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_mul(union ieee754sp x,union ieee754sp y)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 /* fall through */
93
94 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM):
95 SPDNORMY;
96 break;
97
98 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM):
99 SPDNORMX;
100 break;
101
102 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM):
103 break;
104 }
105 /* rm = xm * ym, re = xe+ye basically */
106 assert(xm & SP_HIDDEN_BIT);
107 assert(ym & SP_HIDDEN_BIT);
108
109 re = xe + ye;
110 rs = xs ^ ys;
111
112 /* shunt to top of word */
113 xm <<= 32 - (SP_FBITS + 1);
114 ym <<= 32 - (SP_FBITS + 1);
115
116 /*
117 * Multiply 32 bits xm, ym to give high 32 bits rm with stickness.
118 */
119 lxm = xm & 0xffff;
120 hxm = xm >> 16;
121 lym = ym & 0xffff;
122 hym = ym >> 16;
123
124 lrm = lxm * lym; /* 16 * 16 => 32 */
125 hrm = hxm * hym; /* 16 * 16 => 32 */
126
127 t = lxm * hym; /* 16 * 16 => 32 */
128 at = lrm + (t << 16);
129 hrm += at < lrm;
130 lrm = at;
131 hrm = hrm + (t >> 16);
132
133 t = hxm * lym; /* 16 * 16 => 32 */
134 at = lrm + (t << 16);
135 hrm += at < lrm;
136 lrm = at;
137 hrm = hrm + (t >> 16);
138
139 rm = hrm | (lrm != 0);
140
141 /*
142 * Sticky shift down to normal rounding precision.
143 */
144 if ((int) rm < 0) {
145 rm = (rm >> (32 - (SP_FBITS + 1 + 3))) |
146 ((rm << (SP_FBITS + 1 + 3)) != 0);
147 re++;
148 } else {
149 rm = (rm >> (32 - (SP_FBITS + 1 + 3 + 1))) |
150 ((rm << (SP_FBITS + 1 + 3 + 1)) != 0);
151 }
152 assert(rm & (SP_HIDDEN_BIT << 3));
153
154 return ieee754sp_format(rs, re, rm);
155 }
156