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[Clang][CodeGen] Do not emit lifetime intrinsics for coro promise alloca #140548

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[Clang][CodeGen] Do not emit lifetime intrinsics for coro promise alloca #140548

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d2e1a8d
Do not emit lifetime intrinsics for coro promise alloca
NewSigma May 19, 2025
8f3a3bd
Use VarDecl::getName instead of Value::getName
NewSigma May 20, 2025
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7 changes: 6 additions & 1 deletion clang/lib/CodeGen/CGDecl.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1599,9 +1599,14 @@ CodeGenFunction::EmitAutoVarAlloca(const VarDecl &D) {
bool IsMSCatchParam =
D.isExceptionVariable() && getTarget().getCXXABI().isMicrosoft();

// No lifetime intrinsics on coroutine promise alloca, or middle end
// passes will assume promise dead after lifetime.end, leading to
// mis-optimization
bool IsCoroPromise = D.getName() == "__promise";
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@ChuanqiXu9 ChuanqiXu9 May 20, 2025

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We should avoid comparing string as much as possible. And also it is not good to insert coroutines logic to CGDecl.cpp. We'd either doing this in CGCoroutine or CoroEarly.


// Emit a lifetime intrinsic if meaningful. There's no point in doing this
// if we don't have a valid insertion point (?).
if (HaveInsertPoint() && !IsMSCatchParam) {
if (HaveInsertPoint() && !IsMSCatchParam && !IsCoroPromise) {
// If there's a jump into the lifetime of this variable, its lifetime
// gets broken up into several regions in IR, which requires more work
// to handle correctly. For now, just omit the intrinsics; this is a
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3 changes: 0 additions & 3 deletions clang/test/CodeGenCoroutines/coro-params.cpp
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Expand Up @@ -84,7 +84,6 @@ void f(int val, MoveOnly moParam, MoveAndCopy mcParam, TrivialABI trivialParam)
// CHECK-NEXT: call void @_ZN11MoveAndCopyC1EOS_(ptr {{[^,]*}} %[[McCopy]], ptr noundef nonnull align 4 dereferenceable(4) %[[McParam]]) #
// CHECK-NEXT: call void @llvm.lifetime.start.p0(
// CHECK-NEXT: call void @_ZN10TrivialABIC1EOS_(ptr {{[^,]*}} %[[TrivialCopy]], ptr {{[^,]*}} %[[TrivialAlloca]])
// CHECK-NEXT: call void @llvm.lifetime.start.p0(
// CHECK-NEXT: invoke void @_ZNSt16coroutine_traitsIJvi8MoveOnly11MoveAndCopy10TrivialABIEE12promise_typeC1Ev(

// CHECK: call void @_ZN14suspend_always12await_resumeEv(
Expand All @@ -106,7 +105,6 @@ void f(int val, MoveOnly moParam, MoveAndCopy mcParam, TrivialABI trivialParam)

// Destroy promise, then parameter copies:
// CHECK: call void @_ZNSt16coroutine_traitsIJvi8MoveOnly11MoveAndCopy10TrivialABIEE12promise_typeD1Ev(ptr {{[^,]*}} %__promise)
// CHECK-NEXT: call void @llvm.lifetime.end.p0(
// CHECK-NEXT: call void @_ZN10TrivialABID1Ev(ptr {{[^,]*}} %[[TrivialCopy]])
// CHECK-NEXT: call void @llvm.lifetime.end.p0(
// CHECK-NEXT: call void @_ZN11MoveAndCopyD1Ev(ptr {{[^,]*}} %[[McCopy]])
Expand Down Expand Up @@ -135,7 +133,6 @@ void dependent_params(T x, U, U y) {
// CHECK-NEXT: call void @_ZN1BC1EOS_(ptr {{[^,]*}} %[[unnamed_copy]], ptr noundef nonnull align 4 dereferenceable(512) %0)
// CHECK-NEXT: call void @llvm.lifetime.start.p0(
// CHECK-NEXT: call void @_ZN1BC1EOS_(ptr {{[^,]*}} %[[y_copy]], ptr noundef nonnull align 4 dereferenceable(512) %y)
// CHECK-NEXT: call void @llvm.lifetime.start.p0(
// CHECK-NEXT: invoke void @_ZNSt16coroutine_traitsIJv1A1BS1_EE12promise_typeC1Ev(

co_return;
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2 changes: 1 addition & 1 deletion clang/test/CodeGenCoroutines/coro-suspend-cleanups.cpp
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Expand Up @@ -52,7 +52,7 @@ coroutine ArrayInitCoro() {
// CHECK-NEXT: store ptr %arrayinit.element, ptr %arrayinit.endOfInit.reload.addr, align 8
co_await Awaiter{}
// CHECK-NEXT: @_ZNSt14suspend_always11await_readyEv
// CHECK-NEXT: br i1 %{{.+}}, label %await.ready, label %CoroSave30
// CHECK-NEXT: br i1 %{{.+}}, label %await.ready, label %CoroSave29
};
// CHECK: await.cleanup: ; preds = %AfterCoroSuspend{{.*}}
// CHECK-NEXT: br label %cleanup{{.*}}.from.await.cleanup
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