tree-wide: fix assorted typos all over the place
[linux-2.6.git] / arch / mips / math-emu / dp_sub.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 #include "ieee754dp.h"
29
30 ieee754dp ieee754dp_sub(ieee754dp x, ieee754dp y)
31 {
32         COMPXDP;
33         COMPYDP;
34
35         EXPLODEXDP;
36         EXPLODEYDP;
37
38         CLEARCX;
39
40         FLUSHXDP;
41         FLUSHYDP;
42
43         switch (CLPAIR(xc, yc)) {
44         case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_QNAN):
45         case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_SNAN):
46         case CLPAIR(IEEE754_CLASS_SNAN, 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         case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_ZERO):
52         case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_NORM):
53         case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_DNORM):
54         case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_INF):
55                 SETCX(IEEE754_INVALID_OPERATION);
56                 return ieee754dp_nanxcpt(ieee754dp_indef(), "sub", x, y);
57
58         case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_QNAN):
59         case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_QNAN):
60         case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_QNAN):
61         case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_QNAN):
62                 return y;
63
64         case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_QNAN):
65         case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_ZERO):
66         case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_NORM):
67         case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_DNORM):
68         case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_INF):
69                 return x;
70
71
72                 /* Infinity handling
73                  */
74
75         case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_INF):
76                 if (xs != ys)
77                         return x;
78                 SETCX(IEEE754_INVALID_OPERATION);
79                 return ieee754dp_xcpt(ieee754dp_indef(), "sub", x, y);
80
81         case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_INF):
82         case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_INF):
83         case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_INF):
84                 return ieee754dp_inf(ys ^ 1);
85
86         case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_ZERO):
87         case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_NORM):
88         case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_DNORM):
89                 return x;
90
91                 /* Zero handling
92                  */
93
94         case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO):
95                 if (xs != ys)
96                         return x;
97                 else
98                         return ieee754dp_zero(ieee754_csr.rm ==
99                                               IEEE754_RD);
100
101         case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_ZERO):
102         case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO):
103                 return x;
104
105         case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_NORM):
106         case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_DNORM):
107                 /* quick fix up */
108                 DPSIGN(y) ^= 1;
109                 return y;
110
111         case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
112                 DPDNORMX;
113                 /* FALL THROUGH */
114
115         case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM):
116                 /* normalize ym,ye */
117                 DPDNORMY;
118                 break;
119
120         case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM):
121                 /* normalize xm,xe */
122                 DPDNORMX;
123                 break;
124
125         case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM):
126                 break;
127         }
128         /* flip sign of y and handle as add */
129         ys ^= 1;
130
131         assert(xm & DP_HIDDEN_BIT);
132         assert(ym & DP_HIDDEN_BIT);
133
134
135         /* provide guard,round and stick bit dpace */
136         xm <<= 3;
137         ym <<= 3;
138
139         if (xe > ye) {
140                 /* have to shift y fraction right to align
141                  */
142                 int s = xe - ye;
143                 ym = XDPSRS(ym, s);
144                 ye += s;
145         } else if (ye > xe) {
146                 /* have to shift x fraction right to align
147                  */
148                 int s = ye - xe;
149                 xm = XDPSRS(xm, s);
150                 xe += s;
151         }
152         assert(xe == ye);
153         assert(xe <= DP_EMAX);
154
155         if (xs == ys) {
156                 /* generate 28 bit result of adding two 27 bit numbers
157                  */
158                 xm = xm + ym;
159                 xe = xe;
160                 xs = xs;
161
162                 if (xm >> (DP_MBITS + 1 + 3)) { /* carry out */
163                         xm = XDPSRS1(xm);       /* shift preserving sticky */
164                         xe++;
165                 }
166         } else {
167                 if (xm >= ym) {
168                         xm = xm - ym;
169                         xe = xe;
170                         xs = xs;
171                 } else {
172                         xm = ym - xm;
173                         xe = xe;
174                         xs = ys;
175                 }
176                 if (xm == 0) {
177                         if (ieee754_csr.rm == IEEE754_RD)
178                                 return ieee754dp_zero(1);       /* round negative inf. => sign = -1 */
179                         else
180                                 return ieee754dp_zero(0);       /* other round modes   => sign = 1 */
181                 }
182
183                 /* normalize to rounding precision
184                  */
185                 while ((xm >> (DP_MBITS + 3)) == 0) {
186                         xm <<= 1;
187                         xe--;
188                 }
189         }
190         DPNORMRET2(xs, xe, xm, "sub", x, y);
191 }