| /* Copyright (C) 1995, 1996, 1997, 1998, 1999, 2002, 2003, 2004, 2006, 2007 |
| 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, write to the Free |
| Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA |
| 02111-1307 USA. */ |
| |
| #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.ieee.negative = sign; |
| u.ieee.negative2 = sign; |
| u.ieee.exponent = expt + IBM_EXTENDED_LONG_DOUBLE_BIAS; |
| u.ieee.exponent2 = 0; |
| exponent2 = expt - 53 + IBM_EXTENDED_LONG_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 - 11; |
| else |
| lzcount = lzcount + 42; |
| |
| if (lzcount > u.ieee.exponent) |
| { |
| lzcount = u.ieee.exponent; |
| u.ieee.exponent = 0; |
| exponent2 -= lzcount; |
| } |
| else |
| { |
| u.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 != 0L) |
| { |
| /* hidden2 bit of low double controls rounding of the high double. |
| If hidden2 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)))) |
| { |
| hi++; |
| if ((hi & ((1LL << 52) - 1)) == 0) |
| { |
| if ((hi & (1LL << 53)) != 0) |
| hi -= 1LL << 52; |
| u.ieee.exponent++; |
| } |
| u.ieee.negative2 = !sign; |
| lo = (1LL << 53) - lo; |
| } |
| |
| /* The hidden bit of the lo mantissa is zero so we need to normalize |
| it for the low double. Shift it left until the hidden bit is '1' |
| then adjust the 2nd 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 - 11; |
| if (lzcount > 0) |
| { |
| lo = lo << lzcount; |
| exponent2 = exponent2 - lzcount; |
| } |
| if (exponent2 > 0) |
| u.ieee.exponent2 = exponent2; |
| else |
| lo >>= 1 - exponent2; |
| } |
| else |
| u.ieee.negative2 = 0; |
| |
| u.ieee.mantissa3 = lo & 0xffffffffLL; |
| u.ieee.mantissa2 = (lo >> 32) & 0xfffff; |
| u.ieee.mantissa1 = hi & 0xffffffffLL; |
| u.ieee.mantissa0 = (hi >> 32) & ((1LL << (LDBL_MANT_DIG - 86)) - 1); |
| |
| return u.d; |
| } |