xref: /freebsd/lib/libc/i386/string/bzero.S (revision 1d386b48a555f61cb7325543adbbb5c3f3407a66)
12ceb2ce9SGarrett Wollman/*
22ceb2ce9SGarrett Wollman * Copyright (c) 1993 Winning Strategies, Inc.
32ceb2ce9SGarrett Wollman * All rights reserved.
42ceb2ce9SGarrett Wollman *
52ceb2ce9SGarrett Wollman * Redistribution and use in source and binary forms, with or without
62ceb2ce9SGarrett Wollman * modification, are permitted provided that the following conditions
72ceb2ce9SGarrett Wollman * are met:
82ceb2ce9SGarrett Wollman * 1. Redistributions of source code must retain the above copyright
92ceb2ce9SGarrett Wollman *    notice, this list of conditions and the following disclaimer.
102ceb2ce9SGarrett Wollman * 2. Redistributions in binary form must reproduce the above copyright
112ceb2ce9SGarrett Wollman *    notice, this list of conditions and the following disclaimer in the
122ceb2ce9SGarrett Wollman *    documentation and/or other materials provided with the distribution.
132ceb2ce9SGarrett Wollman * 3. All advertising materials mentioning features or use of this software
142ceb2ce9SGarrett Wollman *    must display the following acknowledgement:
152ceb2ce9SGarrett Wollman *      This product includes software developed by Winning Strategies, Inc.
162ceb2ce9SGarrett Wollman * 4. The name of the author may not be used to endorse or promote products
1721dc7d4fSJens Schweikhardt *    derived from this software without specific prior written permission
182ceb2ce9SGarrett Wollman *
192ceb2ce9SGarrett Wollman * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
202ceb2ce9SGarrett Wollman * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
212ceb2ce9SGarrett Wollman * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
222ceb2ce9SGarrett Wollman * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
232ceb2ce9SGarrett Wollman * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
242ceb2ce9SGarrett Wollman * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
252ceb2ce9SGarrett Wollman * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
262ceb2ce9SGarrett Wollman * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
272ceb2ce9SGarrett Wollman * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
282ceb2ce9SGarrett Wollman * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
292ceb2ce9SGarrett Wollman */
302ceb2ce9SGarrett Wollman
31e6d808aeSPeter Wemm#include <machine/asm.h>
322ceb2ce9SGarrett Wollman/*
332ceb2ce9SGarrett Wollman * bzero (void *b, size_t len)
342ceb2ce9SGarrett Wollman *	write len zero bytes to the string b.
352ceb2ce9SGarrett Wollman *
362ceb2ce9SGarrett Wollman * Written by:
372ceb2ce9SGarrett Wollman *	J.T. Conklin (jtc@wimsey.com), Winning Strategies, Inc.
382ceb2ce9SGarrett Wollman */
392ceb2ce9SGarrett Wollman
402ceb2ce9SGarrett WollmanENTRY(bzero)
412ceb2ce9SGarrett Wollman	pushl	%edi
422ceb2ce9SGarrett Wollman	pushl	%ebx
432ceb2ce9SGarrett Wollman	movl	12(%esp),%edi
442ceb2ce9SGarrett Wollman	movl	16(%esp),%ecx
452ceb2ce9SGarrett Wollman
462ceb2ce9SGarrett Wollman	cld				/* set fill direction forward */
472ceb2ce9SGarrett Wollman	xorl	%eax,%eax		/* set fill data to 0 */
482ceb2ce9SGarrett Wollman
492ceb2ce9SGarrett Wollman	/*
502ceb2ce9SGarrett Wollman	 * if the string is too short, it's really not worth the overhead
512ceb2ce9SGarrett Wollman	 * of aligning to word boundries, etc.  So we jump to a plain
522ceb2ce9SGarrett Wollman	 * unaligned set.
532ceb2ce9SGarrett Wollman	 */
542ceb2ce9SGarrett Wollman	cmpl	$0x0f,%ecx
552ceb2ce9SGarrett Wollman	jle	L1
562ceb2ce9SGarrett Wollman
572ceb2ce9SGarrett Wollman	movl	%edi,%edx		/* compute misalignment */
582ceb2ce9SGarrett Wollman	negl	%edx
592ceb2ce9SGarrett Wollman	andl	$3,%edx
602ceb2ce9SGarrett Wollman	movl	%ecx,%ebx
612ceb2ce9SGarrett Wollman	subl	%edx,%ebx
622ceb2ce9SGarrett Wollman
632ceb2ce9SGarrett Wollman	movl	%edx,%ecx		/* zero until word aligned */
642ceb2ce9SGarrett Wollman	rep
652ceb2ce9SGarrett Wollman	stosb
662ceb2ce9SGarrett Wollman
672ceb2ce9SGarrett Wollman	movl	%ebx,%ecx		/* zero by words */
682ceb2ce9SGarrett Wollman	shrl	$2,%ecx
692ceb2ce9SGarrett Wollman	rep
702ceb2ce9SGarrett Wollman	stosl
712ceb2ce9SGarrett Wollman
722ceb2ce9SGarrett Wollman	movl	%ebx,%ecx
732ceb2ce9SGarrett Wollman	andl	$3,%ecx			/* zero remainder by bytes */
742ceb2ce9SGarrett WollmanL1:	rep
752ceb2ce9SGarrett Wollman	stosb
762ceb2ce9SGarrett Wollman
772ceb2ce9SGarrett Wollman	popl	%ebx
782ceb2ce9SGarrett Wollman	popl	%edi
792ceb2ce9SGarrett Wollman	ret
80ed820052SPeter WemmEND(bzero)
81*93ab7586SKonstantin Belousov
82*93ab7586SKonstantin Belousov	.section .note.GNU-stack,"",%progbits
83