minix/common/lib/libc/arch/m68k/string/memcmp.S

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/* $NetBSD: memcmp.S,v 1.1 2005/12/20 19:28:49 christos 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 <machine/asm.h>
#if defined(LIBC_SCCS) && !defined(lint)
#if 0
RCSID("from: @(#)bcmp.s 5.1 (Berkeley) 5/12/90")
#else
RCSID("$NetBSD: memcmp.S,v 1.1 2005/12/20 19:28:49 christos Exp $")
#endif
#endif /* LIBC_SCCS and not lint */
/* 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
jeq bcdone | if zero, nothing to do
movl %a0,%d1
btst #0,%d1 | string 1 address odd?
jeq bceven | no, skip alignment
cmpmb %a0@+,%a1@+ | yes, compare a byte
jne bcnoteq | not equal, return non-zero
subql #1,%d0 | adjust count
jeq bcdone | count 0, reutrn zero
bceven:
movl %a1,%d1
btst #0,%d1 | string 2 address odd?
jne bcbloop | yes, no hope for alignment, compare bytes
movl %d0,%d1 | no, both even
lsrl #2,%d1 | convert count to longword count
jeq bcbloop | count 0, skip longword loop
bclloop:
cmpml %a0@+,%a1@+ | compare a longword
jne bcnoteql | not equal, return non-zero
subql #1,%d1 | adjust count
jne bclloop | still more, keep comparing
andl #3,%d0 | what remains
jeq bcdone | nothing, all done
bcbloop:
cmpmb %a0@+,%a1@+ | compare a byte
jne bcnoteq | not equal, return non-zero
subql #1,%d0 | adjust count
jne 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