mirror of
https://sourceware.org/git/glibc.git
synced 2024-11-14 01:00:07 +00:00
63 lines
1.8 KiB
C
63 lines
1.8 KiB
C
/* Compute 2^x.
|
|
Copyright (C) 2012-2016 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);
|
|
math_check_force_underflow_nonneg (result);
|
|
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)
|