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
24union ieee754dp ieee754dp_div(union ieee754dp x, union ieee754dp y)
25{
26	u64 rm;
27	int re;
28	u64 bm;
29
30	COMPXDP;
31	COMPYDP;
32
33	EXPLODEXDP;
34	EXPLODEYDP;
35
36	ieee754_clearcx();
37
38	FLUSHXDP;
39	FLUSHYDP;
40
41	switch (CLPAIR(xc, yc)) {
42	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_SNAN):
43	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_SNAN):
44	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_SNAN):
45	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_SNAN):
46	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_SNAN):
47		return ieee754dp_nanxcpt(y);
48
49	case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_SNAN):
50	case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_QNAN):
51	case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_ZERO):
52	case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_NORM):
53	case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_DNORM):
54	case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_INF):
55		return ieee754dp_nanxcpt(x);
56
57	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_QNAN):
58	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_QNAN):
59	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_QNAN):
60	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_QNAN):
61		return y;
62
63	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_QNAN):
64	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_ZERO):
65	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_NORM):
66	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_DNORM):
67	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_INF):
68		return x;
69
70
71	/*
72	 * Infinity handling
73	 */
74	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_INF):
75		ieee754_setcx(IEEE754_INVALID_OPERATION);
76		return ieee754dp_indef();
77
78	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_INF):
79	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_INF):
80	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_INF):
81		return ieee754dp_zero(xs ^ ys);
82
83	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_ZERO):
84	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_NORM):
85	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_DNORM):
86		return ieee754dp_inf(xs ^ ys);
87
88	/*
89	 * Zero handling
90	 */
91	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO):
92		ieee754_setcx(IEEE754_INVALID_OPERATION);
93		return ieee754dp_indef();
94
95	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_ZERO):
96	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO):
97		ieee754_setcx(IEEE754_ZERO_DIVIDE);
98		return ieee754dp_inf(xs ^ ys);
99
100	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_NORM):
101	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_DNORM):
102		return ieee754dp_zero(xs == ys ? 0 : 1);
103
104	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
105		DPDNORMX;
106
107	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM):
108		DPDNORMY;
109		break;
110
111	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM):
112		DPDNORMX;
113		break;
114
115	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM):
116		break;
117	}
118	assert(xm & DP_HIDDEN_BIT);
119	assert(ym & DP_HIDDEN_BIT);
120
121	/* provide rounding space */
122	xm <<= 3;
123	ym <<= 3;
124
125	/* now the dirty work */
126
127	rm = 0;
128	re = xe - ye;
129
130	for (bm = DP_MBIT(DP_FBITS + 2); bm; bm >>= 1) {
131		if (xm >= ym) {
132			xm -= ym;
133			rm |= bm;
134			if (xm == 0)
135				break;
136		}
137		xm <<= 1;
138	}
139
140	rm <<= 1;
141	if (xm)
142		rm |= 1;	/* have remainder, set sticky */
143
144	assert(rm);
145
146	/*
147	 * Normalise rm to rounding precision ?
148	 */
149	while ((rm >> (DP_FBITS + 3)) == 0) {
150		rm <<= 1;
151		re--;
152	}
153
154	return ieee754dp_format(xs == ys ? 0 : 1, re, rm);
155}
156