projects / deliverable / linux.git / blame
| Commit | Line | Data |
|---|---|---|
| 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> | |
| 18 | ||
| 19 | #undef strchr | |
| 20 | ||
| 21 | char *strchr(const char *s, int c) | |
| 22 | { | |
| 23 | int z, g; | |
| 24 | ||
| 25 | /* Get an aligned pointer. */ | |
| 26 | const uintptr_t s_int = (uintptr_t) s; | |
| 27 | const uint64_t *p = (const uint64_t *)(s_int & -8); | |
| 28 | ||
| 29 | /* Create eight copies of the byte for which we are looking. */ | |
| 30 | const uint64_t goal = 0x0101010101010101ULL * (uint8_t) c; | |
| 31 | ||
| 32 | /* Read the first aligned word, but force bytes before the string to | |
| 33 | * match neither zero nor goal (we make sure the high bit of each | |
| 34 | * byte is 1, and the low 7 bits are all the opposite of the goal | |
| 35 | * byte). | |
| 36 | * | |
| 37 | * Note that this shift count expression works because we know shift | |
| 38 | * counts are taken mod 64. | |
| 39 | */ | |
| 40 | const uint64_t before_mask = (1ULL << (s_int << 3)) - 1; | |
| 41 | uint64_t v = (*p | before_mask) ^ | |
| 42 | (goal & __insn_v1shrsi(before_mask, 1)); | |
| 43 | ||
| 44 | uint64_t zero_matches, goal_matches; | |
| 45 | while (1) { | |
| 46 | /* Look for a terminating '\0'. */ | |
| 47 | zero_matches = __insn_v1cmpeqi(v, 0); | |
| 48 | ||
| 49 | /* Look for the goal byte. */ | |
| 50 | goal_matches = __insn_v1cmpeq(v, goal); | |
| 51 | ||
| 52 | if (__builtin_expect((zero_matches | goal_matches) != 0, 0)) | |
| 53 | break; | |
| 54 | ||
| 55 | v = *++p; | |
| 56 | } | |
| 57 | ||
| 58 | z = __insn_ctz(zero_matches); | |
| 59 | g = __insn_ctz(goal_matches); | |
| 60 | ||
| 61 | /* If we found c before '\0' we got a match. Note that if c == '\0' | |
| 62 | * then g == z, and we correctly return the address of the '\0' | |
| 63 | * rather than NULL. | |
| 64 | */ | |
| 65 | return (g <= z) ? ((char *)p) + (g >> 3) : NULL; | |
| 66 | } | |
| 67 | EXPORT_SYMBOL(strchr); |