/* $OpenBSD: bcmp.S,v 1.5 2015/08/31 02:53:56 guenther Exp $ */ /*- * Copyright (c) 1991, 1993 * The Regents of the University of California. All rights reserved. * * This code is derived from software contributed to Berkeley by * Ralph Campbell. * * 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 "SYS.h" /* bcmp(s1, s2, n) */ LEAF(bcmp, 0) .set noreorder blt a2, 16, small # is it worth any trouble? xor v0, a0, a1 # compare low two bits of addresses and v0, v0, 3 dsubu a3, zero, a1 # compute # bytes to word align address bne v0, zero, unaligned # not possible to align addresses and a3, a3, 3 beq a3, zero, 1f dsubu a2, a2, a3 # subtract from remaining count move v0, v1 # init v0,v1 so unmodified bytes match LWHI v0, 0(a0) # read 1, 2, or 3 bytes LWHI v1, 0(a1) daddu a1, a1, a3 bne v0, v1, nomatch daddu a0, a0, a3 1: and a3, a2, ~3 # compute number of whole words left dsubu a2, a2, a3 # which has to be >= (16-3) & ~3 daddu a3, a3, a0 # compute ending address 2: lw v0, 0(a0) # compare words lw v1, 0(a1) daddu a0, a0, 4 bne v0, v1, nomatch daddu a1, a1, 4 bne a0, a3, 2b nop b small # finish remainder nop unaligned: beq a3, zero, 2f dsubu a2, a2, a3 # subtract from remaining count daddu a3, a3, a0 # compute ending address 1: lbu v0, 0(a0) # compare bytes until a1 word aligned lbu v1, 0(a1) daddu a0, a0, 1 bne v0, v1, nomatch daddu a1, a1, 1 bne a0, a3, 1b nop 2: and a3, a2, ~3 # compute number of whole words left dsubu a2, a2, a3 # which has to be >= (16-3) & ~3 daddu a3, a3, a0 # compute ending address 3: LWHI v0, 0(a0) # compare words a0 unaligned, a1 aligned LWLO v0, 3(a0) lw v1, 0(a1) daddu a0, a0, 4 bne v0, v1, nomatch daddu a1, a1, 4 bne a0, a3, 3b nop small: ble a2, zero, match daddu a3, a2, a0 # compute ending address 1: lbu v0, 0(a0) lbu v1, 0(a1) daddu a0, a0, 1 bne v0, v1, nomatch daddu a1, a1, 1 bne a0, a3, 1b nop match: j ra move v0, zero nomatch: j ra li v0, 1 .set reorder END_WEAK(bcmp)
