| 1 | /* IEEE floating point support routines, for GDB, the GNU Debugger. |
| 2 | Copyright 1991, 1994, 1999, 2000, 2003, 2005, 2006 |
| 3 | Free Software Foundation, Inc. |
| 4 | |
| 5 | This file is part of GDB. |
| 6 | |
| 7 | This program is free software; you can redistribute it and/or modify |
| 8 | it under the terms of the GNU General Public License as published by |
| 9 | the Free Software Foundation; either version 2 of the License, or |
| 10 | (at your option) any later version. |
| 11 | |
| 12 | This program is distributed in the hope that it will be useful, |
| 13 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 14 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 15 | GNU General Public License for more details. |
| 16 | |
| 17 | You should have received a copy of the GNU General Public License |
| 18 | along with this program; if not, write to the Free Software |
| 19 | Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston, MA 02110-1301, USA. */ |
| 20 | |
| 21 | /* This is needed to pick up the NAN macro on some systems. */ |
| 22 | #define _GNU_SOURCE |
| 23 | |
| 24 | #ifdef HAVE_CONFIG_H |
| 25 | #include "config.h" |
| 26 | #endif |
| 27 | |
| 28 | #include <math.h> |
| 29 | |
| 30 | #ifdef HAVE_STRING_H |
| 31 | #include <string.h> |
| 32 | #endif |
| 33 | |
| 34 | /* On some platforms, <float.h> provides DBL_QNAN. */ |
| 35 | #ifdef STDC_HEADERS |
| 36 | #include <float.h> |
| 37 | #endif |
| 38 | |
| 39 | #include "ansidecl.h" |
| 40 | #include "libiberty.h" |
| 41 | #include "floatformat.h" |
| 42 | |
| 43 | #ifndef INFINITY |
| 44 | #ifdef HUGE_VAL |
| 45 | #define INFINITY HUGE_VAL |
| 46 | #else |
| 47 | #define INFINITY (1.0 / 0.0) |
| 48 | #endif |
| 49 | #endif |
| 50 | |
| 51 | #ifndef NAN |
| 52 | #ifdef DBL_QNAN |
| 53 | #define NAN DBL_QNAN |
| 54 | #else |
| 55 | #define NAN (0.0 / 0.0) |
| 56 | #endif |
| 57 | #endif |
| 58 | |
| 59 | static int mant_bits_set (const struct floatformat *, const unsigned char *); |
| 60 | static unsigned long get_field (const unsigned char *, |
| 61 | enum floatformat_byteorders, |
| 62 | unsigned int, |
| 63 | unsigned int, |
| 64 | unsigned int); |
| 65 | static int floatformat_always_valid (const struct floatformat *fmt, |
| 66 | const void *from); |
| 67 | |
| 68 | static int |
| 69 | floatformat_always_valid (const struct floatformat *fmt ATTRIBUTE_UNUSED, |
| 70 | const void *from ATTRIBUTE_UNUSED) |
| 71 | { |
| 72 | return 1; |
| 73 | } |
| 74 | |
| 75 | /* The odds that CHAR_BIT will be anything but 8 are low enough that I'm not |
| 76 | going to bother with trying to muck around with whether it is defined in |
| 77 | a system header, what we do if not, etc. */ |
| 78 | #define FLOATFORMAT_CHAR_BIT 8 |
| 79 | |
| 80 | /* floatformats for IEEE single and double, big and little endian. */ |
| 81 | const struct floatformat floatformat_ieee_single_big = |
| 82 | { |
| 83 | floatformat_big, 32, 0, 1, 8, 127, 255, 9, 23, |
| 84 | floatformat_intbit_no, |
| 85 | "floatformat_ieee_single_big", |
| 86 | floatformat_always_valid, |
| 87 | NULL |
| 88 | }; |
| 89 | const struct floatformat floatformat_ieee_single_little = |
| 90 | { |
| 91 | floatformat_little, 32, 0, 1, 8, 127, 255, 9, 23, |
| 92 | floatformat_intbit_no, |
| 93 | "floatformat_ieee_single_little", |
| 94 | floatformat_always_valid, |
| 95 | NULL |
| 96 | }; |
