }, ptr %d.var, i32 0, i32 2, !dbg !16
 // CHECK:STDOUT:   %.loc18_26.7 = load i32, ptr %tuple.elem2.loc18.tuple.elem, align 4, !dbg !16
-// CHECK:STDOUT:   %.loc18_26.8.array.index = getelementptr inbounds [3 x i32], ptr %e.var, i32 0, i64 2, !dbg !16
+// CHECK:STDOUT:   %.loc18_26.8.array.index = getelementptr inbounds [3 x i32], ptr %_.var.loc18, i32 0, i64 2, !dbg !16
 // CHECK:STDOUT:   store i32 %.loc18_26.7, ptr %.loc18_26.8.array.index, align 4, !dbg !16
 // CHECK:STDOUT:   ret void, !dbg !17
 // CHECK:STDOUT: }
diff --git a/toolchain/lower/testdata/builtins/maybe_unformed.carbon b/toolchain/lower/testdata/builtins/maybe_unformed.carbon
index 495f2428c8b0..bc0853d49a9c 100644
--- a/toolchain/lower/testdata/builtins/maybe_unformed.carbon
+++ b/toolchain/lower/testdata/builtins/maybe_unformed.carbon
@@ -12,10 +12,10 @@
 
 fn MaybeUnformedBuiltin(t: type) -> type = "maybe_unformed.make_type";
 
-fn TakeI32(x: MaybeUnformedBuiltin(i32)) {}
+fn TakeI32(_: MaybeUnformedBuiltin(i32)) {}
 fn MakeI32() -> MaybeUnformedBuiltin(i32);
 
-fn TakeBool(x: MaybeUnformedBuiltin(bool)) {}
+fn TakeBool(_: MaybeUnformedBuiltin(bool)) {}
 fn MakeBool() -> MaybeUnformedBuiltin(bool);
 
 fn PassI32() {
@@ -39,7 +39,7 @@ class MaybeUnformedAdapter(T:! type) {
   adapt MaybeUnformedBuiltin(T);
 }
 
-fn TakeAdapterI32(x: MaybeUnformedAdapter(i32)) {}
+fn TakeAdapterI32(_: MaybeUnformedAdapter(i32)) {}
 fn MakeAdapterI32() -> MaybeUnformedAdapter(i32);
 
 fn PassAdapterI32() {
@@ -48,7 +48,7 @@ fn PassAdapterI32() {
   TakeAdapterI32(MakeAdapterI32());
 }
 
-fn TakeAdapterBool(x: MaybeUnformedAdapter(bool)) {}
+fn TakeAdapterBool(_: MaybeUnformedAdapter(bool)) {}
 fn MakeAdapterBool() -> MaybeUnformedAdapter(bool);
 
 fn PassAdapterBool() {
@@ -59,7 +59,7 @@ fn PassAdapterBool() {
 // CHECK:STDOUT: source_filename = "maybe_unformed.carbon"
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
-// CHECK:STDOUT: define void @_CTakeI32.Main(i32 %x) #0 !dbg !4 {
+// CHECK:STDOUT: define void @_CTakeI32.Main(i32 %_) #0 !dbg !4 {
 // CHECK:STDOUT: entry:
 // CHECK:STDOUT:   ret void, !dbg !10
 // CHECK:STDOUT: }
@@ -67,7 +67,7 @@ fn PassAdapterBool() {
 // CHECK:STDOUT: declare i32 @_CMakeI32.Main()
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
-// CHECK:STDOUT: define void @_CTakeBool.Main(ptr %x) #0 !dbg !11 {
+// CHECK:STDOUT: define void @_CTakeBool.Main(ptr %_) #0 !dbg !11 {
 // CHECK:STDOUT: entry:
 // CHECK:STDOUT:   ret void, !dbg !17
 // CHECK:STDOUT: }
@@ -100,7 +100,7 @@ fn PassAdapterBool() {
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
-// CHECK:STDOUT: define void @_CTakeAdapterI32.Main(i32 %x) #0 !dbg !33 {
+// CHECK:STDOUT: define void @_CTakeAdapterI32.Main(i32 %_) #0 !dbg !33 {
 // CHECK:STDOUT: entry:
 // CHECK:STDOUT:   ret void, !dbg !36
 // CHECK:STDOUT: }
@@ -120,7 +120,7 @@ fn PassAdapterBool() {
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
-// CHECK:STDOUT: define void @_CTakeAdapterBool.Main(ptr %x) #0 !dbg !41 {
+// CHECK:STDOUT: define void @_CTakeAdapterBool.Main(ptr %_) #0 !dbg !41 {
 // CHECK:STDOUT: entry:
 // CHECK:STDOUT:   ret void, !dbg !44
 // CHECK:STDOUT: }
diff --git a/toolchain/lower/testdata/builtins/type.carbon b/toolchain/lower/testdata/builtins/type.carbon
index 0edde3c40c65..044d7823cd35 100644
--- a/toolchain/lower/testdata/builtins/type.carbon
+++ b/toolchain/lower/testdata/builtins/type.carbon
@@ -16,7 +16,7 @@ library "[[@TEST_NAME]]";
 fn CanDestroy() -> type = "type.can_destroy";
 
 fn F() {
-  let t: type = CanDestroy();
+  let _: type = CanDestroy();
 }
 
 // --- destroy.carbon
diff --git a/toolchain/lower/testdata/class/basic.carbon b/toolchain/lower/testdata/class/basic.carbon
index 170a4d699c00..a0d4b7f3543d 100644
--- a/toolchain/lower/testdata/class/basic.carbon
+++ b/toolchain/lower/testdata/class/basic.carbon
@@ -19,7 +19,7 @@ fn F(c: C) -> C;
 
 fn Run() {
   var c: C;
-  var d: C = F(c);
+  var _: C = F(c);
 }
 
 // CHECK:STDOUT: ; ModuleID = 'basic.carbon'
@@ -31,10 +31,10 @@ fn Run() {
 // CHECK:STDOUT: define void @main() #0 !dbg !4 {
 // CHECK:STDOUT: entry:
 // CHECK:STDOUT:   %c.var = alloca { i32, ptr }, align 8, !dbg !7
-// CHECK:STDOUT:   %d.var = alloca { i32, ptr }, align 8, !dbg !8
+// CHECK:STDOUT:   %_.var = alloca { i32, ptr }, align 8, !dbg !8
 // CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %c.var), !dbg !7
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %d.var), !dbg !8
-// CHECK:STDOUT:   call void @_CF.Main(ptr %d.var, ptr %c.var), !dbg !9
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var), !dbg !8
+// CHECK:STDOUT:   call void @_CF.Main(ptr %_.var, ptr %c.var), !dbg !9
 // CHECK:STDOUT:   ret void, !dbg !10
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
diff --git a/toolchain/lower/testdata/class/convert.carbon b/toolchain/lower/testdata/class/convert.carbon
index c7573c0b5dad..3d6c9161a7bb 100644
--- a/toolchain/lower/testdata/class/convert.carbon
+++ b/toolchain/lower/testdata/class/convert.carbon
@@ -18,7 +18,7 @@ impl IntWrapper as Core.ImplicitAs(i32) {
   fn Convert[self: Self]() -> i32 { return self.n; }
 }
 
-fn Consume(n: i32) {}
+fn Consume(_: i32) {}
 
 fn DoIt() {
   var w: IntWrapper = {.n = 42};
@@ -39,7 +39,7 @@ fn DoIt() {
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
-// CHECK:STDOUT: define void @_CConsume.Main(i32 %n) #0 !dbg !13 {
+// CHECK:STDOUT: define void @_CConsume.Main(i32 %_) #0 !dbg !13 {
 // CHECK:STDOUT: entry:
 // CHECK:STDOUT:   ret void, !dbg !18
 // CHECK:STDOUT: }
diff --git a/toolchain/lower/testdata/class/field.carbon b/toolchain/lower/testdata/class/field.carbon
index 2fce2f415a96..c9079de02a5a 100644
--- a/toolchain/lower/testdata/class/field.carbon
+++ b/toolchain/lower/testdata/class/field.carbon
@@ -45,7 +45,7 @@ fn Run() {
   var o: Other;
   // .a is initialized with a non-constant expression
   // .b is initialized with in-place class_init
-  var u: Use = {.a = &o, .b = {}};
+  var _: Use = {.a = &o, .b = {}};
 }
 
 // --- implicit_init_with_nonempty_nonconst.carbon
@@ -65,7 +65,7 @@ fn Run() {
   var o: Other;
   // .a is initialized with a non-constant expression
   // .b is initialized with in-place class_init
-  var u: Use = {.a = &o, .b = {.v = 42}};
+  var _: Use = {.a = &o, .b = {.v = 42}};
 }
 
 // CHECK:STDOUT: ; ModuleID = 'basic.carbon'
@@ -134,12 +134,12 @@ fn Run() {
 // CHECK:STDOUT: define void @main() #0 !dbg !4 {
 // CHECK:STDOUT: entry:
 // CHECK:STDOUT:   %o.var = alloca {}, align 8, !dbg !7
-// CHECK:STDOUT:   %u.var = alloca { ptr, {} }, align 8, !dbg !8
+// CHECK:STDOUT:   %_.var = alloca { ptr, {} }, align 8, !dbg !8
 // CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %o.var), !dbg !7
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %u.var), !dbg !8
-// CHECK:STDOUT:   %.loc15_33.2.a = getelementptr inbounds nuw { ptr, {} }, ptr %u.var, i32 0, i32 0, !dbg !9
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var), !dbg !8
+// CHECK:STDOUT:   %.loc15_33.2.a = getelementptr inbounds nuw { ptr, {} }, ptr %_.var, i32 0, i32 0, !dbg !9
 // CHECK:STDOUT:   store ptr %o.var, ptr %.loc15_33.2.a, align 8, !dbg !9
-// CHECK:STDOUT:   %.loc15_33.4.b = getelementptr inbounds nuw { ptr, {} }, ptr %u.var, i32 0, i32 1, !dbg !9
+// CHECK:STDOUT:   %.loc15_33.4.b = getelementptr inbounds nuw { ptr, {} }, ptr %_.var, i32 0, i32 1, !dbg !9
 // CHECK:STDOUT:   call void @llvm.memcpy.p0.p0.i64(ptr align 1 %.loc15_33.4.b, ptr align 1 @Other.val.loc15_33.5, i64 0, i1 false), !dbg !9
 // CHECK:STDOUT:   ret void, !dbg !10
 // CHECK:STDOUT: }
@@ -180,12 +180,12 @@ fn Run() {
 // CHECK:STDOUT: define void @main() #0 !dbg !4 {
 // CHECK:STDOUT: entry:
 // CHECK:STDOUT:   %o.var = alloca { i32 }, align 8, !dbg !7
-// CHECK:STDOUT:   %u.var = alloca { ptr, { i32 } }, align 8, !dbg !8
+// CHECK:STDOUT:   %_.var = alloca { ptr, { i32 } }, align 8, !dbg !8
 // CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %o.var), !dbg !7
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %u.var), !dbg !8
-// CHECK:STDOUT:   %.loc17_40.2.a = getelementptr inbounds nuw { ptr, { i32 } }, ptr %u.var, i32 0, i32 0, !dbg !9
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var), !dbg !8
+// CHECK:STDOUT:   %.loc17_40.2.a = getelementptr inbounds nuw { ptr, { i32 } }, ptr %_.var, i32 0, i32 0, !dbg !9
 // CHECK:STDOUT:   store ptr %o.var, ptr %.loc17_40.2.a, align 8, !dbg !9
-// CHECK:STDOUT:   %.loc17_40.4.b = getelementptr inbounds nuw { ptr, { i32 } }, ptr %u.var, i32 0, i32 1, !dbg !9
+// CHECK:STDOUT:   %.loc17_40.4.b = getelementptr inbounds nuw { ptr, { i32 } }, ptr %_.var, i32 0, i32 1, !dbg !9
 // CHECK:STDOUT:   %.loc17_39.3.v = getelementptr inbounds nuw { i32 }, ptr %.loc17_40.4.b, i32 0, i32 0, !dbg !10
 // CHECK:STDOUT:   call void @llvm.memcpy.p0.p0.i64(ptr align 4 %.loc17_40.4.b, ptr align 4 @Other.val.loc17_40.5, i64 4, i1 false), !dbg !9
 // CHECK:STDOUT:   ret void, !dbg !11
diff --git a/toolchain/lower/testdata/class/virtual.carbon b/toolchain/lower/testdata/class/virtual.carbon
index 4c7cefb67875..856f49aad4ef 100644
--- a/toolchain/lower/testdata/class/virtual.carbon
+++ b/toolchain/lower/testdata/class/virtual.carbon
@@ -34,12 +34,12 @@ package Create;
 import Classes;
 
 fn Create() {
-  var b: Classes.Base = {};
-  var i: Classes.Intermediate = {.base = {}};
-  var d: Classes.Derived = {.base = {.base = {}}};
+  var _: Classes.Base = {};
+  var _: Classes.Intermediate = {.base = {}};
+  var _: Classes.Derived = {.base = {.base = {}}};
   // Implicit initialization creates an object with the unformed state, which
   // doesn't include vptr initialization.
-  var d2: Classes.Derived;
+  var _: Classes.Derived;
 }
 
 fn Use(v: Classes.Intermediate*) {
@@ -59,7 +59,7 @@ fn Fn() {
   var i: i32 = 3;
   var v: Base = {.m = i};
   v.m = 5;
-  var u: Base = {.m = 3};
+  var _: Base = {.m = 3};
 }
 
 // --- member_brace_init.carbon
@@ -75,7 +75,7 @@ class Derived {
 }
 
 fn Use() {
-  var v : Derived = {.base = {}};
+  var _ : Derived = {.base = {}};
 }
 
 // --- call.carbon
@@ -122,7 +122,7 @@ library "[[@TEST_NAME]]";
 
 base class Base(T:! Core.Destroy) {
   virtual fn F[self: Self]() {
-    var v: T;
+    var _: T;
   }
 }
 
@@ -132,8 +132,8 @@ class T2 {
 }
 
 fn F() {
-  var t1: Base(T1) = {};
-  var t2: Base(T2) = {};
+  var _: Base(T1) = {};
+  var _: Base(T2) = {};
 }
 
 // --- generic_base.carbon
@@ -151,7 +151,7 @@ class Derived {
 }
 
 fn Make() {
-  var v: Derived;
+  var _: Derived;
 }
 
 // CHECK:STDOUT: ; ModuleID = 'classes.carbon'
@@ -204,22 +204,22 @@ fn Make() {
 // CHECK:STDOUT: ; Function Attrs: nounwind
 // CHECK:STDOUT: define void @_CCreate.Create() #0 !dbg !4 {
 // CHECK:STDOUT: entry:
-// CHECK:STDOUT:   %b.var = alloca {}, align 8, !dbg !7
-// CHECK:STDOUT:   %i.var = alloca { ptr, {} }, align 8, !dbg !8
-// CHECK:STDOUT:   %d.var = alloca { { ptr, {} } }, align 8, !dbg !9
-// CHECK:STDOUT:   %d2.var = alloca { { ptr, {} } }, align 8, !dbg !10
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %b.var), !dbg !7
-// CHECK:STDOUT:   call void @llvm.memcpy.p0.p0.i64(ptr align 1 %b.var, ptr align 1 @Base.val.loc7_3, i64 0, i1 false), !dbg !7
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %i.var), !dbg !8
-// CHECK:STDOUT:   %.loc8_44.2.vptr = getelementptr inbounds nuw { ptr, {} }, ptr %i.var, i32 0, i32 0, !dbg !11
-// CHECK:STDOUT:   %.loc8_44.4.base = getelementptr inbounds nuw { ptr, {} }, ptr %i.var, i32 0, i32 1, !dbg !11
-// CHECK:STDOUT:   call void @llvm.memcpy.p0.p0.i64(ptr align 8 %i.var, ptr align 8 @Intermediate.val.ec2.loc8_3, i64 8, i1 false), !dbg !8
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %d.var), !dbg !9
-// CHECK:STDOUT:   %.loc9_49.2.base = getelementptr inbounds nuw { { ptr, {} } }, ptr %d.var, i32 0, i32 0, !dbg !12
+// CHECK:STDOUT:   %_.var.loc7 = alloca {}, align 8, !dbg !7
+// CHECK:STDOUT:   %_.var.loc8 = alloca { ptr, {} }, align 8, !dbg !8
+// CHECK:STDOUT:   %_.var.loc9 = alloca { { ptr, {} } }, align 8, !dbg !9
+// CHECK:STDOUT:   %_.var.loc12 = alloca { { ptr, {} } }, align 8, !dbg !10
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var.loc7), !dbg !7
+// CHECK:STDOUT:   call void @llvm.memcpy.p0.p0.i64(ptr align 1 %_.var.loc7, ptr align 1 @Base.val.loc7_3, i64 0, i1 false), !dbg !7
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var.loc8), !dbg !8
+// CHECK:STDOUT:   %.loc8_44.2.vptr = getelementptr inbounds nuw { ptr, {} }, ptr %_.var.loc8, i32 0, i32 0, !dbg !11
+// CHECK:STDOUT:   %.loc8_44.4.base = getelementptr inbounds nuw { ptr, {} }, ptr %_.var.loc8, i32 0, i32 1, !dbg !11
+// CHECK:STDOUT:   call void @llvm.memcpy.p0.p0.i64(ptr align 8 %_.var.loc8, ptr align 8 @Intermediate.val.ec2.loc8_3, i64 8, i1 false), !dbg !8
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var.loc9), !dbg !9
+// CHECK:STDOUT:   %.loc9_49.2.base = getelementptr inbounds nuw { { ptr, {} } }, ptr %_.var.loc9, i32 0, i32 0, !dbg !12
 // CHECK:STDOUT:   %.loc9_48.2.vptr = getelementptr inbounds nuw { ptr, {} }, ptr %.loc9_49.2.base, i32 0, i32 0, !dbg !13
 // CHECK:STDOUT:   %.loc9_48.4.base = getelementptr inbounds nuw { ptr, {} }, ptr %.loc9_49.2.base, i32 0, i32 1, !dbg !13
-// CHECK:STDOUT:   call void @llvm.memcpy.p0.p0.i64(ptr align 8 %d.var, ptr align 8 @Derived.val.loc9_3, i64 8, i1 false), !dbg !9
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %d2.var), !dbg !10
+// CHECK:STDOUT:   call void @llvm.memcpy.p0.p0.i64(ptr align 8 %_.var.loc9, ptr align 8 @Derived.val.loc9_3, i64 8, i1 false), !dbg !9
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var.loc12), !dbg !10
 // CHECK:STDOUT:   ret void, !dbg !14
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
@@ -297,7 +297,7 @@ fn Make() {
 // CHECK:STDOUT: entry:
 // CHECK:STDOUT:   %i.var = alloca i32, align 4, !dbg !14
 // CHECK:STDOUT:   %v.var = alloca { ptr, i32 }, align 8, !dbg !15
-// CHECK:STDOUT:   %u.var = alloca { ptr, i32 }, align 8, !dbg !16
+// CHECK:STDOUT:   %_.var = alloca { ptr, i32 }, align 8, !dbg !16
 // CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %i.var), !dbg !14
 // CHECK:STDOUT:   store i32 3, ptr %i.var, align 4, !dbg !14
 // CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %v.var), !dbg !15
@@ -308,10 +308,10 @@ fn Make() {
 // CHECK:STDOUT:   store ptr @"_CBase.MemberInit.$vtable", ptr %.loc11_24.2.vptr, align 8, !dbg !17
 // CHECK:STDOUT:   %.loc12_4.m = getelementptr inbounds nuw { ptr, i32 }, ptr %v.var, i32 0, i32 1, !dbg !19
 // CHECK:STDOUT:   store i32 5, ptr %.loc12_4.m, align 4, !dbg !19
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %u.var), !dbg !16
-// CHECK:STDOUT:   %.loc13_24.2.vptr = getelementptr inbounds nuw { ptr, i32 }, ptr %u.var, i32 0, i32 0, !dbg !20
-// CHECK:STDOUT:   %.loc13_24.5.m = getelementptr inbounds nuw { ptr, i32 }, ptr %u.var, i32 0, i32 1, !dbg !20
-// CHECK:STDOUT:   call void @llvm.memcpy.p0.p0.i64(ptr align 8 %u.var, ptr align 8 @Base.val.loc13_3, i64 16, i1 false), !dbg !16
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var), !dbg !16
+// CHECK:STDOUT:   %.loc13_24.2.vptr = getelementptr inbounds nuw { ptr, i32 }, ptr %_.var, i32 0, i32 0, !dbg !20
+// CHECK:STDOUT:   %.loc13_24.5.m = getelementptr inbounds nuw { ptr, i32 }, ptr %_.var, i32 0, i32 1, !dbg !20
+// CHECK:STDOUT:   call void @llvm.memcpy.p0.p0.i64(ptr align 8 %_.var, ptr align 8 @Base.val.loc13_3, i64 16, i1 false), !dbg !16
 // CHECK:STDOUT:   ret void, !dbg !21
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
@@ -365,11 +365,11 @@ fn Make() {
 // CHECK:STDOUT: ; Function Attrs: nounwind
 // CHECK:STDOUT: define void @_CUse.Main() #0 !dbg !4 {
 // CHECK:STDOUT: entry:
-// CHECK:STDOUT:   %v.var = alloca { { ptr } }, align 8, !dbg !7
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %v.var), !dbg !7
-// CHECK:STDOUT:   %.loc13_32.2.base = getelementptr inbounds nuw { { ptr } }, ptr %v.var, i32 0, i32 0, !dbg !8
+// CHECK:STDOUT:   %_.var = alloca { { ptr } }, align 8, !dbg !7
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var), !dbg !7
+// CHECK:STDOUT:   %.loc13_32.2.base = getelementptr inbounds nuw { { ptr } }, ptr %_.var, i32 0, i32 0, !dbg !8
 // CHECK:STDOUT:   %.loc13_31.2.vptr = getelementptr inbounds nuw { ptr }, ptr %.loc13_32.2.base, i32 0, i32 0, !dbg !9
-// CHECK:STDOUT:   call void @llvm.memcpy.p0.p0.i64(ptr align 8 %v.var, ptr align 8 @Derived.val.loc13_3, i64 8, i1 false), !dbg !7
+// CHECK:STDOUT:   call void @llvm.memcpy.p0.p0.i64(ptr align 8 %_.var, ptr align 8 @Derived.val.loc13_3, i64 8, i1 false), !dbg !7
 // CHECK:STDOUT:   ret void, !dbg !10
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
@@ -509,30 +509,30 @@ fn Make() {
 // CHECK:STDOUT: ; Function Attrs: nounwind
 // CHECK:STDOUT: define void @_CF.Main() #0 !dbg !4 {
 // CHECK:STDOUT: entry:
-// CHECK:STDOUT:   %t1.var = alloca { ptr }, align 8, !dbg !7
-// CHECK:STDOUT:   %t2.var = alloca { ptr }, align 8, !dbg !8
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %t1.var), !dbg !7
-// CHECK:STDOUT:   %.loc16_23.2.vptr = getelementptr inbounds nuw { ptr }, ptr %t1.var, i32 0, i32 0, !dbg !9
-// CHECK:STDOUT:   call void @llvm.memcpy.p0.p0.i64(ptr align 8 %t1.var, ptr align 8 @Base.val.439.loc16_3, i64 8, i1 false), !dbg !7
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %t2.var), !dbg !8
-// CHECK:STDOUT:   %.loc17_23.2.vptr = getelementptr inbounds nuw { ptr }, ptr %t2.var, i32 0, i32 0, !dbg !10
-// CHECK:STDOUT:   call void @llvm.memcpy.p0.p0.i64(ptr align 8 %t2.var, ptr align 8 @Base.val.5bf.loc17_3, i64 8, i1 false), !dbg !8
+// CHECK:STDOUT:   %_.var.loc16 = alloca { ptr }, align 8, !dbg !7
+// CHECK:STDOUT:   %_.var.loc17 = alloca { ptr }, align 8, !dbg !8
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var.loc16), !dbg !7
+// CHECK:STDOUT:   %.loc16_22.2.vptr = getelementptr inbounds nuw { ptr }, ptr %_.var.loc16, i32 0, i32 0, !dbg !9
+// CHECK:STDOUT:   call void @llvm.memcpy.p0.p0.i64(ptr align 8 %_.var.loc16, ptr align 8 @Base.val.439.loc16_3, i64 8, i1 false), !dbg !7
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var.loc17), !dbg !8
+// CHECK:STDOUT:   %.loc17_22.2.vptr = getelementptr inbounds nuw { ptr }, ptr %_.var.loc17, i32 0, i32 0, !dbg !10
+// CHECK:STDOUT:   call void @llvm.memcpy.p0.p0.i64(ptr align 8 %_.var.loc17, ptr align 8 @Base.val.5bf.loc17_3, i64 8, i1 false), !dbg !8
 // CHECK:STDOUT:   ret void, !dbg !11
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
 // CHECK:STDOUT: define linkonce_odr void @_CF.Base.Main.4ff89889d3f52e25(ptr %self) #0 !dbg !12 {
 // CHECK:STDOUT: entry:
-// CHECK:STDOUT:   %v.var = alloca {}, align 8, !dbg !18
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %v.var), !dbg !18
+// CHECK:STDOUT:   %_.var = alloca {}, align 8, !dbg !18
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var), !dbg !18
 // CHECK:STDOUT:   ret void, !dbg !19
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
 // CHECK:STDOUT: define linkonce_odr void @_CF.Base.Main.af40b72a3cc0ef58(ptr %self) #0 !dbg !20 {
 // CHECK:STDOUT: entry:
-// CHECK:STDOUT:   %v.var = alloca { {} }, align 8, !dbg !23
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %v.var), !dbg !23
+// CHECK:STDOUT:   %_.var = alloca { {} }, align 8, !dbg !23
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var), !dbg !23
 // CHECK:STDOUT:   ret void, !dbg !24
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
@@ -562,8 +562,8 @@ fn Make() {
 // CHECK:STDOUT: !6 = !{null}
 // CHECK:STDOUT: !7 = !DILocation(line: 16, column: 3, scope: !4)
 // CHECK:STDOUT: !8 = !DILocation(line: 17, column: 3, scope: !4)
-// CHECK:STDOUT: !9 = !DILocation(line: 16, column: 22, scope: !4)
-// CHECK:STDOUT: !10 = !DILocation(line: 17, column: 22, scope: !4)
+// CHECK:STDOUT: !9 = !DILocation(line: 16, column: 21, scope: !4)
+// CHECK:STDOUT: !10 = !DILocation(line: 17, column: 21, scope: !4)
 // CHECK:STDOUT: !11 = !DILocation(line: 15, column: 1, scope: !4)
 // CHECK:STDOUT: !12 = distinct !DISubprogram(name: "F", linkageName: "_CF.Base.Main.4ff89889d3f52e25", scope: null, file: !3, line: 5, type: !13, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !16)
 // CHECK:STDOUT: !13 = !DISubroutineType(types: !14)
@@ -586,8 +586,8 @@ fn Make() {
 // CHECK:STDOUT: ; Function Attrs: nounwind
 // CHECK:STDOUT: define void @_CMake.Main() #0 !dbg !4 {
 // CHECK:STDOUT: entry:
-// CHECK:STDOUT:   %v.var = alloca { { ptr } }, align 8, !dbg !7
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %v.var), !dbg !7
+// CHECK:STDOUT:   %_.var = alloca { { ptr } }, align 8, !dbg !7
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var), !dbg !7
 // CHECK:STDOUT:   ret void, !dbg !8
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
diff --git a/toolchain/lower/testdata/for/bindings.carbon b/toolchain/lower/testdata/for/bindings.carbon
index d8a7b55d967d..b508b061f2a7 100644
--- a/toolchain/lower/testdata/for/bindings.carbon
+++ b/toolchain/lower/testdata/for/bindings.carbon
@@ -15,7 +15,7 @@ class EmptyRange(T:! Core.Copy) {
     fn NewCursor[self: Self]() -> {} {
       return {};
     }
-    fn Next[self: Self](cursor: {}*) -> Core.Optional(T) {
+    fn Next[self: Self](_: {}*) -> Core.Optional(T) {
       return Core.Optional(T).None();
     }
   }
@@ -87,7 +87,7 @@ fn For() {
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
-// CHECK:STDOUT: define linkonce_odr void @"_CNext.EmptyRange.Main:Iterate.Core.f3fd01d4dee2d7f7"(ptr sret({ { i32, i32 }, i1 }) %return, ptr %self, ptr %cursor) #0 !dbg !20 {
+// CHECK:STDOUT: define linkonce_odr void @"_CNext.EmptyRange.Main:Iterate.Core.f3fd01d4dee2d7f7"(ptr sret({ { i32, i32 }, i1 }) %return, ptr %self, ptr %_) #0 !dbg !20 {
 // CHECK:STDOUT: entry:
 // CHECK:STDOUT:   call void @_CNone.Optional.Core.9925d053027dadb9(ptr %return), !dbg !26
 // CHECK:STDOUT:   ret void, !dbg !27
diff --git a/toolchain/lower/testdata/for/break_continue.carbon b/toolchain/lower/testdata/for/break_continue.carbon
index cca04a183d7b..7efd18f6cd17 100644
--- a/toolchain/lower/testdata/for/break_continue.carbon
+++ b/toolchain/lower/testdata/for/break_continue.carbon
@@ -17,7 +17,7 @@ fn G() -> bool;
 fn H();
 
