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58 lines
1.9 KiB
C
58 lines
1.9 KiB
C
/* Copyright (C) 1991-2025 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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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, see
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<https://www.gnu.org/licenses/>. */
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#include <limits.h>
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#define ffsl __something_else
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#include <string.h>
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#undef ffs
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#include <math-use-builtins.h>
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/* Find the first bit set in I. */
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int
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__ffs (int i)
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{
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#if USE_FFS_BUILTIN
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return __builtin_ffs (i);
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#else
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static const unsigned char table[] =
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{
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0,1,2,2,3,3,3,3,4,4,4,4,4,4,4,4,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,
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6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
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7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
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7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
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8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,
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8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,
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8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,
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8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8
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};
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unsigned int a;
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unsigned int x = i & -i;
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a = x <= 0xffff ? (x <= 0xff ? 0 : 8) : (x <= 0xffffff ? 16 : 24);
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return table[x >> a] + a;
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#endif
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}
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weak_alias (__ffs, ffs)
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libc_hidden_def (__ffs)
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libc_hidden_builtin_def (ffs)
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#if ULONG_MAX == UINT_MAX
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#undef ffsl
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weak_alias (__ffs, ffsl)
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#endif
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