[TypedThrows] Don't return undef : void.

LLVM doesn't like undef instances of void.

rdar://135631963

Author: nate-chandler

lib/IRGen/GenThunk.cpp

@@ -436,7 +436,8 @@ void IRGenThunk::emit() {
 
   // Return the result.
   if (result.empty()) {
-    if (emission->getTypedErrorExplosion()) {
+    if (emission->getTypedErrorExplosion() &&
+        !IGF.CurFn->getReturnType()->isVoidTy()) {
       IGF.Builder.CreateRet(llvm::UndefValue::get(IGF.CurFn->getReturnType()));
     } else {
       IGF.Builder.CreateRetVoid();

test/IRGen/typed_throws_thunks.swift

@@ -65,3 +65,60 @@ extension P {
   public func g3(body: () throws(FixedSize) -> Void) throws(FixedSize) {
   }
 }
+
+protocol P2 {
+// CHECK-LABEL: define{{.*}} swiftcc void @"$s19typed_throws_thunks2P2P1fyyAA1EOYKFTj"(
+// CHECK-SAME:      ptr noalias swiftself %0, 
+// CHECK-SAME:      ptr noalias nocapture swifterror dereferenceable(8) %1, 
+// CHECK-SAME:      ptr %2, ptr %3
+// CHECK-SAME:  )
+// CHECK-SAME:  {
+// CHECK:       failure:
+// CHECK-NOT:     ret void undef
+// CHECK:         ret void
+// CHECK:       success:
+// CHECK-NEXT:    ret void
+    func f() throws(E)
+// CHECK-LABEL: define{{.*}} swiftcc i8 @"$s19typed_throws_thunks2P2P1gyys4Int8VYKFTj"(
+// CHECk-SAME:      ptr noalias swiftself %0
+// CHECK-SAME:      ptr noalias nocapture swifterror dereferenceable(8) %1
+// CHECK-SAME:      ptr %2
+// CHECK-SAME:      ptr %3
+// CHECK-SAME:  )
+// CHECK-SAME:  {
+// CHECK:       failure:
+// CHECK-NEXT:    ret i8 %{{.*}}
+// CHECK:       success:
+// CHECK-NEXT:    ret i8 undef
+    func g() throws(Int8)
+// CHECK-LABEL: define{{.*}} swiftcc i8 @"$s19typed_throws_thunks2P2P1hs4Int8VyAA1EOYKFTj"(
+// CHECK-SAME:      ptr noalias swiftself %0
+// CHECK-SAME:      ptr noalias nocapture swifterror dereferenceable(8) %1
+// CHECK-SAME:      ptr %2 
+// CHECK-SAME:      ptr %3
+// CHECK-SAME:  )
+// CHECK-SAME:  {
+// CHECK:       failure:
+// CHECK-NEXT:    ret void
+// CHECK:       success:
+// CHECK-NEXT:    ret i8 %{{.*}}
+    func h() throws(E) -> Int8
+// CHECK-LABEL: define{{.*}} swiftcc i8 @"$s19typed_throws_thunks2P2P1is4Int8VyAFYKFTj"(
+// CHECK-SAME:      ptr noalias swiftself %0
+// CHECK-SAME:      ptr noalias nocapture swifterror dereferenceable(8) %1
+// CHECK-SAME:      ptr %2
+// CHECK-SAME:      ptr %3
+// CHECK-SAME:  )
+// CHECK-SAME:  {
+// CHECK:       failure:
+// CHECK-NEXT:    ret i8 %{{.*}}
+// CHECK:       success:
+// CHECK-NEXT:    ret i8 %{{.*}}
+    func i() throws(Int8) -> Int8
+}
+
+extension Int8 : Error {}
+
+enum E: Error {
+    case e
+}