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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, | |
69 | "floatformat_ieee_double_little" | |
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 | { | |
94 | #ifdef HARRIS_FLOAT_FORMAT | |
95 | /* Harris uses raw format 128 bytes long, but the number is just an ieee | |
96 | double, and the last 64 bits are wasted. */ | |
97 | floatformat_big,128, 0, 1, 11, 0x3ff, 0x7ff, 12, 52, | |
f03aa80d AC |
98 | floatformat_intbit_no, |
99 | "floatformat_m88110_ext(harris)" | |
252b5132 RH |
100 | #else |
101 | floatformat_big, 80, 0, 1, 15, 0x3fff, 0x7fff, 16, 64, | |
f03aa80d AC |
102 | floatformat_intbit_yes, |
103 | "floatformat_m88110_ext" | |
252b5132 RH |
104 | #endif /* HARRIS_FLOAT_FORMAT */ |
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 RH |
112 | }; |
113 | \f | |
114 | static unsigned long get_field PARAMS ((unsigned char *, | |
115 | enum floatformat_byteorders, | |
116 | unsigned int, | |
117 | unsigned int, | |
118 | unsigned int)); | |
119 | ||
120 | /* Extract a field which starts at START and is LEN bytes long. DATA and | |
121 | TOTAL_LEN are the thing we are extracting it from, in byteorder ORDER. */ | |
122 | static unsigned long | |
123 | get_field (data, order, total_len, start, len) | |
124 | unsigned char *data; | |
125 | enum floatformat_byteorders order; | |
126 | unsigned int total_len; | |
127 | unsigned int start; | |
128 | unsigned int len; | |
129 | { | |
130 | unsigned long result; | |
131 | unsigned int cur_byte; | |
132 | int cur_bitshift; | |
133 | ||
134 | /* Start at the least significant part of the field. */ | |
135 | cur_byte = (start + len) / FLOATFORMAT_CHAR_BIT; | |
136 | if (order == floatformat_little) | |
137 | cur_byte = (total_len / FLOATFORMAT_CHAR_BIT) - cur_byte - 1; | |
138 | cur_bitshift = | |
139 | ((start + len) % FLOATFORMAT_CHAR_BIT) - FLOATFORMAT_CHAR_BIT; | |
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 | /* Move towards the most significant part of the field. */ | |
08372f14 | 148 | while ((unsigned int) cur_bitshift < len) |
252b5132 RH |
149 | { |
150 | if (len - cur_bitshift < FLOATFORMAT_CHAR_BIT) | |
151 | /* This is the last byte; zero out the bits which are not part of | |
152 | this field. */ | |
153 | result |= | |
154 | (*(data + cur_byte) & ((1 << (len - cur_bitshift)) - 1)) | |
155 | << cur_bitshift; | |
156 | else | |
157 | result |= *(data + cur_byte) << cur_bitshift; | |
158 | cur_bitshift += FLOATFORMAT_CHAR_BIT; | |
159 | if (order == floatformat_little) | |
160 | ++cur_byte; | |
161 | else | |
162 | --cur_byte; | |
163 | } | |
164 | return result; | |
165 | } | |
166 | ||
167 | #ifndef min | |
168 | #define min(a, b) ((a) < (b) ? (a) : (b)) | |
169 | #endif | |
170 | ||
171 | /* Convert from FMT to a double. | |
172 | FROM is the address of the extended float. | |
173 | Store the double in *TO. */ | |
174 | ||
175 | void | |
176 | floatformat_to_double (fmt, from, to) | |
177 | const struct floatformat *fmt; | |
178 | char *from; | |
179 | double *to; | |
180 | { | |
181 | unsigned char *ufrom = (unsigned char *)from; | |
182 | double dto; | |
183 | long exponent; | |
184 | unsigned long mant; | |
185 | unsigned int mant_bits, mant_off; | |
186 | int mant_bits_left; | |
187 | int special_exponent; /* It's a NaN, denorm or zero */ | |
188 | ||
189 | exponent = get_field (ufrom, fmt->byteorder, fmt->totalsize, | |
190 | fmt->exp_start, fmt->exp_len); | |
191 | /* Note that if exponent indicates a NaN, we can't really do anything useful | |
192 | (not knowing if the host has NaN's, or how to build one). So it will | |
193 | end up as an infinity or something close; that is OK. */ | |
194 | ||
195 | mant_bits_left = fmt->man_len; | |
196 | mant_off = fmt->man_start; | |
197 | dto = 0.0; | |
198 | ||
08372f14 | 199 | special_exponent = exponent == 0 || (unsigned long) exponent == fmt->exp_nan; |
