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libc: Remove the i386 assembler version of strlen(3).

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On anything modern, the C version, which processes a word at a time, is much
faster. The Intel optimization manual explicitly warns against using REP
prefixes with SCAS or CMPS, which is exactly what the assembler version
does.

A simple test on a Phenom II showed the C version, compiled with -O2, to be
about twice as fast determining the length of 100000 strings between 0 and
255 bytes long.

MFC after:	2 weeks
This commit is contained in:
Jilles Tjoelker 2010-10-01 13:10:11 +00:00
parent 544794507a
commit 220856f376
2 changed files with 1 additions and 55 deletions
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2
lib/libc/i386/string/Makefile.inc
View file

@ -3,5 +3,5 @@
MDSRCS+=bcmp.S bcopy.S bzero.S ffs.S index.S memchr.S memcmp.S memcpy.S \
memmove.S memset.S rindex.S strcat.S strchr.S strcmp.S strcpy.S \
strlen.S strncmp.S strrchr.S swab.S wcschr.S wcscmp.S wcslen.S \
strncmp.S strrchr.S swab.S wcschr.S wcscmp.S wcslen.S \
wmemchr.S

54
lib/libc/i386/string/strlen.S
View file

@ -1,54 +0,0 @@
/*
* Copyright (c) 1993 Winning Strategies, Inc.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by Winning Strategies, Inc.
* 4. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include <machine/asm.h>
__FBSDID("$FreeBSD$");
/*
* strlen (s)
* compute the length of the string s.
*
* Written by:
* J.T. Conklin (jtc@wimsey.com), Winning Strategies, Inc.
*/
ENTRY(strlen)
pushl %edi
movl 8(%esp),%edi /* string address */
cld /* set search forward */
xorl %eax,%eax /* set search for null terminator */
movl $-1,%ecx /* set search for lots of characters */
repne /* search! */
scasb
notl %ecx /* get length by taking complement */
leal -1(%ecx),%eax /* and subtracting one */
popl %edi
ret
END(strlen)