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[Clang][CodeGen] Bail out on constexpr unknown values in ConstantEmitter #127525

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[Clang][CodeGen] Bail out on constexpr unknown values in ConstantEmitter #127525

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d931667
[Clang][CodeGen] Bail out on constexpr unknown values in ConstantEmitter
dtcxzyw Feb 17, 2025
9eb4a88
Address review comments. NFC.
dtcxzyw Feb 18, 2025
269f93f
[Clang][CodeGen] Address review comments. NFC.
dtcxzyw Feb 21, 2025
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4 changes: 3 additions & 1 deletion clang/lib/CodeGen/CGExprConstant.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1883,7 +1883,9 @@ llvm::Constant *ConstantEmitter::tryEmitPrivateForVarInit(const VarDecl &D) {

// Try to emit the initializer. Note that this can allow some things that
// are not allowed by tryEmitPrivateForMemory alone.
if (APValue *value = D.evaluateValue())
// Bail out on constexpr-unknown values since they are invalid in CodeGen.
if (APValue *value = D.evaluateValue();
value && !value->allowConstexprUnknown())
return tryEmitPrivateForMemory(*value, destType);

return nullptr;
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15 changes: 15 additions & 0 deletions clang/test/CodeGenCXX/cxx23-p2280r4.cpp
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@@ -0,0 +1,15 @@
// RUN: %clang_cc1 -triple %itanium_abi_triple -std=c++23 %s -emit-llvm -o - | FileCheck %s
// RUN: %clang_cc1 -triple %itanium_abi_triple -std=c++20 %s -emit-llvm -o - | FileCheck %s
// RUN: %clang_cc1 -triple %itanium_abi_triple -std=c++17 %s -emit-llvm -o - | FileCheck %s

extern int& s;

// CHECK: @_Z4testv()
// CHECK-NEXT: entry:
// CHECK-NEXT: [[I:%.*]] = alloca ptr, align {{.*}}
// CHECK-NEXT: [[X:%.*]] = load ptr, ptr @s, align {{.*}}
// CHECK-NEXT: store ptr [[X]], ptr [[I]], align {{.*}}
int& test() {
auto &i = s;
return i;
}
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