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
12 union 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
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