Import prebuilt clang toolchain for linux.
diff --git a/linux-x64/clang/include/llvm/Support/Atomic.h b/linux-x64/clang/include/llvm/Support/Atomic.h
new file mode 100644
index 0000000..552313f
--- /dev/null
+++ b/linux-x64/clang/include/llvm/Support/Atomic.h
@@ -0,0 +1,43 @@
+//===- llvm/Support/Atomic.h - Atomic Operations -----------------*- C++ -*-===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file declares the llvm::sys atomic operations.
+//
+// DO NOT USE IN NEW CODE!
+//
+// New code should always rely on the std::atomic facilities in C++11.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_SUPPORT_ATOMIC_H
+#define LLVM_SUPPORT_ATOMIC_H
+
+#include "llvm/Support/DataTypes.h"
+
+// Windows will at times define MemoryFence.
+#ifdef MemoryFence
+#undef MemoryFence
+#endif
+
+namespace llvm {
+ namespace sys {
+ void MemoryFence();
+
+#ifdef _MSC_VER
+ typedef long cas_flag;
+#else
+ typedef uint32_t cas_flag;
+#endif
+ cas_flag CompareAndSwap(volatile cas_flag* ptr,
+ cas_flag new_value,
+ cas_flag old_value);
+ }
+}
+
+#endif