Annotation of sys/lib/libkern/arch/m68k/memcmp.S, Revision 1.1
1.1 ! nbrk 1: /* $OpenBSD: memcmp.S,v 1.2 2003/06/02 23:28:08 millert Exp $ */
! 2:
! 3: /*-
! 4: * Copyright (c) 1990 The Regents of the University of California.
! 5: * All rights reserved.
! 6: *
! 7: * This code is derived from software contributed to Berkeley by
! 8: * the Systems Programming Group of the University of Utah Computer
! 9: * Science Department.
! 10: *
! 11: * Redistribution and use in source and binary forms, with or without
! 12: * modification, are permitted provided that the following conditions
! 13: * are met:
! 14: * 1. Redistributions of source code must retain the above copyright
! 15: * notice, this list of conditions and the following disclaimer.
! 16: * 2. Redistributions in binary form must reproduce the above copyright
! 17: * notice, this list of conditions and the following disclaimer in the
! 18: * documentation and/or other materials provided with the distribution.
! 19: * 3. Neither the name of the University nor the names of its contributors
! 20: * may be used to endorse or promote products derived from this software
! 21: * without specific prior written permission.
! 22: *
! 23: * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
! 24: * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
! 25: * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
! 26: * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
! 27: * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
! 28: * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
! 29: * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
! 30: * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
! 31: * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
! 32: * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
! 33: * SUCH DAMAGE.
! 34: */
! 35:
! 36: #include "DEFS.h"
! 37:
! 38: #if defined(LIBC_SCCS)
! 39: .text
! 40: .asciz "$OpenBSD: memcmp.S,v 1.2 2003/06/02 23:28:08 millert Exp $"
! 41: #endif /* LIBC_SCCS */
! 42:
! 43: /* memcmp(s1, s2, n) */
! 44:
! 45: /*
! 46: * This is probably not the best we can do, but it is still 2-10 times
! 47: * faster than the C version in the portable gen directory.
! 48: *
! 49: * Things that might help:
! 50: * - longword align when possible (only on the 68020)
! 51: * - use nested DBcc instructions or use one and limit size to 64K
! 52: */
! 53: ENTRY(memcmp)
! 54: movl sp@(4),a0 | string 1
! 55: movl sp@(8),a1 | string 2
! 56: movl sp@(12),d0 | length
! 57: beq bcdone | if zero, nothing to do
! 58: movl a0,d1
! 59: btst #0,d1 | string 1 address odd?
! 60: beq bceven | no, skip alignment
! 61: cmpmb a0@+,a1@+ | yes, compare a byte
! 62: bne bcnoteq | not equal, return non-zero
! 63: subql #1,d0 | adjust count
! 64: beq bcdone | count 0, reutrn zero
! 65: bceven:
! 66: movl a1,d1
! 67: btst #0,d1 | string 2 address odd?
! 68: bne bcbloop | yes, no hope for alignment, compare bytes
! 69: movl d0,d1 | no, both even
! 70: lsrl #2,d1 | convert count to longword count
! 71: beq bcbloop | count 0, skip longword loop
! 72: bclloop:
! 73: cmpml a0@+,a1@+ | compare a longword
! 74: bne bcnoteql | not equal, return non-zero
! 75: subql #1,d1 | adjust count
! 76: bne bclloop | still more, keep comparing
! 77: andl #3,d0 | what remains
! 78: beq bcdone | nothing, all done
! 79: bcbloop:
! 80: cmpmb a0@+,a1@+ | compare a byte
! 81: bne bcnoteq | not equal, return non-zero
! 82: subql #1,d0 | adjust count
! 83: bne bcbloop | still more, keep going
! 84: rts
! 85: bcnoteql:
! 86: subql #4,a0
! 87: subql #4,a1
! 88: movl #4,d0
! 89: jra bcbloop
! 90: bcnoteq:
! 91: clrl d0
! 92: clrl d1
! 93: movb a0@-,d0
! 94: movb a1@-,d1
! 95: subl d1,d0
! 96: bcdone:
! 97: rts
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