floatformat.c revision 1.1.1.5 1 1.1 mrg /* IEEE floating point support routines, for GDB, the GNU Debugger.
2 1.1.1.5 mrg Copyright (C) 1991-2017 Free Software Foundation, Inc.
3 1.1 mrg
4 1.1 mrg This file is part of GDB.
5 1.1 mrg
6 1.1 mrg This program is free software; you can redistribute it and/or modify
7 1.1 mrg it under the terms of the GNU General Public License as published by
8 1.1 mrg the Free Software Foundation; either version 2 of the License, or
9 1.1 mrg (at your option) any later version.
10 1.1 mrg
11 1.1 mrg This program is distributed in the hope that it will be useful,
12 1.1 mrg but WITHOUT ANY WARRANTY; without even the implied warranty of
13 1.1 mrg MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 1.1 mrg GNU General Public License for more details.
15 1.1 mrg
16 1.1 mrg You should have received a copy of the GNU General Public License
17 1.1 mrg along with this program; if not, write to the Free Software
18 1.1 mrg Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston, MA 02110-1301, USA. */
19 1.1 mrg
20 1.1 mrg /* This is needed to pick up the NAN macro on some systems. */
21 1.1.1.4 mrg #ifndef _GNU_SOURCE
22 1.1 mrg #define _GNU_SOURCE
23 1.1.1.4 mrg #endif
24 1.1 mrg
25 1.1 mrg #ifdef HAVE_CONFIG_H
26 1.1 mrg #include "config.h"
27 1.1 mrg #endif
28 1.1 mrg
29 1.1 mrg #include <math.h>
30 1.1 mrg
31 1.1 mrg #ifdef HAVE_STRING_H
32 1.1 mrg #include <string.h>
33 1.1 mrg #endif
34 1.1 mrg
35 1.1 mrg /* On some platforms, <float.h> provides DBL_QNAN. */
36 1.1 mrg #ifdef STDC_HEADERS
37 1.1 mrg #include <float.h>
38 1.1 mrg #endif
39 1.1 mrg
40 1.1 mrg #include "ansidecl.h"
41 1.1 mrg #include "libiberty.h"
42 1.1 mrg #include "floatformat.h"
43 1.1 mrg
44 1.1 mrg #ifndef INFINITY
45 1.1 mrg #ifdef HUGE_VAL
46 1.1 mrg #define INFINITY HUGE_VAL
47 1.1 mrg #else
48 1.1 mrg #define INFINITY (1.0 / 0.0)
49 1.1 mrg #endif
50 1.1 mrg #endif
51 1.1 mrg
52 1.1 mrg #ifndef NAN
53 1.1 mrg #ifdef DBL_QNAN
54 1.1 mrg #define NAN DBL_QNAN
55 1.1 mrg #else
56 1.1 mrg #define NAN (0.0 / 0.0)
57 1.1 mrg #endif
58 1.1 mrg #endif
59 1.1 mrg
60 1.1 mrg static int mant_bits_set (const struct floatformat *, const unsigned char *);
61 1.1 mrg static unsigned long get_field (const unsigned char *,
62 1.1 mrg enum floatformat_byteorders,
63 1.1 mrg unsigned int,
64 1.1 mrg unsigned int,
65 1.1 mrg unsigned int);
66 1.1 mrg static int floatformat_always_valid (const struct floatformat *fmt,
67 1.1 mrg const void *from);
68 1.1 mrg
69 1.1 mrg static int
70 1.1 mrg floatformat_always_valid (const struct floatformat *fmt ATTRIBUTE_UNUSED,
71 1.1 mrg const void *from ATTRIBUTE_UNUSED)
72 1.1 mrg {
73 1.1 mrg return 1;
74 1.1 mrg }
75 1.1 mrg
76 1.1 mrg /* The odds that CHAR_BIT will be anything but 8 are low enough that I'm not
77 1.1 mrg going to bother with trying to muck around with whether it is defined in
78 1.1 mrg a system header, what we do if not, etc. */
79 1.1 mrg #define FLOATFORMAT_CHAR_BIT 8
80 1.1 mrg
81 1.1.1.2 mrg /* floatformats for IEEE half, single and double, big and little endian. */
82 1.1.1.2 mrg const struct floatformat floatformat_ieee_half_big =
83 1.1.1.2 mrg {
84 1.1.1.2 mrg floatformat_big, 16, 0, 1, 5, 15, 31, 6, 10,
85 1.1.1.2 mrg floatformat_intbit_no,
86 1.1.1.2 mrg "floatformat_ieee_half_big",
87 1.1.1.2 mrg floatformat_always_valid,
88 1.1.1.2 mrg NULL
89 1.1.1.2 mrg };
90 1.1.1.2 mrg const struct floatformat floatformat_ieee_half_little =
91 1.1.1.2 mrg {
92 1.1.1.2 mrg floatformat_little, 16, 0, 1, 5, 15, 31, 6, 10,
93 1.1.1.2 mrg floatformat_intbit_no,
