45 lines
1.3 KiB
C
45 lines
1.3 KiB
C
/* Compute radix independent exponent.
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Copyright (C) 2011 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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Contributed by Ulrich Drepper <drepper@gmail.com>, 2011.
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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 <math.h>
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#include "math_private.h"
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double
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__logb (double x)
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{
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int64_t ix;
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EXTRACT_WORDS64 (ix, x);
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ix &= UINT64_C(0x7fffffffffffffff);
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if (ix == 0)
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return -1.0 / fabs (x);
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unsigned int ex = ix >> 52;
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if (ex == 0x7ff)
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return x * x;
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return ex == 0 ? -1022.0 : (double) (ex - 1023);
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}
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weak_alias (__logb, logb)
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#ifdef NO_LONG_DOUBLE
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strong_alias (__logb, __logbl)
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weak_alias (__logb, logbl)
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#endif
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