libgo patch committed: Use _mm_pause rather than __builtin_ia32_pause

[Ian Lance Taylor]

This patch based on one by Peter Collingbourne changes libgo to use the
somewhat portable _mm_pause intrinsic rather than the GCC-specific
__builtin_ia32_pause builtin function.  This makes it easier to compile
libgo with compilers other than GCC.  Bootstrapped and ran Go testsuite
on x86_64-unknown-linux-gnu.  Committed to mainline.

Ian


diff -r 4d88292e0727 libgo/runtime/yield.c
--- a/libgo/runtime/yield.c	Thu May 29 13:21:58 2014 -0700
+++ b/libgo/runtime/yield.c	Fri May 30 06:51:16 2014 -0700
@@ -14,6 +14,10 @@
 #include <sys/select.h>
 #endif
 
+#if defined (__i386__) || defined (__x86_64__)
+#include <xmmintrin.h>
+#endif
+
 #include "runtime.h"
 
 /* Spin wait.  */
@@ -26,7 +30,7 @@
   for (i = 0; i < cnt; ++i)
     {
 #if defined (__i386__) || defined (__x86_64__)
-      __builtin_ia32_pause ();
+      _mm_pause ();
 #endif
     }
 }