strchr_arm.S revision 1.5.4.2
1 1.5.4.2 tls /*- 2 1.5.4.2 tls * Copyright (c) 2013 The NetBSD Foundation, Inc. 3 1.5.4.2 tls * All rights reserved. 4 1.5.4.2 tls * 5 1.5.4.2 tls * This code is derived from software contributed to The NetBSD Foundation 6 1.5.4.2 tls * by Matt Thomas of 3am Software Foundry. 7 1.5.4.2 tls * 8 1.5.4.2 tls * Redistribution and use in source and binary forms, with or without 9 1.5.4.2 tls * modification, are permitted provided that the following conditions 10 1.5.4.2 tls * are met: 11 1.5.4.2 tls * 1. Redistributions of source code must retain the above copyright 12 1.5.4.2 tls * notice, this list of conditions and the following disclaimer. 13 1.5.4.2 tls * 2. Redistributions in binary form must reproduce the above copyright 14 1.5.4.2 tls * notice, this list of conditions and the following disclaimer in the 15 1.5.4.2 tls * documentation and/or other materials provided with the distribution. 16 1.5.4.2 tls * 17 1.5.4.2 tls * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 18 1.5.4.2 tls * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 19 1.5.4.2 tls * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 20 1.5.4.2 tls * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 21 1.5.4.2 tls * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 22 1.5.4.2 tls * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 23 1.5.4.2 tls * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 24 1.5.4.2 tls * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 25 1.5.4.2 tls * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 26 1.5.4.2 tls * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 27 1.5.4.2 tls * POSSIBILITY OF SUCH DAMAGE. 28 1.5.4.2 tls */ 29 1.5.4.2 tls 30 1.5.4.2 tls #include <machine/asm.h> 31 1.5.4.2 tls 32 1.5.4.2 tls RCSID("$NetBSD: strchr_arm.S,v 1.5.4.2 2013/02/25 00:23:57 tls Exp $") 33 1.5.4.2 tls 34 1.5.4.2 tls #ifdef __ARMEL__ 35 1.5.4.2 tls #define BYTE0 0x000000ff 36 1.5.4.2 tls #define BYTE1 0x0000ff00 37 1.5.4.2 tls #define BYTE2 0x00ff0000 38 1.5.4.2 tls #define BYTE3 0xff000000 39 1.5.4.2 tls #define lshi lsl 40 1.5.4.2 tls #else 41 1.5.4.2 tls #define BYTE0 0xff000000 42 1.5.4.2 tls #define BYTE1 0x00ff0000 43 1.5.4.2 tls #define BYTE2 0x0000ff00 44 1.5.4.2 tls #define BYTE3 0x000000ff 45 1.5.4.2 tls #define lshi lsr 46 1.5.4.2 tls #endif 47 1.5.4.2 tls 48 1.5.4.2 tls .text 49 1.5.4.2 tls ENTRY(strchr) 50 1.5.4.2 tls and r2, r1, #0xff /* restrict to byte value */ 51 1.5.4.2 tls 1: tst r0, #3 /* test for word alignment */ 52 1.5.4.2 tls beq .Lpre_main_loop /* finally word aligned */ 53 1.5.4.2 tls ldrb r3, [r0], #1 /* load a byte */ 54 1.5.4.2 tls cmp r3, r2 /* is it a match? */ 55 1.5.4.2 tls beq 2f /* yes, return current ptr - 1 */ 56 1.5.4.2 tls teq r3, #0 /* no, was it 0? */ 57 1.5.4.2 tls bne 1b /* no, try next byte */ 58 1.5.4.2 tls mov r0, #0 /* yes, set return value to NULL */ 59 1.5.4.2 tls RET /* return */ 60 1.5.4.2 tls 2: sub r0, r0, #1 /* back up by one */ 61 1.5.4.2 tls RET /* return */ 62 1.5.4.2 tls .Lpre_main_loop: 63 1.5.4.2 tls #if defined(_ARM_ARCH_7) 64 1.5.4.2 tls movw r1, #0xfefe /* magic constant; 254 in each byte */ 65 1.5.4.2 tls movt r1, #0xfefe /* magic constant; 254 in each byte */ 66 1.5.4.2 tls #elif defined(_ARM_ARCH_6) 67 1.5.4.2 tls mov r1, #0xfe /* put 254 in low byte */ 68 1.5.4.2 tls orr r1, r1, r1, lsl #8 /* move to next byte */ 69 1.5.4.2 tls orr r1, r1, r1, lsl #16 /* move to next halfword */ 70 1.5.4.2 tls #endif /* _ARM_ARCH_6 */ 71 1.5.4.2 tls orr r2, r2, r2, lsl #8 /* move to next byte */ 72 1.5.4.2 tls orr r2, r2, r2, lsl #16 /* move to next halfword */ 73 1.5.4.2 tls .Lmain_loop: 74 1.5.4.2 tls ldr r3, [r0], #4 /* load next word */ 75 1.5.4.2 tls #if defined(_ARM_ARCH_6) 76 1.5.4.2 tls /* 77 1.5.4.2 tls * Add 254 to each byte using the UQADD8 (unsigned saturating add 8) 78 1.5.4.2 tls * instruction. For every non-NUL byte, the result for that byte will 79 1.5.4.2 tls * become 255. For