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[IR] Make dead_on_return attribute optionally sized #171712

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Merged
boomanaiden154 merged 10 commits into from
Jan 21, 2026
Merged

[IR] Make dead_on_return attribute optionally sized #171712

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7de1d77
[𝘀𝗽𝗿] initial version
boomanaiden154 Dec 10, 2025
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bitcode autoupgrade
boomanaiden154 Dec 10, 2025
6e65f88
formatting
boomanaiden154 Dec 10, 2025
fe16fe0
update
boomanaiden154 Dec 22, 2025
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update
boomanaiden154 Dec 22, 2025
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feedback
boomanaiden154 Dec 22, 2025
4d6de09
fix
boomanaiden154 Dec 22, 2025
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boomanaiden154 Jan 11, 2026
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boomanaiden154 Jan 20, 2026
ec48d72
rebase/test fixes
boomanaiden154 Jan 21, 2026
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2 changes: 1 addition & 1 deletion clang/lib/CodeGen/CGCall.cpp
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Expand Up @@ -2884,7 +2884,7 @@ void CodeGenModule::ConstructAttributeList(StringRef Name,
// (e.g., Obj-C ARC-managed structs, MSVC callee-destroyed objects).
if (!ParamType.isDestructedType() || !ParamType->isRecordType() ||
ParamType->castAsRecordDecl()->isParamDestroyedInCallee())
Attrs.addAttribute(llvm::Attribute::DeadOnReturn);
Attrs.addDeadOnReturnAttr(llvm::DeadOnReturnInfo());
}
}

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2 changes: 1 addition & 1 deletion clang/test/CodeGen/AArch64/args.cpp
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Expand Up @@ -34,7 +34,7 @@ EXTERNC int empty_align16_arg(struct EmptyAlign16 a, int b) {
return b;
}