94 1.1.1.2 mrg "floatformat_ieee_half_little",
95 1.1.1.2 mrg floatformat_always_valid,
96 1.1.1.2 mrg NULL
97 1.1.1.2 mrg };
98 1.1 mrg const struct floatformat floatformat_ieee_single_big =
99 1.1 mrg {
100 1.1 mrg floatformat_big, 32, 0, 1, 8, 127, 255, 9, 23,
101 1.1 mrg floatformat_intbit_no,
102 1.1 mrg "floatformat_ieee_single_big",
103 1.1 mrg floatformat_always_valid,
104 1.1 mrg NULL
105 1.1 mrg };
106 1.1 mrg const struct floatformat floatformat_ieee_single_little =
107 1.1 mrg {
108 1.1 mrg floatformat_little, 32, 0, 1, 8, 127, 255, 9, 23,
109 1.1 mrg floatformat_intbit_no,
110 1.1 mrg "floatformat_ieee_single_little",
111 1.1 mrg floatformat_always_valid,
112 1.1 mrg NULL
113 1.1 mrg };
114 1.1 mrg const struct floatformat floatformat_ieee_double_big =
115 1.1 mrg {
116 1.1 mrg floatformat_big, 64, 0, 1, 11, 1023, 2047, 12, 52,
117 1.1 mrg floatformat_intbit_no,
118 1.1 mrg "floatformat_ieee_double_big",
119 1.1 mrg floatformat_always_valid,
120 1.1 mrg NULL
121 1.1 mrg };
122 1.1 mrg const struct floatformat floatformat_ieee_double_little =
123 1.1 mrg {
124 1.1 mrg floatformat_little, 64, 0, 1, 11, 1023, 2047, 12, 52,
125 1.1 mrg floatformat_intbit_no,
126 1.1 mrg "floatformat_ieee_double_little",
127 1.1 mrg floatformat_always_valid,
128 1.1 mrg NULL
129 1.1 mrg };
130 1.1 mrg
131 1.1 mrg /* floatformat for IEEE double, little endian byte order, with big endian word
132 1.1 mrg ordering, as on the ARM. */
133 1.1 mrg
134 1.1 mrg const struct floatformat floatformat_ieee_double_littlebyte_bigword =
135 1.1 mrg {
136 1.1 mrg floatformat_littlebyte_bigword, 64, 0, 1, 11, 1023, 2047, 12, 52,
137 1.1 mrg floatformat_intbit_no,
138 1.1 mrg "floatformat_ieee_double_littlebyte_bigword",
139 1.1 mrg floatformat_always_valid,
140 1.1 mrg NULL
141 1.1 mrg };
142 1.1 mrg
143 1.1 mrg /* floatformat for VAX. Not quite IEEE, but close enough. */
144 1.1 mrg
145 1.1 mrg const struct floatformat floatformat_vax_f =
146 1.1 mrg {
147 1.1 mrg floatformat_vax, 32, 0, 1, 8, 129, 0, 9, 23,
148 1.1 mrg floatformat_intbit_no,
149 1.1 mrg "floatformat_vax_f",
150 1.1 mrg floatformat_always_valid,
151 1.1 mrg NULL
152 1.1 mrg };
153 1.1 mrg const struct floatformat floatformat_vax_d =
154 1.1 mrg {
155 1.1 mrg floatformat_vax, 64, 0, 1, 8, 129, 0, 9, 55,
156 1.1 mrg floatformat_intbit_no,
157 1.1 mrg "floatformat_vax_d",
158 1.1 mrg floatformat_always_valid,
159 1.1 mrg NULL
160 1.1 mrg };
161 1.1 mrg const struct floatformat floatformat_vax_g =
162 1.1 mrg {
163 1.1 mrg floatformat_vax, 64, 0, 1, 11, 1025, 0, 12, 52,
164 1.1 mrg floatformat_intbit_no,
165 1.1 mrg "floatformat_vax_g",
166 1.1 mrg floatformat_always_valid,
167 1.1 mrg NULL
168 1.1 mrg };
169 1.1 mrg
170 1.1 mrg static int floatformat_i387_ext_is_valid (const struct floatformat *fmt,
171 1.1 mrg const void *from);
172 1.1 mrg
173 1.1 mrg static int
174 1.1 mrg floatformat_i387_ext_is_valid (const struct floatformat *fmt, const void *from)
175 1.1 mrg {
176 1.1 mrg /* In the i387 double-extended format, if the exponent is all ones,
177 1.1 mrg then the integer bit must be set. If the exponent is neither 0
178 1.1 mrg nor ~0, the intbit must also be set. Only if the exponent is
179 1.1 mrg zero can it be zero, and then it must be zero. */
180 1.1 mrg unsigned long exponent, int_bit;
181 1.1 mrg const unsigned char *ufrom = (const unsigned char *) from;
182 1.1 mrg
183 1.1 mrg exponent = get_field (ufrom, fmt->byteorder, fmt->totalsize,
184 1.1 mrg fmt->exp_start, fmt->exp_len);
185 1.1 mrg int_bit = get_field (ufrom, fmt->byteorder, fmt->totalsize,
