1/* $OpenBSD: bcmp.S,v 1.4 2004/10/08 14:42:09 pefo Exp $ */ 2/*- 3 * Copyright (c) 1991, 1993 4 * The Regents of the University of California. All rights reserved. 5 * 6 * This code is derived from software contributed to Berkeley by 7 * Ralph Campbell. 8 * 9 * Redistribution and use in source and binary forms, with or without 10 * modification, are permitted provided that the following conditions 11 * are met: 12 * 1. Redistributions of source code must retain the above copyright 13 * notice, this list of conditions and the following disclaimer. 14 * 2. Redistributions in binary form must reproduce the above copyright 15 * notice, this list of conditions and the following disclaimer in the 16 * documentation and/or other materials provided with the distribution. 17 * 3. Neither the name of the University nor the names of its contributors 18 * may be used to endorse or promote products derived from this software 19 * without specific prior written permission. 20 * 21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31 * SUCH DAMAGE. 32 */ 33 34#include "DEFS.h" 35 36 37/* 38 * bcmp(s1, s2, n) 39 */ 40LEAF(bcmp, 0) 41 .set noreorder 42 blt a2, 16, smallcmp # is it worth any trouble? 43 xor v0, a0, a1 # compare low two bits of addresses 44 and v0, v0, 3 45 PTR_SUBU a3, zero, a1 # compute # bytes to word align address 46 bne v0, zero, unalignedcmp # not possible to align addresses 47 and a3, a3, 3 48 49 beq a3, zero, 1f 50 PTR_SUBU a2, a2, a3 # subtract from remaining count 51 move v0, v1 # init v0,v1 so unmodified bytes match 52 LWHI v0, 0(a0) # read 1, 2, or 3 bytes 53 LWHI v1, 0(a1) 54 PTR_ADDU a1, a1, a3 55 bne v0, v1, nomatch 56 PTR_ADDU a0, a0, a3 571: 58 and a3, a2, ~3 # compute number of whole words left 59 PTR_SUBU a2, a2, a3 # which has to be >= (16-3) & ~3 60 PTR_ADDU a3, a3, a0 # compute ending address 612: 62 lw v0, 0(a0) # compare words 63 lw v1, 0(a1) 64 PTR_ADDU a0, a0, 4 65 bne v0, v1, nomatch 66 PTR_ADDU a1, a1, 4 67 bne a0, a3, 2b 68 nop 69 b smallcmp # finish remainder 70 nop 71unalignedcmp: 72 beq a3, zero, 2f 73 PTR_SUBU a2, a2, a3 # subtract from remaining count 74 PTR_ADDU a3, a3, a0 # compute ending address 751: 76 lbu v0, 0(a0) # compare bytes until a1 word aligned 77 lbu v1, 0(a1) 78 PTR_ADDU a0, a0, 1 79 bne v0, v1, nomatch 80 PTR_ADDU a1, a1, 1 81 bne a0, a3, 1b 82 nop 832: 84 and a3, a2, ~3 # compute number of whole words left 85 PTR_SUBU a2, a2, a3 # which has to be >= (16-3) & ~3 86 PTR_ADDU a3, a3, a0 # compute ending address 873: 88 LWHI v0, 0(a0) # compare words a0 unaligned, a1 aligned 89 LWLO v0, 3(a0) 90 lw v1, 0(a1) 91 PTR_ADDU a0, a0, 4 92 bne v0, v1, nomatch 93 PTR_ADDU a1, a1, 4 94 bne a0, a3, 3b 95 nop 96smallcmp: 97 ble a2, zero, match 98 PTR_ADDU a3, a2, a0 # compute ending address 991: 100 lbu v0, 0(a0) 101 lbu v1, 0(a1) 102 PTR_ADDU a0, a0, 1 103 bne v0, v1, nomatch 104 PTR_ADDU a1, a1, 1 105 bne a0, a3, 1b 106 nop 107match: 108 j ra 109 move v0, zero 110nomatch: 111 j ra 112 dli v0, 1 113END(bcmp) 114