/*	$NetBSD: bzero.S,v 1.2 2008/04/28 20:22:52 martin Exp $	*/

/*-
 * Copyright (c) 1997 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * This code is derived from software contributed to The NetBSD Foundation
 * by J.T. Conklin.
 *
 * 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.
 */

/*-
 * Copyright (c) 1990 The Regents of the University of California.
 * All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * the Systems Programming Group of the University of Utah Computer
 * Science Department.
 *
 * 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. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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) && !defined(lint)
#if 0
	RCSID("from: @(#)bzero.s	5.1 (Berkeley) 5/12/90")
#else
	RCSID("$NetBSD: bzero.S,v 1.2 2008/04/28 20:22:52 martin Exp $")
#endif
#endif /* LIBC_SCCS and not lint */

ENTRY(bzero)
	movl	%d2,%sp@-
	movl	%sp@(8),%a0		| destination
	movl	%sp@(12),%d1		| count

	movql	#0,%d2

	/* 
	 * It isn't worth the overhead of aligning to {long}word boundries
	 * if the string is too short.
	 */
	cmpl	#8,%d1
	jlt	Lbzbyte

	/* word align */
	movl	%a0,%d0
	btst	#0,%d0			| if (dst & 1)
	jeq	Lbzalgndw		| 
	movb	%d2,%a0@+		| 	*(char *)dst++ = 0
	subql	#1,%d1			|	len--
Lbzalgndw:
	/* long word align */
	btst	#1,%d0			| if (dst & 2)
	jeq	Lbzalgndl		|
	movw	%d2,%a0@+		|	*(short *)dst++ = 0
	subql	#2,%d1			|	len -= 2
Lbzalgndl:
	/* zero by 8 longwords */
	movel	%d1,%d0
	lsrl	#5,%d0			| cnt = len / 32
	jeq	Lbzlong			| if (cnt)
	andl	#31,%d1			|	len %= 32
	subql	#1,%d0			|	set up for dbf
Lbz32loop:
	movl	%d2,%a0@+		|	zero 8 long words
	movl	%d2,%a0@+
	movl	%d2,%a0@+
	movl	%d2,%a0@+
	movl	%d2,%a0@+
	movl	%d2,%a0@+
	movl	%d2,%a0@+
	movl	%d2,%a0@+
	dbf	%d0,Lbz32loop		|	till done
	clrw	%d0
	subql	#1,%d0
	jcc	Lbz32loop

Lbzlong:
	/* copy by longwords */
	movel	%d1,%d0
	lsrl	#2,%d0			| cnt = len / 4
	jeq	Lbzbyte			| if (cnt)
	subql	#1,%d0			|	set up for dbf
Lbzlloop:
	movl	%d2,%a0@+		|	clear longwords
	dbf	%d0,Lbzlloop		|	till done
	andl	#3,%d1			|	len %= 4
	jeq	Lbzdone

	subql	#1,%d1			| set up for dbf
Lbzbloop:
	movb	%d2,%a0@+		| zero bytes
Lbzbyte:
	dbf	%d1,Lbzbloop		| till done
Lbzdone:
	movl	%sp@+,%d2
	rts