1
2
3
4
5
6
7
8
9
10#include "ieee754dp.h"
11
12union ieee754dp ieee754dp_sub(union ieee754dp x, union ieee754dp y)
13{
14 int s;
15
16 COMPXDP;
17 COMPYDP;
18
19 EXPLODEXDP;
20 EXPLODEYDP;
21
22 ieee754_clearcx();
23
24 FLUSHXDP;
25 FLUSHYDP;
26
27 switch (CLPAIR(xc, yc)) {
28 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_SNAN):
29 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_SNAN):
30 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_SNAN):
31 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_SNAN):
32 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_SNAN):
33 return ieee754dp_nanxcpt(y);
34
35 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_SNAN):
36 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_QNAN):
37 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_ZERO):
38 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_NORM):
39 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_DNORM):
40 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_INF):
41 return ieee754dp_nanxcpt(x);
42
43 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_QNAN):
44 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_QNAN):
45 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_QNAN):
46 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_QNAN):
47 return y;
48
49 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_QNAN):
50 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_ZERO):
51 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_NORM):
52 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_DNORM):
53 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_INF):
54 return x;
55
56
57
58
59
60 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_INF):
61 if (xs != ys)
62 return x;
63 ieee754_setcx(IEEE754_INVALID_OPERATION);
64 return ieee754dp_indef();
65
66 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_INF):
67 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_INF):
68 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_INF):
69 return ieee754dp_inf(ys ^ 1);
70
71 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_ZERO):
72 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_NORM):
73 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_DNORM):
74 return x;
75
76
77
78
79 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO):
80 if (xs != ys)
81 return x;
82 else
83 return ieee754dp_zero(ieee754_csr.rm == FPU_CSR_RD);
84
85 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_ZERO):
86 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO):
87 return x;
88
89 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_NORM):
90 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_DNORM):
91
92 DPSIGN(y) ^= 1;
93 return y;
94
95 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
96 DPDNORMX;
97 fallthrough;
98 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM):
99
100 DPDNORMY;
101 break;
102
103 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM):
104
105 DPDNORMX;
106 break;
107
108 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM):
109 break;
110 }
111
112 ys ^= 1;
113
114 assert(xm & DP_HIDDEN_BIT);
115 assert(ym & DP_HIDDEN_BIT);
116
117
118
119 xm <<= 3;
120 ym <<= 3;
121
122 if (xe > ye) {
123
124
125
126 s = xe - ye;
127 ym = XDPSRS(ym, s);
128 ye += s;
129 } else if (ye > xe) {
130
131
132
133 s = ye - xe;
134 xm = XDPSRS(xm, s);
135 xe += s;
136 }
137 assert(xe == ye);
138 assert(xe <= DP_EMAX);
139
140 if (xs == ys) {
141
142
143 xm = xm + ym;
144
145 if (xm >> (DP_FBITS + 1 + 3)) {
146 xm = XDPSRS1(xm);
147 xe++;
148 }
149 } else {
150 if (xm >= ym) {
151 xm = xm - ym;
152 } else {
153 xm = ym - xm;
154 xs = ys;
155 }
156 if (xm == 0) {
157 if (ieee754_csr.rm == FPU_CSR_RD)
158 return ieee754dp_zero(1);
159 else
160 return ieee754dp_zero(0);
161 }
162
163
164
165 while ((xm >> (DP_FBITS + 3)) == 0) {
166 xm <<= 1;
167 xe--;
168 }
169 }
170
171 return ieee754dp_format(xs, xe, xm);
172}
173