[MIPS] Kconfig: Move missplaced NR_CPUS default from SMTC to VSMP.
[linux-2.6] / arch / mips / math-emu / ieee754sp.c
1 /* IEEE754 floating point arithmetic
2  * single precision
3  */
4 /*
5  * MIPS floating point support
6  * Copyright (C) 1994-2000 Algorithmics Ltd.
7  * http://www.algor.co.uk
8  *
9  * ########################################################################
10  *
11  *  This program is free software; you can distribute it and/or modify it
12  *  under the terms of the GNU General Public License (Version 2) as
13  *  published by the Free Software Foundation.
14  *
15  *  This program is distributed in the hope it will be useful, but WITHOUT
16  *  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
17  *  FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
18  *  for more details.
19  *
20  *  You should have received a copy of the GNU General Public License along
21  *  with this program; if not, write to the Free Software Foundation, Inc.,
22  *  59 Temple Place - Suite 330, Boston MA 02111-1307, USA.
23  *
24  * ########################################################################
25  */
26
27
28 #include "ieee754sp.h"
29
30 int ieee754sp_class(ieee754sp x)
31 {
32         COMPXSP;
33         EXPLODEXSP;
34         return xc;
35 }
36
37 int ieee754sp_isnan(ieee754sp x)
38 {
39         return ieee754sp_class(x) >= IEEE754_CLASS_SNAN;
40 }
41
42 int ieee754sp_issnan(ieee754sp x)
43 {
44         assert(ieee754sp_isnan(x));
45         return (SPMANT(x) & SP_MBIT(SP_MBITS-1));
46 }
47
48
49 ieee754sp ieee754sp_xcpt(ieee754sp r, const char *op, ...)
50 {
51         struct ieee754xctx ax;
52
53         if (!TSTX())
54                 return r;
55
56         ax.op = op;
57         ax.rt = IEEE754_RT_SP;
58         ax.rv.sp = r;
59         va_start(ax.ap, op);
60         ieee754_xcpt(&ax);
61         return ax.rv.sp;
62 }
63
64 ieee754sp ieee754sp_nanxcpt(ieee754sp r, const char *op, ...)
65 {
66         struct ieee754xctx ax;
67
68         assert(ieee754sp_isnan(r));
69
70         if (!ieee754sp_issnan(r))       /* QNAN does not cause invalid op !! */
71                 return r;
72
73         if (!SETANDTESTCX(IEEE754_INVALID_OPERATION)) {
74                 /* not enabled convert to a quiet NaN */
75                 SPMANT(r) &= (~SP_MBIT(SP_MBITS-1));
76                 if (ieee754sp_isnan(r))
77                         return r;
78                 else
79                         return ieee754sp_indef();
80         }
81
82         ax.op = op;
83         ax.rt = 0;
84         ax.rv.sp = r;
85         va_start(ax.ap, op);
86         ieee754_xcpt(&ax);
87         return ax.rv.sp;
88 }
89
90 ieee754sp ieee754sp_bestnan(ieee754sp x, ieee754sp y)
91 {
92         assert(ieee754sp_isnan(x));
93         assert(ieee754sp_isnan(y));
94
95         if (SPMANT(x) > SPMANT(y))
96                 return x;
97         else
98                 return y;
99 }
100
101
102 static unsigned get_rounding(int sn, unsigned xm)
103 {
104         /* inexact must round of 3 bits
105          */
106         if (xm & (SP_MBIT(3) - 1)) {
107                 switch (ieee754_csr.rm) {
108                 case IEEE754_RZ:
109                         break;
110                 case IEEE754_RN:
111                         xm += 0x3 + ((xm >> 3) & 1);
112                         /* xm += (xm&0x8)?0x4:0x3 */
113                         break;
114                 case IEEE754_RU:        /* toward +Infinity */
115                         if (!sn)        /* ?? */
116                                 xm += 0x8;
117                         break;
118                 case IEEE754_RD:        /* toward -Infinity */
119                         if (sn) /* ?? */
120                                 xm += 0x8;
121                         break;
122                 }
123         }
124         return xm;
125 }
126
127
128 /* generate a normal/denormal number with over,under handling
129  * sn is sign
130  * xe is an unbiased exponent
131  * xm is 3bit extended precision value.
