Commit | Line | Data |
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1da177e4 LT |
1 | /* IEEE754 floating point arithmetic |
2 | * single precision square root | |
3 | */ | |
4 | /* | |
5 | * MIPS floating point support | |
6 | * Copyright (C) 1994-2000 Algorithmics Ltd. | |
1da177e4 | 7 | * |
1da177e4 LT |
8 | * This program is free software; you can distribute it and/or modify it |
9 | * under the terms of the GNU General Public License (Version 2) as | |
10 | * published by the Free Software Foundation. | |
11 | * | |
12 | * This program is distributed in the hope it will be useful, but WITHOUT | |
13 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | |
14 | * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | |
15 | * for more details. | |
16 | * | |
17 | * You should have received a copy of the GNU General Public License along | |
18 | * with this program; if not, write to the Free Software Foundation, Inc., | |
3f7cac41 | 19 | * 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
1da177e4 LT |
20 | */ |
21 | ||
1da177e4 LT |
22 | #include "ieee754sp.h" |
23 | ||
2209bcb1 | 24 | union ieee754sp ieee754sp_sqrt(union ieee754sp x) |
1da177e4 LT |
25 | { |
26 | int ix, s, q, m, t, i; | |
27 | unsigned int r; | |
28 | COMPXSP; | |
29 | ||
30 | /* take care of Inf and NaN */ | |
31 | ||
32 | EXPLODEXSP; | |
9e8bad1f | 33 | ieee754_clearcx(); |
1da177e4 LT |
34 | FLUSHXSP; |
35 | ||
36 | /* x == INF or NAN? */ | |
37 | switch (xc) { | |
d5afa7e9 MR |
38 | case IEEE754_CLASS_SNAN: |
39 | return ieee754sp_nanxcpt(x); | |
40 | ||
1da177e4 LT |
41 | case IEEE754_CLASS_QNAN: |
42 | /* sqrt(Nan) = Nan */ | |
539bfb57 | 43 | return x; |
3f7cac41 | 44 | |
1da177e4 LT |
45 | case IEEE754_CLASS_ZERO: |
46 | /* sqrt(0) = 0 */ | |
47 | return x; | |
3f7cac41 | 48 | |
1da177e4 LT |
49 | case IEEE754_CLASS_INF: |
50 | if (xs) { | |
51 | /* sqrt(-Inf) = Nan */ | |
9e8bad1f | 52 | ieee754_setcx(IEEE754_INVALID_OPERATION); |
539bfb57 | 53 | return ieee754sp_indef(); |
1da177e4 LT |
54 | } |
55 | /* sqrt(+Inf) = Inf */ | |
56 | return x; | |
3f7cac41 | 57 | |
1da177e4 LT |
58 | case IEEE754_CLASS_DNORM: |
59 | case IEEE754_CLASS_NORM: | |
60 | if (xs) { | |
61 | /* sqrt(-x) = Nan */ | |
9e8bad1f | 62 | ieee754_setcx(IEEE754_INVALID_OPERATION); |
539bfb57 | 63 | return ieee754sp_indef(); |
1da177e4 LT |
64 | } |
65 | break; | |
66 | } | |
67 | ||
68 | ix = x.bits; | |
69 | ||
70 | /* normalize x */ | |
71 | m = (ix >> 23); | |
72 | if (m == 0) { /* subnormal x */ | |
73 | for (i = 0; (ix & 0x00800000) == 0; i++) | |
74 | ix <<= 1; | |
75 | m -= i - 1; | |
76 | } | |
77 | m -= 127; /* unbias exponent */ | |
78 | ix = (ix & 0x007fffff) | 0x00800000; | |
79 | if (m & 1) /* odd m, double x to make it even */ | |
80 | ix += ix; | |
81 | m >>= 1; /* m = [m/2] */ | |
82 | ||
83 | /* generate sqrt(x) bit by bit */ | |
84 | ix += ix; | |
85 | q = s = 0; /* q = sqrt(x) */ | |
86 | r = 0x01000000; /* r = moving bit from right to left */ | |
87 | ||
88 | while (r != 0) { | |
89 | t = s + r; | |
90 | if (t <= ix) { | |
91 | s = t + r; | |
92 | ix -= t; | |
93 | q += r; | |
94 | } | |
95 | ix += ix; | |
96 | r >>= 1; | |
97 | } | |
98 | ||
99 | if (ix != 0) { | |
9e8bad1f | 100 | ieee754_setcx(IEEE754_INEXACT); |
1da177e4 | 101 | switch (ieee754_csr.rm) { |
56a64733 | 102 | case FPU_CSR_RU: |
1da177e4 LT |
103 | q += 2; |
104 | break; | |
56a64733 | 105 | case FPU_CSR_RN: |
1da177e4 LT |
106 | q += (q & 1); |
107 | break; | |
108 | } | |
109 | } | |
110 | ix = (q >> 1) + 0x3f000000; | |
111 | ix += (m << 23); | |
112 | x.bits = ix; | |
113 | return x; | |
114 | } |