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/* Copyright (C) 2005-2021 Free Software Foundation, Inc.
This file is part of the GNU C Library.
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
<https://www.gnu.org/licenses/>. */
#include <stdbool.h>
#include <math.h>
#include <complex.h>
attribute_hidden
long double _Complex
__multc3 (long double a, long double b, long double c, long double d)
{
long double ac, bd, ad, bc, x, y;
ac = a * c;
bd = b * d;
ad = a * d;
bc = b * c;
x = ac - bd;
y = ad + bc;
if (isnan (x) && isnan (y))
{
/* Recover infinities that computed as NaN + iNaN. */
bool recalc = 0;
if (isinf (a) || isinf (b))
{
/* z is infinite. "Box" the infinity and change NaNs in
the other factor to 0. */
a = copysignl (isinf (a) ? 1 : 0, a);
b = copysignl (isinf (b) ? 1 : 0, b);
if (isnan (c)) c = copysignl (0, c);
if (isnan (d)) d = copysignl (0, d);
recalc = 1;
}
if (isinf (c) || isinf (d))
{
/* w is infinite. "Box" the infinity and change NaNs in
the other factor to 0. */
c = copysignl (isinf (c) ? 1 : 0, c);
d = copysignl (isinf (d) ? 1 : 0, d);
if (isnan (a)) a = copysignl (0, a);
if (isnan (b)) b = copysignl (0, b);
recalc = 1;
}
if (!recalc
&& (isinf (ac) || isinf (bd)
|| isinf (ad) || isinf (bc)))
{
/* Recover infinities from overflow by changing NaNs to 0. */
if (isnan (a)) a = copysignl (0, a);
if (isnan (b)) b = copysignl (0, b);
if (isnan (c)) c = copysignl (0, c);
if (isnan (d)) d = copysignl (0, d);
recalc = 1;
}
if (recalc)
{
x = INFINITY * (a * c - b * d);
y = INFINITY * (a * d + b * c);
}
}
return x + I * y;
}
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