46 lines
1.4 KiB
C
46 lines
1.4 KiB
C
/* ffs -- find first set bit in a word, counted from least significant end.
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For Intel 80x86, x>=3.
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Copyright (C) 1991, 1992, 1993, 1994 Free Software Foundation, Inc.
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Contributed by Torbjorn Granlund (tege@sics.se).
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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 Library General Public License as
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published by the Free Software Foundation; either version 2 of the
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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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Library General Public License for more details.
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You should have received a copy of the GNU Library General Public
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License along with the GNU C Library; see the file COPYING.LIB. If
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not, write to the Free Software Foundation, Inc., 675 Mass Ave,
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Cambridge, MA 02139, USA. */
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#include <ansidecl.h>
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#include <string.h>
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#undef ffs
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#ifdef __GNUC__
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int
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DEFUN(ffs, (x), int x)
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{
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int cnt;
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int tmp;
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asm ("xorl %0,%0\n" /* Set CNT to zero. */
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"bsfl %2,%1\n" /* Count low bits in X and store in %1. */
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"jz nonzero\n" /* Jump if OK, i.e. X was non-zero. */
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"leal 1(%1),%0\n" /* Return bsfl-result plus one on %0. */
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"nonzero:" : "=&a" (cnt), "=r" (tmp) : "rm" (x));
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return cnt;
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}
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#else
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#include <sysdeps/generic/ffs.c>
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#endif
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