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/*
* Copyright 2010 Tilera Corporation. All Rights Reserved.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation, version 2.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
* NON INFRINGEMENT. See the GNU General Public License for
* more details.
*/
#include <linux/types.h>
#include <linux/string.h>
#include <linux/module.h>
char *strchr(const char *s, int c)
{
int z, g;
/* Get an aligned pointer. */
const uintptr_t s_int = (uintptr_t) s;
const uint32_t *p = (const uint32_t *)(s_int & -4);
/* Create four copies of the byte for which we are looking. */
const uint32_t goal = 0x01010101 * (uint8_t) c;
/* Read the first aligned word, but force bytes before the string to
* match neither zero nor goal (we make sure the high bit of each
* byte is 1, and the low 7 bits are all the opposite of the goal
* byte).
*
* Note that this shift count expression works because we know shift
* counts are taken mod 32.
*/
const uint32_t before_mask = (1 << (s_int << 3)) - 1;
uint32_t v = (*p | before_mask) ^ (goal & __insn_shrib(before_mask, 1));
uint32_t zero_matches, goal_matches;
while (1) {
/* Look for a terminating '\0'. */
zero_matches = __insn_seqb(v, 0);
/* Look for the goal byte. */
goal_matches = __insn_seqb(v, goal);
if (__builtin_expect(zero_matches | goal_matches, 0))
break;
v = *++p;
}
z = __insn_ctz(zero_matches);
g = __insn_ctz(goal_matches);
/* If we found c before '\0' we got a match. Note that if c == '\0'
* then g == z, and we correctly return the address of the '\0'
* rather than NULL.
*/
return (g <= z) ? ((char *)p) + (g >> 3) : NULL;
}
EXPORT_SYMBOL(strchr);
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