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1da177e4 LT |
1 | /* IEEE754 floating point arithmetic |
2 | * single precision | |
3 | */ | |
4 | /* | |
5 | * MIPS floating point support | |
6 | * Copyright (C) 1994-2000 Algorithmics Ltd. | |
1da177e4 LT |
7 | * |
8 | * ######################################################################## | |
9 | * | |
10 | * This program is free software; you can distribute it and/or modify it | |
11 | * under the terms of the GNU General Public License (Version 2) as | |
12 | * published by the Free Software Foundation. | |
13 | * | |
14 | * This program is distributed in the hope it will be useful, but WITHOUT | |
15 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | |
16 | * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | |
17 | * for more details. | |
18 | * | |
19 | * You should have received a copy of the GNU General Public License along | |
20 | * with this program; if not, write to the Free Software Foundation, Inc., | |
21 | * 59 Temple Place - Suite 330, Boston MA 02111-1307, USA. | |
22 | * | |
23 | * ######################################################################## | |
24 | */ | |
25 | ||
26 | ||
27 | #include "ieee754sp.h" | |
28 | ||
29 | int ieee754sp_class(ieee754sp x) | |
30 | { | |
31 | COMPXSP; | |
32 | EXPLODEXSP; | |
33 | return xc; | |
34 | } | |
35 | ||
36 | int ieee754sp_isnan(ieee754sp x) | |
37 | { | |
38 | return ieee754sp_class(x) >= IEEE754_CLASS_SNAN; | |
39 | } | |
40 | ||
41 | int ieee754sp_issnan(ieee754sp x) | |
42 | { | |
43 | assert(ieee754sp_isnan(x)); | |
44 | return (SPMANT(x) & SP_MBIT(SP_MBITS-1)); | |
45 | } | |
46 | ||
47 | ||
48 | ieee754sp ieee754sp_xcpt(ieee754sp r, const char *op, ...) | |
49 | { | |
50 | struct ieee754xctx ax; | |
51 | ||
52 | if (!TSTX()) | |
53 | return r; | |
54 | ||
55 | ax.op = op; | |
56 | ax.rt = IEEE754_RT_SP; | |
57 | ax.rv.sp = r; | |
58 | va_start(ax.ap, op); | |
59 | ieee754_xcpt(&ax); | |
8142294d | 60 | va_end(ax.ap); |
1da177e4 LT |
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); | |
8142294d | 87 | va_end(ax.ap); |
1da177e4 LT |
88 | return ax.rv.sp; |
89 | } | |
90 | ||
91 | ieee754sp ieee754sp_bestnan(ieee754sp x, ieee754sp y) | |
92 | { | |
93 | assert(ieee754sp_isnan(x)); | |
94 | assert(ieee754sp_isnan(y)); | |
95 | ||
96 | if (SPMANT(x) > SPMANT(y)) | |
97 | return x; | |
98 | else | |
99 | return y; | |
100 | } | |
101 | ||
102 | ||
103 | static unsigned get_rounding(int sn, unsigned xm) | |
104 | { | |
105 | /* inexact must round of 3 bits | |
106 | */ | |
107 | if (xm & (SP_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 */ | |
70342287 | 120 | if (sn) /* ?? */ |
1da177e4 LT |
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 | ieee754sp ieee754sp_format(int sn, int xe, unsigned xm) | |
135 | { | |
136 | assert(xm); /* we don't gen exact zeros (probably should) */ | |
137 | ||
138 | assert((xm >> (SP_MBITS + 1 + 3)) == 0); /* no execess */ | |
139 | assert(xm & (SP_HIDDEN_BIT << 3)); | |
140 | ||
141 | if (xe < SP_EMIN) { | |
142 | /* strip lower bits */ | |
143 | int es = SP_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: | |
1da177e4 LT |
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 | } |