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252b5132 | 1 | /* IEEE floating point support routines, for GDB, the GNU Debugger. |
f03aa80d | 2 | Copyright (C) 1991, 1994, 1999, 2000 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 | { | |
f03aa80d AC |
39 | floatformat_big, 32, 0, 1, 8, 127, 255, 9, 23, |
40 | floatformat_intbit_no, | |
41 | "floatformat_ieee_single_big" | |
252b5132 RH |
42 | }; |
43 | const struct floatformat floatformat_ieee_single_little = | |
44 | { | |
f03aa80d AC |
45 | floatformat_little, 32, 0, 1, 8, 127, 255, 9, 23, |
46 | floatformat_intbit_no, | |
47 | "floatformat_ieee_single_little" | |
252b5132 RH |
48 | }; |
49 | const struct floatformat floatformat_ieee_double_big = | |
50 | { | |
f03aa80d AC |
51 | floatformat_big, 64, 0, 1, 11, 1023, 2047, 12, 52, |
52 | floatformat_intbit_no, | |
53 | "floatformat_ieee_double_big" | |
252b5132 RH |
54 | }; |
55 | const struct floatformat floatformat_ieee_double_little = | |
56 | { | |
f03aa80d AC |
57 | floatformat_little, 64, 0, 1, 11, 1023, 2047, 12, 52, |
58 | floatformat_intbit_no, | |
59 | "floatformat_ieee_double_little" | |
252b5132 RH |
60 | }; |
61 | ||
62 | /* floatformat for IEEE double, little endian byte order, with big endian word | |
63 | ordering, as on the ARM. */ | |
64 | ||
65 | const struct floatformat floatformat_ieee_double_littlebyte_bigword = | |
66 | { | |
f03aa80d AC |
67 | floatformat_littlebyte_bigword, 64, 0, 1, 11, 1023, 2047, 12, 52, |
68 | floatformat_intbit_no, | |
16bad250 | 69 | "floatformat_ieee_double_littlebyte_bigword" |
252b5132 RH |
70 | }; |
71 | ||
72 | const struct floatformat floatformat_i387_ext = | |
73 | { | |
74 | floatformat_little, 80, 0, 1, 15, 0x3fff, 0x7fff, 16, 64, | |
f03aa80d AC |
75 | floatformat_intbit_yes, |
76 | "floatformat_i387_ext" | |
252b5132 RH |
77 | }; |
78 | const struct floatformat floatformat_m68881_ext = | |
79 | { | |
80 | /* Note that the bits from 16 to 31 are unused. */ | |
f03aa80d AC |
81 | floatformat_big, 96, 0, 1, 15, 0x3fff, 0x7fff, 32, 64, |
82 | floatformat_intbit_yes, | |
83 | "floatformat_m68881_ext" | |
252b5132 RH |
84 | }; |
85 | const struct floatformat floatformat_i960_ext = | |
86 | { | |
87 | /* Note that the bits from 0 to 15 are unused. */ | |
88 | floatformat_little, 96, 16, 17, 15, 0x3fff, 0x7fff, 32, 64, | |
f03aa80d AC |
89 | floatformat_intbit_yes, |
90 | "floatformat_i960_ext" | |
252b5132 RH |
91 | }; |
92 | const struct floatformat floatformat_m88110_ext = | |
93 | { | |
eb828599 AC |
94 | floatformat_big, 80, 0, 1, 15, 0x3fff, 0x7fff, 16, 64, |
95 | floatformat_intbit_yes, | |
96 | "floatformat_m88110_ext" | |
97 | }; | |
98 | const struct floatformat floatformat_m88110_harris_ext = | |
99 | { | |
252b5132 RH |
100 | /* Harris uses raw format 128 bytes long, but the number is just an ieee |
101 | double, and the last 64 bits are wasted. */ | |
102 | floatformat_big,128, 0, 1, 11, 0x3ff, 0x7ff, 12, 52, | |
f03aa80d | 103 | floatformat_intbit_no, |
eb828599 | 104 | "floatformat_m88110_ext_harris" |
252b5132 RH |
105 | }; |
106 | const struct floatformat floatformat_arm_ext = | |
107 | { | |
108 | /* Bits 1 to 16 are unused. */ | |
