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/* mpfr_set_float128 -- convert a machine __float128 number to
a multiple precision floating-point number
Copyright 2012-2016 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
http://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
int
mpfr_set_float128 (mpfr_ptr r, __float128 d, mpfr_rnd_t rnd_mode)
{
mpfr_t t, u;
int inexact, shift_exp;
__float128 x;
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 == ((__float128) 1.0 / (__float128) 0.0)))
{
mpfr_set_inf (r, 1);
return 0;
}
else if (MPFR_UNLIKELY (d == ((__float128) -1.0 / (__float128) 0.0)))
{
mpfr_set_inf (r, -1);
return 0;
}
/* Check for ZERO */
else if (MPFR_UNLIKELY (d == (__float128) 0.0))
return mpfr_set_d (r, (double) d, rnd_mode);
mpfr_init2 (t, IEEE_FLOAT128_MANT_DIG);
mpfr_init2 (u, IEEE_FLOAT128_MANT_DIG);
MPFR_SAVE_EXPO_MARK (expo);
x = d;
MPFR_SET_ZERO (t); /* The sign doesn't matter. */
shift_exp = 0; /* invariant: remainder to deal with is x*2^shift_exp */
/* 2^(-16494) <= x < 2^16384 */
while (x != (__float128) 0.0)
{
/* check overflow of double */
if (x > (__float128) DBL_MAX || (-x) > (__float128) DBL_MAX)
{
__float128 div9, div10, div11, div12, div13;
#define TWO_64 18446744073709551616.0 /* 2^64 */
#define TWO_128 (TWO_64 * TWO_64)
#define TWO_256 (TWO_128 * TWO_128)
div9 = (__float128) (double) (TWO_256 * TWO_256); /* 2^(2^9) */
div10 = div9 * div9;
div11 = div10 * div10; /* 2^(2^11) */
div12 = div11 * div11; /* 2^(2^12) */
div13 = div12 * div12; /* 2^(2^13) */
if (ABS (x) >= div13)
{
x /= div13; /* exact */
shift_exp += 8192;
mpfr_div_2si (t, t, 8192, MPFR_RNDZ);
}
/* now |x| < 2^8192 */
if (ABS (x) >= div12)
{
x /= div12; /* exact */
shift_exp += 4096;
mpfr_div_2si (t, t, 4096, MPFR_RNDZ);
}
/* now |x| < 2^4096 */
if (ABS (x) >= div11)
{
x /= div11; /* exact */
shift_exp += 2048;
mpfr_div_2si (t, t, 2048, MPFR_RNDZ);
}
/* now |x| < 2^2048 */
if (ABS (x) >= (0.5 * div10))
{
x /= (2.0 * div10); /* exact */
shift_exp += 1025;
mpfr_div_2si (t, t, 1025, MPFR_RNDZ);
}
/* now |x| < 2^1023 */
} /* end of check overflow of double */
/* check underflow on double */
else if ((x < (__float128) DBL_MIN) && ((-x) < (__float128) DBL_MIN))
{
__float128 div9, div10, div11, div12, div13;
div9 = (__float128) (double) 7.4583407312002067432909653e-155;
/* div9 = 2^(-512) */
div10 = div9 * div9; /* 2^(-1024) */
div11 = div10 * div10; /* 2^(-2048) */
div12 = div11 * div11; /* 2^(-4096) */
div13 = div12 * div12; /* 2^(-8192) */
if (ABS (x) <= div13)
{
x /= div13; /* exact */
shift_exp -= 8192;
mpfr_mul_2si (t, t, 8192, MPFR_RNDZ);
}
/* now |x| > 2^(-8192) */
if (ABS (x) <= div12)
{
x /= div12; /* exact */
shift_exp -= 4096;
mpfr_mul_2si (t, t, 4096, MPFR_RNDZ);
}
/* now |x| > 2^(-4096) */
if (ABS (x) <= div11)
{
x /= div11; /* exact */
shift_exp -= 2048;
mpfr_mul_2si (t, t, 2048, MPFR_RNDZ);
}
/* now |x| > 2^(-2048) */
if (ABS (x) <= (div10 * 4.0)) /* div10 * 4.0 = 2^(-1022) */
{
x /= (div10 * 0.25); /* exact, div10 * 0.25 = 2^(-1026) */
shift_exp -= 1026;
mpfr_mul_2si (t, t, 1026, MPFR_RNDZ);
}
/* now |x| > 2^(-1022) */
}
else /* no underflow: 2^(-512) <= |x| < 2^1023 */
{
inexact = mpfr_set_d (u, (double) x, MPFR_RNDZ);
MPFR_ASSERTD (inexact == 0);
if (mpfr_add (t, t, u, MPFR_RNDZ) != 0)
{
if (!mpfr_number_p (t))
break;
/* Inexact. This cannot happen unless the C implementation
"lies" on the precision. */
}
x -= (__float128) mpfr_get_d1 (u); /* exact */
}
}
inexact = mpfr_mul_2si (r, t, shift_exp, rnd_mode);
mpfr_clear (t);
mpfr_clear (u);
MPFR_SAVE_EXPO_FREE (expo);
return mpfr_check_range (r, inexact, rnd_mode);
}
#endif /* MPFR_WANT_FLOAT128 */
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