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1da177e4 LT |
1 | /* IEEE754 floating point arithmetic |
2 | * double precision: common utilities | |
3 | */ | |
4 | /* | |
5 | * MIPS floating point support | |
6 | * Copyright (C) 1994-2000 Algorithmics Ltd. | |
7 | * http://www.algor.co.uk | |
8 | * | |
9 | * ######################################################################## | |
10 | * | |
11 | * This program is free software; you can distribute it and/or modify it | |
12 | * under the terms of the GNU General Public License (Version 2) as | |
13 | * published by the Free Software Foundation. | |
14 | * | |
15 | * This program is distributed in the hope it will be useful, but WITHOUT | |
16 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | |
17 | * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | |
18 | * for more details. | |
19 | * | |
20 | * You should have received a copy of the GNU General Public License along | |
21 | * with this program; if not, write to the Free Software Foundation, Inc., | |
22 | * 59 Temple Place - Suite 330, Boston MA 02111-1307, USA. | |
23 | * | |
24 | * ######################################################################## | |
25 | */ | |
26 | ||
27 | ||
28 | #include "ieee754dp.h" | |
29 | ||
30 | /* modf function is always exact for a finite number | |
31 | */ | |
32 | ieee754dp ieee754dp_modf(ieee754dp x, ieee754dp * ip) | |
33 | { | |
34 | COMPXDP; | |
35 | ||
36 | CLEARCX; | |
37 | ||
38 | EXPLODEXDP; | |
39 | ||
40 | switch (xc) { | |
41 | case IEEE754_CLASS_SNAN: | |
42 | case IEEE754_CLASS_QNAN: | |
43 | case IEEE754_CLASS_INF: | |
44 | case IEEE754_CLASS_ZERO: | |
45 | *ip = x; | |
46 | return x; | |
47 | case IEEE754_CLASS_DNORM: | |
48 | /* far to small */ | |
49 | *ip = ieee754dp_zero(xs); | |
50 | return x; | |
51 | case IEEE754_CLASS_NORM: | |
52 | break; | |
53 | } | |
54 | if (xe < 0) { | |
55 | *ip = ieee754dp_zero(xs); | |
56 | return x; | |
57 | } | |
58 | if (xe >= DP_MBITS) { | |
59 | *ip = x; | |
60 | return ieee754dp_zero(xs); | |
61 | } | |
62 | /* generate ipart mantissa by clearing bottom bits | |
63 | */ | |
64 | *ip = builddp(xs, xe + DP_EBIAS, | |
65 | ((xm >> (DP_MBITS - xe)) << (DP_MBITS - xe)) & | |
66 | ~DP_HIDDEN_BIT); | |
67 | ||
68 | /* generate fpart mantissa by clearing top bits | |
69 | * and normalizing (must be able to normalize) | |
70 | */ | |
71 | xm = (xm << (64 - (DP_MBITS - xe))) >> (64 - (DP_MBITS - xe)); | |
72 | if (xm == 0) | |
73 | return ieee754dp_zero(xs); | |
74 | ||
75 | while ((xm >> DP_MBITS) == 0) { | |
76 | xm <<= 1; | |
77 | xe--; | |
78 | } | |
79 | return builddp(xs, xe + DP_EBIAS, xm & ~DP_HIDDEN_BIT); | |
80 | } |