NUL, it will be 254. When we complement the 80 1.5.4.2 tls * result, if the result is non-0 then we must have encountered a NUL. 81 1.5.4.2 tls */ 82 1.5.4.2 tls uqadd8 ip, r3, r1 /* NUL detection happens here */ 83 1.5.4.2 tls eor r3, r3, r2 /* xor to clear each lane */ 84 1.5.4.2 tls uqadd8 r3, r3, r1 /* char detection happens here */ 85 1.5.4.2 tls and r3, r3, ip /* merge results */ 86 1.5.4.2 tls mvns r3, r3 /* is the complement non-0? */ 87 1.5.4.2 tls beq .Lmain_loop /* no, then keep going */ 88 1.5.4.2 tls 89 1.5.4.2 tls /* 90 1.5.4.2 tls * We've encountered a NUL or a match but we don't know which happened 91 1.5.4.2 tls * first. 92 1.5.4.2 tls */ 93 1.5.4.2 tls teq r2, #0 /* searching for NUL? */ 94 1.5.4.2 tls beq .Lfind_match /* yes, find the match */ 95 1.5.4.2 tls mvns ip, ip /* did we encounter a NUL? */ 96 1.5.4.2 tls beq .Lfind_match /* no, find the match */ 97 1.5.4.2 tls bics r3, r3, ip /* clear match for the NUL(s) */ 98 1.5.4.2 tls beq .Lnomatch /* any left set? if not, no match */ 99 1.5.4.2 tls movs ip, ip, lshi #8 /* replicate NUL bit to other bytes */ 100 1.5.4.2 tls orrne ip, ip, ip, lshi #8 /* replicate NUL bit to other bytes */ 101 1.5.4.2 tls orrne ip, ip, ip, lshi #8 /* replicate NUL bit to other bytes */ 102 1.5.4.2 tls bics r3, r3, ip /* clear any match bits after the NUL */ 103 1.5.4.2 tls beq .Lnomatch /* any left set? if not, no match */ 104 1.5.4.2 tls .Lfind_match: 105 1.5.4.2 tls #ifdef __ARMEL__ 106 1.5.4.2 tls rev r3, r3 /* we want this in BE for the CLZ */ 107 1.5.4.2 tls #endif 108 1.5.4.2 tls clz r3, r3 /* count how many leading zeros */ 109 1.5.4.2 tls add r0, r0, r3, lsr #3 /* divide that by 8 and add to count */ 110 1.5.4.2 tls sub r0, r0, #4 /* compensate for the post-inc */ 111 1.5.4.2 tls RET 112 1.5.4.2 tls .Lnomatch: 113 1.5.4.2 tls mov r0, #0 114 1.5.4.2 tls RET 115 1.5.4.2 tls #else 116 1.5.4.2 tls /* 117 1.5.4.2 tls * No fancy shortcuts so just test each byte lane for a NUL. 118 1.5.4.2 tls * (other tests for NULs in a word take more instructions/cycles). 119 1.5.4.2 tls */ 120 1.5.4.2 tls eor ip, r3, r2 /* xor .. */ 121 1.5.4.2 tls tst r3, #BYTE0 /* is this byte NUL? */ 122 1.5.4.2 tls tstne ip, #BYTE0 /* no, does this byte match? */ 123 1.5.4.2 tls tstne r3, #BYTE1 /* no, is this byte NUL? */ 124 1.5.4.2 tls tstne ip, #BYTE1 /* no, does this byte match? */ 125 1.5.4.2 tls tstne r3, #BYTE2 /* no, is this byte NUL? */ 126 1.5.4.2 tls tstne ip, #BYTE2 /* no, does this byte match? */ 127 1.5.4.2 tls tstne r3, #BYTE3 /* no, is this byte NUL? */ 128 1.5.4.2 tls tstne ip, #BYTE3 /* no, does this byte match? */ 129 1.5.4.2 tls bne .Lmain_loop 130 1.5.4.2 tls 131 1.5.4.2 tls sub r2, r0, #4 /* un post-inc */ 132 1.5.4.2 tls mov r0, #0 /* assume no match */ 133 1.5.4.2 tls 134 1.5.4.2 tls tst ip, #BYTE0 /* does this byte match? */ 135 1.5.4.2 tls moveq r0, r2 /* yes, point to it */ 136 1.5.4.2 tls RETc(eq) /* and return */ 137 1.5.4.2 tls tst r3, #BYTE0 /* is this byte NUL? */ 138 1.5.4.2 tls RETc(eq) /* yes, return NULL */ 139 1.5.4.2 tls 140 1.5.4.2 tls tst ip, #BYTE1 /* does this byte match? */ 141 1.5.4.2 tls addeq r0, r2, #1 /* yes, point to it */ 142 1.5.4.2 tls RETc(eq) /* and return */ 143 1.5.4.2 tls tst r3, #BYTE1 /* is this byte NUL? */ 144 1.5.4.2 tls RETc(eq) /* yes, return NULL */ 145 1.5.4.2 tls 146 1.5.4.2 tls tst ip, #BYTE2 /* does this byte match? */ 147 1.5.4.2 tls addeq r0, r2, #2 /* yes, point to it */ 148 1.5.4.2 tls RETc(eq) /* and return */ 149 1.5.4.2 tls tst r3, #BYTE2 /* is this byte NUL? */ 150 1.5.4.2 tls RETc(eq) /* yes, return NULL */ 151 1.5.4.2 tls 152 1.5.4.2 tls tst ip, #BYTE3 /* does this byte match? */ 153 1.5.4.2 tls addeq r0, r2, #3 /* yes, point to it */ 154 1.5.4.2 tls /* 155 1.5.4.2 tls * Since no NULs and no matches this must be the only case left. 156 1.5.4.2 tls */ 157 1.5.4.2 tls RET /* return */ 158 1.5.4.2 tls #endif /* _ARM_ARCH_6 */ 159 1.5.4.2 tls END(strchr) 160
Indexes created Wed Sep 24 05:09:52 GMT 2025