diff options
Diffstat (limited to 'sysdeps/ieee754/ldbl-128ibm/mpn2ldbl.c')
| -rw-r--r-- | sysdeps/ieee754/ldbl-128ibm/mpn2ldbl.c | 152 |
1 files changed, 152 insertions, 0 deletions
diff --git a/sysdeps/ieee754/ldbl-128ibm/mpn2ldbl.c b/sysdeps/ieee754/ldbl-128ibm/mpn2ldbl.c new file mode 100644 index 0000000..21d1e62 --- /dev/null +++ b/sysdeps/ieee754/ldbl-128ibm/mpn2ldbl.c @@ -0,0 +1,152 @@ +/* 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; +} |