1/* Copyright (c) 2010-2011, Linaro Limited 2 All rights reserved. 3 4 Redistribution and use in source and binary forms, with or without 5 modification, are permitted provided that the following conditions 6 are met: 7 8 * Redistributions of source code must retain the above copyright 9 notice, this list of conditions and the following disclaimer. 10 11 * Redistributions in binary form must reproduce the above copyright 12 notice, this list of conditions and the following disclaimer in the 13 documentation and/or other materials provided with the distribution. 14 15 * Neither the name of Linaro Limited nor the names of its 16 contributors may be used to endorse or promote products derived 17 from this software without specific prior written permission. 18 19 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 20 "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 21 LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 22 A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 23 HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 24 SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 25 LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 26 DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 27 THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 28 (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 29 OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 30 */ 31 32/* 33 Written by Dave Gilbert <david.gilbert@linaro.org> 34 35 This memset routine is optimised on a Cortex-A9 and should work on 36 all ARMv7 processors. 37 38 */ 39 40 .syntax unified 41 .arch armv7-a 42 43@ 2011-08-30 david.gilbert@linaro.org 44@ Extracted from local git 2f11b436 45 46@ this lets us check a flag in a 00/ff byte easily in either endianness 47#ifdef __ARMEB__ 48#define CHARTSTMASK(c) 1<<(31-(c*8)) 49#else 50#define CHARTSTMASK(c) 1<<(c*8) 51#endif 52 .text 53 .thumb 54 55@ --------------------------------------------------------------------------- 56 .thumb_func 57 .align 2 58 .p2align 4,,15 59 .global memset 60 .type memset,%function 61memset: 62 @ r0 = address 63 @ r1 = character 64 @ r2 = count 65 @ returns original address in r0 66 67 mov r3, r0 @ Leave r0 alone 68 cbz r2, 10f @ Exit if 0 length 69 70 tst r0, #7 71 beq 2f @ Already aligned 72 73 @ Ok, so we're misaligned here 741: 75 strb r1, [r3], #1 76 subs r2,r2,#1 77 tst r3, #7 78 cbz r2, 10f @ Exit if we hit the end 79 bne 1b @ go round again if still misaligned 80 812: 82 @ OK, so we're aligned 83 push {r4,r5,r6,r7} 84 bics r4, r2, #15 @ if less than 16 bytes then need to finish it off 85 beq 5f 86 873: 88 @ POSIX says that ch is cast to an unsigned char. A uxtb is one 89 @ byte and takes two cycles, where an AND is four bytes but one 90 @ cycle. 91 and r1, #0xFF 92 orr r1, r1, r1, lsl#8 @ Same character into all bytes 93 orr r1, r1, r1, lsl#16 94 mov r5,r1 95 mov r6,r1 96 mov r7,r1 97 984: 99 subs r4,r4,#16 100 stmia r3!,{r1,r5,r6,r7} 101 bne 4b 102 and r2,r2,#15 103 104 @ At this point we're still aligned and we have upto align-1 bytes left to right 105 @ we can avoid some of the byte-at-a time now by testing for some big chunks 106 tst r2,#8 107 itt ne 108 subne r2,r2,#8 109 stmiane r3!,{r1,r5} 110 1115: 112 pop {r4,r5,r6,r7} 113 cbz r2, 10f 114 115 @ Got to do any last < alignment bytes 1166: 117 subs r2,r2,#1 118 strb r1,[r3],#1 119 bne 6b 120 12110: 122 bx lr @ goodbye 123