1 /* IEEE754 floating point arithmetic
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 "ieee754sp.h"
26 int ieee754sp_class(union ieee754sp x)
33 int ieee754sp_isnan(union ieee754sp x)
35 return ieee754sp_class(x) >= IEEE754_CLASS_SNAN;
38 static inline int ieee754sp_issnan(union ieee754sp x)
40 assert(ieee754sp_isnan(x));
41 return (SPMANT(x) & SP_MBIT(SP_FBITS-1));
45 union ieee754sp __cold ieee754sp_nanxcpt(union ieee754sp r)
47 assert(ieee754sp_isnan(r));
49 if (!ieee754sp_issnan(r)) /* QNAN does not cause invalid op !! */
52 if (!ieee754_setandtestcx(IEEE754_INVALID_OPERATION)) {
53 /* not enabled convert to a quiet NaN */
54 SPMANT(r) &= (~SP_MBIT(SP_FBITS-1));
55 if (ieee754sp_isnan(r))
58 return ieee754sp_indef();
64 static unsigned ieee754sp_get_rounding(int sn, unsigned xm)
66 /* inexact must round of 3 bits
68 if (xm & (SP_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 ieee754sp ieee754sp_format(int sn, int xe, unsigned xm)
97 assert(xm); /* we don't gen exact zeros (probably should) */
99 assert((xm >> (SP_FBITS + 1 + 3)) == 0); /* no execess */
100 assert(xm & (SP_HIDDEN_BIT << 3));
103 /* strip lower bits */
104 int es = SP_EMIN - xe;
106 if (ieee754_csr.nod) {
107 ieee754_setcx(IEEE754_UNDERFLOW);
108 ieee754_setcx(IEEE754_INEXACT);
110 switch(ieee754_csr.rm) {
113 return ieee754sp_zero(sn);
114 case FPU_CSR_RU: /* toward +Infinity */
116 return ieee754sp_min(0);
118 return ieee754sp_zero(1);
119 case FPU_CSR_RD: /* toward -Infinity */
121 return ieee754sp_zero(0);
123 return ieee754sp_min(1);
127 if (xe == SP_EMIN - 1 &&
128 ieee754sp_get_rounding(sn, xm) >> (SP_FBITS + 1 + 3))
130 /* Not tiny after rounding */
131 ieee754_setcx(IEEE754_INEXACT);
132 xm = ieee754sp_get_rounding(sn, xm);
135 xm &= ~(SP_MBIT(3) - 1);
138 /* sticky right shift es bits
141 assert((xm & (SP_HIDDEN_BIT << 3)) == 0);
142 assert(xe == SP_EMIN);
145 if (xm & (SP_MBIT(3) - 1)) {
146 ieee754_setcx(IEEE754_INEXACT);
147 if ((xm & (SP_HIDDEN_BIT << 3)) == 0) {
148 ieee754_setcx(IEEE754_UNDERFLOW);
151 /* inexact must round of 3 bits
153 xm = ieee754sp_get_rounding(sn, xm);
154 /* adjust exponent for rounding add overflowing
156 if (xm >> (SP_FBITS + 1 + 3)) {
157 /* add causes mantissa overflow */
165 assert((xm >> (SP_FBITS + 1)) == 0); /* no execess */
166 assert(xe >= SP_EMIN);
169 ieee754_setcx(IEEE754_OVERFLOW);
170 ieee754_setcx(IEEE754_INEXACT);
171 /* -O can be table indexed by (rm,sn) */
172 switch (ieee754_csr.rm) {
174 return ieee754sp_inf(sn);
176 return ieee754sp_max(sn);
177 case FPU_CSR_RU: /* toward +Infinity */
179 return ieee754sp_inf(0);
181 return ieee754sp_max(1);
182 case FPU_CSR_RD: /* toward -Infinity */
184 return ieee754sp_max(0);
186 return ieee754sp_inf(1);
189 /* gen norm/denorm/zero */
191 if ((xm & SP_HIDDEN_BIT) == 0) {
192 /* we underflow (tiny/zero) */
193 assert(xe == SP_EMIN);
194 if (ieee754_csr.mx & IEEE754_UNDERFLOW)
195 ieee754_setcx(IEEE754_UNDERFLOW);
196 return buildsp(sn, SP_EMIN - 1 + SP_EBIAS, xm);
198 assert((xm >> (SP_FBITS + 1)) == 0); /* no execess */
199 assert(xm & SP_HIDDEN_BIT);
201 return buildsp(sn, xe + SP_EBIAS, xm & ~SP_HIDDEN_BIT);