| /* Copyright (C) 1995-2014 Free Software Foundation, Inc. |
| This file is part of the GNU C Library. |
| |
| The GNU C 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 GNU C 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 GNU C Library; if not, see |
| <http://www.gnu.org/licenses/>. */ |
| |
| #include "gmp.h" |
| #include "gmp-impl.h" |
| #include "longlong.h" |
| #include <ieee754.h> |
| #include <float.h> |
| #include <math.h> |
| #include <stdlib.h> |
| |
| /* Convert a `long double' in IBM extended format to a multi-precision |
| integer representing the significand scaled up by its number of |
| bits (106 for long double) and an integral power of two (MPN |
| frexpl). */ |
| |
| mp_size_t |
| __mpn_extract_long_double (mp_ptr res_ptr, mp_size_t size, |
| int *expt, int *is_neg, |
| long double value) |
| { |
| union ibm_extended_long_double u; |
| unsigned long long hi, lo; |
| int ediff; |
| |
| u.ld = value; |
| |
| *is_neg = u.d[0].ieee.negative; |
| *expt = (int) u.d[0].ieee.exponent - IEEE754_DOUBLE_BIAS; |
| |
| lo = ((long long) u.d[1].ieee.mantissa0 << 32) | u.d[1].ieee.mantissa1; |
| hi = ((long long) u.d[0].ieee.mantissa0 << 32) | u.d[0].ieee.mantissa1; |
| |
| /* If the lower double is not a denormal or zero then set the hidden |
| 53rd bit. */ |
| if (u.d[1].ieee.exponent != 0) |
| lo |= 1ULL << 52; |
| else |
| lo = lo << 1; |
| |
| /* The lower double is normalized separately from the upper. We may |
| need to adjust the lower manitissa to reflect this. */ |
| ediff = u.d[0].ieee.exponent - u.d[1].ieee.exponent - 53; |
| if (ediff > 0) |
| { |
| if (ediff < 64) |
| lo = lo >> ediff; |
| else |
| lo = 0; |
| } |
| else if (ediff < 0) |
| lo = lo << -ediff; |
| |
| /* The high double may be rounded and the low double reflects the |
| difference between the long double and the rounded high double |
| value. This is indicated by a differnce between the signs of the |
| high and low doubles. */ |
| if (u.d[0].ieee.negative != u.d[1].ieee.negative |
| && lo != 0) |
| { |
| lo = (1ULL << 53) - lo; |
| if (hi == 0) |
| { |
| /* we have a borrow from the hidden bit, so shift left 1. */ |
| hi = 0x0ffffffffffffeLL | (lo >> 51); |
| lo = 0x1fffffffffffffLL & (lo << 1); |
| (*expt)--; |
| } |
| else |
| hi--; |
| } |
| #if BITS_PER_MP_LIMB == 32 |
| /* Combine the mantissas to be contiguous. */ |
| res_ptr[0] = lo; |
| res_ptr[1] = (hi << (53 - 32)) | (lo >> 32); |
| res_ptr[2] = hi >> 11; |
| res_ptr[3] = hi >> (32 + 11); |
| #define N 4 |
| #elif BITS_PER_MP_LIMB == 64 |
| /* Combine the two mantissas to be contiguous. */ |
| res_ptr[0] = (hi << 53) | lo; |
| res_ptr[1] = hi >> 11; |
| #define N 2 |
| #else |
| #error "mp_limb size " BITS_PER_MP_LIMB "not accounted for" |
| #endif |
| /* The format does not fill the last limb. There are some zeros. */ |
| #define NUM_LEADING_ZEROS (BITS_PER_MP_LIMB \ |
| - (LDBL_MANT_DIG - ((N - 1) * BITS_PER_MP_LIMB))) |
| |
| if (u.d[0].ieee.exponent == 0) |
| { |
| /* A biased exponent of zero is a special case. |
| Either it is a zero or it is a denormal number. */ |
| if (res_ptr[0] == 0 && res_ptr[1] == 0 |
| && res_ptr[N - 2] == 0 && res_ptr[N - 1] == 0) /* Assumes N<=4. */ |
| /* It's zero. */ |
| *expt = 0; |
| else |
| { |
| /* It is a denormal number, meaning it has no implicit leading |
| one bit, and its exponent is in fact the format minimum. We |
| use DBL_MIN_EXP instead of LDBL_MIN_EXP below because the |
| latter describes the properties of both parts together, but |
| the exponent is computed from the high part only. */ |
| int cnt; |
| |
| #if N == 2 |
| if (res_ptr[N - 1] != 0) |
| { |
| count_leading_zeros (cnt, res_ptr[N - 1]); |
| cnt -= NUM_LEADING_ZEROS; |
| res_ptr[N - 1] = res_ptr[N - 1] << cnt |
| | (res_ptr[0] >> (BITS_PER_MP_LIMB - cnt)); |
| res_ptr[0] <<= cnt; |
| *expt = DBL_MIN_EXP - 1 - cnt; |
| } |
| else |
| { |
| count_leading_zeros (cnt, res_ptr[0]); |
| if (cnt >= NUM_LEADING_ZEROS) |
| { |
| res_ptr[N - 1] = res_ptr[0] << (cnt - NUM_LEADING_ZEROS); |
| res_ptr[0] = 0; |
| } |
| else |
| { |
| res_ptr[N - 1] = res_ptr[0] >> (NUM_LEADING_ZEROS - cnt); |
| res_ptr[0] <<= BITS_PER_MP_LIMB - (NUM_LEADING_ZEROS - cnt); |
| } |
| *expt = DBL_MIN_EXP - 1 |
| - (BITS_PER_MP_LIMB - NUM_LEADING_ZEROS) - cnt; |
| } |
| #else |
| int j, k, l; |
| |
| for (j = N - 1; j > 0; j--) |
| if (res_ptr[j] != 0) |
| break; |
| |
| count_leading_zeros (cnt, res_ptr[j]); |
| cnt -= NUM_LEADING_ZEROS; |
| l = N - 1 - j; |
| if (cnt < 0) |
| { |
| cnt += BITS_PER_MP_LIMB; |
| l--; |
| } |
| if (!cnt) |
| for (k = N - 1; k >= l; k--) |
| res_ptr[k] = res_ptr[k-l]; |
| else |
| { |
| for (k = N - 1; k > l; k--) |
| res_ptr[k] = res_ptr[k-l] << cnt |
| | res_ptr[k-l-1] >> (BITS_PER_MP_LIMB - cnt); |
| res_ptr[k--] = res_ptr[0] << cnt; |
| } |
| |
| for (; k >= 0; k--) |
| res_ptr[k] = 0; |
| *expt = DBL_MIN_EXP - 1 - l * BITS_PER_MP_LIMB - cnt; |
| #endif |
| } |
| } |
| else |
| /* Add the implicit leading one bit for a normalized number. */ |
| res_ptr[N - 1] |= (mp_limb_t) 1 << (LDBL_MANT_DIG - 1 |
| - ((N - 1) * BITS_PER_MP_LIMB)); |
| |
| return N; |
| } |