[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

3 files changed, 16 insertions, 2 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);
diff --git a/clang/test/CodeGenCXX/microsoft-abi-eh-catch.cpp b/clang/test/CodeGenCXX/microsoft-abi-eh-catch.cpp
index 15edef3d131..292fad2e4d6 100644
--- a/clang/test/CodeGenCXX/microsoft-abi-eh-catch.cpp
+++ b/clang/test/CodeGenCXX/microsoft-abi-eh-catch.cpp
@@ -48,6 +48,18 @@ extern "C" void catch_int() {
 // WIN64: call void @handle_exception(i8* %[[e_i8]])
 // WIN64: call void @llvm.eh.endcatch()
 
+extern "C" void catch_int_unnamed() {
+  try {
+    might_throw();
+  } catch (int) {
+  }
+}
+
+// WIN64-LABEL: define void @catch_int_unnamed()
+// WIN64: landingpad { i8*, i32 }
+// WIN64: call void @llvm.eh.begincatch(i8* %{{.*}}, i8* null)
+// WIN64: call void @llvm.eh.endcatch()
+
 struct A {
   A();
   A(const A &o);
diff --git a/clang/test/CodeGenCXX/microsoft-abi-try-throw.cpp b/clang/test/CodeGenCXX/microsoft-abi-try-throw.cpp
index a3a45a54685..fed39761714 100644
--- a/clang/test/CodeGenCXX/microsoft-abi-try-throw.cpp
+++ b/clang/test/CodeGenCXX/microsoft-abi-try-throw.cpp
@@ -21,7 +21,7 @@ int main() {
     external(); // TRY: invoke void @"\01?external@@YAXXZ"
   } catch (int) {
     rv = 1;
-    // TRY: call void @llvm.eh.begincatch(i8* %{{.*}}, i8* %{{.*}})
+    // TRY: call void @llvm.eh.begincatch(i8* %{{.*}}, i8* null)
     // TRY: call void @llvm.eh.endcatch()
   }
 #endif