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RE: [PATCH] Improve memccpy performance
- From: "Wilco Dijkstra" <wdijkstr at arm dot com>
- To: "Richard Earnshaw" <Richard dot Earnshaw at arm dot com>, "'Roland McGrath'" <roland at hack dot frob dot com>
- Cc: <libc-alpha at sourceware dot org>
- Date: Fri, 27 Feb 2015 15:17:18 -0000
- Subject: RE: [PATCH] Improve memccpy performance
- Authentication-results: sourceware.org; auth=none
- References: <001f01d03004$e05abdb0$a1103910$ at com> <20150114181430 dot C9E062C39DB at topped-with-meat dot com> <54B79A67 dot 2010208 at arm dot com>
> Wilco Dijkstra wrote:
> > Richard Earnshaw wrote:
> > On 14/01/15 18:14, Roland McGrath wrote:
> > >> + return memcpy (dest, src, n) + n;
> > >
> > > Use __mempcpy here.
> > >
> > That will be worse if mempcpy just calls memcpy; which is what the C
> > library implementation does.
>
> If GLIBC inlines mempcpy like I proposed then it would be reasonable
> to use mempcpy here as it results in exactly the same code.
So, OK for trunk with __mempcpy like below?
---
string/memccpy.c | 14 +++++++-------
1 file changed, 7 insertions(+), 7 deletions(-)
diff --git a/string/memccpy.c b/string/memccpy.c
index 70ee2ae..d4146f9 100644
--- a/string/memccpy.c
+++ b/string/memccpy.c
@@ -26,15 +26,15 @@
void *
__memccpy (void *dest, const void *src, int c, size_t n)
{
- const char *s = src;
- char *d = dest;
- const char x = c;
- size_t i = n;
+ void *p = memchr (src, c, n);
- while (i-- > 0)
- if ((*d++ = *s++) == x)
- return d;
+ if (p != NULL)
+ {
+ n = p - src + 1;
+ return __mempcpy (dest, src, n);
+ }
+ memcpy (dest, src, n);
return NULL;
}
--
1.9.1