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_SNAN, IEEE754_CLASS_QNAN):
41 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_SNAN):
42 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_SNAN):
43 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_SNAN):
44 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_SNAN):
45 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_SNAN):
46 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_SNAN):
47 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_ZERO):
48 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_NORM):
49 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_DNORM):
50 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_INF):
51 ieee754_setcx(IEEE754_INVALID_OPERATION);
52 return ieee754dp_nanxcpt(ieee754dp_indef());
54 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_QNAN):
55 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_QNAN):
56 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_QNAN):
57 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_QNAN):
60 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_QNAN):
61 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_ZERO):
62 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_NORM):
63 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_DNORM):
64 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_INF):
71 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_INF):
74 ieee754_setcx(IEEE754_INVALID_OPERATION);
75 return ieee754dp_indef();
77 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_INF):
78 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_INF):
79 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_INF):
80 return ieee754dp_inf(ys ^ 1);
82 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_ZERO):
83 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_NORM):
84 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_DNORM):
90 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO):
94 return ieee754dp_zero(ieee754_csr.rm == FPU_CSR_RD);
96 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_ZERO):
97 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO):
100 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_NORM):
101 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_DNORM):
106 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
110 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM):
111 /* normalize ym,ye */
115 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM):
116 /* normalize xm,xe */
120 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM):
123 /* flip sign of y and handle as add */
126 assert(xm & DP_HIDDEN_BIT);
127 assert(ym & DP_HIDDEN_BIT);
130 /* provide guard,round and stick bit dpace */
136 * Have to shift y fraction right to align
141 } else if (ye > xe) {
143 * Have to shift x fraction right to align
150 assert(xe <= DP_EMAX);
153 /* generate 28 bit result of adding two 27 bit numbers
159 if (xm >> (DP_FBITS + 1 + 3)) { /* carry out */
160 xm = XDPSRS1(xm); /* shift preserving sticky */
174 if (ieee754_csr.rm == FPU_CSR_RD)
175 return ieee754dp_zero(1); /* round negative inf. => sign = -1 */
177 return ieee754dp_zero(0); /* other round modes => sign = 1 */
180 /* normalize to rounding precision
182 while ((xm >> (DP_FBITS + 3)) == 0) {
188 return ieee754dp_format(xs, xe, xm);