1 /* Copyright (C) 1995-2014 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 quad-precision format to a
27 multi-precision integer representing the significand scaled up by its
28 number of bits (113 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
.mantissa3
; /* Low-order 32 bits of fraction. */
44 res_ptr
[1] = u
.ieee
.mantissa2
;
45 res_ptr
[2] = u
.ieee
.mantissa1
;
46 res_ptr
[3] = u
.ieee
.mantissa0
; /* High-order 32 bits. */
48 #elif BITS_PER_MP_LIMB == 64
49 /* Hopefully the compiler will combine the two bitfield extracts
50 and this composition into just the original quadword extract. */
51 res_ptr
[0] = ((mp_limb_t
) u
.ieee
.mantissa2
<< 32) | u
.ieee
.mantissa3
;
52 res_ptr
[1] = ((mp_limb_t
) u
.ieee
.mantissa0
<< 32) | u
.ieee
.mantissa1
;
55 #error "mp_limb size " BITS_PER_MP_LIMB "not accounted for"
57 /* The format does not fill the last limb. There are some zeros. */
58 #define NUM_LEADING_ZEROS (BITS_PER_MP_LIMB \
59 - (LDBL_MANT_DIG - ((N - 1) * BITS_PER_MP_LIMB)))
61 if (u
.ieee
.exponent
== 0)
63 /* A biased exponent of zero is a special case.
64 Either it is a zero or it is a denormal number. */
65 if (res_ptr
[0] == 0 && res_ptr
[1] == 0
66 && res_ptr
[N
- 2] == 0 && res_ptr
[N
- 1] == 0) /* Assumes N<=4. */
71 /* It is a denormal number, meaning it has no implicit leading
72 one bit, and its exponent is in fact the format minimum. */
76 if (res_ptr
[N
- 1] != 0)
78 count_leading_zeros (cnt
, res_ptr
[N
- 1]);
79 cnt
-= NUM_LEADING_ZEROS
;
80 res_ptr
[N
- 1] = res_ptr
[N
- 1] << cnt
81 | (res_ptr
[0] >> (BITS_PER_MP_LIMB
- cnt
));
83 *expt
= LDBL_MIN_EXP
- 1 - cnt
;
87 count_leading_zeros (cnt
, res_ptr
[0]);
88 if (cnt
>= NUM_LEADING_ZEROS
)
90 res_ptr
[N
- 1] = res_ptr
[0] << (cnt
- NUM_LEADING_ZEROS
);
95 res_ptr
[N
- 1] = res_ptr
[0] >> (NUM_LEADING_ZEROS
- cnt
);
96 res_ptr
[0] <<= BITS_PER_MP_LIMB
- (NUM_LEADING_ZEROS
- cnt
);
98 *expt
= LDBL_MIN_EXP
- 1
99 - (BITS_PER_MP_LIMB
- NUM_LEADING_ZEROS
) - cnt
;
104 for (j
= N
- 1; j
> 0; j
--)
108 count_leading_zeros (cnt
, res_ptr
[j
]);
109 cnt
-= NUM_LEADING_ZEROS
;
113 cnt
+= BITS_PER_MP_LIMB
;
117 for (k
= N
- 1; k
>= l
; k
--)
118 res_ptr
[k
] = res_ptr
[k
-l
];
121 for (k
= N
- 1; k
> l
; k
--)
122 res_ptr
[k
] = res_ptr
[k
-l
] << cnt
123 | res_ptr
[k
-l
-1] >> (BITS_PER_MP_LIMB
- cnt
);
124 res_ptr
[k
--] = res_ptr
[0] << cnt
;
129 *expt
= LDBL_MIN_EXP
- 1 - l
* BITS_PER_MP_LIMB
- cnt
;
134 /* Add the implicit leading one bit for a normalized number. */
135 res_ptr
[N
- 1] |= (mp_limb_t
) 1 << (LDBL_MANT_DIG
- 1
136 - ((N
- 1) * BITS_PER_MP_LIMB
));