Revert r236879, "Do not emit thunks with available_externally linkage in comdats"

It broke pecoff, at least i686-cygwin.

llvm-svn: 236937

clang/lib/CodeGen/CGVTables.cpp

@@ -378,6 +378,9 @@ void CodeGenFunction::GenerateThunk(llvm::Function *Fn,
   // 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<CXXMethodDecl>(GD.getDecl());
   setThunkVisibility(CGM, MD, Thunk, Fn);
@@ -458,7 +461,6 @@ void CodeGenVTables::emitThunk(GlobalDecl GD, const ThunkInfo &Thunk,
     CGM.getCXXABI().setThunkLinkage(ThunkFn, ForVTable, GD,
                                     !Thunk.Return.isEmpty());
   }
-  CGM.maybeSetTrivialComdat(*ThunkFn);
 }
 
 void CodeGenVTables::maybeEmitThunkForVTable(GlobalDecl GD,