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