/* $NetBSD: memcmp.S,v 1.1 2014/09/03 19:34:25 matt Exp $ */ /*- * Copyright (c) 2014 The NetBSD Foundation, Inc. * All rights reserved. * * This code is derived from software contributed to The NetBSD Foundation * by Matt Thomas of 3am Software Foundry. * * 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. * * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. 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 FOUNDATION 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. */ /* * * * int memcmp(const char *s1, const char *s2, size_t n); * * for (; n-- != 0; s1++, s2++) { * if (*s1 < *s2) * return -1; * if (*s1 > *s2) * return 1; * } * return 0; * * Return: ((s1 > s2) ? 1 : (s1 < s2) ? -1 : 0) * * ========================================================================== */ #include <machine/asm.h> .text .align 4 /* LINTSTUB: Func: void *memcmp(const void *, const void *, size_t) */ ENTRY(memcmp) /* * Check count passed in R5. If zero, return 0; otherwise continue. */ l.sfeqi r5, 0 /* nothing to compare? */ l.bf .Lret_0 /* yes, return equality */ l.nop #ifdef _KERNEL l.sfeqi r5, 6 /* less than two words? */ l.bnf .Lsixbyte_compare /* yes, just compare by bytes */ l.nop #endif l.sfgesi r5, 7 /* less than two words? */ l.bnf .Lbyte_compare /* yes, just compare by bytes */ l.nop l.xor r6, r3, r4 /* check alignment compatibility */ l.andi r6, r6, 3 /* only care about the two bits */ l.sfeqi r6, 0 /* same alignment? */ l.bnf .Lmisaligned /* no, avoid alignment errors */ l.nop /* * At this point, we know we read the data via word accesses. */ l.andi r7, r3, 3 /* check alignment */ l.sfeqi r7, 0 /* word aligned? */ l.bf .Lword_compare /* yes, it is. */ l.sub r3, r3, r7 /* align string 1 */ l.sub r4, r4, r7 /* align string 2 */ l.add r5, r5, r7 /* pad length */ l.lwz r15, 0(r3) /* load word from s1 */ l.lwz r17, 0(r4) /* load word from s2 */ l.slli r7, r7, 3 /* bytes to bits */ l.sll r15, r15, r7 /* shift away leading bytes */ l.sll r17, r17, r7 /* shift away leading bytes */ l.j .Lword_compare /* now we can compare them */ l.nop .Lword_loop: l.lwz r15, 0(r3) /* load s1 word */ l.lwz r17, 0(r4) /* load s2 word */ .Lword_compare: l.sfeq r15, r17 /* compare s1 and s2 words */ l.bnf .Lall_done /* different? we're done */ l.addi r3, r3, 4 /* advance s1 one word */ l.addi r4, r4, 4 /* advance s2 one word */ l.addi r5, r5, -4 /* decrement one word */ l.sfgtsi r5, 4 /* at least more than a word? */ l.bf .Lword_loop /* yes, loop around */ l.nop l.sfeqi r5, 0 /* nothing left? */ l.bf .Lret_0 /* yes, return equality */ l.nop /* * Fall through to handle the last word */ l.sub r3, r0, r5 /* If count <= 4, handle */ l.andi r3, r3, 3 /* mask off low 2 bits */ l.slli r3, r3, 3 /* count *= 8 */ l.srl r15, r15, r3 /* discard extra s1 bytes */ l.srl r17, r17, r3 /* discard extra s2 bytes */ l.sfeq r17, r15 /* compare result */ l.bnf .Lall_done .Lret_0: l.addi r11, r0, 0 l.jr lr l.nop /* * The two string don't have the same word alignment. */ .Lmisaligned: l.sfeqi r6, 2 /* check for halfword alignment */ l.bnf .Lbyte_compare l.nop l.andi r7, r3, 1 l.sfeqi r7, 0 l.bf .Lhalfword_loop l.nop l.addi r5, r5, 1 l.addi r3, r3, -1 l.addi r4, r4, -1 l.lbz r15, 1(r3) l.lbz r17, 1(r4) l.j .Lhalfword_compare l.nop .Lhalfword_loop: l.lhz r15, 0(r3) l.lhz r17, 0(r4) .Lhalfword_compare: l.sfeq r15, r17 l.bnf .Lall_done l.nop l.addi r3, r3, 2 l.addi r4, r4, 2 l.addi r5, r5, -2 l.sfgesi r5, 2 l.bf .Lhalfword_loop l.nop .Lbyte_compare: l.addi r5, r5, -1 l.sfgesi r5, 0 l.bnf .Lret_0 l.nop l.lbz r15, 0(r3) l.lbz r17, 0(r4) l.addi r3, r3, 1 l.addi r4, r4, 1 l.sfeq r15, r17 l.bf .Lbyte_compare l.nop .Lall_done: l.sub r11, r15, r17 /* subtract s2 from s1 */ l.srai r11, r11, 30 /* replicate sign bit thru bit 1 */ l.ori r11, r11, 1 /* make sure bit 0 is set */ l.jr lr l.nop #ifdef _KERNEL .Lsixbyte_compare: l.or r7, r3, r4 l.andi r7, r7, 1 l.sfeqi r7, 0 l.bnf .Lbyte_compare l.nop l.lhz r15, 0(r3) l.lhz r17, 0(r4) l.sfeq r15, r17 l.bnf .Lall_done l.nop l.lhz r15, 2(r3) l.lhz r17, 2(r4) l.sfeq r15, r17 l.bnf .Lall_done l.nop l.lhz r15, 4(r3) l.lhz r17, 4(r4) l.sfeq r15, r17 l.bnf .Lall_done l.nop l.addi r11, r0, 0 l.jr lr l.nop #endif END(memcmp)
