libiberty/floatformat.c

   1 /* IEEE floating point support routines, for GDB, the GNU Debugger.
   2    Copyright (C) 1991, 1994, 1999, 2000, 2003 Free Software Foundation, Inc.
   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 /* This is needed to pick up the NAN macro on some systems.  */
  21 #define _GNU_SOURCE
  22
  23 #ifdef HAVE_CONFIG_H
  24 #include "config.h"
  25 #endif
  26
  27 #include <math.h>
  28
  29 #ifdef HAVE_STRING_H
  30 #include <string.h>
  31 #endif
  32
  33 #include "ansidecl.h"
  34 #include "libiberty.h"
  35 #include "floatformat.h"
  36
  37 #ifndef INFINITY
  38 #ifdef HUGE_VAL
  39 #define INFINITY HUGE_VAL
  40 #else
  41 #define INFINITY (1.0 / 0.0)
  42 #endif
  43 #endif
  44
  45 #ifndef NAN
  46 #define NAN (0.0 / 0.0)
  47 #endif
  48
  49 static unsigned long get_field PARAMS ((const unsigned char *,
  50                                         enum floatformat_byteorders,
  51                                         unsigned int,
  52                                         unsigned int,
  53                                         unsigned int));
  54 static int floatformat_always_valid PARAMS ((const struct floatformat *fmt,
  55                                              const char *from));
  56
  57 static int
  58 floatformat_always_valid (fmt, from)
  59      const struct floatformat *fmt ATTRIBUTE_UNUSED;
  60      const char *from ATTRIBUTE_UNUSED;
  61 {
  62   return 1;
  63 }
  64
  65 /* The odds that CHAR_BIT will be anything but 8 are low enough that I'm not
  66    going to bother with trying to muck around with whether it is defined in
  67    a system header, what we do if not, etc.  */
  68 #define FLOATFORMAT_CHAR_BIT 8
  69
  70 /* floatformats for IEEE single and double, big and little endian.  */
  71 const struct floatformat floatformat_ieee_single_big =
  72 {
  73   floatformat_big, 32, 0, 1, 8, 127, 255, 9, 23,
  74   floatformat_intbit_no,
  75   "floatformat_ieee_single_big",
  76   floatformat_always_valid
  77 };
  78 const struct floatformat floatformat_ieee_single_little =
  79 {
  80   floatformat_little, 32, 0, 1, 8, 127, 255, 9, 23,
  81   floatformat_intbit_no,
  82   "floatformat_ieee_single_little",
  83   floatformat_always_valid
  84 };
  85 const struct floatformat floatformat_ieee_double_big =
  86 {
  87   floatformat_big, 64, 0, 1, 11, 1023, 2047, 12, 52,
  88   floatformat_intbit_no,
  89   "floatformat_ieee_double_big",
  90   floatformat_always_valid
  91 };
  92 const struct floatformat floatformat_ieee_double_little =
  93 {
  94   floatformat_little, 64, 0, 1, 11, 1023, 2047, 12, 52,
  95   floatformat_intbit_no,
  96   "floatformat_ieee_double_little",
  97   floatformat_always_valid
  98 };
  99
 100 /* floatformat for IEEE double, little endian byte order, with big endian word
 101    ordering, as on the ARM.  */
 102
 103 const struct floatformat floatformat_ieee_double_littlebyte_bigword =
 104 {
 105   floatformat_littlebyte_bigword, 64, 0, 1, 11, 1023, 2047, 12, 52,
 106   floatformat_intbit_no,
 107   "floatformat_ieee_double_littlebyte_bigword",
 108   floatformat_always_valid
 109 };
 110
 111 static int floatformat_i387_ext_is_valid PARAMS ((const struct floatformat *fmt, const char *from));
 112
 113 static int
 114 floatformat_i387_ext_is_valid (fmt, from)
 115      const struct floatformat *fmt;
 116      const char *from;
 117 {
 118   /* In the i387 double-extended format, if the exponent is all ones,
 119      then the integer bit must be set.  If the exponent is neither 0
 120      nor ~0, the intbit must also be set.  Only if the exponent is
 121      zero can it be zero, and then it must be zero.  */
 122   unsigned long exponent, int_bit;
 123   const unsigned char *ufrom = (const unsigned char *) from;
 124
 125   exponent = get_field (ufrom, fmt->byteorder, fmt->totalsize,
 126                         fmt->exp_start, fmt->exp_len);
 127   int_bit = get_field (ufrom, fmt->byteorder, fmt->totalsize,
 128                        fmt->man_start, 1);
 129
 130   if ((exponent == 0) != (int_bit == 0))
 131     return 0;
 132   else
 133     return 1;
 134 }
 135
 136 const struct floatformat floatformat_i387_ext =
 137 {
 138   floatformat_little, 80, 0, 1, 15, 0x3fff, 0x7fff, 16, 64,
 139   floatformat_intbit_yes,
 140   "floatformat_i387_ext",
 141   floatformat_i387_ext_is_valid
 142 };
 143 const struct floatformat floatformat_m68881_ext =
 144 {
 145   /* Note that the bits from 16 to 31 are unused.  */
