Linux Kernel  3.7.1
 All Data Structures Namespaces Files Functions Variables Typedefs Enumerations Enumerator Macros Groups Pages
sp_mul.c
Go to the documentation of this file.
1 /* IEEE754 floating point arithmetic
2  * single precision
3  */
4 /*
5  * MIPS floating point support
6  * Copyright (C) 1994-2000 Algorithmics Ltd.
7  *
8  * ########################################################################
9  *
10  * This program is free software; you can distribute it and/or modify it
11  * under the terms of the GNU General Public License (Version 2) as
12  * published by the Free Software Foundation.
13  *
14  * This program is distributed in the hope it will be useful, but WITHOUT
15  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
16  * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
17  * for more details.
18  *
19  * You should have received a copy of the GNU General Public License along
20  * with this program; if not, write to the Free Software Foundation, Inc.,
21  * 59 Temple Place - Suite 330, Boston MA 02111-1307, USA.
22  *
23  * ########################################################################
24  */
25 
26 
27 #include "ieee754sp.h"
28 
29 ieee754sp ieee754sp_mul(ieee754sp x, ieee754sp y)
30 {
31  COMPXSP;
32  COMPYSP;
33 
34  EXPLODEXSP;
35  EXPLODEYSP;
36 
37  CLEARCX;
38 
39  FLUSHXSP;
40  FLUSHYSP;
41 
42  switch (CLPAIR(xc, yc)) {
43  case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_QNAN):
44  case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_SNAN):
45  case CLPAIR(IEEE754_CLASS_SNAN, 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  case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_ZERO):
51  case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_NORM):
52  case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_DNORM):
53  case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_INF):
54  SETCX(IEEE754_INVALID_OPERATION);
55  return ieee754sp_nanxcpt(ieee754sp_indef(), "mul", x, y);
56 
57  case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_QNAN):
58  case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_QNAN):
59  case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_QNAN):
60  case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_QNAN):
61  return y;
62 
63  case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_QNAN):
64  case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_ZERO):
65  case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_NORM):
66  case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_DNORM):
67  case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_INF):
68  return x;
69 
70 
71  /* Infinity handling */
72 
73  case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_ZERO):
74  case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_INF):
75  SETCX(IEEE754_INVALID_OPERATION);
76  return ieee754sp_xcpt(ieee754sp_indef(), "mul", x, y);
77 
78  case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_INF):
79  case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_INF):
80  case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_NORM):
81  case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_DNORM):
82  case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_INF):
83  return ieee754sp_inf(xs ^ ys);
84 
85  case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO):
86  case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_NORM):
87  case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_DNORM):
88  case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_ZERO):
89  case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO):
90  return ieee754sp_zero(xs ^ ys);
91 
92 
93  case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
94  SPDNORMX;
95 
96  case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM):
97  SPDNORMY;
98  break;
99 
100  case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM):
101  SPDNORMX;
102  break;
103 
104  case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM):
105  break;
106  }
107  /* rm = xm * ym, re = xe+ye basically */
108  assert(xm & SP_HIDDEN_BIT);
109  assert(ym & SP_HIDDEN_BIT);
110 
111  {
112  int re = xe + ye;
113  int rs = xs ^ ys;
114  unsigned rm;
115 
116  /* shunt to top of word */
117  xm <<= 32 - (SP_MBITS + 1);
118  ym <<= 32 - (SP_MBITS + 1);
119 
120  /* multiply 32bits xm,ym to give high 32bits rm with stickness
121  */
122  {
123  unsigned short lxm = xm & 0xffff;
124  unsigned short hxm = xm >> 16;
125  unsigned short lym = ym & 0xffff;
126  unsigned short hym = ym >> 16;
127  unsigned lrm;
128  unsigned hrm;
129 
130  lrm = lxm * lym; /* 16 * 16 => 32 */
131  hrm = hxm * hym; /* 16 * 16 => 32 */
132 
133  {
134  unsigned t = lxm * hym; /* 16 * 16 => 32 */
135  {
136  unsigned at = lrm + (t << 16);
137  hrm += at < lrm;
138  lrm = at;
139  }
140  hrm = hrm + (t >> 16);
141  }
142 
143  {
144  unsigned t = hxm * lym; /* 16 * 16 => 32 */
145  {
146  unsigned at = lrm + (t << 16);
147  hrm += at < lrm;
148  lrm = at;
149  }
150  hrm = hrm + (t >> 16);
151  }
152  rm = hrm | (lrm != 0);
153  }
154 
155  /*
156  * sticky shift down to normal rounding precision
157  */
158  if ((int) rm < 0) {
159  rm = (rm >> (32 - (SP_MBITS + 1 + 3))) |
160  ((rm << (SP_MBITS + 1 + 3)) != 0);
161  re++;
162  } else {
163  rm = (rm >> (32 - (SP_MBITS + 1 + 3 + 1))) |
164  ((rm << (SP_MBITS + 1 + 3 + 1)) != 0);
165  }
166  assert(rm & (SP_HIDDEN_BIT << 3));
167 
168  SPNORMRET2(rs, re, rm, "mul", x, y);
169  }
170 }
Generated on Thu Jan 10 2013 13:11:40 for Linux Kernel by   doxygen 1.8.2