186 1.1 mrg fmt->man_start, 1);
187 1.1 mrg
188 1.1 mrg if ((exponent == 0) != (int_bit == 0))
189 1.1 mrg return 0;
190 1.1 mrg else
191 1.1 mrg return 1;
192 1.1 mrg }
193 1.1 mrg
194 1.1 mrg const struct floatformat floatformat_i387_ext =
195 1.1 mrg {
196 1.1 mrg floatformat_little, 80, 0, 1, 15, 0x3fff, 0x7fff, 16, 64,
197 1.1 mrg floatformat_intbit_yes,
198 1.1 mrg "floatformat_i387_ext",
199 1.1 mrg floatformat_i387_ext_is_valid,
200 1.1 mrg NULL
201 1.1 mrg };
202 1.1 mrg const struct floatformat floatformat_m68881_ext =
203 1.1 mrg {
204 1.1 mrg /* Note that the bits from 16 to 31 are unused. */
205 1.1 mrg floatformat_big, 96, 0, 1, 15, 0x3fff, 0x7fff, 32, 64,
206 1.1 mrg floatformat_intbit_yes,
207 1.1 mrg "floatformat_m68881_ext",
208 1.1 mrg floatformat_always_valid,
209 1.1 mrg NULL
210 1.1 mrg };
211 1.1 mrg const struct floatformat floatformat_i960_ext =
212 1.1 mrg {
213 1.1 mrg /* Note that the bits from 0 to 15 are unused. */
214 1.1 mrg floatformat_little, 96, 16, 17, 15, 0x3fff, 0x7fff, 32, 64,
215 1.1 mrg floatformat_intbit_yes,
216 1.1 mrg "floatformat_i960_ext",
217 1.1 mrg floatformat_always_valid,
218 1.1 mrg NULL
219 1.1 mrg };
220 1.1 mrg const struct floatformat floatformat_m88110_ext =
221 1.1 mrg {
222 1.1 mrg floatformat_big, 80, 0, 1, 15, 0x3fff, 0x7fff, 16, 64,
223 1.1 mrg floatformat_intbit_yes,
224 1.1 mrg "floatformat_m88110_ext",
225 1.1 mrg floatformat_always_valid,
226 1.1 mrg NULL
227 1.1 mrg };
228 1.1 mrg const struct floatformat floatformat_m88110_harris_ext =
229 1.1 mrg {
230 1.1 mrg /* Harris uses raw format 128 bytes long, but the number is just an ieee
231 1.1 mrg double, and the last 64 bits are wasted. */
232 1.1 mrg floatformat_big,128, 0, 1, 11, 0x3ff, 0x7ff, 12, 52,
233 1.1 mrg floatformat_intbit_no,
234 1.1 mrg "floatformat_m88110_ext_harris",
235 1.1 mrg floatformat_always_valid,
236 1.1 mrg NULL
237 1.1 mrg };
238 1.1 mrg const struct floatformat floatformat_arm_ext_big =
239 1.1 mrg {
240 1.1 mrg /* Bits 1 to 16 are unused. */
241 1.1 mrg floatformat_big, 96, 0, 17, 15, 0x3fff, 0x7fff, 32, 64,
242 1.1 mrg floatformat_intbit_yes,
243 1.1 mrg "floatformat_arm_ext_big",
244 1.1 mrg floatformat_always_valid,
245 1.1 mrg NULL
246 1.1 mrg };
247 1.1 mrg const struct floatformat floatformat_arm_ext_littlebyte_bigword =
248 1.1 mrg {
249 1.1 mrg /* Bits 1 to 16 are unused. */
250 1.1 mrg floatformat_littlebyte_bigword, 96, 0, 17, 15, 0x3fff, 0x7fff, 32, 64,
251 1.1 mrg floatformat_intbit_yes,
252 1.1 mrg "floatformat_arm_ext_littlebyte_bigword",
253 1.1 mrg floatformat_always_valid,
254 1.1 mrg NULL
255 1.1 mrg };
256 1.1 mrg const struct floatformat floatformat_ia64_spill_big =
257 1.1 mrg {
258 1.1 mrg floatformat_big, 128, 0, 1, 17, 65535, 0x1ffff, 18, 64,
259 1.1 mrg floatformat_intbit_yes,
260 1.1 mrg "floatformat_ia64_spill_big",
261 1.1 mrg floatformat_always_valid,
262 1.1 mrg NULL
263 1.1 mrg };
264 1.1 mrg const struct floatformat floatformat_ia64_spill_little =
265 1.1 mrg {
266 1.1 mrg floatformat_little, 128, 0, 1, 17, 65535, 0x1ffff, 18, 64,
267 1.1 mrg floatformat_intbit_yes,
268 1.1 mrg "floatformat_ia64_spill_little",
269 1.1 mrg floatformat_always_valid,
270 1.1 mrg NULL
271 1.1 mrg };
272 1.1 mrg const struct floatformat floatformat_ia64_quad_big =
273 1.1 mrg {
274 1.1 mrg floatformat_big, 128, 0, 1, 15, 16383, 0x7fff, 16, 112,
275 1.1 mrg floatformat_intbit_no,
276 1.1 mrg "floatformat_ia64_quad_big",
277 1.1 mrg floatformat_always_valid,
278 1.1 mrg NULL
279 1.1 mrg };
280 1.1 mrg const struct floatformat floatformat_ia64_quad_little =
281 1.1 mrg {
