1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
|
/* IEEE754 floating point arithmetic
* single precision square root
*/
/*
* MIPS floating point support
* Copyright (C) 1994-2000 Algorithmics Ltd. All rights reserved.
* http://www.algor.co.uk
*
* ########################################################################
*
* This program is free software; you can distribute it and/or modify it
* under the terms of the GNU General Public License (Version 2) as
* published by the Free Software Foundation.
*
* This program is distributed in the hope it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 59 Temple Place - Suite 330, Boston MA 02111-1307, USA.
*
* ########################################################################
*/
#include "ieee754sp.h"
static const struct ieee754sp_konst knan = {
0, SP_EBIAS + SP_EMAX + 1, 0
};
#define nan ((ieee754sp)knan)
ieee754sp ieee754sp_sqrt(ieee754sp x)
{
int sign = (int) 0x80000000;
int ix, s, q, m, t, i;
unsigned int r;
COMPXDP;
/* take care of Inf and NaN */
EXPLODEXDP;
/* x == INF or NAN? */
switch (xc) {
case IEEE754_CLASS_QNAN:
case IEEE754_CLASS_SNAN:
/* sqrt(Nan) = Nan */
return ieee754sp_nanxcpt(x, "sqrt");
case IEEE754_CLASS_ZERO:
/* sqrt(0) = 0 */
return x;
case IEEE754_CLASS_INF:
if (xs)
/* sqrt(-Inf) = Nan */
return ieee754sp_nanxcpt(nan, "sqrt");
/* sqrt(+Inf) = Inf */
return x;
case IEEE754_CLASS_DNORM:
case IEEE754_CLASS_NORM:
if (xs)
/* sqrt(-x) = Nan */
return ieee754sp_nanxcpt(nan, "sqrt");
break;
}
ix = x.bits;
/* normalize x */
m = (ix >> 23);
if (m == 0) { /* subnormal x */
for (i = 0; (ix & 0x00800000) == 0; i++)
ix <<= 1;
m -= i - 1;
}
m -= 127; /* unbias exponent */
ix = (ix & 0x007fffff) | 0x00800000;
if (m & 1) /* odd m, double x to make it even */
ix += ix;
m >>= 1; /* m = [m/2] */
/* generate sqrt(x) bit by bit */
ix += ix;
q = s = 0; /* q = sqrt(x) */
r = 0x01000000; /* r = moving bit from right to left */
while (r != 0) {
t = s + r;
if (t <= ix) {
s = t + r;
ix -= t;
q += r;
}
ix += ix;
r >>= 1;
}
if (ix != 0) {
switch (ieee754_csr.rm) {
case IEEE754_RP:
q += 2;
break;
case IEEE754_RN:
q += (q & 1);
break;
}
}
ix = (q >> 1) + 0x3f000000;
ix += (m << 23);
x.bits = ix;
return x;
}
|