 fn For() {
-  for (n: i32 in Core.Range(100)) {
+  for (_: i32 in Core.Range(100)) {
     if (F()) { break; }
     if (G()) { continue; }
     H();
diff --git a/toolchain/lower/testdata/for/for.carbon b/toolchain/lower/testdata/for/for.carbon
index 40dd6eb0112c..6502cb857c01 100644
--- a/toolchain/lower/testdata/for/for.carbon
+++ b/toolchain/lower/testdata/for/for.carbon
@@ -18,7 +18,7 @@ fn H();
 
 fn For() {
   F();
-  for (n: i32 in Core.Range(100)) {
+  for (_: i32 in Core.Range(100)) {
     G();
   }
   H();
diff --git a/toolchain/lower/testdata/function/call/empty_struct.carbon b/toolchain/lower/testdata/function/call/empty_struct.carbon
index 36acf8e19ca2..de8d013c796e 100644
--- a/toolchain/lower/testdata/function/call/empty_struct.carbon
+++ b/toolchain/lower/testdata/function/call/empty_struct.carbon
@@ -10,12 +10,12 @@
 // TIP: To dump output, run:
 // TIP:   bazel run //toolchain/testing:file_test -- --dump_output --file_tests=toolchain/lower/testdata/function/call/empty_struct.carbon
 
-fn Echo(a: {}) -> {} {
+fn Echo(_: {}) -> {} {
   return {};
 }
 
 fn Main() {
-  var b: {} = Echo({});
+  var _: {} = Echo({});
 }
 
 // CHECK:STDOUT: ; ModuleID = 'empty_struct.carbon'
@@ -30,8 +30,8 @@ fn Main() {
 // CHECK:STDOUT: ; Function Attrs: nounwind
 // CHECK:STDOUT: define void @_CMain.Main() #0 !dbg !9 {
 // CHECK:STDOUT: entry:
-// CHECK:STDOUT:   %b.var = alloca {}, align 8, !dbg !12
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %b.var), !dbg !12
+// CHECK:STDOUT:   %_.var = alloca {}, align 8, !dbg !12
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var), !dbg !12
 // CHECK:STDOUT:   call void @_CEcho.Main(), !dbg !13
 // CHECK:STDOUT:   ret void, !dbg !14
 // CHECK:STDOUT: }
diff --git a/toolchain/lower/testdata/function/call/empty_tuple.carbon b/toolchain/lower/testdata/function/call/empty_tuple.carbon
index 29652a8bffb9..7977539275be 100644
--- a/toolchain/lower/testdata/function/call/empty_tuple.carbon
+++ b/toolchain/lower/testdata/function/call/empty_tuple.carbon
@@ -15,7 +15,7 @@ fn Echo(a: ()) -> () {
 }
 
 fn Main() {
-  var b: () = Echo(());
+  var _: () = Echo(());
 }
 
 // CHECK:STDOUT: ; ModuleID = 'empty_tuple.carbon'
@@ -30,8 +30,8 @@ fn Main() {
 // CHECK:STDOUT: ; Function Attrs: nounwind
 // CHECK:STDOUT: define void @_CMain.Main() #0 !dbg !9 {
 // CHECK:STDOUT: entry:
-// CHECK:STDOUT:   %b.var = alloca {}, align 8, !dbg !12
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %b.var), !dbg !12
+// CHECK:STDOUT:   %_.var = alloca {}, align 8, !dbg !12
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var), !dbg !12
 // CHECK:STDOUT:   call void @_CEcho.Main(), !dbg !13
 // CHECK:STDOUT:   ret void, !dbg !14
 // CHECK:STDOUT: }
diff --git a/toolchain/lower/testdata/function/call/i32.carbon b/toolchain/lower/testdata/function/call/i32.carbon
index 996f59ab5bdc..25092bd50eee 100644
--- a/toolchain/lower/testdata/function/call/i32.carbon
+++ b/toolchain/lower/testdata/function/call/i32.carbon
@@ -15,7 +15,7 @@ fn Echo(a: i32) -> i32 {
 }
 
 fn Main() {
-  var b: i32 = Echo(1);
+  var _: i32 = Echo(1);
 }
 
 // CHECK:STDOUT: ; ModuleID = 'i32.carbon'
@@ -30,10 +30,10 @@ fn Main() {
 // CHECK:STDOUT: ; Function Attrs: nounwind
 // CHECK:STDOUT: define void @_CMain.Main() #0 !dbg !11 {
 // CHECK:STDOUT: entry:
-// CHECK:STDOUT:   %b.var = alloca i32, align 4, !dbg !14
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %b.var), !dbg !14
+// CHECK:STDOUT:   %_.var = alloca i32, align 4, !dbg !14
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var), !dbg !14
 // CHECK:STDOUT:   %Echo.call = call i32 @_CEcho.Main(i32 1), !dbg !15
-// CHECK:STDOUT:   store i32 %Echo.call, ptr %b.var, align 4, !dbg !14
+// CHECK:STDOUT:   store i32 %Echo.call, ptr %_.var, align 4, !dbg !14
 // CHECK:STDOUT:   ret void, !dbg !16
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
diff --git a/toolchain/lower/testdata/function/call/implicit_empty_tuple_as_arg.carbon b/toolchain/lower/testdata/function/call/implicit_empty_tuple_as_arg.carbon
index 7d80e3bbe830..a3d9364af59e 100644
--- a/toolchain/lower/testdata/function/call/implicit_empty_tuple_as_arg.carbon
+++ b/toolchain/lower/testdata/function/call/implicit_empty_tuple_as_arg.carbon
@@ -16,7 +16,7 @@ fn Foo() {}
 fn Bar(a: ()) -> () { return a; }
 
 fn Main() {
-  var x: () = Bar(Foo());
+  var _: () = Bar(Foo());
 }
 
 // CHECK:STDOUT: ; ModuleID = 'implicit_empty_tuple_as_arg.carbon'
@@ -37,9 +37,9 @@ fn Main() {
 // CHECK:STDOUT: ; Function Attrs: nounwind
 // CHECK:STDOUT: define void @_CMain.Main() #0 !dbg !13 {
 // CHECK:STDOUT: entry:
-// CHECK:STDOUT:   %x.var = alloca {}, align 8, !dbg !14
+// CHECK:STDOUT:   %_.var = alloca {}, align 8, !dbg !14
 // CHECK:STDOUT:   %.loc19_23.1.temp = alloca {}, align 8, !dbg !15
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %x.var), !dbg !14
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var), !dbg !14
 // CHECK:STDOUT:   call void @_CFoo.Main(), !dbg !15
 // CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %.loc19_23.1.temp), !dbg !15
 // CHECK:STDOUT:   call void @_CBar.Main(), !dbg !16
diff --git a/toolchain/lower/testdata/function/call/params_one.carbon b/toolchain/lower/testdata/function/call/params_one.carbon
index b6c4f681fbf9..07cf04587043 100644
--- a/toolchain/lower/testdata/function/call/params_one.carbon
+++ b/toolchain/lower/testdata/function/call/params_one.carbon
@@ -10,7 +10,7 @@
 // TIP: To dump output, run:
 // TIP:   bazel run //toolchain/testing:file_test -- --dump_output --file_tests=toolchain/lower/testdata/function/call/params_one.carbon
 
-fn Foo(a: i32) {}
+fn Foo(_: i32) {}
 
 fn Main() {
   Foo(1);
@@ -20,7 +20,7 @@ fn Main() {
 // CHECK:STDOUT: source_filename = "params_one.carbon"
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
-// CHECK:STDOUT: define void @_CFoo.Main(i32 %a) #0 !dbg !4 {
+// CHECK:STDOUT: define void @_CFoo.Main(i32 %_) #0 !dbg !4 {
 // CHECK:STDOUT: entry:
 // CHECK:STDOUT:   ret void, !dbg !10
 // CHECK:STDOUT: }
diff --git a/toolchain/lower/testdata/function/call/params_one_comma.carbon b/toolchain/lower/testdata/function/call/params_one_comma.carbon
index 5e45163ac150..2af913aaad9e 100644
--- a/toolchain/lower/testdata/function/call/params_one_comma.carbon
+++ b/toolchain/lower/testdata/function/call/params_one_comma.carbon
@@ -10,7 +10,7 @@
 // TIP: To dump output, run:
 // TIP:   bazel run //toolchain/testing:file_test -- --dump_output --file_tests=toolchain/lower/testdata/function/call/params_one_comma.carbon
 
-fn Foo(a: i32,) {}
+fn Foo(_: i32,) {}
 
 fn Main() {
   Foo(1);
@@ -21,7 +21,7 @@ fn Main() {
 // CHECK:STDOUT: source_filename = "params_one_comma.carbon"
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
-// CHECK:STDOUT: define void @_CFoo.Main(i32 %a) #0 !dbg !4 {
+// CHECK:STDOUT: define void @_CFoo.Main(i32 %_) #0 !dbg !4 {
 // CHECK:STDOUT: entry:
 // CHECK:STDOUT:   ret void, !dbg !10
 // CHECK:STDOUT: }
diff --git a/toolchain/lower/testdata/function/call/params_two.carbon b/toolchain/lower/testdata/function/call/params_two.carbon
index cd158dc4ac71..79ddb9055c70 100644
--- a/toolchain/lower/testdata/function/call/params_two.carbon
+++ b/toolchain/lower/testdata/function/call/params_two.carbon
@@ -10,7 +10,7 @@
 // TIP: To dump output, run:
 // TIP:   bazel run //toolchain/testing:file_test -- --dump_output --file_tests=toolchain/lower/testdata/function/call/params_two.carbon
 
-fn Foo(a: i32, b: i32) {}
+fn Foo(_: i32, _: i32) {}
 
 fn Main() {
   Foo(1, 2);
@@ -20,7 +20,7 @@ fn Main() {
 // CHECK:STDOUT: source_filename = "params_two.carbon"
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
-// CHECK:STDOUT: define void @_CFoo.Main(i32 %a, i32 %b) #0 !dbg !4 {
+// CHECK:STDOUT: define void @_CFoo.Main(i32 %_, i32 %_1) #0 !dbg !4 {
 // CHECK:STDOUT: entry:
 // CHECK:STDOUT:   ret void, !dbg !11
 // CHECK:STDOUT: }
diff --git a/toolchain/lower/testdata/function/call/params_two_comma.carbon b/toolchain/lower/testdata/function/call/params_two_comma.carbon
index 0abe12f74640..2fe1b431dc12 100644
--- a/toolchain/lower/testdata/function/call/params_two_comma.carbon
+++ b/toolchain/lower/testdata/function/call/params_two_comma.carbon
@@ -10,7 +10,7 @@
 // TIP: To dump output, run:
 // TIP:   bazel run //toolchain/testing:file_test -- --dump_output --file_tests=toolchain/lower/testdata/function/call/params_two_comma.carbon
 
-fn Foo(a: i32, b: i32,) {}
+fn Foo(_: i32, _: i32,) {}
 
 fn Main() {
   Foo(1, 2);
@@ -21,7 +21,7 @@ fn Main() {
 // CHECK:STDOUT: source_filename = "params_two_comma.carbon"
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
-// CHECK:STDOUT: define void @_CFoo.Main(i32 %a, i32 %b) #0 !dbg !4 {
+// CHECK:STDOUT: define void @_CFoo.Main(i32 %_, i32 %_1) #0 !dbg !4 {
 // CHECK:STDOUT: entry:
 // CHECK:STDOUT:   ret void, !dbg !11
 // CHECK:STDOUT: }
diff --git a/toolchain/lower/testdata/function/call/ref_param.carbon b/toolchain/lower/testdata/function/call/ref_param.carbon
index 5c45d7bb6d52..b5554b8fcfd8 100644
--- a/toolchain/lower/testdata/function/call/ref_param.carbon
+++ b/toolchain/lower/testdata/function/call/ref_param.carbon
@@ -10,7 +10,7 @@
 // TIP: To dump output, run:
 // TIP:   bazel run //toolchain/testing:file_test -- --dump_output --file_tests=toolchain/lower/testdata/function/call/ref_param.carbon
 
-fn DoNothing(ref a: i32) {}
+fn DoNothing(ref _: i32) {}
 
 fn Main() {
   var a: i32 = 0;
@@ -21,7 +21,7 @@ fn Main() {
 // CHECK:STDOUT: source_filename = "ref_param.carbon"
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
-// CHECK:STDOUT: define void @_CDoNothing.Main(ptr %a) #0 !dbg !4 {
+// CHECK:STDOUT: define void @_CDoNothing.Main(ptr %_) #0 !dbg !4 {
 // CHECK:STDOUT: entry:
 // CHECK:STDOUT:   ret void, !dbg !10
 // CHECK:STDOUT: }
diff --git a/toolchain/lower/testdata/function/call/return_implicit.carbon b/toolchain/lower/testdata/function/call/return_implicit.carbon
index 3142bda1d23c..aa182b06c2d0 100644
--- a/toolchain/lower/testdata/function/call/return_implicit.carbon
+++ b/toolchain/lower/testdata/function/call/return_implicit.carbon
@@ -15,7 +15,7 @@ fn MakeImplicitEmptyTuple() {
 }
 
 fn Main() {
-  var b: () = MakeImplicitEmptyTuple();
+  var _: () = MakeImplicitEmptyTuple();
 }
 
 // CHECK:STDOUT: ; ModuleID = 'return_implicit.carbon'
@@ -30,8 +30,8 @@ fn Main() {
 // CHECK:STDOUT: ; Function Attrs: nounwind
 // CHECK:STDOUT: define void @_CMain.Main() #0 !dbg !8 {
 // CHECK:STDOUT: entry:
-// CHECK:STDOUT:   %b.var = alloca {}, align 8, !dbg !9
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %b.var), !dbg !9
+// CHECK:STDOUT:   %_.var = alloca {}, align 8, !dbg !9
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var), !dbg !9
 // CHECK:STDOUT:   call void @_CMakeImplicitEmptyTuple.Main(), !dbg !10
 // CHECK:STDOUT:   ret void, !dbg !11
 // CHECK:STDOUT: }
diff --git a/toolchain/lower/testdata/function/call/struct_param.carbon b/toolchain/lower/testdata/function/call/struct_param.carbon
index 3ca2958e06a3..cec6a1080f29 100644
--- a/toolchain/lower/testdata/function/call/struct_param.carbon
+++ b/toolchain/lower/testdata/function/call/struct_param.carbon
@@ -10,7 +10,7 @@
 // TIP: To dump output, run:
 // TIP:   bazel run //toolchain/testing:file_test -- --dump_output --file_tests=toolchain/lower/testdata/function/call/struct_param.carbon
 
-fn F(a: {}, b: {.a: i32}, c: {.a: i32, .b: i32}) {}
+fn F(_: {}, _: {.a: i32}, _: {.a: i32, .b: i32}) {}
 
 fn Main() {
   F({}, {.a = 1}, {.a = 2, .b = 3});
@@ -22,7 +22,7 @@ fn Main() {
 // CHECK:STDOUT: @struct.9ae.loc16_34.6 = internal constant { i32, i32 } { i32 2, i32 3 }
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
-// CHECK:STDOUT: define void @_CF.Main({ i32 } %b, ptr %c) #0 !dbg !4 {
+// CHECK:STDOUT: define void @_CF.Main({ i32 } %_, ptr %_1) #0 !dbg !4 {
 // CHECK:STDOUT: entry:
 // CHECK:STDOUT:   ret void, !dbg !11
 // CHECK:STDOUT: }
diff --git a/toolchain/lower/testdata/function/call/tuple_param.carbon b/toolchain/lower/testdata/function/call/tuple_param.carbon
index 4afd57be1400..2cc800215b6c 100644
--- a/toolchain/lower/testdata/function/call/tuple_param.carbon
+++ b/toolchain/lower/testdata/function/call/tuple_param.carbon
@@ -10,7 +10,7 @@
 // TIP: To dump output, run:
 // TIP:   bazel run //toolchain/testing:file_test -- --dump_output --file_tests=toolchain/lower/testdata/function/call/tuple_param.carbon
 
-fn F(a: (), b: (i32,), c: (i32, i32)) {}
+fn F(_: (), _: (i32,), _: (i32, i32)) {}
 
 fn Main() {
   F((), (1,), (2, 3));
@@ -22,7 +22,7 @@ fn Main() {
 // CHECK:STDOUT: @tuple.11a.loc16_20.6 = internal constant { i32, i32 } { i32 2, i32 3 }
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
-// CHECK:STDOUT: define void @_CF.Main({ i32 } %b, ptr %c) #0 !dbg !4 {
+// CHECK:STDOUT: define void @_CF.Main({ i32 } %_, ptr %_1) #0 !dbg !4 {
 // CHECK:STDOUT: entry:
 // CHECK:STDOUT:   ret void, !dbg !11
 // CHECK:STDOUT: }
diff --git a/toolchain/lower/testdata/function/call/tuple_param_with_return_slot.carbon b/toolchain/lower/testdata/function/call/tuple_param_with_return_slot.carbon
index 858f254bbf48..7bf8e07beb84 100644
--- a/toolchain/lower/testdata/function/call/tuple_param_with_return_slot.carbon
+++ b/toolchain/lower/testdata/function/call/tuple_param_with_return_slot.carbon
@@ -10,7 +10,7 @@
 // TIP: To dump output, run:
 // TIP:   bazel run //toolchain/testing:file_test -- --dump_output --file_tests=toolchain/lower/testdata/function/call/tuple_param_with_return_slot.carbon
 
-fn F(a: (), b: (i32,), c: (i32, i32)) -> (i32, i32, i32) {
+fn F(_: (), b: (i32,), c: (i32, i32)) -> (i32, i32, i32) {
   return (b.0, c.0, c.1);
 }
 
diff --git a/toolchain/lower/testdata/function/call/var_param.carbon b/toolchain/lower/testdata/function/call/var_param.carbon
index ac1fc1d1bb0c..a38cda3f185b 100644
--- a/toolchain/lower/testdata/function/call/var_param.carbon
+++ b/toolchain/lower/testdata/function/call/var_param.carbon
@@ -10,7 +10,7 @@
 // TIP: To dump output, run:
 // TIP:   bazel run //toolchain/testing:file_test -- --dump_output --file_tests=toolchain/lower/testdata/function/call/var_param.carbon
 
-fn DoNothing(a: i32) {}
+fn DoNothing(_: i32) {}
 
 fn Main() {
   var a: i32 = 0;
@@ -21,7 +21,7 @@ fn Main() {
 // CHECK:STDOUT: source_filename = "var_param.carbon"
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
-// CHECK:STDOUT: define void @_CDoNothing.Main(i32 %a) #0 !dbg !4 {
+// CHECK:STDOUT: define void @_CDoNothing.Main(i32 %_) #0 !dbg !4 {
 // CHECK:STDOUT: entry:
 // CHECK:STDOUT:   ret void, !dbg !10
 // CHECK:STDOUT: }
diff --git a/toolchain/lower/testdata/function/definition/destroy.carbon b/toolchain/lower/testdata/function/definition/destroy.carbon
index 389c61e50bd5..e7bd4aeffecd 100644
--- a/toolchain/lower/testdata/function/definition/destroy.carbon
+++ b/toolchain/lower/testdata/function/definition/destroy.carbon
@@ -16,7 +16,7 @@ library "[[@TEST_NAME]]";
 
 class C {}
 
-fn F(x: C) {
+fn F(_: C) {
 }
 
 fn G();
@@ -34,7 +34,7 @@ library "[[@TEST_NAME]]";
 
 class C {}
 
-fn F(var x: C) {
+fn F(var _: C) {
 }
 
 fn G();
@@ -63,12 +63,12 @@ fn Forward() -> C {
 }
 
 fn InitVar() {
-  var local: C = F();
+  var _: C = F();
   G();
 }
 
 fn InitLet() {
-  let local: C = F();
+  let _: C = F();
   G();
 }
 
@@ -78,7 +78,7 @@ fn InitLet() {
 // CHECK:STDOUT: @C.val.loc12_6.3 = internal constant {} zeroinitializer
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
-// CHECK:STDOUT: define void @_CF.Main(ptr %x) #0 !dbg !4 {
+// CHECK:STDOUT: define void @_CF.Main(ptr %_) #0 !dbg !4 {
 // CHECK:STDOUT: entry:
 // CHECK:STDOUT:   ret void, !dbg !10
 // CHECK:STDOUT: }
@@ -133,7 +133,7 @@ fn InitLet() {
 // CHECK:STDOUT: @C.val.loc6_6.2 = internal constant {} zeroinitializer
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
-// CHECK:STDOUT: define void @_CF.Main(ptr %x) #0 !dbg !4 {
+// CHECK:STDOUT: define void @_CF.Main(ptr %_) #0 !dbg !4 {
 // CHECK:STDOUT: entry:
 // CHECK:STDOUT:   ret void, !dbg !10
 // CHECK:STDOUT: }
@@ -206,9 +206,9 @@ fn InitLet() {
 // CHECK:STDOUT: ; Function Attrs: nounwind
 // CHECK:STDOUT: define void @_CInitVar.Main() #0 !dbg !12 {
 // CHECK:STDOUT: entry:
-// CHECK:STDOUT:   %local.var = alloca {}, align 8, !dbg !15
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %local.var), !dbg !15
-// CHECK:STDOUT:   call void @_CF.Main(ptr %local.var), !dbg !16
+// CHECK:STDOUT:   %_.var = alloca {}, align 8, !dbg !15
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var), !dbg !15
+// CHECK:STDOUT:   call void @_CF.Main(ptr %_.var), !dbg !16
 // CHECK:STDOUT:   call void @_CG.Main(), !dbg !17
 // CHECK:STDOUT:   ret void, !dbg !18
 // CHECK:STDOUT: }
@@ -216,9 +216,9 @@ fn InitLet() {
 // CHECK:STDOUT: ; Function Attrs: nounwind
 // CHECK:STDOUT: define void @_CInitLet.Main() #0 !dbg !19 {
 // CHECK:STDOUT: entry:
-// CHECK:STDOUT:   %.loc22_20.1.temp = alloca {}, align 8, !dbg !20
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %.loc22_20.1.temp), !dbg !20
-// CHECK:STDOUT:   call void @_CF.Main(ptr %.loc22_20.1.temp), !dbg !20
+// CHECK:STDOUT:   %.loc22_16.1.temp = alloca {}, align 8, !dbg !20
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %.loc22_16.1.temp), !dbg !20
+// CHECK:STDOUT:   call void @_CF.Main(ptr %.loc22_16.1.temp), !dbg !20
 // CHECK:STDOUT:   call void @_CG.Main(), !dbg !21
 // CHECK:STDOUT:   ret void, !dbg !22
 // CHECK:STDOUT: }
@@ -255,10 +255,10 @@ fn InitLet() {
 // CHECK:STDOUT: !13 = !DISubroutineType(types: !14)
 // CHECK:STDOUT: !14 = !{null}
 // CHECK:STDOUT: !15 = !DILocation(line: 17, column: 3, scope: !12)
-// CHECK:STDOUT: !16 = !DILocation(line: 17, column: 18, scope: !12)
+// CHECK:STDOUT: !16 = !DILocation(line: 17, column: 14, scope: !12)
 // CHECK:STDOUT: !17 = !DILocation(line: 18, column: 3, scope: !12)
 // CHECK:STDOUT: !18 = !DILocation(line: 16, column: 1, scope: !12)
 // CHECK:STDOUT: !19 = distinct !DISubprogram(name: "InitLet", linkageName: "_CInitLet.Main", scope: null, file: !3, line: 21, type: !13, spFlags: DISPFlagDefinition, unit: !2)
-// CHECK:STDOUT: !20 = !DILocation(line: 22, column: 18, scope: !19)
+// CHECK:STDOUT: !20 = !DILocation(line: 22, column: 14, scope: !19)
 // CHECK:STDOUT: !21 = !DILocation(line: 23, column: 3, scope: !19)
 // CHECK:STDOUT: !22 = !DILocation(line: 21, column: 1, scope: !19)
diff --git a/toolchain/lower/testdata/function/definition/empty_struct.carbon b/toolchain/lower/testdata/function/definition/empty_struct.carbon
index 13d8ad92e0fd..93e735d15bfb 100644
--- a/toolchain/lower/testdata/function/definition/empty_struct.carbon
+++ b/toolchain/lower/testdata/function/definition/empty_struct.carbon
@@ -10,7 +10,7 @@
 // TIP: To dump output, run:
 // TIP:   bazel run //toolchain/testing:file_test -- --dump_output --file_tests=toolchain/lower/testdata/function/definition/empty_struct.carbon
 
