math/w_pow_compat.c

   1 /* Copyright (C) 2011-2017 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Ulrich Drepper <drepper@gmail.com>, 2011.
   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
  22
  23 /* wrapper pow */
  24 double
  25 __pow (double x, double y)
  26 {
  27   double z = __ieee754_pow (x, y);
  28   if (__glibc_unlikely (!isfinite (z)))
  29     {
  30       if (_LIB_VERSION != _IEEE_)
  31         {
  32           if (isfinite (x) && isfinite (y))
  33             {
  34               if (isnan (z))
  35                 /* pow neg**non-int */
  36                 return __kernel_standard (x, y, 24);
  37               else if (x == 0.0 && y < 0.0)
  38                 {
  39                   if (signbit (x) && signbit (z))
  40                     /* pow(-0.0,negative) */
  41                     return __kernel_standard (x, y, 23);
  42                   else
  43                     /* pow(+0.0,negative) */
  44                     return __kernel_standard (x, y, 43);
  45                 }
  46               else
  47                 /* pow overflow */
  48                 return __kernel_standard (x, y, 21);
  49             }
  50         }
  51     }
  52   else if (__builtin_expect (z == 0.0, 0)
  53            && isfinite (x) && x != 0 && isfinite (y)
  54            && _LIB_VERSION != _IEEE_)
  55     /* pow underflow */
  56     return __kernel_standard (x, y, 22);
  57
  58   return z;
  59 }
  60 weak_alias (__pow, pow)
  61 #ifdef NO_LONG_DOUBLE
  62 strong_alias (__pow, __powl)
  63 weak_alias (__pow, powl)
  64 #endif