https://github.com/ChuanqiXu9 created https://github.com/llvm/llvm-project/pull/93530
Close https://github.com/llvm/llvm-project/issues/93497 The root cause of the problem is, we mark the variable from other modules as constnant in LLVM incorrectly. This patch fixes this problem and only mark the variable from other modules as constant if its initializer is const. >From 778205df51376ddd38253b2ce5bab9dcab512774 Mon Sep 17 00:00:00 2001 From: Chuanqi Xu <yedeng...@linux.alibaba.com> Date: Tue, 28 May 2024 18:44:18 +0800 Subject: [PATCH] [C++20] [Modules] Don't mark variables from other modules as constant if its initializer is not constant Close https://github.com/llvm/llvm-project/issues/93497 The root cause of the problem is, we mark the variable from other modules as constnant in LLVM incorrectly. This patch fixes this problem and only mark the variable from other modules as constant if its initializer is const. --- clang/lib/CodeGen/CodeGenModule.cpp | 2 + clang/test/Modules/pr93497.cppm | 81 +++++++++++++++++++++++++++++ 2 files changed, 83 insertions(+) create mode 100644 clang/test/Modules/pr93497.cppm diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp index e4774a587707a..5596a6708e4a1 100644 --- a/clang/lib/CodeGen/CodeGenModule.cpp +++ b/clang/lib/CodeGen/CodeGenModule.cpp @@ -5492,6 +5492,8 @@ void CodeGenModule::EmitGlobalVarDefinition(const VarDecl *D, // If it is safe to mark the global 'constant', do so now. GV->setConstant(!NeedsGlobalCtor && !NeedsGlobalDtor && + (!IsDefinitionAvailableExternally || + D->hasConstantInitialization()) && D->getType().isConstantStorage(getContext(), true, true)); // If it is in a read-only section, mark it 'constant'. diff --git a/clang/test/Modules/pr93497.cppm b/clang/test/Modules/pr93497.cppm new file mode 100644 index 0000000000000..dc0d8eb462e27 --- /dev/null +++ b/clang/test/Modules/pr93497.cppm @@ -0,0 +1,81 @@ +// RUN: rm -rf %t +// RUN: mkdir -p %t +// RUN: split-file %s %t + +// RUN: %clang_cc1 -triple %itanium_abi_triple -std=c++20 %t/mod.cppm \ +// RUN: -emit-module-interface -o %t/mod.pcm +// RUN: %clang_cc1 -triple %itanium_abi_triple -std=c++20 %t/use.cpp \ +// RUN: -fmodule-file=mod=%t/mod.pcm -emit-llvm \ +// RUN: -o - | FileCheck %t/use.cpp + +//--- mod.cppm +export module mod; + +export struct Thing { + static const Thing One; + explicit Thing(int raw) :raw(raw) { } + int raw; +}; + +const Thing Thing::One = Thing(1); + +export struct C { + int value; +}; +export const C ConstantValue = {1}; + +export const C *ConstantPtr = &ConstantValue; + +C NonConstantValue = {1}; +export const C &ConstantRef = NonConstantValue; + +//--- use.cpp +import mod; + +int consume(int); +int consumeC(C); + +extern "C" __attribute__((noinline)) inline int unneeded() { + return consume(43); +} + +extern "C" __attribute__((noinline)) inline int needed() { + return consume(43); +} + +int use() { + Thing t1 = Thing::One; + return consume(t1.raw); +} + +int use2() { + if (ConstantValue.value) + return consumeC(ConstantValue); + return unneeded(); +} + +int use3() { + if (ConstantPtr->value) + return consumeC(*ConstantPtr); + return needed(); +} + +int use4() { + if (ConstantRef.value) + return consumeC(ConstantRef); + return needed(); +} + +// CHECK-NOT: @_ZNW3mod5Thing3OneE = {{.*}}constant +// CHECK: @_ZW3mod13ConstantValue ={{.*}}available_externally{{.*}} constant + +// Check that the middle end can optimize the program by the constant information. +// CHECK-NOT: @unneeded( + +// Check that the use of ConstantPtr won't get optimized incorrectly. +// CHECK-LABEL: @_Z4use3v( +// CHECK: @needed( + +// Check that the use of ConstantRef won't get optimized incorrectly. +// CHECK-LABEL: @_Z4use4v( +// CHECK: @needed( _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
