1/* $NetBSD: memset.S,v 1.3 2007/11/12 18:41:59 ad Exp $ */ 2 3/*- 4 * Copyright (c) 2003 The NetBSD Foundation, Inc. 5 * All rights reserved. 6 * 7 * This code is derived from software contributed to The NetBSD Foundation 8 * by David Laight. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 3. Neither the name of The NetBSD Foundation nor the names of its 19 * contributors may be used to endorse or promote products derived 20 * from this software without specific prior written permission. 21 * 22 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 23 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 24 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 25 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 26 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 27 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 28 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 29 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 30 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 31 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 32 * POSSIBILITY OF SUCH DAMAGE. 33 */ 34 35#include <machine/asm.h> 36 37#if defined(LIBC_SCCS) 38 RCSID("$NetBSD: memset.S,v 1.3 2007/11/12 18:41:59 ad Exp $") 39#endif 40 41#ifdef BZERO 42ENTRY(bzero) 43#else 44ENTRY(memset) 45#endif 46#ifdef BZERO 47 movl 8(%esp),%ecx 48 xor %eax,%eax 49#else 50 movl 12(%esp),%ecx 51 movzbl 8(%esp),%eax /* unsigned char, zero extend */ 52#endif 53 cmpl $0x0f,%ecx /* avoid mispredicted branch... */ 54 55 pushl %edi 56 movl 8(%esp),%edi 57 58 /* 59 * if the string is too short, it's really not worth the overhead 60 * of aligning to word boundries, etc. So we jump to a plain 61 * unaligned set. 62 * 63 * NB aligning the transfer is actually pointless on my athlon 700, 64 * It does make a difference to a PII though. 65 * 66 * The PII, PIII and PIV all seem to have a massive performance 67 * drop when the initial target address is an odd multiple of 4. 68 */ 69 jbe .Lby_bytes 70 71#ifndef BZERO 72 movb %al,%ah /* copy char to all bytes in word */ 73 movl %eax,%edx 74 sall $16,%eax 75 orl %edx,%eax 76#endif 77 78 movl %edi,%edx /* detect misalignment */ 79 neg %edx 80 andl $7,%edx 81 jnz .Lalign 82.Laligned: 83 movl %eax,-4(%edi,%ecx) /* zap last 4 bytes */ 84 shrl $2,%ecx /* zero by words */ 85 rep 86 stosl 87.Ldone: 88#ifndef BZERO 89 movl 8(%esp),%eax /* return address of buffer */ 90#endif 91 pop %edi 92 ret 93 94.Lalign: 95 movl %eax,(%edi) /* zap first 8 bytes */ 96 movl %eax,4(%edi) 97 subl %edx,%ecx /* remove from main count */ 98 add %edx,%edi 99 jmp .Laligned 100 101.Lby_bytes: 102 rep 103 stosb 104 105#ifndef BZERO 106 movl 8(%esp),%eax /* return address of buffer */ 107#endif 108 popl %edi 109 ret 110