-fn Echo(a: {}) {
+fn Echo(_: {}) {
 }
 
 // CHECK:STDOUT: ; ModuleID = 'empty_struct.carbon'
diff --git a/toolchain/lower/testdata/function/definition/params_one.carbon b/toolchain/lower/testdata/function/definition/params_one.carbon
index 132828240f86..c85fdb79955e 100644
--- a/toolchain/lower/testdata/function/definition/params_one.carbon
+++ b/toolchain/lower/testdata/function/definition/params_one.carbon
@@ -10,13 +10,13 @@
 // TIP: To dump output, run:
 // TIP:   bazel run //toolchain/testing:file_test -- --dump_output --file_tests=toolchain/lower/testdata/function/definition/params_one.carbon
 
-fn Foo(a: i32) {}
+fn Foo(_: i32) {}
 
 // CHECK:STDOUT: ; ModuleID = 'params_one.carbon'
 // CHECK:STDOUT: source_filename = "params_one.carbon"
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
-// CHECK:STDOUT: define void @_CFoo.Main(i32 %a) #0 !dbg !4 {
+// CHECK:STDOUT: define void @_CFoo.Main(i32 %_) #0 !dbg !4 {
 // CHECK:STDOUT: entry:
 // CHECK:STDOUT:   ret void, !dbg !10
 // CHECK:STDOUT: }
diff --git a/toolchain/lower/testdata/function/definition/params_two.carbon b/toolchain/lower/testdata/function/definition/params_two.carbon
index cf899fadac7f..ce2c6123a95d 100644
--- a/toolchain/lower/testdata/function/definition/params_two.carbon
+++ b/toolchain/lower/testdata/function/definition/params_two.carbon
@@ -10,13 +10,13 @@
 // TIP: To dump output, run:
 // TIP:   bazel run //toolchain/testing:file_test -- --dump_output --file_tests=toolchain/lower/testdata/function/definition/params_two.carbon
 
-fn Foo(a: i32, b: i32) {}
+fn Foo(_: i32, _: i32) {}
 
 // CHECK:STDOUT: ; ModuleID = 'params_two.carbon'
 // CHECK:STDOUT: source_filename = "params_two.carbon"
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
-// CHECK:STDOUT: define void @_CFoo.Main(i32 %a, i32 %b) #0 !dbg !4 {
+// CHECK:STDOUT: define void @_CFoo.Main(i32 %_, i32 %_1) #0 !dbg !4 {
 // CHECK:STDOUT: entry:
 // CHECK:STDOUT:   ret void, !dbg !11
 // CHECK:STDOUT: }
diff --git a/toolchain/lower/testdata/function/definition/var_param.carbon b/toolchain/lower/testdata/function/definition/var_param.carbon
index 5b8ab633abcf..9346644c4b09 100644
--- a/toolchain/lower/testdata/function/definition/var_param.carbon
+++ b/toolchain/lower/testdata/function/definition/var_param.carbon
@@ -12,13 +12,13 @@
 
 class X {}
 
-fn OneVar_i32(var n: i32) {}
-fn OneVar_X(var x: X) {}
+fn OneVar_i32(var _: i32) {}
+fn OneVar_X(var _: X) {}
 
-fn TwoVars(var a: i32, var b: X) {}
+fn TwoVars(var _: i32, var _: X) {}
 
-fn VarThenLet(var a: i32, b: X) {}
-fn LetThenVar(a: i32, var b: X) {}
+fn VarThenLet(var _: i32, _: X) {}
+fn LetThenVar(_: i32, var _: X) {}
 
 fn Call() {
   OneVar_i32(1);
@@ -34,31 +34,31 @@ fn Call() {
 // CHECK:STDOUT: @X.val.loc16_13.2 = internal constant {} zeroinitializer
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
-// CHECK:STDOUT: define void @_COneVar_i32.Main(ptr %n) #0 !dbg !4 {
+// CHECK:STDOUT: define void @_COneVar_i32.Main(ptr %_) #0 !dbg !4 {
 // CHECK:STDOUT: entry:
 // CHECK:STDOUT:   ret void, !dbg !10
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
-// CHECK:STDOUT: define void @_COneVar_X.Main(ptr %x) #0 !dbg !11 {
+// CHECK:STDOUT: define void @_COneVar_X.Main(ptr %_) #0 !dbg !11 {
 // CHECK:STDOUT: entry:
 // CHECK:STDOUT:   ret void, !dbg !17
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
-// CHECK:STDOUT: define void @_CTwoVars.Main(ptr %a, ptr %b) #0 !dbg !18 {
+// CHECK:STDOUT: define void @_CTwoVars.Main(ptr %_, ptr %_1) #0 !dbg !18 {
 // CHECK:STDOUT: entry:
 // CHECK:STDOUT:   ret void, !dbg !24
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
-// CHECK:STDOUT: define void @_CVarThenLet.Main(ptr %a, ptr %b) #0 !dbg !25 {
+// CHECK:STDOUT: define void @_CVarThenLet.Main(ptr %_, ptr %_1) #0 !dbg !25 {
 // CHECK:STDOUT: entry:
 // CHECK:STDOUT:   ret void, !dbg !29
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
-// CHECK:STDOUT: define void @_CLetThenVar.Main(i32 %a, ptr %b) #0 !dbg !30 {
+// CHECK:STDOUT: define void @_CLetThenVar.Main(i32 %_, ptr %_1) #0 !dbg !30 {
 // CHECK:STDOUT: entry:
 // CHECK:STDOUT:   ret void, !dbg !34
 // CHECK:STDOUT: }
diff --git a/toolchain/lower/testdata/function/generic/call.carbon b/toolchain/lower/testdata/function/generic/call.carbon
index 56223cc08c67..e52f72973817 100644
--- a/toolchain/lower/testdata/function/generic/call.carbon
+++ b/toolchain/lower/testdata/function/generic/call.carbon
@@ -10,7 +10,7 @@
 // TIP: To dump output, run:
 // TIP:   bazel run //toolchain/testing:file_test -- --dump_output --file_tests=toolchain/lower/testdata/function/generic/call.carbon
 
-fn F[T:! type](x: T) {
+fn F[T:! type](_: T) {
 }
 
 class C {}
@@ -69,25 +69,25 @@ fn G() {
 // CHECK:STDOUT: declare void @llvm.memcpy.p0.p0.i64(ptr noalias writeonly captures(none), ptr noalias readonly captures(none), i64, i1 immarg) #2
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
-// CHECK:STDOUT: define linkonce_odr void @_CF.Main.0c4ab795cec6cb27(ptr %x) #0 !dbg !19 {
+// CHECK:STDOUT: define linkonce_odr void @_CF.Main.0c4ab795cec6cb27(ptr %_) #0 !dbg !19 {
 // CHECK:STDOUT: entry:
 // CHECK:STDOUT:   ret void, !dbg !25
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
-// CHECK:STDOUT: define linkonce_odr void @_CF.Main.b88d1103f417c6d4(i32 %x) #0 !dbg !26 {
+// CHECK:STDOUT: define linkonce_odr void @_CF.Main.b88d1103f417c6d4(i32 %_) #0 !dbg !26 {
 // CHECK:STDOUT: entry:
 // CHECK:STDOUT:   ret void, !dbg !32
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
-// CHECK:STDOUT: define linkonce_odr void @_CF.Main.d4b5665541d5d7a8(double %x) #0 !dbg !33 {
+// CHECK:STDOUT: define linkonce_odr void @_CF.Main.d4b5665541d5d7a8(double %_) #0 !dbg !33 {
 // CHECK:STDOUT: entry:
 // CHECK:STDOUT:   ret void, !dbg !36
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
-// CHECK:STDOUT: define linkonce_odr void @_CF.Main.5754c7a55c7cbe4a(%type %x) #0 !dbg !37 {
+// CHECK:STDOUT: define linkonce_odr void @_CF.Main.5754c7a55c7cbe4a(%type %_) #0 !dbg !37 {
 // CHECK:STDOUT: entry:
 // CHECK:STDOUT:   ret void, !dbg !40
 // CHECK:STDOUT: }
diff --git a/toolchain/lower/testdata/function/generic/call_basic.carbon b/toolchain/lower/testdata/function/generic/call_basic.carbon
index 70be80269e82..20918b4a8070 100644
--- a/toolchain/lower/testdata/function/generic/call_basic.carbon
+++ b/toolchain/lower/testdata/function/generic/call_basic.carbon
@@ -16,7 +16,7 @@ class C {
   }
 }
 
-fn F[T:! type](x: T) {
+fn F[T:! type](_: T) {
 }
 
 fn H[T:! Core.Copy](x: T) -> T {
@@ -47,14 +47,12 @@ fn G[T:! Core.Copy & Core.Destroy](x: T) -> T {
 
 fn M() {
   var n: i32 = 0;
-  var m: i32;
   var p: f64 = 1.0;
-  var q: f64;
 
   F(n);
-  m = G(n);
+  let _: i32 = G(n);
   F(p);
-  q = G(p);
+  let _: f64 = G(p);
 }
 
