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32c075e1 | 1 | /* Copyright (C) 1995, 1996, 1997, 2000, 2007 Free Software Foundation, Inc. |
478b92f0 | 2 | This file is part of the GNU C Library. |
ce563359 | 3 | |
478b92f0 | 4 | The GNU C Library is free software; you can redistribute it and/or |
41bdb6e2 AJ |
5 | modify it under the terms of the GNU Lesser General Public |
6 | License as published by the Free Software Foundation; either | |
7 | version 2.1 of the License, or (at your option) any later version. | |
ce563359 | 8 | |
478b92f0 UD |
9 | The GNU C Library is distributed in the hope that it will be useful, |
10 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
11 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
41bdb6e2 | 12 | Lesser General Public License for more details. |
ce563359 | 13 | |
41bdb6e2 AJ |
14 | You should have received a copy of the GNU Lesser General Public |
15 | License along with the GNU C Library; if not, write to the Free | |
16 | Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA | |
17 | 02111-1307 USA. */ | |
ce563359 RM |
18 | |
19 | #include "gmp.h" | |
20 | #include "gmp-impl.h" | |
21 | #include "longlong.h" | |
32c075e1 | 22 | #include <ieee754.h> |
ce563359 RM |
23 | #include <float.h> |
24 | #include <stdlib.h> | |
25 | ||
26 | /* Convert a `long double' in IEEE854 standard double-precision format to a | |
27 | multi-precision integer representing the significand scaled up by its | |
28 | number of bits (64 for long double) and an integral power of two | |
29 | (MPN frexpl). */ | |
30 | ||
31 | mp_size_t | |
32 | __mpn_extract_long_double (mp_ptr res_ptr, mp_size_t size, | |
33 | int *expt, int *is_neg, | |
34 | long double value) | |
35 | { | |
36 | union ieee854_long_double u; | |
37 | u.d = value; | |
38 | ||
39 | *is_neg = u.ieee.negative; | |
40 | *expt = (int) u.ieee.exponent - IEEE854_LONG_DOUBLE_BIAS; | |
41 | ||
42 | #if BITS_PER_MP_LIMB == 32 | |
43 | res_ptr[0] = u.ieee.mantissa1; /* Low-order 32 bits of fraction. */ | |
44 | res_ptr[1] = u.ieee.mantissa0; /* High-order 32 bits. */ | |
45 | #define N 2 | |
46 | #elif BITS_PER_MP_LIMB == 64 | |
47 | /* Hopefully the compiler will combine the two bitfield extracts | |
48 | and this composition into just the original quadword extract. */ | |
32c075e1 | 49 | res_ptr[0] = ((mp_limb_t) u.ieee.mantissa0 << 32) | u.ieee.mantissa1; |
ce563359 RM |
50 | #define N 1 |
51 | #else | |
52 | #error "mp_limb size " BITS_PER_MP_LIMB "not accounted for" | |
53 | #endif | |
54 | ||
55 | if (u.ieee.exponent == 0) | |
56 | { | |
57 | /* A biased exponent of zero is a special case. | |
58 | Either it is a zero or it is a denormal number. */ | |
59 | if (res_ptr[0] == 0 && res_ptr[N - 1] == 0) /* Assumes N<=2. */ | |
60 | /* It's zero. */ | |
61 | *expt = 0; | |
62 | else | |
63 | { | |
478b92f0 UD |
64 | /* It is a denormal number, meaning it has no implicit leading |
65 | one bit, and its exponent is in fact the format minimum. */ | |
ce563359 RM |
66 | int cnt; |
67 | ||
68 | /* One problem with Intel's 80-bit format is that the explicit | |
69 | leading one in the normalized representation has to be zero | |
70 | for denormalized number. If it is one, the number is according | |
71 | to Intel's specification an invalid number. We make the | |
72 | representation unique by explicitly clearing this bit. */ | |
73 | res_ptr[N - 1] &= ~(1L << ((LDBL_MANT_DIG - 1) % BITS_PER_MP_LIMB)); | |
74 | ||
75 | if (res_ptr[N - 1] != 0) | |
76 | { | |
77 | count_leading_zeros (cnt, res_ptr[N - 1]); | |
78 | if (cnt != 0) | |
79 | { | |
80 | #if N == 2 | |
478b92f0 UD |
81 | res_ptr[N - 1] = res_ptr[N - 1] << cnt |
82 | | (res_ptr[0] >> (BITS_PER_MP_LIMB - cnt)); | |
83 | res_ptr[0] <<= cnt; | |
ce563359 | 84 | #else |
478b92f0 | 85 | res_ptr[N - 1] <<= cnt; |
ce563359 RM |
86 | #endif |
87 | } | |
88 | *expt = LDBL_MIN_EXP - 1 - cnt; | |
89 | } | |
8cd806cf | 90 | else if (res_ptr[0] != 0) |
ce563359 RM |
91 | { |
92 | count_leading_zeros (cnt, res_ptr[0]); | |
93 | res_ptr[N - 1] = res_ptr[0] << cnt; | |
94 | res_ptr[0] = 0; | |
95 | *expt = LDBL_MIN_EXP - 1 - BITS_PER_MP_LIMB - cnt; | |
96 | } | |
8cd806cf UD |
97 | else |
98 | { | |
99 | /* This is the special case of the pseudo denormal number | |
100 | with only the implicit leading bit set. The value is | |
101 | in fact a normal number and so we have to treat this | |
102 | case differently. */ | |
103 | #if N == 2 | |
104 | res_ptr[N - 1] = 0x80000000ul; | |
105 | #else | |
106 | res_ptr[0] = 0x8000000000000000ul; | |
107 | #endif | |
108 | *expt = LDBL_MIN_EXP - 1; | |
109 | } | |
ce563359 RM |
110 | } |
111 | } | |
32c075e1 JJ |
112 | else if (u.ieee.exponent < 0x7fff |
113 | #if N == 2 | |
114 | && res_ptr[0] == 0 | |
115 | #endif | |
116 | && res_ptr[N - 1] == 0) | |
117 | /* Pseudo zero. */ | |
118 | *expt = 0; | |
ce563359 RM |
119 | |
120 | return N; | |
121 | } |