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review.trustedfirmware.org / hafnium / third_party / linux / 0e64123141f3854e695eb4924d82b52856691466 / . / arch / mips / math-emu / dp_mul.c
blob: e8a97d26472a992e92d1530c05587fd56e318a85 [file] [log] [blame]
David Brazdil0f672f62019-12-10 10:32:29 +0000[diff] [blame]1// SPDX-License-Identifier: GPL-2.0-only
Andrew Scullb4b6d4a2019-01-02 15:54:55 +0000[diff] [blame]2/* IEEE754 floating point arithmetic
3 * double precision: common utilities
4 */
5/*
6 * MIPS floating point support
7 * Copyright (C) 1994-2000 Algorithmics Ltd.
Andrew Scullb4b6d4a2019-01-02 15:54:55 +0000[diff] [blame]8 */
9
10#include "ieee754dp.h"
11
12union ieee754dp ieee754dp_mul(union ieee754dp x, union ieee754dp y)
13{
14 int re;
15 int rs;
16 u64 rm;
17 unsigned int lxm;
18 unsigned int hxm;
19 unsigned int lym;
20 unsigned int hym;
21 u64 lrm;
22 u64 hrm;
23 u64 t;
24 u64 at;
25
26 COMPXDP;
27 COMPYDP;
28
29 EXPLODEXDP;
30 EXPLODEYDP;
31
32 ieee754_clearcx();
33
34 FLUSHXDP;
35 FLUSHYDP;
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 ieee754dp_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 ieee754dp_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 ieee754dp_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 ieee754dp_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 ieee754dp_zero(xs ^ ys);
88
89
90 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
91 DPDNORMX;
92 /* fall through */
93
94 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM):
95 DPDNORMY;
96 break;
97
98 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM):
99 DPDNORMX;
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 & DP_HIDDEN_BIT);
107 assert(ym & DP_HIDDEN_BIT);
108
109 re = xe + ye;
110 rs = xs ^ ys;
111
112 /* shunt to top of word */
113 xm <<= 64 - (DP_FBITS + 1);
114 ym <<= 64 - (DP_FBITS + 1);
115
116 /*
117 * Multiply 64 bits xm, ym to give high 64 bits rm with stickness.
118 */
119
120 lxm = xm;
121 hxm = xm >> 32;
122 lym = ym;
123 hym = ym >> 32;
124
125 lrm = DPXMULT(lxm, lym);
126 hrm = DPXMULT(hxm, hym);
127
128 t = DPXMULT(lxm, hym);
129
130 at = lrm + (t << 32);
131 hrm += at < lrm;
132 lrm = at;
133
134 hrm = hrm + (t >> 32);
135
136 t = DPXMULT(hxm, lym);
137
138 at = lrm + (t << 32);
139 hrm += at < lrm;
140 lrm = at;
141
142 hrm = hrm + (t >> 32);
143
144 rm = hrm | (lrm != 0);
145
146 /*
147 * Sticky shift down to normal rounding precision.
148 */
149 if ((s64) rm < 0) {
150 rm = (rm >> (64 - (DP_FBITS + 1 + 3))) |
151 ((rm << (DP_FBITS + 1 + 3)) != 0);
152 re++;
153 } else {
154 rm = (rm >> (64 - (DP_FBITS + 1 + 3 + 1))) |
155 ((rm << (DP_FBITS + 1 + 3 + 1)) != 0);
156 }
157 assert(rm & (DP_HIDDEN_BIT << 3));
158
159 return ieee754dp_format(rs, re, rm);
160}