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      1 /*	$NetBSD: bcmp.S,v 1.9 2009/12/14 01:07:42 matt 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. Neither the name of the University nor the names of its contributors
     19  *    may be used to endorse or promote products derived from this software
     20  *    without specific prior written permission.
     21  *
     22  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     23  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     24  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     25  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     26  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     27  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     28  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     29  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     30  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     31  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     32  * SUCH DAMAGE.
     33  */
     34 
     35 #include <mips/asm.h>
     36 #define _LOCORE		/* XXX not really, just assembly-code source */
     37 #include <machine/endian.h>	/* LWLO/LWHI, SWLO/SWHI */
     38 
     39 #if defined(LIBC_SCCS) && !defined(lint)
     40 #if 0
     41 	RCSID("from: @(#)bcmp.s	8.1 (Berkeley) 6/4/93")
     42 #else
     43 	RCSID("$NetBSD: bcmp.S,v 1.9 2009/12/14 01:07:42 matt Exp $")
     44 #endif
     45 #endif /* LIBC_SCCS and not lint */
     46 
     47 /* bcmp(s1, s2, n) */
     48 
     49 
     50 LEAF(bcmp)
     51 	.set	noreorder
     52 	blt		a2, 16, small	# is it worth any trouble?
     53 	xor		v0, a0, a1	# compare low two bits of addresses
     54 	and		v0, v0, 3
     55 	PTR_SUBU	a3, zero, a1	# compute # bytes to word align address
     56 	bne		v0, zero, unaligned # not possible to align addresses
     57 	and		a3, a3, 3
     58 
     59 	beq		a3, zero, 1f
     60 	PTR_SUBU	a2, a2, a3	# subtract from remaining count
     61 	move		v0, v1		# init v0,v1 so unmodified bytes match
     62 	LWHI		v0, 0(a0)	# read 1, 2, or 3 bytes
     63 	LWHI		v1, 0(a1)
     64 	PTR_ADDU	a1, a1, a3
     65 	bne		v0, v1, nomatch
     66 	PTR_ADDU	a0, a0, a3
     67 1:
     68 	and		a3, a2, ~3	# compute number of whole words left
     69 	PTR_SUBU	a2, a2, a3	#   which has to be >= (16-3) & ~3
     70 	PTR_ADDU	a3, a3, a0	# compute ending address
     71 2:
     72 	lw		v0, 0(a0)	# compare words
     73 	lw		v1, 0(a1)
     74 	PTR_ADDU	a0, a0, 4
     75 	bne		v0, v1, nomatch
     76 	PTR_ADDU	a1, a1, 4
     77 	bne		a0, a3, 2b
     78 	nop
     79 	b		small		# finish remainder
     80 	nop
     81 unaligned:
     82 	beq		a3, zero, 2f
     83 	PTR_SUBU	a2, a2, a3	# subtract from remaining count
     84 	PTR_ADDU	a3, a3, a0	# compute ending address
     85 1:
     86 	lbu		v0, 0(a0)	# compare bytes until a1 word aligned
     87 	lbu		v1, 0(a1)
     88 	PTR_ADDU	a0, a0, 1
     89 	bne		v0, v1, nomatch
     90 	PTR_ADDU	a1, a1, 1
     91 	bne		a0, a3, 1b
     92 	nop
     93 2:
     94 	and		a3, a2, ~3	# compute number of whole words left
     95 	PTR_SUBU	a2, a2, a3	#   which has to be >= (16-3) & ~3
     96 	PTR_ADDU	a3, a3, a0	# compute ending address
     97 3:
     98 	LWHI		v0, 0(a0)	# compare words a0 unaligned, a1 aligned
     99 	LWLO		v0, 3(a0)
    100 	lw		v1, 0(a1)
    101 	PTR_ADDU	a0, a0, 4
    102 	bne		v0, v1, nomatch
    103 	PTR_ADDU	a1, a1, 4
    104 	bne		a0, a3, 3b
    105 	nop
    106 small:
    107 	ble		a2, zero, match
    108 	PTR_ADDU	a3, a2, a0		# compute ending address
    109 1:
    110 	lbu		v0, 0(a0)
    111 	lbu		v1, 0(a1)
    112 	PTR_ADDU	a0, a0, 1
    113 	bne		v0, v1, nomatch
    114 	PTR_ADDU	a1, a1, 1
    115 	bne		a0, a3, 1b
    116 	nop
    117 match:
    118 	j		ra
    119 	move		v0, zero
    120 nomatch:
    121 	j		ra
    122 	li		v0, 1
    123 	.set	reorder
    124 END(bcmp)
    125