Revert r184205 and associated patches while investigating issue with broken buildbot (possible interaction with LTO)

<rdar://problem/14209661>

llvm-svn: 184384

clang/lib/CodeGen/CodeGenModule.cpp

@@ -722,14 +722,6 @@ void CodeGenModule::SetFunctionAttributes(GlobalDecl GD,
   if (!IsIncompleteFunction)
     SetLLVMFunctionAttributes(FD, getTypes().arrangeGlobalDeclaration(GD), F);
 
-  if (getCXXABI().HasThisReturn(GD)) {
-    assert(!F->arg_empty() &&
-           F->arg_begin()->getType()
-             ->canLosslesslyBitCastTo(F->getReturnType()) &&
-           "unexpected this return");
-    F->addAttribute(1, llvm::Attribute::Returned);
-  }
-
   // Only a few attributes are set on declarations; these may later be
   // overridden by a definition.