diff options
Diffstat (limited to 'REORG.TODO/sysdeps/i386/ldbl2mpn.c')
| -rw-r--r-- | REORG.TODO/sysdeps/i386/ldbl2mpn.c | 120 |
1 files changed, 120 insertions, 0 deletions
diff --git a/REORG.TODO/sysdeps/i386/ldbl2mpn.c b/REORG.TODO/sysdeps/i386/ldbl2mpn.c new file mode 100644 index 0000000000..076be0ae7e --- /dev/null +++ b/REORG.TODO/sysdeps/i386/ldbl2mpn.c @@ -0,0 +1,120 @@ +/* Copyright (C) 1995-2017 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 <stdlib.h> + +/* Convert a `long double' in IEEE854 standard double-precision format to a + multi-precision integer representing the significand scaled up by its + number of bits (64 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 ieee854_long_double u; + u.d = value; + + *is_neg = u.ieee.negative; + *expt = (int) u.ieee.exponent - IEEE854_LONG_DOUBLE_BIAS; + +#if BITS_PER_MP_LIMB == 32 + res_ptr[0] = u.ieee.mantissa1; /* Low-order 32 bits of fraction. */ + res_ptr[1] = u.ieee.mantissa0; /* High-order 32 bits. */ + #define N 2 +#elif BITS_PER_MP_LIMB == 64 + /* Hopefully the compiler will combine the two bitfield extracts + and this composition into just the original quadword extract. */ + res_ptr[0] = ((mp_limb_t) u.ieee.mantissa0 << 32) | u.ieee.mantissa1; + #define N 1 +#else + #error "mp_limb size " BITS_PER_MP_LIMB "not accounted for" +#endif + + if (u.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[N - 1] == 0) /* Assumes N<=2. */ + /* 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. */ + int cnt; + + /* One problem with Intel's 80-bit format is that the explicit + leading one in the normalized representation has to be zero + for denormalized number. If it is one, the number is according + to Intel's specification an invalid number. We make the + representation unique by explicitly clearing this bit. */ + res_ptr[N - 1] &= ~((mp_limb_t) 1 << ((LDBL_MANT_DIG - 1) % BITS_PER_MP_LIMB)); + + if (res_ptr[N - 1] != 0) + { + count_leading_zeros (cnt, res_ptr[N - 1]); + if (cnt != 0) + { +#if N == 2 + res_ptr[N - 1] = res_ptr[N - 1] << cnt + | (res_ptr[0] >> (BITS_PER_MP_LIMB - cnt)); + res_ptr[0] <<= cnt; +#else + res_ptr[N - 1] <<= cnt; +#endif + } + *expt = LDBL_MIN_EXP - 1 - cnt; + } + else if (res_ptr[0] != 0) + { + count_leading_zeros (cnt, res_ptr[0]); + res_ptr[N - 1] = res_ptr[0] << cnt; + res_ptr[0] = 0; + *expt = LDBL_MIN_EXP - 1 - BITS_PER_MP_LIMB - cnt; + } + else + { + /* This is the special case of the pseudo denormal number + with only the implicit leading bit set. The value is + in fact a normal number and so we have to treat this + case differently. */ +#if N == 2 + res_ptr[N - 1] = 0x80000000ul; +#else + res_ptr[0] = 0x8000000000000000ul; +#endif + *expt = LDBL_MIN_EXP - 1; + } + } + } + else if (u.ieee.exponent < 0x7fff +#if N == 2 + && res_ptr[0] == 0 +#endif + && res_ptr[N - 1] == 0) + /* Pseudo zero. */ + *expt = 0; + + return N; +} |