Merge branch 'irq-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git...
[linux-2.6] / 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.
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         FLUSHXDP;
42         FLUSHYDP;
43
44         switch (CLPAIR(xc, yc)) {
45         case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_QNAN):
46         case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_SNAN):
47         case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_SNAN):
48         case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_SNAN):
49         case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_SNAN):
50         case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_SNAN):
51         case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_SNAN):
52         case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_ZERO):
53         case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_NORM):
54         case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_DNORM):
55         case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_INF):
56                 SETCX(IEEE754_INVALID_OPERATION);
57                 return ieee754dp_nanxcpt(ieee754dp_indef(), "add", x, y);
58
59         case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_QNAN):
60         case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_QNAN):
61         case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_QNAN):
62         case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_QNAN):
63                 return y;
64
65         case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_QNAN):
66         case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_ZERO):
67         case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_NORM):
68         case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_DNORM):
69         case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_INF):
70                 return x;
71
72
73                 /* Infinity handling
74                  */
75
76         case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_INF):
77                 if (xs == ys)
78                         return x;
79                 SETCX(IEEE754_INVALID_OPERATION);
80                 return ieee754dp_xcpt(ieee754dp_indef(), "add", x, y);
81
82         case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_INF):
83         case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_INF):
84         case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_INF):
85                 return y;
86
87         case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_ZERO):
88         case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_NORM):
89         case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_DNORM):
90                 return x;
91
92                 /* Zero handling
93                  */
94
95         case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO):
96                 if (xs == ys)
97                         return x;
98                 else
99                         return ieee754dp_zero(ieee754_csr.rm ==
100                                               IEEE754_RD);
101
102         case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_ZERO):
103         case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO):
104                 return x;
105
106         case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_NORM):
107         case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_DNORM):
108                 return y;
109
110         case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
111                 DPDNORMX;
112
113                 /* FALL THROUGH */
114
115         case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM):
116                 DPDNORMY;
117                 break;
118
119         case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM):
120                 DPDNORMX;
121                 break;
122
123         case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM):
124                 break;
125         }
126         assert(xm & DP_HIDDEN_BIT);
127         assert(ym & DP_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                 ym = XDPSRS(ym, s);
138                 ye += s;
139         } else if (ye > xe) {
140                 /* have to shift x fraction right to align
141                  */
142                 int s = ye - xe;
143                 xm = XDPSRS(xm, s);
144                 xe += s;
145         }
146         assert(xe == ye);
147         assert(xe <= DP_EMAX);
148
149         if (xs == ys) {
150                 /* generate 28 bit result of adding two 27 bit numbers
151                  * leaving result in xm,xs,xe
152                  */
153                 xm = xm + ym;
154                 xe = xe;
155                 xs = xs;
156
157                 if (xm >> (DP_MBITS + 1 + 3)) { /* carry out */
158                         xm = XDPSRS1(xm);
159                         xe++;
160                 }
161         } else {
162                 if (xm >= ym) {
163                         xm = xm - ym;
164                         xe = xe;
165                         xs = xs;
166                 } else {
167                         xm = ym - xm;
168                         xe = xe;
169                         xs = ys;
170                 }
171                 if (xm == 0)
172                         return ieee754dp_zero(ieee754_csr.rm ==
173                                               IEEE754_RD);
174
175                 /* normalize to rounding precision */
176                 while ((xm >> (DP_MBITS + 3)) == 0) {
177                         xm <<= 1;
178                         xe--;
179                 }
180
181         }
182         DPNORMRET2(xs, xe, xm, "add", x, y);
183 }