 146   floatformat_big, 96, 0, 1, 15, 0x3fff, 0x7fff, 32, 64,
 147   floatformat_intbit_yes,
 148   "floatformat_m68881_ext",
 149   floatformat_always_valid
 150 };
 151 const struct floatformat floatformat_i960_ext =
 152 {
 153   /* Note that the bits from 0 to 15 are unused.  */
 154   floatformat_little, 96, 16, 17, 15, 0x3fff, 0x7fff, 32, 64,
 155   floatformat_intbit_yes,
 156   "floatformat_i960_ext",
 157   floatformat_always_valid
 158 };
 159 const struct floatformat floatformat_m88110_ext =
 160 {
 161   floatformat_big, 80, 0, 1, 15, 0x3fff, 0x7fff, 16, 64,
 162   floatformat_intbit_yes,
 163   "floatformat_m88110_ext",
 164   floatformat_always_valid
 165 };
 166 const struct floatformat floatformat_m88110_harris_ext =
 167 {
 168   /* Harris uses raw format 128 bytes long, but the number is just an ieee
 169      double, and the last 64 bits are wasted. */
 170   floatformat_big,128, 0, 1, 11,  0x3ff,  0x7ff, 12, 52,
 171   floatformat_intbit_no,
 172   "floatformat_m88110_ext_harris",
 173   floatformat_always_valid
 174 };
 175 const struct floatformat floatformat_arm_ext_big =
 176 {
 177   /* Bits 1 to 16 are unused.  */
 178   floatformat_big, 96, 0, 17, 15, 0x3fff, 0x7fff, 32, 64,
 179   floatformat_intbit_yes,
 180   "floatformat_arm_ext_big",
 181   floatformat_always_valid
 182 };
 183 const struct floatformat floatformat_arm_ext_littlebyte_bigword =
 184 {
 185   /* Bits 1 to 16 are unused.  */
 186   floatformat_littlebyte_bigword, 96, 0, 17, 15, 0x3fff, 0x7fff, 32, 64,
 187   floatformat_intbit_yes,
 188   "floatformat_arm_ext_littlebyte_bigword",
 189   floatformat_always_valid
 190 };
 191 const struct floatformat floatformat_ia64_spill_big =
 192 {
 193   floatformat_big, 128, 0, 1, 17, 65535, 0x1ffff, 18, 64,
 194   floatformat_intbit_yes,
 195   "floatformat_ia64_spill_big",
 196   floatformat_always_valid
 197 };
 198 const struct floatformat floatformat_ia64_spill_little =
 199 {
 200   floatformat_little, 128, 0, 1, 17, 65535, 0x1ffff, 18, 64,
 201   floatformat_intbit_yes,
 202   "floatformat_ia64_spill_little",
 203   floatformat_always_valid
 204 };
 205 const struct floatformat floatformat_ia64_quad_big =
 206 {
 207   floatformat_big, 128, 0, 1, 15, 16383, 0x7fff, 16, 112,
 208   floatformat_intbit_no,
 209   "floatformat_ia64_quad_big",
 210   floatformat_always_valid
 211 };
 212 const struct floatformat floatformat_ia64_quad_little =
 213 {
 214   floatformat_little, 128, 0, 1, 15, 16383, 0x7fff, 16, 112,
 215   floatformat_intbit_no,
 216   "floatformat_ia64_quad_little",
 217   floatformat_always_valid
 218 };
 219 \f
 220 /* Extract a field which starts at START and is LEN bits long.  DATA and
 221    TOTAL_LEN are the thing we are extracting it from, in byteorder ORDER.  */
 222 static unsigned long
 223 get_field (data, order, total_len, start, len)
 224      const unsigned char *data;
 225      enum floatformat_byteorders order;
 226      unsigned int total_len;
 227      unsigned int start;
 228      unsigned int len;
 229 {
 230   unsigned long result;
 231   unsigned int cur_byte;
 232   int cur_bitshift;
 233
 234   /* Start at the least significant part of the field.  */
 235   cur_byte = (start + len) / FLOATFORMAT_CHAR_BIT;
 236   if (order == floatformat_little)
 237     cur_byte = (total_len / FLOATFORMAT_CHAR_BIT) - cur_byte - 1;
 238   cur_bitshift =
 239     ((start + len) % FLOATFORMAT_CHAR_BIT) - FLOATFORMAT_CHAR_BIT;
 240   result = *(data + cur_byte) >> (-cur_bitshift);
 241   cur_bitshift += FLOATFORMAT_CHAR_BIT;
 242   if (order == floatformat_little)
 243     ++cur_byte;
 244   else
 245     --cur_byte;
 246
 247   /* Move towards the most significant part of the field.  */
 248   while ((unsigned int) cur_bitshift < len)
 249     {
 250       if (len - cur_bitshift < FLOATFORMAT_CHAR_BIT)
 251         /* This is the last byte; zero out the bits which are not part of
 252            this field.  */
 253         result |=
 254           (*(data + cur_byte) & ((1 << (len - cur_bitshift)) - 1))
 255             << cur_bitshift;
 256       else
 257         result |= *(data + cur_byte) << cur_bitshift;
 258       cur_bitshift += FLOATFORMAT_CHAR_BIT;
 259       if (order == floatformat_little)
 260         ++cur_byte;
 261       else
 262         --cur_byte;
 263     }
 264   return result;
 265 }
 266
 267 #ifndef min
 268 #define min(a, b) ((a) < (b) ? (a) : (b))
 269 #endif
 270
 271 /* Convert from FMT to a double.
