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
ieee754dp_add(union ieee754dp x,union ieee754dp y)24 union ieee754dp ieee754dp_add(union ieee754dp x, union ieee754dp y)
25 {
26 int s;
27
28 COMPXDP;
29 COMPYDP;
30
31 EXPLODEXDP;
32 EXPLODEYDP;
33
34 ieee754_clearcx();
35
36 FLUSHXDP;
37 FLUSHYDP;
38
39 switch (CLPAIR(xc, yc)) {
40 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_SNAN):
41 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_SNAN):
42 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_SNAN):
43 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_SNAN):
44 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_SNAN):
45 return ieee754dp_nanxcpt(y);
46
47 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_SNAN):
48 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_QNAN):
49 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_ZERO):
50 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_NORM):
51 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_DNORM):
52 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_INF):
53 return ieee754dp_nanxcpt(x);
54
55 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_QNAN):
56 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_QNAN):
57 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_QNAN):
58 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_QNAN):
59 return y;
60
61 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_QNAN):
62 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_ZERO):
63 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_NORM):
64 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_DNORM):
65 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_INF):
66 return x;
67
68
69 /*
70 * Infinity handling
71 */
72 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_INF):
73 if (xs == ys)
74 return x;
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 y;
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 x;
87
88 /*
89 * Zero handling
90 */
91 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO):
92 if (xs == ys)
93 return x;
94 else
95 return ieee754dp_zero(ieee754_csr.rm == FPU_CSR_RD);
96
97 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_ZERO):
98 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO):
99 return x;
100
101 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_NORM):
102 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_DNORM):
103 return y;
104
105 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
106 DPDNORMX;
107 /* fall through */
108
109 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM):
110 DPDNORMY;
111 break;
112
113 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM):
114 DPDNORMX;
115 break;
116
117 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM):
118 break;
119 }
120 assert(xm & DP_HIDDEN_BIT);
121 assert(ym & DP_HIDDEN_BIT);
122
123 /*
124 * Provide guard,round and stick bit space.
125 */
126 xm <<= 3;
127 ym <<= 3;
128
129 if (xe > ye) {
130 /*
131 * Have to shift y fraction right to align.
132 */
133 s = xe - ye;
134 ym = XDPSRS(ym, s);
135 ye += s;
136 } else if (ye > xe) {
137 /*
138 * Have to shift x fraction right to align.
139 */
140 s = ye - xe;
141 xm = XDPSRS(xm, s);
142 xe += s;
143 }
144 assert(xe == ye);
145 assert(xe <= DP_EMAX);
146
147 if (xs == ys) {
148 /*
149 * Generate 28 bit result of adding two 27 bit numbers
150 * leaving result in xm, xs and xe.
151 */
152 xm = xm + ym;
153
154 if (xm >> (DP_FBITS + 1 + 3)) { /* carry out */
155 xm = XDPSRS1(xm);
156 xe++;
157 }
158 } else {
159 if (xm >= ym) {
160 xm = xm - ym;
161 } else {
162 xm = ym - xm;
163 xs = ys;
164 }
165 if (xm == 0)
166 return ieee754dp_zero(ieee754_csr.rm == FPU_CSR_RD);
167
168 /*
169 * Normalize to rounding precision.
170 */
171 while ((xm >> (DP_FBITS + 3)) == 0) {
172 xm <<= 1;
173 xe--;
174 }
175 }
176
177 return ieee754dp_format(xs, xe, xm);
178 }
179