File: /usr/src/linux/arch/mips/math-emu/dp_add.c
1 /* IEEE754 floating point arithmetic
2 * double precision: common utilities
3 */
4 /*
5 * MIPS floating point support
6 * Copyright (C) 1994-2000 Algorithmics Ltd. All rights reserved.
7 * http://www.algor.co.uk
8 *
9 * ########################################################################
10 *
11 * This program is free software; you can distribute it and/or modify it
12 * under the terms of the GNU General Public License (Version 2) as
13 * published by the Free Software Foundation.
14 *
15 * This program is distributed in the hope it will be useful, but WITHOUT
16 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
17 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
18 * for more details.
19 *
20 * You should have received a copy of the GNU General Public License along
21 * with this program; if not, write to the Free Software Foundation, Inc.,
22 * 59 Temple Place - Suite 330, Boston MA 02111-1307, USA.
23 *
24 * ########################################################################
25 *
26 */
27
28
29 #include "ieee754dp.h"
30
31 ieee754dp ieee754dp_add(ieee754dp x, ieee754dp y)
32 {
33 COMPXDP;
34 COMPYDP;
35
36 EXPLODEXDP;
37 EXPLODEYDP;
38
39 CLEARCX;
40
41 switch (CLPAIR(xc, yc)) {
42 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_SNAN):
43 return ieee754dp_nanxcpt(ieee754dp_bestnan(x, y), "add", x,
44 y);
45
46 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_SNAN):
47 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_SNAN):
48 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_SNAN):
49 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_SNAN):
50 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_SNAN):
51 return ieee754dp_nanxcpt(y, "add", x, y);
52
53 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_QNAN):
54 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_ZERO):
55 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_NORM):
56 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_DNORM):
57 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_INF):
58 return ieee754dp_nanxcpt(x, "add", x, y);
59
60 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_QNAN):
61 return ieee754dp_bestnan(x, y);
62
63 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_QNAN):
64 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_QNAN):
65 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_QNAN):
66 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_QNAN):
67 return y;
68
69 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_ZERO):
70 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_NORM):
71 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_DNORM):
72 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_INF):
73 return x;
74
75
76 /* Inifity handeling
77 */
78
79 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_INF):
80 if (xs == ys)
81 return x;
82 SETCX(IEEE754_INVALID_OPERATION);
83 return ieee754dp_xcpt(ieee754dp_indef(), "add", x, y);
84
85 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_INF):
86 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_INF):
87 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_INF):
88 return y;
89
90 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_ZERO):
91 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_NORM):
92 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_DNORM):
93 return x;
94
95 /* Zero handeling
96 */
97
98 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO):
99 if (xs == ys)
100 return x;
101 else
102 return ieee754dp_zero(ieee754_csr.rm ==
103 IEEE754_RD);
104
105 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_ZERO):
106 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO):
107 return x;
108
109 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_NORM):
110 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_DNORM):
111 return y;
112
113 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
114 DPDNORMX;
115
116 /* FALL THROUGH */
117
118 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM):
119 DPDNORMY;
120 break;
121
122 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM):
123 DPDNORMX;
124 break;
125
126 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM):
127 break;
128 }
129 assert(xm & DP_HIDDEN_BIT);
130 assert(ym & DP_HIDDEN_BIT);
131
132 /* provide guard,round and stick bit space */
133 xm <<= 3;
134 ym <<= 3;
135
136 if (xe > ye) {
137 /* have to shift y fraction right to align
138 */
139 int s = xe - ye;
140 ym = XDPSRS(ym, s);
141 ye += s;
142 } else if (ye > xe) {
143 /* have to shift x fraction right to align
144 */
145 int s = ye - xe;
146 xm = XDPSRS(xm, s);
147 xe += s;
148 }
149 assert(xe == ye);
150 assert(xe <= DP_EMAX);
151
152 if (xs == ys) {
153 /* generate 28 bit result of adding two 27 bit numbers
154 * leaving result in xm,xs,xe
155 */
156 xm = xm + ym;
157 xe = xe;
158 xs = xs;
159
160 if (xm >> (DP_MBITS + 1 + 3)) { /* carry out */
161 xm = XDPSRS1(xm);
162 xe++;
163 }
164 } else {
165 if (xm >= ym) {
166 xm = xm - ym;
167 xe = xe;
168 xs = xs;
169 } else {
170 xm = ym - xm;
171 xe = xe;
172 xs = ys;
173 }
174 if (xm == 0)
175 return ieee754dp_zero(ieee754_csr.rm ==
176 IEEE754_RD);
177
178 /* normalize to rounding precision */
179 while ((xm >> (DP_MBITS + 3)) == 0) {
180 xm <<= 1;
181 xe--;
182 }
183
184 }
185 DPNORMRET2(xs, xe, xm, "add", x, y);
186 }
187