strchr_arm.S revision 1.2.2.2
1 1.2.2.2 yamt /*- 2 1.2.2.2 yamt * Copyright (c) 2013 The NetBSD Foundation, Inc. 3 1.2.2.2 yamt * All rights reserved. 4 1.2.2.2 yamt * 5 1.2.2.2 yamt * This code is derived from software contributed to The NetBSD Foundation 6 1.2.2.2 yamt * by Matt Thomas of 3am Software Foundry. 7 1.2.2.2 yamt * 8 1.2.2.2 yamt * Redistribution and use in source and binary forms, with or without 9 1.2.2.2 yamt * modification, are permitted provided that the following conditions 10 1.2.2.2 yamt * are met: 11 1.2.2.2 yamt * 1. Redistributions of source code must retain the above copyright 12 1.2.2.2 yamt * notice, this list of conditions and the following disclaimer. 13 1.2.2.2 yamt * 2. Redistributions in binary form must reproduce the above copyright 14 1.2.2.2 yamt * notice, this list of conditions and the following disclaimer in the 15 1.2.2.2 yamt * documentation and/or other materials provided with the distribution. 16 1.2.2.2 yamt * 17 1.2.2.2 yamt * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 18 1.2.2.2 yamt * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 19 1.2.2.2 yamt * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 20 1.2.2.2 yamt * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 21 1.2.2.2 yamt * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 22 1.2.2.2 yamt * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 23 1.2.2.2 yamt * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 24 1.2.2.2 yamt * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 25 1.2.2.2 yamt * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 26 1.2.2.2 yamt * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 27 1.2.2.2 yamt * POSSIBILITY OF SUCH DAMAGE. 28 1.2.2.2 yamt */ 29 1.2.2.2 yamt 30 1.2.2.2 yamt #include <machine/asm.h> 31 1.2.2.2 yamt 32 1.2.2.2 yamt RCSID("$NetBSD: strchr_arm.S,v 1.2.2.2 2013/01/23 00:04:06 yamt Exp $") 33 1.2.2.2 yamt 34 1.2.2.2 yamt #ifdef __ARMEL__ 35 1.2.2.2 yamt #define BYTE0 0x000000ff 36 1.2.2.2 yamt #define BYTE1 0x0000ff00 37 1.2.2.2 yamt #define BYTE2 0x00ff0000 38 1.2.2.2 yamt #define BYTE3 0xff000000 39 1.2.2.2 yamt #define lshi lsl 40 1.2.2.2 yamt #else 41 1.2.2.2 yamt #define BYTE0 0xff000000 42 1.2.2.2 yamt #define BYTE1 0x00ff0000 43 1.2.2.2 yamt #define BYTE2 0x0000ff00 44 1.2.2.2 yamt #define BYTE3 0x000000ff 45 1.2.2.2 yamt #define lshi lsr 46 1.2.2.2 yamt #endif 47 1.2.2.2 yamt 48 1.2.2.2 yamt .text 49 1.2.2.2 yamt ENTRY(strchr) 50 1.2.2.2 yamt and r2, r1, #0xff /* restrict to byte value */ 51 1.2.2.2 yamt 1: tst r0, #3 /* test for word alignment */ 52 1.2.2.2 yamt beq .Lpre_main_loop /* finally word aligned */ 53 1.2.2.2 yamt ldrb r3, [r0], #1 /* load a byte */ 54 1.2.2.2 yamt cmp r3, r2 /* is it a match? */ 55 1.2.2.2 yamt beq 2f /* yes, return current ptr - 1 */ 56 1.2.2.2 yamt teq r3, #0 /* no, was it 0? */ 57 1.2.2.2 yamt bne 1b /* no, try next byte */ 58 1.2.2.2 yamt mov r0, #0 /* yes, set return value to NULL */ 59 1.2.2.2 yamt RET /* return */ 60 1.2.2.2 yamt 2: sub r0, r0, #1 /* back up by one */ 61 1.2.2.2 yamt RET /* return */ 62 1.2.2.2 yamt .Lpre_main_loop: 63 1.2.2.2 yamt #if defined(_ARM_ARCH_7) 64 1.2.2.2 yamt movw r1, #0xfefe /* magic constant; 254 in each byte */ 65 1.2.2.2 yamt movt r1, #0xfefe /* magic constant; 254 in each byte */ 66 1.2.2.2 yamt #elif defined(_ARM_ARCH_6) 67 1.2.2.2 yamt mov r1, #0xfe /* put 254 in low byte */ 68 1.2.2.2 yamt orr r1, r1, r1, lsl #8 /* move to next byte */ 69 1.2.2.2 yamt orr r1, r1, r1, lsl #16 /* move to next halfword */ 70 1.2.2.2 yamt #endif /* _ARM_ARCH_6 */ 71 1.2.2.2 yamt orr r2, r2, r2, lsl #8 /* move to next byte */ 72 1.2.2.2 yamt orr r2, r2, r2, lsl #16 /* move to next halfword */ 73 1.2.2.2 yamt .Lmain_loop: 74 1.2.2.2 yamt ldr r3, [r0], #4 /* load next word */ 75 1.2.2.2 yamt #if defined(_ARM_ARCH_6) 76 1.2.2.2 yamt /* 77 1.2.2.2 yamt * Add 254 to each byte using the UQADD8 (unsigned saturating