Do not emit thunks with available_externally linkage in comdats

Functions with available_externally linkage will not be emitted to object
files (they will just be undefined symbols), so it does not make sense to
put them in comdats.

Creates a second overload of maybeSetTrivialComdat that uses the GlobalObject
instead of the Decl, and uses that in several places that had the faulty
logic.

Differential Revision: http://reviews.llvm.org/D9580

llvm-svn: 236879

1 files changed, 12 insertions, 11 deletions

diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index d75dcd2..b3d7b5d 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -1298,8 +1298,7 @@ llvm::Constant *CodeGenModule::GetAddrOfUuidDescriptor(
   auto *GV = new llvm::GlobalVariable(
       getModule(), Init->getType(),
       /*isConstant=*/true, llvm::GlobalValue::LinkOnceODRLinkage, Init, Name);
-  if (supportsCOMDAT())
-    GV->setComdat(TheModule.getOrInsertComdat(GV->getName()));
+  maybeSetTrivialComdat(*GV);
   return GV;
 }
 
@@ -1850,9 +1849,7 @@ CodeGenModule::CreateOrReplaceCXXRuntimeVariable(StringRef Name,
     OldGV->eraseFromParent();
   }
 
-  if (supportsCOMDAT() && GV->isWeakForLinker() &&
-      !GV->hasAvailableExternallyLinkage())
-    GV->setComdat(TheModule.getOrInsertComdat(GV->getName()));
+  maybeSetTrivialComdat(*GV);
 
   return GV;
 }
@@ -1985,6 +1982,14 @@ void CodeGenModule::maybeSetTrivialComdat(const Decl &D,
   GO.setComdat(TheModule.getOrInsertComdat(GO.getName()));
 }
 
+void CodeGenModule::maybeSetTrivialComdat(llvm::GlobalObject &GO) {
+  if (!supportsCOMDAT())
+    return;
+  if (GO.isWeakForLinker() && !GO.hasAvailableExternallyLinkage()) {
+    GO.setComdat(getModule().getOrInsertComdat(GO.getName()));
+  }
+}
+
 void CodeGenModule::EmitGlobalVarDefinition(const VarDecl *D) {
   llvm::Constant *Init = nullptr;
   QualType ASTTy = D->getType();
@@ -2924,10 +2929,7 @@ GenerateStringLiteral(llvm::Constant *C, llvm::GlobalValue::LinkageTypes LT,
       nullptr, llvm::GlobalVariable::NotThreadLocal, AddrSpace);
   GV->setAlignment(Alignment);
   GV->setUnnamedAddr(true);
-  if (GV->isWeakForLinker()) {
-    assert(CGM.supportsCOMDAT() && "Only COFF uses weak string literals");
-    GV->setComdat(M.getOrInsertComdat(GV->getName()));
-  }
+  CGM.maybeSetTrivialComdat(*GV);
 
   return GV;
 }
@@ -3109,8 +3111,7 @@ llvm::Constant *CodeGenModule::GetAddrOfGlobalTemporary(
   setGlobalVisibility(GV, VD);
   GV->setAlignment(
       getContext().getTypeAlignInChars(MaterializedType).getQuantity());
-  if (supportsCOMDAT() && GV->isWeakForLinker())
-    GV->setComdat(TheModule.getOrInsertComdat(GV->getName()));
+  maybeSetTrivialComdat(*GV);
   if (VD->getTLSKind())
     setTLSMode(GV, *VD);
   Slot = GV;