| 97 | const struct floatformat floatformat_ieee_double_big = |
| 98 | { |
| 99 | floatformat_big, 64, 0, 1, 11, 1023, 2047, 12, 52, |
| 100 | floatformat_intbit_no, |
| 101 | "floatformat_ieee_double_big", |
| 102 | floatformat_always_valid, |
| 103 | NULL |
| 104 | }; |
| 105 | const struct floatformat floatformat_ieee_double_little = |
| 106 | { |
| 107 | floatformat_little, 64, 0, 1, 11, 1023, 2047, 12, 52, |
| 108 | floatformat_intbit_no, |
| 109 | "floatformat_ieee_double_little", |
| 110 | floatformat_always_valid, |
| 111 | NULL |
| 112 | }; |
| 113 | |
| 114 | /* floatformat for IEEE double, little endian byte order, with big endian word |
| 115 | ordering, as on the ARM. */ |
| 116 | |
| 117 | const struct floatformat floatformat_ieee_double_littlebyte_bigword = |
| 118 | { |
| 119 | floatformat_littlebyte_bigword, 64, 0, 1, 11, 1023, 2047, 12, 52, |
| 120 | floatformat_intbit_no, |
| 121 | "floatformat_ieee_double_littlebyte_bigword", |
| 122 | floatformat_always_valid, |
| 123 | NULL |
| 124 | }; |
| 125 | |
| 126 | /* floatformat for VAX. Not quite IEEE, but close enough. */ |
| 127 | |
| 128 | const struct floatformat floatformat_vax_f = |
| 129 | { |
| 130 | floatformat_vax, 32, 0, 1, 8, 129, 0, 9, 23, |
| 131 | floatformat_intbit_no, |
| 132 | "floatformat_vax_f", |
| 133 | floatformat_always_valid, |
| 134 | NULL |
| 135 | }; |
| 136 | const struct floatformat floatformat_vax_d = |
| 137 | { |
| 138 | floatformat_vax, 64, 0, 1, 8, 129, 0, 9, 55, |
| 139 | floatformat_intbit_no, |
| 140 | "floatformat_vax_d", |
| 141 | floatformat_always_valid, |
| 142 | NULL |
| 143 | }; |
| 144 | const struct floatformat floatformat_vax_g = |
| 145 | { |
| 146 | floatformat_vax, 64, 0, 1, 11, 1025, 0, 12, 52, |
| 147 | floatformat_intbit_no, |
| 148 | "floatformat_vax_g", |
| 149 | floatformat_always_valid, |
| 150 | NULL |
| 151 | }; |
| 152 | |
| 153 | static int floatformat_i387_ext_is_valid (const struct floatformat *fmt, |
| 154 | const void *from); |
| 155 | |
| 156 | static int |
| 157 | floatformat_i387_ext_is_valid (const struct floatformat *fmt, const void *from) |
| 158 | { |
| 159 | /* In the i387 double-extended format, if the exponent is all ones, |
| 160 | then the integer bit must be set. If the exponent is neither 0 |
| 161 | nor ~0, the intbit must also be set. Only if the exponent is |
| 162 | zero can it be zero, and then it must be zero. */ |
| 163 | unsigned long exponent, int_bit; |
| 164 | const unsigned char *ufrom = (const unsigned char *) from; |
| 165 | |
| 166 | exponent = get_field (ufrom, fmt->byteorder, fmt->totalsize, |
| 167 | fmt->exp_start, fmt->exp_len); |
| 168 | int_bit = get_field (ufrom, fmt->byteorder, fmt->totalsize, |
| 169 | fmt->man_start, 1); |
| 170 | |
| 171 | if ((exponent == 0) != (int_bit == 0)) |
| 172 | return 0; |
| 173 | else |
| 174 | return 1; |
| 175 | } |
| 176 | |
| 177 | const struct floatformat floatformat_i387_ext = |
| 178 | { |
| 179 | floatformat_little, 80, 0, 1, 15, 0x3fff, 0x7fff, 16, 64, |
| 180 | floatformat_intbit_yes, |
| 181 | "floatformat_i387_ext", |
| 182 | floatformat_i387_ext_is_valid, |
| 183 | NULL |
| 184 | }; |
| 185 | const struct floatformat floatformat_m68881_ext = |
| 186 | { |
| 187 | /* Note that the bits from 16 to 31 are unused. */ |
| 188 | floatformat_big, 96, 0, 1, 15, 0x3fff, 0x7fff, 32, 64, |
| 189 | floatformat_intbit_yes, |
| 190 | "floatformat_m68881_ext", |
