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
30ieee754dp ieee754dp_div(ieee754dp x, ieee754dp y)
31{
32	COMPXDP;
33	COMPYDP;
34
35	EXPLODEXDP;
36	EXPLODEYDP;
37
38	CLEARCX;
39
40	FLUSHXDP;
41	FLUSHYDP;
42
43	switch (CLPAIR(xc, yc)) {
44	case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_QNAN):
45	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_SNAN):
46	case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_SNAN):
47	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_SNAN):
48	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_SNAN):
49	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_SNAN):
50	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_SNAN):
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		SETCX(IEEE754_INVALID_OPERATION);
56		return ieee754dp_nanxcpt(ieee754dp_indef(), "div", x, y);
57
58	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_QNAN):
59	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_QNAN):
60	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_QNAN):
61	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_QNAN):
62		return y;
63
64	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_QNAN):
65	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_ZERO):
66	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_NORM):
67	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_DNORM):
68	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_INF):
69		return x;
70
71
72		/* Infinity handling
73		 */
74
75	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_INF):
76		SETCX(IEEE754_INVALID_OPERATION);
77		return ieee754dp_xcpt(ieee754dp_indef(), "div", x, y);
78
79	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_INF):
80	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_INF):
81	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_INF):
82		return ieee754dp_zero(xs ^ ys);
83
84	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_ZERO):
85	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_NORM):
86	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_DNORM):
87		return ieee754dp_inf(xs ^ ys);
88
89		/* Zero handling
90		 */
91
92	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO):
93		SETCX(IEEE754_INVALID_OPERATION);
94		return ieee754dp_xcpt(ieee754dp_indef(), "div", x, y);
95
96	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_ZERO):
97	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO):
98		SETCX(IEEE754_ZERO_DIVIDE);
99		return ieee754dp_xcpt(ieee754dp_inf(xs ^ ys), "div", x, y);
100
101	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_NORM):
102	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_DNORM):
103		return ieee754dp_zero(xs == ys ? 0 : 1);
104
105	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
106		DPDNORMX;
107
108	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM):
109		DPDNORMY;
110		break;
111
112	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM):
113		DPDNORMX;
114		break;
115
116	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM):
117		break;
118	}
119	assert(xm & DP_HIDDEN_BIT);
120	assert(ym & DP_HIDDEN_BIT);
121
122	/* provide rounding space */
123	xm <<= 3;
124	ym <<= 3;
125
126	{
127		/* now the dirty work */
128
129		u64 rm = 0;
130		int re = xe - ye;
131		u64 bm;
132
133		for (bm = DP_MBIT(DP_MBITS + 2); bm; bm >>= 1) {
134			if (xm >= ym) {
135				xm -= ym;
136				rm |= bm;
137				if (xm == 0)
138					break;
139			}
140			xm <<= 1;
141		}
142		rm <<= 1;
143		if (xm)
144			rm |= 1;	/* have remainder, set sticky */
145
146		assert(rm);
147
148		/* normalise rm to rounding precision ?
149		 */
150		while ((rm >> (DP_MBITS + 3)) == 0) {
151			rm <<= 1;
152			re--;
153		}
154
155		DPNORMRET2(xs == ys ? 0 : 1, re, rm, "div", x, y);
156	}
157}
158