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252b5132 | 1 | /* IEEE floating point support routines, for GDB, the GNU Debugger. |
08372f14 | 2 | Copyright (C) 1991, 1994, 1999 Free Software Foundation, Inc. |
252b5132 RH |
3 | |
4 | This file is part of GDB. | |
5 | ||
6 | This program is free software; you can redistribute it and/or modify | |
7 | it under the terms of the GNU General Public License as published by | |
8 | the Free Software Foundation; either version 2 of the License, or | |
9 | (at your option) any later version. | |
10 | ||
11 | This program is distributed in the hope that it will be useful, | |
12 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
13 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
14 | GNU General Public License for more details. | |
15 | ||
16 | You should have received a copy of the GNU General Public License | |
17 | along with this program; if not, write to the Free Software | |
18 | Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */ | |
19 | ||
20 | #include "floatformat.h" | |
21 | #include <math.h> /* ldexp */ | |
22 | #ifdef __STDC__ | |
23 | #include <stddef.h> | |
24 | extern void *memcpy (void *s1, const void *s2, size_t n); | |
25 | extern void *memset (void *s, int c, size_t n); | |
26 | #else | |
27 | extern char *memcpy (); | |
28 | extern char *memset (); | |
29 | #endif | |
30 | ||
31 | /* The odds that CHAR_BIT will be anything but 8 are low enough that I'm not | |
32 | going to bother with trying to muck around with whether it is defined in | |
33 | a system header, what we do if not, etc. */ | |
34 | #define FLOATFORMAT_CHAR_BIT 8 | |
35 | ||
36 | /* floatformats for IEEE single and double, big and little endian. */ | |
37 | const struct floatformat floatformat_ieee_single_big = | |
38 | { | |
39 | floatformat_big, 32, 0, 1, 8, 127, 255, 9, 23, floatformat_intbit_no | |
40 | }; | |
41 | const struct floatformat floatformat_ieee_single_little = | |
42 | { | |
43 | floatformat_little, 32, 0, 1, 8, 127, 255, 9, 23, floatformat_intbit_no | |
44 | }; | |
45 | const struct floatformat floatformat_ieee_double_big = | |
46 | { | |
47 | floatformat_big, 64, 0, 1, 11, 1023, 2047, 12, 52, floatformat_intbit_no | |
48 | }; | |
49 | const struct floatformat floatformat_ieee_double_little = | |
50 | { | |
51 | floatformat_little, 64, 0, 1, 11, 1023, 2047, 12, 52, floatformat_intbit_no | |
52 | }; | |
53 | ||
54 | /* floatformat for IEEE double, little endian byte order, with big endian word | |
55 | ordering, as on the ARM. */ | |
56 | ||
57 | const struct floatformat floatformat_ieee_double_littlebyte_bigword = | |
58 | { | |
59 | floatformat_littlebyte_bigword, 64, 0, 1, 11, 1023, 2047, 12, 52, floatformat_intbit_no | |
60 | }; | |
61 | ||
62 | const struct floatformat floatformat_i387_ext = | |
63 | { | |
64 | floatformat_little, 80, 0, 1, 15, 0x3fff, 0x7fff, 16, 64, | |
65 | floatformat_intbit_yes | |
66 | }; | |
67 | const struct floatformat floatformat_m68881_ext = | |
68 | { | |
69 | /* Note that the bits from 16 to 31 are unused. */ | |
70 | floatformat_big, 96, 0, 1, 15, 0x3fff, 0x7fff, 32, 64, floatformat_intbit_yes | |
71 | }; | |
72 | const struct floatformat floatformat_i960_ext = | |
73 | { | |
74 | /* Note that the bits from 0 to 15 are unused. */ | |
75 | floatformat_little, 96, 16, 17, 15, 0x3fff, 0x7fff, 32, 64, | |
76 | floatformat_intbit_yes | |
77 | }; | |
78 | const struct floatformat floatformat_m88110_ext = | |
79 | { | |
80 | #ifdef HARRIS_FLOAT_FORMAT | |
81 | /* Harris uses raw format 128 bytes long, but the number is just an ieee | |
82 | double, and the last 64 bits are wasted. */ | |
83 | floatformat_big,128, 0, 1, 11, 0x3ff, 0x7ff, 12, 52, | |
84 | floatformat_intbit_no | |
85 | #else | |