109 | floatformat_big, 96, 0, 17, 15, 0x3fff, 0x7fff, 32, 64, | |
f03aa80d AC |
110 | floatformat_intbit_yes, |
111 | "floatformat_arm_ext" | |
252b5132 | 112 | }; |
eb828599 AC |
113 | const struct floatformat floatformat_arm_ext_big = |
114 | { | |
115 | /* Bits 1 to 16 are unused. */ | |
116 | floatformat_big, 96, 0, 17, 15, 0x3fff, 0x7fff, 32, 64, | |
117 | floatformat_intbit_yes, | |
118 | "floatformat_arm_ext_big" | |
119 | }; | |
120 | const struct floatformat floatformat_arm_ext_littlebyte_bigword = | |
121 | { | |
122 | /* Bits 1 to 16 are unused. */ | |
123 | floatformat_littlebyte_bigword, 96, 0, 17, 15, 0x3fff, 0x7fff, 32, 64, | |
124 | floatformat_intbit_yes, | |
125 | "floatformat_arm_ext_littlebyte_bigword" | |
126 | }; | |
127 | const struct floatformat floatformat_ia64_spill_big = | |
128 | { | |
129 | floatformat_big, 128, 0, 1, 17, 65535, 0x1ffff, 18, 64, | |
130 | floatformat_intbit_yes, | |
131 | "floatformat_ia64_spill_big" | |
132 | }; | |
133 | const struct floatformat floatformat_ia64_spill_little = | |
134 | { | |
135 | floatformat_little, 128, 0, 1, 17, 65535, 0x1ffff, 18, 64, | |
136 | floatformat_intbit_yes, | |
137 | "floatformat_ia64_spill_little" | |
138 | }; | |
139 | const struct floatformat floatformat_ia64_quad_big = | |
140 | { | |
141 | floatformat_big, 128, 0, 1, 15, 16383, 0x7fff, 16, 112, | |
142 | floatformat_intbit_no, | |
143 | "floatformat_ia64_quad_big" | |
144 | }; | |
145 | const struct floatformat floatformat_ia64_quad_little = | |
146 | { | |
147 | floatformat_little, 128, 0, 1, 15, 16383, 0x7fff, 16, 112, | |
148 | floatformat_intbit_no, | |
149 | "floatformat_ia64_quad_little" | |
150 | }; | |
252b5132 RH |
151 | \f |
152 | static unsigned long get_field PARAMS ((unsigned char *, | |
153 | enum floatformat_byteorders, | |
154 | unsigned int, | |
155 | unsigned int, | |
156 | unsigned int)); | |
157 | ||
158 | /* Extract a field which starts at START and is LEN bytes long. DATA and | |
159 | TOTAL_LEN are the thing we are extracting it from, in byteorder ORDER. */ | |
160 | static unsigned long | |
161 | get_field (data, order, total_len, start, len) | |
162 | unsigned char *data; | |
163 | enum floatformat_byteorders order; | |
164 | unsigned int total_len; | |
165 | unsigned int start; | |
166 | unsigned int len; | |
167 | { | |
168 | unsigned long result; | |
169 | unsigned int cur_byte; | |
170 | int cur_bitshift; | |
171 | ||
172 | /* Start at the least significant part of the field. */ | |
173 | cur_byte = (start + len) / FLOATFORMAT_CHAR_BIT; | |
174 | if (order == floatformat_little) | |
175 | cur_byte = (total_len / FLOATFORMAT_CHAR_BIT) - cur_byte - 1; | |
176 | cur_bitshift = | |
177 | ((start + len) % FLOATFORMAT_CHAR_BIT) - FLOATFORMAT_CHAR_BIT; | |
178 | result = *(data + cur_byte) >> (-cur_bitshift); | |
179 | cur_bitshift += FLOATFORMAT_CHAR_BIT; | |
180 | if (order == floatformat_little) | |
181 | ++cur_byte; | |
182 | else | |
183 | --cur_byte; | |
184 | ||
185 | /* Move towards the most significant part of the field. */ | |
08372f14 | 186 | while ((unsigned int) cur_bitshift < len) |
252b5132 RH |
187 | { |
