[clang] [llvm] [DirectX] Add target builtins (PR #134439)

[Helena Kotas via llvm-commits]

================
@@ -0,0 +1,23 @@
+//===- SemaDirectX.cpp - Semantic Analysis for DirectX constructs----------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+// This implements Semantic Analysis for DirectX constructs.
+//===----------------------------------------------------------------------===//
+
+#include "clang/Sema/SemaDirectX.h"
+#include "clang/Basic/TargetBuiltins.h"
+#include "clang/Sema/Sema.h"
+
+namespace clang {
+
+SemaDirectX::SemaDirectX(Sema &S) : SemaBase(S) {}
+
+bool SemaDirectX::CheckDirectXBuiltinFunctionCall(unsigned BuiltinID,
+                                                  CallExpr *TheCall) {
+  return false;
----------------
hekota wrote:

Is there really no checking needed for the `__builtin_dx_dot2add` call? Maybe add an empty switch to make that explicit?

```suggestion
switch (BuiltinID) {
  case DirectX::BI__builtin_dx_dot2add: 
    return false;
  }
  return false;
```

https://github.com/llvm/llvm-project/pull/134439