86 | floatformat_big, 80, 0, 1, 15, 0x3fff, 0x7fff, 16, 64, | |
87 | floatformat_intbit_yes | |
88 | #endif /* HARRIS_FLOAT_FORMAT */ | |
89 | }; | |
90 | const struct floatformat floatformat_arm_ext = | |
91 | { | |
92 | /* Bits 1 to 16 are unused. */ | |
93 | floatformat_big, 96, 0, 17, 15, 0x3fff, 0x7fff, 32, 64, | |
94 | floatformat_intbit_yes | |
95 | }; | |
96 | \f | |
97 | static unsigned long get_field PARAMS ((unsigned char *, | |
98 | enum floatformat_byteorders, | |
99 | unsigned int, | |
100 | unsigned int, | |
101 | unsigned int)); | |
102 | ||
103 | /* Extract a field which starts at START and is LEN bytes long. DATA and | |
104 | TOTAL_LEN are the thing we are extracting it from, in byteorder ORDER. */ | |
105 | static unsigned long | |
106 | get_field (data, order, total_len, start, len) | |
107 | unsigned char *data; | |
108 | enum floatformat_byteorders order; | |
109 | unsigned int total_len; | |
110 | unsigned int start; | |
111 | unsigned int len; | |
112 | { | |
113 | unsigned long result; | |
114 | unsigned int cur_byte; | |
115 | int cur_bitshift; | |
116 | ||
117 | /* Start at the least significant part of the field. */ | |
118 | cur_byte = (start + len) / FLOATFORMAT_CHAR_BIT; | |
119 | if (order == floatformat_little) | |
120 | cur_byte = (total_len / FLOATFORMAT_CHAR_BIT) - cur_byte - 1; | |
121 | cur_bitshift = | |
122 | ((start + len) % FLOATFORMAT_CHAR_BIT) - FLOATFORMAT_CHAR_BIT; | |
123 | result = *(data + cur_byte) >> (-cur_bitshift); | |
124 | cur_bitshift += FLOATFORMAT_CHAR_BIT; | |
125 | if (order == floatformat_little) | |
126 | ++cur_byte; | |
127 | else | |
128 | --cur_byte; | |
129 | ||
130 | /* Move towards the most significant part of the field. */ | |
08372f14 | 131 | while ((unsigned int) cur_bitshift < len) |
252b5132 RH |
132 | { |
133 | if (len - cur_bitshift < FLOATFORMAT_CHAR_BIT) | |
134 | /* This is the last byte; zero out the bits which are not part of | |
135 | this field. */ | |
136 | result |= | |
137 | (*(data + cur_byte) & ((1 << (len - cur_bitshift)) - 1)) | |
138 | << cur_bitshift; | |
139 | else | |
140 | result |= *(data + cur_byte) << cur_bitshift; | |
141 | cur_bitshift += FLOATFORMAT_CHAR_BIT; | |
142 | if (order == floatformat_little) | |
143 | ++cur_byte; | |
144 | else | |
145 | --cur_byte; | |
146 | } | |
147 | return result; | |
148 | } | |
149 | ||
150 | #ifndef min | |
151 | #define min(a, b) ((a) < (b) ? (a) : (b)) | |
152 | #endif | |
153 | ||
154 | /* Convert from FMT to a double. | |
155 | FROM is the address of the extended float. | |
156 | Store the double in *TO. */ | |
157 | ||
158 | void | |
159 | floatformat_to_double (fmt, from, to) | |
160 | const struct floatformat *fmt; | |
161 | char *from; | |
162 | double *to; | |
163 | { | |
164 | unsigned char *ufrom = (unsigned char *)from; | |
165 | double dto; | |
166 | long exponent; | |
167 | unsigned long mant; | |
168 | unsigned int mant_bits, mant_off; | |
169 | int mant_bits_left; | |
170 | int special_exponent; /* It's a NaN, denorm or zero */ | |
171 | ||
172 | exponent = get_field (ufrom, fmt->byteorder, fmt->totalsize, | |
173 | fmt->exp_start, fmt->exp_len); | |
174 | /* Note that if exponent indicates a NaN, we can't really do anything useful | |
175 | (not knowing if the host has NaN's, or how to build one). So it will | |
176 | end up as an infinity or something close; that is OK. */ | |
177 | ||
178 | mant_bits_left = fmt->man_len; | |
179 | mant_off = fmt->man_start; | |
180 | dto = 0.0; | |
181 | ||
08372f14 | 182 | special_exponent = exponent == 0 || (unsigned long) exponent == fmt->exp_nan; |
252b5132 RH |
183 | |
184 | /* Don't bias zero's, denorms or NaNs. */ | |
185 | if (!special_exponent) | |
186 | exponent -= fmt->exp_bias; | |
187 | ||
