LXR linux/arch/arm64/lib/memchr.S

   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_WEAK_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)
  75EXPORT_SYMBOL_NOKASAN(memchr)
  76