188 | if (len - cur_bitshift < FLOATFORMAT_CHAR_BIT) | |
189 | /* This is the last byte; zero out the bits which are not part of | |
190 | this field. */ | |
191 | result |= | |
192 | (*(data + cur_byte) & ((1 << (len - cur_bitshift)) - 1)) | |
193 | << cur_bitshift; | |
194 | else | |
195 | result |= *(data + cur_byte) << cur_bitshift; | |
196 | cur_bitshift += FLOATFORMAT_CHAR_BIT; | |
197 | if (order == floatformat_little) | |
198 | ++cur_byte; | |
199 | else | |
200 | --cur_byte; | |
201 | } | |
202 | return result; | |
203 | } | |
204 | ||
205 | #ifndef min | |
206 | #define min(a, b) ((a) < (b) ? (a) : (b)) | |
207 | #endif | |
208 | ||
209 | /* Convert from FMT to a double. | |
210 | FROM is the address of the extended float. | |
211 | Store the double in *TO. */ | |
212 | ||
213 | void | |
214 | floatformat_to_double (fmt, from, to) | |
215 | const struct floatformat *fmt; | |
216 | char *from; | |
217 | double *to; | |
218 | { | |
219 | unsigned char *ufrom = (unsigned char *)from; | |
220 | double dto; | |
221 | long exponent; | |
222 | unsigned long mant; | |
223 | unsigned int mant_bits, mant_off; | |
224 | int mant_bits_left; | |
225 | int special_exponent; /* It's a NaN, denorm or zero */ | |
226 | ||
227 | exponent = get_field (ufrom, fmt->byteorder, fmt->totalsize, | |
228 | fmt->exp_start, fmt->exp_len); | |
229 | /* Note that if exponent indicates a NaN, we can't really do anything useful | |
230 | (not knowing if the host has NaN's, or how to build one). So it will | |
231 | end up as an infinity or something close; that is OK. */ | |
232 | ||
233 | mant_bits_left = fmt->man_len; | |
234 | mant_off = fmt->man_start; | |
235 | dto = 0.0; | |
236 | ||
08372f14 | 237 | special_exponent = exponent == 0 || (unsigned long) exponent == fmt->exp_nan; |
252b5132 RH |
238 | |
239 | /* Don't bias zero's, denorms or NaNs. */ | |
240 | if (!special_exponent) | |
241 | exponent -= fmt->exp_bias; | |
242 | ||
243 | /* Build the result algebraically. Might go infinite, underflow, etc; | |
244 | who cares. */ | |
245 | ||
246 | /* If this format uses a hidden bit, explicitly add it in now. Otherwise, | |
247 | increment the exponent by one to account for the integer bit. */ | |
248 | ||
249 | if (!special_exponent) | |
250 | { | |
251 | if (fmt->intbit == floatformat_intbit_no) | |
252 | dto = ldexp (1.0, exponent); | |
253 | else | |
254 | exponent++; | |
255 | } | |
256 | ||
257 | while (mant_bits_left > 0) | |
258 | { | |
259 | mant_bits = min (mant_bits_left, 32); | |
260 | ||
261 | mant = get_field (ufrom, fmt->byteorder, fmt->totalsize, | |
262 | mant_off, mant_bits); | |
263 | ||
264 | dto += ldexp ((double)mant, exponent - mant_bits); | |
265 | exponent -= mant_bits; | |
266 | mant_off += mant_bits; | |
267 | mant_bits_left -= mant_bits; | |
268 | } | |
269 | ||
270 | /* Negate it if negative. */ | |
271 | if (get_field (ufrom, fmt->byteorder, fmt->totalsize, fmt->sign_start, 1)) | |
272 | dto = -dto; | |
273 | *to = dto; | |
274 | } | |
275 | \f | |
276 | static void put_field PARAMS ((unsigned char *, enum floatformat_byteorders, | |
277 | unsigned int, | |
278 | unsigned int, | |
279 | unsigned int, | |
