Index: lib/CodeGen/CGVTables.cpp =================================================================== --- lib/CodeGen/CGVTables.cpp +++ lib/CodeGen/CGVTables.cpp @@ -378,9 +378,6 @@ // Set the right linkage. CGM.setFunctionLinkage(GD, Fn); - if (CGM.supportsCOMDAT() && Fn->isWeakForLinker()) - Fn->setComdat(CGM.getModule().getOrInsertComdat(Fn->getName())); - // Set the right visibility. const CXXMethodDecl *MD = cast(GD.getDecl()); setThunkVisibility(CGM, MD, Thunk, Fn); @@ -461,6 +458,7 @@ CGM.getCXXABI().setThunkLinkage(ThunkFn, ForVTable, GD, !Thunk.Return.isEmpty()); } + CGM.maybeSetTrivialComdat(*ThunkFn); } void CodeGenVTables::maybeEmitThunkForVTable(GlobalDecl GD, Index: lib/CodeGen/CodeGenModule.h =================================================================== --- lib/CodeGen/CodeGenModule.h +++ lib/CodeGen/CodeGenModule.h @@ -608,6 +608,7 @@ const llvm::Triple &getTriple() const; bool supportsCOMDAT() const; void maybeSetTrivialComdat(const Decl &D, llvm::GlobalObject &GO); + void maybeSetTrivialComdat(llvm::GlobalValue &GV); CGCXXABI &getCXXABI() const { return *ABI; } llvm::LLVMContext &getLLVMContext() { return VMContext; } Index: lib/CodeGen/CodeGenModule.cpp =================================================================== --- lib/CodeGen/CodeGenModule.cpp +++ lib/CodeGen/CodeGenModule.cpp @@ -1985,6 +1985,15 @@ GO.setComdat(TheModule.getOrInsertComdat(GO.getName())); } +void CodeGenModule::maybeSetTrivialComdat(llvm::GlobalValue &GV) { + if (!supportsCOMDAT()) + return; + if (GV.isWeakForLinker() && !GV.hasAvailableExternallyLinkage()) { + if (auto *GO = dyn_cast(&GV)) + GO->setComdat(getModule().getOrInsertComdat(GV.getName())); + } +} + void CodeGenModule::EmitGlobalVarDefinition(const VarDecl *D) { llvm::Constant *Init = nullptr; QualType ASTTy = D->getType(); Index: test/CodeGenCXX/thunks.cpp =================================================================== --- test/CodeGenCXX/thunks.cpp +++ test/CodeGenCXX/thunks.cpp @@ -1,5 +1,5 @@ // RUN: %clang_cc1 %s -triple=x86_64-pc-linux-gnu -munwind-tables -emit-llvm -o - | FileCheck %s -// RUN: %clang_cc1 %s -triple=x86_64-pc-linux-gnu -munwind-tables -emit-llvm -o - -O1 -disable-llvm-optzns | FileCheck %s +// RUN: %clang_cc1 %s -triple=x86_64-pc-linux-gnu -munwind-tables -emit-llvm -o - -O1 -disable-llvm-optzns | FileCheck %s --check-prefix=CHECK --check-prefix=CHECKOPT namespace Test1 { @@ -361,6 +361,28 @@ // CHECK: declare void @_ZThn8_N6Test151C1fEiz } +namespace Test16 { + +// Check that the thunk for 'B::f' has available_externally linkage +// and is not in a comdat. + +template +struct A { + virtual void f(); +}; + +template +struct B : virtual A { + virtual void f() { } +}; + +extern template struct B; + +void f(B b) { + b.f(); +} +} + /**** The following has to go at the end of the file ****/ // This is from Test5: @@ -371,4 +393,7 @@ // CHECK-LABEL: define linkonce_odr void @_ZN6Test101C3fooEv // CHECK-LABEL: define linkonce_odr void @_ZThn8_N6Test101C3fooEv +// CHECKOPT-LABEL: define available_externally void @_ZTv0_n24_N6Test161BIiE1fEv +// CHECKOPT-NOT: comdat + // CHECK: attributes [[NUW]] = { nounwind uwtable{{.*}} }