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review.trustedfirmware.org / hafnium / third_party / linux / b4b6d4a02fa8aa8187d426b508fb7f3b69df0dcc / . / arch / mips / math-emu / dp_div.c
blob: 3063ae3ab3b9a0c94ce08fa007e34cd924bedf47 [file] [log] [blame]
Andrew Scullb4b6d4a2019-01-02 15:54:55 +0000[diff] [blame^]1/* IEEE754 floating point arithmetic
2 * double precision: common utilities
3 */
4/*
5 * MIPS floating point support
6 * Copyright (C) 1994-2000 Algorithmics Ltd.
7 *
8 * This program is free software; you can distribute it and/or modify it
9 * under the terms of the GNU General Public License (Version 2) as
10 * published by the Free Software Foundation.
11 *
12 * This program is distributed in the hope it will be useful, but WITHOUT
13 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
14 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
15 * for more details.
16 *
17 * You should have received a copy of the GNU General Public License along
18 * with this program; if not, write to the Free Software Foundation, Inc.,
19 * 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 */
21
22#include "ieee754dp.h"
23
24union ieee754dp ieee754dp_div(union ieee754dp x, union ieee754dp y)
25{
26 u64 rm;
27 int re;
28 u64 bm;
29
30 COMPXDP;
31 COMPYDP;
32
33 EXPLODEXDP;
34 EXPLODEYDP;
35
36 ieee754_clearcx();
37
38 FLUSHXDP;
39 FLUSHYDP;
40
41 switch (CLPAIR(xc, yc)) {
42 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_SNAN):
43 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_SNAN):
44 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_SNAN):
45 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_SNAN):
46 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_SNAN):
47 return ieee754dp_nanxcpt(y);
48
49 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_SNAN):
50 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_QNAN):
51 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_ZERO):
52 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_NORM):
53 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_DNORM):
54 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_INF):
55 return ieee754dp_nanxcpt(x);
56
57 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_QNAN):
58 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_QNAN):
59 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_QNAN):
60 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_QNAN):
61 return y;
62
63 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_QNAN):
64 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_ZERO):
65 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_NORM):
66 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_DNORM):
67 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_INF):
68 return x;
69
70
71 /*
72 * Infinity handling
73 */
74 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_INF):
75 ieee754_setcx(IEEE754_INVALID_OPERATION);
76 return ieee754dp_indef();
77
78 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_INF):
79 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_INF):
80 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_INF):
81 return ieee754dp_zero(xs ^ ys);
82
83 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_ZERO):
84 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_NORM):
85 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_DNORM):
86 return ieee754dp_inf(xs ^ ys);
87
88 /*
89 * Zero handling
90 */
91 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO):
92 ieee754_setcx(IEEE754_INVALID_OPERATION);
93 return ieee754dp_indef();
94
95 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_ZERO):
96 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO):
97 ieee754_setcx(IEEE754_ZERO_DIVIDE);
98 return ieee754dp_inf(xs ^ ys);
99
100 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_NORM):
101 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_DNORM):
102 return ieee754dp_zero(xs == ys ? 0 : 1);
103
104 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
105 DPDNORMX;
106 /* fall through */
107
108 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM):
109 DPDNORMY;
110 break;
111
112 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM):
113 DPDNORMX;
114 break;
115
116 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM):
117 break;
118 }
119 assert(xm & DP_HIDDEN_BIT);
120 assert(ym & DP_HIDDEN_BIT);
121
122 /* provide rounding space */
123 xm <<= 3;
124 ym <<= 3;
125
126 /* now the dirty work */
127
128 rm = 0;
129 re = xe - ye;
130
131 for (bm = DP_MBIT(DP_FBITS + 2); bm; bm >>= 1) {
132 if (xm >= ym) {
133 xm -= ym;
134 rm |= bm;
135 if (xm == 0)
136 break;
137 }
138 xm <<= 1;
139 }
140
141 rm <<= 1;
142 if (xm)
143 rm |= 1; /* have remainder, set sticky */
144
145 assert(rm);
146
147 /*
148 * Normalise rm to rounding precision ?
149 */
150 while ((rm >> (DP_FBITS + 3)) == 0) {
151 rm <<= 1;
152 re--;
153 }
154
155 return ieee754dp_format(xs == ys ? 0 : 1, re, rm);
156}