Commit | Line | Data |
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1da177e4 LT |
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 | ||
29 | #include "ieee754dp.h" | |
30 | ||
31 | ieee754dp ieee754dp_add(ieee754dp x, ieee754dp y) | |
32 | { | |
33 | COMPXDP; | |
34 | COMPYDP; | |
35 | ||
36 | EXPLODEXDP; | |
37 | EXPLODEYDP; | |
38 | ||
39 | CLEARCX; | |
40 | ||
41 | FLUSHXDP; | |
42 | FLUSHYDP; | |
43 | ||
44 | switch (CLPAIR(xc, yc)) { | |
45 | case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_QNAN): | |
46 | case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_SNAN): | |
47 | case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_SNAN): | |
48 | case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_SNAN): | |
49 | case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_SNAN): | |
50 | case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_SNAN): | |
51 | case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_SNAN): | |
52 | case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_ZERO): | |
53 | case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_NORM): | |
54 | case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_DNORM): | |
55 | case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_INF): | |
56 | SETCX(IEEE754_INVALID_OPERATION); | |
57 | return ieee754dp_nanxcpt(ieee754dp_indef(), "add", x, y); | |
58 | ||
59 | case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_QNAN): | |
60 | case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_QNAN): | |
61 | case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_QNAN): | |
62 | case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_QNAN): | |
63 | return y; | |
64 | ||
65 | case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_QNAN): | |
66 | case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_ZERO): | |
67 | case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_NORM): | |
68 | case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_DNORM): | |
69 | case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_INF): | |
70 | return x; | |
71 | ||
72 | ||
73 | /* Infinity handling | |
74 | */ | |
75 | ||
76 | case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_INF): | |
77 | if (xs == ys) | |
78 | return x; | |
79 | SETCX(IEEE754_INVALID_OPERATION); | |
80 | return ieee754dp_xcpt(ieee754dp_indef(), "add", x, y); | |
81 | ||
82 | case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_INF): | |
83 | case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_INF): | |
84 | case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_INF): | |
85 | return y; | |
86 | ||
87 | case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_ZERO): | |
88 | case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_NORM): | |
89 | case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_DNORM): | |
90 | return x; | |
91 | ||
92 | /* Zero handling | |
93 | */ | |
94 | ||
95 | case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO): | |
96 | if (xs == ys) | |
97 | return x; | |
98 | else | |
99 | return ieee754dp_zero(ieee754_csr.rm == | |
100 | IEEE754_RD); | |
101 | ||
102 | case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_ZERO): | |
103 | case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO): | |
104 | return x; | |
105 | ||
106 | case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_NORM): | |
107 | case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_DNORM): | |
108 | return y; | |
109 | ||
110 | case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM): | |
111 | DPDNORMX; | |
112 | ||
113 | /* FALL THROUGH */ | |
114 | ||
115 | case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM): | |
116 | DPDNORMY; | |
117 | break; | |
118 | ||
119 | case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM): | |
120 | DPDNORMX; | |
121 | break; | |
122 | ||
123 | case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM): | |
124 | break; | |
125 | } | |
126 | assert(xm & DP_HIDDEN_BIT); | |
127 | assert(ym & DP_HIDDEN_BIT); | |
128 | ||
129 | /* provide guard,round and stick bit space */ | |
130 | xm <<= 3; | |
131 | ym <<= 3; | |
132 | ||
133 | if (xe > ye) { | |
134 | /* have to shift y fraction right to align | |
135 | */ | |
136 | int s = xe - ye; | |
137 | ym = XDPSRS(ym, s); | |
138 | ye += s; | |
139 | } else if (ye > xe) { | |
140 | /* have to shift x fraction right to align | |
141 | */ | |
142 | int s = ye - xe; | |
143 | xm = XDPSRS(xm, s); | |
144 | xe += s; | |
145 | } | |
146 | assert(xe == ye); | |
147 | assert(xe <= DP_EMAX); | |
148 | ||
149 | if (xs == ys) { | |
150 | /* generate 28 bit result of adding two 27 bit numbers | |
151 | * leaving result in xm,xs,xe | |
152 | */ | |
153 | xm = xm + ym; | |
154 | xe = xe; | |
155 | xs = xs; | |
156 | ||
157 | if (xm >> (DP_MBITS + 1 + 3)) { /* carry out */ | |
158 | xm = XDPSRS1(xm); | |
159 | xe++; | |
160 | } | |
161 | } else { | |
162 | if (xm >= ym) { | |
163 | xm = xm - ym; | |
164 | xe = xe; | |
165 | xs = xs; | |
166 | } else { | |
167 | xm = ym - xm; | |
168 | xe = xe; | |
169 | xs = ys; | |
170 | } | |
171 | if (xm == 0) | |
172 | return ieee754dp_zero(ieee754_csr.rm == | |
173 | IEEE754_RD); | |
174 | ||
175 | /* normalize to rounding precision */ | |
176 | while ((xm >> (DP_MBITS + 3)) == 0) { | |
177 | xm <<= 1; | |
178 | xe--; | |
179 | } | |
180 | ||
181 | } | |
182 | DPNORMRET2(xs, xe, xm, "add", x, y); | |
183 | } |