1 | /* ffs -- find first set bit in a word, counted from least significant end. |
2 | For Intel 80x86, x>=6. |
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 ("bsfl %2,%0\n" /* Count low bits in X and store in %1. */ |
34 | "cmovel %1,%0\n" /* If number was zero, use -1 as result. */ |
35 | : "=&r" (cnt), "=r" (tmp) : "rm" (x), "1" (-1)); |
36 | |
37 | return cnt + 1; |
38 | } |
39 | weak_alias (__ffs, ffs) |
40 | libc_hidden_def (__ffs) |
41 | libc_hidden_builtin_def (ffs) |
42 | #undef ffsl |
43 | weak_alias (__ffs, ffsl) |
44 | |
45 | #else |
46 | #include <string/ffs.c> |
47 | #endif |
48 | |