| 191 | floatformat_always_valid, |
| 192 | NULL |
| 193 | }; |
| 194 | const struct floatformat floatformat_i960_ext = |
| 195 | { |
| 196 | /* Note that the bits from 0 to 15 are unused. */ |
| 197 | floatformat_little, 96, 16, 17, 15, 0x3fff, 0x7fff, 32, 64, |
| 198 | floatformat_intbit_yes, |
| 199 | "floatformat_i960_ext", |
| 200 | floatformat_always_valid, |
| 201 | NULL |
| 202 | }; |
| 203 | const struct floatformat floatformat_m88110_ext = |
| 204 | { |
| 205 | floatformat_big, 80, 0, 1, 15, 0x3fff, 0x7fff, 16, 64, |
| 206 | floatformat_intbit_yes, |
| 207 | "floatformat_m88110_ext", |
| 208 | floatformat_always_valid, |
| 209 | NULL |
| 210 | }; |
| 211 | const struct floatformat floatformat_m88110_harris_ext = |
| 212 | { |
| 213 | /* Harris uses raw format 128 bytes long, but the number is just an ieee |
| 214 | double, and the last 64 bits are wasted. */ |
| 215 | floatformat_big,128, 0, 1, 11, 0x3ff, 0x7ff, 12, 52, |
| 216 | floatformat_intbit_no, |
| 217 | "floatformat_m88110_ext_harris", |
| 218 | floatformat_always_valid, |
| 219 | NULL |
| 220 | }; |
| 221 | const struct floatformat floatformat_arm_ext_big = |
| 222 | { |
| 223 | /* Bits 1 to 16 are unused. */ |
| 224 | floatformat_big, 96, 0, 17, 15, 0x3fff, 0x7fff, 32, 64, |
| 225 | floatformat_intbit_yes, |
| 226 | "floatformat_arm_ext_big", |
| 227 | floatformat_always_valid, |
| 228 | NULL |
| 229 | }; |
| 230 | const struct floatformat floatformat_arm_ext_littlebyte_bigword = |
| 231 | { |
| 232 | /* Bits 1 to 16 are unused. */ |
| 233 | floatformat_littlebyte_bigword, 96, 0, 17, 15, 0x3fff, 0x7fff, 32, 64, |
| 234 | floatformat_intbit_yes, |
| 235 | "floatformat_arm_ext_littlebyte_bigword", |
| 236 | floatformat_always_valid, |
| 237 | NULL |
| 238 | }; |
| 239 | const struct floatformat floatformat_ia64_spill_big = |
| 240 | { |
| 241 | floatformat_big, 128, 0, 1, 17, 65535, 0x1ffff, 18, 64, |
| 242 | floatformat_intbit_yes, |
| 243 | "floatformat_ia64_spill_big", |
| 244 | floatformat_always_valid, |
| 245 | NULL |
| 246 | }; |
| 247 | const struct floatformat floatformat_ia64_spill_little = |
| 248 | { |
| 249 | floatformat_little, 128, 0, 1, 17, 65535, 0x1ffff, 18, 64, |
| 250 | floatformat_intbit_yes, |
| 251 | "floatformat_ia64_spill_little", |
| 252 | floatformat_always_valid, |
| 253 | NULL |
| 254 | }; |
| 255 | const struct floatformat floatformat_ia64_quad_big = |
| 256 | { |
| 257 | floatformat_big, 128, 0, 1, 15, 16383, 0x7fff, 16, 112, |
| 258 | floatformat_intbit_no, |
| 259 | "floatformat_ia64_quad_big", |
| 260 | floatformat_always_valid, |
| 261 | NULL |
| 262 | }; |
| 263 | const struct floatformat floatformat_ia64_quad_little = |
| 264 | { |
| 265 | floatformat_little, 128, 0, 1, 15, 16383, 0x7fff, 16, 112, |
| 266 | floatformat_intbit_no, |
| 267 | "floatformat_ia64_quad_little", |
| 268 | floatformat_always_valid, |
| 269 | NULL |
| 270 | }; |
| 271 | |
| 272 | static int |
| 273 | floatformat_ibm_long_double_is_valid (const struct floatformat *fmt, |
| 274 | const void *from) |
| 275 | { |
| 276 | const unsigned char *ufrom = (const unsigned char *) from; |
| 277 | const struct floatformat *hfmt = fmt->split_half; |
| 278 | long top_exp, bot_exp; |
| 279 | int top_nan = 0; |
| 280 | |
| 281 | top_exp = get_field (ufrom, hfmt->byteorder, hfmt->totalsize, |
| 282 | hfmt->exp_start, hfmt->exp_len); |
