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28f540f4 RM |
1 | /* ffs -- find first set bit in a word, counted from least significant end. |
2 | For Intel 80x86, x>=3. | |
ebbad4cc | 3 | This file is part of the GNU C Library. |
b168057a | 4 | Copyright (C) 1991-2015 Free Software Foundation, Inc. |
28f540f4 RM |
5 | Contributed by Torbjorn Granlund (tege@sics.se). |
6 | ||
ebbad4cc | 7 | The GNU C Library is free software; you can redistribute it and/or |
41bdb6e2 AJ |
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. | |
28f540f4 | 11 | |
ebbad4cc UD |
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 | |
41bdb6e2 | 15 | Lesser General Public License for more details. |
28f540f4 | 16 | |
41bdb6e2 | 17 | You should have received a copy of the GNU Lesser General Public |
59ba27a6 PE |
18 | License along with the GNU C Library; if not, see |
19 | <http://www.gnu.org/licenses/>. */ | |
28f540f4 | 20 | |
bdd421cc | 21 | #define ffsl __something_else |
28f540f4 RM |
22 | #include <string.h> |
23 | ||
24 | #undef ffs | |
25 | ||
26 | #ifdef __GNUC__ | |
27 | ||
28 | int | |
bd2260a2 | 29 | __ffs (int x) |
28f540f4 RM |
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. */ | |
ebbad4cc | 36 | "jz 1f\n" /* Jump if OK, i.e. X was non-zero. */ |
28f540f4 | 37 | "leal 1(%1),%0\n" /* Return bsfl-result plus one on %0. */ |
ebbad4cc | 38 | "1:" : "=&a" (cnt), "=r" (tmp) : "rm" (x)); |
28f540f4 RM |
39 | |
40 | return cnt; | |
41 | } | |
19212f87 | 42 | weak_alias (__ffs, ffs) |
5bb43a43 | 43 | libc_hidden_def (__ffs) |
2dd18ce2 | 44 | libc_hidden_builtin_def (ffs) |
bdd421cc UD |
45 | #undef ffsl |
46 | weak_alias (__ffs, ffsl) | |
28f540f4 RM |
47 | |
48 | #else | |
2826ac7e | 49 | #include <string/ffs.c> |
28f540f4 | 50 | #endif |