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bcmp.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: @(#)bcmp.s	8.1 (Berkeley) 6/4/93")
     41 	ASMSTR("$Id: bcmp.S,v 1.1 1994/05/24 07:12:46 glass Exp $")
     42 #endif /* LIBC_SCCS and not lint */
     43 
     44 /* bcmp(s1, s2, n) */
     45 
     46 #ifdef MIPSEL
     47 #	define	LWHI	lwr
     48 #	define	LWLO	lwl
     49 #	define	SWHI	swr
     50 #	define	SWLO	swl
     51 #endif
     52 #ifdef MIPSEB
     53 #	define	LWHI	lwl
     54 #	define	LWLO	lwr
     55 #	define	SWHI	swl
     56 #	define	SWLO	swr
     57 #endif
     58 
     59 LEAF(bcmp)
     60 	.set	noreorder
     61 	blt	a2, 16, small		# is it worth any trouble?
     62 	xor	v0, a0, a1		# compare low two bits of addresses
     63 	and	v0, v0, 3
     64 	subu	a3, zero, a1		# compute # bytes to word align address
     65 	bne	v0, zero, unaligned	# not possible to align addresses
     66 	and	a3, a3, 3
     67 
     68 	beq	a3, zero, 1f
     69 	subu	a2, a2, a3		# subtract from remaining count
     70 	move	v0, v1			# init v0,v1 so unmodified bytes match
     71 	LWHI	v0, 0(a0)		# read 1, 2, or 3 bytes
     72 	LWHI	v1, 0(a1)
     73 	addu	a1, a1, a3
     74 	bne	v0, v1, nomatch
     75 	addu	a0, a0, a3
     76 1:
     77 	and	a3, a2, ~3		# compute number of whole words left
     78 	subu	a2, a2, a3		#   which has to be >= (16-3) & ~3
     79 	addu	a3, a3, a0		# compute ending address
     80 2:
     81 	lw	v0, 0(a0)		# compare words
     82 	lw	v1, 0(a1)
     83 	addu	a0, a0, 4
     84 	bne	v0, v1, nomatch
     85 	addu	a1, a1, 4
     86 	bne	a0, a3, 2b
     87 	nop
     88 	b	small			# finish remainder
     89 	nop
     90 unaligned:
     91 	beq	a3, zero, 2f
     92 	subu	a2, a2, a3		# subtract from remaining count
     93 	addu	a3, a3, a0		# compute ending address
     94 1:
     95 	lbu	v0, 0(a0)		# compare bytes until a1 word aligned
     96 	lbu	v1, 0(a1)
     97 	addu	a0, a0, 1
     98 	bne	v0, v1, nomatch
     99 	addu	a1, a1, 1
    100 	bne	a0, a3, 1b
    101 	nop
    102 2:
    103 	and	a3, a2, ~3		# compute number of whole words left
    104 	subu	a2, a2, a3		#   which has to be >= (16-3) & ~3
    105 	addu	a3, a3, a0		# compute ending address
    106 3:
    107 	LWHI	v0, 0(a0)		# compare words a0 unaligned, a1 aligned
    108 	LWLO	v0, 3(a0)
    109 	lw	v1, 0(a1)
    110 	addu	a0, a0, 4
    111 	bne	v0, v1, nomatch
    112 	addu	a1, a1, 4
    113 	bne	a0, a3, 3b
    114 	nop
    115 small:
    116 	ble	a2, zero, match
    117 	addu	a3, a2, a0		# compute ending address
    118 1:
    119 	lbu	v0, 0(a0)
    120 	lbu	v1, 0(a1)
    121 	addu	a0, a0, 1
    122 	bne	v0, v1, nomatch
    123 	addu	a1, a1, 1
    124 	bne	a0, a3, 1b
    125 	nop
    126 match:
    127 	j	ra
    128 	move	v0, zero
    129 nomatch:
    130 	j	ra
    131 	li	v0, 1
    132 	.set	reorder
    133 END(bcmp)
    134