blob: 8592e49032b876d9e4eb1921e9385b05814e5e19 [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/* IEEE754 floating point arithmetic
2 * single precision
3 */
4/*
5 * MIPS floating point support
6 * Copyright (C) 1994-2000 Algorithmics Ltd.
Linus Torvalds1da177e2005-04-16 15:20:36 -07007 *
Linus Torvalds1da177e2005-04-16 15:20:36 -07008 * 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.,
Ralf Baechle3f7cac42014-04-26 01:49:14 +020019 * 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
Linus Torvalds1da177e2005-04-16 15:20:36 -070020 */
21
Linus Torvalds1da177e2005-04-16 15:20:36 -070022#include "ieee754sp.h"
23
Ralf Baechle2209bcb2014-04-16 01:31:11 +020024union ieee754sp ieee754sp_sub(union ieee754sp x, union ieee754sp y)
Linus Torvalds1da177e2005-04-16 15:20:36 -070025{
Ralf Baechle3f7cac42014-04-26 01:49:14 +020026 int s;
27
Linus Torvalds1da177e2005-04-16 15:20:36 -070028 COMPXSP;
29 COMPYSP;
30
31 EXPLODEXSP;
32 EXPLODEYSP;
33
Ralf Baechle9e8bad12014-04-19 00:36:32 +020034 ieee754_clearcx();
Linus Torvalds1da177e2005-04-16 15:20:36 -070035
36 FLUSHXSP;
37 FLUSHYSP;
38
39 switch (CLPAIR(xc, yc)) {
40 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_QNAN):
41 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_SNAN):
42 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_SNAN):
43 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_SNAN):
44 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_SNAN):
45 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_SNAN):
46 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_SNAN):
47 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_ZERO):
48 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_NORM):
49 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_DNORM):
50 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_INF):
Ralf Baechle9e8bad12014-04-19 00:36:32 +020051 ieee754_setcx(IEEE754_INVALID_OPERATION);
Ralf Baechle90efba32014-04-25 03:19:57 +020052 return ieee754sp_nanxcpt(ieee754sp_indef());
Linus Torvalds1da177e2005-04-16 15:20:36 -070053
54 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_QNAN):
55 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_QNAN):
56 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_QNAN):
57 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_QNAN):
58 return y;
59
60 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_QNAN):
61 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_ZERO):
62 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_NORM):
63 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_DNORM):
64 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_INF):
65 return x;
66
67
Ralf Baechle3f7cac42014-04-26 01:49:14 +020068 /*
69 * Infinity handling
70 */
Linus Torvalds1da177e2005-04-16 15:20:36 -070071 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_INF):
72 if (xs != ys)
73 return x;
Ralf Baechle9e8bad12014-04-19 00:36:32 +020074 ieee754_setcx(IEEE754_INVALID_OPERATION);
Ralf Baechle90efba32014-04-25 03:19:57 +020075 return ieee754sp_indef();
Linus Torvalds1da177e2005-04-16 15:20:36 -070076
77 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_INF):
78 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_INF):
79 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_INF):
80 return ieee754sp_inf(ys ^ 1);
81
82 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_ZERO):
83 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_NORM):
84 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_DNORM):
85 return x;
86
Ralf Baechle3f7cac42014-04-26 01:49:14 +020087 /*
88 * Zero handling
89 */
Linus Torvalds1da177e2005-04-16 15:20:36 -070090 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO):
91 if (xs != ys)
92 return x;
93 else
Ralf Baechle56a64732014-04-30 11:21:55 +020094 return ieee754sp_zero(ieee754_csr.rm == FPU_CSR_RD);
Linus Torvalds1da177e2005-04-16 15:20:36 -070095
96 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_ZERO):
97 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO):
98 return x;
99
100 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_NORM):
101 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_DNORM):
102 /* quick fix up */
Ralf Baechle3e160aa2014-04-22 16:02:03 +0200103 SPSIGN(y) ^= 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700104 return y;
105
106 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
107 SPDNORMX;
108
109 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM):
110 SPDNORMY;
111 break;
112
113 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM):
114 SPDNORMX;
115 break;
116
117 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM):
118 break;
119 }
120 /* flip sign of y and handle as add */
121 ys ^= 1;
122
123 assert(xm & SP_HIDDEN_BIT);
124 assert(ym & SP_HIDDEN_BIT);
125
126
127 /* provide guard,round and stick bit space */
128 xm <<= 3;
129 ym <<= 3;
130
131 if (xe > ye) {
Ralf Baechle3f7cac42014-04-26 01:49:14 +0200132 /*
133 * have to shift y fraction right to align
Linus Torvalds1da177e2005-04-16 15:20:36 -0700134 */
Ralf Baechle3f7cac42014-04-26 01:49:14 +0200135 s = xe - ye;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700136 SPXSRSYn(s);
137 } else if (ye > xe) {
Ralf Baechle3f7cac42014-04-26 01:49:14 +0200138 /*
139 * have to shift x fraction right to align
Linus Torvalds1da177e2005-04-16 15:20:36 -0700140 */
Ralf Baechle3f7cac42014-04-26 01:49:14 +0200141 s = ye - xe;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700142 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 */
150 xm = xm + ym;
151 xe = xe;
152 xs = xs;
153
Ralf Baechlead8fb5532014-04-22 15:51:55 +0200154 if (xm >> (SP_FBITS + 1 + 3)) { /* carry out */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700155 SPXSRSX1(); /* shift preserving sticky */
156 }
157 } else {
158 if (xm >= ym) {
159 xm = xm - ym;
160 xe = xe;
161 xs = xs;
162 } else {
163 xm = ym - xm;
164 xe = xe;
165 xs = ys;
166 }
167 if (xm == 0) {
Ralf Baechle56a64732014-04-30 11:21:55 +0200168 if (ieee754_csr.rm == FPU_CSR_RD)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700169 return ieee754sp_zero(1); /* round negative inf. => sign = -1 */
170 else
171 return ieee754sp_zero(0); /* other round modes => sign = 1 */
172 }
173 /* normalize to rounding precision
174 */
Ralf Baechlead8fb5532014-04-22 15:51:55 +0200175 while ((xm >> (SP_FBITS + 3)) == 0) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700176 xm <<= 1;
177 xe--;
178 }
179 }
Ralf Baechle90efba32014-04-25 03:19:57 +0200180
181 return ieee754sp_format(xs, xe, xm);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700182}