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/* mpfr_set_float128 -- convert a machine __float128 number to
a multiple precision floating-point number
Copyright 2012-2019 Free Software Foundation, Inc.
Contributed by the AriC and Caramba projects, INRIA.
This file is part of the GNU MPFR Library.
The GNU MPFR 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 3 of the License, or (at your
option) any later version.
The GNU MPFR 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 MPFR Library; see the file COPYING.LESSER. If not, see
https://www.gnu.org/licenses/ or write to the Free Software Foundation, Inc.,
51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA. */
#include <float.h> /* for DBL_MAX */
#define MPFR_NEED_LONGLONG_H
#include "mpfr-impl.h"
#ifdef MPFR_WANT_FLOAT128
/* The q suffix is a GNU C extension, but so is __float128. */
#define MPFR_FLOAT128_MAX 0x1.ffffffffffffffffffffffffffffp+16383q
int
mpfr_set_float128 (mpfr_ptr r, __float128 d, mpfr_rnd_t rnd_mode)
{
mpfr_t t;
mp_limb_t *tp;
int inexact, shift_exp, neg, e, i;
__float128 p[14], q[14];
MPFR_SAVE_EXPO_DECL (expo);
/* Check for NaN */
if (MPFR_UNLIKELY (DOUBLE_ISNAN (d)))
{
MPFR_SET_NAN(r);
MPFR_RET_NAN;
}
/* Check for INF */
if (MPFR_UNLIKELY (d > MPFR_FLOAT128_MAX))
{
MPFR_SET_INF (r);
MPFR_SET_POS (r);
return 0;
}
else if (MPFR_UNLIKELY (d < -MPFR_FLOAT128_MAX))
{
MPFR_SET_INF (r);
MPFR_SET_NEG (r);
return 0;
}
/* Check for ZERO */
else if (MPFR_UNLIKELY (d == (__float128) 0.0))
return mpfr_set_d (r, (double) d, rnd_mode);
shift_exp = 0; /* invariant: remainder to deal with is d*2^shift_exp */
neg = d < 0;
if (d < 0)
d = -d;
/* Scaling, avoiding (slow) divisions. Should the tables be cached? */
if (d >= 1.0)
{
p[0] = 2.0;
q[0] = 0.5;
e = 1;
/* p[i] = 2^(2^i), q[i] = 1/p[i] */
for (i = 0; i < 13 && d >= p[i]; i++)
{
p[i+1] = p[i] * p[i];
q[i+1] = q[i] * q[i];
e <<= 1;
}
for (; i >= 0; e >>= 1, i--)
if (d >= p[i])
{
d *= q[i];
shift_exp += e;
}
d *= 0.5;
shift_exp++;
}
else if (d < 0.5)
{
p[0] = 2.0;
q[0] = 0.5;
e = 1;
/* p[i] = 2^(2^i), q[i] = 1/p[i] */
for (i = 0; i < 13 && d < q[i]; i++)
{
p[i+1] = p[i] * p[i];
q[i+1] = q[i] * q[i];
e <<= 1;
}
/* The while() may be needed for i = 13 due to subnormals.
This can probably be improved without yielding an underflow. */
for (; i >= 0; e >>= 1, i--)
while (d < q[i])
{
d *= p[i];
shift_exp -= e;
}
}
MPFR_ASSERTD (d >= 0.5 && d < 1.0);
mpfr_init2 (t, IEEE_FLOAT128_MANT_DIG);
tp = MPFR_MANT (t);
MPFR_SAVE_EXPO_MARK (expo);
MPFR_SET_EXP (t, shift_exp);
MPFR_SET_SIGN (t, neg ? MPFR_SIGN_NEG : MPFR_SIGN_POS);
for (i = MPFR_LAST_LIMB (t); i >= 0; i--)
{
d *= 2 * (__float128) MPFR_LIMB_HIGHBIT;
tp[i] = (mp_limb_t) d;
d -= tp[i];
}
inexact = mpfr_set (r, t, rnd_mode);
mpfr_clear (t);
MPFR_SAVE_EXPO_FREE (expo);
return mpfr_check_range (r, inexact, rnd_mode);
}
#endif /* MPFR_WANT_FLOAT128 */
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