[libclc] [libclc] Add OpenCL atomic_*_explicit builtins (PR #168318)

[Matt Arsenault via cfe-commits]

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@@ -0,0 +1,48 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef __CLC_OPENCL_TYPES_H__
+#define __CLC_OPENCL_TYPES_H__
+
+// Copied from clang/lib/Headers/opencl-c-base.h
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arsenm wrote:

This shouldn't need copying? Use the builtin included declarations? 

https://github.com/llvm/llvm-project/pull/168318