2003-03-11 Aldy Hernandez <aldyh@redhat.com>
[official-gcc.git] / libiberty / floatformat.c
blobd9e9fad816de0c65b58bc1afffba710fd20920ab
1 /* IEEE floating point support routines, for GDB, the GNU Debugger.
2 Copyright (C) 1991, 1994, 1999, 2000 Free Software Foundation, Inc.
4 This file is part of GDB.
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.
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.
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. */
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
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
36 /* floatformats for IEEE single and double, big and little endian. */
37 const struct floatformat floatformat_ieee_single_big =
39 floatformat_big, 32, 0, 1, 8, 127, 255, 9, 23,
40 floatformat_intbit_no,
41 "floatformat_ieee_single_big"
43 const struct floatformat floatformat_ieee_single_little =
45 floatformat_little, 32, 0, 1, 8, 127, 255, 9, 23,
46 floatformat_intbit_no,
47 "floatformat_ieee_single_little"
49 const struct floatformat floatformat_ieee_double_big =
51 floatformat_big, 64, 0, 1, 11, 1023, 2047, 12, 52,
52 floatformat_intbit_no,
53 "floatformat_ieee_double_big"
55 const struct floatformat floatformat_ieee_double_little =
57 floatformat_little, 64, 0, 1, 11, 1023, 2047, 12, 52,
58 floatformat_intbit_no,
59 "floatformat_ieee_double_little"
62 /* floatformat for IEEE double, little endian byte order, with big endian word
63 ordering, as on the ARM. */
65 const struct floatformat floatformat_ieee_double_littlebyte_bigword =
67 floatformat_littlebyte_bigword, 64, 0, 1, 11, 1023, 2047, 12, 52,
68 floatformat_intbit_no,
69 "floatformat_ieee_double_littlebyte_bigword"
72 const struct floatformat floatformat_i387_ext =
74 floatformat_little, 80, 0, 1, 15, 0x3fff, 0x7fff, 16, 64,
75 floatformat_intbit_yes,
76 "floatformat_i387_ext"
78 const struct floatformat floatformat_m68881_ext =
80 /* Note that the bits from 16 to 31 are unused. */
81 floatformat_big, 96, 0, 1, 15, 0x3fff, 0x7fff, 32, 64,
82 floatformat_intbit_yes,
83 "floatformat_m68881_ext"
85 const struct floatformat floatformat_i960_ext =
87 /* Note that the bits from 0 to 15 are unused. */
88 floatformat_little, 96, 16, 17, 15, 0x3fff, 0x7fff, 32, 64,
89 floatformat_intbit_yes,
90 "floatformat_i960_ext"
92 const struct floatformat floatformat_m88110_ext =
94 floatformat_big, 80, 0, 1, 15, 0x3fff, 0x7fff, 16, 64,
95 floatformat_intbit_yes,
96 "floatformat_m88110_ext"
98 const struct floatformat floatformat_m88110_harris_ext =
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,
103 floatformat_intbit_no,
104 "floatformat_m88110_ext_harris"
106 const struct floatformat floatformat_arm_ext_big =
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"
113 const struct floatformat floatformat_arm_ext_littlebyte_bigword =
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"
120 const struct floatformat floatformat_ia64_spill_big =
122 floatformat_big, 128, 0, 1, 17, 65535, 0x1ffff, 18, 64,
123 floatformat_intbit_yes,
124 "floatformat_ia64_spill_big"
126 const struct floatformat floatformat_ia64_spill_little =
128 floatformat_little, 128, 0, 1, 17, 65535, 0x1ffff, 18, 64,
129 floatformat_intbit_yes,
130 "floatformat_ia64_spill_little"
132 const struct floatformat floatformat_ia64_quad_big =
134 floatformat_big, 128, 0, 1, 15, 16383, 0x7fff, 16, 112,
135 floatformat_intbit_no,
136 "floatformat_ia64_quad_big"
138 const struct floatformat floatformat_ia64_quad_little =
140 floatformat_little, 128, 0, 1, 15, 16383, 0x7fff, 16, 112,
141 floatformat_intbit_no,
142 "floatformat_ia64_quad_little"
145 static unsigned long get_field PARAMS ((unsigned char *,
146 enum floatformat_byteorders,
147 unsigned int,
148 unsigned int,
149 unsigned int));
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;
161 unsigned long result;
162 unsigned int cur_byte;
163 int cur_bitshift;
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;
178 /* Move towards the most significant part of the field. */
179 while ((unsigned int) cur_bitshift < len)
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;
195 return result;
198 #ifndef min
199 #define min(a, b) ((a) < (b) ? (a) : (b))
200 #endif
202 /* Convert from FMT to a double.
