1// SPDX-License-Identifier: GPL-2.0-only
2/* IEEE754 floating point arithmetic
3 * double precision: common utilities
4 */
5/*
6 * MIPS floating point support
7 * Copyright (C) 1994-2000 Algorithmics Ltd.
8 */
9
10#include "ieee754dp.h"
11
12union ieee754dp ieee754dp_div(union ieee754dp x, union ieee754dp y)
13{
14	u64 rm;
15	int re;
16	u64 bm;
17
18	COMPXDP;
19	COMPYDP;
20
21	EXPLODEXDP;
22	EXPLODEYDP;
23
24	ieee754_clearcx();
25
26	FLUSHXDP;
27	FLUSHYDP;
28
29	switch (CLPAIR(xc, yc)) {
30	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_SNAN):
31	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_SNAN):
32	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_SNAN):
33	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_SNAN):
34	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_SNAN):
35		return ieee754dp_nanxcpt(y);
36
37	case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_SNAN):
38	case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_QNAN):
39	case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_ZERO):
40	case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_NORM):
41	case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_DNORM):
42	case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_INF):
43		return ieee754dp_nanxcpt(x);
44
45	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_QNAN):
46	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_QNAN):
47	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_QNAN):
48	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_QNAN):
49		return y;
50
51	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_QNAN):
52	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_ZERO):
53	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_NORM):
54	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_DNORM):
55	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_INF):
56		return x;
57
58
59	/*
60	 * Infinity handling
61	 */
62	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_INF):
63		ieee754_setcx(IEEE754_INVALID_OPERATION);
64		return ieee754dp_indef();
65
66	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_INF):
67	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_INF):
68	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_INF):
69		return ieee754dp_zero(xs ^ ys);
70
71	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_ZERO):
72	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_NORM):
73	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_DNORM):
74		return ieee754dp_inf(xs ^ ys);
75
76	/*
77	 * Zero handling
78	 */
79	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO):
80		ieee754_setcx(IEEE754_INVALID_OPERATION);
81		return ieee754dp_indef();
82
83	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_ZERO):
84	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO):
85		ieee754_setcx(IEEE754_ZERO_DIVIDE);
86		return ieee754dp_inf(xs ^ ys);
87
88	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_NORM):
89	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_DNORM):
90		return ieee754dp_zero(xs == ys ? 0 : 1);
91
92	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
93		DPDNORMX;
94		fallthrough;
95	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM):
96		DPDNORMY;
97		break;
98
99	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM):
100		DPDNORMX;
101		break;
102
103	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM):
104		break;
105	}
106	assert(xm & DP_HIDDEN_BIT);
107	assert(ym & DP_HIDDEN_BIT);
108
109	/* provide rounding space */
110	xm <<= 3;
111	ym <<= 3;
112
113	/* now the dirty work */
114
115	rm = 0;
116	re = xe - ye;
117
118	for (bm = DP_MBIT(DP_FBITS + 2); bm; bm >>= 1) {
119		if (xm >= ym) {
120			xm -= ym;
121			rm |= bm;
122			if (xm == 0)
123				break;
124		}
125		xm <<= 1;
126	}
127
128	rm <<= 1;
129	if (xm)
130		rm |= 1;	/* have remainder, set sticky */
131
132	assert(rm);
133
134	/*
135	 * Normalise rm to rounding precision ?
136	 */
137	while ((rm >> (DP_FBITS + 3)) == 0) {
138		rm <<= 1;
139		re--;
140	}
141
142	return ieee754dp_format(xs == ys ? 0 : 1, re, rm);
143}
144