252b5132 RH |
200 | |
201 | /* Don't bias zero's, denorms or NaNs. */ | |
202 | if (!special_exponent) | |
203 | exponent -= fmt->exp_bias; | |
204 | ||
205 | /* Build the result algebraically. Might go infinite, underflow, etc; | |
206 | who cares. */ | |
207 | ||
208 | /* If this format uses a hidden bit, explicitly add it in now. Otherwise, | |
209 | increment the exponent by one to account for the integer bit. */ | |
210 | ||
211 | if (!special_exponent) | |
212 | { | |
213 | if (fmt->intbit == floatformat_intbit_no) | |
214 | dto = ldexp (1.0, exponent); | |
215 | else | |
216 | exponent++; | |
217 | } | |
218 | ||
219 | while (mant_bits_left > 0) | |
220 | { | |
221 | mant_bits = min (mant_bits_left, 32); | |
222 | ||
223 | mant = get_field (ufrom, fmt->byteorder, fmt->totalsize, | |
224 | mant_off, mant_bits); | |
225 | ||
226 | dto += ldexp ((double)mant, exponent - mant_bits); | |
227 | exponent -= mant_bits; | |
228 | mant_off += mant_bits; | |
229 | mant_bits_left -= mant_bits; | |
230 | } | |
231 | ||
232 | /* Negate it if negative. */ | |
233 | if (get_field (ufrom, fmt->byteorder, fmt->totalsize, fmt->sign_start, 1)) | |
234 | dto = -dto; | |
235 | *to = dto; | |
236 | } | |
237 | \f | |
238 | static void put_field PARAMS ((unsigned char *, enum floatformat_byteorders, | |
239 | unsigned int, | |
240 | unsigned int, | |
241 | unsigned int, | |
242 | unsigned long)); | |
243 | ||
244 | /* Set a field which starts at START and is LEN bytes long. DATA and | |
245 | TOTAL_LEN are the thing we are extracting it from, in byteorder ORDER. */ | |
246 | static void | |
247 | put_field (data, order, total_len, start, len, stuff_to_put) | |
248 | unsigned char *data; | |
249 | enum floatformat_byteorders order; | |
250 | unsigned int total_len; | |
251 | unsigned int start; | |
252 | unsigned int len; | |
253 | unsigned long stuff_to_put; | |
254 | { | |
255 | unsigned int cur_byte; | |
256 | int cur_bitshift; | |
257 | ||
258 | /* Start at the least significant part of the field. */ | |
259 | cur_byte = (start + len) / FLOATFORMAT_CHAR_BIT; | |
260 | if (order == floatformat_little) | |
261 | cur_byte = (total_len / FLOATFORMAT_CHAR_BIT) - cur_byte - 1; | |
262 | cur_bitshift = | |
263 | ((start + len) % FLOATFORMAT_CHAR_BIT) - FLOATFORMAT_CHAR_BIT; | |
264 | *(data + cur_byte) &= | |
265 | ~(((1 << ((start + len) % FLOATFORMAT_CHAR_BIT)) - 1) << (-cur_bitshift)); | |
266 | *(data + cur_byte) |= | |
267 | (stuff_to_put & ((1 << FLOATFORMAT_CHAR_BIT) - 1)) << (-cur_bitshift); | |
268 | cur_bitshift += FLOATFORMAT_CHAR_BIT; | |
269 | if (order == floatformat_little) | |
270 | ++cur_byte; | |
271 | else | |
272 | --cur_byte; | |
273 | ||
274 | /* Move towards the most significant part of the field. */ | |
08372f14 | 275 | while ((unsigned int) cur_bitshift < len) |
252b5132 RH |
276 | { |
277 | if (len - cur_bitshift < FLOATFORMAT_CHAR_BIT) | |
278 | { | |
279 | /* This is the last byte. */ | |
280 | *(data + cur_byte) &= | |
281 | ~((1 << (len - cur_bitshift)) - 1); | |
282 | *(data + cur_byte) |= (stuff_to_put >> cur_bitshift); | |
283 | } | |
284 | else | |
285 | *(data + cur_byte) = ((stuff_to_put >> cur_bitshift) | |
286 | & ((1 << FLOATFORMAT_CHAR_BIT) - 1)); | |
287 | cur_bitshift += FLOATFORMAT_CHAR_BIT; | |
288 | if (order == floatformat_little) | |
289 | ++cur_byte; | |
290 | else | |
291 | --cur_byte; | |
292 | } | |
293 | } | |
294 | ||
295 | /* The converse: convert the double *FROM to an extended float | |
296 | and store where TO points. Neither FROM nor TO have any alignment | |
297 | restrictions. */ | |
298 | ||
299 | void | |
300 | floatformat_from_double (fmt, from, to) | |
301 | const struct floatformat *fmt; | |
302 | double *from; | |
303 | char *to; | |
304 | { | |
305 | double dfrom; | |
306 | int exponent; | |
307 | double mant; | |