 // CHECK:STDOUT: ; ModuleID = 'call_basic.carbon'
@@ -75,26 +73,20 @@ fn M() {
 // CHECK:STDOUT: define void @_CM.Main() #0 !dbg !11 {
 // CHECK:STDOUT: entry:
 // CHECK:STDOUT:   %n.var = alloca i32, align 4, !dbg !14
-// CHECK:STDOUT:   %m.var = alloca i32, align 4, !dbg !15
-// CHECK:STDOUT:   %p.var = alloca double, align 8, !dbg !16
-// CHECK:STDOUT:   %q.var = alloca double, align 8, !dbg !17
+// CHECK:STDOUT:   %p.var = alloca double, align 8, !dbg !15
 // CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %n.var), !dbg !14
 // CHECK:STDOUT:   store i32 0, ptr %n.var, align 4, !dbg !14
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %m.var), !dbg !15
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %p.var), !dbg !16
-// CHECK:STDOUT:   store double 1.000000e+00, ptr %p.var, align 8, !dbg !16
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %q.var), !dbg !17
-// CHECK:STDOUT:   %.loc54 = load i32, ptr %n.var, align 4, !dbg !18
-// CHECK:STDOUT:   call void @_CF.Main.b88d1103f417c6d4(i32 %.loc54), !dbg !19
-// CHECK:STDOUT:   %.loc55_9 = load i32, ptr %n.var, align 4, !dbg !20
-// CHECK:STDOUT:   %G.call.loc55 = call i32 @_CG.Main.68e44d468a50c22e(i32 %.loc55_9), !dbg !21
-// CHECK:STDOUT:   store i32 %G.call.loc55, ptr %m.var, align 4, !dbg !22
-// CHECK:STDOUT:   %.loc56 = load double, ptr %p.var, align 8, !dbg !23
-// CHECK:STDOUT:   call void @_CF.Main.d4b5665541d5d7a8(double %.loc56), !dbg !24
-// CHECK:STDOUT:   %.loc57_9 = load double, ptr %p.var, align 8, !dbg !25
-// CHECK:STDOUT:   %G.call.loc57 = call double @_CG.Main.c274f22d2c1ca5ee(double %.loc57_9), !dbg !26
-// CHECK:STDOUT:   store double %G.call.loc57, ptr %q.var, align 8, !dbg !27
-// CHECK:STDOUT:   ret void, !dbg !28
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %p.var), !dbg !15
+// CHECK:STDOUT:   store double 1.000000e+00, ptr %p.var, align 8, !dbg !15
+// CHECK:STDOUT:   %.loc52 = load i32, ptr %n.var, align 4, !dbg !16
+// CHECK:STDOUT:   call void @_CF.Main.b88d1103f417c6d4(i32 %.loc52), !dbg !17
+// CHECK:STDOUT:   %.loc53_18 = load i32, ptr %n.var, align 4, !dbg !18
+// CHECK:STDOUT:   %G.call.loc53 = call i32 @_CG.Main.68e44d468a50c22e(i32 %.loc53_18), !dbg !19
+// CHECK:STDOUT:   %.loc54 = load double, ptr %p.var, align 8, !dbg !20
+// CHECK:STDOUT:   call void @_CF.Main.d4b5665541d5d7a8(double %.loc54), !dbg !21
+// CHECK:STDOUT:   %.loc55_18 = load double, ptr %p.var, align 8, !dbg !22
+// CHECK:STDOUT:   %G.call.loc55 = call double @_CG.Main.c274f22d2c1ca5ee(double %.loc55_18), !dbg !23
+// CHECK:STDOUT:   ret void, !dbg !24
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nocallback nofree nounwind willreturn memory(argmem: readwrite)
@@ -104,132 +96,132 @@ fn M() {
 // CHECK:STDOUT: declare void @llvm.lifetime.start.p0(ptr captures(none)) #2
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
-// CHECK:STDOUT: define linkonce_odr void @_CF.Main.b88d1103f417c6d4(i32 %x) #0 !dbg !29 {
+// CHECK:STDOUT: define linkonce_odr void @_CF.Main.b88d1103f417c6d4(i32 %_) #0 !dbg !25 {
 // CHECK:STDOUT: entry:
-// CHECK:STDOUT:   ret void, !dbg !35
+// CHECK:STDOUT:   ret void, !dbg !31
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
-// CHECK:STDOUT: define linkonce_odr i32 @_CG.Main.68e44d468a50c22e(i32 %x) #0 !dbg !36 {
+// CHECK:STDOUT: define linkonce_odr i32 @_CG.Main.68e44d468a50c22e(i32 %x) #0 !dbg !32 {
 // CHECK:STDOUT: entry:
-// CHECK:STDOUT:   %.loc29_6.3.temp = alloca i32, align 4, !dbg !41
-// CHECK:STDOUT:   %.loc31_8.3.temp = alloca i32, align 4, !dbg !42
-// CHECK:STDOUT:   %.loc31_9.3.temp = alloca i32, align 4, !dbg !43
-// CHECK:STDOUT:   %var_f64.var = alloca double, align 8, !dbg !44
-// CHECK:STDOUT:   %ptr_i32.var = alloca ptr, align 8, !dbg !45
-// CHECK:STDOUT:   %ptr_f64.var = alloca ptr, align 8, !dbg !46
-// CHECK:STDOUT:   %ptr_i8.var = alloca ptr, align 8, !dbg !47
-// CHECK:STDOUT:   %c.var = alloca {}, align 8, !dbg !48
-// CHECK:STDOUT:   %.loc43_6.3.temp = alloca {}, align 8, !dbg !49
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %.loc29_6.3.temp), !dbg !41
-// CHECK:STDOUT:   %H.call.loc29 = call i32 @_CH.Main.3440082c84c3c17b(i32 %x), !dbg !41
-// CHECK:STDOUT:   store i32 %H.call.loc29, ptr %.loc29_6.3.temp, align 4, !dbg !41
-// CHECK:STDOUT:   %H.call.loc30 = call %type @_CH.Main.93e33f284107e304(%type zeroinitializer), !dbg !50
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %.loc31_8.3.temp), !dbg !42
-// CHECK:STDOUT:   %G.call = call i32 @_CG.Main.68e44d468a50c22e(i32 %x), !dbg !42
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %.loc31_9.3.temp), !dbg !43
-// CHECK:STDOUT:   store i32 %G.call, ptr %.loc31_8.3.temp, align 4, !dbg !42
-// CHECK:STDOUT:   %.loc31_8.5 = load i32, ptr %.loc31_8.3.temp, align 4, !dbg !42
-// CHECK:STDOUT:   %H.call.loc31 = call i32 @_CH.Main.3440082c84c3c17b(i32 %.loc31_8.5), !dbg !43
-// CHECK:STDOUT:   store i32 %H.call.loc31, ptr %.loc31_9.3.temp, align 4, !dbg !43
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %var_f64.var), !dbg !44
-// CHECK:STDOUT:   %.loc35_5 = load double, ptr %var_f64.var, align 8, !dbg !51
-// CHECK:STDOUT:   %H.call.loc35 = call double @_CH.Main.286b0f7890e5304c(double %.loc35_5), !dbg !52
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %ptr_i32.var), !dbg !45
-// CHECK:STDOUT:   %.loc37_5 = load ptr, ptr %ptr_i32.var, align 8, !dbg !53
-// CHECK:STDOUT:   %H.call.loc37 = call ptr @_CH.Main.4b30cda44e16b9ec(ptr %.loc37_5), !dbg !54
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %ptr_f64.var), !dbg !46
-// CHECK:STDOUT:   %.loc39_5 = load ptr, ptr %ptr_f64.var, align 8, !dbg !55
-// CHECK:STDOUT:   %H.call.loc39 = call ptr @_CH.Main.4b30cda44e16b9ec(ptr %.loc39_5), !dbg !56
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %ptr_i8.var), !dbg !47
-// CHECK:STDOUT:   %.loc41_5 = load ptr, ptr %ptr_i8.var, align 8, !dbg !57
-// CHECK:STDOUT:   %H.call.loc41 = call ptr @_CH.Main.4b30cda44e16b9ec(ptr %.loc41_5), !dbg !58
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %c.var), !dbg !48
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %.loc43_6.3.temp), !dbg !49
-// CHECK:STDOUT:   call void @_CH.Main.f8e70200fd9d8b37(ptr %.loc43_6.3.temp, ptr %c.var), !dbg !49
-// CHECK:STDOUT:   ret i32 %x, !dbg !59
+// CHECK:STDOUT:   %.loc29_6.3.temp = alloca i32, align 4, !dbg !37
+// CHECK:STDOUT:   %.loc31_8.3.temp = alloca i32, align 4, !dbg !38
+// CHECK:STDOUT:   %.loc31_9.3.temp = alloca i32, align 4, !dbg !39
+// CHECK:STDOUT:   %var_f64.var = alloca double, align 8, !dbg !40
+// CHECK:STDOUT:   %ptr_i32.var = alloca ptr, align 8, !dbg !41
+// CHECK:STDOUT:   %ptr_f64.var = alloca ptr, align 8, !dbg !42
+// CHECK:STDOUT:   %ptr_i8.var = alloca ptr, align 8, !dbg !43
+// CHECK:STDOUT:   %c.var = alloca {}, align 8, !dbg !44
+// CHECK:STDOUT:   %.loc43_6.3.temp = alloca {}, align 8, !dbg !45
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %.loc29_6.3.temp), !dbg !37
+// CHECK:STDOUT:   %H.call.loc29 = call i32 @_CH.Main.3440082c84c3c17b(i32 %x), !dbg !37
+// CHECK:STDOUT:   store i32 %H.call.loc29, ptr %.loc29_6.3.temp, align 4, !dbg !37
+// CHECK:STDOUT:   %H.call.loc30 = call %type @_CH.Main.93e33f284107e304(%type zeroinitializer), !dbg !46
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %.loc31_8.3.temp), !dbg !38
+// CHECK:STDOUT:   %G.call = call i32 @_CG.Main.68e44d468a50c22e(i32 %x), !dbg !38
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %.loc31_9.3.temp), !dbg !39
+// CHECK:STDOUT:   store i32 %G.call, ptr %.loc31_8.3.temp, align 4, !dbg !38
+// CHECK:STDOUT:   %.loc31_8.5 = load i32, ptr %.loc31_8.3.temp, align 4, !dbg !38
+// CHECK:STDOUT:   %H.call.loc31 = call i32 @_CH.Main.3440082c84c3c17b(i32 %.loc31_8.5), !dbg !39
+// CHECK:STDOUT:   store i32 %H.call.loc31, ptr %.loc31_9.3.temp, align 4, !dbg !39
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %var_f64.var), !dbg !40
+// CHECK:STDOUT:   %.loc35_5 = load double, ptr %var_f64.var, align 8, !dbg !47
+// CHECK:STDOUT:   %H.call.loc35 = call double @_CH.Main.286b0f7890e5304c(double %.loc35_5), !dbg !48
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %ptr_i32.var), !dbg !41
+// CHECK:STDOUT:   %.loc37_5 = load ptr, ptr %ptr_i32.var, align 8, !dbg !49
+// CHECK:STDOUT:   %H.call.loc37 = call ptr @_CH.Main.4b30cda44e16b9ec(ptr %.loc37_5), !dbg !50
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %ptr_f64.var), !dbg !42
+// CHECK:STDOUT:   %.loc39_5 = load ptr, ptr %ptr_f64.var, align 8, !dbg !51
+// CHECK:STDOUT:   %H.call.loc39 = call ptr @_CH.Main.4b30cda44e16b9ec(ptr %.loc39_5), !dbg !52
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %ptr_i8.var), !dbg !43
+// CHECK:STDOUT:   %.loc41_5 = load ptr, ptr %ptr_i8.var, align 8, !dbg !53
+// CHECK:STDOUT:   %H.call.loc41 = call ptr @_CH.Main.4b30cda44e16b9ec(ptr %.loc41_5), !dbg !54
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %c.var), !dbg !44
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %.loc43_6.3.temp), !dbg !45
+// CHECK:STDOUT:   call void @_CH.Main.f8e70200fd9d8b37(ptr %.loc43_6.3.temp, ptr %c.var), !dbg !45
+// CHECK:STDOUT:   ret i32 %x, !dbg !55
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
-// CHECK:STDOUT: define linkonce_odr void @_CF.Main.d4b5665541d5d7a8(double %x) #0 !dbg !60 {
+// CHECK:STDOUT: define linkonce_odr void @_CF.Main.d4b5665541d5d7a8(double %_) #0 !dbg !56 {
 // CHECK:STDOUT: entry:
-// CHECK:STDOUT:   ret void, !dbg !65
+// CHECK:STDOUT:   ret void, !dbg !61
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
-// CHECK:STDOUT: define linkonce_odr double @_CG.Main.c274f22d2c1ca5ee(double %x) #0 !dbg !66 {
+// CHECK:STDOUT: define linkonce_odr double @_CG.Main.c274f22d2c1ca5ee(double %x) #0 !dbg !62 {
 // CHECK:STDOUT: entry:
-// CHECK:STDOUT:   %.loc29_6.3.temp = alloca double, align 8, !dbg !69
-// CHECK:STDOUT:   %.loc31_8.3.temp = alloca double, align 8, !dbg !70
-// CHECK:STDOUT:   %.loc31_9.3.temp = alloca double, align 8, !dbg !71
-// CHECK:STDOUT:   %var_f64.var = alloca double, align 8, !dbg !72
-// CHECK:STDOUT:   %ptr_i32.var = alloca ptr, align 8, !dbg !73
-// CHECK:STDOUT:   %ptr_f64.var = alloca ptr, align 8, !dbg !74
-// CHECK:STDOUT:   %ptr_i8.var = alloca ptr, align 8, !dbg !75
-// CHECK:STDOUT:   %c.var = alloca {}, align 8, !dbg !76
-// CHECK:STDOUT:   %.loc43_6.3.temp = alloca {}, align 8, !dbg !77
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %.loc29_6.3.temp), !dbg !69
-// CHECK:STDOUT:   %H.call.loc29 = call double @_CH.Main.286b0f7890e5304c(double %x), !dbg !69
-// CHECK:STDOUT:   store double %H.call.loc29, ptr %.loc29_6.3.temp, align 8, !dbg !69
-// CHECK:STDOUT:   %H.call.loc30 = call %type @_CH.Main.93e33f284107e304(%type zeroinitializer), !dbg !78
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %.loc31_8.3.temp), !dbg !70
-// CHECK:STDOUT:   %G.call = call double @_CG.Main.c274f22d2c1ca5ee(double %x), !dbg !70
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %.loc31_9.3.temp), !dbg !71
-// CHECK:STDOUT:   store double %G.call, ptr %.loc31_8.3.temp, align 8, !dbg !70
-// CHECK:STDOUT:   %.loc31_8.5 = load double, ptr %.loc31_8.3.temp, align 8, !dbg !70
-// CHECK:STDOUT:   %H.call.loc31 = call double @_CH.Main.286b0f7890e5304c(double %.loc31_8.5), !dbg !71
-// CHECK:STDOUT:   store double %H.call.loc31, ptr %.loc31_9.3.temp, align 8, !dbg !71
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %var_f64.var), !dbg !72
-// CHECK:STDOUT:   %.loc35_5 = load double, ptr %var_f64.var, align 8, !dbg !79
-// CHECK:STDOUT:   %H.call.loc35 = call double @_CH.Main.286b0f7890e5304c(double %.loc35_5), !dbg !80
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %ptr_i32.var), !dbg !73
-// CHECK:STDOUT:   %.loc37_5 = load ptr, ptr %ptr_i32.var, align 8, !dbg !81
-// CHECK:STDOUT:   %H.call.loc37 = call ptr @_CH.Main.4b30cda44e16b9ec(ptr %.loc37_5), !dbg !82
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %ptr_f64.var), !dbg !74
-// CHECK:STDOUT:   %.loc39_5 = load ptr, ptr %ptr_f64.var, align 8, !dbg !83
-// CHECK:STDOUT:   %H.call.loc39 = call ptr @_CH.Main.4b30cda44e16b9ec(ptr %.loc39_5), !dbg !84
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %ptr_i8.var), !dbg !75
-// CHECK:STDOUT:   %.loc41_5 = load ptr, ptr %ptr_i8.var, align 8, !dbg !85
-// CHECK:STDOUT:   %H.call.loc41 = call ptr @_CH.Main.4b30cda44e16b9ec(ptr %.loc41_5), !dbg !86
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %c.var), !dbg !76
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %.loc43_6.3.temp), !dbg !77
-// CHECK:STDOUT:   call void @_CH.Main.f8e70200fd9d8b37(ptr %.loc43_6.3.temp, ptr %c.var), !dbg !77
-// CHECK:STDOUT:   ret double %x, !dbg !87
+// CHECK:STDOUT:   %.loc29_6.3.temp = alloca double, align 8, !dbg !65
+// CHECK:STDOUT:   %.loc31_8.3.temp = alloca double, align 8, !dbg !66
+// CHECK:STDOUT:   %.loc31_9.3.temp = alloca double, align 8, !dbg !67
+// CHECK:STDOUT:   %var_f64.var = alloca double, align 8, !dbg !68
+// CHECK:STDOUT:   %ptr_i32.var = alloca ptr, align 8, !dbg !69
+// CHECK:STDOUT:   %ptr_f64.var = alloca ptr, align 8, !dbg !70
+// CHECK:STDOUT:   %ptr_i8.var = alloca ptr, align 8, !dbg !71
+// CHECK:STDOUT:   %c.var = alloca {}, align 8, !dbg !72
+// CHECK:STDOUT:   %.loc43_6.3.temp = alloca {}, align 8, !dbg !73
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %.loc29_6.3.temp), !dbg !65
+// CHECK:STDOUT:   %H.call.loc29 = call double @_CH.Main.286b0f7890e5304c(double %x), !dbg !65
+// CHECK:STDOUT:   store double %H.call.loc29, ptr %.loc29_6.3.temp, align 8, !dbg !65
+// CHECK:STDOUT:   %H.call.loc30 = call %type @_CH.Main.93e33f284107e304(%type zeroinitializer), !dbg !74
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %.loc31_8.3.temp), !dbg !66
+// CHECK:STDOUT:   %G.call = call double @_CG.Main.c274f22d2c1ca5ee(double %x), !dbg !66
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %.loc31_9.3.temp), !dbg !67
+// CHECK:STDOUT:   store double %G.call, ptr %.loc31_8.3.temp, align 8, !dbg !66
+// CHECK:STDOUT:   %.loc31_8.5 = load double, ptr %.loc31_8.3.temp, align 8, !dbg !66
+// CHECK:STDOUT:   %H.call.loc31 = call double @_CH.Main.286b0f7890e5304c(double %.loc31_8.5), !dbg !67
+// CHECK:STDOUT:   store double %H.call.loc31, ptr %.loc31_9.3.temp, align 8, !dbg !67
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %var_f64.var), !dbg !68
+// CHECK:STDOUT:   %.loc35_5 = load double, ptr %var_f64.var, align 8, !dbg !75
+// CHECK:STDOUT:   %H.call.loc35 = call double @_CH.Main.286b0f7890e5304c(double %.loc35_5), !dbg !76
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %ptr_i32.var), !dbg !69
+// CHECK:STDOUT:   %.loc37_5 = load ptr, ptr %ptr_i32.var, align 8, !dbg !77
+// CHECK:STDOUT:   %H.call.loc37 = call ptr @_CH.Main.4b30cda44e16b9ec(ptr %.loc37_5), !dbg !78
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %ptr_f64.var), !dbg !70
+// CHECK:STDOUT:   %.loc39_5 = load ptr, ptr %ptr_f64.var, align 8, !dbg !79
+// CHECK:STDOUT:   %H.call.loc39 = call ptr @_CH.Main.4b30cda44e16b9ec(ptr %.loc39_5), !dbg !80
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %ptr_i8.var), !dbg !71
+// CHECK:STDOUT:   %.loc41_5 = load ptr, ptr %ptr_i8.var, align 8, !dbg !81
+// CHECK:STDOUT:   %H.call.loc41 = call ptr @_CH.Main.4b30cda44e16b9ec(ptr %.loc41_5), !dbg !82
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %c.var), !dbg !72
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %.loc43_6.3.temp), !dbg !73
+// CHECK:STDOUT:   call void @_CH.Main.f8e70200fd9d8b37(ptr %.loc43_6.3.temp, ptr %c.var), !dbg !73
+// CHECK:STDOUT:   ret double %x, !dbg !83
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
-// CHECK:STDOUT: define linkonce_odr i32 @_CH.Main.3440082c84c3c17b(i32 %x) #0 !dbg !88 {
+// CHECK:STDOUT: define linkonce_odr i32 @_CH.Main.3440082c84c3c17b(i32 %x) #0 !dbg !84 {
 // CHECK:STDOUT: entry:
-// CHECK:STDOUT:   ret i32 %x, !dbg !91
+// CHECK:STDOUT:   ret i32 %x, !dbg !87
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
-// CHECK:STDOUT: define linkonce_odr %type @_CH.Main.93e33f284107e304(%type %x) #0 !dbg !92 {
+// CHECK:STDOUT: define linkonce_odr %type @_CH.Main.93e33f284107e304(%type %x) #0 !dbg !88 {
 // CHECK:STDOUT: entry:
-// CHECK:STDOUT:   ret %type %x, !dbg !95
+// CHECK:STDOUT:   ret %type %x, !dbg !91
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
-// CHECK:STDOUT: define linkonce_odr double @_CH.Main.286b0f7890e5304c(double %x) #0 !dbg !96 {
+// CHECK:STDOUT: define linkonce_odr double @_CH.Main.286b0f7890e5304c(double %x) #0 !dbg !92 {
 // CHECK:STDOUT: entry:
-// CHECK:STDOUT:   ret double %x, !dbg !99
+// CHECK:STDOUT:   ret double %x, !dbg !95
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
-// CHECK:STDOUT: define linkonce_odr ptr @_CH.Main.4b30cda44e16b9ec(ptr %x) #0 !dbg !100 {
+// CHECK:STDOUT: define linkonce_odr ptr @_CH.Main.4b30cda44e16b9ec(ptr %x) #0 !dbg !96 {
 // CHECK:STDOUT: entry:
-// CHECK:STDOUT:   ret ptr %x, !dbg !103
+// CHECK:STDOUT:   ret ptr %x, !dbg !99
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
-// CHECK:STDOUT: define linkonce_odr void @_CH.Main.f8e70200fd9d8b37(ptr sret({}) %return, ptr %x) #0 !dbg !104 {
+// CHECK:STDOUT: define linkonce_odr void @_CH.Main.f8e70200fd9d8b37(ptr sret({}) %return, ptr %x) #0 !dbg !100 {
 // CHECK:STDOUT: entry:
-// CHECK:STDOUT:   call void @"_COp.C.Main:Copy.Core"(ptr %return, ptr %x), !dbg !107
-// CHECK:STDOUT:   ret void, !dbg !108
+// CHECK:STDOUT:   call void @"_COp.C.Main:Copy.Core"(ptr %return, ptr %x), !dbg !103
+// CHECK:STDOUT:   ret void, !dbg !104
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; uselistorder directives
-// CHECK:STDOUT: uselistorder ptr @llvm.lifetime.start.p0, { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 21, 20, 19, 18 }
+// CHECK:STDOUT: uselistorder ptr @llvm.lifetime.start.p0, { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 19, 18 }
 // CHECK:STDOUT: uselistorder ptr @_CH.Main.3440082c84c3c17b, { 1, 0 }
 // CHECK:STDOUT: uselistorder ptr @_CH.Main.93e33f284107e304, { 1, 0 }
 // CHECK:STDOUT: uselistorder ptr @_CH.Main.286b0f7890e5304c, { 3, 2, 1, 0 }
@@ -259,96 +251,92 @@ fn M() {
 // CHECK:STDOUT: !13 = !{null}
 // CHECK:STDOUT: !14 = !DILocation(line: 49, column: 3, scope: !11)
 // CHECK:STDOUT: !15 = !DILocation(line: 50, column: 3, scope: !11)
-// CHECK:STDOUT: !16 = !DILocation(line: 51, column: 3, scope: !11)
+// CHECK:STDOUT: !16 = !DILocation(line: 52, column: 5, scope: !11)
 // CHECK:STDOUT: !17 = !DILocation(line: 52, column: 3, scope: !11)
-// CHECK:STDOUT: !18 = !DILocation(line: 54, column: 5, scope: !11)
-// CHECK:STDOUT: !19 = !DILocation(line: 54, column: 3, scope: !11)
-// CHECK:STDOUT: !20 = !DILocation(line: 55, column: 9, scope: !11)
-// CHECK:STDOUT: !21 = !DILocation(line: 55, column: 7, scope: !11)
-// CHECK:STDOUT: !22 = !DILocation(line: 55, column: 3, scope: !11)
-// CHECK:STDOUT: !23 = !DILocation(line: 56, column: 5, scope: !11)
-// CHECK:STDOUT: !24 = !DILocation(line: 56, column: 3, scope: !11)
-// CHECK:STDOUT: !25 = !DILocation(line: 57, column: 9, scope: !11)
-// CHECK:STDOUT: !26 = !DILocation(line: 57, column: 7, scope: !11)
-// CHECK:STDOUT: !27 = !DILocation(line: 57, column: 3, scope: !11)
-// CHECK:STDOUT: !28 = !DILocation(line: 48, column: 1, scope: !11)
-// CHECK:STDOUT: !29 = distinct !DISubprogram(name: "F", linkageName: "_CF.Main.b88d1103f417c6d4", scope: null, file: !3, line: 19, type: !30, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !33)
-// CHECK:STDOUT: !30 = !DISubroutineType(types: !31)
-// CHECK:STDOUT: !31 = !{null, !32}
-// CHECK:STDOUT: !32 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
-// CHECK:STDOUT: !33 = !{!34}
-// CHECK:STDOUT: !34 = !DILocalVariable(arg: 1, scope: !29, type: !32)
-// CHECK:STDOUT: !35 = !DILocation(line: 19, column: 1, scope: !29)
-// CHECK:STDOUT: !36 = distinct !DISubprogram(name: "G", linkageName: "_CG.Main.68e44d468a50c22e", scope: null, file: !3, line: 28, type: !37, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !39)
-// CHECK:STDOUT: !37 = !DISubroutineType(types: !38)
-// CHECK:STDOUT: !38 = !{!32, !32}
-// CHECK:STDOUT: !39 = !{!40}
-// CHECK:STDOUT: !40 = !DILocalVariable(arg: 1, scope: !36, type: !32)
-// CHECK:STDOUT: !41 = !DILocation(line: 29, column: 3, scope: !36)
-// CHECK:STDOUT: !42 = !DILocation(line: 31, column: 5, scope: !36)
-// CHECK:STDOUT: !43 = !DILocation(line: 31, column: 3, scope: !36)
-// CHECK:STDOUT: !44 = !DILocation(line: 34, column: 3, scope: !36)
-// CHECK:STDOUT: !45 = !DILocation(line: 36, column: 3, scope: !36)
-// CHECK:STDOUT: !46 = !DILocation(line: 38, column: 3, scope: !36)
-// CHECK:STDOUT: !47 = !DILocation(line: 40, column: 3, scope: !36)
-// CHECK:STDOUT: !48 = !DILocation(line: 42, column: 3, scope: !36)
-// CHECK:STDOUT: !49 = !DILocation(line: 43, column: 3, scope: !36)
-// CHECK:STDOUT: !50 = !DILocation(line: 30, column: 3, scope: !36)
-// CHECK:STDOUT: !51 = !DILocation(line: 35, column: 5, scope: !36)
-// CHECK:STDOUT: !52 = !DILocation(line: 35, column: 3, scope: !36)
-// CHECK:STDOUT: !53 = !DILocation(line: 37, column: 5, scope: !36)
-// CHECK:STDOUT: !54 = !DILocation(line: 37, column: 3, scope: !36)
-// CHECK:STDOUT: !55 = !DILocation(line: 39, column: 5, scope: !36)
-// CHECK:STDOUT: !56 = !DILocation(line: 39, column: 3, scope: !36)
-// CHECK:STDOUT: !57 = !DILocation(line: 41, column: 5, scope: !36)
-// CHECK:STDOUT: !58 = !DILocation(line: 41, column: 3, scope: !36)
-// CHECK:STDOUT: !59 = !DILocation(line: 45, column: 3, scope: !36)
-// CHECK:STDOUT: !60 = distinct !DISubprogram(name: "F", linkageName: "_CF.Main.d4b5665541d5d7a8", scope: null, file: !3, line: 19, type: !61, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !63)
-// CHECK:STDOUT: !61 = !DISubroutineType(types: !62)
-// CHECK:STDOUT: !62 = !{null, !7}
+// CHECK:STDOUT: !18 = !DILocation(line: 53, column: 18, scope: !11)
+// CHECK:STDOUT: !19 = !DILocation(line: 53, column: 16, scope: !11)
+// CHECK:STDOUT: !20 = !DILocation(line: 54, column: 5, scope: !11)
+// CHECK:STDOUT: !21 = !DILocation(line: 54, column: 3, scope: !11)
+// CHECK:STDOUT: !22 = !DILocation(line: 55, column: 18, scope: !11)
+// CHECK:STDOUT: !23 = !DILocation(line: 55, column: 16, scope: !11)
+// CHECK:STDOUT: !24 = !DILocation(line: 48, column: 1, scope: !11)
+// CHECK:STDOUT: !25 = distinct !DISubprogram(name: "F", linkageName: "_CF.Main.b88d1103f417c6d4", scope: null, file: !3, line: 19, type: !26, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !29)
+// CHECK:STDOUT: !26 = !DISubroutineType(types: !27)
+// CHECK:STDOUT: !27 = !{null, !28}
+// CHECK:STDOUT: !28 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+// CHECK:STDOUT: !29 = !{!30}
+// CHECK:STDOUT: !30 = !DILocalVariable(arg: 1, scope: !25, type: !28)
+// CHECK:STDOUT: !31 = !DILocation(line: 19, column: 1, scope: !25)
+// CHECK:STDOUT: !32 = distinct !DISubprogram(name: "G", linkageName: "_CG.Main.68e44d468a50c22e", scope: null, file: !3, line: 28, type: !33, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !35)
+// CHECK:STDOUT: !33 = !DISubroutineType(types: !34)
+// CHECK:STDOUT: !34 = !{!28, !28}
+// CHECK:STDOUT: !35 = !{!36}
+// CHECK:STDOUT: !36 = !DILocalVariable(arg: 1, scope: !32, type: !28)
+// CHECK:STDOUT: !37 = !DILocation(line: 29, column: 3, scope: !32)
+// CHECK:STDOUT: !38 = !DILocation(line: 31, column: 5, scope: !32)
+// CHECK:STDOUT: !39 = !DILocation(line: 31, column: 3, scope: !32)
+// CHECK:STDOUT: !40 = !DILocation(line: 34, column: 3, scope: !32)
+// CHECK:STDOUT: !41 = !DILocation(line: 36, column: 3, scope: !32)
+// CHECK:STDOUT: !42 = !DILocation(line: 38, column: 3, scope: !32)
+// CHECK:STDOUT: !43 = !DILocation(line: 40, column: 3, scope: !32)
+// CHECK:STDOUT: !44 = !DILocation(line: 42, column: 3, scope: !32)
+// CHECK:STDOUT: !45 = !DILocation(line: 43, column: 3, scope: !32)
+// CHECK:STDOUT: !46 = !DILocation(line: 30, column: 3, scope: !32)
+// CHECK:STDOUT: !47 = !DILocation(line: 35, column: 5, scope: !32)
+// CHECK:STDOUT: !48 = !DILocation(line: 35, column: 3, scope: !32)
+// CHECK:STDOUT: !49 = !DILocation(line: 37, column: 5, scope: !32)
+// CHECK:STDOUT: !50 = !DILocation(line: 37, column: 3, scope: !32)
+// CHECK:STDOUT: !51 = !DILocation(line: 39, column: 5, scope: !32)
+// CHECK:STDOUT: !52 = !DILocation(line: 39, column: 3, scope: !32)
+// CHECK:STDOUT: !53 = !DILocation(line: 41, column: 5, scope: !32)
+// CHECK:STDOUT: !54 = !DILocation(line: 41, column: 3, scope: !32)
+// CHECK:STDOUT: !55 = !DILocation(line: 45, column: 3, scope: !32)
+// CHECK:STDOUT: !56 = distinct !DISubprogram(name: "F", linkageName: "_CF.Main.d4b5665541d5d7a8", scope: null, file: !3, line: 19, type: !57, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !59)
+// CHECK:STDOUT: !57 = !DISubroutineType(types: !58)
+// CHECK:STDOUT: !58 = !{null, !7}
+// CHECK:STDOUT: !59 = !{!60}
+// CHECK:STDOUT: !60 = !DILocalVariable(arg: 1, scope: !56, type: !7)
+// CHECK:STDOUT: !61 = !DILocation(line: 19, column: 1, scope: !56)
+// CHECK:STDOUT: !62 = distinct !DISubprogram(name: "G", linkageName: "_CG.Main.c274f22d2c1ca5ee", scope: null, file: !3, line: 28, type: !5, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !63)
 // CHECK:STDOUT: !63 = !{!64}
-// CHECK:STDOUT: !64 = !DILocalVariable(arg: 1, scope: !60, type: !7)
-// CHECK:STDOUT: !65 = !DILocation(line: 19, column: 1, scope: !60)
-// CHECK:STDOUT: !66 = distinct !DISubprogram(name: "G", linkageName: "_CG.Main.c274f22d2c1ca5ee", scope: null, file: !3, line: 28, type: !5, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !67)
-// CHECK:STDOUT: !67 = !{!68}
-// CHECK:STDOUT: !68 = !DILocalVariable(arg: 1, scope: !66, type: !7)
-// CHECK:STDOUT: !69 = !DILocation(line: 29, column: 3, scope: !66)
-// CHECK:STDOUT: !70 = !DILocation(line: 31, column: 5, scope: !66)
-// CHECK:STDOUT: !71 = !DILocation(line: 31, column: 3, scope: !66)
-// CHECK:STDOUT: !72 = !DILocation(line: 34, column: 3, scope: !66)
-// CHECK:STDOUT: !73 = !DILocation(line: 36, column: 3, scope: !66)
-// CHECK:STDOUT: !74 = !DILocation(line: 38, column: 3, scope: !66)
-// CHECK:STDOUT: !75 = !DILocation(line: 40, column: 3, scope: !66)
-// CHECK:STDOUT: !76 = !DILocation(line: 42, column: 3, scope: !66)
-// CHECK:STDOUT: !77 = !DILocation(line: 43, column: 3, scope: !66)
-// CHECK:STDOUT: !78 = !DILocation(line: 30, column: 3, scope: !66)
-// CHECK:STDOUT: !79 = !DILocation(line: 35, column: 5, scope: !66)
-// CHECK:STDOUT: !80 = !DILocation(line: 35, column: 3, scope: !66)
-// CHECK:STDOUT: !81 = !DILocation(line: 37, column: 5, scope: !66)
-// CHECK:STDOUT: !82 = !DILocation(line: 37, column: 3, scope: !66)
-// CHECK:STDOUT: !83 = !DILocation(line: 39, column: 5, scope: !66)
-// CHECK:STDOUT: !84 = !DILocation(line: 39, column: 3, scope: !66)
-// CHECK:STDOUT: !85 = !DILocation(line: 41, column: 5, scope: !66)
-// CHECK:STDOUT: !86 = !DILocation(line: 41, column: 3, scope: !66)
-// CHECK:STDOUT: !87 = !DILocation(line: 45, column: 3, scope: !66)
-// CHECK:STDOUT: !88 = distinct !DISubprogram(name: "H", linkageName: "_CH.Main.3440082c84c3c17b", scope: null, file: !3, line: 22, type: !37, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !89)
+// CHECK:STDOUT: !64 = !DILocalVariable(arg: 1, scope: !62, type: !7)
+// CHECK:STDOUT: !65 = !DILocation(line: 29, column: 3, scope: !62)
+// CHECK:STDOUT: !66 = !DILocation(line: 31, column: 5, scope: !62)
+// CHECK:STDOUT: !67 = !DILocation(line: 31, column: 3, scope: !62)
+// CHECK:STDOUT: !68 = !DILocation(line: 34, column: 3, scope: !62)
+// CHECK:STDOUT: !69 = !DILocation(line: 36, column: 3, scope: !62)
+// CHECK:STDOUT: !70 = !DILocation(line: 38, column: 3, scope: !62)
+// CHECK:STDOUT: !71 = !DILocation(line: 40, column: 3, scope: !62)
+// CHECK:STDOUT: !72 = !DILocation(line: 42, column: 3, scope: !62)
+// CHECK:STDOUT: !73 = !DILocation(line: 43, column: 3, scope: !62)
+// CHECK:STDOUT: !74 = !DILocation(line: 30, column: 3, scope: !62)
+// CHECK:STDOUT: !75 = !DILocation(line: 35, column: 5, scope: !62)
+// CHECK:STDOUT: !76 = !DILocation(line: 35, column: 3, scope: !62)
+// CHECK:STDOUT: !77 = !DILocation(line: 37, column: 5, scope: !62)
+// CHECK:STDOUT: !78 = !DILocation(line: 37, column: 3, scope: !62)
+// CHECK:STDOUT: !79 = !DILocation(line: 39, column: 5, scope: !62)
+// CHECK:STDOUT: !80 = !DILocation(line: 39, column: 3, scope: !62)
+// CHECK:STDOUT: !81 = !DILocation(line: 41, column: 5, scope: !62)
+// CHECK:STDOUT: !82 = !DILocation(line: 41, column: 3, scope: !62)
+// CHECK:STDOUT: !83 = !DILocation(line: 45, column: 3, scope: !62)
+// CHECK:STDOUT: !84 = distinct !DISubprogram(name: "H", linkageName: "_CH.Main.3440082c84c3c17b", scope: null, file: !3, line: 22, type: !33, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !85)
+// CHECK:STDOUT: !85 = !{!86}
+// CHECK:STDOUT: !86 = !DILocalVariable(arg: 1, scope: !84, type: !28)
+// CHECK:STDOUT: !87 = !DILocation(line: 23, column: 3, scope: !84)
+// CHECK:STDOUT: !88 = distinct !DISubprogram(name: "H", linkageName: "_CH.Main.93e33f284107e304", scope: null, file: !3, line: 22, type: !5, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !89)
 // CHECK:STDOUT: !89 = !{!90}
-// CHECK:STDOUT: !90 = !DILocalVariable(arg: 1, scope: !88, type: !32)
+// CHECK:STDOUT: !90 = !DILocalVariable(arg: 1, scope: !88, type: !7)
 // CHECK:STDOUT: !91 = !DILocation(line: 23, column: 3, scope: !88)
-// CHECK:STDOUT: !92 = distinct !DISubprogram(name: "H", linkageName: "_CH.Main.93e33f284107e304", scope: null, file: !3, line: 22, type: !5, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !93)
+// CHECK:STDOUT: !92 = distinct !DISubprogram(name: "H", linkageName: "_CH.Main.286b0f7890e5304c", scope: null, file: !3, line: 22, type: !5, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !93)
 // CHECK:STDOUT: !93 = !{!94}
 // CHECK:STDOUT: !94 = !DILocalVariable(arg: 1, scope: !92, type: !7)
 // CHECK:STDOUT: !95 = !DILocation(line: 23, column: 3, scope: !92)
-// CHECK:STDOUT: !96 = distinct !DISubprogram(name: "H", linkageName: "_CH.Main.286b0f7890e5304c", scope: null, file: !3, line: 22, type: !5, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !97)
+// CHECK:STDOUT: !96 = distinct !DISubprogram(name: "H", linkageName: "_CH.Main.4b30cda44e16b9ec", scope: null, file: !3, line: 22, type: !5, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !97)
 // CHECK:STDOUT: !97 = !{!98}
 // CHECK:STDOUT: !98 = !DILocalVariable(arg: 1, scope: !96, type: !7)
 // CHECK:STDOUT: !99 = !DILocation(line: 23, column: 3, scope: !96)
-// CHECK:STDOUT: !100 = distinct !DISubprogram(name: "H", linkageName: "_CH.Main.4b30cda44e16b9ec", scope: null, file: !3, line: 22, type: !5, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !101)
+// CHECK:STDOUT: !100 = distinct !DISubprogram(name: "H", linkageName: "_CH.Main.f8e70200fd9d8b37", scope: null, file: !3, line: 22, type: !5, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !101)
 // CHECK:STDOUT: !101 = !{!102}
 // CHECK:STDOUT: !102 = !DILocalVariable(arg: 1, scope: !100, type: !7)
-// CHECK:STDOUT: !103 = !DILocation(line: 23, column: 3, scope: !100)
-// CHECK:STDOUT: !104 = distinct !DISubprogram(name: "H", linkageName: "_CH.Main.f8e70200fd9d8b37", scope: null, file: !3, line: 22, type: !5, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !105)
-// CHECK:STDOUT: !105 = !{!106}
-// CHECK:STDOUT: !106 = !DILocalVariable(arg: 1, scope: !104, type: !7)
-// CHECK:STDOUT: !107 = !DILocation(line: 23, column: 10, scope: !104)
-// CHECK:STDOUT: !108 = !DILocation(line: 23, column: 3, scope: !104)
+// CHECK:STDOUT: !103 = !DILocation(line: 23, column: 10, scope: !100)
+// CHECK:STDOUT: !104 = !DILocation(line: 23, column: 3, scope: !100)
diff --git a/toolchain/lower/testdata/function/generic/call_basic_depth.carbon b/toolchain/lower/testdata/function/generic/call_basic_depth.carbon
index a746c6550fae..14fa33b67b39 100644
--- a/toolchain/lower/testdata/function/generic/call_basic_depth.carbon
+++ b/toolchain/lower/testdata/function/generic/call_basic_depth.carbon
@@ -13,7 +13,7 @@
 // Builds on `call_basic.carbon`. Checks definitions are emitted with deeper
 // call stack, i.e., when functions can be type checked without looking at the
 // specific calling context.
-fn F[T:! type](x: T) {
+fn F[T:! type](_: T) {
 }
 
 fn H[T:! Core.Copy](x: T) -> T {
@@ -27,58 +27,60 @@ fn G[T:! Core.Copy & Core.Destroy](x: T) -> T {
   return x;
 }
 
-fn M() {
+fn M() -> i32 {
   var n: i32 = 0;
   var m: i32;
 
