Linux Kernel  3.7.1
 All Data Structures Namespaces Files Functions Variables Typedefs Enumerations Enumerator Macros Groups Pages
dp_add.c
Go to the documentation of this file.
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  *
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 
28 #include "ieee754dp.h"
29 
30 ieee754dp ieee754dp_add(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(), "add", 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(), "add", x, y);
80 
81  case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_INF):
82  case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_INF):
83  case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_INF):
84  return y;
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  return y;
108 
109  case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
110  DPDNORMX;
111 
112  /* FALL THROUGH */
113 
114  case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM):
115  DPDNORMY;
116  break;
117 
118  case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM):
119  DPDNORMX;
120  break;
121 
122  case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM):
123  break;
124  }
125  assert(xm & DP_HIDDEN_BIT);
126  assert(ym & DP_HIDDEN_BIT);
127 
128  /* provide guard,round and stick bit space */
129  xm <<= 3;
130  ym <<= 3;
131 
132  if (xe > ye) {
133  /* have to shift y fraction right to align
134  */
135  int s = xe - ye;
136  ym = XDPSRS(ym, s);
137  ye += s;
138  } else if (ye > xe) {
139  /* have to shift x fraction right to align
140  */
141  int s = ye - xe;
142  xm = XDPSRS(xm, s);
143  xe += s;
144  }
145  assert(xe == ye);
146  assert(xe <= DP_EMAX);
147 
148  if (xs == ys) {
149  /* generate 28 bit result of adding two 27 bit numbers
150  * leaving result in xm,xs,xe
151  */
152  xm = xm + ym;
153  xe = xe;
154  xs = xs;
155 
156  if (xm >> (DP_MBITS + 1 + 3)) { /* carry out */
157  xm = XDPSRS1(xm);
158  xe++;
159  }
160  } else {
161  if (xm >= ym) {
162  xm = xm - ym;
163  xe = xe;
164  xs = xs;
165  } else {
166  xm = ym - xm;
167  xe = xe;
168  xs = ys;
169  }
170  if (xm == 0)
171  return ieee754dp_zero(ieee754_csr.rm ==
172  IEEE754_RD);
173 
174  /* normalize to rounding precision */
175  while ((xm >> (DP_MBITS + 3)) == 0) {
176  xm <<= 1;
177  xe--;
178  }
179 
180  }
181  DPNORMRET2(xs, xe, xm, "add", x, y);
182 }
Generated on Thu Jan 10 2013 13:11:38 for Linux Kernel by   doxygen 1.8.2