| /* Copyright (C) 2011-2014 Free Software Foundation, Inc. |
| This file is part of the GNU C Library. |
| Contributed by Chris Metcalf <cmetcalf@tilera.com>, 2011. |
| |
| The GNU C Library is free software; you can redistribute it and/or |
| modify it under the terms of the GNU Lesser General Public |
| License as published by the Free Software Foundation; either |
| version 2.1 of the License, or (at your option) any later version. |
| |
| The GNU C Library 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. See the GNU |
| Lesser General Public License for more details. |
| |
| You should have received a copy of the GNU Lesser General Public |
| License along with the GNU C Library. If not, see |
| <http://www.gnu.org/licenses/>. */ |
| |
| #include <string.h> |
| #include <stdint.h> |
| |
| char * |
| strrchr (const char *s, int c) |
| { |
| /* 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)); |
| const char *found = NULL; |
| 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 we found the goal, record the last offset. */ |
| if (__builtin_expect (goal_matches != 0, 0)) |
| { |
| if (__builtin_expect (zero_matches != 0, 0)) |
| { |
| /* Clear any goal after the first zero. */ |
| int first_nul = __insn_ctz (zero_matches); |
| /* The number of top bits we need to clear is |
| 32 - (first_nul + 8). */ |
| int shift_amt = (24 - first_nul); |
| goal_matches <<= shift_amt; |
| goal_matches >>= shift_amt; |
| } |
| if (__builtin_expect (goal_matches != 0, 1)) |
| found = ((char *) p) + 3 - (__insn_clz (goal_matches) >> 3); |
| } |
| |
| if (__builtin_expect (zero_matches != 0, 0)) |
| return (char *) found; |
| |
| v = *++p; |
| } |
| } |
| weak_alias (strrchr, rindex) |
| libc_hidden_builtin_def (strrchr) |