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) 1991-2024 Free Software Foundation, Inc. |
5 | |
6 | The GNU C Library is free software; you can redistribute it and/or |
7 | modify it under the terms of the GNU Lesser General Public |
8 | License as published by the Free Software Foundation; either |
9 | version 2.1 of the License, or (at your option) any later version. |
10 | |
11 | The GNU C Library is distributed in the hope that it will be useful, |
12 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
13 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
14 | Lesser General Public License for more details. |
15 | |
16 | You should have received a copy of the GNU Lesser General Public |
17 | License along with the GNU C Library; if not, see |
18 | <https://www.gnu.org/licenses/>. */ |
19 | |
20 | #define ffsl __something_else |
21 | #include <string.h> |
22 | |
23 | #undef ffs |
24 | |
25 | #ifdef __GNUC__ |
26 | |
27 | int |
28 | __ffs (int x) |
29 | { |
30 | int cnt; |
31 | int tmp; |
32 | |
33 | asm ("xorl %0,%0\n" /* Set CNT to zero. */ |
34 | "bsfl %2,%1\n" /* Count low bits in X and store in %1. */ |
35 | "jz 1f\n" /* Jump if OK, i.e. X was non-zero. */ |
36 | "leal 1(%1),%0\n" /* Return bsfl-result plus one on %0. */ |
37 | "1:" : "=&a" (cnt), "=r" (tmp) : "rm" (x)); |
38 | |
39 | return cnt; |
40 | } |
41 | weak_alias (__ffs, ffs) |
42 | libc_hidden_def (__ffs) |
43 | libc_hidden_builtin_def (ffs) |
44 | #undef ffsl |
45 | weak_alias (__ffs, ffsl) |
46 | |
47 | #else |
48 | #include <string/ffs.c> |
49 | #endif |
50 | |