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 <linux/compiler.h>
24 #include "ieee754dp.h"
26 int ieee754dp_class(union ieee754dp x)
33 int ieee754dp_isnan(union ieee754dp x)
35 return ieee754dp_class(x) >= IEEE754_CLASS_SNAN;
38 static inline int ieee754dp_issnan(union ieee754dp x)
40 assert(ieee754dp_isnan(x));
41 return ((DPMANT(x) & DP_MBIT(DP_FBITS-1)) == DP_MBIT(DP_FBITS-1));
45 union ieee754dp __cold ieee754dp_nanxcpt(union ieee754dp r)
47 assert(ieee754dp_isnan(r));
49 if (!ieee754dp_issnan(r)) /* QNAN does not cause invalid op !! */
52 if (!ieee754_setandtestcx(IEEE754_INVALID_OPERATION)) {
53 /* not enabled convert to a quiet NaN */
54 DPMANT(r) &= (~DP_MBIT(DP_FBITS-1));
55 if (ieee754dp_isnan(r))
58 return ieee754dp_indef();
64 static u64 ieee754dp_get_rounding(int sn, u64 xm)
66 /* inexact must round of 3 bits
68 if (xm & (DP_MBIT(3) - 1)) {
69 switch (ieee754_csr.rm) {
73 xm += 0x3 + ((xm >> 3) & 1);
74 /* xm += (xm&0x8)?0x4:0x3 */
76 case FPU_CSR_RU: /* toward +Infinity */
80 case FPU_CSR_RD: /* toward -Infinity */
90 /* generate a normal/denormal number with over,under handling
92 * xe is an unbiased exponent
93 * xm is 3bit extended precision value.
95 union ieee754dp ieee754dp_format(int sn, int xe, u64 xm)
97 assert(xm); /* we don't gen exact zeros (probably should) */
99 assert((xm >> (DP_FBITS + 1 + 3)) == 0); /* no execess */
100 assert(xm & (DP_HIDDEN_BIT << 3));
103 /* strip lower bits */
104 int es = DP_EMIN - xe;
106 if (ieee754_csr.nod) {
107 ieee754_setcx(IEEE754_UNDERFLOW);
108 ieee754_setcx(IEEE754_INEXACT);
110 switch(ieee754_csr.rm) {
113 return ieee754dp_zero(sn);
114 case FPU_CSR_RU: /* toward +Infinity */
116 return ieee754dp_min(0);
118 return ieee754dp_zero(1);
119 case FPU_CSR_RD: /* toward -Infinity */
121 return ieee754dp_zero(0);
123 return ieee754dp_min(1);
127 if (xe == DP_EMIN - 1 &&
128 ieee754dp_get_rounding(sn, xm) >> (DP_FBITS + 1 + 3))
130 /* Not tiny after rounding */
131 ieee754_setcx(IEEE754_INEXACT);
132 xm = ieee754dp_get_rounding(sn, xm);
135 xm &= ~(DP_MBIT(3) - 1);
139 /* sticky right shift es bits
143 assert((xm & (DP_HIDDEN_BIT << 3)) == 0);
144 assert(xe == DP_EMIN);
147 if (xm & (DP_MBIT(3) - 1)) {
148 ieee754_setcx(IEEE754_INEXACT);
149 if ((xm & (DP_HIDDEN_BIT << 3)) == 0) {
150 ieee754_setcx(IEEE754_UNDERFLOW);
153 /* inexact must round of 3 bits
155 xm = ieee754dp_get_rounding(sn, xm);
156 /* adjust exponent for rounding add overflowing
158 if (xm >> (DP_FBITS + 3 + 1)) {
159 /* add causes mantissa overflow */
167 assert((xm >> (DP_FBITS + 1)) == 0); /* no execess */
168 assert(xe >= DP_EMIN);
171 ieee754_setcx(IEEE754_OVERFLOW);
172 ieee754_setcx(IEEE754_INEXACT);
173 /* -O can be table indexed by (rm,sn) */
174 switch (ieee754_csr.rm) {
176 return ieee754dp_inf(sn);
178 return ieee754dp_max(sn);
179 case FPU_CSR_RU: /* toward +Infinity */
181 return ieee754dp_inf(0);
183 return ieee754dp_max(1);
184 case FPU_CSR_RD: /* toward -Infinity */
186 return ieee754dp_max(0);
188 return ieee754dp_inf(1);
191 /* gen norm/denorm/zero */
193 if ((xm & DP_HIDDEN_BIT) == 0) {
194 /* we underflow (tiny/zero) */
195 assert(xe == DP_EMIN);
196 if (ieee754_csr.mx & IEEE754_UNDERFLOW)
197 ieee754_setcx(IEEE754_UNDERFLOW);
198 return builddp(sn, DP_EMIN - 1 + DP_EBIAS, xm);
200 assert((xm >> (DP_FBITS + 1)) == 0); /* no execess */
201 assert(xm & DP_HIDDEN_BIT);
203 return builddp(sn, xe + DP_EBIAS, xm & ~DP_HIDDEN_BIT);