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 static inline int ieee754dp_isnan(union ieee754dp x)
35 return ieee754_class_nan(ieee754dp_class(x));
38 static inline int ieee754dp_issnan(union ieee754dp x)
42 assert(ieee754dp_isnan(x));
43 qbit = (DPMANT(x) & DP_MBIT(DP_FBITS - 1)) == DP_MBIT(DP_FBITS - 1);
44 return ieee754_csr.nan2008 ^ qbit;
49 * Raise the Invalid Operation IEEE 754 exception
50 * and convert the signaling NaN supplied to a quiet NaN.
52 union ieee754dp __cold ieee754dp_nanxcpt(union ieee754dp r)
54 assert(ieee754dp_issnan(r));
56 ieee754_setcx(IEEE754_INVALID_OPERATION);
57 if (ieee754_csr.nan2008) {
58 DPMANT(r) |= DP_MBIT(DP_FBITS - 1);
60 DPMANT(r) &= ~DP_MBIT(DP_FBITS - 1);
61 if (!ieee754dp_isnan(r))
62 DPMANT(r) |= DP_MBIT(DP_FBITS - 2);
68 static u64 ieee754dp_get_rounding(int sn, u64 xm)
70 /* inexact must round of 3 bits
72 if (xm & (DP_MBIT(3) - 1)) {
73 switch (ieee754_csr.rm) {
77 xm += 0x3 + ((xm >> 3) & 1);
78 /* xm += (xm&0x8)?0x4:0x3 */
80 case FPU_CSR_RU: /* toward +Infinity */
84 case FPU_CSR_RD: /* toward -Infinity */
94 /* generate a normal/denormal number with over,under handling
96 * xe is an unbiased exponent
97 * xm is 3bit extended precision value.
99 union ieee754dp ieee754dp_format(int sn, int xe, u64 xm)
101 assert(xm); /* we don't gen exact zeros (probably should) */
103 assert((xm >> (DP_FBITS + 1 + 3)) == 0); /* no excess */
104 assert(xm & (DP_HIDDEN_BIT << 3));
107 /* strip lower bits */
108 int es = DP_EMIN - xe;
110 if (ieee754_csr.nod) {
111 ieee754_setcx(IEEE754_UNDERFLOW);
112 ieee754_setcx(IEEE754_INEXACT);
114 switch(ieee754_csr.rm) {
117 return ieee754dp_zero(sn);
118 case FPU_CSR_RU: /* toward +Infinity */
120 return ieee754dp_min(0);
122 return ieee754dp_zero(1);
123 case FPU_CSR_RD: /* toward -Infinity */
125 return ieee754dp_zero(0);
127 return ieee754dp_min(1);
131 if (xe == DP_EMIN - 1 &&
132 ieee754dp_get_rounding(sn, xm) >> (DP_FBITS + 1 + 3))
134 /* Not tiny after rounding */
135 ieee754_setcx(IEEE754_INEXACT);
136 xm = ieee754dp_get_rounding(sn, xm);
139 xm &= ~(DP_MBIT(3) - 1);
143 /* sticky right shift es bits
147 assert((xm & (DP_HIDDEN_BIT << 3)) == 0);
148 assert(xe == DP_EMIN);
151 if (xm & (DP_MBIT(3) - 1)) {
152 ieee754_setcx(IEEE754_INEXACT);
153 if ((xm & (DP_HIDDEN_BIT << 3)) == 0) {
154 ieee754_setcx(IEEE754_UNDERFLOW);
157 /* inexact must round of 3 bits
159 xm = ieee754dp_get_rounding(sn, xm);
160 /* adjust exponent for rounding add overflowing
162 if (xm >> (DP_FBITS + 3 + 1)) {
163 /* add causes mantissa overflow */
171 assert((xm >> (DP_FBITS + 1)) == 0); /* no excess */
172 assert(xe >= DP_EMIN);
175 ieee754_setcx(IEEE754_OVERFLOW);
176 ieee754_setcx(IEEE754_INEXACT);
177 /* -O can be table indexed by (rm,sn) */
178 switch (ieee754_csr.rm) {
180 return ieee754dp_inf(sn);
182 return ieee754dp_max(sn);
183 case FPU_CSR_RU: /* toward +Infinity */
185 return ieee754dp_inf(0);
187 return ieee754dp_max(1);
188 case FPU_CSR_RD: /* toward -Infinity */
190 return ieee754dp_max(0);
192 return ieee754dp_inf(1);
195 /* gen norm/denorm/zero */
197 if ((xm & DP_HIDDEN_BIT) == 0) {
198 /* we underflow (tiny/zero) */
199 assert(xe == DP_EMIN);
200 if (ieee754_csr.mx & IEEE754_UNDERFLOW)
201 ieee754_setcx(IEEE754_UNDERFLOW);
202 return builddp(sn, DP_EMIN - 1 + DP_EBIAS, xm);
204 assert((xm >> (DP_FBITS + 1)) == 0); /* no excess */
205 assert(xm & DP_HIDDEN_BIT);
207 return builddp(sn, xe + DP_EBIAS, xm & ~DP_HIDDEN_BIT);