280 | unsigned long)); | |
281 | ||
282 | /* Set a field which starts at START and is LEN bytes long. DATA and | |
283 | TOTAL_LEN are the thing we are extracting it from, in byteorder ORDER. */ | |
284 | static void | |
285 | put_field (data, order, total_len, start, len, stuff_to_put) | |
286 | unsigned char *data; | |
287 | enum floatformat_byteorders order; | |
288 | unsigned int total_len; | |
289 | unsigned int start; | |
290 | unsigned int len; | |
291 | unsigned long stuff_to_put; | |
292 | { | |
293 | unsigned int cur_byte; | |
294 | int cur_bitshift; | |
295 | ||
296 | /* Start at the least significant part of the field. */ | |
297 | cur_byte = (start + len) / FLOATFORMAT_CHAR_BIT; | |
298 | if (order == floatformat_little) | |
299 | cur_byte = (total_len / FLOATFORMAT_CHAR_BIT) - cur_byte - 1; | |
300 | cur_bitshift = | |
301 | ((start + len) % FLOATFORMAT_CHAR_BIT) - FLOATFORMAT_CHAR_BIT; | |
302 | *(data + cur_byte) &= | |
303 | ~(((1 << ((start + len) % FLOATFORMAT_CHAR_BIT)) - 1) << (-cur_bitshift)); | |
304 | *(data + cur_byte) |= | |
305 | (stuff_to_put & ((1 << FLOATFORMAT_CHAR_BIT) - 1)) << (-cur_bitshift); | |
306 | cur_bitshift += FLOATFORMAT_CHAR_BIT; | |
307 | if (order == floatformat_little) | |
308 | ++cur_byte; | |
309 | else | |
310 | --cur_byte; | |
311 | ||
312 | /* Move towards the most significant part of the field. */ | |
08372f14 | 313 | while ((unsigned int) cur_bitshift < len) |
252b5132 RH |
314 | { |
315 | if (len - cur_bitshift < FLOATFORMAT_CHAR_BIT) | |
316 | { | |
317 | /* This is the last byte. */ | |
318 | *(data + cur_byte) &= | |
319 | ~((1 << (len - cur_bitshift)) - 1); | |
320 | *(data + cur_byte) |= (stuff_to_put >> cur_bitshift); | |
321 | } | |
322 | else | |
323 | *(data + cur_byte) = ((stuff_to_put >> cur_bitshift) | |
324 | & ((1 << FLOATFORMAT_CHAR_BIT) - 1)); | |
325 | cur_bitshift += FLOATFORMAT_CHAR_BIT; | |
326 | if (order == floatformat_little) | |
327 | ++cur_byte; | |
328 | else | |
329 | --cur_byte; | |
330 | } | |
331 | } | |
332 | ||
333 | /* The converse: convert the double *FROM to an extended float | |
334 | and store where TO points. Neither FROM nor TO have any alignment | |
335 | restrictions. */ | |
336 | ||
337 | void | |
338 | floatformat_from_double (fmt, from, to) | |
339 | const struct floatformat *fmt; | |
340 | double *from; | |
341 | char *to; | |
342 | { | |
343 | double dfrom; | |
344 | int exponent; | |
345 | double mant; | |
346 | unsigned int mant_bits, mant_off; | |
347 | int mant_bits_left; | |
348 | unsigned char *uto = (unsigned char *)to; | |
349 | ||
350 | memcpy (&dfrom, from, sizeof (dfrom)); | |
351 | memset (uto, 0, fmt->totalsize / FLOATFORMAT_CHAR_BIT); | |
352 | if (dfrom == 0) | |
353 | return; /* Result is zero */ | |
354 | if (dfrom != dfrom) | |
355 | { | |
356 | /* From is NaN */ | |
357 | put_field (uto, fmt->byteorder, fmt->totalsize, fmt->exp_start, | |
358 | fmt->exp_len, fmt->exp_nan); | |
359 | /* Be sure it's not infinity, but NaN value is irrel */ | |
360 | put_field (uto, fmt->byteorder, fmt->totalsize, fmt->man_start, | |
361 | 32, 1); | |
362 | return; | |
363 | } | |
364 | ||