188 | /* Build the result algebraically. Might go infinite, underflow, etc; | |
189 | who cares. */ | |
190 | ||
191 | /* If this format uses a hidden bit, explicitly add it in now. Otherwise, | |
192 | increment the exponent by one to account for the integer bit. */ | |
193 | ||
194 | if (!special_exponent) | |
195 | { | |
196 | if (fmt->intbit == floatformat_intbit_no) | |
197 | dto = ldexp (1.0, exponent); | |
198 | else | |
199 | exponent++; | |
200 | } | |
201 | ||
202 | while (mant_bits_left > 0) | |
203 | { | |
204 | mant_bits = min (mant_bits_left, 32); | |
205 | ||
206 | mant = get_field (ufrom, fmt->byteorder, fmt->totalsize, | |
207 | mant_off, mant_bits); | |
208 | ||
209 | dto += ldexp ((double)mant, exponent - mant_bits); | |
210 | exponent -= mant_bits; | |
211 | mant_off += mant_bits; | |
212 | mant_bits_left -= mant_bits; | |
213 | } | |
214 | ||
215 | /* Negate it if negative. */ | |
216 | if (get_field (ufrom, fmt->byteorder, fmt->totalsize, fmt->sign_start, 1)) | |
217 | dto = -dto; | |
218 | *to = dto; | |
219 | } | |
220 | \f | |
221 | static void put_field PARAMS ((unsigned char *, enum floatformat_byteorders, | |
222 | unsigned int, | |
223 | unsigned int, | |
224 | unsigned int, | |
225 | unsigned long)); | |
226 | ||
227 | /* Set a field which starts at START and is LEN bytes long. DATA and | |
228 | TOTAL_LEN are the thing we are extracting it from, in byteorder ORDER. */ | |
229 | static void | |
230 | put_field (data, order, total_len, start, len, stuff_to_put) | |
231 | unsigned char *data; | |
232 | enum floatformat_byteorders order; | |
233 | unsigned int total_len; | |
234 | unsigned int start; | |
235 | unsigned int len; | |
236 | unsigned long stuff_to_put; | |
237 | { | |
238 | unsigned int cur_byte; | |
239 | int cur_bitshift; | |
240 | ||
241 | /* Start at the least significant part of the field. */ | |
242 | cur_byte = (start + len) / FLOATFORMAT_CHAR_BIT; | |
243 | if (order == floatformat_little) | |
244 | cur_byte = (total_len / FLOATFORMAT_CHAR_BIT) - cur_byte - 1; | |
245 | cur_bitshift = | |
246 | ((start + len) % FLOATFORMAT_CHAR_BIT) - FLOATFORMAT_CHAR_BIT; | |
247 | *(data + cur_byte) &= | |
248 | ~(((1 << ((start + len) % FLOATFORMAT_CHAR_BIT)) - 1) << (-cur_bitshift)); | |
249 | *(data + cur_byte) |= | |
250 | (stuff_to_put & ((1 << FLOATFORMAT_CHAR_BIT) - 1)) << (-cur_bitshift); | |
251 | cur_bitshift += FLOATFORMAT_CHAR_BIT; | |
252 | if (order == floatformat_little) | |
253 | ++cur_byte; | |
254 | else | |
255 | --cur_byte; | |
256 | ||
257 | /* Move towards the most significant part of the field. */ | |
08372f14 | 258 | while ((unsigned int) cur_bitshift < len) |
252b5132 RH |
259 | { |
260 | if (len - cur_bitshift < FLOATFORMAT_CHAR_BIT) | |
261 | { | |
262 | /* This is the last byte. */ | |
263 | *(data + cur_byte) &= | |
264 | ~((1 << (len - cur_bitshift)) - 1); | |
265 | *(data + cur_byte) |= (stuff_to_put >> cur_bitshift); | |
266 | } | |
267 | else | |
268 | *(data + cur_byte) = ((stuff_to_put >> cur_bitshift) | |
269 | & ((1 << FLOATFORMAT_CHAR_BIT) - 1)); | |
270 | cur_bitshift += FLOATFORMAT_CHAR_BIT; | |
271 | if (order == floatformat_little) | |
272 | ++cur_byte; | |
273 | else | |
274 | --cur_byte; | |
275 | } | |
276 | } | |
277 | ||
278 | /* The converse: convert the double *FROM to an extended float | |
279 | and store where TO points. Neither FROM nor TO have any alignment | |
280 | restrictions. */ | |
281 | ||
282 | void | |
283 | floatformat_from_double (fmt, from, to) | |
284 | const struct floatformat *fmt; | |
285 | double *from; | |
286 | char *to; | |
287 | { | |
288 | double dfrom; | |
289 | int exponent; | |
290 | double mant; | |
291 | unsigned int mant_bits, mant_off; | |
292 | int mant_bits_left; | |
