1// SPDX-License-Identifier: GPL-2.0-only
2/* IEEE754 floating point arithmetic
3 * single precision
4 */
5/*
6 * MIPS floating point support
7 * Copyright (C) 1994-2000 Algorithmics Ltd.
8 */
9
10#include "ieee754sp.h"
11
12union ieee754sp ieee754sp_mul(union ieee754sp x, union ieee754sp y)
13{
14	int re;
15	int rs;
16	unsigned int rm;
17	unsigned short lxm;
18	unsigned short hxm;
19	unsigned short lym;
20	unsigned short hym;
21	unsigned int lrm;
22	unsigned int hrm;
23	unsigned int t;
24	unsigned int at;
25
26	COMPXSP;
27	COMPYSP;
28
29	EXPLODEXSP;
30	EXPLODEYSP;
31
32	ieee754_clearcx();
33
34	FLUSHXSP;
35	FLUSHYSP;
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 ieee754sp_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 ieee754sp_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 ieee754sp_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 ieee754sp_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 ieee754sp_zero(xs ^ ys);
88
89
90	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
91		SPDNORMX;
92		fallthrough;
93	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM):
94		SPDNORMY;
95		break;
96
97	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM):
98		SPDNORMX;
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 & SP_HIDDEN_BIT);
106	assert(ym & SP_HIDDEN_BIT);
107
108	re = xe + ye;
109	rs = xs ^ ys;
110
111	/* shunt to top of word */
112	xm <<= 32 - (SP_FBITS + 1);
113	ym <<= 32 - (SP_FBITS + 1);
114
115	/*
116	 * Multiply 32 bits xm, ym to give high 32 bits rm with stickness.
117	 */
118	lxm = xm & 0xffff;
119	hxm = xm >> 16;
120	lym = ym & 0xffff;
121	hym = ym >> 16;
122
123	lrm = lxm * lym;	/* 16 * 16 => 32 */
124	hrm = hxm * hym;	/* 16 * 16 => 32 */
125
126	t = lxm * hym; /* 16 * 16 => 32 */
127	at = lrm + (t << 16);
128	hrm += at < lrm;
129	lrm = at;
130	hrm = hrm + (t >> 16);
131
132	t = hxm * lym; /* 16 * 16 => 32 */
133	at = lrm + (t << 16);
134	hrm += at < lrm;
135	lrm = at;
136	hrm = hrm + (t >> 16);
137
138	rm = hrm | (lrm != 0);
139
140	/*
141	 * Sticky shift down to normal rounding precision.
142	 */
143	if ((int) rm < 0) {
144		rm = (rm >> (32 - (SP_FBITS + 1 + 3))) |
145		    ((rm << (SP_FBITS + 1 + 3)) != 0);
146		re++;
147	} else {
148		rm = (rm >> (32 - (SP_FBITS + 1 + 3 + 1))) |
149		     ((rm << (SP_FBITS + 1 + 3 + 1)) != 0);
150	}
151	assert(rm & (SP_HIDDEN_BIT << 3));
152
153	return ieee754sp_format(rs, re, rm);
154}
155