282 1.1 mrg floatformat_little, 128, 0, 1, 15, 16383, 0x7fff, 16, 112,
283 1.1 mrg floatformat_intbit_no,
284 1.1 mrg "floatformat_ia64_quad_little",
285 1.1 mrg floatformat_always_valid,
286 1.1 mrg NULL
287 1.1 mrg };
288 1.1 mrg
289 1.1 mrg static int
290 1.1 mrg floatformat_ibm_long_double_is_valid (const struct floatformat *fmt,
291 1.1 mrg const void *from)
292 1.1 mrg {
293 1.1 mrg const unsigned char *ufrom = (const unsigned char *) from;
294 1.1 mrg const struct floatformat *hfmt = fmt->split_half;
295 1.1 mrg long top_exp, bot_exp;
296 1.1 mrg int top_nan = 0;
297 1.1 mrg
298 1.1 mrg top_exp = get_field (ufrom, hfmt->byteorder, hfmt->totalsize,
299 1.1 mrg hfmt->exp_start, hfmt->exp_len);
300 1.1 mrg bot_exp = get_field (ufrom + 8, hfmt->byteorder, hfmt->totalsize,
301 1.1 mrg hfmt->exp_start, hfmt->exp_len);
302 1.1 mrg
303 1.1 mrg if ((unsigned long) top_exp == hfmt->exp_nan)
304 1.1 mrg top_nan = mant_bits_set (hfmt, ufrom);
305 1.1 mrg
306 1.1 mrg /* A NaN is valid with any low part. */
307 1.1 mrg if (top_nan)
308 1.1 mrg return 1;
309 1.1 mrg
310 1.1 mrg /* An infinity, zero or denormal requires low part 0 (positive or
311 1.1 mrg negative). */
312 1.1 mrg if ((unsigned long) top_exp == hfmt->exp_nan || top_exp == 0)
313 1.1 mrg {
314 1.1 mrg if (bot_exp != 0)
315 1.1 mrg return 0;
316 1.1 mrg
317 1.1 mrg return !mant_bits_set (hfmt, ufrom + 8);
318 1.1 mrg }
319 1.1 mrg
320 1.1 mrg /* The top part is now a finite normal value. The long double value
321 1.1 mrg is the sum of the two parts, and the top part must equal the
322 1.1 mrg result of rounding the long double value to nearest double. Thus
323 1.1 mrg the bottom part must be <= 0.5ulp of the top part in absolute
324 1.1 mrg value, and if it is < 0.5ulp then the long double is definitely
325 1.1 mrg valid. */
326 1.1 mrg if (bot_exp < top_exp - 53)
327 1.1 mrg return 1;
328 1.1 mrg if (bot_exp > top_exp - 53 && bot_exp != 0)
329 1.1 mrg return 0;
330 1.1 mrg if (bot_exp == 0)
331 1.1 mrg {
332 1.1 mrg /* The bottom part is 0 or denormal. Determine which, and if
333 1.1 mrg denormal the first two set bits. */
334 1.1 mrg int first_bit = -1, second_bit = -1, cur_bit;
335 1.1 mrg for (cur_bit = 0; (unsigned int) cur_bit < hfmt->man_len; cur_bit++)
336 1.1 mrg if (get_field (ufrom + 8, hfmt->byteorder, hfmt->totalsize,
337 1.1 mrg hfmt->man_start + cur_bit, 1))
338 1.1 mrg {
339 1.1 mrg if (first_bit == -1)
340 1.1 mrg first_bit = cur_bit;
341 1.1 mrg else
342 1.1 mrg {
343 1.1 mrg second_bit = cur_bit;
344 1.1 mrg break;
345 1.1 mrg }
346 1.1 mrg }
347 1.1 mrg /* Bottom part 0 is OK. */
348 1.1 mrg if (first_bit == -1)
349 1.1 mrg return 1;
350 1.1 mrg /* The real exponent of the bottom part is -first_bit. */
351 1.1 mrg if (-first_bit < top_exp - 53)
352 1.1 mrg return 1;
353 1.1 mrg if (-first_bit > top_exp - 53)
354 1.1 mrg return 0;
355 1.1 mrg /* The bottom part is at least 0.5ulp of the top part. For this
356 1.1 mrg to be OK, the bottom part must be exactly 0.5ulp (i.e. no
357 1.1 mrg more bits set) and the top part must have last bit 0. */
358 1.1 mrg if (second_bit != -1)
359 1.1 mrg return 0;
360 1.1 mrg return !get_field (ufrom, hfmt->byteorder, hfmt->totalsize,
361 1.1 mrg hfmt->man_start + hfmt->man_len - 1, 1);
362 1.1 mrg }
363 1.1 mrg else
364 1.1 mrg {
365 1.1 mrg /* The bottom part is at least 0.5ulp of the top part. For this
366 1.1 mrg to be OK, it must be exactly 0.5ulp (i.e. no explicit bits
367 1.1 mrg set) and the top part must have last bit 0. */
368 1.1 mrg if (get_field (ufrom, hfmt->byteorder, hfmt->totalsize,