   F(n);
   m = G(n);
+  return m;
 }
 
 // CHECK:STDOUT: ; ModuleID = 'call_basic_depth.carbon'
 // CHECK:STDOUT: source_filename = "call_basic_depth.carbon"
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
-// CHECK:STDOUT: define void @_CM.Main() #0 !dbg !4 {
+// CHECK:STDOUT: define i32 @_CM.Main() #0 !dbg !4 {
 // CHECK:STDOUT: entry:
-// CHECK:STDOUT:   %n.var = alloca i32, align 4, !dbg !7
-// CHECK:STDOUT:   %m.var = alloca i32, align 4, !dbg !8
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %n.var), !dbg !7
-// CHECK:STDOUT:   store i32 0, ptr %n.var, align 4, !dbg !7
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %m.var), !dbg !8
-// CHECK:STDOUT:   %.loc34 = load i32, ptr %n.var, align 4, !dbg !9
-// CHECK:STDOUT:   call void @_CF.Main.b88d1103f417c6d4(i32 %.loc34), !dbg !10
-// CHECK:STDOUT:   %.loc35_9 = load i32, ptr %n.var, align 4, !dbg !11
-// CHECK:STDOUT:   %G.call = call i32 @_CG.Main.68e44d468a50c22e(i32 %.loc35_9), !dbg !12
-// CHECK:STDOUT:   store i32 %G.call, ptr %m.var, align 4, !dbg !13
-// CHECK:STDOUT:   ret void, !dbg !14
+// CHECK:STDOUT:   %n.var = alloca i32, align 4, !dbg !8
+// CHECK:STDOUT:   %m.var = alloca i32, align 4, !dbg !9
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %n.var), !dbg !8
+// CHECK:STDOUT:   store i32 0, ptr %n.var, align 4, !dbg !8
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %m.var), !dbg !9
+// CHECK:STDOUT:   %.loc34 = load i32, ptr %n.var, align 4, !dbg !10
+// CHECK:STDOUT:   call void @_CF.Main.b88d1103f417c6d4(i32 %.loc34), !dbg !11
+// CHECK:STDOUT:   %.loc35_9 = load i32, ptr %n.var, align 4, !dbg !12
+// CHECK:STDOUT:   %G.call = call i32 @_CG.Main.68e44d468a50c22e(i32 %.loc35_9), !dbg !13
+// CHECK:STDOUT:   store i32 %G.call, ptr %m.var, align 4, !dbg !14
+// CHECK:STDOUT:   %.loc36 = load i32, ptr %m.var, align 4, !dbg !15
+// CHECK:STDOUT:   ret i32 %.loc36, !dbg !16
 // CHECK:STDOUT: }
 // 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)) #1
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
-// CHECK:STDOUT: define linkonce_odr void @_CF.Main.b88d1103f417c6d4(i32 %x) #0 !dbg !15 {
+// CHECK:STDOUT: define linkonce_odr void @_CF.Main.b88d1103f417c6d4(i32 %_) #0 !dbg !17 {
 // CHECK:STDOUT: entry:
-// CHECK:STDOUT:   ret void, !dbg !21
+// CHECK:STDOUT:   ret void, !dbg !22
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
-// CHECK:STDOUT: define linkonce_odr i32 @_CG.Main.68e44d468a50c22e(i32 %x) #0 !dbg !22 {
+// CHECK:STDOUT: define linkonce_odr i32 @_CG.Main.68e44d468a50c22e(i32 %x) #0 !dbg !23 {
 // CHECK:STDOUT: entry:
-// CHECK:STDOUT:   %.loc25_6.3.temp = alloca i32, align 4, !dbg !27
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %.loc25_6.3.temp), !dbg !27
-// CHECK:STDOUT:   %H.call = call i32 @_CH.Main.3440082c84c3c17b(i32 %x), !dbg !27
-// CHECK:STDOUT:   store i32 %H.call, ptr %.loc25_6.3.temp, align 4, !dbg !27
-// CHECK:STDOUT:   call void @_CF.Main.b88d1103f417c6d4(i32 %x), !dbg !28
-// CHECK:STDOUT:   ret i32 %x, !dbg !29
+// CHECK:STDOUT:   %.loc25_6.3.temp = alloca i32, align 4, !dbg !28
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %.loc25_6.3.temp), !dbg !28
+// CHECK:STDOUT:   %H.call = call i32 @_CH.Main.3440082c84c3c17b(i32 %x), !dbg !28
+// CHECK:STDOUT:   store i32 %H.call, ptr %.loc25_6.3.temp, align 4, !dbg !28
+// CHECK:STDOUT:   call void @_CF.Main.b88d1103f417c6d4(i32 %x), !dbg !29
+// CHECK:STDOUT:   ret i32 %x, !dbg !30
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
-// CHECK:STDOUT: define linkonce_odr i32 @_CH.Main.3440082c84c3c17b(i32 %x) #0 !dbg !30 {
+// CHECK:STDOUT: define linkonce_odr i32 @_CH.Main.3440082c84c3c17b(i32 %x) #0 !dbg !31 {
 // CHECK:STDOUT: entry:
-// CHECK:STDOUT:   call void @_CF.Main.b88d1103f417c6d4(i32 %x), !dbg !33
-// CHECK:STDOUT:   ret i32 %x, !dbg !34
+// CHECK:STDOUT:   call void @_CF.Main.b88d1103f417c6d4(i32 %x), !dbg !34
+// CHECK:STDOUT:   ret i32 %x, !dbg !35
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; uselistorder directives
@@ -96,32 +98,33 @@ fn M() {
 // CHECK:STDOUT: !3 = !DIFile(filename: "call_basic_depth.carbon", directory: "")
 // CHECK:STDOUT: !4 = distinct !DISubprogram(name: "M", linkageName: "_CM.Main", scope: null, file: !3, line: 30, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
-// CHECK:STDOUT: !6 = !{null}
-// CHECK:STDOUT: !7 = !DILocation(line: 31, column: 3, scope: !4)
-// CHECK:STDOUT: !8 = !DILocation(line: 32, column: 3, scope: !4)
-// CHECK:STDOUT: !9 = !DILocation(line: 34, column: 5, scope: !4)
-// CHECK:STDOUT: !10 = !DILocation(line: 34, column: 3, scope: !4)
-// CHECK:STDOUT: !11 = !DILocation(line: 35, column: 9, scope: !4)
-// CHECK:STDOUT: !12 = !DILocation(line: 35, column: 7, scope: !4)
-// CHECK:STDOUT: !13 = !DILocation(line: 35, column: 3, scope: !4)
-// CHECK:STDOUT: !14 = !DILocation(line: 30, column: 1, scope: !4)
-// CHECK:STDOUT: !15 = distinct !DISubprogram(name: "F", linkageName: "_CF.Main.b88d1103f417c6d4", scope: null, file: !3, line: 16, type: !16, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !19)
-// CHECK:STDOUT: !16 = !DISubroutineType(types: !17)
-// CHECK:STDOUT: !17 = !{null, !18}
-// CHECK:STDOUT: !18 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
-// CHECK:STDOUT: !19 = !{!20}
-// CHECK:STDOUT: !20 = !DILocalVariable(arg: 1, scope: !15, type: !18)
-// CHECK:STDOUT: !21 = !DILocation(line: 16, column: 1, scope: !15)
-// CHECK:STDOUT: !22 = distinct !DISubprogram(name: "G", linkageName: "_CG.Main.68e44d468a50c22e", scope: null, file: !3, line: 24, type: !23, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !25)
-// CHECK:STDOUT: !23 = !DISubroutineType(types: !24)
-// CHECK:STDOUT: !24 = !{!18, !18}
-// CHECK:STDOUT: !25 = !{!26}
-// CHECK:STDOUT: !26 = !DILocalVariable(arg: 1, scope: !22, type: !18)
-// CHECK:STDOUT: !27 = !DILocation(line: 25, column: 3, scope: !22)
-// CHECK:STDOUT: !28 = !DILocation(line: 26, column: 3, scope: !22)
-// CHECK:STDOUT: !29 = !DILocation(line: 27, column: 3, scope: !22)
-// CHECK:STDOUT: !30 = distinct !DISubprogram(name: "H", linkageName: "_CH.Main.3440082c84c3c17b", scope: null, file: !3, line: 19, type: !23, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !31)
-// CHECK:STDOUT: !31 = !{!32}
-// CHECK:STDOUT: !32 = !DILocalVariable(arg: 1, scope: !30, type: !18)
-// CHECK:STDOUT: !33 = !DILocation(line: 20, column: 3, scope: !30)
-// CHECK:STDOUT: !34 = !DILocation(line: 21, column: 3, scope: !30)
+// CHECK:STDOUT: !6 = !{!7}
+// CHECK:STDOUT: !7 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+// CHECK:STDOUT: !8 = !DILocation(line: 31, column: 3, scope: !4)
+// CHECK:STDOUT: !9 = !DILocation(line: 32, column: 3, scope: !4)
+// CHECK:STDOUT: !10 = !DILocation(line: 34, column: 5, scope: !4)
+// CHECK:STDOUT: !11 = !DILocation(line: 34, column: 3, scope: !4)
+// CHECK:STDOUT: !12 = !DILocation(line: 35, column: 9, scope: !4)
+// CHECK:STDOUT: !13 = !DILocation(line: 35, column: 7, scope: !4)
+// CHECK:STDOUT: !14 = !DILocation(line: 35, column: 3, scope: !4)
+// CHECK:STDOUT: !15 = !DILocation(line: 36, column: 10, scope: !4)
+// CHECK:STDOUT: !16 = !DILocation(line: 36, column: 3, scope: !4)
+// CHECK:STDOUT: !17 = distinct !DISubprogram(name: "F", linkageName: "_CF.Main.b88d1103f417c6d4", scope: null, file: !3, line: 16, type: !18, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !20)
+// CHECK:STDOUT: !18 = !DISubroutineType(types: !19)
+// CHECK:STDOUT: !19 = !{null, !7}
+// CHECK:STDOUT: !20 = !{!21}
+// CHECK:STDOUT: !21 = !DILocalVariable(arg: 1, scope: !17, type: !7)
+// CHECK:STDOUT: !22 = !DILocation(line: 16, column: 1, scope: !17)
+// CHECK:STDOUT: !23 = distinct !DISubprogram(name: "G", linkageName: "_CG.Main.68e44d468a50c22e", scope: null, file: !3, line: 24, type: !24, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !26)
+// CHECK:STDOUT: !24 = !DISubroutineType(types: !25)
+// CHECK:STDOUT: !25 = !{!7, !7}
+// CHECK:STDOUT: !26 = !{!27}
+// CHECK:STDOUT: !27 = !DILocalVariable(arg: 1, scope: !23, type: !7)
+// CHECK:STDOUT: !28 = !DILocation(line: 25, column: 3, scope: !23)
+// CHECK:STDOUT: !29 = !DILocation(line: 26, column: 3, scope: !23)
+// CHECK:STDOUT: !30 = !DILocation(line: 27, column: 3, scope: !23)
+// CHECK:STDOUT: !31 = distinct !DISubprogram(name: "H", linkageName: "_CH.Main.3440082c84c3c17b", scope: null, file: !3, line: 19, type: !24, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !32)
+// CHECK:STDOUT: !32 = !{!33}
+// CHECK:STDOUT: !33 = !DILocalVariable(arg: 1, scope: !31, type: !7)
+// CHECK:STDOUT: !34 = !DILocation(line: 20, column: 3, scope: !31)
+// CHECK:STDOUT: !35 = !DILocation(line: 21, column: 3, scope: !31)
diff --git a/toolchain/lower/testdata/function/generic/call_different_associated_const.carbon b/toolchain/lower/testdata/function/generic/call_different_associated_const.carbon
index 671043a8754c..88279bc70471 100644
--- a/toolchain/lower/testdata/function/generic/call_different_associated_const.carbon
+++ b/toolchain/lower/testdata/function/generic/call_different_associated_const.carbon
@@ -20,7 +20,7 @@ interface I {
 }
 
 fn G(U:! I) {
-  var x: U.T*;
+  var _: U.T*;
 }
 
 class C {}
@@ -51,8 +51,8 @@ fn H() {
 // CHECK:STDOUT: ; Function Attrs: nounwind
 // CHECK:STDOUT: define linkonce_odr void @_CG.Main.105e251602f0e987() #0 !dbg !10 {
 // CHECK:STDOUT: entry:
-// CHECK:STDOUT:   %x.var = alloca ptr, align 8, !dbg !11
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %x.var), !dbg !11
+// CHECK:STDOUT:   %_.var = alloca ptr, align 8, !dbg !11
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var), !dbg !11
 // CHECK:STDOUT:   ret void, !dbg !12
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
diff --git a/toolchain/lower/testdata/function/generic/call_different_impls_with_const.carbon b/toolchain/lower/testdata/function/generic/call_different_impls_with_const.carbon
index fd2ebdf63ee6..f8e39ddfd926 100644
--- a/toolchain/lower/testdata/function/generic/call_different_impls_with_const.carbon
+++ b/toolchain/lower/testdata/function/generic/call_different_impls_with_const.carbon
@@ -34,7 +34,7 @@ impl Y as I where .T = i32 {
 // Cannot coalesce the lowering for G specifics, as they call different functions.
 // Check different functions are still emitted when trying to deduplicate emitted definitons.
 fn G(U:! I) {
-  let x: U.T = U.F();
+  let _: U.T = U.F();
 }
 
 fn Run() {
diff --git a/toolchain/lower/testdata/function/generic/call_specific_in_class.carbon b/toolchain/lower/testdata/function/generic/call_specific_in_class.carbon
index a5499307d4f4..95975def08cf 100644
--- a/toolchain/lower/testdata/function/generic/call_specific_in_class.carbon
+++ b/toolchain/lower/testdata/function/generic/call_specific_in_class.carbon
@@ -40,7 +40,7 @@ fn M() {
   F(var_i32);
   var var_f64: f64 = 0.0;
   F(var_f64);
-  var c: C;
+  var _: C;
   F(C);
 }
 
@@ -57,7 +57,7 @@ fn M() {
 // CHECK:STDOUT:   %ptr_i8.var = alloca ptr, align 8, !dbg !9
 // CHECK:STDOUT:   %var_i32.var = alloca i32, align 4, !dbg !10
 // CHECK:STDOUT:   %var_f64.var = alloca double, align 8, !dbg !11
-// CHECK:STDOUT:   %c.var = alloca {}, align 8, !dbg !12
+// CHECK:STDOUT:   %_.var = alloca {}, align 8, !dbg !12
 // CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %ptr_i32.var), !dbg !7
 // CHECK:STDOUT:   %.loc34_5 = load ptr, ptr %ptr_i32.var, align 8, !dbg !13
 // CHECK:STDOUT:   %F.call.loc34 = call ptr @_CF.Main.4b30cda44e16b9ec(ptr %.loc34_5), !dbg !14
@@ -75,7 +75,7 @@ fn M() {
 // CHECK:STDOUT:   store double 0.000000e+00, ptr %var_f64.var, align 8, !dbg !11
 // CHECK:STDOUT:   %.loc42_5 = load double, ptr %var_f64.var, align 8, !dbg !21
 // CHECK:STDOUT:   %F.call.loc42 = call double @_CF.Main.286b0f7890e5304c(double %.loc42_5), !dbg !22
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %c.var), !dbg !12
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var), !dbg !12
 // CHECK:STDOUT:   %F.call.loc44 = call %type @_CF.Main.93e33f284107e304(%type zeroinitializer), !dbg !23
 // CHECK:STDOUT:   ret void, !dbg !24
 // CHECK:STDOUT: }
diff --git a/toolchain/lower/testdata/function/generic/cross_library_name_collision_private.carbon b/toolchain/lower/testdata/function/generic/cross_library_name_collision_private.carbon
index 079beeefff6d..0af263b73106 100644
--- a/toolchain/lower/testdata/function/generic/cross_library_name_collision_private.carbon
+++ b/toolchain/lower/testdata/function/generic/cross_library_name_collision_private.carbon
@@ -14,7 +14,7 @@
 
 library "[[@TEST_NAME]]";
 
-private fn F[T:! Core.Copy](a: T, b: T) -> T {
+private fn F[T:! Core.Copy](a: T, _: T) -> T {
   return a;
 }
 
@@ -29,7 +29,7 @@ library "[[@TEST_NAME]]";
 // Duplicate function name in different files. Shouldn't be a name conflict
 // because of `private`. However, we currently use the same mangling for both
 // functions.
-private fn F[T:! Core.Copy](a: T, b: T) -> T {
+private fn F[T:! Core.Copy](_: T, b: T) -> T {
   return b;
 }
 
@@ -47,8 +47,8 @@ import library "lib1";
 import library "lib2";
 
 fn Run() {
-  let a: i32 = Lib1CallF(1 as i32, 2 as i32);
-  let b: i32 = Lib2CallF(1 as i32, 2 as i32);
+  let _: i32 = Lib1CallF(1 as i32, 2 as i32);
+  let _: i32 = Lib2CallF(1 as i32, 2 as i32);
 }
 
 // CHECK:STDOUT: ; ModuleID = 'lib1.carbon'
@@ -95,7 +95,7 @@ fn Run() {
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
-// CHECK:STDOUT: define linkonce_odr i32 @_CF.Main.d7c78c5f84c57c86(i32 %a, i32 %b) #0 !dbg !27 {
+// CHECK:STDOUT: define linkonce_odr i32 @_CF.Main.d7c78c5f84c57c86(i32 %a, i32 %_) #0 !dbg !27 {
 // CHECK:STDOUT:   ret i32 %a, !dbg !31
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
diff --git a/toolchain/lower/testdata/function/generic/type_param.carbon b/toolchain/lower/testdata/function/generic/type_param.carbon
index 96a27dfa51c9..79c0e2c41967 100644
--- a/toolchain/lower/testdata/function/generic/type_param.carbon
+++ b/toolchain/lower/testdata/function/generic/type_param.carbon
@@ -12,7 +12,7 @@
 
 fn F(T:! type) {
   var p: T*;
-  let n: T = *p;
+  let _: T = *p;
 }
 
 // CHECK:STDOUT: ; ModuleID = 'type_param.carbon'
diff --git a/toolchain/lower/testdata/function/generic/type_representation.carbon b/toolchain/lower/testdata/function/generic/type_representation.carbon
index c7d4996a6288..1e175af1cfbe 100644
--- a/toolchain/lower/testdata/function/generic/type_representation.carbon
+++ b/toolchain/lower/testdata/function/generic/type_representation.carbon
@@ -15,7 +15,7 @@ interface Copy {
 }
 
 fn F[T:! Copy & Core.Destroy](a: T) -> T {
-  var v: T = a.(Copy.Op)();
+  var _: T = a.(Copy.Op)();
   return a.(Copy.Op)();
 }
 
@@ -169,10 +169,10 @@ fn F_nested_tuple(a: ((i32, i32), X)) -> ((i32, i32), X) {
 // CHECK:STDOUT: ; Function Attrs: nounwind
 // CHECK:STDOUT: define linkonce_odr i32 @_CF.Main.4301ec5c5ecd651f(i32 %a) #0 !dbg !60 {
 // CHECK:STDOUT: entry:
-// CHECK:STDOUT:   %v.var = alloca i32, align 4, !dbg !63
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %v.var), !dbg !63
+// CHECK:STDOUT:   %_.var = alloca i32, align 4, !dbg !63
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var), !dbg !63
 // CHECK:STDOUT:   %Copy.Op.call.loc18 = call i32 @"_COp.Int.Core:Copy.Main"(i32 %a), !dbg !64
-// CHECK:STDOUT:   store i32 %Copy.Op.call.loc18, ptr %v.var, align 4, !dbg !63
+// CHECK:STDOUT:   store i32 %Copy.Op.call.loc18, ptr %_.var, align 4, !dbg !63
 // CHECK:STDOUT:   %Copy.Op.call.loc19 = call i32 @"_COp.Int.Core:Copy.Main"(i32 %a), !dbg !65
 // CHECK:STDOUT:   ret i32 %Copy.Op.call.loc19, !dbg !66
 // CHECK:STDOUT: }
@@ -180,9 +180,9 @@ fn F_nested_tuple(a: ((i32, i32), X)) -> ((i32, i32), X) {
 // CHECK:STDOUT: ; Function Attrs: nounwind
 // CHECK:STDOUT: define linkonce_odr void @_CF.Main.8bb618905c12e223(ptr sret({ i32, i32 }) %return, ptr %a) #0 !dbg !67 {
 // CHECK:STDOUT: entry:
-// CHECK:STDOUT:   %v.var = alloca { i32, i32 }, align 8, !dbg !70
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %v.var), !dbg !70
-// CHECK:STDOUT:   call void @"_COp.X.Main:Copy.Main"(ptr %v.var, ptr %a), !dbg !71
+// CHECK:STDOUT:   %_.var = alloca { i32, i32 }, align 8, !dbg !70
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var), !dbg !70
+// CHECK:STDOUT:   call void @"_COp.X.Main:Copy.Main"(ptr %_.var, ptr %a), !dbg !71
 // CHECK:STDOUT:   call void @"_COp.X.Main:Copy.Main"(ptr %return, ptr %a), !dbg !72
 // CHECK:STDOUT:   ret void, !dbg !73
 // CHECK:STDOUT: }
@@ -190,8 +190,8 @@ fn F_nested_tuple(a: ((i32, i32), X)) -> ((i32, i32), X) {
 // CHECK:STDOUT: ; Function Attrs: nounwind
 // CHECK:STDOUT: define linkonce_odr void @_CF.Main.92c61b43c9f740f5() #0 !dbg !74 {
 // CHECK:STDOUT: entry:
-// CHECK:STDOUT:   %v.var = alloca {}, align 8, !dbg !75
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %v.var), !dbg !75
+// CHECK:STDOUT:   %_.var = alloca {}, align 8, !dbg !75
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var), !dbg !75
 // CHECK:STDOUT:   call void @"_COp.61ea2aba74ab3bf1:Copy.Main"(), !dbg !76
 // CHECK:STDOUT:   call void @"_COp.61ea2aba74ab3bf1:Copy.Main"(), !dbg !77
 // CHECK:STDOUT:   ret void, !dbg !78
@@ -200,9 +200,9 @@ fn F_nested_tuple(a: ((i32, i32), X)) -> ((i32, i32), X) {
 // CHECK:STDOUT: ; Function Attrs: nounwind
 // CHECK:STDOUT: define linkonce_odr void @_CF.Main.444df219ccd81c52(ptr sret({ i32, i32 }) %return, ptr %a) #0 !dbg !79 {
 // CHECK:STDOUT: entry:
-// CHECK:STDOUT:   %v.var = alloca { i32, i32 }, align 8, !dbg !82
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %v.var), !dbg !82
-// CHECK:STDOUT:   call void @"_COp.d07e2731f1087d49:Copy.Main"(ptr %v.var, ptr %a), !dbg !83
+// CHECK:STDOUT:   %_.var = alloca { i32, i32 }, align 8, !dbg !82
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var), !dbg !82
+// CHECK:STDOUT:   call void @"_COp.d07e2731f1087d49:Copy.Main"(ptr %_.var, ptr %a), !dbg !83
 // CHECK:STDOUT:   call void @"_COp.d07e2731f1087d49:Copy.Main"(ptr %return, ptr %a), !dbg !84
 // CHECK:STDOUT:   ret void, !dbg !85
 // CHECK:STDOUT: }
@@ -210,9 +210,9 @@ fn F_nested_tuple(a: ((i32, i32), X)) -> ((i32, i32), X) {
 // CHECK:STDOUT: ; Function Attrs: nounwind
 // CHECK:STDOUT: define linkonce_odr void @_CF.Main.ce36b8714ed574a4(ptr sret({ { i32, i32 }, { i32, i32 } }) %return, ptr %a) #0 !dbg !86 {
 // CHECK:STDOUT: entry:
-// CHECK:STDOUT:   %v.var = alloca { { i32, i32 }, { i32, i32 } }, align 8, !dbg !89
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %v.var), !dbg !89
-// CHECK:STDOUT:   call void @"_COp.a6c7c55658a5a74c:Copy.Main"(ptr %v.var, ptr %a), !dbg !90
+// CHECK:STDOUT:   %_.var = alloca { { i32, i32 }, { i32, i32 } }, align 8, !dbg !89
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var), !dbg !89
+// CHECK:STDOUT:   call void @"_COp.a6c7c55658a5a74c:Copy.Main"(ptr %_.var, ptr %a), !dbg !90
 // CHECK:STDOUT:   call void @"_COp.a6c7c55658a5a74c:Copy.Main"(ptr %return, ptr %a), !dbg !91
 // CHECK:STDOUT:   ret void, !dbg !92
 // CHECK:STDOUT: }
diff --git a/toolchain/lower/testdata/impl/thunk.carbon b/toolchain/lower/testdata/impl/thunk.carbon
index ccc203fe736c..3ee9a430be22 100644
--- a/toolchain/lower/testdata/impl/thunk.carbon
+++ b/toolchain/lower/testdata/impl/thunk.carbon
@@ -55,7 +55,7 @@ interface I(T:! type) {
 class C(U:! type) {}
 
 impl forall [V:! type] C(V) as I(V) {
-  fn F[self: Self](x: A) -> B { return {}; }
+  fn F[self: Self](_: A) -> B { return {}; }
 }
 
 fn Call(c: C(()), b: B) -> A {
@@ -225,7 +225,7 @@ fn CallCallGeneric(c: C(()), b: B) -> A {
 // CHECK:STDOUT: declare void @llvm.lifetime.start.p0(ptr captures(none)) #2
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
-// CHECK:STDOUT: define linkonce_odr void @"_CF.C.Main:I.Main.e43630e9a6c38c3f"(ptr sret({}) %return, ptr %self, ptr %x) #0 !dbg !26 {
+// CHECK:STDOUT: define linkonce_odr void @"_CF.C.Main:I.Main.e43630e9a6c38c3f"(ptr sret({}) %return, ptr %self, ptr %_) #0 !dbg !26 {
 // CHECK:STDOUT: entry:
 // CHECK:STDOUT:   call void @llvm.memcpy.p0.p0.i64(ptr align 1 %return, ptr align 1 @B.val.loc18_42, i64 0, i1 false), !dbg !30
 // CHECK:STDOUT:   ret void, !dbg !30
diff --git a/toolchain/lower/testdata/index/array_element_access.carbon b/toolchain/lower/testdata/index/array_element_access.carbon
index a395bf0d81b0..08a5ff5aacb9 100644
--- a/toolchain/lower/testdata/index/array_element_access.carbon
+++ b/toolchain/lower/testdata/index/array_element_access.carbon
@@ -16,8 +16,8 @@ fn B() -> array(i32, 2) { return (1, 2); }
 fn Run() {
   var a: array(i32, 2) = A();
   var b: i32 = 1;
-  var c: i32 = a[b];
-  var d: i32 = B()[1];
+  var _: i32 = a[b];
+  var _: i32 = B()[1];
 }
 