| 283 | bot_exp = get_field (ufrom + 8, hfmt->byteorder, hfmt->totalsize, |
| 284 | hfmt->exp_start, hfmt->exp_len); |
| 285 | |
| 286 | if ((unsigned long) top_exp == hfmt->exp_nan) |
| 287 | top_nan = mant_bits_set (hfmt, ufrom); |
| 288 | |
| 289 | /* A NaN is valid with any low part. */ |
| 290 | if (top_nan) |
| 291 | return 1; |
| 292 | |
| 293 | /* An infinity, zero or denormal requires low part 0 (positive or |
| 294 | negative). */ |
| 295 | if ((unsigned long) top_exp == hfmt->exp_nan || top_exp == 0) |
| 296 | { |
| 297 | if (bot_exp != 0) |
| 298 | return 0; |
| 299 | |
| 300 | return !mant_bits_set (hfmt, ufrom + 8); |
| 301 | } |
| 302 | |
| 303 | /* The top part is now a finite normal value. The long double value |
| 304 | is the sum of the two parts, and the top part must equal the |
| 305 | result of rounding the long double value to nearest double. Thus |
| 306 | the bottom part must be <= 0.5ulp of the top part in absolute |
| 307 | value, and if it is < 0.5ulp then the long double is definitely |
| 308 | valid. */ |
| 309 | if (bot_exp < top_exp - 53) |
| 310 | return 1; |
| 311 | if (bot_exp > top_exp - 53 && bot_exp != 0) |
| 312 | return 0; |
| 313 | if (bot_exp == 0) |
| 314 | { |
| 315 | /* The bottom part is 0 or denormal. Determine which, and if |
| 316 | denormal the first two set bits. */ |
| 317 | int first_bit = -1, second_bit = -1, cur_bit; |
| 318 | for (cur_bit = 0; (unsigned int) cur_bit < hfmt->man_len; cur_bit++) |
| 319 | if (get_field (ufrom + 8, hfmt->byteorder, hfmt->totalsize, |
| 320 | hfmt->man_start + cur_bit, 1)) |
| 321 | { |
| 322 | if (first_bit == -1) |
| 323 | first_bit = cur_bit; |
| 324 | else |
| 325 | { |
| 326 | second_bit = cur_bit; |
| 327 | break; |
| 328 | } |
| 329 | } |
| 330 | /* Bottom part 0 is OK. */ |
| 331 | if (first_bit == -1) |
| 332 | return 1; |
| 333 | /* The real exponent of the bottom part is -first_bit. */ |
| 334 | if (-first_bit < top_exp - 53) |
| 335 | return 1; |
| 336 | if (-first_bit > top_exp - 53) |
| 337 | return 0; |
| 338 | /* The bottom part is at least 0.5ulp of the top part. For this |
| 339 | to be OK, the bottom part must be exactly 0.5ulp (i.e. no |
| 340 | more bits set) and the top part must have last bit 0. */ |
| 341 | if (second_bit != -1) |
| 342 | return 0; |
| 343 | return !get_field (ufrom, hfmt->byteorder, hfmt->totalsize, |
| 344 | hfmt->man_start + hfmt->man_len - 1, 1); |
| 345 | } |
| 346 | else |
| 347 | { |
| 348 | /* The bottom part is at least 0.5ulp of the top part. For this |
| 349 | to be OK, it must be exactly 0.5ulp (i.e. no explicit bits |
| 350 | set) and the top part must have last bit 0. */ |
| 351 | if (get_field (ufrom, hfmt->byteorder, hfmt->totalsize, |
| 352 | hfmt->man_start + hfmt->man_len - 1, 1)) |
| 353 | return 0; |
| 354 | return !mant_bits_set (hfmt, ufrom + 8); |
| 355 | } |
| 356 | } |
| 357 | |
| 358 | const struct floatformat floatformat_ibm_long_double = |
| 359 | { |
| 360 | floatformat_big, 128, 0, 1, 11, 1023, 2047, 12, 52, |
| 361 | floatformat_intbit_no, |
| 362 | "floatformat_ibm_long_double", |
| 363 | floatformat_ibm_long_double_is_valid, |
| 364 | &floatformat_ieee_double_big |
| 365 | }; |
| 366 | \f |
| 367 | |
| 368 | #ifndef min |
| 369 | #define min(a, b) ((a) < (b) ? (a) : (b)) |
| 370 | #endif |
| 371 | |
| 372 | /* Return 1 if any bits are explicitly set in the mantissa of UFROM, |
