1 /* Copyright (C) 1995-2022 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 <https://www.gnu.org/licenses/>. */ 17 18 #include "gmp.h" 19 #include "gmp-impl.h" 20 #include <ieee754.h> 21 #include <float.h> 22 23 /* Convert a multi-precision integer of the needed number of bits (53 for 24 double) and an integral power of two to a `double' in IEEE754 double- 25 precision format. */ 26 27 double __mpn_construct_double(mp_srcptr frac_ptr,int expt,int negative)28__mpn_construct_double (mp_srcptr frac_ptr, int expt, int negative) 29 { 30 union ieee754_double u; 31 32 u.ieee.negative = negative; 33 u.ieee.exponent = expt + IEEE754_DOUBLE_BIAS; 34 #if BITS_PER_MP_LIMB == 32 35 u.ieee.mantissa1 = frac_ptr[0]; 36 u.ieee.mantissa0 = frac_ptr[1] & (((mp_limb_t) 1 37 << (DBL_MANT_DIG - 32)) - 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) & (((mp_limb_t) 1 41 << (DBL_MANT_DIG - 32)) - 1); 42 #else 43 # error "mp_limb size " BITS_PER_MP_LIMB "not accounted for" 44 #endif 45 46 return u.d; 47 } 48