293 | unsigned char *uto = (unsigned char *)to; | |
294 | ||
295 | memcpy (&dfrom, from, sizeof (dfrom)); | |
296 | memset (uto, 0, fmt->totalsize / FLOATFORMAT_CHAR_BIT); | |
297 | if (dfrom == 0) | |
298 | return; /* Result is zero */ | |
299 | if (dfrom != dfrom) | |
300 | { | |
301 | /* From is NaN */ | |
302 | put_field (uto, fmt->byteorder, fmt->totalsize, fmt->exp_start, | |
303 | fmt->exp_len, fmt->exp_nan); | |
304 | /* Be sure it's not infinity, but NaN value is irrel */ | |
305 | put_field (uto, fmt->byteorder, fmt->totalsize, fmt->man_start, | |
306 | 32, 1); | |
307 | return; | |
308 | } | |
309 | ||
310 | /* If negative, set the sign bit. */ | |
311 | if (dfrom < 0) | |
312 | { | |
313 | put_field (uto, fmt->byteorder, fmt->totalsize, fmt->sign_start, 1, 1); | |
314 | dfrom = -dfrom; | |
315 | } | |
316 | ||
317 | /* How to tell an infinity from an ordinary number? FIXME-someday */ | |
318 | ||
319 | mant = frexp (dfrom, &exponent); | |
320 | put_field (uto, fmt->byteorder, fmt->totalsize, fmt->exp_start, fmt->exp_len, | |
321 | exponent + fmt->exp_bias - 1); | |
322 | ||
323 | mant_bits_left = fmt->man_len; | |
324 | mant_off = fmt->man_start; | |
325 | while (mant_bits_left > 0) | |
326 | { | |
327 | unsigned long mant_long; | |
328 | mant_bits = mant_bits_left < 32 ? mant_bits_left : 32; | |
329 | ||
330 | mant *= 4294967296.0; | |
331 | mant_long = (unsigned long)mant; | |
332 | mant -= mant_long; | |
333 | ||
334 | /* If the integer bit is implicit, then we need to discard it. | |
335 | If we are discarding a zero, we should be (but are not) creating | |
336 | a denormalized number which means adjusting the exponent | |
337 | (I think). */ | |
08372f14 | 338 | if ((unsigned int) mant_bits_left == fmt->man_len |
252b5132 RH |
339 | && fmt->intbit == floatformat_intbit_no) |
340 | { | |
341 | mant_long &= 0x7fffffff; | |
342 | mant_bits -= 1; | |
343 | } | |
344 | else if (mant_bits < 32) | |
345 | { | |
346 | /* The bits we want are in the most significant MANT_BITS bits of | |
347 | mant_long. Move them to the least significant. */ | |
348 | mant_long >>= 32 - mant_bits; | |
349 | } | |
350 | ||
351 | put_field (uto, fmt->byteorder, fmt->totalsize, | |
352 | mant_off, mant_bits, mant_long); | |
353 | mant_off += mant_bits; | |
354 | mant_bits_left -= mant_bits; | |
355 | } | |
356 | } | |
357 | ||
358 | ||
359 | #ifdef IEEE_DEBUG | |
360 | ||
361 | /* This is to be run on a host which uses IEEE floating point. */ | |
362 | ||
363 | void | |
364 | ieee_test (n) | |
365 | double n; | |
366 | { | |
367 | double result; | |
368 | char exten[16]; | |
369 | ||
370 | floatformat_to_double (&floatformat_ieee_double_big, &n, &result); | |
371 | if (n != result) | |
372 | printf ("Differ(to): %.20g -> %.20g\n", n, result); | |
373 | floatformat_from_double (&floatformat_ieee_double_big, &n, &result); | |
374 | if (n != result) | |
375 | printf ("Differ(from): %.20g -> %.20g\n", n, result); | |
376 | ||
377 | floatformat_from_double (&floatformat_m68881_ext, &n, exten); | |
378 | floatformat_to_double (&floatformat_m68881_ext, exten, &result); | |
379 | if (n != result) | |
380 | printf ("Differ(to+from): %.20g -> %.20g\n", n, result); | |
381 | ||
382 | #if IEEE_DEBUG > 1 | |
383 | /* This is to be run on a host which uses 68881 format. */ | |
384 | { | |
385 | long double ex = *(long double *)exten; | |
386 | if (ex != n) | |
387 | printf ("Differ(from vs. extended): %.20g\n", n); | |
388 | } | |
389 | #endif | |
390 | } | |
391 | ||
392 | int | |
393 | main () | |
394 | { | |
395 | ieee_test (0.5); | |
396 | ieee_test (256.0); | |
397 | ieee_test (0.12345); | |
398 | ieee_test (234235.78907234); | |
399 | ieee_test (-512.0); | |
400 | ieee_test (-0.004321); | |
401 | return 0; | |
402 | } | |
403 | #endif |