| 373 | format FMT, 0 otherwise. */ |
| 374 | static int |
| 375 | mant_bits_set (const struct floatformat *fmt, const unsigned char *ufrom) |
| 376 | { |
| 377 | unsigned int mant_bits, mant_off; |
| 378 | int mant_bits_left; |
| 379 | |
| 380 | mant_off = fmt->man_start; |
| 381 | mant_bits_left = fmt->man_len; |
| 382 | while (mant_bits_left > 0) |
| 383 | { |
| 384 | mant_bits = min (mant_bits_left, 32); |
| 385 | |
| 386 | if (get_field (ufrom, fmt->byteorder, fmt->totalsize, |
| 387 | mant_off, mant_bits) != 0) |
| 388 | return 1; |
| 389 | |
| 390 | mant_off += mant_bits; |
| 391 | mant_bits_left -= mant_bits; |
| 392 | } |
| 393 | return 0; |
| 394 | } |
| 395 | |
| 396 | /* Extract a field which starts at START and is LEN bits long. DATA and |
| 397 | TOTAL_LEN are the thing we are extracting it from, in byteorder ORDER. */ |
| 398 | static unsigned long |
| 399 | get_field (const unsigned char *data, enum floatformat_byteorders order, |
| 400 | unsigned int total_len, unsigned int start, unsigned int len) |
| 401 | { |
| 402 | unsigned long result = 0; |
| 403 | unsigned int cur_byte; |
| 404 | int lo_bit, hi_bit, cur_bitshift = 0; |
| 405 | int nextbyte = (order == floatformat_little) ? 1 : -1; |
| 406 | |
| 407 | /* Start is in big-endian bit order! Fix that first. */ |
| 408 | start = total_len - (start + len); |
| 409 | |
| 410 | /* Start at the least significant part of the field. */ |
| 411 | if (order == floatformat_little) |
| 412 | cur_byte = start / FLOATFORMAT_CHAR_BIT; |
| 413 | else |
| 414 | cur_byte = (total_len - start - 1) / FLOATFORMAT_CHAR_BIT; |
| 415 | |
| 416 | lo_bit = start % FLOATFORMAT_CHAR_BIT; |
| 417 | hi_bit = min (lo_bit + len, FLOATFORMAT_CHAR_BIT); |
| 418 | |
| 419 | do |
| 420 | { |
| 421 | unsigned int shifted = *(data + cur_byte) >> lo_bit; |
| 422 | unsigned int bits = hi_bit - lo_bit; |
| 423 | unsigned int mask = (1 << bits) - 1; |
| 424 | result |= (shifted & mask) << cur_bitshift; |
| 425 | len -= bits; |
| 426 | cur_bitshift += bits; |
| 427 | cur_byte += nextbyte; |
| 428 | lo_bit = 0; |
| 429 | hi_bit = min (len, FLOATFORMAT_CHAR_BIT); |
| 430 | } |
| 431 | while (len != 0); |
| 432 | |
| 433 | return result; |
| 434 | } |
| 435 | |
| 436 | /* Convert from FMT to a double. |
| 437 | FROM is the address of the extended float. |
| 438 | Store the double in *TO. */ |
| 439 | |
| 440 | void |
| 441 | floatformat_to_double (const struct floatformat *fmt, |
| 442 | const void *from, double *to) |
| 443 | { |
| 444 | const unsigned char *ufrom = (const unsigned char *) from; |
| 445 | double dto; |
| 446 | long exponent; |
| 447 | unsigned long mant; |
| 448 | unsigned int mant_bits, mant_off; |
| 449 | int mant_bits_left; |
| 450 | int special_exponent; /* It's a NaN, denorm or zero */ |
| 451 | |
| 452 | /* Split values are not handled specially, since the top half has |
| 453 | the correctly rounded double value (in the only supported case of |
| 454 | split values). */ |
| 455 | |
| 456 | exponent = get_field (ufrom, fmt->byteorder, fmt->totalsize, |
| 457 | fmt->exp_start, fmt->exp_len); |
| 458 | |
| 459 | /* If the exponent indicates a NaN, we don't have information to |
| 460 | decide what to do. So we handle it like IEEE, except that we |
| 461 | don't try to preserve the type of NaN. FIXME. */ |
| 462 | if ((unsigned long) exponent == fmt->exp_nan) |
| 463 | { |
