math/e_exp2l.c

   1 /* Compute 2^x.
   2    Copyright (C) 2012-2015 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <math.h>
  20 #include <math_private.h>
  21 #include <float.h>
  22
  23 long double
  24 __ieee754_exp2l (long double x)
  25 {
  26   if (__glibc_likely (isless (x, (long double) LDBL_MAX_EXP)))
  27     {
  28       if (__builtin_expect (isgreaterequal (x, (long double) (LDBL_MIN_EXP
  29                                                               - LDBL_MANT_DIG
  30                                                               - 1)), 1))
  31         {
  32           int intx = (int) x;
  33           long double fractx = x - intx;
  34           return __scalbnl (__ieee754_expl (M_LN2l * fractx), intx);
  35         }
  36       else
  37         {
  38           /* Underflow or exact zero.  */
  39           if (__isinfl (x))
  40             return 0;
  41           else
  42             return LDBL_MIN * LDBL_MIN;
  43         }
  44     }
  45   else
  46     /* Infinity, NaN or overflow.  */
  47     return LDBL_MAX * x;
  48 }
  49 strong_alias (__ieee754_exp2l, __exp2l_finite)