add 8) 78 1.2.2.2 yamt * instruction. For every non-NUL byte, the result for that byte will 79 1.2.2.2 yamt * become 255. For NUL, it will be 254. When we complement the 80 1.2.2.2 yamt * result, if the result is non-0 then we must have encountered a NUL. 81 1.2.2.2 yamt */ 82 1.2.2.2 yamt uqadd8 ip, r3, r1 /* NUL detection happens here */ 83 1.2.2.2 yamt eor r3, r3, r2 /* xor to clear each lane */ 84 1.2.2.2 yamt uqadd8 r3, r3, r1 /* char detection happens here */ 85 1.2.2.2 yamt and r3, r3, ip /* merge results */ 86 1.2.2.2 yamt mvns r3, r3 /* is the complement non-0? */ 87 1.2.2.2 yamt beq .Lmain_loop /* no, then keep going */ 88 1.2.2.2 yamt 89 1.2.2.2 yamt /* 90 1.2.2.2 yamt * We've encountered a NUL or a match but we don't know which happened 91 1.2.2.2 yamt * first. 92 1.2.2.2 yamt */ 93 1.2.2.2 yamt mvns ip, ip /* did we encounter a NUL? */ 94 1.2.2.2 yamt beq .Lfind_match /* no, find the match */ 95 1.2.2.2 yamt movs ip, ip, lshi #8 /* replicate NUL bit to other bytes */ 96 1.2.2.2 yamt orrne ip, ip, lshi #8 /* replicate NUL bit to other bytes */ 97 1.2.2.2 yamt orrne ip, ip, lshi #8 /* replicate NUL bit to other bytes */ 98 1.2.2.2 yamt bics r3, r3, ip /* clear any match bits after the NUL */ 99 1.2.2.2 yamt beq .Lnomatch /* any left set? if not, no match */ 100 1.2.2.2 yamt .Lfind_match: 101 1.2.2.2 yamt #ifdef __ARMEL__ 102 1.2.2.2 yamt rev r3, r3 /* we want this in BE for the CLZ */ 103 1.2.2.2 yamt #endif 104 1.2.2.2 yamt clz r3, r3 /* count how many leading zeros */ 105 1.2.2.2 yamt add r0, r0, r3, lsr #3 /* divide that by 8 and add to count */ 106 1.2.2.2 yamt sub r0, r0, #4 /* compensate for the post-inc */ 107 1.2.2.2 yamt RET 108 1.2.2.2 yamt .Lnomatch: 109 1.2.2.2 yamt mov r0, #0 110 1.2.2.2 yamt RET 111 1.2.2.2 yamt #else 112 1.2.2.2 yamt /* 113 1.2.2.2 yamt * No fancy shortcuts so just test each byte lane for a NUL. 114 1.2.2.2 yamt * (other tests for NULs in a word take more instructions/cycles). 115 1.2.2.2 yamt */ 116 1.2.2.2 yamt eor ip, r3, r2 /* xor .. */ 117 1.2.2.2 yamt tst r3, #BYTE0 /* is this byte NUL? */ 118 1.2.2.2 yamt tstne ip, #BYTE0 /* no, does this byte match? */ 119 1.2.2.2 yamt tstne r3, #BYTE1 /* no, is this byte NUL? */ 120 1.2.2.2 yamt tstne ip, #BYTE1 /* no, does this byte match? */ 121 1.2.2.2 yamt tstne r3, #BYTE2 /* no, is this byte NUL? */ 122 1.2.2.2 yamt tstne ip, #BYTE2 /* no, does this byte match? */ 123 1.2.2.2 yamt tstne r3, #BYTE3 /* no, is this byte NUL? */ 124 1.2.2.2 yamt tstne ip, #BYTE3 /* no, does this byte match? */ 125 1.2.2.2 yamt bne .Lmain_loop 126 1.2.2.2 yamt 127 1.2.2.2 yamt sub r2, r0, #4 /* un post-inc */ 128 1.2.2.2 yamt mov r0, #0 /* assume no match */ 129 1.2.2.2 yamt 130 1.2.2.2 yamt tst ip, #BYTE0 /* does this byte match? */ 131 1.2.2.2 yamt moveq r0, r2 /* yes, point to it */ 132 1.2.2.2 yamt RETc(eq) /* and return */ 133 1.2.2.2 yamt tst r3, #BYTE0 /* is this byte NUL? */ 134 1.2.2.2 yamt RETc(eq) /* yes, return NULL */ 135 1.2.2.2 yamt 136 1.2.2.2 yamt tst ip, #BYTE1 /* does this byte match? */ 137 1.2.2.2 yamt addeq r0, r2, #1 /* yes, point to it */ 138 1.2.2.2 yamt RETc(eq) /* and return */ 139 1.2.2.2 yamt tst r3, #BYTE1 /* is this byte NUL? */ 140 1.2.2.2 yamt RETc(eq) /* yes, return NULL */ 141 1.2.2.2 yamt 142 1.2.2.2 yamt tst ip, #BYTE2 /* does this byte match? */ 143 1.2.2.2 yamt addeq r0, r2, #2 /* yes, point to it */ 144 1.2.2.2 yamt RETc(eq) /* and return */ 145 1.2.2.2 yamt tst r3, #BYTE2 /* is this byte NUL? */ 146 1.2.2.2 yamt RETc(eq) /* yes, return NULL */ 147 1.2.2.2 yamt 148 1.2.2.2 yamt tst ip, #BYTE3 /* does this byte match? */ 149 1.2.2.2 yamt addeq r0, r2, #3 /* yes, point to it */ 150 1.2.2.2 yamt /* 151 1.2.2.2 yamt * Since no NULs and no matches this must be the only case left. 152 1.2.2.2 yamt */ 153 1.2.2.2 yamt RET /* return */ 154 1.2.2.2 yamt #endif /* _ARM_ARCH_6 */ 155 1.2.2.2 yamt END(strchr) 156
Indexes created Thu Sep 25 16:09:42 GMT 2025