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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: Wed, 15 Apr 2015 13:31:30 +0100
- 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>
ping
> Wilco Dijkstra wrote:
> > 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