365 | /* If negative, set the sign bit. */ | |
366 | if (dfrom < 0) | |
367 | { | |
368 | put_field (uto, fmt->byteorder, fmt->totalsize, fmt->sign_start, 1, 1); | |
369 | dfrom = -dfrom; | |
370 | } | |
371 | ||
372 | /* How to tell an infinity from an ordinary number? FIXME-someday */ | |
373 | ||
374 | mant = frexp (dfrom, &exponent); | |
375 | put_field (uto, fmt->byteorder, fmt->totalsize, fmt->exp_start, fmt->exp_len, | |
376 | exponent + fmt->exp_bias - 1); | |
377 | ||
378 | mant_bits_left = fmt->man_len; | |
379 | mant_off = fmt->man_start; | |
380 | while (mant_bits_left > 0) | |
381 | { | |
382 | unsigned long mant_long; | |
383 | mant_bits = mant_bits_left < 32 ? mant_bits_left : 32; | |
384 | ||
385 | mant *= 4294967296.0; | |
386 | mant_long = (unsigned long)mant; | |
387 | mant -= mant_long; | |
388 | ||
389 | /* If the integer bit is implicit, then we need to discard it. | |
390 | If we are discarding a zero, we should be (but are not) creating | |
391 | a denormalized number which means adjusting the exponent | |
392 | (I think). */ | |
08372f14 | 393 | if ((unsigned int) mant_bits_left == fmt->man_len |
252b5132 RH |
394 | && fmt->intbit == floatformat_intbit_no) |
395 | { | |
396 | mant_long &= 0x7fffffff; | |
397 | mant_bits -= 1; | |
398 | } | |
399 | else if (mant_bits < 32) | |
400 | { | |
401 | /* The bits we want are in the most significant MANT_BITS bits of | |
402 | mant_long. Move them to the least significant. */ | |
403 | mant_long >>= 32 - mant_bits; | |
404 | } | |
405 | ||
406 | put_field (uto, fmt->byteorder, fmt->totalsize, | |
407 | mant_off, mant_bits, mant_long); | |
408 | mant_off += mant_bits; | |
409 | mant_bits_left -= mant_bits; | |
410 | } | |
411 | } | |
412 | ||
413 | ||
414 | #ifdef IEEE_DEBUG | |
415 | ||
416 | /* This is to be run on a host which uses IEEE floating point. */ | |
417 | ||
418 | void | |
419 | ieee_test (n) | |
420 | double n; | |
421 | { | |
422 | double result; | |
423 | char exten[16]; | |
424 | ||
425 | floatformat_to_double (&floatformat_ieee_double_big, &n, &result); | |
426 | if (n != result) | |
427 | printf ("Differ(to): %.20g -> %.20g\n", n, result); | |
428 | floatformat_from_double (&floatformat_ieee_double_big, &n, &result); | |
429 | if (n != result) | |
430 | printf ("Differ(from): %.20g -> %.20g\n", n, result); | |
431 | ||
432 | floatformat_from_double (&floatformat_m68881_ext, &n, exten); | |
433 | floatformat_to_double (&floatformat_m68881_ext, exten, &result); | |
434 | if (n != result) | |
435 | printf ("Differ(to+from): %.20g -> %.20g\n", n, result); | |
436 | ||
437 | #if IEEE_DEBUG > 1 | |
438 | /* This is to be run on a host which uses 68881 format. */ | |
439 | { | |
440 | long double ex = *(long double *)exten; | |
441 | if (ex != n) | |
442 | printf ("Differ(from vs. extended): %.20g\n", n); | |
443 | } | |
444 | #endif | |
445 | } | |
446 | ||
447 | int | |
448 | main () | |
449 | { | |
450 | ieee_test (0.5); | |
451 | ieee_test (256.0); | |
452 | ieee_test (0.12345); | |
453 | ieee_test (234235.78907234); | |
454 | ieee_test (-512.0); | |
455 | ieee_test (-0.004321); | |
456 | return 0; | |
457 | } | |
458 | #endif |