1 /*
2 * Copyright 2011 Tilera Corporation. All Rights Reserved.
3 *
4 * This program is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU General Public License
6 * as published by the Free Software Foundation, version 2.
7 *
8 * This program is distributed in the hope that it will be useful, but
9 * WITHOUT ANY WARRANTY; without even the implied warranty of
10 * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
11 * NON INFRINGEMENT. See the GNU General Public License for
12 * more details.
13 */
14
15 #include <linux/types.h>
16 #include <linux/string.h>
17 #include <linux/module.h>
18 #include "string-endian.h"
19
strchr(const char * s,int c)20 char *strchr(const char *s, int c)
21 {
22 int z, g;
23
24 /* Get an aligned pointer. */
25 const uintptr_t s_int = (uintptr_t) s;
26 const uint64_t *p = (const uint64_t *)(s_int & -8);
27
28 /* Create eight copies of the byte for which we are looking. */
29 const uint64_t goal = copy_byte(c);
30
31 /* Read the first aligned word, but force bytes before the string to
32 * match neither zero nor goal (we make sure the high bit of each
33 * byte is 1, and the low 7 bits are all the opposite of the goal
34 * byte).
35 */
36 const uint64_t before_mask = MASK(s_int);
37 uint64_t v = (*p | before_mask) ^ (goal & __insn_v1shrui(before_mask, 1));
38
39 uint64_t zero_matches, goal_matches;
40 while (1) {
41 /* Look for a terminating '\0'. */
42 zero_matches = __insn_v1cmpeqi(v, 0);
43
44 /* Look for the goal byte. */
45 goal_matches = __insn_v1cmpeq(v, goal);
46
47 if (__builtin_expect((zero_matches | goal_matches) != 0, 0))
48 break;
49
50 v = *++p;
51 }
52
53 z = CFZ(zero_matches);
54 g = CFZ(goal_matches);
55
56 /* If we found c before '\0' we got a match. Note that if c == '\0'
57 * then g == z, and we correctly return the address of the '\0'
58 * rather than NULL.
59 */
60 return (g <= z) ? ((char *)p) + (g >> 3) : NULL;
61 }
62 EXPORT_SYMBOL(strchr);
63