libm/w_pow.c

   1 /* Copyright (C) 2011-2016 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 #if defined(__UCLIBC_HAS_FENV__)
  28         double z = __ieee754_pow (x, y);
  29   if (__builtin_expect (!isfinite (z), 0))
  30     {
  31       if (_LIB_VERSION != _IEEE_)
  32         {
  33           if (isnan (x))
  34             {
  35               if (y == 0.0)
  36                 /* pow(NaN,0.0) */
  37                 return __kernel_standard (x, y, 42);
  38             }
  39           else if (isfinite (x) && isfinite (y))
  40             {
  41               if (isnan (z))
  42                 /* pow neg**non-int */
  43                 return __kernel_standard (x, y, 24);
  44               else if (x == 0.0 && y < 0.0)
  45                 {
  46                   if (signbit (x) && signbit (z))
  47                     /* pow(-0.0,negative) */
  48                     return __kernel_standard (x, y, 23);
  49                   else
  50                     /* pow(+0.0,negative) */
  51                     return __kernel_standard (x, y, 43);
  52                 }
  53               else
  54                 /* pow overflow */
  55                 return __kernel_standard (x, y, 21);
  56             }
  57         }
  58     }
  59   else if (__builtin_expect (z == 0.0, 0) && isfinite (x) && isfinite (y)
  60            && _LIB_VERSION != _IEEE_)
  61     {
  62       if (x == 0.0)
  63         {
  64           if (y == 0.0)
  65             /* pow(0.0,0.0) */
  66             return __kernel_standard (x, y, 20);
  67         }
  68       else
  69         /* pow underflow */
  70         return __kernel_standard (x, y, 22);
  71     }
  72
  73         return z;
  74 #else
  75         return __ieee754_pow (x, y);
  76 #endif
  77 }
  78 libm_hidden_def(pow)