1 /* IEEE754 floating point arithmetic
2 * double precision: common utilities
5 * MIPS floating point support
6 * Copyright (C) 1994-2000 Algorithmics Ltd.
8 * This program is free software; you can distribute it and/or modify it
9 * under the terms of the GNU General Public License (Version 2) as
10 * published by the Free Software Foundation.
12 * This program is distributed in the hope it will be useful, but WITHOUT
13 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
14 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
17 * You should have received a copy of the GNU General Public License along
18 * with this program; if not, write to the Free Software Foundation, Inc.,
19 * 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
22 #include "ieee754dp.h"
24 union ieee754dp ieee754dp_sub(union ieee754dp x, union ieee754dp y)
39 switch (CLPAIR(xc, yc)) {
40 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_SNAN):
41 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_SNAN):
42 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_SNAN):
43 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_SNAN):
44 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_SNAN):
45 return ieee754dp_nanxcpt(y);
47 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_SNAN):
48 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_QNAN):
49 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_ZERO):
50 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_NORM):
51 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_DNORM):
52 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_INF):
53 return ieee754dp_nanxcpt(x);
55 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_QNAN):
56 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_QNAN):
57 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_QNAN):
58 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_QNAN):
61 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_QNAN):
62 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_ZERO):
63 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_NORM):
64 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_DNORM):
65 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_INF):
72 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_INF):
75 ieee754_setcx(IEEE754_INVALID_OPERATION);
76 return ieee754dp_indef();
78 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_INF):
79 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_INF):
80 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_INF):
81 return ieee754dp_inf(ys ^ 1);
83 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_ZERO):
84 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_NORM):
85 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_DNORM):
91 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO):
95 return ieee754dp_zero(ieee754_csr.rm == FPU_CSR_RD);
97 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_ZERO):
98 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO):
101 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_NORM):
102 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_DNORM):
107 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
111 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM):
112 /* normalize ym,ye */
116 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM):
117 /* normalize xm,xe */
121 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM):
124 /* flip sign of y and handle as add */
127 assert(xm & DP_HIDDEN_BIT);
128 assert(ym & DP_HIDDEN_BIT);
131 /* provide guard,round and stick bit dpace */
137 * Have to shift y fraction right to align
142 } else if (ye > xe) {
144 * Have to shift x fraction right to align
151 assert(xe <= DP_EMAX);
154 /* generate 28 bit result of adding two 27 bit numbers
158 if (xm >> (DP_FBITS + 1 + 3)) { /* carry out */
159 xm = XDPSRS1(xm); /* shift preserving sticky */
170 if (ieee754_csr.rm == FPU_CSR_RD)
171 return ieee754dp_zero(1); /* round negative inf. => sign = -1 */
173 return ieee754dp_zero(0); /* other round modes => sign = 1 */
176 /* normalize to rounding precision
178 while ((xm >> (DP_FBITS + 3)) == 0) {
184 return ieee754dp_format(xs, xe, xm);