1 /* Copyright (C) 1995,1996,1997,1998,1999,2002,2003
2 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, write to the Free
17 Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
28 /* Convert a `long double' in IEEE854 quad-precision format to a
29 multi-precision integer representing the significand scaled up by its
30 number of bits (113 for long double) and an integral power of two
34 __mpn_extract_long_double (mp_ptr res_ptr
, mp_size_t size
,
35 int *expt
, int *is_neg
,
38 union ieee854_long_double u
;
41 *is_neg
= u
.ieee
.negative
;
42 *expt
= (int) u
.ieee
.exponent
- IEEE854_LONG_DOUBLE_BIAS
;
44 #if BITS_PER_MP_LIMB == 32
45 res_ptr
[0] = u
.ieee
.mantissa3
; /* Low-order 32 bits of fraction. */
46 res_ptr
[1] = u
.ieee
.mantissa2
;
47 res_ptr
[2] = u
.ieee
.mantissa1
;
48 res_ptr
[3] = u
.ieee
.mantissa0
; /* High-order 32 bits. */
50 #elif BITS_PER_MP_LIMB == 64
51 /* Hopefully the compiler will combine the two bitfield extracts
52 and this composition into just the original quadword extract. */
53 res_ptr
[0] = ((mp_limb_t
) u
.ieee
.mantissa2
<< 32) | u
.ieee
.mantissa3
;
54 res_ptr
[1] = ((mp_limb_t
) u
.ieee
.mantissa0
<< 32) | u
.ieee
.mantissa1
;
57 #error "mp_limb size " BITS_PER_MP_LIMB "not accounted for"
59 /* The format does not fill the last limb. There are some zeros. */
60 #define NUM_LEADING_ZEROS (BITS_PER_MP_LIMB \
61 - (LDBL_MANT_DIG - ((N - 1) * BITS_PER_MP_LIMB)))
63 if (u
.ieee
.exponent
== 0)
65 /* A biased exponent of zero is a special case.
66 Either it is a zero or it is a denormal number. */
67 if (res_ptr
[0] == 0 && res_ptr
[1] == 0
68 && res_ptr
[N
- 2] == 0 && res_ptr
[N
- 1] == 0) /* Assumes N<=4. */
73 /* It is a denormal number, meaning it has no implicit leading
74 one bit, and its exponent is in fact the format minimum. */
78 if (res_ptr
[N
- 1] != 0)
80 count_leading_zeros (cnt
, res_ptr
[N
- 1]);
81 cnt
-= NUM_LEADING_ZEROS
;
82 res_ptr
[N
- 1] = res_ptr
[N
- 1] << cnt
83 | (res_ptr
[0] >> (BITS_PER_MP_LIMB
- cnt
));
85 *expt
= LDBL_MIN_EXP
- 1 - cnt
;
89 count_leading_zeros (cnt
, res_ptr
[0]);
90 if (cnt
>= NUM_LEADING_ZEROS
)
92 res_ptr
[N
- 1] = res_ptr
[0] << (cnt
- NUM_LEADING_ZEROS
);
97 res_ptr
[N
- 1] = res_ptr
[0] >> (NUM_LEADING_ZEROS
- cnt
);
98 res_ptr
[0] <<= BITS_PER_MP_LIMB
- (NUM_LEADING_ZEROS
- cnt
);
100 *expt
= LDBL_MIN_EXP
- 1
101 - (BITS_PER_MP_LIMB
- NUM_LEADING_ZEROS
) - cnt
;
106 for (j
= N
- 1; j
> 0; j
--)
110 count_leading_zeros (cnt
, res_ptr
[j
]);
111 cnt
-= NUM_LEADING_ZEROS
;
115 cnt
+= BITS_PER_MP_LIMB
;
119 for (k
= N
- 1; k
>= l
; k
--)
120 res_ptr
[k
] = res_ptr
[k
-l
];
123 for (k
= N
- 1; k
> l
; k
--)
124 res_ptr
[k
] = res_ptr
[k
-l
] << cnt
125 | res_ptr
[k
-l
-1] >> (BITS_PER_MP_LIMB
- cnt
);
126 res_ptr
[k
--] = res_ptr
[0] << cnt
;
131 *expt
= LDBL_MIN_EXP
- 1 - l
* BITS_PER_MP_LIMB
- cnt
;
136 /* Add the implicit leading one bit for a normalized number. */
137 res_ptr
[N
- 1] |= (mp_limb_t
) 1 << (LDBL_MANT_DIG
- 1
138 - ((N
- 1) * BITS_PER_MP_LIMB
));