| /* 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 <ieee754.h> |
| #include <float.h> |
| #include <math.h> |
| |
| /* Convert a multi-precision integer of the needed number of bits (106 |
| for long double) and an integral power of two to a `long double' in |
| IBM extended format. */ |
| |
| long double |
| __mpn_construct_long_double (mp_srcptr frac_ptr, int expt, int sign) |
| { |
| union ibm_extended_long_double u; |
| unsigned long lzcount; |
| unsigned long long hi, lo; |
| int exponent2; |
| |
| u.d[0].ieee.negative = sign; |
| u.d[1].ieee.negative = sign; |
| u.d[0].ieee.exponent = expt + IEEE754_DOUBLE_BIAS; |
| u.d[1].ieee.exponent = 0; |
| exponent2 = expt - 53 + IEEE754_DOUBLE_BIAS; |
| |
| #if BITS_PER_MP_LIMB == 32 |
| /* The low order 53 bits (52 + hidden) go into the lower double */ |
| lo = frac_ptr[0]; |
| lo |= (frac_ptr[1] & ((1LL << (53 - 32)) - 1)) << 32; |
| /* The high order 53 bits (52 + hidden) go into the upper double */ |
| hi = (frac_ptr[1] >> (53 - 32)) & ((1 << 11) - 1); |
| hi |= ((unsigned long long) frac_ptr[2]) << 11; |
| hi |= ((unsigned long long) frac_ptr[3]) << (32 + 11); |
| #elif BITS_PER_MP_LIMB == 64 |
| /* The low order 53 bits (52 + hidden) go into the lower double */ |
| lo = frac_ptr[0] & (((mp_limb_t) 1 << 53) - 1); |
| /* The high order 53 bits (52 + hidden) go into the upper double */ |
| hi = (frac_ptr[0] >> 53) & (((mp_limb_t) 1 << 11) - 1); |
| hi |= (frac_ptr[1] << 11); |
| #else |
| #error "mp_limb size " BITS_PER_MP_LIMB "not accounted for" |
| #endif |
| |
| if ((hi & (1LL << 52)) == 0 && (hi | lo) != 0) |
| { |
| /* denormal number */ |
| unsigned long long val = hi ? hi : lo; |
| |
| if (sizeof (val) == sizeof (long)) |
| lzcount = __builtin_clzl (val); |
| else if ((val >> 32) != 0) |
| lzcount = __builtin_clzl ((long) (val >> 32)); |
| else |
| lzcount = __builtin_clzl ((long) val) + 32; |
| if (hi) |
| lzcount = lzcount - (64 - 53); |
| else |
| lzcount = lzcount + 53 - (64 - 53); |
| |
| if (lzcount > u.d[0].ieee.exponent) |
| { |
| lzcount = u.d[0].ieee.exponent; |
| u.d[0].ieee.exponent = 0; |
| exponent2 -= lzcount; |
| } |
| else |
| { |
| u.d[0].ieee.exponent -= (lzcount - 1); |
| exponent2 -= (lzcount - 1); |
| } |
| |
| if (lzcount <= 53) |
| { |
| hi = (hi << lzcount) | (lo >> (53 - lzcount)); |
| lo = (lo << lzcount) & ((1LL << 53) - 1); |
| } |
| else |
| { |
| hi = lo << (lzcount - 53); |
| lo = 0; |
| } |
| } |
| |
| if (lo != 0) |
| { |
| /* hidden bit of low double controls rounding of the high double. |
| If hidden is '1' and either the explicit mantissa is non-zero |
| or hi is odd, then round up hi and adjust lo (2nd mantissa) |
| plus change the sign of the low double to compensate. */ |
| if ((lo & (1LL << 52)) != 0 |
| && ((hi & 1) != 0 || (lo & ((1LL << 52) - 1)) != 0)) |
| { |
| hi++; |
| if ((hi & (1LL << 53)) != 0) |
| { |
| hi >>= 1; |
| u.d[0].ieee.exponent++; |
| } |
| u.d[1].ieee.negative = !sign; |
| lo = (1LL << 53) - lo; |
| } |
| |
| /* Normalize the low double. Shift the mantissa left until |
| the hidden bit is '1' and adjust the exponent accordingly. */ |
| |
| if (sizeof (lo) == sizeof (long)) |
| lzcount = __builtin_clzl (lo); |
| else if ((lo >> 32) != 0) |
| lzcount = __builtin_clzl ((long) (lo >> 32)); |
| else |
| lzcount = __builtin_clzl ((long) lo) + 32; |
| lzcount = lzcount - (64 - 53); |
| lo <<= lzcount; |
| exponent2 -= lzcount; |
| |
| if (exponent2 > 0) |
| u.d[1].ieee.exponent = exponent2; |
| else if (exponent2 > -53) |
| lo >>= 1 - exponent2; |
| else |
| lo = 0; |
| } |
| else |
| u.d[1].ieee.negative = 0; |
| |
| u.d[1].ieee.mantissa1 = lo; |
| u.d[1].ieee.mantissa0 = lo >> 32; |
| u.d[0].ieee.mantissa1 = hi; |
| u.d[0].ieee.mantissa0 = hi >> 32; |
| |
| return u.ld; |
| } |