x86: Add macros to implement ifunce selection in C

These macros are used to implement ifunc selection in C.  To implement
an ifunc function, foo, which returns the address of __foo_sse2 or
__foo_avx2:

   __foo_avx2:

   #define foo __redirect_foo
   #define __foo __redirect___foo
   #include <foo.h>
   #undef foo
   #undef __foo
   #define SYMBOL_NAME foo
   #include <init-arch.h>

   extern __typeof (REDIRECT_NAME) OPTIMIZE (sse2) attribute_hidden;
   extern __typeof (REDIRECT_NAME) OPTIMIZE (avx2) attribute_hidden;

   static inline void *
   foo_selector (void)
   {
     if (use AVX2)
      return OPTIMIZE (avx2);

     return OPTIMIZE (sse2);
   }

   libc_ifunc_redirected (__redirect_foo, foo, foo_selector ());

	* sysdeps/x86/init-arch.h (PASTER1): New.
	(EVALUATOR1): Likewise.
	(PASTER2): Likewise.
	(EVALUATOR2): Likewise.
	(REDIRECT_NAME): Likewise.
	(OPTIMIZE): Likewise.
	(IFUNC_SELECTOR): Likewise.

1 files changed, 11 insertions, 0 deletions

diff --git a/ChangeLog b/ChangeLog
index 5a70bf18e2..0ebfcf9f9b 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,14 @@
+2017-06-05  Adhemerval Zanella  <adhemerval.zanella@linaro.org>
+	    H.J. Lu  <hongjiu.lu@intel.com>
+
+	* sysdeps/x86/init-arch.h (PASTER1): New.
+	(EVALUATOR1): Likewise.
+	(PASTER2): Likewise.
+	(EVALUATOR2): Likewise.
+	(REDIRECT_NAME): Likewise.
+	(OPTIMIZE): Likewise.
+	(IFUNC_SELECTOR): Likewise.
+
 2017-06-05  H.J. Lu  <hongjiu.lu@intel.com>
 
 	* sysdeps/x86_64/strlen.S (PMINU): New.