308 | unsigned int mant_bits, mant_off; | |
309 | int mant_bits_left; | |
310 | unsigned char *uto = (unsigned char *)to; | |
311 | ||
312 | memcpy (&dfrom, from, sizeof (dfrom)); | |
313 | memset (uto, 0, fmt->totalsize / FLOATFORMAT_CHAR_BIT); | |
314 | if (dfrom == 0) | |
315 | return; /* Result is zero */ | |
316 | if (dfrom != dfrom) | |
317 | { | |
318 | /* From is NaN */ | |
319 | put_field (uto, fmt->byteorder, fmt->totalsize, fmt->exp_start, | |
320 | fmt->exp_len, fmt->exp_nan); | |
321 | /* Be sure it's not infinity, but NaN value is irrel */ | |
322 | put_field (uto, fmt->byteorder, fmt->totalsize, fmt->man_start, | |
323 | 32, 1); | |
324 | return; | |
325 | } | |
326 | ||
327 | /* If negative, set the sign bit. */ | |
328 | if (dfrom < 0) | |
329 | { | |
330 | put_field (uto, fmt->byteorder, fmt->totalsize, fmt->sign_start, 1, 1); | |
331 | dfrom = -dfrom; | |
332 | } | |
333 | ||
334 | /* How to tell an infinity from an ordinary number? FIXME-someday */ | |
335 | ||
336 | mant = frexp (dfrom, &exponent); | |
337 | put_field (uto, fmt->byteorder, fmt->totalsize, fmt->exp_start, fmt->exp_len, | |
338 | exponent + fmt->exp_bias - 1); | |
339 | ||
340 | mant_bits_left = fmt->man_len; | |
341 | mant_off = fmt->man_start; | |
342 | while (mant_bits_left > 0) | |
343 | { | |
344 | unsigned long mant_long; | |
345 | mant_bits = mant_bits_left < 32 ? mant_bits_left : 32; | |
346 | ||
347 | mant *= 4294967296.0; | |
348 | mant_long = (unsigned long)mant; | |
349 | mant -= mant_long; | |
350 | ||
351 | /* If the integer bit is implicit, then we need to discard it. | |
352 | If we are discarding a zero, we should be (but are not) creating | |
353 | a denormalized number which means adjusting the exponent | |
354 | (I think). */ | |
08372f14 | 355 | if ((unsigned int) mant_bits_left == fmt->man_len |
252b5132 RH |
356 | && fmt->intbit == floatformat_intbit_no) |
357 | { | |
358 | mant_long &= 0x7fffffff; | |
359 | mant_bits -= 1; | |
360 | } | |
361 | else if (mant_bits < 32) | |
362 | { | |
363 | /* The bits we want are in the most significant MANT_BITS bits of | |
364 | mant_long. Move them to the least significant. */ | |
365 | mant_long >>= 32 - mant_bits; | |
366 | } | |
367 | ||
368 | put_field (uto, fmt->byteorder, fmt->totalsize, | |
369 | mant_off, mant_bits, mant_long); | |
370 | mant_off += mant_bits; | |
371 | mant_bits_left -= mant_bits; | |
372 | } | |
373 | } | |
374 | ||
375 | ||
376 | #ifdef IEEE_DEBUG | |
377 | ||
378 | /* This is to be run on a host which uses IEEE floating point. */ | |
379 | ||
380 | void | |
381 | ieee_test (n) | |
382 | double n; | |
383 | { | |
384 | double result; | |
385 | char exten[16]; | |
386 | ||
387 | floatformat_to_double (&floatformat_ieee_double_big, &n, &result); | |
388 | if (n != result) | |
389 | printf ("Differ(to): %.20g -> %.20g\n", n, result); | |
390 | floatformat_from_double (&floatformat_ieee_double_big, &n, &result); | |
391 | if (n != result) | |
392 | printf ("Differ(from): %.20g -> %.20g\n", n, result); | |
393 | ||
394 | floatformat_from_double (&floatformat_m68881_ext, &n, exten); | |
395 | floatformat_to_double (&floatformat_m68881_ext, exten, &result); | |
396 | if (n != result) | |
397 | printf ("Differ(to+from): %.20g -> %.20g\n", n, result); | |
398 | ||
399 | #if IEEE_DEBUG > 1 | |
400 | /* This is to be run on a host which uses 68881 format. */ | |
401 | { | |
402 | long double ex = *(long double *)exten; | |
403 | if (ex != n) | |
404 | printf ("Differ(from vs. extended): %.20g\n", n); | |
405 | } | |
406 | #endif | |
407 | } | |
408 | ||
409 | int | |
410 | main () | |
411 | { | |
412 | ieee_test (0.5); | |
413 | ieee_test (256.0); | |
414 | ieee_test (0.12345); | |
415 | ieee_test (234235.78907234); | |
416 | ieee_test (-512.0); | |
417 | ieee_test (-0.004321); | |
418 | return 0; | |
419 | } | |
420 | #endif |