| 464 | int nan = mant_bits_set (fmt, ufrom); |
| 465 | |
| 466 | /* On certain systems (such as GNU/Linux), the use of the |
| 467 | INFINITY macro below may generate a warning that can not be |
| 468 | silenced due to a bug in GCC (PR preprocessor/11931). The |
| 469 | preprocessor fails to recognise the __extension__ keyword in |
| 470 | conjunction with the GNU/C99 extension for hexadecimal |
| 471 | floating point constants and will issue a warning when |
| 472 | compiling with -pedantic. */ |
| 473 | if (nan) |
| 474 | dto = NAN; |
| 475 | else |
| 476 | dto = INFINITY; |
| 477 | |
| 478 | if (get_field (ufrom, fmt->byteorder, fmt->totalsize, fmt->sign_start, 1)) |
| 479 | dto = -dto; |
| 480 | |
| 481 | *to = dto; |
| 482 | |
| 483 | return; |
| 484 | } |
| 485 | |
| 486 | mant_bits_left = fmt->man_len; |
| 487 | mant_off = fmt->man_start; |
| 488 | dto = 0.0; |
| 489 | |
| 490 | special_exponent = exponent == 0 || (unsigned long) exponent == fmt->exp_nan; |
| 491 | |
| 492 | /* Don't bias zero's, denorms or NaNs. */ |
| 493 | if (!special_exponent) |
| 494 | exponent -= fmt->exp_bias; |
| 495 | |
| 496 | /* Build the result algebraically. Might go infinite, underflow, etc; |
| 497 | who cares. */ |
| 498 | |
| 499 | /* If this format uses a hidden bit, explicitly add it in now. Otherwise, |
| 500 | increment the exponent by one to account for the integer bit. */ |
| 501 | |
| 502 | if (!special_exponent) |
| 503 | { |
| 504 | if (fmt->intbit == floatformat_intbit_no) |
| 505 | dto = ldexp (1.0, exponent); |
| 506 | else |
| 507 | exponent++; |
| 508 | } |
| 509 | |
| 510 | while (mant_bits_left > 0) |
| 511 | { |
| 512 | mant_bits = min (mant_bits_left, 32); |
| 513 | |
| 514 | mant = get_field (ufrom, fmt->byteorder, fmt->totalsize, |
| 515 | mant_off, mant_bits); |
| 516 | |
| 517 | /* Handle denormalized numbers. FIXME: What should we do for |
| 518 | non-IEEE formats? */ |
| 519 | if (special_exponent && exponent == 0 && mant != 0) |
| 520 | dto += ldexp ((double)mant, |
| 521 | (- fmt->exp_bias |
| 522 | - mant_bits |
| 523 | - (mant_off - fmt->man_start) |
| 524 | + 1)); |
| 525 | else |
| 526 | dto += ldexp ((double)mant, exponent - mant_bits); |
| 527 | if (exponent != 0) |
| 528 | exponent -= mant_bits; |
| 529 | mant_off += mant_bits; |
| 530 | mant_bits_left -= mant_bits; |
| 531 | } |
| 532 | |
| 533 | /* Negate it if negative. */ |
| 534 | if (get_field (ufrom, fmt->byteorder, fmt->totalsize, fmt->sign_start, 1)) |
| 535 | dto = -dto; |
| 536 | *to = dto; |
| 537 | } |
| 538 | \f |
| 539 | static void put_field (unsigned char *, enum floatformat_byteorders, |
| 540 | unsigned int, |
| 541 | unsigned int, |
| 542 | unsigned int, |
| 543 | unsigned long); |
| 544 | |
| 545 | /* Set a field which starts at START and is LEN bits long. DATA and |
| 546 | TOTAL_LEN are the thing we are extracting it from, in byteorder ORDER. */ |
| 547 | static void |
| 548 | put_field (unsigned char *data, enum floatformat_byteorders order, |
| 549 | unsigned int total_len, unsigned int start, unsigned int len, |
| 550 | unsigned long stuff_to_put) |
| 551 | { |
| 552 | unsigned int cur_byte; |
| 553 | int lo_bit, hi_bit; |
| 554 | int nextbyte = (order == floatformat_little) ? 1 : -1; |
| 555 | |
| 556 | /* Start is in big-endian bit order! Fix that first. */ |
| 557 | start = total_len - (start + len); |
| 558 | |
