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bcmp.S revision 1.4 
      1 /*	$NetBSD: bcmp.S,v 1.4 1996/09/16 18:11:17 jonathan Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 1991, 1993
      5  *	The Regents of the University of California.  All rights reserved.
      6  *
      7  * This code is derived from software contributed to Berkeley by
      8  * Ralph Campbell.
      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. All advertising materials mentioning features or use of this software
     19  *    must display the following acknowledgement:
     20  *	This product includes software developed by the University of
     21  *	California, Berkeley and its contributors.
     22  * 4. Neither the name of the University nor the names of its contributors
     23  *    may be used to endorse or promote products derived from this software
     24  *    without specific prior written permission.
     25  *
     26  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     27  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     28  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     29  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     30  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     31  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     32  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     33  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     34  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     35  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     36  * SUCH DAMAGE.
     37  */
     38 
     39 #include <machine/machAsmDefs.h>
     40 
     41 #if defined(LIBC_SCCS) && !defined(lint)
     42 	ASMSTR("from: @(#)bcmp.s	8.1 (Berkeley) 6/4/93")
     43 	ASMSTR("$NetBSD: bcmp.S,v 1.4 1996/09/16 18:11:17 jonathan Exp $")
     44 #endif /* LIBC_SCCS and not lint */
     45 
     46 /* bcmp(s1, s2, n) */
     47 
     48 #ifdef MIPSEL
     49 #	define	LWHI	lwr
     50 #	define	LWLO	lwl
     51 #	define	SWHI	swr
     52 #	define	SWLO	swl
     53 #endif
     54 #ifdef MIPSEB
     55 #	define	LWHI	lwl
     56 #	define	LWLO	lwr
     57 #	define	SWHI	swl
     58 #	define	SWLO	swr
     59 #endif
     60 
     61 LEAF(bcmp)
     62 	.set	noreorder
     63 	blt	a2, 16, small		# is it worth any trouble?
     64 	xor	v0, a0, a1		# compare low two bits of addresses
     65 	and	v0, v0, 3
     66 	subu	a3, zero, a1		# compute # bytes to word align address
     67 	bne	v0, zero, unaligned	# not possible to align addresses
     68 	and	a3, a3, 3
     69 
     70 	beq	a3, zero, 1f
     71 	subu	a2, a2, a3		# subtract from remaining count
     72 	move	v0, v1			# init v0,v1 so unmodified bytes match
     73 	LWHI	v0, 0(a0)		# read 1, 2, or 3 bytes
     74 	LWHI	v1, 0(a1)
     75 	addu	a1, a1, a3
     76 	bne	v0, v1, nomatch
     77 	addu	a0, a0, a3
     78 1:
     79 	and	a3, a2, ~3		# compute number of whole words left
     80 	subu	a2, a2, a3		#   which has to be >= (16-3) & ~3
     81 	addu	a3, a3, a0		# compute ending address
     82 2:
     83 	lw	v0, 0(a0)		# compare words
     84 	lw	v1, 0(a1)
     85 	addu	a0, a0, 4
     86 	bne	v0, v1, nomatch
     87 	addu	a1, a1, 4
     88 	bne	a0, a3, 2b
     89 	nop
     90 	b	small			# finish remainder
     91 	nop
     92 unaligned:
     93 	beq	a3, zero, 2f
     94 	subu	a2, a2, a3		# subtract from remaining count
     95 	addu	a3, a3, a0		# compute ending address
     96 1:
     97 	lbu	v0, 0(a0)		# compare bytes until a1 word aligned
     98 	lbu	v1, 0(a1)
     99 	addu	a0, a0, 1
    100 	bne	v0, v1, nomatch
    101 	addu	a1, a1, 1
    102 	bne	a0, a3, 1b
    103 	nop
    104 2:
    105 	and	a3, a2, ~3		# compute number of whole words left
    106 	subu	a2, a2, a3		#   which has to be >= (16-3) & ~3
    107 	addu	a3, a3, a0		# compute ending address
    108 3:
    109 	LWHI	v0, 0(a0)		# compare words a0 unaligned, a1 aligned
    110 	LWLO	v0, 3(a0)
    111 	lw	v1, 0(a1)
    112 	addu	a0, a0, 4
    113 	bne	v0, v1, nomatch
    114 	addu	a1, a1, 4
    115 	bne	a0, a3, 3b
    116 	nop
    117 small:
    118 	ble	a2, zero, match
    119 	addu	a3, a2, a0		# compute ending address
    120 1:
    121 	lbu	v0, 0(a0)
    122 	lbu	v1, 0(a1)
    123 	addu	a0, a0, 1
    124 	bne	v0, v1, nomatch
    125 	addu	a1, a1, 1
    126 	bne	a0, a3, 1b
    127 	nop
    128 match:
    129 	j	ra
    130 	move	v0, zero
    131 nomatch:
    132 	j	ra
    133 	li	v0, 1
    134 	.set	reorder
    135 END(bcmp)
    136