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
12 union 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
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