| 559 | /* Start at the least significant part of the field. */ |
| 560 | if (order == floatformat_little) |
| 561 | cur_byte = start / FLOATFORMAT_CHAR_BIT; |
| 562 | else |
| 563 | cur_byte = (total_len - start - 1) / FLOATFORMAT_CHAR_BIT; |
| 564 | |
| 565 | lo_bit = start % FLOATFORMAT_CHAR_BIT; |
| 566 | hi_bit = min (lo_bit + len, FLOATFORMAT_CHAR_BIT); |
| 567 | |
| 568 | do |
| 569 | { |
| 570 | unsigned char *byte_ptr = data + cur_byte; |
| 571 | unsigned int bits = hi_bit - lo_bit; |
| 572 | unsigned int mask = ((1 << bits) - 1) << lo_bit; |
| 573 | *byte_ptr = (*byte_ptr & ~mask) | ((stuff_to_put << lo_bit) & mask); |
| 574 | stuff_to_put >>= bits; |
| 575 | len -= bits; |
| 576 | cur_byte += nextbyte; |
| 577 | lo_bit = 0; |
| 578 | hi_bit = min (len, FLOATFORMAT_CHAR_BIT); |
| 579 | } |
| 580 | while (len != 0); |
| 581 | } |
| 582 | |
| 583 | /* The converse: convert the double *FROM to an extended float |
| 584 | and store where TO points. Neither FROM nor TO have any alignment |
| 585 | restrictions. */ |
| 586 | |
| 587 | void |
| 588 | floatformat_from_double (const struct floatformat *fmt, |
| 589 | const double *from, void *to) |
| 590 | { |
| 591 | double dfrom; |
| 592 | int exponent; |
| 593 | double mant; |
| 594 | unsigned int mant_bits, mant_off; |
| 595 | int mant_bits_left; |
| 596 | unsigned char *uto = (unsigned char *) to; |
| 597 | |
| 598 | dfrom = *from; |
| 599 | memset (uto, 0, fmt->totalsize / FLOATFORMAT_CHAR_BIT); |
| 600 | |
| 601 | /* Split values are not handled specially, since a bottom half of |
| 602 | zero is correct for any value representable as double (in the |
| 603 | only supported case of split values). */ |
| 604 | |
| 605 | /* If negative, set the sign bit. */ |
| 606 | if (dfrom < 0) |
| 607 | { |
| 608 | put_field (uto, fmt->byteorder, fmt->totalsize, fmt->sign_start, 1, 1); |
| 609 | dfrom = -dfrom; |
| 610 | } |
| 611 | |
| 612 | if (dfrom == 0) |
| 613 | { |
| 614 | /* 0.0. */ |
| 615 | return; |
| 616 | } |
| 617 | |
| 618 | if (dfrom != dfrom) |
| 619 | { |
| 620 | /* NaN. */ |
| 621 | put_field (uto, fmt->byteorder, fmt->totalsize, fmt->exp_start, |
| 622 | fmt->exp_len, fmt->exp_nan); |
| 623 | /* Be sure it's not infinity, but NaN value is irrelevant. */ |
| 624 | put_field (uto, fmt->byteorder, fmt->totalsize, fmt->man_start, |
| 625 | 32, 1); |
| 626 | return; |
| 627 | } |
| 628 | |
| 629 | if (dfrom + dfrom == dfrom) |
| 630 | { |
| 631 | /* This can only happen for an infinite value (or zero, which we |
| 632 | already handled above). */ |
| 633 | put_field (uto, fmt->byteorder, fmt->totalsize, fmt->exp_start, |
| 634 | fmt->exp_len, fmt->exp_nan); |
| 635 | return; |
| 636 | } |
| 637 | |
| 638 | mant = frexp (dfrom, &exponent); |
| 639 | if (exponent + fmt->exp_bias - 1 > 0) |
| 640 | put_field (uto, fmt->byteorder, fmt->totalsize, fmt->exp_start, |
| 641 | fmt->exp_len, exponent + fmt->exp_bias - 1); |
| 642 | else |
| 643 | { |
| 644 | /* Handle a denormalized number. FIXME: What should we do for |
| 645 | non-IEEE formats? */ |
| 646 | put_field (uto, fmt->byteorder, fmt->totalsize, fmt->exp_start, |
| 647 | fmt->exp_len, 0); |
| 648 | mant = ldexp (mant, exponent + fmt->exp_bias - 1); |
| 649 | } |
| 650 | |
| 651 | mant_bits_left = fmt->man_len; |
| 652 | mant_off = fmt->man_start; |
| 653 | while (mant_bits_left > 0) |
| 654 | { |
| 655 | unsigned long mant_long; |