203 FROM is the address of the extended float.
204 Store the double in *TO. */
206 void
207 floatformat_to_double (fmt, from, to)
208 const struct floatformat *fmt;
209 char *from;
210 double *to;
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 */
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. */
226 mant_bits_left = fmt->man_len;
227 mant_off = fmt->man_start;
228 dto = 0.0;
230 special_exponent = exponent == 0 || (unsigned long) exponent == fmt->exp_nan;
232 /* Don't bias zero's, denorms or NaNs. */
233 if (!special_exponent)
234 exponent -= fmt->exp_bias;
236 /* Build the result algebraically. Might go infinite, underflow, etc;
237 who cares. */
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. */
242 if (!special_exponent)
244 if (fmt->intbit == floatformat_intbit_no)
245 dto = ldexp (1.0, exponent);
246 else
247 exponent++;
250 while (mant_bits_left > 0)
252 mant_bits = min (mant_bits_left, 32);
254 mant = get_field (ufrom, fmt->byteorder, fmt->totalsize,
255 mant_off, mant_bits);
257 dto += ldexp ((double)mant, exponent - mant_bits);
258 exponent -= mant_bits;
259 mant_off += mant_bits;
260 mant_bits_left -= mant_bits;
263 /* Negate it if negative. */
264 if (get_field (ufrom, fmt->byteorder, fmt->totalsize, fmt->sign_start, 1))
265 dto = -dto;
266 *to = dto;
269 static void put_field PARAMS ((unsigned char *, enum floatformat_byteorders,
270 unsigned int,
271 unsigned int,
272 unsigned int,
273 unsigned long));
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;
286 unsigned int cur_byte;
287 int cur_bitshift;
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;
305 /* Move towards the most significant part of the field. */
306 while ((unsigned int) cur_bitshift < len)
308 if (len - cur_bitshift < FLOATFORMAT_CHAR_BIT)
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);
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;
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. */
330 void
331 floatformat_from_double (fmt, from, to)
332 const struct floatformat *fmt;
333 double *from;
334 char *to;
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;
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)
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;
358 /* If negative, set the sign bit. */
359 if (dfrom < 0)
361 put_field (uto, fmt->byteorder, fmt->totalsize, fmt->sign_start, 1, 1);
362 dfrom = -dfrom;
365 /* How to tell an infinity from an ordinary number? FIXME-someday */
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);
371 mant_bits_left = fmt->man_len;
372 mant_off = fmt->man_start;
373 while (mant_bits_left > 0)
375 unsigned long mant_long;
376 mant_bits = mant_bits_left < 32 ? mant_bits_left : 32;
378 mant *= 4294967296.0;
379 mant_long = (unsigned long)mant;
380 mant -= mant_long;
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). */
386 if ((unsigned int) mant_bits_left == fmt->man_len
387 && fmt->intbit == floatformat_intbit_no)
389 mant_long &= 0x7fffffff;
390 mant_bits -= 1;
392 else if (mant_bits < 32)
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;
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;
407 #ifdef IEEE_DEBUG
409 /* This is to be run on a host which uses IEEE floating point. */
411 void
412 ieee_test (n)
413 double n;
415 double result;
416 char exten[16];
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);
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);
430 #if IEEE_DEBUG > 1
431 /* This is to be run on a host which uses 68881 format. */
433 long double ex = *(long double *)exten;
434 if (ex != n)
435 printf ("Differ(from vs. extended): %.20g\n", n);
437 #endif
441 main ()
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;
451 #endif