Use strspn/strcspn/strpbrk ifunc in internal calls.

To make a strtok faster and improve performance in general we need to do one
additional change.

A comment:

/* It doesn't make sense to send libc-internal strcspn calls through a PLT.
   The speedup we get from using SSE4.2 instruction is likely eaten away
   by the indirect call in the PLT.  */

Does not make sense at all because nobody bothered to check it. Gap
between these implementations is quite big, when haystack is empty a
sse2 is around 40 cycles slower because it needs to populate a lookup
table and difference only increases with size. That is much bigger than
plt slowdown which is few cycles.

Even benchtest show a gap which also may be reverse by branch
misprediction but my internal benchmark shown.

 simple_strspn stupid_strspn __strspn_sse42  __strspn_sse2
Length    0, alignment  0, acc len  6:  18.6562 35.2344 17.0469 61.6719
Length    6, alignment  0, acc len  6:  59.5469 72.5781 16.4219 73.625

This patch also handles strpbrk which is implemented by including a
x86_64/multiarch/strcspn.S file.

	* sysdeps/x86_64/multiarch/strspn.S: Remove plt indirection.
	* sysdeps/x86_64/multiarch/strcspn.S: Likewise.

1 files changed, 5 insertions, 0 deletions

diff --git a/ChangeLog b/ChangeLog
index 85234b3559..f2f2447d22 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2015-05-12  Ondřej Bílka  <neleai@seznam.cz>
+
+	* sysdeps/x86_64/multiarch/strcspn.S: Remove plt indirection.
+	* sysdeps/x86_64/multiarch/strspn.S: Likewise.
+
 2015-05-12  Roland McGrath  <roland@hack.frob.com>
 
 	* posix/uname-values.h: New file.