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Re: [PATCH] Improve stpncpy performance
- From: OndÅej BÃlka <neleai at seznam dot cz>
- To: Wilco Dijkstra <wdijkstr at arm dot com>
- Cc: libc-alpha at sourceware dot org
- Date: Tue, 16 Jun 2015 13:13:10 +0200
- Subject: Re: [PATCH] Improve stpncpy performance
- Authentication-results: sourceware.org; auth=none
- References: <000401d07778$390823c0$ab186b40$ at com> <20150512092317 dot GB27121 at domone>
Same case as strncpy.
On Tue, May 12, 2015 at 11:23:17AM +0200, OndÅej BÃlka wrote:
> On Wed, Apr 15, 2015 at 01:32:22PM +0100, Wilco Dijkstra wrote:
> > ping
> >
> ok for me.
> > > > -----Original Message-----
> > > > From: Wilco Dijkstra [mailto:wdijkstr@arm.com]
> > > > Sent: 12 January 2015 15:09
> > > > To: 'libc-alpha@sourceware.org'
> > > > Subject: [PATCH] Improve stpncpy performance
> > > >
> > > > Like strncpy, this patch improves stpncpy performance by using strnlen/memcpy/memset rather
> > > > than a byte loop. Performance on bench-stpncpy is ~2x faster on average.
> > > >
> > > > ChangeLog:
> > > >
> > > > 2015-01-12 Wilco Dijkstra wdijkstr@arm.com
> > > >
> > > > * string/stpncpy.c (stpncpy): Improve performance using
> > > > __strnlen/memcpy/memset.
> > > >
> > > > ---
> > > > string/stpncpy.c | 59 ++++++--------------------------------------------------
> > > > 1 file changed, 6 insertions(+), 53 deletions(-)
> > > >
> > > > diff --git a/string/stpncpy.c b/string/stpncpy.c
> > > > index fad747e..50521aa 100644
> > > > --- a/string/stpncpy.c
> > > > +++ b/string/stpncpy.c
> > > > @@ -15,7 +15,7 @@
> > > > License along with the GNU C Library; if not, see
> > > > <http://www.gnu.org/licenses/>. */
> > > >
> > > > -/* This is almost copied from strncpy.c, written by Torbjorn Granlund. */
> > > > +#include <stddef.h>
> > > >
> > > > #ifdef HAVE_CONFIG_H
> > > > # include <config.h>
> > > > @@ -41,59 +41,12 @@ weak_alias (__stpncpy, stpncpy)
> > > > char *
> > > > STPNCPY (char *dest, const char *src, size_t n)
> > > > {
> > > > - char c;
> > > > - char *s = dest;
> > > > -
> > > > - if (n >= 4)
> > > > - {
> > > > - size_t n4 = n >> 2;
> > > > -
> > > > - for (;;)
> > > > - {
> > > > - c = *src++;
> > > > - *dest++ = c;
> > > > - if (c == '\0')
> > > > - break;
> > > > - c = *src++;
> > > > - *dest++ = c;
> > > > - if (c == '\0')
> > > > - break;
> > > > - c = *src++;
> > > > - *dest++ = c;
> > > > - if (c == '\0')
> > > > - break;
> > > > - c = *src++;
> > > > - *dest++ = c;
> > > > - if (c == '\0')
> > > > - break;
> > > > - if (--n4 == 0)
> > > > - goto last_chars;
> > > > - }
> > > > - n -= dest - s;
> > > > - goto zero_fill;
> > > > - }
> > > > -
> > > > - last_chars:
> > > > - n &= 3;
> > > > - if (n == 0)
> > > > + size_t size = __strnlen (src, n);
> > > > + memcpy (dest, src, size);
> > > > + dest += size;
> > > > + if (size == n)
> > > > return dest;
> > > > -
> > > > - for (;;)
> > > > - {
> > > > - c = *src++;
> > > > - --n;
> > > > - *dest++ = c;
> > > > - if (c == '\0')
> > > > - break;
> > > > - if (n == 0)
> > > > - return dest;
> > > > - }
> > > > -
> > > > - zero_fill:
> > > > - while (n-- > 0)
> > > > - dest[n] = '\0';
> > > > -
> > > > - return dest - 1;
> > > > + return memset (dest, '\0', n - size);
> > > > }
> > > > #ifdef weak_alias
> > > > libc_hidden_def (__stpncpy)
> > > > --
> > > > 1.9.1
> >
>
> --
>
> A plumber is needed, the network drain is clogged
--
Telecommunications is downgrading.