 // CHECK:STDOUT: ; ModuleID = 'array_element_access.carbon'
@@ -50,8 +50,8 @@ fn Run() {
 // CHECK:STDOUT:   %a.var = alloca [2 x i32], align 4, !dbg !16
 // CHECK:STDOUT:   %.loc17_28.1.temp = alloca { i32, i32 }, align 8, !dbg !17
 // CHECK:STDOUT:   %b.var = alloca i32, align 4, !dbg !18
-// CHECK:STDOUT:   %c.var = alloca i32, align 4, !dbg !19
-// CHECK:STDOUT:   %d.var = alloca i32, align 4, !dbg !20
+// CHECK:STDOUT:   %_.var.loc19 = alloca i32, align 4, !dbg !19
+// CHECK:STDOUT:   %_.var.loc20 = alloca i32, align 4, !dbg !20
 // CHECK:STDOUT:   %.loc20_18.1.temp = alloca [2 x i32], align 4, !dbg !21
 // CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %a.var), !dbg !16
 // CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %.loc17_28.1.temp), !dbg !17
@@ -66,17 +66,17 @@ fn Run() {
 // CHECK:STDOUT:   store i32 %.loc17_28.6, ptr %.loc17_28.7.array.index, align 4, !dbg !17
 // CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %b.var), !dbg !18
 // CHECK:STDOUT:   store i32 1, ptr %b.var, align 4, !dbg !18
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %c.var), !dbg !19
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var.loc19), !dbg !19
 // CHECK:STDOUT:   %.loc19_18 = load i32, ptr %b.var, align 4, !dbg !22
 // CHECK:STDOUT:   %.loc19_19.1.array.index = getelementptr inbounds [2 x i32], ptr %a.var, i32 0, i32 %.loc19_18, !dbg !23
 // CHECK:STDOUT:   %.loc19_19.2 = load i32, ptr %.loc19_19.1.array.index, align 4, !dbg !23
-// CHECK:STDOUT:   store i32 %.loc19_19.2, ptr %c.var, align 4, !dbg !19
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %d.var), !dbg !20
+// CHECK:STDOUT:   store i32 %.loc19_19.2, ptr %_.var.loc19, align 4, !dbg !19
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var.loc20), !dbg !20
 // CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %.loc20_18.1.temp), !dbg !21
 // CHECK:STDOUT:   call void @_CB.Main(ptr %.loc20_18.1.temp), !dbg !21
 // CHECK:STDOUT:   %.loc20_21.1.array.index = getelementptr inbounds [2 x i32], ptr %.loc20_18.1.temp, i32 0, i32 1, !dbg !21
 // CHECK:STDOUT:   %.loc20_21.2 = load i32, ptr %.loc20_21.1.array.index, align 4, !dbg !21
-// CHECK:STDOUT:   store i32 %.loc20_21.2, ptr %d.var, align 4, !dbg !20
+// CHECK:STDOUT:   store i32 %.loc20_21.2, ptr %_.var.loc20, align 4, !dbg !20
 // CHECK:STDOUT:   ret void, !dbg !24
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
diff --git a/toolchain/lower/testdata/interface/basic.carbon b/toolchain/lower/testdata/interface/basic.carbon
index 69a3699a9969..0407869ad6f5 100644
--- a/toolchain/lower/testdata/interface/basic.carbon
+++ b/toolchain/lower/testdata/interface/basic.carbon
@@ -16,7 +16,7 @@ interface I {
 
 // There are no interesting runtime operations here, but there's no rule saying
 // you can't pass a facet around at runtime, so make sure it works.
-fn F(T: I) {}
+fn F(_: I) {}
 
 fn G() -> I;
 
@@ -26,7 +26,7 @@ fn H() -> I { return G(); }
 // CHECK:STDOUT: source_filename = "basic.carbon"
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
-// CHECK:STDOUT: define void @_CF.Main({} %T) #0 !dbg !4 {
+// CHECK:STDOUT: define void @_CF.Main({} %_) #0 !dbg !4 {
 // CHECK:STDOUT: entry:
 // CHECK:STDOUT:   ret void, !dbg !10
 // CHECK:STDOUT: }
diff --git a/toolchain/lower/testdata/interop/cpp/constructor.carbon b/toolchain/lower/testdata/interop/cpp/constructor.carbon
index 178c416df3d0..e29037f715a0 100644
--- a/toolchain/lower/testdata/interop/cpp/constructor.carbon
+++ b/toolchain/lower/testdata/interop/cpp/constructor.carbon
@@ -32,7 +32,7 @@ library "[[@TEST_NAME]]";
 import Cpp library "default.h";
 
 fn F() {
-  let c: Cpp.C = Cpp.C.C();
+  let _: Cpp.C = Cpp.C.C();
 }
 
 // ============================================================================
diff --git a/toolchain/lower/testdata/interop/cpp/function_decl.carbon b/toolchain/lower/testdata/interop/cpp/function_decl.carbon
index 965399a5b5f8..aef1f6b14add 100644
--- a/toolchain/lower/testdata/interop/cpp/function_decl.carbon
+++ b/toolchain/lower/testdata/interop/cpp/function_decl.carbon
@@ -121,7 +121,7 @@ library "[[@TEST_NAME]]";
 
 import Cpp library "with_default_args.h";
 
-fn MyF() {
+fn MyF() -> i32 {
   Cpp.NoReturnValue();
   Cpp.NoReturnValue(3);
   Cpp.NoReturnValue(3, 4);
@@ -129,6 +129,7 @@ fn MyF() {
   var value: i32 = Cpp.SimpleReturnValue();
   value = Cpp.SimpleReturnValue(3);
   value = Cpp.SimpleReturnValue(3, 4);
+  return value;
 }
 
 // CHECK:STDOUT: ; ModuleID = 'import_function_decl.carbon'
@@ -355,20 +356,21 @@ fn MyF() {
 // CHECK:STDOUT: target triple = "x86_64-unknown-linux-gnu"
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
-// CHECK:STDOUT: define void @_CMyF.Main() #0 !dbg !7 {
+// CHECK:STDOUT: define i32 @_CMyF.Main() #0 !dbg !7 {
 // CHECK:STDOUT: entry:
-// CHECK:STDOUT:   %value.var = alloca i32, align 4, !dbg !10
-// CHECK:STDOUT:   call void @_Z13NoReturnValueii.carbon_thunk0(), !dbg !11
-// CHECK:STDOUT:   call void @_Z13NoReturnValueii.carbon_thunk1(i32 3), !dbg !12
-// CHECK:STDOUT:   call void @_Z13NoReturnValueii(i32 3, i32 4), !dbg !13
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %value.var), !dbg !10
-// CHECK:STDOUT:   %SimpleReturnValue__carbon_thunk.call.loc11 = call i32 @_Z17SimpleReturnValueii.carbon_thunk0(), !dbg !14
-// CHECK:STDOUT:   store i32 %SimpleReturnValue__carbon_thunk.call.loc11, ptr %value.var, align 4, !dbg !10
-// CHECK:STDOUT:   %SimpleReturnValue__carbon_thunk.call.loc12 = call i32 @_Z17SimpleReturnValueii.carbon_thunk1(i32 3), !dbg !15
-// CHECK:STDOUT:   store i32 %SimpleReturnValue__carbon_thunk.call.loc12, ptr %value.var, align 4, !dbg !16
-// CHECK:STDOUT:   %SimpleReturnValue.call = call i32 @_Z17SimpleReturnValueii(i32 3, i32 4), !dbg !17
-// CHECK:STDOUT:   store i32 %SimpleReturnValue.call, ptr %value.var, align 4, !dbg !18
-// CHECK:STDOUT:   ret void, !dbg !19
+// CHECK:STDOUT:   %value.var = alloca i32, align 4, !dbg !11
+// CHECK:STDOUT:   call void @_Z13NoReturnValueii.carbon_thunk0(), !dbg !12
+// CHECK:STDOUT:   call void @_Z13NoReturnValueii.carbon_thunk1(i32 3), !dbg !13
+// CHECK:STDOUT:   call void @_Z13NoReturnValueii(i32 3, i32 4), !dbg !14
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %value.var), !dbg !11
+// CHECK:STDOUT:   %SimpleReturnValue__carbon_thunk.call.loc11 = call i32 @_Z17SimpleReturnValueii.carbon_thunk0(), !dbg !15
+// CHECK:STDOUT:   store i32 %SimpleReturnValue__carbon_thunk.call.loc11, ptr %value.var, align 4, !dbg !11
+// CHECK:STDOUT:   %SimpleReturnValue__carbon_thunk.call.loc12 = call i32 @_Z17SimpleReturnValueii.carbon_thunk1(i32 3), !dbg !16
+// CHECK:STDOUT:   store i32 %SimpleReturnValue__carbon_thunk.call.loc12, ptr %value.var, align 4, !dbg !17
+// CHECK:STDOUT:   %SimpleReturnValue.call = call i32 @_Z17SimpleReturnValueii(i32 3, i32 4), !dbg !18
+// CHECK:STDOUT:   store i32 %SimpleReturnValue.call, ptr %value.var, align 4, !dbg !19
+// CHECK:STDOUT:   %.loc14 = load i32, ptr %value.var, align 4, !dbg !20
+// CHECK:STDOUT:   ret i32 %.loc14, !dbg !21
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: declare void @_Z13NoReturnValueii(i32, i32)
@@ -428,14 +430,16 @@ fn MyF() {
 // CHECK:STDOUT: !6 = !DIFile(filename: "call_with_default_args.carbon", directory: "")
 // CHECK:STDOUT: !7 = distinct !DISubprogram(name: "MyF", linkageName: "_CMyF.Main", scope: null, file: !6, line: 6, type: !8, spFlags: DISPFlagDefinition, unit: !5)
 // CHECK:STDOUT: !8 = !DISubroutineType(types: !9)
-// CHECK:STDOUT: !9 = !{null}
-// CHECK:STDOUT: !10 = !DILocation(line: 11, column: 3, scope: !7)
-// CHECK:STDOUT: !11 = !DILocation(line: 7, column: 3, scope: !7)
-// CHECK:STDOUT: !12 = !DILocation(line: 8, column: 3, scope: !7)
-// CHECK:STDOUT: !13 = !DILocation(line: 9, column: 3, scope: !7)
-// CHECK:STDOUT: !14 = !DILocation(line: 11, column: 20, scope: !7)
-// CHECK:STDOUT: !15 = !DILocation(line: 12, column: 11, scope: !7)
-// CHECK:STDOUT: !16 = !DILocation(line: 12, column: 3, scope: !7)
-// CHECK:STDOUT: !17 = !DILocation(line: 13, column: 11, scope: !7)
-// CHECK:STDOUT: !18 = !DILocation(line: 13, column: 3, scope: !7)
-// CHECK:STDOUT: !19 = !DILocation(line: 6, column: 1, scope: !7)
+// CHECK:STDOUT: !9 = !{!10}
+// CHECK:STDOUT: !10 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+// CHECK:STDOUT: !11 = !DILocation(line: 11, column: 3, scope: !7)
+// CHECK:STDOUT: !12 = !DILocation(line: 7, column: 3, scope: !7)
+// CHECK:STDOUT: !13 = !DILocation(line: 8, column: 3, scope: !7)
+// CHECK:STDOUT: !14 = !DILocation(line: 9, column: 3, scope: !7)
+// CHECK:STDOUT: !15 = !DILocation(line: 11, column: 20, scope: !7)
+// CHECK:STDOUT: !16 = !DILocation(line: 12, column: 11, scope: !7)
+// CHECK:STDOUT: !17 = !DILocation(line: 12, column: 3, scope: !7)
+// CHECK:STDOUT: !18 = !DILocation(line: 13, column: 11, scope: !7)
+// CHECK:STDOUT: !19 = !DILocation(line: 13, column: 3, scope: !7)
+// CHECK:STDOUT: !20 = !DILocation(line: 14, column: 10, scope: !7)
+// CHECK:STDOUT: !21 = !DILocation(line: 14, column: 3, scope: !7)
diff --git a/toolchain/lower/testdata/interop/cpp/globals.carbon b/toolchain/lower/testdata/interop/cpp/globals.carbon
index 6adc14936b9b..043d32b8ddbc 100644
--- a/toolchain/lower/testdata/interop/cpp/globals.carbon
+++ b/toolchain/lower/testdata/interop/cpp/globals.carbon
@@ -26,7 +26,7 @@ library "[[@TEST_NAME]]";
 import Cpp library "global.h";
 
 fn MyF() {
-  let local: Cpp.C = Cpp.global;
+  let _: Cpp.C = Cpp.global;
 }
 
 // CHECK:STDOUT: ; ModuleID = 'import_global.carbon'
diff --git a/toolchain/lower/testdata/interop/cpp/pointer.carbon b/toolchain/lower/testdata/interop/cpp/pointer.carbon
index 20306bc5b8de..b1fd7166ccbc 100644
--- a/toolchain/lower/testdata/interop/cpp/pointer.carbon
+++ b/toolchain/lower/testdata/interop/cpp/pointer.carbon
@@ -62,7 +62,7 @@ auto TakePtrWithThunk(C*, int = 0) -> void;
 auto ReturnPtrWithThunk(int = 0) -> C*;
 ''';
 
-fn PassPtr(p: Core.Optional(Cpp.C*)) {
+fn PassPtr(_: Core.Optional(Cpp.C*)) {
   // TODO: Add support for passing an optional here.
   // Cpp.TakePtr(p);
 }
@@ -77,7 +77,7 @@ fn ReturnPtr() -> Core.Optional(Cpp.C*) {
   return Cpp.ReturnPtr();
 }
 
-fn PassPtrWithThunk(p: Core.Optional(Cpp.C*)) {
+fn PassPtrWithThunk(_: Core.Optional(Cpp.C*)) {
   // TODO: Add support for passing an optional here.
   // Cpp.TakePtrWithThunk(p);
 }
@@ -189,7 +189,7 @@ fn ReturnPtrWithThunk() -> Core.Optional(Cpp.C*) {
 // CHECK:STDOUT: target triple = "x86_64-unknown-linux-gnu"
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
-// CHECK:STDOUT: define void @_CPassPtr.Main(ptr %p) #0 !dbg !7 {
+// CHECK:STDOUT: define void @_CPassPtr.Main(ptr %_) #0 !dbg !7 {
 // CHECK:STDOUT: entry:
 // CHECK:STDOUT:   ret void, !dbg !13
 // CHECK:STDOUT: }
@@ -218,7 +218,7 @@ fn ReturnPtrWithThunk() -> Core.Optional(Cpp.C*) {
 // CHECK:STDOUT: declare ptr @_Z9ReturnPtrv()
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
-// CHECK:STDOUT: define void @_CPassPtrWithThunk.Main(ptr %p) #0 !dbg !25 {
+// CHECK:STDOUT: define void @_CPassPtrWithThunk.Main(ptr %_) #0 !dbg !25 {
 // CHECK:STDOUT: entry:
 // CHECK:STDOUT:   ret void, !dbg !28
 // CHECK:STDOUT: }
diff --git a/toolchain/lower/testdata/interop/cpp/reference.carbon b/toolchain/lower/testdata/interop/cpp/reference.carbon
index 8914006d8675..ba2c760327cb 100644
--- a/toolchain/lower/testdata/interop/cpp/reference.carbon
+++ b/toolchain/lower/testdata/interop/cpp/reference.carbon
@@ -92,13 +92,13 @@ 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 _: Cpp.C* = Cpp.ReturnCRef();
+  var _: Cpp.C* = Cpp.ReturnCRRef();
+  var _: const Cpp.C* = Cpp.ReturnConstCRef();
 
-  var n1: i32* = Cpp.ReturnIntRef();
-  var n2: i32* = Cpp.ReturnIntRRef();
-  var n3: const i32* = Cpp.ReturnConstIntRef();
+  var _: i32* = Cpp.ReturnIntRef();
+  var _: i32* = Cpp.ReturnIntRRef();
+  var _: const i32* = Cpp.ReturnConstIntRef();
 }
 
 // --- return_references_via_thunk.carbon
@@ -119,13 +119,13 @@ auto ReturnConstIntRef(ForceThunk = {}) -> const int&;
 ''';
 
 fn GetRefs() {
-  var c1: Cpp.C* = Cpp.ReturnCRef();
-  var c2: Cpp.C* = Cpp.ReturnCRRef();
-  var c3: const Cpp.C* = Cpp.ReturnConstCRef();
+  var _: Cpp.C* = Cpp.ReturnCRef();
+  var _: Cpp.C* = Cpp.ReturnCRRef();
+  var _: const Cpp.C* = Cpp.ReturnConstCRef();
 
-  var n1: i32* = Cpp.ReturnIntRef();
-  var n2: i32* = Cpp.ReturnIntRRef();
-  var n3: const i32* = Cpp.ReturnConstIntRef();
+  var _: i32* = Cpp.ReturnIntRef();
+  var _: i32* = Cpp.ReturnIntRRef();
+  var _: const i32* = Cpp.ReturnConstIntRef();
 }
 
 // CHECK:STDOUT: ; ModuleID = 'pass_references.carbon'
@@ -426,30 +426,30 @@ fn GetRefs() {
 // CHECK:STDOUT: ; Function Attrs: nounwind
 // CHECK:STDOUT: define void @_CGetRefs.Main() #0 !dbg !7 {
 // CHECK:STDOUT: entry:
-// CHECK:STDOUT:   %c1.var = alloca ptr, align 8, !dbg !10
-// CHECK:STDOUT:   %c2.var = alloca ptr, 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 ptr, align 8, !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:   %_.var.loc17 = alloca ptr, align 8, !dbg !10
+// CHECK:STDOUT:   %_.var.loc18 = alloca ptr, align 8, !dbg !11
+// CHECK:STDOUT:   %_.var.loc19 = alloca ptr, align 8, !dbg !12
+// CHECK:STDOUT:   %_.var.loc21 = alloca ptr, align 8, !dbg !13
+// CHECK:STDOUT:   %_.var.loc22 = alloca ptr, align 8, !dbg !14
+// CHECK:STDOUT:   %_.var.loc23 = alloca ptr, align 8, !dbg !15
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var.loc17), !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:   store ptr %ReturnCRef.call, ptr %_.var.loc17, align 8, !dbg !10
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var.loc18), !dbg !11
 // CHECK:STDOUT:   %ReturnCRRef.call = call ptr @_Z11ReturnCRRefv(), !dbg !17
-// CHECK:STDOUT:   store ptr %ReturnCRRef.call, ptr %c2.var, align 8, !dbg !11
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %c3.var), !dbg !12
+// CHECK:STDOUT:   store ptr %ReturnCRRef.call, ptr %_.var.loc18, align 8, !dbg !11
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var.loc19), !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:   store ptr %ReturnConstCRef.call, ptr %_.var.loc19, align 8, !dbg !12
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var.loc21), !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:   store ptr %ReturnIntRef.call, ptr %_.var.loc21, align 8, !dbg !13
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var.loc22), !dbg !14
 // CHECK:STDOUT:   %ReturnIntRRef.call = call ptr @_Z13ReturnIntRRefv(), !dbg !20
-// CHECK:STDOUT:   store ptr %ReturnIntRRef.call, ptr %n2.var, align 8, !dbg !14
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %n3.var), !dbg !15
+// CHECK:STDOUT:   store ptr %ReturnIntRRef.call, ptr %_.var.loc22, align 8, !dbg !14
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var.loc23), !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:   store ptr %ReturnConstIntRef.call, ptr %_.var.loc23, align 8, !dbg !15
 // CHECK:STDOUT:   ret void, !dbg !22
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
@@ -493,12 +493,12 @@ fn GetRefs() {
 // 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: 20, 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: 18, scope: !7)
-// CHECK:STDOUT: !21 = !DILocation(line: 23, column: 24, scope: !7)
+// CHECK:STDOUT: !16 = !DILocation(line: 17, column: 19, scope: !7)
+// CHECK:STDOUT: !17 = !DILocation(line: 18, column: 19, scope: !7)
+// CHECK:STDOUT: !18 = !DILocation(line: 19, column: 25, scope: !7)
+// CHECK:STDOUT: !19 = !DILocation(line: 21, column: 17, scope: !7)
+// CHECK:STDOUT: !20 = !DILocation(line: 22, column: 17, scope: !7)
+// CHECK:STDOUT: !21 = !DILocation(line: 23, column: 23, scope: !7)
 // CHECK:STDOUT: !22 = !DILocation(line: 16, column: 1, scope: !7)
 // CHECK:STDOUT: ; ModuleID = 'return_references_via_thunk.carbon'
 // CHECK:STDOUT: source_filename = "return_references_via_thunk.carbon"
@@ -510,30 +510,30 @@ fn GetRefs() {
 // CHECK:STDOUT: ; Function Attrs: nounwind
 // CHECK:STDOUT: define void @_CGetRefs.Main() #0 !dbg !7 {
 // CHECK:STDOUT: entry:
-// CHECK:STDOUT:   %c1.var = alloca ptr, align 8, !dbg !10
-// CHECK:STDOUT:   %c2.var = alloca ptr, 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 ptr, align 8, !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:   %_.var.loc18 = alloca ptr, align 8, !dbg !10
+// CHECK:STDOUT:   %_.var.loc19 = alloca ptr, align 8, !dbg !11
+// CHECK:STDOUT:   %_.var.loc20 = alloca ptr, align 8, !dbg !12
+// CHECK:STDOUT:   %_.var.loc22 = alloca ptr, align 8, !dbg !13
+// CHECK:STDOUT:   %_.var.loc23 = alloca ptr, align 8, !dbg !14
+// CHECK:STDOUT:   %_.var.loc24 = alloca ptr, align 8, !dbg !15
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var.loc18), !dbg !10
 // CHECK:STDOUT:   %ReturnCRef__carbon_thunk.call = call ptr @_Z10ReturnCRef10ForceThunk.carbon_thunk0(), !dbg !16
-// CHECK:STDOUT:   store ptr %ReturnCRef__carbon_thunk.call, ptr %c1.var, align 8, !dbg !10
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %c2.var), !dbg !11
+// CHECK:STDOUT:   store ptr %ReturnCRef__carbon_thunk.call, ptr %_.var.loc18, align 8, !dbg !10
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var.loc19), !dbg !11
 // CHECK:STDOUT:   %ReturnCRRef__carbon_thunk.call = call ptr @_Z11ReturnCRRef10ForceThunk.carbon_thunk0(), !dbg !17
-// CHECK:STDOUT:   store ptr %ReturnCRRef__carbon_thunk.call, ptr %c2.var, align 8, !dbg !11
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %c3.var), !dbg !12
+// CHECK:STDOUT:   store ptr %ReturnCRRef__carbon_thunk.call, ptr %_.var.loc19, align 8, !dbg !11
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var.loc20), !dbg !12
 // CHECK:STDOUT:   %ReturnConstCRef__carbon_thunk.call = call ptr @_Z15ReturnConstCRef10ForceThunk.carbon_thunk0(), !dbg !18
-// CHECK:STDOUT:   store ptr %ReturnConstCRef__carbon_thunk.call, ptr %c3.var, align 8, !dbg !12
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %n1.var), !dbg !13
+// CHECK:STDOUT:   store ptr %ReturnConstCRef__carbon_thunk.call, ptr %_.var.loc20, align 8, !dbg !12
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var.loc22), !dbg !13
 // CHECK:STDOUT:   %ReturnIntRef__carbon_thunk.call = call ptr @_Z12ReturnIntRef10ForceThunk.carbon_thunk0(), !dbg !19
-// CHECK:STDOUT:   store ptr %ReturnIntRef__carbon_thunk.call, ptr %n1.var, align 8, !dbg !13
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %n2.var), !dbg !14
+// CHECK:STDOUT:   store ptr %ReturnIntRef__carbon_thunk.call, ptr %_.var.loc22, align 8, !dbg !13
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var.loc23), !dbg !14
 // CHECK:STDOUT:   %ReturnIntRRef__carbon_thunk.call = call ptr @_Z13ReturnIntRRef10ForceThunk.carbon_thunk0(), !dbg !20
-// CHECK:STDOUT:   store ptr %ReturnIntRRef__carbon_thunk.call, ptr %n2.var, align 8, !dbg !14
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %n3.var), !dbg !15
+// CHECK:STDOUT:   store ptr %ReturnIntRRef__carbon_thunk.call, ptr %_.var.loc23, align 8, !dbg !14
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var.loc24), !dbg !15
 // CHECK:STDOUT:   %ReturnConstIntRef__carbon_thunk.call = call ptr @_Z17ReturnConstIntRef10ForceThunk.carbon_thunk0(), !dbg !21
-// CHECK:STDOUT:   store ptr %ReturnConstIntRef__carbon_thunk.call, ptr %n3.var, align 8, !dbg !15
+// CHECK:STDOUT:   store ptr %ReturnConstIntRef__carbon_thunk.call, ptr %_.var.loc24, align 8, !dbg !15
 // CHECK:STDOUT:   ret void, !dbg !22
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
@@ -627,10 +627,10 @@ fn GetRefs() {
 // CHECK:STDOUT: !13 = !DILocation(line: 22, column: 3, scope: !7)
 // CHECK:STDOUT: !14 = !DILocation(line: 23, column: 3, scope: !7)
 // CHECK:STDOUT: !15 = !DILocation(line: 24, column: 3, scope: !7)
-// CHECK:STDOUT: !16 = !DILocation(line: 18, column: 20, scope: !7)
-// CHECK:STDOUT: !17 = !DILocation(line: 19, column: 20, scope: !7)
-// CHECK:STDOUT: !18 = !DILocation(line: 20, column: 26, scope: !7)
-// CHECK:STDOUT: !19 = !DILocation(line: 22, column: 18, scope: !7)
-// CHECK:STDOUT: !20 = !DILocation(line: 23, column: 18, scope: !7)
-// CHECK:STDOUT: !21 = !DILocation(line: 24, column: 24, scope: !7)
+// CHECK:STDOUT: !16 = !DILocation(line: 18, column: 19, scope: !7)
+// CHECK:STDOUT: !17 = !DILocation(line: 19, column: 19, scope: !7)
+// CHECK:STDOUT: !18 = !DILocation(line: 20, column: 25, scope: !7)
+// CHECK:STDOUT: !19 = !DILocation(line: 22, column: 17, scope: !7)
+// CHECK:STDOUT: !20 = !DILocation(line: 23, column: 17, scope: !7)
+// CHECK:STDOUT: !21 = !DILocation(line: 24, column: 23, scope: !7)
 // CHECK:STDOUT: !22 = !DILocation(line: 17, column: 1, scope: !7)
diff --git a/toolchain/lower/testdata/interop/cpp/return.carbon b/toolchain/lower/testdata/interop/cpp/return.carbon
index ed628e71e850..292c2d99abc3 100644
--- a/toolchain/lower/testdata/interop/cpp/return.carbon
+++ b/toolchain/lower/testdata/interop/cpp/return.carbon
@@ -91,11 +91,11 @@ import Cpp library "class.h";
 fn GetX() -> Cpp.X { return Cpp.Make(); }
 
 fn Let() {
-  let x: Cpp.X = Cpp.Make();
+  let _: Cpp.X = Cpp.Make();
 }
 
 fn Var() {
-  var x: Cpp.X = Cpp.Make();
+  var _: Cpp.X = Cpp.Make();
 }
 
 // --- indirect_return_with_args.carbon
@@ -471,10 +471,10 @@ fn Call(x: Cpp.D) -> Cpp.C {
 // CHECK:STDOUT: ; Function Attrs: nounwind
 // CHECK:STDOUT: define void @_CVar.Main() #0 !dbg !18 {
 // CHECK:STDOUT: entry:
-// CHECK:STDOUT:   %x.var = alloca [16 x i8], align 1, !dbg !19
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %x.var), !dbg !19
-// CHECK:STDOUT:   call void @_Z4Makev.carbon_thunk(ptr %x.var), !dbg !20
-// CHECK:STDOUT:   call void @_ZN1XD1Ev(ptr %x.var), !dbg !19
+// CHECK:STDOUT:   %_.var = alloca [16 x i8], align 1, !dbg !19
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var), !dbg !19
+// CHECK:STDOUT:   call void @_Z4Makev.carbon_thunk(ptr %_.var), !dbg !20
+// CHECK:STDOUT:   call void @_ZN1XD1Ev(ptr %_.var), !dbg !19
 // CHECK:STDOUT:   ret void, !dbg !21
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
diff --git a/toolchain/lower/testdata/interop/cpp/virtual_base.carbon b/toolchain/lower/testdata/interop/cpp/virtual_base.carbon
index ee15e790f1fc..257125755c89 100644
--- a/toolchain/lower/testdata/interop/cpp/virtual_base.carbon
+++ b/toolchain/lower/testdata/interop/cpp/virtual_base.carbon
@@ -54,7 +54,7 @@ fn Make() {
   // mangled name for D (a complete object constructor), which should call
   // constructors with `...C2` mangled names for A, B, and C (base subobject
   // constructors).
-  var d: Cpp.D = Cpp.D.D();
+  var _: Cpp.D = Cpp.D.D();
 }
 
 fn AccessD(d: Cpp.D) -> i32 {
@@ -111,10 +111,10 @@ fn AccessD(d: Cpp.D) -> i32 {
 // CHECK:STDOUT: ; Function Attrs: nounwind
 // CHECK:STDOUT: define void @_CMake.Main() #0 !dbg !7 {
 // CHECK:STDOUT: entry:
-// CHECK:STDOUT:   %d.var = alloca [40 x i8], align 1, !dbg !10
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %d.var), !dbg !10
-// CHECK:STDOUT:   call void @_ZN1DC1Ev.carbon_thunk(ptr %d.var), !dbg !11
-// CHECK:STDOUT:   call void @_ZN1DD1Ev(ptr %d.var), !dbg !10
+// CHECK:STDOUT:   %_.var = alloca [40 x i8], align 1, !dbg !10
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var), !dbg !10
+// CHECK:STDOUT:   call void @_ZN1DC1Ev.carbon_thunk(ptr %_.var), !dbg !11
+// CHECK:STDOUT:   call void @_ZN1DD1Ev(ptr %_.var), !dbg !10
 // CHECK:STDOUT:   ret void, !dbg !12
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
diff --git a/toolchain/lower/testdata/operators/assignment.carbon b/toolchain/lower/testdata/operators/assignment.carbon
index b5224a825051..eda83a926138 100644
--- a/toolchain/lower/testdata/operators/assignment.carbon
+++ b/toolchain/lower/testdata/operators/assignment.carbon
@@ -10,31 +10,51 @@
 // TIP: To dump output, run:
 // TIP:   bazel run //toolchain/testing:file_test -- --dump_output --file_tests=toolchain/lower/testdata/operators/assignment.carbon
 
