sysdeps/ieee754/ldbl-96/mpn2ldbl.c

   1 /* Copyright (C) 1995-2015 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, see
  16    <http://www.gnu.org/licenses/>.  */
  17
  18 #include "gmp.h"
  19 #include "gmp-impl.h"
  20 #include <ieee754.h>
  21 #include <float.h>
  22 #include <math.h>
  23
  24 /* Convert a multi-precision integer of the needed number of bits (64 for
  25    long double) and an integral power of two to a `long double' in IEEE854
  26    extended-precision format.  */
  27
  28 long double
  29 __mpn_construct_long_double (mp_srcptr frac_ptr, int expt, int sign)
  30 {
  31   union ieee854_long_double u;
  32
  33   u.ieee.negative = sign;
  34   u.ieee.exponent = expt + IEEE854_LONG_DOUBLE_BIAS;
  35 #if BITS_PER_MP_LIMB == 32
  36   u.ieee.mantissa1 = frac_ptr[0];
  37   u.ieee.mantissa0 = frac_ptr[1];
  38 #elif BITS_PER_MP_LIMB == 64
  39   u.ieee.mantissa1 = frac_ptr[0] & (((mp_limb_t) 1 << 32) - 1);
  40   u.ieee.mantissa0 = frac_ptr[0] >> 32;
  41 #else
  42   #error "mp_limb size " BITS_PER_MP_LIMB "not accounted for"
  43 #endif
  44
  45   return u.d;
  46 }