minix/common/lib/libc/arch/i386/string/memset.S

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/* $NetBSD: memset.S,v 1.4 2008/04/29 06:53:01 martin Exp $ */
/*-
* Copyright (c) 2003 The NetBSD Foundation, Inc.
* All rights reserved.
*
* This code is derived from software contributed to The NetBSD Foundation
* by David Laight.
*
* 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.
*
* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
* ``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 FOUNDATION OR CONTRIBUTORS
* 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>
#if defined(LIBC_SCCS)
RCSID("$NetBSD: memset.S,v 1.4 2008/04/29 06:53:01 martin Exp $")
#endif
#ifdef BZERO
ENTRY(bzero)
#else
ENTRY(memset)
#endif
#ifdef BZERO
movl 8(%esp),%ecx
xor %eax,%eax
#else
movl 12(%esp),%ecx
movzbl 8(%esp),%eax /* unsigned char, zero extend */
#endif
cmpl $0x0f,%ecx /* avoid mispredicted branch... */
pushl %edi
movl 8(%esp),%edi
/*
* if the string is too short, it's really not worth the overhead
* of aligning to word boundries, etc. So we jump to a plain
* unaligned set.
*
* NB aligning the transfer is actually pointless on my athlon 700,
* It does make a difference to a PII though.
*
* The PII, PIII and PIV all seem to have a massive performance
* drop when the initial target address is an odd multiple of 4.
*/
jbe .Lby_bytes
#ifndef BZERO
movb %al,%ah /* copy char to all bytes in word */
movl %eax,%edx
sall $16,%eax
orl %edx,%eax
#endif
movl %edi,%edx /* detect misalignment */
neg %edx
andl $7,%edx
jnz .Lalign
.Laligned:
movl %eax,-4(%edi,%ecx) /* zap last 4 bytes */
shrl $2,%ecx /* zero by words */
rep
stosl
.Ldone:
#ifndef BZERO
movl 8(%esp),%eax /* return address of buffer */
#endif
pop %edi
ret
.Lalign:
movl %eax,(%edi) /* zap first 8 bytes */
movl %eax,4(%edi)
subl %edx,%ecx /* remove from main count */
add %edx,%edi
jmp .Laligned
.Lby_bytes:
rep
stosb
#ifndef BZERO
movl 8(%esp),%eax /* return address of buffer */
#endif
popl %edi
ret