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/* Compute 2^x.
Copyright (C) 2012-2015 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
#include <math.h>
#include <math_private.h>
#include <float.h>
/* To avoid spurious underflows, use this definition to treat IBM long
double as approximating an IEEE-style format. */
#if LDBL_MANT_DIG == 106
# undef LDBL_EPSILON
# define LDBL_EPSILON 0x1p-106L
#endif
long double
__ieee754_exp2l (long double x)
{
if (__glibc_likely (isless (x, (long double) LDBL_MAX_EXP)))
{
if (__builtin_expect (isgreaterequal (x, (long double) (LDBL_MIN_EXP
- LDBL_MANT_DIG
- 1)), 1))
{
int intx = (int) x;
long double fractx = x - intx;
long double result;
if (fabsl (fractx) < LDBL_EPSILON / 4.0L)
result = __scalbnl (1.0L + fractx, intx);
else
result = __scalbnl (__ieee754_expl (M_LN2l * fractx), intx);
if (result < LDBL_MIN)
{
long double force_underflow = result * result;
math_force_eval (force_underflow);
}
return result;
}
else
{
/* Underflow or exact zero. */
if (isinf (x))
return 0;
else
return LDBL_MIN * LDBL_MIN;
}
}
else
/* Infinity, NaN or overflow. */
return LDBL_MAX * x;
}
strong_alias (__ieee754_exp2l, __exp2l_finite)
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