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bzero.S revision 1.1 
      1 /*-
      2  * Copyright (c) 1991, 1993
      3  *	The Regents of the University of California.  All rights reserved.
      4  *
      5  * This code is derived from software contributed to Berkeley by
      6  * Ralph Campbell.
      7  *
      8  * Redistribution and use in source and binary forms, with or without
      9  * modification, are permitted provided that the following conditions
     10  * are met:
     11  * 1. Redistributions of source code must retain the above copyright
     12  *    notice, this list of conditions and the following disclaimer.
     13  * 2. Redistributions in binary form must reproduce the above copyright
     14  *    notice, this list of conditions and the following disclaimer in the
     15  *    documentation and/or other materials provided with the distribution.
     16  * 3. All advertising materials mentioning features or use of this software
     17  *    must display the following acknowledgement:
     18  *	This product includes software developed by the University of
     19  *	California, Berkeley and its contributors.
     20  * 4. Neither the name of the University nor the names of its contributors
     21  *    may be used to endorse or promote products derived from this software
     22  *    without specific prior written permission.
     23  *
     24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     34  * SUCH DAMAGE.
     35  */
     36 
     37 #include <machine/machAsmDefs.h>
     38 
     39 #if defined(LIBC_SCCS) && !defined(lint)
     40 	ASMSTR("from: @(#)bzero.s	8.1 (Berkeley) 6/4/93")
     41 	ASMSTR("$Id: bzero.S,v 1.1 1994/05/24 07:12:50 glass Exp $")
     42 #endif /* LIBC_SCCS and not lint */
     43 
     44 /* bzero(s1, n) */
     45 
     46 LEAF(bzero)
     47 	.set	noreorder
     48 	blt	a1, 12, smallclr	# small amount to clear?
     49 	subu	a3, zero, a0		# compute # bytes to word align address
     50 	and	a3, a3, 3
     51 	beq	a3, zero, 1f		# skip if word aligned
     52 	subu	a1, a1, a3		# subtract from remaining count
     53 	swr	zero, 0(a0)		# clear 1, 2, or 3 bytes to align
     54 	addu	a0, a0, a3
     55 1:
     56 	and	v0, a1, 3		# compute number of words left
     57 	subu	a3, a1, v0
     58 	move	a1, v0
     59 	addu	a3, a3, a0		# compute ending address
     60 2:
     61 	addu	a0, a0, 4		# clear words
     62 	bne	a0, a3, 2b		#   unrolling loop doesnt help
     63 	sw	zero, -4(a0)		#   since we are limited by memory speed
     64 smallclr:
     65 	ble	a1, zero, 2f
     66 	addu	a3, a1, a0		# compute ending address
     67 1:
     68 	addu	a0, a0, 1		# clear bytes
     69 	bne	a0, a3, 1b
     70 	sb	zero, -1(a0)
     71 2:
     72 	j	ra
     73 	nop
     74 END(bzero)
     75