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/* mpfr_set_ld -- convert a machine long double to
a multiple precision floating-point number
Copyright 2002, 2003, 2004, 2005 Free Software Foundation, Inc.
This file is part of the MPFR Library.
The 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 2.1 of the License, or (at your
option) any later version.
The 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 MPFR Library; see the file COPYING.LIB. If not, write to
the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
MA 02111-1307, USA. */
#include <float.h>
#include "mpfr-impl.h"
/* Various i386 systems have been seen with float.h LDBL constants equal to
the DBL ones, whereas they ought to be bigger, reflecting the 10-byte
IEEE extended format on that processor. gcc 3.2.1 on FreeBSD and Solaris
has been seen with the problem, and gcc 2.95.4 on FreeBSD 4.7. */
#if HAVE_LDOUBLE_IEEE_EXT_LITTLE
static const struct {
char bytes[10];
long double dummy; /* for memory alignment */
} ldbl_max_struct = {
{ '\377','\377','\377','\377',
'\377','\377','\377','\377',
'\376','\177' }, 0.0
};
#define MPFR_LDBL_MAX (* (const long double *) ldbl_max_struct.bytes)
#else
#define MPFR_LDBL_MAX LDBL_MAX
#endif
int
mpfr_set_ld (mpfr_ptr r, long double d, mp_rnd_t rnd_mode)
{
mpfr_t t, u;
int inexact, shift_exp = 0;
long double x;
LONGDOUBLE_NAN_ACTION (d, goto nan);
if (d > MPFR_LDBL_MAX)
{
mpfr_set_inf (r, 1);
return 0;
}
if (d < -MPFR_LDBL_MAX)
{
mpfr_set_inf (r, -1);
return 0;
}
if (d == 0.0)
return mpfr_set_d (r, (double) d, rnd_mode);
mpfr_init2 (t, MPFR_LDBL_MANT_DIG);
mpfr_init2 (u, IEEE_DBL_MANT_DIG);
mpfr_save_emin_emax ();
convert:
x = d;
mpfr_set_ui (t, 0, GMP_RNDN);
while (x != (long double) 0.0)
{
if ((x > (long double) DBL_MAX) || ((-x) > (long double) DBL_MAX))
{
long double 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 = (long double) (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;
}
if (ABS(x) >= div12)
{
x /= div12; /* exact */
shift_exp += 4096;
}
if (ABS(x) >= div11)
{
x /= div11; /* exact */
shift_exp += 2048;
}
if (ABS(x) >= div10)
{
x /= div10; /* exact */
shift_exp += 1024;
}
/* warning: we may have DBL_MAX=2^1024*(1-2^(-53)) < x < 2^1024,
therefore we have one extra exponent reduction step */
if (ABS(x) >= div9)
{
x /= div9; /* exact */
shift_exp += 512;
}
}
else
{
long double div9, div10, div11;
div9 = (long double) (double) 7.4583407312002067432909653e-155;
/* div9 = 2^(-2^9) */
div10 = div9 * div9; /* 2^(-2^10) */
div11 = div10 * div10; /* 2^(-2^11) if extended precision */
/* since -DBL_MAX <= x <= DBL_MAX, the cast to double should not
overflow here */
inexact = mpfr_set_d (u, (double) x, GMP_RNDZ);
MPFR_ASSERTD(inexact == 0);
if (x != (long double) 0.0 &&
ABS(x) < div10 &&
div11 != (long double) 0.0 &&
div11 / div10 == div10) /* possible underflow */
{
long double div12, div13;
/* After the divisions, any bit of x must be >= div10,
hence the possible division by div9. */
div12 = div11 * div11; /* 2^(-2^12) */
div13 = div12 * div12; /* 2^(-2^13) */
if (ABS(x) <= div13)
{
x /= div13; /* exact */
shift_exp -= 8192;
}
if (ABS(x) <= div12)
{
x /= div12; /* exact */
shift_exp -= 4096;
}
if (ABS(x) <= div11)
{
x /= div11; /* exact */
shift_exp -= 2048;
}
if (ABS(x) <= div10)
{
x /= div10; /* exact */
shift_exp -= 1024;
}
if (ABS(x) <= div9)
{
x /= div9; /* exact */
shift_exp -= 512;
}
}
else
{
if (mpfr_add (t, t, u, GMP_RNDZ) != 0)
{
if (!mpfr_number_p (t))
break;
/* Inexact. This cannot happen unless the C implementation
"lies" on the precision or when long doubles are
implemented with FP expansions like under Mac OS X. */
if (MPFR_PREC (t) != MPFR_PREC (r) + 1)
{
/* We assume that MPFR_PREC (r) < MPFR_PREC_MAX.
The precision MPFR_PREC (r) + 1 allows us to
deduce the rounding bit and the sticky bit. */
mpfr_set_prec (t, MPFR_PREC (r) + 1);
goto convert;
}
else
{
mp_limb_t *tp;
int rb_mask;
/* Since mpfr_add was inexact, the sticky bit is 1. */
tp = MPFR_MANT (t);
rb_mask = MPFR_LIMB_ONE <<
(BITS_PER_MP_LIMB - 1 -
(MPFR_PREC (r) & (BITS_PER_MP_LIMB - 1)));
if (rnd_mode == GMP_RNDN)
rnd_mode = (*tp & rb_mask) ^ MPFR_IS_NEG (t) ?
GMP_RNDU : GMP_RNDD;
*tp |= rb_mask;
break;
}
}
x -= (long double) mpfr_get_d1 (u); /* exact */
}
}
}
inexact = mpfr_mul_2si (r, t, shift_exp, rnd_mode);
mpfr_clear (t);
mpfr_clear (u);
mpfr_restore_emin_emax ();
return mpfr_check_range (r, inexact, rnd_mode);
nan:
MPFR_SET_NAN(r);
MPFR_RET_NAN;
}
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