glibc/sysdeps/i386/i486/strlen.S
Roland McGrath 8f5ca04bc7 Sat Oct 14 02:52:36 1995 Ulrich Drepper <drepper@ipd.info.uni-karlsruhe.de>
* malloc/malloc.c (_malloc_internal): Performance fix.  Move
	if statement out of loop.

	* stdio/_itoa.c, stdio/_itoa.h: Complete rewrite.  Much faster
	implementation using GMP functions.  Contributed by
	Torbjorn Granlund and Ulrich Drepper.

	* stdio/test_rdwr.c: Include <errno.h>.

	* sysdeps/i386/i586/Implies: New file.

	New highly optimized string functions for i[345]86.
	* sysdeps/i386/memchr.S, sysdeps/i386/memcmp.S: New files.
        * sysdeps/i386/stpcpy.S, sysdeps/i386/stpncpy.S: New files.
        * sysdeps/i386/strchr.S, sysdeps/i386/strcspn.S: New files.
        * sysdeps/i386/strpbrk.S, sysdeps/i386/strrchr.S: New files.
        * sysdeps/i386/strspn.S, sysdeps/i386/i486/strcat.S: New files.
        * sysdeps/i386/i486/strlen.S, sysdeps/i386/i586/strchr.S: New files.
        * sysdeps/i386/i586/strlen.S: New file.
	* sysdeps/i386/memchr.c: Removed.  There is now an assembler version.

	* sysdeps/i386/i586/memcopy.h (WORD_COPY_BWD): Parameters did
	not correspond to used values.

	* sysdeps/unix/sysv/linux/nfs/nfs.h: New file.  Simply a wrapper
        around a kernel header file.
	* sysdeps/unix/sysv/linux/Dist: Add it.
	* sysdeps/unix/sysv/linux/Makefile [$(subdir)=sunrpc] (headers):
	Likewise.

	* sysdeps/unix/sysv/linux/local_lim.h: Rewrite.  Instead of
        defining ourself we use a kernel header file.

	* sysdeps/unix/sysv/linux/i386/sysdep.h (DO_CALL): Optimize system
        call handler for i586.

	* sysdeps/unix/sysv/linux/sys/param.h: Add copyright and clean up.
Sat Oct 14 02:52:36 1995  Ulrich Drepper  <drepper@ipd.info.uni-karlsruhe.de>

	* malloc/malloc.c (_malloc_internal): Performance fix.  Move
	if statement out of loop.

	* stdio/_itoa.c, stdio/_itoa.h: Complete rewrite.  Much faster
	implementation using GMP functions.  Contributed by
	Torbjorn Granlund and Ulrich Drepper.

	* stdio/test_rdwr.c: Include <errno.h>.

	* sysdeps/i386/i586/Implies: New file.

	New highly optimized string functions for i[345]86.
	* sysdeps/i386/memchr.S, sysdeps/i386/memcmp.S: New files.
        * sysdeps/i386/stpcpy.S, sysdeps/i386/stpncpy.S: New files.
        * sysdeps/i386/strchr.S, sysdeps/i386/strcspn.S: New files.
        * sysdeps/i386/strpbrk.S, sysdeps/i386/strrchr.S: New files.
        * sysdeps/i386/strspn.S, sysdeps/i386/i486/strcat.S: New files.
        * sysdeps/i386/i486/strlen.S, sysdeps/i386/i586/strchr.S: New files.
        * sysdeps/i386/i586/strlen.S: New file.
	* sysdeps/i386/memchr.c: Removed.  There is now an assembler version.

	* sysdeps/i386/i586/memcopy.h (WORD_COPY_BWD): Parameters did
	not correspond to used values.

	* sysdeps/unix/sysv/linux/nfs/nfs.h: New file.  Simply a wrapper
        around a kernel header file.
	* sysdeps/unix/sysv/linux/Dist: Add it.
	* sysdeps/unix/sysv/linux/Makefile [$(subdir)=sunrpc] (headers):
	Likewise.

	* sysdeps/unix/sysv/linux/local_lim.h: Rewrite.  Instead of
        defining ourself we use a kernel header file.

	* sysdeps/unix/sysv/linux/i386/sysdep.h (DO_CALL): Optimize system
        call handler for i586.

