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[CIR][CodeGen] Implement MayDropFunctionReturn for non-trivial destructor #2038

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Merged
merged 2 commits into from
Dec 2, 2025
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[CIR][CodeGen] Implement MayDropFunctionReturn for non-trivial destructor #2038

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09d9e9f
[CIR][CodeGen] Implement MayDropFunctionReturn for non-trivial destru…
bruteforceboy Nov 28, 2025
0762963
apply review comments: camel case & ogcg testing
bruteforceboy Dec 2, 2025
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6 changes: 4 additions & 2 deletions clang/lib/CIR/CodeGen/CIRGenCall.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1178,8 +1178,10 @@ bool CIRGenModule::MayDropFunctionReturn(const ASTContext &astContext,
QualType ReturnType) {
// We can't just disard the return value for a record type with a complex
// destructor or a non-trivially copyable type.
if (ReturnType.getCanonicalType()->getAs<RecordType>()) {
llvm_unreachable("NYI");
if (const RecordType *rt =
ReturnType.getCanonicalType()->getAs<RecordType>()) {
if (const auto *classDecl = dyn_cast<CXXRecordDecl>(rt->getDecl()))
return classDecl->hasTrivialDestructor();
}

return ReturnType.isTriviallyCopyableType(astContext);
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33 changes: 33 additions & 0 deletions clang/test/CIR/CodeGen/return.cpp
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@@ -1,4 +1,6 @@
// RUN: %clang_cc1 -std=c++17 -triple x86_64-unknown-linux-gnu -fclangir -emit-cir %s -o - | FileCheck %s
// RUN: %clang_cc1 -std=c++17 -triple x86_64-unknown-linux-gnu -fno-strict-return -fclangir -emit-llvm %s -o - | FileCheck %s --check-prefix=CHECK-NOSTRICT
// RUN: %clang_cc1 -std=c++17 -triple x86_64-unknown-linux-gnu -fno-strict-return -emit-llvm %s -o - | FileCheck %s --check-prefix=OGCG-CHECK-NOSTRICT

int &ret0(int &x) {
return x;
Expand Down Expand Up @@ -31,3 +33,34 @@ int unreachable_after_return() {
// CHECK-NEXT: cir.store{{.*}} %3, %0 : !s32i, !cir.ptr<!s32i>
// CHECK-NEXT: cir.br ^bb1
// CHECK-NEXT: }

struct NonTrivialDefaultConstructor {
int x;

NonTrivialDefaultConstructor() { }
};

// CHECK-NOSTRICT-LABEL: @_Z28nonTrivialDefaultConstructorv
// OGCG-CHECK-NOSTRICT-LABEL: @_Z28nonTrivialDefaultConstructorv
NonTrivialDefaultConstructor nonTrivialDefaultConstructor() {
// CHECK-NOSTRICT-NOT: call void @llvm.trap
// CHECK-NOSTRICT-NOT: unreachable
// OGCG-CHECK-NOSTRICT-NOT: call void @llvm.trap
// OGCG-CHECK-NOSTRICT-NOT: unreachable
}

// Functions that return records with non-trivial destructors should always use
// the -fstrict-return optimization.

struct NonTrivialDestructor {
~NonTrivialDestructor();
};

// CHECK-NOSTRICT-LABEL: @_Z20nonTrivialDestructorv
// OGCG-CHECK-NOSTRICT-LABEL: @_Z20nonTrivialDestructorv
NonTrivialDestructor nonTrivialDestructor() {
// CHECK-NOSTRICT: call void @llvm.trap
// CHECK-NOSTRICT-NEXT: unreachable
// OGCG-CHECK-NOSTRICT: call void @llvm.trap
// OGCG-CHECK-NOSTRICT-NEXT: unreachable
}