/* $NetBSD: memcmp.S,v 1.3 2018/07/09 06:07:06 ryo 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. */ #include <machine/asm.h> RCSID("$NetBSD: memcmp.S,v 1.3 2018/07/09 06:07:06 ryo Exp $") ENTRY(memcmp) mov x9, x0 mov x10, x1 mov x0, xzr cbz x2, .Lmemcmp_ret #ifdef _KERNEL cmp x2, #6 b.eq .Lmemcmp_6bytes #endif cmp x2, #8 b.ls .Lmemcmp_lessthan8 ands x3, x9, #7 b.eq .Lmemcmp_dword_loop /* * The src1 address is not dword aligned. */ add x2, x2, x3 /* add unalignment to length */ sub x2, x2, #8 /* now subtract a dword */ sub x9, x9, x3 /* dword align src1 */ ldr x6, [x10], #8 /* load dword from src2 */ sub x10, x10, x3 /* src2 -= x3 */ lsl x3, x3, #3 /* convert bytes to bits */ ldr x4, [x9], #8 /* load dword from src1 */ #ifdef __AARCH64EB__ lsl x4, x4, x3 /* discard leading bytes from data1 */ lsr x6, x6, x3 /* discard leading bytes from data2 */ lsl x6, x6, x3 /* get back bit position */ #else lsr x4, x4, x3 /* discard leading bytes from data1 */ lsl x6, x6, x3 /* discard leading bytes from data2 */ lsr x6, x6, x3 /* get back bit position */ #endif subs x0, x4, x6 /* compare data */ b.ne .Lmemcmp_last_compare /* difference. find it */ .Lmemcmp_dword_loop: subs x2, x2, #8 b.mi .Lmemcmp_finish_dword ldr x4, [x9], #8 ldr x6, [x10], #8 subs x0, x4, x6 b.eq .Lmemcmp_dword_loop /* no difference. go to loop */ b .Lmemcmp_last_compare /* go find the difference. */ .Lmemcmp_finish_dword: /* * we might have gotten here with nothing left. If so, just bail. */ tst x2, #7 b.eq .Lmemcmp_ret mov x4, xzr mov x6, xzr /* * */ tbz x2, #2, .Lmemcmp_finish_word ldr w4, [x9], #4 ldr w6, [x10], #4 #ifdef __AARCH64EB__ lsl x4, x4, #32 /* move to MSW */ lsl x6, x6, #32 /* move to MSW */ #endif .Lmemcmp_finish_word: tbz x2, #1, .Lmemcmp_finish_hword ldrh w5, [x9], #2 ldrh w7, [x10], #2 #ifdef __AARCH64EB__ orr x4, x4, x5, lsl #16 orr x6, x6, x7, lsl #16 #else orr x4, x4, x5, lsl #32 orr x6, x6, x7, lsl #32 #endif .Lmemcmp_finish_hword: tbz x2, #0, .Lmemcmp_last_compare0 ldrb w5, [x9] ldrb w7, [x10] #ifdef __AARCH64EB__ orr x4, x4, x5, lsl #8 orr x6, x6, x7, lsl #8 #else orr x4, x4, x5, lsl #48 orr x6, x6, x7, lsl #48 #endif b .Lmemcmp_last_compare0 /* go find the difference. */ /* * D */ .Lmemcmp_lessthan8: sub x2, x2, #1 1: ldrb w4, [x9], #1 ldrb w5, [x10], #1 subs x2, x2, #1 ccmp x4, x5, #0, cs b.eq 1b sub x0, x4, x5 .Lmemcmp_ret: ret #ifdef _KERNEL .Lmemcmp_6bytes: ldr w4, [x9], #4 ldrh w5, [x9] #if __AARCH64EB__ orr x4, x4, x5, lsl #48 rev x4, x4 #else orr x4, x4, x5, lsl #32 #endif ldr w6, [x10], #4 ldrh w7, [x10] #if __AARCH64EB__ orr x6, x6, x7, lsl #48 rev x6, x6 #else orr x6, x6, x7, lsl #32 #endif #endif /* _KERNEL */ /* * We have loaded the final bytes in x4 and x6 in host-endian. Now we have * to figure what the difference is (if any). First we subtract. Any bytes * that are the same will be 0. So to find the first non-zero byte we byterev * and then use clz to find that byte. * We mask the location to get the start of the byte. We shift both * data dwords left to remove the equal part. Then we shift right to discard * the trailing bytes. Then we subtract and return. */ .Lmemcmp_last_compare0: subs x0, x4, x6 b.eq .Lmemcmp_ret .Lmemcmp_last_compare: #if __AARCH64EB__ clz x1, x0 /* find first non-zero byte */ rev x0, x0 #else rev x1, x0 clz x1, x1 /* find first non-zero byte */ #endif bfi x1, xzr, #0, #3 /* make it byte aligned */ lsr x1, x0, x1 /* shift to LSB */ #if __AARCH64EL__ rev x4, x4 /* byte reverse */ rev x6, x6 /* byte reverse */ #endif subs x0, x4, x6 csetm x0, cc /* set mask bits as sign */ bfm x0, x1, #0, #7 /* extend with sign bit */ ret END(memcmp)
