| 1 | /* ffs -- find first set bit in a word, counted from least significant end. |
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| 2 | For Intel 80x86, x>=3. |
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| 3 | This file is part of the GNU C Library. |
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| 4 | Copyright (C) 1991-2022 Free Software Foundation, Inc. |
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| 5 | |
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| 6 | The GNU C Library is free software; you can redistribute it and/or |
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| 7 | modify it under the terms of the GNU Lesser General Public |
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| 8 | License as published by the Free Software Foundation; either |
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| 9 | version 2.1 of the License, or (at your option) any later version. |
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| 10 | |
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| 11 | The GNU C Library is distributed in the hope that it will be useful, |
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| 12 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
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| 13 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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| 14 | Lesser General Public License for more details. |
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| 15 | |
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| 16 | You should have received a copy of the GNU Lesser General Public |
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| 17 | License along with the GNU C Library; if not, see |
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| 18 | <https://www.gnu.org/licenses/>. */ |
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| 19 | |
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| 20 | #define ffsl __something_else |
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| 21 | #include <string.h> |
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| 22 | |
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| 23 | #undef ffs |
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| 24 | |
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| 25 | #ifdef __GNUC__ |
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| 26 | |
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| 27 | int |
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| 28 | __ffs (int x) |
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| 29 | { |
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| 30 | int cnt; |
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| 31 | int tmp; |
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| 32 | |
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| 33 | asm ("xorl %0,%0\n" /* Set CNT to zero. */ |
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| 34 | "bsfl %2,%1\n" /* Count low bits in X and store in %1. */ |
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| 35 | "jz 1f\n" /* Jump if OK, i.e. X was non-zero. */ |
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| 36 | "leal 1(%1),%0\n" /* Return bsfl-result plus one on %0. */ |
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| 37 | "1:" : "=&a" (cnt), "=r" (tmp) : "rm" (x)); |
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| 38 | |
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| 39 | return cnt; |
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| 40 | } |
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| 41 | weak_alias (__ffs, ffs) |
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| 42 | libc_hidden_def (__ffs) |
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| 43 | libc_hidden_builtin_def (ffs) |
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| 44 | #undef ffsl |
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| 45 | weak_alias (__ffs, ffsl) |
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| 46 | |
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| 47 | #else |
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| 48 | #include <string/ffs.c> |
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| 49 | #endif |
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| 50 | |
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