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/* Multiply a 'float' by a power of 2.
Copyright 2002-2003, 2007-2025 Free Software Foundation, Inc.
This file 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.
This file 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 this program. If not, see <https://www.gnu.org/licenses/>. */
/* Written by Paolo Bonzini and Bruno Haible. */
#include <config.h>
/* Specification. */
#include <math.h>
# include <float.h>
#ifdef USE_LONG_DOUBLE
# include "fpucw.h"
#endif
/* Avoid some warnings from "gcc -Wshadow".
This file doesn't use the exp() function. */
#undef exp
#define exp exponent
#ifdef USE_LONG_DOUBLE
# define FUNC ldexpl
# define DOUBLE long double
# define ISNAN isnanl
# define DECL_ROUNDING DECL_LONG_DOUBLE_ROUNDING
# define BEGIN_ROUNDING() BEGIN_LONG_DOUBLE_ROUNDING ()
# define END_ROUNDING() END_LONG_DOUBLE_ROUNDING ()
# define L_(literal) literal##L
#else
# define FUNC ldexp
# define DOUBLE double
# define ISNAN isnand
# define DECL_ROUNDING
# define BEGIN_ROUNDING()
# define END_ROUNDING()
# define L_(literal) literal
#endif
DOUBLE
FUNC (DOUBLE x, int exp)
{
DECL_ROUNDING
BEGIN_ROUNDING ();
/* Check for zero, nan and infinity. */
if (!(ISNAN (x) || x + x == x))
{
DOUBLE factor = exp < 0 ? L_(0.5) : L_(2.0);
while (true)
{
if (exp % 2 != 0)
x *= factor;
exp /= 2;
if (exp == 0)
break;
factor = factor * factor;
}
}
END_ROUNDING ();
return x;
}
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