Merge branch 'upstream' of git://ftp.linux-mips.org/pub/scm/upstream-linus
[linux-2.6] / arch / mips / math-emu / ieee754dp.c
1 /* IEEE754 floating point arithmetic
2  * double precision: common utilities
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 "ieee754dp.h"
29
30 int ieee754dp_class(ieee754dp x)
31 {
32         COMPXDP;
33         EXPLODEXDP;
34         return xc;
35 }
36
37 int ieee754dp_isnan(ieee754dp x)
38 {
39         return ieee754dp_class(x) >= IEEE754_CLASS_SNAN;
40 }
41
42 int ieee754dp_issnan(ieee754dp x)
43 {
44         assert(ieee754dp_isnan(x));
45         return ((DPMANT(x) & DP_MBIT(DP_MBITS-1)) == DP_MBIT(DP_MBITS-1));
46 }
47
48
49 ieee754dp ieee754dp_xcpt(ieee754dp r, const char *op, ...)
50 {
51         struct ieee754xctx ax;
52         if (!TSTX())
53                 return r;
54
55         ax.op = op;
56         ax.rt = IEEE754_RT_DP;
57         ax.rv.dp = r;
58         va_start(ax.ap, op);
59         ieee754_xcpt(&ax);
60         va_end(ax.ap);
61         return ax.rv.dp;
62 }
63
64 ieee754dp ieee754dp_nanxcpt(ieee754dp r, const char *op, ...)
65 {
66         struct ieee754xctx ax;
67
68         assert(ieee754dp_isnan(r));
69
70         if (!ieee754dp_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                 DPMANT(r) &= (~DP_MBIT(DP_MBITS-1));
76                 if (ieee754dp_isnan(r))
77                         return r;
78                 else
79                         return ieee754dp_indef();
80         }
81
82         ax.op = op;
83         ax.rt = 0;
84         ax.rv.dp = r;
85         va_start(ax.ap, op);
86         ieee754_xcpt(&ax);
87         va_end(ax.ap);
88         return ax.rv.dp;
89 }
90
91 ieee754dp ieee754dp_bestnan(ieee754dp x, ieee754dp y)
92 {
93         assert(ieee754dp_isnan(x));
94         assert(ieee754dp_isnan(y));
95
96         if (DPMANT(x) > DPMANT(y))
97                 return x;
98         else
99                 return y;
100 }
101
102
103 static u64 get_rounding(int sn, u64 xm)
104 {
105         /* inexact must round of 3 bits
106          */
107         if (xm & (DP_MBIT(3) - 1)) {
108                 switch (ieee754_csr.rm) {
109                 case IEEE754_RZ:
110                         break;
111                 case IEEE754_RN:
112                         xm += 0x3 + ((xm >> 3) & 1);
113                         /* xm += (xm&0x8)?0x4:0x3 */
114                         break;
115                 case IEEE754_RU:        /* toward +Infinity */
116                         if (!sn)        /* ?? */
117                                 xm += 0x8;
118                         break;
119                 case IEEE754_RD:        /* toward -Infinity */
120                         if (sn) /* ?? */
121                                 xm += 0x8;
122                         break;
123                 }
124         }
125         return xm;
126 }
127
128
129 /* generate a normal/denormal number with over,under handling
130  * sn is sign
131  * xe is an unbiased exponent
132  * xm is 3bit extended precision value.