	* sysdeps/unix/sysv/linux/sys/param.h: Add copyright and clean up.
1995-10-16 01:37:51 +00:00

133 lines
4.8 KiB
ArmAsm

/* strlen(str) -- determine the length of the string STR.
Optimized for Intel 80x86, x>=4.
Copyright (C) 1991, 1992, 1993, 1994, 1995 Free Software Foundation, Inc.
Contributed by Ulrich Drepper <drepper@gnu.ai.mit.edu>.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Library General Public License for more details.
You should have received a copy of the GNU Library General Public
License along with the GNU C Library; see the file COPYING.LIB. If
not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA. */
#include <sysdep.h>
#include "asm-syntax.h"
/*
INPUT PARAMETERS:
str (sp + 4)
*/
.text
ENTRY (strlen)
movl 4(%esp), %ecx /* get string pointer */
movl %ecx, %eax /* duplicate it */
andl $3, %ecx /* mask alignment bits */
jz L1 /* aligned => start loop */
cmpb %ch, (%eax) /* is byte NUL? */
je L2 /* yes => return */
incl %eax /* increment pointer */
xorl $3, %ecx /* was alignment = 3? */
jz L1 /* yes => now it is aligned and start loop */
cmpb %ch, (%eax) /* is byte NUL? */
je L2 /* yes => return */
addl $1, %eax /* increment pointer */
subl $1, %ecx /* was alignment = 2? */
jz L1 /* yes => now it is aligned and start loop */
cmpb %ch, (%eax) /* is byte NUL? */
je L2 /* yes => return */
/* Don't change the above `addl $1,%eax' and `subl $1, %ecx' into `incl %eax'
and `decl %ecx' resp. The additional two byte per instruction make the
label 4 to be aligned on a 16 byte boundary with nops.
The following `sub $15, %eax' is part of this trick, too. Together with
the next instruction (`addl $16, %eax') it is in fact a `incl %eax', just
as expected from the algorithm. But doing so has the advantage that
no jump to label 1 is necessary and so the pipeline is not flushed. */
subl $15, %eax /* effectively +1 */
L4: addl $16, %eax /* adjust pointer for full loop */
L1: movl (%eax), %ecx /* get word (= 4 bytes) in question */
movl $0xfefefeff, %edx /* magic value */
addl %ecx, %edx /* add the magic value to the word. We get
carry bits reported for each byte which
is *not* 0 */
jnc L3 /* highest byte is NUL => return pointer */
xorl %ecx, %edx /* (word+magic)^word */
orl $0xfefefeff, %edx /* set all non-carry bits */
incl %edx /* add 1: if one carry bit was *not* set
the addition will not result in 0. */
jnz L3 /* found NUL => return pointer */
movl 4(%eax), %ecx /* get word (= 4 bytes) in question */
movl $0xfefefeff, %edx /* magic value */
addl %ecx, %edx /* add the magic value to the word. We get
carry bits reported for each byte which
is *not* 0 */
jnc L5 /* highest byte is NUL => return pointer */
xorl %ecx, %edx /* (word+magic)^word */
orl $0xfefefeff, %edx /* set all non-carry bits */
incl %edx /* add 1: if one carry bit was *not* set
the addition will not result in 0. */
jnz L5 /* found NUL => return pointer */
movl 8(%eax), %ecx /* get word (= 4 bytes) in question */
movl $0xfefefeff, %edx /* magic value */
addl %ecx, %edx /* add the magic value to the word. We get
carry bits reported for each byte which
is *not* 0 */
jnc L6 /* highest byte is NUL => return pointer */
xorl %ecx, %edx /* (word+magic)^word */
orl $0xfefefeff, %edx /* set all non-carry bits */
incl %edx /* add 1: if one carry bit was *not* set
the addition will not result in 0. */
jnz L6 /* found NUL => return pointer */
movl 12(%eax), %ecx /* get word (= 4 bytes) in question */
movl $0xfefefeff, %edx /* magic value */
addl %ecx, %edx /* add the magic value to the word. We get
carry bits reported for each byte which
is *not* 0 */
jnc L7 /* highest byte is NUL => return pointer */
xorl %ecx, %edx /* (word+magic)^word */
orl $0xfefefeff, %edx /* set all non-carry bits */
incl %edx /* add 1: if one carry bit was *not* set
the addition will not result in 0. */
jz L4 /* no NUL found => continue loop */
L7: addl $4, %eax /* adjust pointer */
L6: addl $4, %eax
L5: addl $4, %eax
L3: testb %cl, %cl /* is first byte NUL? */
jz L2 /* yes => return */
incl %eax /* increment pointer */
testb %ch, %ch /* is second byte NUL? */
jz L2 /* yes => return */
incl %eax /* increment pointer */
testl $0xff0000, %ecx /* is third byte NUL? */
jz L2 /* yes => return pointer */
incl %eax /* increment pointer */
L2: subl 4(%esp), %eax /* compute difference to string start */
ret