| xf.li | bdd93d5 | 2023-05-12 07:10:14 -0700 | [diff] [blame^] | 1 | /* ffs -- find first set bit in a word, counted from least significant end. |
| 2 | For Intel 80x86, x>=3. |
| 3 | This file is part of the GNU C Library. |
| 4 | Copyright (C) 1991-2016 Free Software Foundation, Inc. |
| 5 | Contributed by Torbjorn Granlund (tege@sics.se). |
| 6 | |
| 7 | The GNU C Library is free software; you can redistribute it and/or |
| 8 | modify it under the terms of the GNU Lesser General Public |
| 9 | License as published by the Free Software Foundation; either |
| 10 | version 2.1 of the License, or (at your option) any later version. |
| 11 | |
| 12 | The GNU C Library is distributed in the hope that it will be useful, |
| 13 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 14 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| 15 | Lesser General Public License for more details. |
| 16 | |
| 17 | You should have received a copy of the GNU Lesser General Public |
| 18 | License along with the GNU C Library; if not, see |
| 19 | <http://www.gnu.org/licenses/>. */ |
| 20 | |
| 21 | #define ffsl __something_else |
| 22 | #include <string.h> |
| 23 | |
| 24 | #undef ffs |
| 25 | |
| 26 | #ifdef __GNUC__ |
| 27 | |
| 28 | int |
| 29 | __ffs (int x) |
| 30 | { |
| 31 | int cnt; |
| 32 | int tmp; |
| 33 | |
| 34 | asm ("xorl %0,%0\n" /* Set CNT to zero. */ |
| 35 | "bsfl %2,%1\n" /* Count low bits in X and store in %1. */ |
| 36 | "jz 1f\n" /* Jump if OK, i.e. X was non-zero. */ |
| 37 | "leal 1(%1),%0\n" /* Return bsfl-result plus one on %0. */ |
| 38 | "1:" : "=&a" (cnt), "=r" (tmp) : "rm" (x)); |
| 39 | |
| 40 | return cnt; |
| 41 | } |
| 42 | weak_alias (__ffs, ffs) |
| 43 | libc_hidden_def (__ffs) |
| 44 | libc_hidden_builtin_def (ffs) |
| 45 | #undef ffsl |
| 46 | weak_alias (__ffs, ffsl) |
| 47 | |
| 48 | #else |
| 49 | #include <string/ffs.c> |
| 50 | #endif |