[WinEH] Don't create an alloca for unnamed catch parameters

The catch object parameter to llvm.eh.begincatch is optional, and can be
null. We can save some ourselves the stack space, copy ctor, and dtor
calls if we pass null.

llvm-svn: 234264

1 files changed, 3 insertions, 1 deletions

diff --git a/clang/lib/CodeGen/MicrosoftCXXABI.cpp b/clang/lib/CodeGen/MicrosoftCXXABI.cpp
index 2a76203e71c..f00cd9c81df 100644
--- a/clang/lib/CodeGen/MicrosoftCXXABI.cpp
+++ b/clang/lib/CodeGen/MicrosoftCXXABI.cpp
@@ -809,7 +809,9 @@ void MicrosoftCXXABI::emitBeginCatch(CodeGenFunction &CGF,
   llvm::Function *BeginCatch =
       CGF.CGM.getIntrinsic(llvm::Intrinsic::eh_begincatch);
 
-  if (!CatchParam) {
+  // If this is a catch-all or the catch parameter is unnamed, we don't need to
+  // emit an alloca to the object.
+  if (!CatchParam || !CatchParam->getDeclName()) {
     llvm::Value *Args[2] = {Exn, llvm::Constant::getNullValue(CGF.Int8PtrTy)};
     CGF.EmitNounwindRuntimeCall(BeginCatch, Args);
     CGF.EHStack.pushCleanup<CallEndCatchMSVC>(NormalAndEHCleanup);