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 
ieee754sp_div(union ieee754sp x,union ieee754sp y)12 union ieee754sp ieee754sp_div(union ieee754sp x, union ieee754sp y)
13 {
14 	unsigned int rm;
15 	int re;
16 	unsigned int bm;
17 
18 	COMPXSP;
19 	COMPYSP;
20 
21 	EXPLODEXSP;
22 	EXPLODEYSP;
23 
24 	ieee754_clearcx();
25 
26 	FLUSHXSP;
27 	FLUSHYSP;
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 ieee754sp_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 ieee754sp_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 ieee754sp_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 ieee754sp_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 ieee754sp_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 ieee754sp_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 ieee754sp_inf(xs ^ ys);
87 
88 	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_NORM):
89 	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_DNORM):
90 		return ieee754sp_zero(xs == ys ? 0 : 1);
91 
92 	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
93 		SPDNORMX;
94 		fallthrough;
95 	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM):
96 		SPDNORMY;
97 		break;
98 
99 	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM):
100 		SPDNORMX;
101 		break;
102 
103 	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM):
104 		break;
105 	}
106 	assert(xm & SP_HIDDEN_BIT);
107 	assert(ym & SP_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 = SP_MBIT(SP_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 	/* normalise rm to rounding precision ?
135 	 */
136 	while ((rm >> (SP_FBITS + 3)) == 0) {
137 		rm <<= 1;
138 		re--;
139 	}
140 
141 	return ieee754sp_format(xs == ys ? 0 : 1, re, rm);
142 }
143