libquadmath/strtod/mpn2flt128.c

   1 /* Copyright (C) 1995-2013 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, write to the Free
  16    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  17    02111-1307 USA.  */
  18
  19 #include <config.h>
  20 #include <float.h>
  21 #include <math.h>
  22 #include "../printf/gmp-impl.h"
  23
  24 /* Convert a multi-precision integer of the needed number of bits (113 for
  25    long double) and an integral power of two to a `long double' in IEEE854
  26    quad-precision format.  */
  27
  28 __float128
  29 mpn_construct_float128 (mp_srcptr frac_ptr, int expt, int sign)
  30 {
  31   ieee854_float128 u;
  32
  33   u.ieee.negative = sign;
  34   u.ieee.exponent = expt + IEEE854_FLOAT128_BIAS;
  35 #if BITS_PER_MP_LIMB == 32
  36   u.ieee.mant_low = (((uint64_t) frac_ptr[1]) << 32)
  37                     | (frac_ptr[0] & 0xffffffff);
  38   u.ieee.mant_high = (((uint64_t) frac_ptr[3]
  39                        & (((mp_limb_t) 1 << (FLT128_MANT_DIG - 96)) - 1))
  40                       << 32) | (frac_ptr[2] & 0xffffffff);
  41 #elif BITS_PER_MP_LIMB == 64
  42   u.ieee.mant_low = frac_ptr[0];
  43   u.ieee.mant_high = frac_ptr[1]
  44                      & (((mp_limb_t) 1 << (FLT128_MANT_DIG - 64)) - 1);
  45 #else
  46   #error "mp_limb size " BITS_PER_MP_LIMB "not accounted for"
  47 #endif
  48
  49   return u.value;
  50 }