File: /usr/src/linux/arch/mips/math-emu/sp_add.c
1 /* IEEE754 floating point arithmetic
2 * single precision
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 #include "ieee754sp.h"
29
30 ieee754sp ieee754sp_add(ieee754sp x, ieee754sp y)
31 {
32 COMPXSP;
33 COMPYSP;
34
35 EXPLODEXSP;
36 EXPLODEYSP;
37
38 CLEARCX;
39
40 switch (CLPAIR(xc, yc)) {
41 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_SNAN):
42 return ieee754sp_nanxcpt(ieee754sp_bestnan(x, y), "add", x,
43 y);
44
45 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_SNAN):
46 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_SNAN):
47 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_SNAN):
48 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_SNAN):
49 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_SNAN):
50 return ieee754sp_nanxcpt(y, "add", x, y);
51
52 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_QNAN):
53 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_ZERO):
54 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_NORM):
55 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_DNORM):
56 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_INF):
57 return ieee754sp_nanxcpt(x, "add", x, y);
58
59 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_QNAN):
60 return ieee754sp_bestnan(x, y);
61
62 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_QNAN):
63 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_QNAN):
64 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_QNAN):
65 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_QNAN):
66 return y;
67
68 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_ZERO):
69 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_NORM):
70 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_DNORM):
71 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_INF):
72 return x;
73
74
75 /* Inifity handeling
76 */
77
78 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_INF):
79 if (xs == ys)
80 return x;
81 SETCX(IEEE754_INVALID_OPERATION);
82 return ieee754sp_xcpt(ieee754sp_indef(), "add", x, y);
83
84 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_INF):
85 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_INF):
86 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_INF):
87 return y;
88
89 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_ZERO):
90 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_NORM):
91 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_DNORM):
92 return x;
93
94 /* Zero handeling
95 */
96
97 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO):
98 if (xs == ys)
99 return x;
100 else
101 return ieee754sp_zero(ieee754_csr.rm ==
102 IEEE754_RD);
103
104 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_ZERO):
105 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO):
106 return x;
107
108 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_NORM):
109 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_DNORM):
110 return y;
111
112 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
113 SPDNORMX;
114
115 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM):
116 SPDNORMY;
117 break;
118
119 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM):
120 SPDNORMX;
121 break;
122
123 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM):
124 break;
125 }
126 assert(xm & SP_HIDDEN_BIT);
127 assert(ym & SP_HIDDEN_BIT);
128
129 /* provide guard,round and stick bit space */
130 xm <<= 3;
131 ym <<= 3;
132
133 if (xe > ye) {
134 /* have to shift y fraction right to align
135 */
136 int s = xe - ye;
137 SPXSRSYn(s);
138 } else if (ye > xe) {
139 /* have to shift x fraction right to align
140 */
141 int s = ye - xe;
142 SPXSRSXn(s);
143 }
144 assert(xe == ye);
145 assert(xe <= SP_EMAX);
146
147 if (xs == ys) {
148 /* generate 28 bit result of adding two 27 bit numbers
149 * leaving result in xm,xs,xe
150 */
151 xm = xm + ym;
152 xe = xe;
153 xs = xs;
154
155 if (xm >> (SP_MBITS + 1 + 3)) { /* carry out */
156 SPXSRSX1();
157 }
158 } else {
159 if (xm >= ym) {
160 xm = xm - ym;
161 xe = xe;
162 xs = xs;
163 } else {
164 xm = ym - xm;
165 xe = xe;
166 xs = ys;
167 }
168 if (xm == 0)
169 return ieee754sp_zero(ieee754_csr.rm ==
170 IEEE754_RD);
171
172 /* normalize in extended single precision */
173 while ((xm >> (SP_MBITS + 3)) == 0) {
174 xm <<= 1;
175 xe--;
176 }
177
178 }
179 SPNORMRET2(xs, xe, xm, "add", x, y);
180 }
181