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18aecc2b CM |
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> | |
1efea40d | 18 | #include "string-endian.h" |
18aecc2b CM |
19 | |
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. */ | |
c53c70a9 | 29 | const uint64_t goal = copy_byte(c); |
18aecc2b CM |
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). | |
18aecc2b | 35 | */ |
1efea40d CM |
36 | const uint64_t before_mask = MASK(s_int); |
37 | uint64_t v = (*p | before_mask) ^ (goal & __insn_v1shrui(before_mask, 1)); | |
18aecc2b CM |
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 | ||
1efea40d CM |
53 | z = CFZ(zero_matches); |
54 | g = CFZ(goal_matches); | |
18aecc2b CM |
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); |