Add Intel intrinsics headers

third_party/intel/xtestintrin.internal.h

@@ -0,0 +1,25 @@
+#ifndef _IMMINTRIN_H_INCLUDED
+#error "Never use <xtestintrin.h> directly; include <immintrin.h> instead."
+#endif
+
+#ifndef _XTESTINTRIN_H_INCLUDED
+#define _XTESTINTRIN_H_INCLUDED
+
+#ifndef __RTM__
+#pragma GCC push_options
+#pragma GCC target("rtm")
+#define __DISABLE_RTM__
+#endif /* __RTM__ */
+
+extern __inline int
+    __attribute__((__gnu_inline__, __always_inline__, __artificial__))
+    _xtest(void) {
+  return __builtin_ia32_xtest();
+}
+
+#ifdef __DISABLE_RTM__
+#undef __DISABLE_RTM__
+#pragma GCC pop_options
+#endif /* __DISABLE_RTM__ */
+
+#endif /* _XTESTINTRIN_H_INCLUDED */