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Thomas Gleixner9d5a6342019-05-31 01:09:55 -07001// SPDX-License-Identifier: GPL-2.0-only
Linus Torvalds1da177e2005-04-16 15:20:36 -07002/* IEEE754 floating point arithmetic
3 * double precision: common utilities
4 */
5/*
6 * MIPS floating point support
7 * Copyright (C) 1994-2000 Algorithmics Ltd.
Linus Torvalds1da177e2005-04-16 15:20:36 -07008 */
9
Linus Torvalds1da177e2005-04-16 15:20:36 -070010#include "ieee754dp.h"
11
Ralf Baechle2209bcb2014-04-16 01:31:11 +020012union ieee754dp ieee754dp_div(union ieee754dp x, union ieee754dp y)
Linus Torvalds1da177e2005-04-16 15:20:36 -070013{
Ralf Baechle3f7cac42014-04-26 01:49:14 +020014 u64 rm;
15 int re;
16 u64 bm;
17
Linus Torvalds1da177e2005-04-16 15:20:36 -070018 COMPXDP;
19 COMPYDP;
20
21 EXPLODEXDP;
22 EXPLODEYDP;
23
Ralf Baechle9e8bad12014-04-19 00:36:32 +020024 ieee754_clearcx();
Linus Torvalds1da177e2005-04-16 15:20:36 -070025
26 FLUSHXDP;
27 FLUSHYDP;
28
29 switch (CLPAIR(xc, yc)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -070030 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_SNAN):
Linus Torvalds1da177e2005-04-16 15:20:36 -070031 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):
Maciej W. Rozyckid5afa7e2015-04-03 23:25:34 +010035 return ieee754dp_nanxcpt(y);
36
37 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_SNAN):
38 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_QNAN):
Linus Torvalds1da177e2005-04-16 15:20:36 -070039 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):
Maciej W. Rozyckid5afa7e2015-04-03 23:25:34 +010043 return ieee754dp_nanxcpt(x);
Linus Torvalds1da177e2005-04-16 15:20:36 -070044
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
Ralf Baechle3f7cac42014-04-26 01:49:14 +020059 /*
60 * Infinity handling
61 */
Linus Torvalds1da177e2005-04-16 15:20:36 -070062 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_INF):
Ralf Baechle9e8bad12014-04-19 00:36:32 +020063 ieee754_setcx(IEEE754_INVALID_OPERATION);
Ralf Baechle90efba32014-04-25 03:19:57 +020064 return ieee754dp_indef();
Linus Torvalds1da177e2005-04-16 15:20:36 -070065
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
Ralf Baechle3f7cac42014-04-26 01:49:14 +020076 /*
77 * Zero handling
78 */
Linus Torvalds1da177e2005-04-16 15:20:36 -070079 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO):
Ralf Baechle9e8bad12014-04-19 00:36:32 +020080 ieee754_setcx(IEEE754_INVALID_OPERATION);
Ralf Baechle90efba32014-04-25 03:19:57 +020081 return ieee754dp_indef();
Linus Torvalds1da177e2005-04-16 15:20:36 -070082
83 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_ZERO):
84 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO):
Ralf Baechle9e8bad12014-04-19 00:36:32 +020085 ieee754_setcx(IEEE754_ZERO_DIVIDE);
Ralf Baechle90efba32014-04-25 03:19:57 +020086 return ieee754dp_inf(xs ^ ys);
Linus Torvalds1da177e2005-04-16 15:20:36 -070087
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;
Liangliang Huangc9b02992020-05-04 16:51:29 +080094 fallthrough;
Linus Torvalds1da177e2005-04-16 15:20:36 -070095 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
Ralf Baechle3f7cac42014-04-26 01:49:14 +0200113 /* now the dirty work */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700114
Ralf Baechle3f7cac42014-04-26 01:49:14 +0200115 rm = 0;
116 re = xe - ye;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700117
Ralf Baechle3f7cac42014-04-26 01:49:14 +0200118 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;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700124 }
Ralf Baechle3f7cac42014-04-26 01:49:14 +0200125 xm <<= 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700126 }
Ralf Baechle3f7cac42014-04-26 01:49:14 +0200127
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);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700143}