-fn Main() {
+fn F() -> i32 {
   var a: i32 = 12;
   a = 9;
+  return a;
+}
+
+fn G() -> (i32, i32) {
   var b: (i32, i32);
   b = (1, 2);
+  return b;
 }
 
 // CHECK:STDOUT: ; ModuleID = 'assignment.carbon'
 // CHECK:STDOUT: source_filename = "assignment.carbon"
 // CHECK:STDOUT:
-// CHECK:STDOUT: @tuple.21c.loc17_5 = internal constant { i32, i32 } { i32 1, i32 2 }
+// CHECK:STDOUT: @tuple.21c.loc21_5 = internal constant { i32, i32 } { i32 1, i32 2 }
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
-// CHECK:STDOUT: define void @_CMain.Main() #0 !dbg !4 {
+// CHECK:STDOUT: define i32 @_CF.Main() #0 !dbg !4 {
 // CHECK:STDOUT: entry:
-// CHECK:STDOUT:   %a.var = alloca i32, align 4, !dbg !7
-// CHECK:STDOUT:   %b.var = alloca { i32, i32 }, align 8, !dbg !8
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %a.var), !dbg !7
-// CHECK:STDOUT:   store i32 12, ptr %a.var, align 4, !dbg !7
+// CHECK:STDOUT:   %a.var = alloca i32, align 4, !dbg !8
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %a.var), !dbg !8
+// CHECK:STDOUT:   store i32 12, ptr %a.var, align 4, !dbg !8
 // CHECK:STDOUT:   store i32 9, ptr %a.var, align 4, !dbg !9
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %b.var), !dbg !8
-// CHECK:STDOUT:   %tuple.elem0.tuple.elem = getelementptr inbounds nuw { i32, i32 }, ptr %b.var, i32 0, i32 0, !dbg !10
-// CHECK:STDOUT:   %tuple.elem1.tuple.elem = getelementptr inbounds nuw { i32, i32 }, ptr %b.var, i32 0, i32 1, !dbg !10
-// CHECK:STDOUT:   call void @llvm.memcpy.p0.p0.i64(ptr align 4 %b.var, ptr align 4 @tuple.21c.loc17_5, i64 8, i1 false), !dbg !11
-// CHECK:STDOUT:   ret void, !dbg !12
+// CHECK:STDOUT:   %.loc16 = load i32, ptr %a.var, align 4, !dbg !10
+// CHECK:STDOUT:   ret i32 %.loc16, !dbg !11
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: ; Function Attrs: nounwind
+// CHECK:STDOUT: define void @_CG.Main(ptr sret({ i32, i32 }) %return) #0 !dbg !12 {
+// CHECK:STDOUT: entry:
+// CHECK:STDOUT:   %b.var = alloca { i32, i32 }, align 8, !dbg !16
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %b.var), !dbg !16
+// CHECK:STDOUT:   %tuple.elem0.loc21.tuple.elem = getelementptr inbounds nuw { i32, i32 }, ptr %b.var, i32 0, i32 0, !dbg !17
+// CHECK:STDOUT:   %tuple.elem1.loc21.tuple.elem = getelementptr inbounds nuw { i32, i32 }, ptr %b.var, i32 0, i32 1, !dbg !17
+// CHECK:STDOUT:   call void @llvm.memcpy.p0.p0.i64(ptr align 4 %b.var, ptr align 4 @tuple.21c.loc21_5, i64 8, i1 false), !dbg !18
+// CHECK:STDOUT:   %tuple.elem0.loc22_10.1.tuple.elem = getelementptr inbounds nuw { i32, i32 }, ptr %b.var, i32 0, i32 0, !dbg !19
+// CHECK:STDOUT:   %.loc22_10.1 = load i32, ptr %tuple.elem0.loc22_10.1.tuple.elem, align 4, !dbg !19
+// CHECK:STDOUT:   %tuple.elem0.loc22_10.2.tuple.elem = getelementptr inbounds nuw { i32, i32 }, ptr %return, i32 0, i32 0, !dbg !19
+// CHECK:STDOUT:   store i32 %.loc22_10.1, ptr %tuple.elem0.loc22_10.2.tuple.elem, align 4, !dbg !19
+// CHECK:STDOUT:   %tuple.elem1.loc22_10.1.tuple.elem = getelementptr inbounds nuw { i32, i32 }, ptr %b.var, i32 0, i32 1, !dbg !19
+// CHECK:STDOUT:   %.loc22_10.3 = load i32, ptr %tuple.elem1.loc22_10.1.tuple.elem, align 4, !dbg !19
+// CHECK:STDOUT:   %tuple.elem1.loc22_10.2.tuple.elem = getelementptr inbounds nuw { i32, i32 }, ptr %return, i32 0, i32 1, !dbg !19
+// CHECK:STDOUT:   store i32 %.loc22_10.3, ptr %tuple.elem1.loc22_10.2.tuple.elem, align 4, !dbg !19
+// CHECK:STDOUT:   ret void, !dbg !20
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nocallback nofree nosync nounwind willreturn memory(argmem: readwrite)
@@ -57,12 +77,20 @@ fn Main() {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "assignment.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Main", linkageName: "_CMain.Main", scope: null, file: !3, line: 13, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", linkageName: "_CF.Main", scope: null, file: !3, line: 13, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
-// CHECK:STDOUT: !6 = !{null}
-// CHECK:STDOUT: !7 = !DILocation(line: 14, column: 3, scope: !4)
-// CHECK:STDOUT: !8 = !DILocation(line: 16, column: 3, scope: !4)
+// CHECK:STDOUT: !6 = !{!7}
+// CHECK:STDOUT: !7 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+// CHECK:STDOUT: !8 = !DILocation(line: 14, column: 3, scope: !4)
 // CHECK:STDOUT: !9 = !DILocation(line: 15, column: 3, scope: !4)
-// CHECK:STDOUT: !10 = !DILocation(line: 17, column: 7, scope: !4)
-// CHECK:STDOUT: !11 = !DILocation(line: 17, column: 3, scope: !4)
-// CHECK:STDOUT: !12 = !DILocation(line: 13, column: 1, scope: !4)
+// CHECK:STDOUT: !10 = !DILocation(line: 16, column: 10, scope: !4)
+// CHECK:STDOUT: !11 = !DILocation(line: 16, column: 3, scope: !4)
+// CHECK:STDOUT: !12 = distinct !DISubprogram(name: "G", linkageName: "_CG.Main", scope: null, file: !3, line: 19, type: !13, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !13 = !DISubroutineType(types: !14)
+// CHECK:STDOUT: !14 = !{!15}
+// CHECK:STDOUT: !15 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: null, size: 8)
+// CHECK:STDOUT: !16 = !DILocation(line: 20, column: 3, scope: !12)
+// CHECK:STDOUT: !17 = !DILocation(line: 21, column: 7, scope: !12)
+// CHECK:STDOUT: !18 = !DILocation(line: 21, column: 3, scope: !12)
+// CHECK:STDOUT: !19 = !DILocation(line: 22, column: 10, scope: !12)
+// CHECK:STDOUT: !20 = !DILocation(line: 22, column: 3, scope: !12)
diff --git a/toolchain/lower/testdata/pointer/pointer_to_pointer.carbon b/toolchain/lower/testdata/pointer/pointer_to_pointer.carbon
index 2f36c2bf261f..ca4b8cdb4c30 100644
--- a/toolchain/lower/testdata/pointer/pointer_to_pointer.carbon
+++ b/toolchain/lower/testdata/pointer/pointer_to_pointer.carbon
@@ -11,7 +11,7 @@
 // TIP:   bazel run //toolchain/testing:file_test -- --dump_output --file_tests=toolchain/lower/testdata/pointer/pointer_to_pointer.carbon
 
 fn F(p: i32**) -> i32 {
-  var a: i32** = p;
+  var _: i32** = p;
   var b: i32* = *p;
   var c: i32** = &b;
   return **c;
@@ -23,11 +23,11 @@ fn F(p: i32**) -> i32 {
 // CHECK:STDOUT: ; Function Attrs: nounwind
 // CHECK:STDOUT: define i32 @_CF.Main(ptr %p) #0 !dbg !4 {
 // CHECK:STDOUT: entry:
-// CHECK:STDOUT:   %a.var = alloca ptr, align 8, !dbg !11
+// CHECK:STDOUT:   %_.var = alloca ptr, align 8, !dbg !11
 // CHECK:STDOUT:   %b.var = alloca ptr, align 8, !dbg !12
 // CHECK:STDOUT:   %c.var = alloca ptr, align 8, !dbg !13
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %a.var), !dbg !11
-// CHECK:STDOUT:   store ptr %p, ptr %a.var, align 8, !dbg !11
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var), !dbg !11
+// CHECK:STDOUT:   store ptr %p, ptr %_.var, align 8, !dbg !11
 // CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %b.var), !dbg !12
 // CHECK:STDOUT:   %.loc15_17.2 = load ptr, ptr %p, align 8, !dbg !14
 // CHECK:STDOUT:   store ptr %.loc15_17.2, ptr %b.var, align 8, !dbg !12
diff --git a/toolchain/lower/testdata/primitives/numeric_literals.carbon b/toolchain/lower/testdata/primitives/numeric_literals.carbon
index 7a312e901255..22b9378dfd94 100644
--- a/toolchain/lower/testdata/primitives/numeric_literals.carbon
+++ b/toolchain/lower/testdata/primitives/numeric_literals.carbon
@@ -13,13 +13,13 @@
 fn F() {
   // 8 and 9 trigger special behavior in APInt when mishandling signed versus
   // unsigned, so we pay extra attention to those.
-  var ints: array(i32, 4) = (
+  var _: array(i32, 4) = (
     8,
     9,
     0x8,
     0b1000,
   );
-  var floats: array(f64, 6) = (
+  var _: array(f64, 6) = (
     0.9,
     8.0,
     80.0,
@@ -38,22 +38,22 @@ fn F() {
 // CHECK:STDOUT: ; Function Attrs: nounwind
 // CHECK:STDOUT: define void @_CF.Main() #0 !dbg !4 {
 // CHECK:STDOUT: entry:
-// CHECK:STDOUT:   %ints.var = alloca [4 x i32], align 4, !dbg !7
-// CHECK:STDOUT:   %floats.var = alloca [6 x double], align 8, !dbg !8
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %ints.var), !dbg !7
-// CHECK:STDOUT:   %.loc21_3.3.array.index = getelementptr inbounds [4 x i32], ptr %ints.var, i32 0, i64 0, !dbg !9
-// CHECK:STDOUT:   %.loc21_3.6.array.index = getelementptr inbounds [4 x i32], ptr %ints.var, i32 0, i64 1, !dbg !9
-// CHECK:STDOUT:   %.loc21_3.9.array.index = getelementptr inbounds [4 x i32], ptr %ints.var, i32 0, i64 2, !dbg !9
-// CHECK:STDOUT:   %.loc21_3.12.array.index = getelementptr inbounds [4 x i32], ptr %ints.var, i32 0, i64 3, !dbg !9
-// CHECK:STDOUT:   call void @llvm.memcpy.p0.p0.i64(ptr align 4 %ints.var, ptr align 4 @array.712.loc16_3, i64 16, i1 false), !dbg !7
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %floats.var), !dbg !8
-// CHECK:STDOUT:   %.loc29_3.3.array.index = getelementptr inbounds [6 x double], ptr %floats.var, i32 0, i64 0, !dbg !10
-// CHECK:STDOUT:   %.loc29_3.6.array.index = getelementptr inbounds [6 x double], ptr %floats.var, i32 0, i64 1, !dbg !10
-// CHECK:STDOUT:   %.loc29_3.9.array.index = getelementptr inbounds [6 x double], ptr %floats.var, i32 0, i64 2, !dbg !10
-// CHECK:STDOUT:   %.loc29_3.12.array.index = getelementptr inbounds [6 x double], ptr %floats.var, i32 0, i64 3, !dbg !10
-// CHECK:STDOUT:   %.loc29_3.15.array.index = getelementptr inbounds [6 x double], ptr %floats.var, i32 0, i64 4, !dbg !10
-// CHECK:STDOUT:   %.loc29_3.18.array.index = getelementptr inbounds [6 x double], ptr %floats.var, i32 0, i64 5, !dbg !10
-// CHECK:STDOUT:   call void @llvm.memcpy.p0.p0.i64(ptr align 8 %floats.var, ptr align 8 @array.6e0.loc22_3, i64 48, i1 false), !dbg !8
+// CHECK:STDOUT:   %_.var.loc16 = alloca [4 x i32], align 4, !dbg !7
+// CHECK:STDOUT:   %_.var.loc22 = alloca [6 x double], align 8, !dbg !8
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var.loc16), !dbg !7
+// CHECK:STDOUT:   %.loc21_3.3.array.index = getelementptr inbounds [4 x i32], ptr %_.var.loc16, i32 0, i64 0, !dbg !9
+// CHECK:STDOUT:   %.loc21_3.6.array.index = getelementptr inbounds [4 x i32], ptr %_.var.loc16, i32 0, i64 1, !dbg !9
+// CHECK:STDOUT:   %.loc21_3.9.array.index = getelementptr inbounds [4 x i32], ptr %_.var.loc16, i32 0, i64 2, !dbg !9
+// CHECK:STDOUT:   %.loc21_3.12.array.index = getelementptr inbounds [4 x i32], ptr %_.var.loc16, i32 0, i64 3, !dbg !9
+// CHECK:STDOUT:   call void @llvm.memcpy.p0.p0.i64(ptr align 4 %_.var.loc16, ptr align 4 @array.712.loc16_3, i64 16, i1 false), !dbg !7
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var.loc22), !dbg !8
+// CHECK:STDOUT:   %.loc29_3.3.array.index = getelementptr inbounds [6 x double], ptr %_.var.loc22, i32 0, i64 0, !dbg !10
+// CHECK:STDOUT:   %.loc29_3.6.array.index = getelementptr inbounds [6 x double], ptr %_.var.loc22, i32 0, i64 1, !dbg !10
+// CHECK:STDOUT:   %.loc29_3.9.array.index = getelementptr inbounds [6 x double], ptr %_.var.loc22, i32 0, i64 2, !dbg !10
+// CHECK:STDOUT:   %.loc29_3.12.array.index = getelementptr inbounds [6 x double], ptr %_.var.loc22, i32 0, i64 3, !dbg !10
+// CHECK:STDOUT:   %.loc29_3.15.array.index = getelementptr inbounds [6 x double], ptr %_.var.loc22, i32 0, i64 4, !dbg !10
+// CHECK:STDOUT:   %.loc29_3.18.array.index = getelementptr inbounds [6 x double], ptr %_.var.loc22, i32 0, i64 5, !dbg !10
+// CHECK:STDOUT:   call void @llvm.memcpy.p0.p0.i64(ptr align 8 %_.var.loc22, ptr align 8 @array.6e0.loc22_3, i64 48, i1 false), !dbg !8
 // CHECK:STDOUT:   ret void, !dbg !11
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
@@ -83,6 +83,6 @@ fn F() {
 // CHECK:STDOUT: !6 = !{null}
 // CHECK:STDOUT: !7 = !DILocation(line: 16, column: 3, scope: !4)
 // CHECK:STDOUT: !8 = !DILocation(line: 22, column: 3, scope: !4)
-// CHECK:STDOUT: !9 = !DILocation(line: 16, column: 29, scope: !4)
-// CHECK:STDOUT: !10 = !DILocation(line: 22, column: 31, scope: !4)
+// CHECK:STDOUT: !9 = !DILocation(line: 16, column: 26, scope: !4)
+// CHECK:STDOUT: !10 = !DILocation(line: 22, column: 26, scope: !4)
 // CHECK:STDOUT: !11 = !DILocation(line: 13, column: 1, scope: !4)
diff --git a/toolchain/lower/testdata/primitives/optional.carbon b/toolchain/lower/testdata/primitives/optional.carbon
index 5e9b486f5e57..69d1cbccda95 100644
--- a/toolchain/lower/testdata/primitives/optional.carbon
+++ b/toolchain/lower/testdata/primitives/optional.carbon
@@ -21,14 +21,14 @@ fn Convert(o: Core.Optional(i32*)) -> Core.Optional(i32) {
 }
 
 fn AddOrRemoveConst(a: i32, b: const i32) {
-  var oa: Core.Optional(i32) = a;
-  var coa: const Core.Optional(i32) = a;
-  var oca: Core.Optional(const i32) = a;
-  var coca: const Core.Optional(const i32) = a;
-  var ob: Core.Optional(i32) = b;
-  var cob: const Core.Optional(i32) = b;
-  var ocb: Core.Optional(const i32) = b;
-  var cocb: const Core.Optional(const i32) = b;
+  var _: Core.Optional(i32) = a;
+  var _: const Core.Optional(i32) = a;
+  var _: Core.Optional(const i32) = a;
+  var _: const Core.Optional(const i32) = a;
+  var _: Core.Optional(i32) = b;
+  var _: const Core.Optional(i32) = b;
+  var _: Core.Optional(const i32) = b;
+  var _: const Core.Optional(const i32) = b;
 }
 
 // CHECK:STDOUT: ; ModuleID = 'optional.carbon'
@@ -54,30 +54,30 @@ fn AddOrRemoveConst(a: i32, b: const i32) {
 // CHECK:STDOUT: ; Function Attrs: nounwind
 // CHECK:STDOUT: define void @_CAddOrRemoveConst.Main(i32 %a, i32 %b) #0 !dbg !17 {
 // CHECK:STDOUT: entry:
-// CHECK:STDOUT:   %oa.var = alloca { i32, i1 }, align 8, !dbg !24
-// CHECK:STDOUT:   %coa.var = alloca { i32, i1 }, align 8, !dbg !25
-// CHECK:STDOUT:   %oca.var = alloca { i32, i1 }, align 8, !dbg !26
-// CHECK:STDOUT:   %coca.var = alloca { i32, i1 }, align 8, !dbg !27
-// CHECK:STDOUT:   %ob.var = alloca { i32, i1 }, align 8, !dbg !28
-// CHECK:STDOUT:   %cob.var = alloca { i32, i1 }, align 8, !dbg !29
-// CHECK:STDOUT:   %ocb.var = alloca { i32, i1 }, align 8, !dbg !30
-// CHECK:STDOUT:   %cocb.var = alloca { i32, i1 }, align 8, !dbg !31
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %oa.var), !dbg !24
-// CHECK:STDOUT:   call void @"_CConvert.8432e4edee1e3855:ImplicitAs.Core.76895dc907db9a3f"(ptr %oa.var, i32 %a), !dbg !24
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %coa.var), !dbg !25
-// CHECK:STDOUT:   call void @"_CConvert.b911a754667cc32d:ImplicitAs.Core.2ad288ff76f5b81b"(ptr %coa.var, i32 %a), !dbg !25
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %oca.var), !dbg !26
-// CHECK:STDOUT:   call void @"_CConvert.8432e4edee1e3855:ImplicitAs.Core.e4d8d712312f87c7"(ptr %oca.var, i32 %a), !dbg !26
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %coca.var), !dbg !27
-// CHECK:STDOUT:   call void @"_CConvert.b911a754667cc32d:ImplicitAs.Core.cb259d1cd9f87a45"(ptr %coca.var, i32 %a), !dbg !27
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %ob.var), !dbg !28
-// CHECK:STDOUT:   call void @"_CConvert.342b90dd3c63ffbd:ImplicitAs.Core.2ad288ff76f5b81b"(ptr %ob.var, i32 %b), !dbg !28
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %cob.var), !dbg !29
-// CHECK:STDOUT:   call void @"_CConvert.342b90dd3c63ffbd:ImplicitAs.Core.4625c39d8336f8c2"(ptr %cob.var, i32 %b), !dbg !29
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %ocb.var), !dbg !30
-// CHECK:STDOUT:   call void @"_CConvert.342b90dd3c63ffbd:ImplicitAs.Core.cb259d1cd9f87a45"(ptr %ocb.var, i32 %b), !dbg !30
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %cocb.var), !dbg !31
-// CHECK:STDOUT:   call void @"_CConvert.342b90dd3c63ffbd:ImplicitAs.Core.84138ae972513b15"(ptr %cocb.var, i32 %b), !dbg !31
+// CHECK:STDOUT:   %_.var.loc24 = alloca { i32, i1 }, align 8, !dbg !24
+// CHECK:STDOUT:   %_.var.loc25 = alloca { i32, i1 }, align 8, !dbg !25
+// CHECK:STDOUT:   %_.var.loc26 = alloca { i32, i1 }, align 8, !dbg !26
+// CHECK:STDOUT:   %_.var.loc27 = alloca { i32, i1 }, align 8, !dbg !27
+// CHECK:STDOUT:   %_.var.loc28 = alloca { i32, i1 }, align 8, !dbg !28
+// CHECK:STDOUT:   %_.var.loc29 = alloca { i32, i1 }, align 8, !dbg !29
+// CHECK:STDOUT:   %_.var.loc30 = alloca { i32, i1 }, align 8, !dbg !30
+// CHECK:STDOUT:   %_.var.loc31 = alloca { i32, i1 }, align 8, !dbg !31
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var.loc24), !dbg !24
+// CHECK:STDOUT:   call void @"_CConvert.8432e4edee1e3855:ImplicitAs.Core.76895dc907db9a3f"(ptr %_.var.loc24, i32 %a), !dbg !24
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var.loc25), !dbg !25
+// CHECK:STDOUT:   call void @"_CConvert.b911a754667cc32d:ImplicitAs.Core.2ad288ff76f5b81b"(ptr %_.var.loc25, i32 %a), !dbg !25
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var.loc26), !dbg !26
+// CHECK:STDOUT:   call void @"_CConvert.8432e4edee1e3855:ImplicitAs.Core.e4d8d712312f87c7"(ptr %_.var.loc26, i32 %a), !dbg !26
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var.loc27), !dbg !27
+// CHECK:STDOUT:   call void @"_CConvert.b911a754667cc32d:ImplicitAs.Core.cb259d1cd9f87a45"(ptr %_.var.loc27, i32 %a), !dbg !27
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var.loc28), !dbg !28
+// CHECK:STDOUT:   call void @"_CConvert.342b90dd3c63ffbd:ImplicitAs.Core.2ad288ff76f5b81b"(ptr %_.var.loc28, i32 %b), !dbg !28
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var.loc29), !dbg !29
+// CHECK:STDOUT:   call void @"_CConvert.342b90dd3c63ffbd:ImplicitAs.Core.4625c39d8336f8c2"(ptr %_.var.loc29, i32 %b), !dbg !29
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var.loc30), !dbg !30
+// CHECK:STDOUT:   call void @"_CConvert.342b90dd3c63ffbd:ImplicitAs.Core.cb259d1cd9f87a45"(ptr %_.var.loc30, i32 %b), !dbg !30
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var.loc31), !dbg !31
+// CHECK:STDOUT:   call void @"_CConvert.342b90dd3c63ffbd:ImplicitAs.Core.84138ae972513b15"(ptr %_.var.loc31, i32 %b), !dbg !31
 // CHECK:STDOUT:   ret void, !dbg !32
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
diff --git a/toolchain/lower/testdata/struct/empty.carbon b/toolchain/lower/testdata/struct/empty.carbon
index d09fca3c60ea..879a31c8daa7 100644
--- a/toolchain/lower/testdata/struct/empty.carbon
+++ b/toolchain/lower/testdata/struct/empty.carbon
@@ -12,7 +12,7 @@
 
 fn Run() -> i32 {
   var x: {} = {};
-  var y: {} = x;
+  var _: {} = x;
   return 0;
 }
 
