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 #include <math-svid-compat.h>
  22
  23
  24 /* wrapper pow */
  25 double
  26 __pow (double x, double y)
  27 {
  28   double z = __ieee754_pow (x, y);
  29   if (__glibc_unlikely (!isfinite (z)))
  30     {
  31       if (_LIB_VERSION != _IEEE_)
  32         {
  33           if (isfinite (x) && isfinite (y))
  34             {
  35               if (isnan (z))
  36                 /* pow neg**non-int */
  37                 return __kernel_standard (x, y, 24);
  38               else if (x == 0.0 && y < 0.0)
  39                 {
  40                   if (signbit (x) && signbit (z))
  41                     /* pow(-0.0,negative) */
  42                     return __kernel_standard (x, y, 23);
  43                   else
  44                     /* pow(+0.0,negative) */
  45                     return __kernel_standard (x, y, 43);
  46                 }
  47               else
  48                 /* pow overflow */
  49                 return __kernel_standard (x, y, 21);
  50             }
  51         }
  52     }
  53   else if (__builtin_expect (z == 0.0, 0)
  54            && isfinite (x) && x != 0 && isfinite (y)
  55            && _LIB_VERSION != _IEEE_)
  56     /* pow underflow */
  57     return __kernel_standard (x, y, 22);
  58
  59   return z;
  60 }
  61 weak_alias (__pow, pow)
  62 #ifdef NO_LONG_DOUBLE
  63 strong_alias (__pow, __powl)
  64 weak_alias (__pow, powl)
  65 #endif