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*/
32ieee754dp 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}
81