@@ -23,9 +23,9 @@ fn Run() -> i32 {
 // CHECK:STDOUT: define i32 @main() #0 !dbg !4 {
 // CHECK:STDOUT: entry:
 // CHECK:STDOUT:   %x.var = alloca {}, align 8, !dbg !8
-// CHECK:STDOUT:   %y.var = alloca {}, align 8, !dbg !9
+// CHECK:STDOUT:   %_.var = alloca {}, align 8, !dbg !9
 // CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %x.var), !dbg !8
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %y.var), !dbg !9
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var), !dbg !9
 // CHECK:STDOUT:   ret i32 0, !dbg !10
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
diff --git a/toolchain/lower/testdata/struct/member_access.carbon b/toolchain/lower/testdata/struct/member_access.carbon
index 030404e47618..38346703912d 100644
--- a/toolchain/lower/testdata/struct/member_access.carbon
+++ b/toolchain/lower/testdata/struct/member_access.carbon
@@ -13,7 +13,7 @@
 fn Run() -> i32 {
   var x: {.a: f64, .b: i32} = {.a = 0.0, .b = 1};
   var y: i32 = x.b;
-  var z: i32 = y;
+  var _: i32 = y;
   return 0;
 }
 
@@ -27,7 +27,7 @@ fn Run() -> i32 {
 // CHECK:STDOUT: entry:
 // CHECK:STDOUT:   %x.var = alloca { double, i32 }, align 8, !dbg !8
 // CHECK:STDOUT:   %y.var = alloca i32, align 4, !dbg !9
-// CHECK:STDOUT:   %z.var = alloca i32, align 4, !dbg !10
+// CHECK:STDOUT:   %_.var = alloca i32, align 4, !dbg !10
 // CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %x.var), !dbg !8
 // CHECK:STDOUT:   %.loc14_48.3.a = getelementptr inbounds nuw { double, i32 }, ptr %x.var, i32 0, i32 0, !dbg !11
 // CHECK:STDOUT:   %.loc14_48.6.b = getelementptr inbounds nuw { double, i32 }, ptr %x.var, i32 0, i32 1, !dbg !11
@@ -36,9 +36,9 @@ fn Run() -> i32 {
 // CHECK:STDOUT:   %.loc15_17.1.b = getelementptr inbounds nuw { double, i32 }, ptr %x.var, i32 0, i32 1, !dbg !12
 // CHECK:STDOUT:   %.loc15_17.2 = load i32, ptr %.loc15_17.1.b, align 4, !dbg !12
 // CHECK:STDOUT:   store i32 %.loc15_17.2, ptr %y.var, align 4, !dbg !9
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %z.var), !dbg !10
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var), !dbg !10
 // CHECK:STDOUT:   %.loc16_16 = load i32, ptr %y.var, align 4, !dbg !13
-// CHECK:STDOUT:   store i32 %.loc16_16, ptr %z.var, align 4, !dbg !10
+// CHECK:STDOUT:   store i32 %.loc16_16, ptr %_.var, align 4, !dbg !10
 // CHECK:STDOUT:   ret i32 0, !dbg !14
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
diff --git a/toolchain/lower/testdata/struct/nested_struct_in_place.carbon b/toolchain/lower/testdata/struct/nested_struct_in_place.carbon
index 53d41acf4e96..860ca552ad6a 100644
--- a/toolchain/lower/testdata/struct/nested_struct_in_place.carbon
+++ b/toolchain/lower/testdata/struct/nested_struct_in_place.carbon
@@ -13,7 +13,7 @@
 fn F() -> (i32, i32, i32);
 
 fn G() {
-  var v: {.a: (i32, i32, i32), .b: (i32, i32, i32)} = {.a = F(), .b = F()};
+  var _: {.a: (i32, i32, i32), .b: (i32, i32, i32)} = {.a = F(), .b = F()};
 }
 
 // CHECK:STDOUT: ; ModuleID = 'nested_struct_in_place.carbon'
@@ -24,11 +24,11 @@ fn G() {
 // CHECK:STDOUT: ; Function Attrs: nounwind
 // CHECK:STDOUT: define void @_CG.Main() #0 !dbg !4 {
 // CHECK:STDOUT: entry:
-// CHECK:STDOUT:   %v.var = alloca { { i32, i32, i32 }, { i32, i32, i32 } }, align 8, !dbg !7
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %v.var), !dbg !7
-// CHECK:STDOUT:   %.loc16_74.1.a = getelementptr inbounds nuw { { i32, i32, i32 }, { i32, i32, i32 } }, ptr %v.var, i32 0, i32 0, !dbg !8
+// CHECK:STDOUT:   %_.var = alloca { { i32, i32, i32 }, { i32, i32, i32 } }, align 8, !dbg !7
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var), !dbg !7
+// CHECK:STDOUT:   %.loc16_74.1.a = getelementptr inbounds nuw { { i32, i32, i32 }, { i32, i32, i32 } }, ptr %_.var, i32 0, i32 0, !dbg !8
 // CHECK:STDOUT:   call void @_CF.Main(ptr %.loc16_74.1.a), !dbg !9
-// CHECK:STDOUT:   %.loc16_74.2.b = getelementptr inbounds nuw { { i32, i32, i32 }, { i32, i32, i32 } }, ptr %v.var, i32 0, i32 1, !dbg !8
+// CHECK:STDOUT:   %.loc16_74.2.b = getelementptr inbounds nuw { { i32, i32, i32 }, { i32, i32, i32 } }, ptr %_.var, i32 0, i32 1, !dbg !8
 // CHECK:STDOUT:   call void @_CF.Main(ptr %.loc16_74.2.b), !dbg !10
 // CHECK:STDOUT:   ret void, !dbg !11
 // CHECK:STDOUT: }
diff --git a/toolchain/lower/testdata/struct/one_entry.carbon b/toolchain/lower/testdata/struct/one_entry.carbon
index 7d22618e0230..a78d03543395 100644
--- a/toolchain/lower/testdata/struct/one_entry.carbon
+++ b/toolchain/lower/testdata/struct/one_entry.carbon
@@ -12,7 +12,7 @@
 
 fn Run() -> i32 {
   var x: {.a: i32} = {.a = 4};
-  var y: {.a: i32} = x;
+  var _: {.a: i32} = x;
   return 0;
 }
 
@@ -23,14 +23,14 @@ fn Run() -> i32 {
 // CHECK:STDOUT: define i32 @main() #0 !dbg !4 {
 // CHECK:STDOUT: entry:
 // CHECK:STDOUT:   %x.var = alloca { i32 }, align 8, !dbg !8
-// CHECK:STDOUT:   %y.var = alloca { i32 }, align 8, !dbg !9
+// CHECK:STDOUT:   %_.var = alloca { i32 }, align 8, !dbg !9
 // CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %x.var), !dbg !8
 // CHECK:STDOUT:   store { i32 } { i32 4 }, ptr %x.var, align 4, !dbg !8
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %y.var), !dbg !9
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var), !dbg !9
 // CHECK:STDOUT:   %.loc15_22.1.a = getelementptr inbounds nuw { i32 }, ptr %x.var, i32 0, i32 0, !dbg !10
 // CHECK:STDOUT:   %.loc15_22.2 = load i32, ptr %.loc15_22.1.a, align 4, !dbg !10
 // CHECK:STDOUT:   %.loc15_22.3.struct.init = insertvalue { i32 } poison, i32 %.loc15_22.2, 0, !dbg !10
-// CHECK:STDOUT:   store { i32 } %.loc15_22.3.struct.init, ptr %y.var, align 4, !dbg !9
+// CHECK:STDOUT:   store { i32 } %.loc15_22.3.struct.init, ptr %_.var, align 4, !dbg !9
 // CHECK:STDOUT:   ret i32 0, !dbg !11
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
diff --git a/toolchain/lower/testdata/struct/two_entries.carbon b/toolchain/lower/testdata/struct/two_entries.carbon
index 99923b3d861a..8f517c625613 100644
--- a/toolchain/lower/testdata/struct/two_entries.carbon
+++ b/toolchain/lower/testdata/struct/two_entries.carbon
@@ -12,7 +12,7 @@
 
 fn Run() -> i32 {
   var x: {.a: i32, .b: i32} = {.a = 1, .b = 2};
-  var y: {.a: i32, .b: i32} = x;
+  var _: {.a: i32, .b: i32} = x;
   return 0;
 }
 
@@ -25,19 +25,19 @@ fn Run() -> i32 {
 // CHECK:STDOUT: define i32 @main() #0 !dbg !4 {
 // CHECK:STDOUT: entry:
 // CHECK:STDOUT:   %x.var = alloca { i32, i32 }, align 8, !dbg !8
-// CHECK:STDOUT:   %y.var = alloca { i32, i32 }, align 8, !dbg !9
+// CHECK:STDOUT:   %_.var = alloca { i32, i32 }, align 8, !dbg !9
 // CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %x.var), !dbg !8
 // CHECK:STDOUT:   %.loc14_46.3.a = getelementptr inbounds nuw { i32, i32 }, ptr %x.var, i32 0, i32 0, !dbg !10
 // CHECK:STDOUT:   %.loc14_46.6.b = getelementptr inbounds nuw { i32, i32 }, ptr %x.var, i32 0, i32 1, !dbg !10
 // CHECK:STDOUT:   call void @llvm.memcpy.p0.p0.i64(ptr align 4 %x.var, ptr align 4 @struct.ed5.loc14_3, i64 8, i1 false), !dbg !8
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %y.var), !dbg !9
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var), !dbg !9
 // CHECK:STDOUT:   %.loc15_31.1.a = getelementptr inbounds nuw { i32, i32 }, ptr %x.var, i32 0, i32 0, !dbg !11
 // CHECK:STDOUT:   %.loc15_31.2 = load i32, ptr %.loc15_31.1.a, align 4, !dbg !11
-// CHECK:STDOUT:   %.loc15_31.3.a = getelementptr inbounds nuw { i32, i32 }, ptr %y.var, i32 0, i32 0, !dbg !11
+// CHECK:STDOUT:   %.loc15_31.3.a = getelementptr inbounds nuw { i32, i32 }, ptr %_.var, i32 0, i32 0, !dbg !11
 // CHECK:STDOUT:   store i32 %.loc15_31.2, ptr %.loc15_31.3.a, align 4, !dbg !11
 // CHECK:STDOUT:   %.loc15_31.5.b = getelementptr inbounds nuw { i32, i32 }, ptr %x.var, i32 0, i32 1, !dbg !11
 // CHECK:STDOUT:   %.loc15_31.6 = load i32, ptr %.loc15_31.5.b, align 4, !dbg !11
-// CHECK:STDOUT:   %.loc15_31.7.b = getelementptr inbounds nuw { i32, i32 }, ptr %y.var, i32 0, i32 1, !dbg !11
+// CHECK:STDOUT:   %.loc15_31.7.b = getelementptr inbounds nuw { i32, i32 }, ptr %_.var, i32 0, i32 1, !dbg !11
 // CHECK:STDOUT:   store i32 %.loc15_31.6, ptr %.loc15_31.7.b, align 4, !dbg !11
 // CHECK:STDOUT:   ret i32 0, !dbg !12
 // CHECK:STDOUT: }
diff --git a/toolchain/lower/testdata/tuple/access/element_access.carbon b/toolchain/lower/testdata/tuple/access/element_access.carbon
index 514dfc0f61ba..66ae2e3008b6 100644
--- a/toolchain/lower/testdata/tuple/access/element_access.carbon
+++ b/toolchain/lower/testdata/tuple/access/element_access.carbon
@@ -12,8 +12,8 @@
 
 fn Run() -> i32 {
   var a: (i32, i32, i32) = (0, 1, 2);
-  var b: i32 = a.0;
-  var c: i32 = a.2;
+  var _: i32 = a.0;
+  var _: i32 = a.2;
   return 0;
 }
 
@@ -26,21 +26,21 @@ fn Run() -> i32 {
 // CHECK:STDOUT: define i32 @main() #0 !dbg !4 {
 // CHECK:STDOUT: entry:
 // CHECK:STDOUT:   %a.var = alloca { i32, i32, i32 }, align 8, !dbg !8
-// CHECK:STDOUT:   %b.var = alloca i32, align 4, !dbg !9
-// CHECK:STDOUT:   %c.var = alloca i32, align 4, !dbg !10
+// CHECK:STDOUT:   %_.var.loc15 = alloca i32, align 4, !dbg !9
+// CHECK:STDOUT:   %_.var.loc16 = alloca i32, align 4, !dbg !10
 // CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %a.var), !dbg !8
 // CHECK:STDOUT:   %tuple.elem0.loc14.tuple.elem = getelementptr inbounds nuw { i32, i32, i32 }, ptr %a.var, i32 0, i32 0, !dbg !11
 // CHECK:STDOUT:   %tuple.elem1.tuple.elem = getelementptr inbounds nuw { i32, i32, i32 }, ptr %a.var, i32 0, i32 1, !dbg !11
 // CHECK:STDOUT:   %tuple.elem2.loc14.tuple.elem = getelementptr inbounds nuw { i32, i32, i32 }, ptr %a.var, i32 0, i32 2, !dbg !11
 // CHECK:STDOUT:   call void @llvm.memcpy.p0.p0.i64(ptr align 4 %a.var, ptr align 4 @tuple.d9f.loc14_3, i64 12, i1 false), !dbg !8
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %b.var), !dbg !9
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var.loc15), !dbg !9
 // CHECK:STDOUT:   %tuple.elem0.loc15.tuple.elem = getelementptr inbounds nuw { i32, i32, i32 }, ptr %a.var, i32 0, i32 0, !dbg !12
 // CHECK:STDOUT:   %.loc15_17 = load i32, ptr %tuple.elem0.loc15.tuple.elem, align 4, !dbg !12
-// CHECK:STDOUT:   store i32 %.loc15_17, ptr %b.var, align 4, !dbg !9
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %c.var), !dbg !10
+// CHECK:STDOUT:   store i32 %.loc15_17, ptr %_.var.loc15, align 4, !dbg !9
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var.loc16), !dbg !10
 // CHECK:STDOUT:   %tuple.elem2.loc16.tuple.elem = getelementptr inbounds nuw { i32, i32, i32 }, ptr %a.var, i32 0, i32 2, !dbg !13
 // CHECK:STDOUT:   %.loc16_17 = load i32, ptr %tuple.elem2.loc16.tuple.elem, align 4, !dbg !13
-// CHECK:STDOUT:   store i32 %.loc16_17, ptr %c.var, align 4, !dbg !10
+// CHECK:STDOUT:   store i32 %.loc16_17, ptr %_.var.loc16, align 4, !dbg !10
 // CHECK:STDOUT:   ret i32 0, !dbg !14
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
diff --git a/toolchain/lower/testdata/tuple/access/return_value_access.carbon b/toolchain/lower/testdata/tuple/access/return_value_access.carbon
index 0480bb162f68..d983762bf692 100644
--- a/toolchain/lower/testdata/tuple/access/return_value_access.carbon
+++ b/toolchain/lower/testdata/tuple/access/return_value_access.carbon
@@ -13,7 +13,7 @@
 fn F() -> (i32, i32) { return (12, 24); }
 
 fn Run() {
-  var t: i32 = F().1;
+  var _: i32 = F().1;
 }
 
 // CHECK:STDOUT: ; ModuleID = 'return_value_access.carbon'
@@ -33,14 +33,14 @@ fn Run() {
 // CHECK:STDOUT: ; Function Attrs: nounwind
 // CHECK:STDOUT: define void @main() #0 !dbg !10 {
 // CHECK:STDOUT: entry:
-// CHECK:STDOUT:   %t.var = alloca i32, align 4, !dbg !13
+// CHECK:STDOUT:   %_.var = alloca i32, align 4, !dbg !13
 // CHECK:STDOUT:   %.loc16_18.1.temp = alloca { i32, i32 }, align 8, !dbg !14
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %t.var), !dbg !13
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var), !dbg !13
 // CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %.loc16_18.1.temp), !dbg !14
 // CHECK:STDOUT:   call void @_CF.Main(ptr %.loc16_18.1.temp), !dbg !14
 // CHECK:STDOUT:   %tuple.elem1.tuple.elem = getelementptr inbounds nuw { i32, i32 }, ptr %.loc16_18.1.temp, i32 0, i32 1, !dbg !14
 // CHECK:STDOUT:   %.loc16_19 = load i32, ptr %tuple.elem1.tuple.elem, align 4, !dbg !14
-// CHECK:STDOUT:   store i32 %.loc16_19, ptr %t.var, align 4, !dbg !13
+// CHECK:STDOUT:   store i32 %.loc16_19, ptr %_.var, align 4, !dbg !13
 // CHECK:STDOUT:   ret void, !dbg !15
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
diff --git a/toolchain/lower/testdata/tuple/empty.carbon b/toolchain/lower/testdata/tuple/empty.carbon
index 45bb5caafa80..63dc8db0903d 100644
--- a/toolchain/lower/testdata/tuple/empty.carbon
+++ b/toolchain/lower/testdata/tuple/empty.carbon
@@ -12,7 +12,7 @@
 
 fn Run() -> i32 {
   var x: () = ();
-  var y: () = x;
+  var _: () = x;
   return 0;
 }
 
@@ -23,9 +23,9 @@ fn Run() -> i32 {
 // CHECK:STDOUT: define i32 @main() #0 !dbg !4 {
 // CHECK:STDOUT: entry:
 // CHECK:STDOUT:   %x.var = alloca {}, align 8, !dbg !8
-// CHECK:STDOUT:   %y.var = alloca {}, align 8, !dbg !9
+// CHECK:STDOUT:   %_.var = alloca {}, align 8, !dbg !9
 // CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %x.var), !dbg !8
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %y.var), !dbg !9
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var), !dbg !9
 // CHECK:STDOUT:   ret i32 0, !dbg !10
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
diff --git a/toolchain/lower/testdata/tuple/nested_tuple_in_place.carbon b/toolchain/lower/testdata/tuple/nested_tuple_in_place.carbon
index 5d5c0e9706e0..c90f70dbf65e 100644
--- a/toolchain/lower/testdata/tuple/nested_tuple_in_place.carbon
+++ b/toolchain/lower/testdata/tuple/nested_tuple_in_place.carbon
@@ -13,7 +13,7 @@
 fn F() -> (i32, i32, i32);
 
 fn G() {
-  var v: ((i32, i32, i32), (i32, i32, i32)) = (F(), F());
+  var _: ((i32, i32, i32), (i32, i32, i32)) = (F(), F());
 }
 
 // CHECK:STDOUT: ; ModuleID = 'nested_tuple_in_place.carbon'
@@ -24,11 +24,11 @@ fn G() {
 // CHECK:STDOUT: ; Function Attrs: nounwind
 // CHECK:STDOUT: define void @_CG.Main() #0 !dbg !4 {
 // CHECK:STDOUT: entry:
-// CHECK:STDOUT:   %v.var = alloca { { i32, i32, i32 }, { i32, i32, i32 } }, align 8, !dbg !7
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %v.var), !dbg !7
-// CHECK:STDOUT:   %tuple.elem0.tuple.elem = getelementptr inbounds nuw { { i32, i32, i32 }, { i32, i32, i32 } }, ptr %v.var, i32 0, i32 0, !dbg !8
+// CHECK:STDOUT:   %_.var = alloca { { i32, i32, i32 }, { i32, i32, i32 } }, align 8, !dbg !7
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var), !dbg !7
+// CHECK:STDOUT:   %tuple.elem0.tuple.elem = getelementptr inbounds nuw { { i32, i32, i32 }, { i32, i32, i32 } }, ptr %_.var, i32 0, i32 0, !dbg !8
 // CHECK:STDOUT:   call void @_CF.Main(ptr %tuple.elem0.tuple.elem), !dbg !9
-// CHECK:STDOUT:   %tuple.elem1.tuple.elem = getelementptr inbounds nuw { { i32, i32, i32 }, { i32, i32, i32 } }, ptr %v.var, i32 0, i32 1, !dbg !8
+// CHECK:STDOUT:   %tuple.elem1.tuple.elem = getelementptr inbounds nuw { { i32, i32, i32 }, { i32, i32, i32 } }, ptr %_.var, i32 0, i32 1, !dbg !8
 // CHECK:STDOUT:   call void @_CF.Main(ptr %tuple.elem1.tuple.elem), !dbg !10
 // CHECK:STDOUT:   ret void, !dbg !11
 // CHECK:STDOUT: }
diff --git a/toolchain/lower/testdata/tuple/one_entry.carbon b/toolchain/lower/testdata/tuple/one_entry.carbon
index 6c2f43b62a58..43b438e0a01c 100644
--- a/toolchain/lower/testdata/tuple/one_entry.carbon
+++ b/toolchain/lower/testdata/tuple/one_entry.carbon
@@ -12,7 +12,7 @@
 
 fn Run() -> i32 {
   var x: (i32, ) = (1, );
-  var y: (i32, ) = x;
+  var _: (i32, ) = x;
   return 0;
 }
 
@@ -23,14 +23,14 @@ fn Run() -> i32 {
 // CHECK:STDOUT: define i32 @main() #0 !dbg !4 {
 // CHECK:STDOUT: entry:
 // CHECK:STDOUT:   %x.var = alloca { i32 }, align 8, !dbg !8
-// CHECK:STDOUT:   %y.var = alloca { i32 }, align 8, !dbg !9
+// CHECK:STDOUT:   %_.var = alloca { i32 }, align 8, !dbg !9
 // CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %x.var), !dbg !8
 // CHECK:STDOUT:   store { i32 } { i32 1 }, ptr %x.var, align 4, !dbg !8
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %y.var), !dbg !9
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var), !dbg !9
 // CHECK:STDOUT:   %tuple.elem0.tuple.elem = getelementptr inbounds nuw { i32 }, ptr %x.var, i32 0, i32 0, !dbg !10
 // CHECK:STDOUT:   %.loc15_20.1 = load i32, ptr %tuple.elem0.tuple.elem, align 4, !dbg !10
 // CHECK:STDOUT:   %.loc15_20.2.tuple.init = insertvalue { i32 } poison, i32 %.loc15_20.1, 0, !dbg !10
-// CHECK:STDOUT:   store { i32 } %.loc15_20.2.tuple.init, ptr %y.var, align 4, !dbg !9
+// CHECK:STDOUT:   store { i32 } %.loc15_20.2.tuple.init, ptr %_.var, align 4, !dbg !9
 // CHECK:STDOUT:   ret i32 0, !dbg !11
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
diff --git a/toolchain/lower/testdata/tuple/two_entries.carbon b/toolchain/lower/testdata/tuple/two_entries.carbon
index fa84d02b9150..7313e33e3d5c 100644
--- a/toolchain/lower/testdata/tuple/two_entries.carbon
+++ b/toolchain/lower/testdata/tuple/two_entries.carbon
@@ -12,7 +12,7 @@
 
 fn Run() -> i32 {
   var x: (i32, i32) = (12, 7);
-  var y: (i32, i32) = x;
+  var _: (i32, i32) = x;
   return 0;
 }
 
@@ -25,19 +25,19 @@ fn Run() -> i32 {
 // CHECK:STDOUT: define i32 @main() #0 !dbg !4 {
 // CHECK:STDOUT: entry:
 // CHECK:STDOUT:   %x.var = alloca { i32, i32 }, align 8, !dbg !8
-// CHECK:STDOUT:   %y.var = alloca { i32, i32 }, align 8, !dbg !9
+// CHECK:STDOUT:   %_.var = alloca { i32, i32 }, align 8, !dbg !9
 // CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %x.var), !dbg !8
 // CHECK:STDOUT:   %tuple.elem0.loc14.tuple.elem = getelementptr inbounds nuw { i32, i32 }, ptr %x.var, i32 0, i32 0, !dbg !10
 // CHECK:STDOUT:   %tuple.elem1.loc14.tuple.elem = getelementptr inbounds nuw { i32, i32 }, ptr %x.var, i32 0, i32 1, !dbg !10
 // CHECK:STDOUT:   call void @llvm.memcpy.p0.p0.i64(ptr align 4 %x.var, ptr align 4 @tuple.d1d.loc14_3, i64 8, i1 false), !dbg !8
-// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %y.var), !dbg !9
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %_.var), !dbg !9
 // CHECK:STDOUT:   %tuple.elem0.loc15_23.1.tuple.elem = getelementptr inbounds nuw { i32, i32 }, ptr %x.var, i32 0, i32 0, !dbg !11
 // CHECK:STDOUT:   %.loc15_23.1 = load i32, ptr %tuple.elem0.loc15_23.1.tuple.elem, align 4, !dbg !11
-// CHECK:STDOUT:   %tuple.elem0.loc15_23.2.tuple.elem = getelementptr inbounds nuw { i32, i32 }, ptr %y.var, i32 0, i32 0, !dbg !11
+// CHECK:STDOUT:   %tuple.elem0.loc15_23.2.tuple.elem = getelementptr inbounds nuw { i32, i32 }, ptr %_.var, i32 0, i32 0, !dbg !11
 // CHECK:STDOUT:   store i32 %.loc15_23.1, ptr %tuple.elem0.loc15_23.2.tuple.elem, align 4, !dbg !11
 // CHECK:STDOUT:   %tuple.elem1.loc15_23.1.tuple.elem = getelementptr inbounds nuw { i32, i32 }, ptr %x.var, i32 0, i32 1, !dbg !11
 // CHECK:STDOUT:   %.loc15_23.3 = load i32, ptr %tuple.elem1.loc15_23.1.tuple.elem, align 4, !dbg !11
-// CHECK:STDOUT:   %tuple.elem1.loc15_23.2.tuple.elem = getelementptr inbounds nuw { i32, i32 }, ptr %y.var, i32 0, i32 1, !dbg !11
+// CHECK:STDOUT:   %tuple.elem1.loc15_23.2.tuple.elem = getelementptr inbounds nuw { i32, i32 }, ptr %_.var, i32 0, i32 1, !dbg !11
 // CHECK:STDOUT:   store i32 %.loc15_23.3, ptr %tuple.elem1.loc15_23.2.tuple.elem, align 4, !dbg !11
 // CHECK:STDOUT:   ret i32 0, !dbg !12
 // CHECK:STDOUT: }