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_mul(union ieee754dp x, union ieee754dp y)
13{
14	int re;
15	int rs;
16	u64 rm;
17	unsigned int lxm;
18	unsigned int hxm;
19	unsigned int lym;
20	unsigned int hym;
21	u64 lrm;
22	u64 hrm;
23	u64 t;
24	u64 at;
25
26	COMPXDP;
27	COMPYDP;
28
29	EXPLODEXDP;
30	EXPLODEYDP;
31
32	ieee754_clearcx();
33
34	FLUSHXDP;
35	FLUSHYDP;
36
37	switch (CLPAIR(xc, yc)) {
38	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_SNAN):
39	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_SNAN):
40	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_SNAN):
41	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_SNAN):
42	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_SNAN):
43		return ieee754dp_nanxcpt(y);
44
45	case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_SNAN):
46	case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_QNAN):
47	case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_ZERO):
48	case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_NORM):
49	case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_DNORM):
50	case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_INF):
51		return ieee754dp_nanxcpt(x);
52
53	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_QNAN):
54	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_QNAN):
55	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_QNAN):
56	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_QNAN):
57		return y;
58
59	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_QNAN):
60	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_ZERO):
61	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_NORM):
62	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_DNORM):
63	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_INF):
64		return x;
65
66
67	/*
68	 * Infinity handling
69	 */
70	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_ZERO):
71	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_INF):
72		ieee754_setcx(IEEE754_INVALID_OPERATION);
73		return ieee754dp_indef();
74
75	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_INF):
76	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_INF):
77	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_NORM):
78	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_DNORM):
79	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_INF):
80		return ieee754dp_inf(xs ^ ys);
81
82	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO):
83	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_NORM):
84	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_DNORM):
85	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_ZERO):
86	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO):
87		return ieee754dp_zero(xs ^ ys);
88
89
90	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
91		DPDNORMX;
92		fallthrough;
93	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM):
94		DPDNORMY;
95		break;
96
97	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM):
98		DPDNORMX;
99		break;
100
101	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM):
102		break;
103	}
104	/* rm = xm * ym, re = xe+ye basically */
105	assert(xm & DP_HIDDEN_BIT);
106	assert(ym & DP_HIDDEN_BIT);
107
108	re = xe + ye;
109	rs = xs ^ ys;
110
111	/* shunt to top of word */
112	xm <<= 64 - (DP_FBITS + 1);
113	ym <<= 64 - (DP_FBITS + 1);
114
115	/*
116	 * Multiply 64 bits xm, ym to give high 64 bits rm with stickness.
117	 */
118
119	lxm = xm;
120	hxm = xm >> 32;
121	lym = ym;
122	hym = ym >> 32;
123
124	lrm = DPXMULT(lxm, lym);
125	hrm = DPXMULT(hxm, hym);
126
127	t = DPXMULT(lxm, hym);
128
129	at = lrm + (t << 32);
130	hrm += at < lrm;
131	lrm = at;
132
133	hrm = hrm + (t >> 32);
134
135	t = DPXMULT(hxm, lym);
136
137	at = lrm + (t << 32);
138	hrm += at < lrm;
139	lrm = at;
140
141	hrm = hrm + (t >> 32);
142
143	rm = hrm | (lrm != 0);
144
145	/*
146	 * Sticky shift down to normal rounding precision.
147	 */
148	if ((s64) rm < 0) {
149		rm = (rm >> (64 - (DP_FBITS + 1 + 3))) |
150		     ((rm << (DP_FBITS + 1 + 3)) != 0);
151		re++;
152	} else {
153		rm = (rm >> (64 - (DP_FBITS + 1 + 3 + 1))) |
154		     ((rm << (DP_FBITS + 1 + 3 + 1)) != 0);
155	}
156	assert(rm & (DP_HIDDEN_BIT << 3));
157
158	return ieee754dp_format(rs, re, rm);
159}
160