Blame math/w_pow_compat.c

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/* Copyright (C) 2011-2018 Free Software Foundation, Inc.
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   This file is part of the GNU C Library.
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   Contributed by Ulrich Drepper <drepper@gmail.com>, 2011.
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   The GNU C Library is free software; you can redistribute it and/or
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   modify it under the terms of the GNU Lesser General Public
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   License as published by the Free Software Foundation; either
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   version 2.1 of the License, or (at your option) any later version.
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   The GNU C Library is distributed in the hope that it will be useful,
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   but WITHOUT ANY WARRANTY; without even the implied warranty of
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   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
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   Lesser General Public License for more details.
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   You should have received a copy of the GNU Lesser General Public
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   License along with the GNU C Library; if not, see
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   <http://www.gnu.org/licenses/>.  */
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#include <math.h>
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#include <math_private.h>
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#include <math-svid-compat.h>
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#include <libm-alias-double.h>
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#if LIBM_SVID_COMPAT
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/* wrapper pow */
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double
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__pow (double x, double y)
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{
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  double z = __ieee754_pow (x, y);
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  if (__glibc_unlikely (!isfinite (z)))
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    {
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      if (_LIB_VERSION != _IEEE_)
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	{
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	  if (isfinite (x) && isfinite (y))
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	    {
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	      if (isnan (z))
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		/* pow neg**non-int */
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		return __kernel_standard (x, y, 24);
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	      else if (x == 0.0 && y < 0.0)
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		{
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		  if (signbit (x) && signbit (z))
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		    /* pow(-0.0,negative) */
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		    return __kernel_standard (x, y, 23);
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		  else
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		    /* pow(+0.0,negative) */
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		    return __kernel_standard (x, y, 43);
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		}
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	      else
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		/* pow overflow */
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		return __kernel_standard (x, y, 21);
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	    }
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	}
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    }
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  else if (__builtin_expect (z == 0.0, 0)
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	   && isfinite (x) && x != 0 && isfinite (y)
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	   && _LIB_VERSION != _IEEE_)
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    /* pow underflow */
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    return __kernel_standard (x, y, 22);
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  return z;
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}
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libm_alias_double (__pow, pow)
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#endif