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*/
31ieee754dp 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}