369 1.1 mrg hfmt->man_start + hfmt->man_len - 1, 1))
370 1.1 mrg return 0;
371 1.1 mrg return !mant_bits_set (hfmt, ufrom + 8);
372 1.1 mrg }
373 1.1 mrg }
374 1.1 mrg
375 1.1.1.3 mrg const struct floatformat floatformat_ibm_long_double_big =
376 1.1 mrg {
377 1.1 mrg floatformat_big, 128, 0, 1, 11, 1023, 2047, 12, 52,
378 1.1 mrg floatformat_intbit_no,
379 1.1.1.3 mrg "floatformat_ibm_long_double_big",
380 1.1 mrg floatformat_ibm_long_double_is_valid,
381 1.1 mrg &floatformat_ieee_double_big
382 1.1 mrg };
383 1.1.1.3 mrg
384 1.1.1.3 mrg const struct floatformat floatformat_ibm_long_double_little =
385 1.1.1.3 mrg {
386 1.1.1.3 mrg floatformat_little, 128, 0, 1, 11, 1023, 2047, 12, 52,
387 1.1.1.3 mrg floatformat_intbit_no,
388 1.1.1.3 mrg "floatformat_ibm_long_double_little",
389 1.1.1.3 mrg floatformat_ibm_long_double_is_valid,
390 1.1.1.3 mrg &floatformat_ieee_double_little
391 1.1.1.3 mrg };
392 1.1 mrg
393 1.1 mrg
395 1.1 mrg #ifndef min
396 1.1 mrg #define min(a, b) ((a) < (b) ? (a) : (b))
397 1.1 mrg #endif
398 1.1 mrg
399 1.1 mrg /* Return 1 if any bits are explicitly set in the mantissa of UFROM,
400 1.1 mrg format FMT, 0 otherwise. */
401 1.1 mrg static int
402 1.1 mrg mant_bits_set (const struct floatformat *fmt, const unsigned char *ufrom)
403 1.1 mrg {
404 1.1 mrg unsigned int mant_bits, mant_off;
405 1.1 mrg int mant_bits_left;
406 1.1 mrg
407 1.1 mrg mant_off = fmt->man_start;
408 1.1 mrg mant_bits_left = fmt->man_len;
409 1.1 mrg while (mant_bits_left > 0)
410 1.1 mrg {
411 1.1 mrg mant_bits = min (mant_bits_left, 32);
412 1.1 mrg
413 1.1 mrg if (get_field (ufrom, fmt->byteorder, fmt->totalsize,
414 1.1 mrg mant_off, mant_bits) != 0)
415 1.1 mrg return 1;
416 1.1 mrg
417 1.1 mrg mant_off += mant_bits;
418 1.1 mrg mant_bits_left -= mant_bits;
419 1.1 mrg }
420 1.1 mrg return 0;
421 1.1 mrg }
422 1.1 mrg
423 1.1 mrg /* Extract a field which starts at START and is LEN bits long. DATA and
424 1.1 mrg TOTAL_LEN are the thing we are extracting it from, in byteorder ORDER. */
425 1.1 mrg static unsigned long
426 1.1 mrg get_field (const unsigned char *data, enum floatformat_byteorders order,
427 1.1 mrg unsigned int total_len, unsigned int start, unsigned int len)
428 1.1 mrg {
429 1.1 mrg unsigned long result = 0;
430 1.1 mrg unsigned int cur_byte;
431 1.1 mrg int lo_bit, hi_bit, cur_bitshift = 0;
432 1.1 mrg int nextbyte = (order == floatformat_little) ? 1 : -1;
433 1.1 mrg
434 1.1 mrg /* Start is in big-endian bit order! Fix that first. */
435 1.1 mrg start = total_len - (start + len);
436 1.1 mrg
437 1.1 mrg /* Start at the least significant part of the field. */
438 1.1 mrg if (order == floatformat_little)
439 1.1 mrg cur_byte = start / FLOATFORMAT_CHAR_BIT;
440 1.1 mrg else
441 1.1 mrg cur_byte = (total_len - start - 1) / FLOATFORMAT_CHAR_BIT;
442 1.1 mrg
443 1.1 mrg lo_bit = start % FLOATFORMAT_CHAR_BIT;
444 1.1 mrg hi_bit = min (lo_bit + len, FLOATFORMAT_CHAR_BIT);
445 1.1 mrg
446 1.1 mrg do
447 1.1 mrg {
448 1.1 mrg unsigned int shifted = *(data + cur_byte) >> lo_bit;
449 1.1 mrg unsigned int bits = hi_bit - lo_bit;
450 1.1 mrg unsigned int mask = (1 << bits) - 1;
451 1.1 mrg result |= (shifted & mask) << cur_bitshift;
452 1.1 mrg len -= bits;
453 1.1 mrg cur_bitshift += bits;
454 1.1 mrg cur_byte += nextbyte;
455 1.1 mrg lo_bit = 0;
456 1.1 mrg hi_bit = min (len, FLOATFORMAT_CHAR_BIT);
457 1.1 mrg }
458 1.1 mrg while (len != 0);
459 1.1 mrg
460 1.1 mrg return result;
461 1.1 mrg }
462 1.1 mrg
463 1.1 mrg /* Convert from FMT to a double.
464 1.1 mrg FROM is the address of the extended float.