132  */
133 ieee754sp ieee754sp_format(int sn, int xe, unsigned xm)
134 {
135         assert(xm);             /* we don't gen exact zeros (probably should) */
136
137         assert((xm >> (SP_MBITS + 1 + 3)) == 0);        /* no execess */
138         assert(xm & (SP_HIDDEN_BIT << 3));
139
140         if (xe < SP_EMIN) {
141                 /* strip lower bits */
142                 int es = SP_EMIN - xe;
143
144                 if (ieee754_csr.nod) {
145                         SETCX(IEEE754_UNDERFLOW);
146                         SETCX(IEEE754_INEXACT);
147
148                         switch(ieee754_csr.rm) {
149                         case IEEE754_RN:
150                                 return ieee754sp_zero(sn);
151                         case IEEE754_RZ:
152                                 return ieee754sp_zero(sn);
153                         case IEEE754_RU:      /* toward +Infinity */
154                                 if(sn == 0)
155                                         return ieee754sp_min(0);
156                                 else
157                                         return ieee754sp_zero(1);
158                         case IEEE754_RD:      /* toward -Infinity */
159                                 if(sn == 0)
160                                         return ieee754sp_zero(0);
161                                 else
162                                         return ieee754sp_min(1);
163                         }
164                 }
165
166                 if (xe == SP_EMIN - 1
167                                 && get_rounding(sn, xm) >> (SP_MBITS + 1 + 3))
168                 {
169                         /* Not tiny after rounding */
170                         SETCX(IEEE754_INEXACT);
171                         xm = get_rounding(sn, xm);
172                         xm >>= 1;
173                         /* Clear grs bits */
174                         xm &= ~(SP_MBIT(3) - 1);
175                         xe++;
176                 }
177                 else {
178                         /* sticky right shift es bits
179                          */
180                         SPXSRSXn(es);
181                         assert((xm & (SP_HIDDEN_BIT << 3)) == 0);
182                         assert(xe == SP_EMIN);
183                 }
184         }
185         if (xm & (SP_MBIT(3) - 1)) {
186                 SETCX(IEEE754_INEXACT);
187                 if ((xm & (SP_HIDDEN_BIT << 3)) == 0) {
188                         SETCX(IEEE754_UNDERFLOW);
189                 }
190
191                 /* inexact must round of 3 bits
192                  */
193                 xm = get_rounding(sn, xm);
194                 /* adjust exponent for rounding add overflowing
195                  */
196                 if (xm >> (SP_MBITS + 1 + 3)) {
197                         /* add causes mantissa overflow */
198                         xm >>= 1;
199                         xe++;
200                 }
201         }
202         /* strip grs bits */
203         xm >>= 3;
204
205         assert((xm >> (SP_MBITS + 1)) == 0);    /* no execess */
206         assert(xe >= SP_EMIN);
207
208         if (xe > SP_EMAX) {
209                 SETCX(IEEE754_OVERFLOW);
210                 SETCX(IEEE754_INEXACT);
211                 /* -O can be table indexed by (rm,sn) */
212                 switch (ieee754_csr.rm) {
213                 case IEEE754_RN:
214                         return ieee754sp_inf(sn);
215                 case IEEE754_RZ:
216                         return ieee754sp_max(sn);
217                 case IEEE754_RU:        /* toward +Infinity */
218                         if (sn == 0)
219                                 return ieee754sp_inf(0);
220                         else
221                                 return ieee754sp_max(1);
222                 case IEEE754_RD:        /* toward -Infinity */
223                         if (sn == 0)
224                                 return ieee754sp_max(0);
225                         else
226                                 return ieee754sp_inf(1);
227                 }
228         }
229         /* gen norm/denorm/zero */
230
231         if ((xm & SP_HIDDEN_BIT) == 0) {
232                 /* we underflow (tiny/zero) */
233                 assert(xe == SP_EMIN);
234                 if (ieee754_csr.mx & IEEE754_UNDERFLOW)
235                         SETCX(IEEE754_UNDERFLOW);
236                 return buildsp(sn, SP_EMIN - 1 + SP_EBIAS, xm);
237         } else {
238                 assert((xm >> (SP_MBITS + 1)) == 0);    /* no execess */
239                 assert(xm & SP_HIDDEN_BIT);
240
241                 return buildsp(sn, xe + SP_EBIAS, xm & ~SP_HIDDEN_BIT);
242         }
243 }