sysdeps/ieee754/float128/mpn2float128.c

   1 /* Convert a number in multi-precision format to _Float128.
   2    Copyright (C) 2017 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include "gmp.h"
  20 #include "gmp-impl.h"
  21 #include <float.h>
  22 #include <math.h>
  23
  24 #include "ieee754_float128.h"
  25
  26 /* Convert a multi-precision integer of the needed number of bits (113 for
  27    binary128) and an integral power of two to a `_Float128' in IEEE854
  28    quad-precision format.  */
  29
  30 _Float128
  31 __mpn_construct_float128 (mp_srcptr frac_ptr, int expt, int sign)
  32 {
  33   union ieee854_float128 u;
  34
  35   u.ieee.negative = sign;
  36   u.ieee.exponent = expt + IEEE854_FLOAT128_BIAS;
  37 #if BITS_PER_MP_LIMB == 32
  38   u.ieee.mantissa3 = frac_ptr[0];
  39   u.ieee.mantissa2 = frac_ptr[1];
  40   u.ieee.mantissa1 = frac_ptr[2];
  41   u.ieee.mantissa0 = frac_ptr[3] & (((mp_limb_t) 1
  42                                      << (FLT128_MANT_DIG - 96)) - 1);
  43 #elif BITS_PER_MP_LIMB == 64
  44   u.ieee.mantissa3 = frac_ptr[0] & (((mp_limb_t) 1 << 32) - 1);
  45   u.ieee.mantissa2 = frac_ptr[0] >> 32;
  46   u.ieee.mantissa1 = frac_ptr[1] & (((mp_limb_t) 1 << 32) - 1);
  47   u.ieee.mantissa0 = (frac_ptr[1] >> 32) & (((mp_limb_t) 1
  48                                              << (FLT128_MANT_DIG - 96)) - 1);
  49 #else
  50   #error "mp_limb size " BITS_PER_MP_LIMB "not accounted for"
  51 #endif
  52
  53   return u.d;
  54 }