465 1.1 mrg Store the double in *TO. */
466 1.1 mrg
467 1.1 mrg void
468 1.1 mrg floatformat_to_double (const struct floatformat *fmt,
469 1.1 mrg const void *from, double *to)
470 1.1 mrg {
471 1.1 mrg const unsigned char *ufrom = (const unsigned char *) from;
472 1.1 mrg double dto;
473 1.1 mrg long exponent;
474 1.1 mrg unsigned long mant;
475 1.1 mrg unsigned int mant_bits, mant_off;
476 1.1 mrg int mant_bits_left;
477 1.1 mrg
478 1.1 mrg /* Split values are not handled specially, since the top half has
479 1.1 mrg the correctly rounded double value (in the only supported case of
480 1.1 mrg split values). */
481 1.1 mrg
482 1.1 mrg exponent = get_field (ufrom, fmt->byteorder, fmt->totalsize,
483 1.1 mrg fmt->exp_start, fmt->exp_len);
484 1.1 mrg
485 1.1 mrg /* If the exponent indicates a NaN, we don't have information to
486 1.1 mrg decide what to do. So we handle it like IEEE, except that we
487 1.1 mrg don't try to preserve the type of NaN. FIXME. */
488 1.1 mrg if ((unsigned long) exponent == fmt->exp_nan)
489 1.1 mrg {
490 1.1 mrg int nan = mant_bits_set (fmt, ufrom);
491 1.1 mrg
492 1.1 mrg /* On certain systems (such as GNU/Linux), the use of the
493 1.1 mrg INFINITY macro below may generate a warning that can not be
494 1.1 mrg silenced due to a bug in GCC (PR preprocessor/11931). The
495 1.1 mrg preprocessor fails to recognise the __extension__ keyword in
496 1.1 mrg conjunction with the GNU/C99 extension for hexadecimal
497 1.1 mrg floating point constants and will issue a warning when
498 1.1 mrg compiling with -pedantic. */
499 1.1 mrg if (nan)
500 1.1 mrg dto = NAN;
501 1.1 mrg else
502 1.1 mrg #ifdef __vax__
503 1.1 mrg dto = HUGE_VAL;
504 1.1 mrg #else
505 1.1 mrg dto = INFINITY;
506 1.1 mrg #endif
507 1.1 mrg
508 1.1 mrg if (get_field (ufrom, fmt->byteorder, fmt->totalsize, fmt->sign_start, 1))
509 1.1 mrg dto = -dto;
510 1.1 mrg
511 1.1 mrg *to = dto;
512 1.1 mrg
513 1.1 mrg return;
514 1.1 mrg }
515 1.1 mrg
516 1.1 mrg mant_bits_left = fmt->man_len;
517 1.1 mrg mant_off = fmt->man_start;
518 1.1 mrg dto = 0.0;
519 1.1 mrg
520 1.1 mrg /* Build the result algebraically. Might go infinite, underflow, etc;
521 1.1 mrg who cares. */
522 1.1.1.2 mrg
523 1.1.1.2 mrg /* For denorms use minimum exponent. */
524 1.1.1.2 mrg if (exponent == 0)
525 1.1.1.2 mrg exponent = 1 - fmt->exp_bias;
526 1.1 mrg else
527 1.1.1.2 mrg {
528 1.1.1.2 mrg exponent -= fmt->exp_bias;
529 1.1.1.2 mrg
530 1.1.1.2 mrg /* If this format uses a hidden bit, explicitly add it in now.
531 1.1.1.2 mrg Otherwise, increment the exponent by one to account for the
532 1.1.1.2 mrg integer bit. */
533 1.1 mrg
534 1.1 mrg if (fmt->intbit == floatformat_intbit_no)
535 1.1 mrg dto = ldexp (1.0, exponent);
536 1.1 mrg else
537 1.1 mrg exponent++;
538 1.1 mrg }
539 1.1 mrg
540 1.1 mrg while (mant_bits_left > 0)
541 1.1 mrg {
542 1.1 mrg mant_bits = min (mant_bits_left, 32);
543 1.1 mrg
544 1.1 mrg mant = get_field (ufrom, fmt->byteorder, fmt->totalsize,
545 1.1 mrg mant_off, mant_bits);
546 1.1.1.2 mrg
547 1.1.1.2 mrg dto += ldexp ((double) mant, exponent - mant_bits);
548 1.1 mrg exponent -= mant_bits;
549 1.1 mrg mant_off += mant_bits;
550 1.1 mrg mant_bits_left -= mant_bits;
551 1.1 mrg }
552 1.1 mrg
553 1.1 mrg /* Negate it if negative. */
554 1.1 mrg if (get_field (ufrom, fmt->byteorder, fmt->totalsize, fmt->sign_start, 1))
555 1.1 mrg dto = -dto;
556 1.1 mrg *to = dto;
557 1.1 mrg }
558 1.1 mrg
559 1.1 mrg static void put_field (unsigned char *, enum floatformat_byteorders,
561 1.1 mrg unsigned int,
562 1.1 mrg unsigned int,
563 1.1 mrg unsigned int,
564 1.1 mrg unsigned long);
565 1.1 mrg
566 1.1 mrg /* Set a field which starts at START and is LEN bits long. DATA and
567 1.1 mrg TOTAL_LEN are the thing we are extracting it from, in byteorder ORDER. */
568 1.1 mrg static void
