File: /usr/src/linux/arch/mips/math-emu/sp_mul.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_mul(ieee754sp x, ieee754sp y)
31 {
32 COMPXSP;
33 COMPYSP;
34
35 CLEARCX;
36
37 EXPLODEXSP;
38 EXPLODEYSP;
39
40 switch (CLPAIR(xc, yc)) {
41 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_SNAN):
42 return ieee754sp_nanxcpt(ieee754sp_bestnan(x, y), "mul", 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, "mul", 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, "mul", 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 /* Infinity handeling */
76
77 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_ZERO):
78 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_INF):
79 SETCX(IEEE754_INVALID_OPERATION);
80 return ieee754sp_xcpt(ieee754sp_indef(), "mul", x, y);
81
82 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_INF):
83 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_INF):
84 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_NORM):
85 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_DNORM):
86 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_INF):
87 return ieee754sp_inf(xs ^ ys);
88
89 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO):
90 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_NORM):
91 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_DNORM):
92 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_ZERO):
93 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO):
94 return ieee754sp_zero(xs ^ ys);
95
96
97 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
98 SPDNORMX;
99
100 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM):
101 SPDNORMY;
102 break;
103
104 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM):
105 SPDNORMX;
106 break;
107
108 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM):
109 break;
110 }
111 /* rm = xm * ym, re = xe+ye basicly */
112 assert(xm & SP_HIDDEN_BIT);
113 assert(ym & SP_HIDDEN_BIT);
114
115 {
116 int re = xe + ye;
117 int rs = xs ^ ys;
118 unsigned rm;
119
120 /* shunt to top of word */
121 xm <<= 32 - (SP_MBITS + 1);
122 ym <<= 32 - (SP_MBITS + 1);
123
124 /* multiply 32bits xm,ym to give high 32bits rm with stickness
125 */
126 {
127 unsigned short lxm = xm & 0xffff;
128 unsigned short hxm = xm >> 16;
129 unsigned short lym = ym & 0xffff;
130 unsigned short hym = ym >> 16;
131 unsigned lrm;
132 unsigned hrm;
133
134 lrm = lxm * lym; /* 16 * 16 => 32 */
135 hrm = hxm * hym; /* 16 * 16 => 32 */
136
137 {
138 unsigned t = lxm * hym; /* 16 * 16 => 32 */
139 {
140 unsigned at = lrm + (t << 16);
141 hrm += at < lrm;
142 lrm = at;
143 }
144 hrm = hrm + (t >> 16);
145 }
146
147 {
148 unsigned t = hxm * lym; /* 16 * 16 => 32 */
149 {
150 unsigned at = lrm + (t << 16);
151 hrm += at < lrm;
152 lrm = at;
153 }
154 hrm = hrm + (t >> 16);
155 }
156 rm = hrm | (lrm != 0);
157 }
158
159 /*
160 * sticky shift down to normal rounding precision
161 */
162 if ((int) rm < 0) {
163 rm = (rm >> (32 - (SP_MBITS + 1 + 3))) |
164 ((rm << (SP_MBITS + 1 + 3)) != 0);
165 re++;
166 } else {
167 rm = (rm >> (32 - (SP_MBITS + 1 + 3 + 1))) |
168 ((rm << (SP_MBITS + 1 + 3 + 1)) != 0);
169 }
170 assert(rm & (SP_HIDDEN_BIT << 3));
171
172 SPNORMRET2(rs, re, rm, "mul", x, y);
173 }
174 }
175