| 656 | mant_bits = mant_bits_left < 32 ? mant_bits_left : 32; |
| 657 | |
| 658 | mant *= 4294967296.0; |
| 659 | mant_long = (unsigned long)mant; |
| 660 | mant -= mant_long; |
| 661 | |
| 662 | /* If the integer bit is implicit, and we are not creating a |
| 663 | denormalized number, then we need to discard it. */ |
| 664 | if ((unsigned int) mant_bits_left == fmt->man_len |
| 665 | && fmt->intbit == floatformat_intbit_no |
| 666 | && exponent + fmt->exp_bias - 1 > 0) |
| 667 | { |
| 668 | mant_long &= 0x7fffffff; |
| 669 | mant_bits -= 1; |
| 670 | } |
| 671 | else if (mant_bits < 32) |
| 672 | { |
| 673 | /* The bits we want are in the most significant MANT_BITS bits of |
| 674 | mant_long. Move them to the least significant. */ |
| 675 | mant_long >>= 32 - mant_bits; |
| 676 | } |
| 677 | |
| 678 | put_field (uto, fmt->byteorder, fmt->totalsize, |
| 679 | mant_off, mant_bits, mant_long); |
| 680 | mant_off += mant_bits; |
| 681 | mant_bits_left -= mant_bits; |
| 682 | } |
| 683 | } |
| 684 | |
| 685 | /* Return non-zero iff the data at FROM is a valid number in format FMT. */ |
| 686 | |
| 687 | int |
| 688 | floatformat_is_valid (const struct floatformat *fmt, const void *from) |
| 689 | { |
| 690 | return fmt->is_valid (fmt, from); |
| 691 | } |
| 692 | |
| 693 | |
| 694 | #ifdef IEEE_DEBUG |
| 695 | |
| 696 | #include <stdio.h> |
| 697 | |
| 698 | /* This is to be run on a host which uses IEEE floating point. */ |
| 699 | |
| 700 | void |
| 701 | ieee_test (double n) |
| 702 | { |
| 703 | double result; |
| 704 | |
| 705 | floatformat_to_double (&floatformat_ieee_double_little, &n, &result); |
| 706 | if ((n != result && (! isnan (n) || ! isnan (result))) |
| 707 | || (n < 0 && result >= 0) |
| 708 | || (n >= 0 && result < 0)) |
| 709 | printf ("Differ(to): %.20g -> %.20g\n", n, result); |
| 710 | |
| 711 | floatformat_from_double (&floatformat_ieee_double_little, &n, &result); |
| 712 | if ((n != result && (! isnan (n) || ! isnan (result))) |
| 713 | || (n < 0 && result >= 0) |
| 714 | || (n >= 0 && result < 0)) |
| 715 | printf ("Differ(from): %.20g -> %.20g\n", n, result); |
| 716 | |
| 717 | #if 0 |
| 718 | { |
| 719 | char exten[16]; |
| 720 | |
| 721 | floatformat_from_double (&floatformat_m68881_ext, &n, exten); |
| 722 | floatformat_to_double (&floatformat_m68881_ext, exten, &result); |
| 723 | if (n != result) |
| 724 | printf ("Differ(to+from): %.20g -> %.20g\n", n, result); |
| 725 | } |
| 726 | #endif |
| 727 | |
| 728 | #if IEEE_DEBUG > 1 |
| 729 | /* This is to be run on a host which uses 68881 format. */ |
| 730 | { |
| 731 | long double ex = *(long double *)exten; |
| 732 | if (ex != n) |
| 733 | printf ("Differ(from vs. extended): %.20g\n", n); |
| 734 | } |
| 735 | #endif |
| 736 | } |
| 737 | |
| 738 | int |
| 739 | main (void) |
| 740 | { |
| 741 | ieee_test (0.0); |
| 742 | ieee_test (0.5); |
| 743 | ieee_test (256.0); |
| 744 | ieee_test (0.12345); |
| 745 | ieee_test (234235.78907234); |
| 746 | ieee_test (-512.0); |
| 747 | ieee_test (-0.004321); |
| 748 | ieee_test (1.2E-70); |
| 749 | ieee_test (1.2E-316); |
| 750 | ieee_test (4.9406564584124654E-324); |
| 751 | ieee_test (- 4.9406564584124654E-324); |
| 752 | ieee_test (- 0.0); |
| 753 | ieee_test (- INFINITY); |
| 754 | ieee_test (- NAN); |
| 755 | ieee_test (INFINITY); |
| 756 | ieee_test (NAN); |
| 757 | return 0; |
| 758 | } |
| 759 | #endif |