569 1.1 mrg put_field (unsigned char *data, enum floatformat_byteorders order,
570 1.1 mrg unsigned int total_len, unsigned int start, unsigned int len,
571 1.1 mrg unsigned long stuff_to_put)
572 1.1 mrg {
573 1.1 mrg unsigned int cur_byte;
574 1.1 mrg int lo_bit, hi_bit;
575 1.1 mrg int nextbyte = (order == floatformat_little) ? 1 : -1;
576 1.1 mrg
577 1.1 mrg /* Start is in big-endian bit order! Fix that first. */
578 1.1 mrg start = total_len - (start + len);
579 1.1 mrg
580 1.1 mrg /* Start at the least significant part of the field. */
581 1.1 mrg if (order == floatformat_little)
582 1.1 mrg cur_byte = start / FLOATFORMAT_CHAR_BIT;
583 1.1 mrg else
584 1.1 mrg cur_byte = (total_len - start - 1) / FLOATFORMAT_CHAR_BIT;
585 1.1 mrg
586 1.1 mrg lo_bit = start % FLOATFORMAT_CHAR_BIT;
587 1.1 mrg hi_bit = min (lo_bit + len, FLOATFORMAT_CHAR_BIT);
588 1.1 mrg
589 1.1 mrg do
590 1.1 mrg {
591 1.1 mrg unsigned char *byte_ptr = data + cur_byte;
592 1.1 mrg unsigned int bits = hi_bit - lo_bit;
593 1.1 mrg unsigned int mask = ((1 << bits) - 1) << lo_bit;
594 1.1 mrg *byte_ptr = (*byte_ptr & ~mask) | ((stuff_to_put << lo_bit) & mask);
595 1.1 mrg stuff_to_put >>= bits;
596 1.1 mrg len -= bits;
597 1.1 mrg cur_byte += nextbyte;
598 1.1 mrg lo_bit = 0;
599 1.1 mrg hi_bit = min (len, FLOATFORMAT_CHAR_BIT);
600 1.1 mrg }
601 1.1 mrg while (len != 0);
602 1.1 mrg }
603 1.1 mrg
604 1.1 mrg /* The converse: convert the double *FROM to an extended float
605 1.1 mrg and store where TO points. Neither FROM nor TO have any alignment
606 1.1 mrg restrictions. */
607 1.1 mrg
608 1.1 mrg void
609 1.1 mrg floatformat_from_double (const struct floatformat *fmt,
610 1.1 mrg const double *from, void *to)
611 1.1 mrg {
612 1.1 mrg double dfrom;
613 1.1 mrg int exponent;
614 1.1 mrg double mant;
615 1.1 mrg unsigned int mant_bits, mant_off;
616 1.1 mrg int mant_bits_left;
617 1.1 mrg unsigned char *uto = (unsigned char *) to;
618 1.1 mrg
619 1.1 mrg dfrom = *from;
620 1.1 mrg memset (uto, 0, fmt->totalsize / FLOATFORMAT_CHAR_BIT);
621 1.1 mrg
622 1.1 mrg /* Split values are not handled specially, since a bottom half of
623 1.1 mrg zero is correct for any value representable as double (in the
624 1.1 mrg only supported case of split values). */
625 1.1 mrg
626 1.1 mrg /* If negative, set the sign bit. */
627 1.1 mrg if (dfrom < 0)
628 1.1 mrg {
629 1.1 mrg put_field (uto, fmt->byteorder, fmt->totalsize, fmt->sign_start, 1, 1);
630 1.1 mrg dfrom = -dfrom;
631 1.1 mrg }
632 1.1 mrg
633 1.1 mrg if (dfrom == 0)
634 1.1 mrg {
635 1.1 mrg /* 0.0. */
636 1.1 mrg return;
637 1.1 mrg }
638 1.1 mrg
639 1.1 mrg if (dfrom != dfrom)
640 1.1 mrg {
641 1.1 mrg /* NaN. */
642 1.1 mrg put_field (uto, fmt->byteorder, fmt->totalsize, fmt->exp_start,
643 1.1 mrg fmt->exp_len, fmt->exp_nan);
644 1.1 mrg /* Be sure it's not infinity, but NaN value is irrelevant. */
645 1.1 mrg put_field (uto, fmt->byteorder, fmt->totalsize, fmt->man_start,
646 1.1 mrg 32, 1);
647 1.1 mrg return;
648 1.1 mrg }
649 1.1 mrg
650 1.1 mrg if (dfrom + dfrom == dfrom)
651 1.1 mrg {
652 1.1 mrg /* This can only happen for an infinite value (or zero, which we
653 1.1 mrg already handled above). */
654 1.1 mrg put_field (uto, fmt->byteorder, fmt->totalsize, fmt->exp_start,
655 1.1 mrg fmt->exp_len, fmt->exp_nan);
656 1.1 mrg return;
657 1.1 mrg }
658 1.1 mrg
659 1.1 mrg mant = frexp (dfrom, &exponent);
660 1.1 mrg if (exponent + fmt->exp_bias - 1 > 0)
661 1.1 mrg put_field (uto, fmt->byteorder, fmt->totalsize, fmt->exp_start,
662 1.1 mrg fmt->exp_len, exponent + fmt->exp_bias - 1);
663 1.1 mrg else
664 1.1 mrg {
665 1.1 mrg /* Handle a denormalized number. FIXME: What should we do for
666 1.1 mrg non-IEEE formats? */
667 1.1 mrg put_field (uto, fmt->byteorder, fmt->totalsize, fmt->exp_start,
668 1.1 mrg fmt->exp_len, 0);
669 1.1 mrg mant = ldexp (mant, exponent + fmt->exp_bias - 1);
