+// RTTI may not be enabled for this compilation unit.
+#if defined(__GXX_RTTI) || defined(__cpp_rtti) || \
+ (defined(_MSC_VER) && defined(_CPPRTTI))
+# define FOLLY_HAS_RTTI 1
+#endif
+
+#ifdef _MSC_VER
+# include <intrin.h>
+#endif
+
+namespace folly {
+
+inline void asm_volatile_pause() {
+#if defined(_MSC_VER) && (defined(_M_IX86) || defined(_M_X64))
+ ::_mm_pause();
+#elif defined(__i386__) || FOLLY_X64
+ asm volatile ("pause");
+#elif FOLLY_A64
+ asm volatile ("wfe");
+#endif
+}
+inline void asm_pause() {
+#if defined(_MSC_VER) && (defined(_M_IX86) || defined(_M_X64))
+ ::_mm_pause();
+#elif defined(__i386__) || FOLLY_X64
+ asm ("pause");
+#elif FOLLY_A64
+ asm ("wfe");
+#endif
+}
+
+}
+