/*- * Copyright (c) 2013 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 RCSID("$NetBSD: memset_naive.S,v 1.1.52.1 2024/07/20 14:52:04 martin Exp $") /* * This isn't quite as simple/short as it could be but the truly trivial * memset was an order of magnitude slower than this. */ ENTRY(memset) /* LINTSTUB: void *memset(void *, int, size_t) */ mov ip, r0 /* need to preserve r0 */ cmp r2, #10 /* 10 bytes or less? */ bls .Lbyte_by_byte /* yes, bytewise is faster */ ands r3, r1, #0xff /* we are dealing with bytes */ orrne r3, r3, r3, lsl #8 /* move value into 2nd byte lane */ orrne r3, r3, r3, lsl #16 /* move value into all byte lanes */ mov r1, r2 /* move count */ ands r2, ip, #7 /* are we dword aligned? */ beq 1f /* yes we are */ rsb r2, r2, #8 /* how many bytes until aligned? */ sub r1, r1, r2 /* subtract from count */ tst ip, #1 /* halfword aligned? */ strneb r3, [ip], #1 /* nope, write a byte */ tst ip, #2 /* word aligned? */ strneh r3, [ip], #2 /* nope, write a halfword */ tst ip, #4 /* dword aligned? */ strne r3, [ip], #4 /* nope, write a word */ /* * At this point, we are dword aligned. */ 1: mov r2, r3 /* duplicate fill value */ 2: subs r1, r1, #16 /* can we write 16 bytes? */ stmhsia ip!, {r2,r3} /* yes, write the first 8 of them */ stmhsia ip!, {r2,r3} /* yes, write the second 8 of them */ bhi 2b /* more left to fill */ RETc(eq) /* no, return */ /* * Our count went negative but the bits below 16 haven't changed. * So we are effectively testing modulo 16. */ tst r1, #8 /* can we write at least 8 bytes? */ stmneia ip!, {r2,r3} /* so do it */ tst r1, #4 /* can we write at least 4 bytes? */ strne r3, [ip], #4 /* so do it */ tst r1, #2 /* can we write at least 2 bytes? */ strneh r3, [ip], #2 /* so do it */ tst r1, #1 /* can we write 1 bytes? */ strneb r3, [ip], #1 /* so do it */ RET /* return */ .Lbyte_by_byte: subs r2, r2, #1 /* can we write a byte? */ RETc(lo) /* no, return */ strb r3, [ip], #1 /* write a byte */ b .Lbyte_by_byte /* do next byte */ END(memset)