40 lines
1.3 KiB
C
40 lines
1.3 KiB
C
/* ffs -- find first set bit in a word, counted from least significant end.
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For AMD x86-64.
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This file is part of the GNU C Library.
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Copyright (C) 1991,92,93,94,97,98,2001,2004 Free Software Foundation, Inc.
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Contributed by Ulrich Drepper <drepper@cygnus.com>.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, write to the Free
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Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
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02111-1307 USA. */
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#include <string.h>
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#undef ffs
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int
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__ffs (int x)
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{
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int cnt;
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int tmp;
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asm ("bsfl %2,%0\n" /* Count low bits in X and store in %1. */
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"cmovel %1,%0\n" /* If number was zero, use -1 as result. */
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: "=&r" (cnt), "=r" (tmp) : "rm" (x), "1" (-1));
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return cnt + 1;
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}
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weak_alias (__ffs, ffs)
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libc_hidden_builtin_def (ffs)
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