memchr.S (1411B)
1/* SPDX-License-Identifier: GPL-2.0-only */ 2/* 3 * Copyright (C) 2021 Arm Ltd. 4 */ 5 6#include <linux/linkage.h> 7#include <asm/assembler.h> 8 9/* 10 * Find a character in an area of memory. 11 * 12 * Parameters: 13 * x0 - buf 14 * x1 - c 15 * x2 - n 16 * Returns: 17 * x0 - address of first occurrence of 'c' or 0 18 */ 19 20#define L(label) .L ## label 21 22#define REP8_01 0x0101010101010101 23#define REP8_7f 0x7f7f7f7f7f7f7f7f 24 25#define srcin x0 26#define chrin w1 27#define cntin x2 28 29#define result x0 30 31#define wordcnt x3 32#define rep01 x4 33#define repchr x5 34#define cur_word x6 35#define cur_byte w6 36#define tmp x7 37#define tmp2 x8 38 39 .p2align 4 40 nop 41SYM_FUNC_START(__pi_memchr) 42 and chrin, chrin, #0xff 43 lsr wordcnt, cntin, #3 44 cbz wordcnt, L(byte_loop) 45 mov rep01, #REP8_01 46 mul repchr, x1, rep01 47 and cntin, cntin, #7 48L(word_loop): 49 ldr cur_word, [srcin], #8 50 sub wordcnt, wordcnt, #1 51 eor cur_word, cur_word, repchr 52 sub tmp, cur_word, rep01 53 orr tmp2, cur_word, #REP8_7f 54 bics tmp, tmp, tmp2 55 b.ne L(found_word) 56 cbnz wordcnt, L(word_loop) 57L(byte_loop): 58 cbz cntin, L(not_found) 59 ldrb cur_byte, [srcin], #1 60 sub cntin, cntin, #1 61 cmp cur_byte, chrin 62 b.ne L(byte_loop) 63 sub srcin, srcin, #1 64 ret 65L(found_word): 66CPU_LE( rev tmp, tmp) 67 clz tmp, tmp 68 sub tmp, tmp, #64 69 add result, srcin, tmp, asr #3 70 ret 71L(not_found): 72 mov result, #0 73 ret 74SYM_FUNC_END(__pi_memchr) 75SYM_FUNC_ALIAS_WEAK(memchr, __pi_memchr) 76EXPORT_SYMBOL_NOKASAN(memchr)