1 /* Copyright (C) 1995-2015 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
4 The GNU C Library is free software; you can redistribute it and/or
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.
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
12 Lesser General Public License for more details.
14 You should have received a copy of the GNU Lesser General Public
15 License along with the GNU C Library; if not, see
16 <http://www.gnu.org/licenses/>. */
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
32 __mpn_extract_long_double (mp_ptr res_ptr
, mp_size_t size
,
33 int *expt
, int *is_neg
,
36 union ieee854_long_double u
;
39 *is_neg
= u
.ieee
.negative
;
40 *expt
= (int) u
.ieee
.exponent
- IEEE854_LONG_DOUBLE_BIAS
;
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. */
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. */
49 res_ptr
[0] = ((mp_limb_t
) u
.ieee
.mantissa0
<< 32) | u
.ieee
.mantissa1
;
52 #error "mp_limb size " BITS_PER_MP_LIMB "not accounted for"
55 if (u
.ieee
.exponent
== 0)
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. */
64 /* It is a denormal number, meaning it has no implicit leading
65 one bit, and its exponent is in fact the format minimum. */
68 if (res_ptr
[N
- 1] != 0)
70 count_leading_zeros (cnt
, res_ptr
[N
- 1]);
74 res_ptr
[N
- 1] = res_ptr
[N
- 1] << cnt
75 | (res_ptr
[0] >> (BITS_PER_MP_LIMB
- cnt
));
78 res_ptr
[N
- 1] <<= cnt
;
81 *expt
= LDBL_MIN_EXP
- 1 - cnt
;
85 count_leading_zeros (cnt
, res_ptr
[0]);
86 res_ptr
[N
- 1] = res_ptr
[0] << cnt
;
88 *expt
= LDBL_MIN_EXP
- 1 - BITS_PER_MP_LIMB
- cnt
;