glibc/math/w_pow.c

/* Copyright (C) 2011-2015 Free Software Foundation, Inc.
   This file is part of the GNU C Library.
   Contributed by Ulrich Drepper <drepper@gmail.com>, 2011.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, see
   <http://www.gnu.org/licenses/>.  */

#include <math.h>
#include <math_private.h>


/* wrapper pow */
double
__pow (double x, double y)
{
  double z = __ieee754_pow (x, y);
  if (__glibc_unlikely (!__finite (z)))
    {
      if (_LIB_VERSION != _IEEE_)
	{
	  if (__isnan (x))
	    {
	      if (y == 0.0)
		/* pow(NaN,0.0) */
		return __kernel_standard (x, y, 42);
	    }
	  else if (__finite (x) && __finite (y))
	    {
	      if (__isnan (z))
		/* pow neg**non-int */
		return __kernel_standard (x, y, 24);
	      else if (x == 0.0 && y < 0.0)
		{
		  if (signbit (x) && signbit (z))
		    /* pow(-0.0,negative) */
		    return __kernel_standard (x, y, 23);
		  else
		    /* pow(+0.0,negative) */
		    return __kernel_standard (x, y, 43);
		}
	      else
		/* pow overflow */
		return __kernel_standard (x, y, 21);
	    }
	}
    }
  else if (__builtin_expect (z == 0.0, 0) && __finite (x) && __finite (y)
	   && _LIB_VERSION != _IEEE_)
    {
      if (x == 0.0)
	{
	  if (y == 0.0)
	    /* pow(0.0,0.0) */
	    return __kernel_standard (x, y, 20);
	}
      else
	/* pow underflow */
	return __kernel_standard (x, y, 22);
    }

  return z;
}
weak_alias (__pow, pow)
#ifdef NO_LONG_DOUBLE
strong_alias (__pow, __powl)
weak_alias (__pow, powl)
#endif