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/* $OpenBSD: memcmp.S,v 1.2 2003/06/02 23:28:08 millert Exp $ */
/*-
* Copyright (c) 1990 The Regents of the University of California.
* All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* the Systems Programming Group of the University of Utah Computer
* Science Department.
*
* 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 "DEFS.h"
#if defined(LIBC_SCCS)
.text
.asciz "$OpenBSD: memcmp.S,v 1.2 2003/06/02 23:28:08 millert Exp $"
#endif /* LIBC_SCCS */
/* memcmp(s1, s2, n) */
/*
* This is probably not the best we can do, but it is still 2-10 times
* faster than the C version in the portable gen directory.
*
* Things that might help:
* - longword align when possible (only on the 68020)
* - use nested DBcc instructions or use one and limit size to 64K
*/
ENTRY(memcmp)
movl sp@(4),a0 | string 1
movl sp@(8),a1 | string 2
movl sp@(12),d0 | length
beq bcdone | if zero, nothing to do
movl a0,d1
btst #0,d1 | string 1 address odd?
beq bceven | no, skip alignment
cmpmb a0@+,a1@+ | yes, compare a byte
bne bcnoteq | not equal, return non-zero
subql #1,d0 | adjust count
beq bcdone | count 0, reutrn zero
bceven:
movl a1,d1
btst #0,d1 | string 2 address odd?
bne bcbloop | yes, no hope for alignment, compare bytes
movl d0,d1 | no, both even
lsrl #2,d1 | convert count to longword count
beq bcbloop | count 0, skip longword loop
bclloop:
cmpml a0@+,a1@+ | compare a longword
bne bcnoteql | not equal, return non-zero
subql #1,d1 | adjust count
bne bclloop | still more, keep comparing
andl #3,d0 | what remains
beq bcdone | nothing, all done
bcbloop:
cmpmb a0@+,a1@+ | compare a byte
bne bcnoteq | not equal, return non-zero
subql #1,d0 | adjust count
bne bcbloop | still more, keep going
rts
bcnoteql:
subql #4,a0
subql #4,a1
movl #4,d0
jra bcbloop
bcnoteq:
clrl d0
clrl d1
movb a0@-,d0
movb a1@-,d1
subl d1,d0
bcdone:
rts
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