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