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 *  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.,
19 *  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA.
20 */
21
22#include "ieee754dp.h"
23
24int ieee754dp_tint(union ieee754dp x)
25{
26	u64 residue;
27	int round;
28	int sticky;
29	int odd;
30
31	COMPXDP;
32
33	ieee754_clearcx();
34
35	EXPLODEXDP;
36	FLUSHXDP;
37
38	switch (xc) {
39	case IEEE754_CLASS_SNAN:
40	case IEEE754_CLASS_QNAN:
41	case IEEE754_CLASS_INF:
42		ieee754_setcx(IEEE754_INVALID_OPERATION);
43		return ieee754si_indef();
44
45	case IEEE754_CLASS_ZERO:
46		return 0;
47
48	case IEEE754_CLASS_DNORM:
49	case IEEE754_CLASS_NORM:
50		break;
51	}
52	if (xe > 31) {
53		/* Set invalid. We will only use overflow for floating
54		   point overflow */
55		ieee754_setcx(IEEE754_INVALID_OPERATION);
56		return ieee754si_indef();
57	}
58	/* oh gawd */
59	if (xe > DP_FBITS) {
60		xm <<= xe - DP_FBITS;
61	} else if (xe < DP_FBITS) {
62		if (xe < -1) {
63			residue = xm;
64			round = 0;
65			sticky = residue != 0;
66			xm = 0;
67		} else {
68			residue = xm << (64 - DP_FBITS + xe);
69			round = (residue >> 63) != 0;
70			sticky = (residue << 1) != 0;
71			xm >>= DP_FBITS - xe;
72		}
73		/* Note: At this point upper 32 bits of xm are guaranteed
74		   to be zero */
75		odd = (xm & 0x1) != 0x0;
76		switch (ieee754_csr.rm) {
77		case FPU_CSR_RN:
78			if (round && (sticky || odd))
79				xm++;
80			break;
81		case FPU_CSR_RZ:
82			break;
83		case FPU_CSR_RU:	/* toward +Infinity */
84			if ((round || sticky) && !xs)
85				xm++;
86			break;
87		case FPU_CSR_RD:	/* toward -Infinity */
88			if ((round || sticky) && xs)
89				xm++;
90			break;
91		}
92		/* look for valid corner case 0x80000000 */
93		if ((xm >> 31) != 0 && (xs == 0 || xm != 0x80000000)) {
94			/* This can happen after rounding */
95			ieee754_setcx(IEEE754_INVALID_OPERATION);
96			return ieee754si_indef();
97		}
98		if (round || sticky)
99			ieee754_setcx(IEEE754_INEXACT);
100	}
101	if (xs)
102		return -xm;
103	else
104		return xm;
105}
106