133  */
134 ieee754dp ieee754dp_format(int sn, int xe, u64 xm)
135 {
136         assert(xm);             /* we don't gen exact zeros (probably should) */
137
138         assert((xm >> (DP_MBITS + 1 + 3)) == 0);        /* no execess */
139         assert(xm & (DP_HIDDEN_BIT << 3));
140
141         if (xe < DP_EMIN) {
142                 /* strip lower bits */
143                 int es = DP_EMIN - xe;
144
145                 if (ieee754_csr.nod) {
146                         SETCX(IEEE754_UNDERFLOW);
147                         SETCX(IEEE754_INEXACT);
148
149                         switch(ieee754_csr.rm) {
150                         case IEEE754_RN:
151                                 return ieee754dp_zero(sn);
152                         case IEEE754_RZ:
153                                 return ieee754dp_zero(sn);
154                         case IEEE754_RU:    /* toward +Infinity */
155                                 if(sn == 0)
156                                         return ieee754dp_min(0);
157                                 else
158                                         return ieee754dp_zero(1);
159                         case IEEE754_RD:    /* toward -Infinity */
160                                 if(sn == 0)
161                                         return ieee754dp_zero(0);
162                                 else
163                                         return ieee754dp_min(1);
164                         }
165                 }
166
167                 if (xe == DP_EMIN - 1
168                                 && get_rounding(sn, xm) >> (DP_MBITS + 1 + 3))
169                 {
170                         /* Not tiny after rounding */
171                         SETCX(IEEE754_INEXACT);
172                         xm = get_rounding(sn, xm);
173                         xm >>= 1;
174                         /* Clear grs bits */
175                         xm &= ~(DP_MBIT(3) - 1);
176                         xe++;
177                 }
178                 else {
179                         /* sticky right shift es bits
180                          */
181                         xm = XDPSRS(xm, es);
182                         xe += es;
183                         assert((xm & (DP_HIDDEN_BIT << 3)) == 0);
184                         assert(xe == DP_EMIN);
185                 }
186         }
187         if (xm & (DP_MBIT(3) - 1)) {
188                 SETCX(IEEE754_INEXACT);
189                 if ((xm & (DP_HIDDEN_BIT << 3)) == 0) {
190                         SETCX(IEEE754_UNDERFLOW);
191                 }
192
193                 /* inexact must round of 3 bits
194                  */
195                 xm = get_rounding(sn, xm);
196                 /* adjust exponent for rounding add overflowing
197                  */
198                 if (xm >> (DP_MBITS + 3 + 1)) {
199                         /* add causes mantissa overflow */
200                         xm >>= 1;
201                         xe++;
202                 }
203         }
204         /* strip grs bits */
205         xm >>= 3;
206
207         assert((xm >> (DP_MBITS + 1)) == 0);    /* no execess */
208         assert(xe >= DP_EMIN);
209
210         if (xe > DP_EMAX) {
211                 SETCX(IEEE754_OVERFLOW);
212                 SETCX(IEEE754_INEXACT);
213                 /* -O can be table indexed by (rm,sn) */
214                 switch (ieee754_csr.rm) {
215                 case IEEE754_RN:
216                         return ieee754dp_inf(sn);
217                 case IEEE754_RZ:
218                         return ieee754dp_max(sn);
219                 case IEEE754_RU:        /* toward +Infinity */
220                         if (sn == 0)
221                                 return ieee754dp_inf(0);
222                         else
223                                 return ieee754dp_max(1);
224                 case IEEE754_RD:        /* toward -Infinity */
225                         if (sn == 0)
226                                 return ieee754dp_max(0);
227                         else
228                                 return ieee754dp_inf(1);
229                 }
230         }
231         /* gen norm/denorm/zero */
232
233         if ((xm & DP_HIDDEN_BIT) == 0) {
234                 /* we underflow (tiny/zero) */
235                 assert(xe == DP_EMIN);
236                 if (ieee754_csr.mx & IEEE754_UNDERFLOW)
237                         SETCX(IEEE754_UNDERFLOW);
238                 return builddp(sn, DP_EMIN - 1 + DP_EBIAS, xm);
239         } else {
240                 assert((xm >> (DP_MBITS + 1)) == 0);    /* no execess */
241                 assert(xm & DP_HIDDEN_BIT);
242
243                 return builddp(sn, xe + DP_EBIAS, xm & ~DP_HIDDEN_BIT);
244         }
245 }