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