670 1.1 mrg }
671 1.1 mrg
672 1.1 mrg mant_bits_left = fmt->man_len;
673 1.1 mrg mant_off = fmt->man_start;
674 1.1 mrg while (mant_bits_left > 0)
675 1.1 mrg {
676 1.1 mrg unsigned long mant_long;
677 1.1 mrg mant_bits = mant_bits_left < 32 ? mant_bits_left : 32;
678 1.1 mrg
679 1.1 mrg mant *= 4294967296.0;
680 1.1 mrg mant_long = (unsigned long)mant;
681 1.1 mrg mant -= mant_long;
682 1.1 mrg
683 1.1 mrg /* If the integer bit is implicit, and we are not creating a
684 1.1 mrg denormalized number, then we need to discard it. */
685 1.1 mrg if ((unsigned int) mant_bits_left == fmt->man_len
686 1.1 mrg && fmt->intbit == floatformat_intbit_no
687 1.1 mrg && exponent + fmt->exp_bias - 1 > 0)
688 1.1 mrg {
689 1.1 mrg mant_long &= 0x7fffffff;
690 1.1 mrg mant_bits -= 1;
691 1.1 mrg }
692 1.1 mrg else if (mant_bits < 32)
693 1.1 mrg {
694 1.1 mrg /* The bits we want are in the most significant MANT_BITS bits of
695 1.1 mrg mant_long. Move them to the least significant. */
696 1.1 mrg mant_long >>= 32 - mant_bits;
697 1.1 mrg }
698 1.1 mrg
699 1.1 mrg put_field (uto, fmt->byteorder, fmt->totalsize,
700 1.1 mrg mant_off, mant_bits, mant_long);
701 1.1 mrg mant_off += mant_bits;
702 1.1 mrg mant_bits_left -= mant_bits;
703 1.1 mrg }
704 1.1 mrg }
705 1.1 mrg
706 1.1 mrg /* Return non-zero iff the data at FROM is a valid number in format FMT. */
707 1.1 mrg
708 1.1 mrg int
709 1.1 mrg floatformat_is_valid (const struct floatformat *fmt, const void *from)
710 1.1 mrg {
711 1.1 mrg return fmt->is_valid (fmt, from);
712 1.1 mrg }
713 1.1 mrg
714 1.1 mrg
715 1.1 mrg #ifdef IEEE_DEBUG
716 1.1 mrg
717 1.1 mrg #include <stdio.h>
718 1.1 mrg
719 1.1 mrg /* This is to be run on a host which uses IEEE floating point. */
720 1.1 mrg
721 1.1 mrg void
722 1.1 mrg ieee_test (double n)
723 1.1 mrg {
724 1.1 mrg double result;
725 1.1 mrg
726 1.1 mrg floatformat_to_double (&floatformat_ieee_double_little, &n, &result);
727 1.1 mrg if ((n != result && (! isnan (n) || ! isnan (result)))
728 1.1 mrg || (n < 0 && result >= 0)
729 1.1 mrg || (n >= 0 && result < 0))
730 1.1 mrg printf ("Differ(to): %.20g -> %.20g\n", n, result);
731 1.1 mrg
732 1.1 mrg floatformat_from_double (&floatformat_ieee_double_little, &n, &result);
733 1.1 mrg if ((n != result && (! isnan (n) || ! isnan (result)))
734 1.1 mrg || (n < 0 && result >= 0)
735 1.1 mrg || (n >= 0 && result < 0))
736 1.1 mrg printf ("Differ(from): %.20g -> %.20g\n", n, result);
737 1.1 mrg
738 1.1 mrg #if 0
739 1.1 mrg {
740 1.1 mrg char exten[16];
741 1.1 mrg
742 1.1 mrg floatformat_from_double (&floatformat_m68881_ext, &n, exten);
743 1.1 mrg floatformat_to_double (&floatformat_m68881_ext, exten, &result);
744 1.1 mrg if (n != result)
745 1.1 mrg printf ("Differ(to+from): %.20g -> %.20g\n", n, result);
746 1.1 mrg }
747 1.1 mrg #endif
748 1.1 mrg
749 1.1 mrg #if IEEE_DEBUG > 1
750 1.1 mrg /* This is to be run on a host which uses 68881 format. */
751 1.1 mrg {
752 1.1 mrg long double ex = *(long double *)exten;
753 1.1 mrg if (ex != n)
754 1.1 mrg printf ("Differ(from vs. extended): %.20g\n", n);
755 1.1 mrg }
756 1.1 mrg #endif
757 1.1 mrg }
758 1.1 mrg
759 1.1 mrg int
760 1.1 mrg main (void)
761 1.1 mrg {
762 1.1.1.2 mrg ieee_test (0.0);
763 1.1 mrg ieee_test (0.5);
764 1.1 mrg ieee_test (1.1);
765 1.1 mrg ieee_test (256.0);
766 1.1 mrg ieee_test (0.12345);
767 1.1 mrg ieee_test (234235.78907234);
768 1.1 mrg ieee_test (-512.0);
769 1.1 mrg ieee_test (-0.004321);
770 1.1 mrg ieee_test (1.2E-70);
771 1.1 mrg ieee_test (1.2E-316);
772 1.1 mrg ieee_test (4.9406564584124654E-324);
773 1.1 mrg ieee_test (- 4.9406564584124654E-324);
774 1.1 mrg ieee_test (- 0.0);
775 1.1 mrg ieee_test (- INFINITY);
776 1.1 mrg ieee_test (- NAN);
777 1.1 mrg ieee_test (INFINITY);
778 1.1 mrg ieee_test (NAN);
779 1.1 mrg return 0;
780 }
781 #endif
782