xref: /netbsd-src/lib/libc/arch/mips/string/bzero.S (revision 42b55ff43aca2f3b38e1d3d6d0d1beabda118045)

/*	$NetBSD: bzero.S,v 1.10 2009/12/14 02:53:52 matt Exp $	*/

/*-
 * Copyright (c) 1991, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Ralph Campbell.
 *
 * 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 <mips/asm.h>

#if defined(LIBC_SCCS) && !defined(lint)
#if 0
	RCSID("from: @(#)bzero.s	8.1 (Berkeley) 6/4/93")
#else
	RCSID("$NetBSD: bzero.S,v 1.10 2009/12/14 02:53:52 matt Exp $")
#endif
#endif /* LIBC_SCCS and not lint */


#define _LOCORE		/* XXX not really, just assembly-code source */
#include <machine/endian.h>

/* bzero(s1, n) */

LEAF(bzero)
	.set	noreorder
	blt		a1, 3*SZREG, smallclr # small amount to clear?
	PTR_SUBU	a3, zero, a0	# compute # bytes to word align address
	and		a3, a3, SZREG-1
	beq		a3, zero, 1f	# skip if word aligned
#if SZREG == 4
	PTR_SUBU	a1, a1, a3	# subtract from remaining count
	SWHI		zero, 0(a0)	# clear 1, 2, or 3 bytes to align
	PTR_ADDU	a0, a0, a3
#endif
#if SZREG == 8
	PTR_SUBU	a1, a1, a3	# subtract from remaining count
	PTR_ADDU	a0, a0, a3	# align dst to next word
	sll		a3, a3, 3	# bits to bytes
	li		a2, -1		# make a mask
#if _BYTE_ORDER == _BIG_ENDIAN
	REG_SRLV	a2, a2, a3	# we want to keep the MSB bytes
#endif
#if _BYTE_ORDER == _LITTLE_ENDIAN
	REG_SLLV	a2, a2, a3	# we want to keep the LSB bytes
#endif
	nor		a2, zero, a2	# complement the mask
	REG_L		v0, -SZREG(a0)	# load the word to partially clear
	and		v0, v0, a2	# clear the bytes
	REG_S		v0, -SZREG(a0)	# store it back
#endif
1:
	and		v0, a1, SZREG-1	# compute number of words left
	PTR_SUBU	a3, a1, v0
	move		a1, v0
	PTR_ADDU	a3, a3, a0	# compute ending address
2:
	PTR_ADDU	a0, a0, SZREG	# clear words
	bne		a0, a3, 2b	#  unrolling loop doesnt help
	REG_S		zero, -SZREG(a0) # since we are limited by memory speed
smallclr:
	ble		a1, zero, 2f
	PTR_ADDU	a3, a1, a0	# compute ending address
1:
	PTR_ADDU	a0, a0, 1	# clear bytes
	bne		a0, a3, 1b
	sb		zero, -1(a0)
2:
	j		ra
	nop
END(bzero)