Fix implementation of _mm_pause.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@61441 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Headers/emmintrin.h b/lib/Headers/emmintrin.h
index 1232cab..2388065 100644
--- a/lib/Headers/emmintrin.h
+++ b/lib/Headers/emmintrin.h
@@ -1106,7 +1106,7 @@
 
 static inline void __attribute__((__always_inline__)) _mm_pause(void)
 {
-  asm("pause");
+  __asm__ volatile ("pause");
 }
 
 #define _MM_SHUFFLE(x, y) (((x) << 1) | (y))