// CXX: define{{.*}} i32 @empty_align32_arg(ptr dead_on_return noundef %a, i32 noundef %b)
// CXX: define{{.*}} i32 @empty_align32_arg(ptr noundef dead_on_return %a, i32 noundef %b)
struct EmptyAlign32 { long long int __attribute__((aligned(32))) : 0; };
EXTERNC int empty_align32_arg(struct EmptyAlign32 a, int b) {
return b;
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16 changes: 8 additions & 8 deletions clang/test/CodeGen/AArch64/byval-temp.c
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Expand Up @@ -30,10 +30,10 @@ void example(void) {
// Then, memcpy `l` to the temporary stack space.
// CHECK-O0-NEXT: call void @llvm.memcpy.p0.p0.i64(ptr align 8 %[[byvaltemp]], ptr align 8 %[[l]], i64 64, i1 false)
// Finally, call using a pointer to the temporary stack space.
// CHECK-O0-NEXT: call void @pass_large(ptr dead_on_return noundef %[[byvaltemp]])
// CHECK-O0-NEXT: call void @pass_large(ptr noundef dead_on_return %[[byvaltemp]])
// Now, do the same for the second call, using the second temporary alloca.
// CHECK-O0-NEXT: call void @llvm.memcpy.p0.p0.i64(ptr align 8 %[[byvaltemp1]], ptr align 8 %[[l]], i64 64, i1 false)
// CHECK-O0-NEXT: call void @pass_large(ptr dead_on_return noundef %[[byvaltemp1]])
// CHECK-O0-NEXT: call void @pass_large(ptr noundef dead_on_return %[[byvaltemp1]])
// CHECK-O0-NEXT: ret void
//
// At O3, we should have lifetime markers to help the optimizer re-use the temporary allocas.
Expand All @@ -58,15 +58,15 @@ void example(void) {
// Then, memcpy `l` to the temporary stack space.
// CHECK-O3-NEXT: call void @llvm.memcpy.p0.p0.i64(ptr align 8 %[[byvaltemp]], ptr align 8 %[[l]], i64 64, i1 false)
// Finally, call using a pointer to the temporary stack space.
// CHECK-O3-NEXT: call void @pass_large(ptr dead_on_return noundef %[[byvaltemp]])
// CHECK-O3-NEXT: call void @pass_large(ptr noundef dead_on_return %[[byvaltemp]])
//
// The lifetime of the temporary used to pass a pointer to the struct ends here.
// CHECK-O3-NEXT: call void @llvm.lifetime.end.p0(ptr %[[byvaltemp]])
//
// Now, do the same for the second call, using the second temporary alloca.
// CHECK-O3-NEXT: call void @llvm.lifetime.start.p0(ptr %[[byvaltemp1]])
// CHECK-O3-NEXT: call void @llvm.memcpy.p0.p0.i64(ptr align 8 %[[byvaltemp1]], ptr align 8 %[[l]], i64 64, i1 false)
// CHECK-O3-NEXT: call void @pass_large(ptr dead_on_return noundef %[[byvaltemp1]])
// CHECK-O3-NEXT: call void @pass_large(ptr noundef dead_on_return %[[byvaltemp1]])
// CHECK-O3-NEXT: call void @llvm.lifetime.end.p0(ptr %[[byvaltemp1]])
//
// Mark the end of the lifetime of `l`.
Expand All @@ -88,12 +88,12 @@ void example_BitInt(void) {
// CHECK-O0-NEXT: [[LOADEDV:%.*]] = trunc i256 [[TMP0]] to i129
// CHECK-O0-NEXT: [[STOREDV:%.*]] = sext i129 [[LOADEDV]] to i256
// CHECK-O0-NEXT: store i256 [[STOREDV]], ptr [[INDIRECT_ARG_TEMP]], align 16
// CHECK-O0-NEXT: call void @pass_large_BitInt(ptr dead_on_return noundef [[INDIRECT_ARG_TEMP]])
// CHECK-O0-NEXT: call void @pass_large_BitInt(ptr noundef dead_on_return [[INDIRECT_ARG_TEMP]])
// CHECK-O0-NEXT: [[TMP1:%.*]] = load i256, ptr [[L]], align 16
// CHECK-O0-NEXT: [[LOADEDV1:%.*]] = trunc i256 [[TMP1]] to i129
// CHECK-O0-NEXT: [[STOREDV1:%.*]] = sext i129 [[LOADEDV1]] to i256
// CHECK-O0-NEXT: store i256 [[STOREDV1]], ptr [[INDIRECT_ARG_TEMP1]], align 16
// CHECK-O0-NEXT: call void @pass_large_BitInt(ptr dead_on_return noundef [[INDIRECT_ARG_TEMP1]])
// CHECK-O0-NEXT: call void @pass_large_BitInt(ptr noundef dead_on_return [[INDIRECT_ARG_TEMP1]])
// CHECK-O0-NEXT: ret void
//
// CHECK-O3-LABEL: define dso_local void @example_BitInt(
Expand All @@ -108,13 +108,13 @@ void example_BitInt(void) {
// CHECK-O3-NEXT: call void @llvm.lifetime.start.p0(ptr [[INDIRECT_ARG_TEMP]])
// CHECK-O3-NEXT: [[STOREDV:%.*]] = sext i129 [[LOADEDV]] to i256
// CHECK-O3-NEXT: store i256 [[STOREDV]], ptr [[INDIRECT_ARG_TEMP]], align 16, !tbaa [[TBAA6]]
// CHECK-O3-NEXT: call void @pass_large_BitInt(ptr dead_on_return noundef [[INDIRECT_ARG_TEMP]])
// CHECK-O3-NEXT: call void @pass_large_BitInt(ptr noundef dead_on_return [[INDIRECT_ARG_TEMP]])
// CHECK-O3-NEXT: call void @llvm.lifetime.end.p0(ptr [[INDIRECT_ARG_TEMP]])
// CHECK-O3-NEXT: [[TMP1:%.*]] = load i256, ptr [[L]], align 16, !tbaa [[TBAA6]]
// CHECK-O3-NEXT: [[LOADEDV1:%.*]] = trunc i256 [[TMP1]] to i129
// CHECK-O3-NEXT: call void @llvm.lifetime.start.p0(ptr [[INDIRECT_ARG_TEMP1]])
// CHECK-O3-NEXT: [[STOREDV1:%.*]] = sext i129 [[LOADEDV1]] to i256
// CHECK-O3-NEXT: store i256 [[STOREDV1]], ptr [[INDIRECT_ARG_TEMP1]], align 16, !tbaa [[TBAA6]]
// CHECK-O3-NEXT: call void @pass_large_BitInt(ptr dead_on_return noundef [[INDIRECT_ARG_TEMP1]])
// CHECK-O3-NEXT: call void @pass_large_BitInt(ptr noundef dead_on_return [[INDIRECT_ARG_TEMP1]])
// CHECK-O3-NEXT: call void @llvm.lifetime.end.p0(ptr [[INDIRECT_ARG_TEMP1]])
// CHECK-O3-NEXT: call void @llvm.lifetime.end.p0(ptr [[L]])
2 changes: 1 addition & 1 deletion clang/test/CodeGen/AArch64/pure-scalable-args-empty-union.c
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Expand Up @@ -19,7 +19,7 @@ void f0(S0 *p) {
use0(*p);
}
// CHECK-C: declare void @use0(<vscale x 4 x float>, <vscale x 4 x float>, <vscale x 4 x float>, <vscale x 4 x float>)
// CHECK-CXX: declare void @use0(ptr dead_on_return noundef)
// CHECK-CXX: declare void @use0(ptr noundef dead_on_return)

#ifdef __cplusplus

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