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[v2] Do not transform strchr into rawmemchr

Message ID AM5PR0802MB2610436B25330FAF7A3F017883B70@AM5PR0802MB2610.eurprd08.prod.outlook.com
State Superseded
Headers show

Commit Message

Wilco Dijkstra Nov. 23, 2016, 5:19 p.m. UTC
Version 2 of the patch removes the strchr define completely as
suggested:

GLIBC uses strchr (s, '\0') as an idiom to find the end of a string.
This is transformed into rawmemchr by the bits/string2.h header.
However this is generally slower than strlen on most targets, even when
an optimized rawmemchr implementation exists.  Since GCC7 optimizes
strchr (s, '\0') to strlen (s) + s, the GLIBC headers should not
transform this to rawmemchr.  As GCC recognizes strchr as a builtin,
defining strchr as the builtin is not useful.

Regress passes, OK for commit?

ChangeLog:
2015-11-23  Wilco Dijkstra  <wdijkstr@arm.com>

	* string/bits/string2.h (strchr): Remove define.
--

Comments

Florian Weimer Nov. 24, 2016, 2:24 p.m. UTC | #1
On 11/23/2016 06:19 PM, Wilco Dijkstra wrote:

> -#ifndef _HAVE_STRING_ARCH_strchr

Please post a version which removes the definition of 
_HAVE_STRING_ARCH_strchr as well.

Thanks,
Florian
Wilco Dijkstra Dec. 13, 2016, 12:58 p.m. UTC | #2
Florian Weimer wrote:
> Please post a version which removes the definition of
> _HAVE_STRING_ARCH_strchr as well.

See https://sourceware.org/ml/libc-alpha/2016-11/msg00853.html
which removes all of the redundant STRING_ARCH defines.

Wilco
diff mbox

Patch

diff --git a/string/bits/string2.h b/string/bits/string2.h
index e39d4f1a85c25a4f47418e6a5613b27177ca6cbb..de426b47cae09933b2dc53e0956d63b4c93aebc0 100644
--- a/string/bits/string2.h
+++ b/string/bits/string2.h
@@ -58,16 +58,6 @@ 
 #endif
 
 
-#ifndef _HAVE_STRING_ARCH_strchr
-extern void *__rawmemchr (const void *__s, int __c);
-#  define strchr(s, c) \
-  (__extension__ (__builtin_constant_p (c) && !__builtin_constant_p (s)	      \
-		  && (c) == '\0'					      \
-		  ? (char *) __rawmemchr (s, c)				      \
-		  : __builtin_strchr (s, c)))
-#endif
-
-
 /* Copy SRC to DEST, returning pointer to final NUL byte.  */
 #ifdef __USE_GNU
 # ifndef _HAVE_STRING_ARCH_stpcpy