1 // SPDX-License-Identifier: GPL-2.0-only
2 /* IEEE754 floating point arithmetic
3 * double precision: common utilities
4 */
5 /*
6 * MIPS floating point support
7 * Copyright (C) 1994-2000 Algorithmics Ltd.
8 */
9
10 #include "ieee754dp.h"
11
12 union ieee754dp ieee754dp_add(union ieee754dp x, union ieee754dp y)
13 {
14 int s;
15
16 COMPXDP;
17 COMPYDP;
18
19 EXPLODEXDP;
20 EXPLODEYDP;
21
22 ieee754_clearcx();
23
24 FLUSHXDP;
25 FLUSHYDP;
26
27 switch (CLPAIR(xc, yc)) {
28 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_SNAN):
29 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_SNAN):
30 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_SNAN):
31 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_SNAN):
32 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_SNAN):
33 return ieee754dp_nanxcpt(y);
34
35 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_SNAN):
36 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_QNAN):
37 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_ZERO):
38 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_NORM):
39 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_DNORM):
40 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_INF):
41 return ieee754dp_nanxcpt(x);
42
43 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_QNAN):
44 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_QNAN):
45 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_QNAN):
46 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_QNAN):
47 return y;
48
49 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_QNAN):
50 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_ZERO):
51 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_NORM):
52 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_DNORM):
53 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_INF):
54 return x;
55
56
57 /*
58 * Infinity handling
59 */
60 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_INF):
61 if (xs == ys)
62 return x;
63 ieee754_setcx(IEEE754_INVALID_OPERATION);
64 return ieee754dp_indef();
65
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 y;
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 x;
75
76 /*
77 * Zero handling
78 */
79 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO):
80 if (xs == ys)
81 return x;
82 else
83 return ieee754dp_zero(ieee754_csr.rm == FPU_CSR_RD);
84
85 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_ZERO):
86 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO):
87 return x;
88
89 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_NORM):
90 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_DNORM):
91 return y;
92
93 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
94 DPDNORMX;
95 fallthrough;
96 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM):
97 DPDNORMY;
98 break;
99
100 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM):
101 DPDNORMX;
102 break;
103
104 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM):
105 break;
106 }
107 assert(xm & DP_HIDDEN_BIT);
108 assert(ym & DP_HIDDEN_BIT);
109
110 /*
111 * Provide guard,round and stick bit space.
112 */
113 xm <<= 3;
114 ym <<= 3;
115
116 if (xe > ye) {
117 /*
118 * Have to shift y fraction right to align.
119 */
120 s = xe - ye;
121 ym = XDPSRS(ym, s);
122 ye += s;
123 } else if (ye > xe) {
124 /*
125 * Have to shift x fraction right to align.
126 */
127 s = ye - xe;
128 xm = XDPSRS(xm, s);
129 xe += s;
130 }
131 assert(xe == ye);
132 assert(xe <= DP_EMAX);
133
134 if (xs == ys) {
135 /*
136 * Generate 28 bit result of adding two 27 bit numbers
137 * leaving result in xm, xs and xe.
138 */
139 xm = xm + ym;
140
141 if (xm >> (DP_FBITS + 1 + 3)) { /* carry out */
142 xm = XDPSRS1(xm);
143 xe++;
144 }
145 } else {
146 if (xm >= ym) {
147 xm = xm - ym;
148 } else {
149 xm = ym - xm;
150 xs = ys;
151 }
152 if (xm == 0)
153 return ieee754dp_zero(ieee754_csr.rm == FPU_CSR_RD);
154
155 /*
156 * Normalize to rounding precision.
157 */
158 while ((xm >> (DP_FBITS + 3)) == 0) {
159 xm <<= 1;
160 xe--;
161 }
162 }
163
164 return ieee754dp_format(xs, xe, xm);
165 }
166
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