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