math/w_pow.c

   1 /* Copyright (C) 2011-2015 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 (isnan (x))
  33             {
  34               if (y == 0.0)
  35                 /* pow(NaN,0.0) */
  36                 return __kernel_standard (x, y, 42);
  37             }
  38           else if (isfinite (x) && isfinite (y))
  39             {
  40               if (isnan (z))
  41                 /* pow neg**non-int */
  42                 return __kernel_standard (x, y, 24);
  43               else if (x == 0.0 && y < 0.0)
  44                 {
  45                   if (signbit (x) && signbit (z))
  46                     /* pow(-0.0,negative) */
  47                     return __kernel_standard (x, y, 23);
  48                   else
  49                     /* pow(+0.0,negative) */
  50                     return __kernel_standard (x, y, 43);
  51                 }
  52               else
  53                 /* pow overflow */
  54                 return __kernel_standard (x, y, 21);
  55             }
  56         }
  57     }
  58   else if (__builtin_expect (z == 0.0, 0) && isfinite (x) && isfinite (y)
  59            && _LIB_VERSION != _IEEE_)
  60     {
  61       if (x == 0.0)
  62         {
  63           if (y == 0.0)
  64             /* pow(0.0,0.0) */
  65             return __kernel_standard (x, y, 20);
  66         }
  67       else
  68         /* pow underflow */
  69         return __kernel_standard (x, y, 22);
  70     }
  71
  72   return z;
  73 }
  74 weak_alias (__pow, pow)
  75 #ifdef NO_LONG_DOUBLE
  76 strong_alias (__pow, __powl)
  77 weak_alias (__pow, powl)
  78 #endif