 272    FROM is the address of the extended float.
 273    Store the double in *TO.  */
 274
 275 void
 276 floatformat_to_double (fmt, from, to)
 277      const struct floatformat *fmt;
 278      const char *from;
 279      double *to;
 280 {
 281   const unsigned char *ufrom = (const unsigned char *)from;
 282   double dto;
 283   long exponent;
 284   unsigned long mant;
 285   unsigned int mant_bits, mant_off;
 286   int mant_bits_left;
 287   int special_exponent;         /* It's a NaN, denorm or zero */
 288
 289   exponent = get_field (ufrom, fmt->byteorder, fmt->totalsize,
 290                         fmt->exp_start, fmt->exp_len);
 291
 292   /* If the exponent indicates a NaN, we don't have information to
 293      decide what to do.  So we handle it like IEEE, except that we
 294      don't try to preserve the type of NaN.  FIXME.  */
 295   if ((unsigned long) exponent == fmt->exp_nan)
 296     {
 297       int nan;
 298
 299       mant_off = fmt->man_start;
 300       mant_bits_left = fmt->man_len;
 301       nan = 0;
 302       while (mant_bits_left > 0)
 303         {
 304           mant_bits = min (mant_bits_left, 32);
 305
 306           if (get_field (ufrom, fmt->byteorder, fmt->totalsize,
 307                          mant_off, mant_bits) != 0)
 308             {
 309               /* This is a NaN.  */
 310               nan = 1;
 311               break;
 312             }
 313
 314           mant_off += mant_bits;
 315           mant_bits_left -= mant_bits;
 316         }
 317
 318       if (nan)
 319         dto = NAN;
 320       else
 321         dto = INFINITY;
 322
 323       if (get_field (ufrom, fmt->byteorder, fmt->totalsize, fmt->sign_start, 1))
 324         dto = -dto;
 325
 326       *to = dto;
 327
 328       return;
 329     }
 330
 331   mant_bits_left = fmt->man_len;
 332   mant_off = fmt->man_start;
 333   dto = 0.0;
 334
 335   special_exponent = exponent == 0 || (unsigned long) exponent == fmt->exp_nan;
 336
 337   /* Don't bias zero's, denorms or NaNs.  */
 338   if (!special_exponent)
 339     exponent -= fmt->exp_bias;
 340
 341   /* Build the result algebraically.  Might go infinite, underflow, etc;
 342      who cares. */
 343
 344   /* If this format uses a hidden bit, explicitly add it in now.  Otherwise,
 345      increment the exponent by one to account for the integer bit.  */
 346
 347   if (!special_exponent)
 348     {
 349       if (fmt->intbit == floatformat_intbit_no)
 350         dto = ldexp (1.0, exponent);
 351       else
 352         exponent++;
 353     }
 354
 355   while (mant_bits_left > 0)
 356     {
 357       mant_bits = min (mant_bits_left, 32);
 358
 359       mant = get_field (ufrom, fmt->byteorder, fmt->totalsize,
 360                          mant_off, mant_bits);
 361
 362       /* Handle denormalized numbers.  FIXME: What should we do for
 363          non-IEEE formats?  */
 364       if (exponent == 0 && mant != 0)
 365         dto += ldexp ((double)mant,
 366                       (- fmt->exp_bias
 367                        - mant_bits
 368                        - (mant_off - fmt->man_start)
 369                        + 1));
 370       else
 371         dto += ldexp ((double)mant, exponent - mant_bits);
 372       if (exponent != 0)
 373         exponent -= mant_bits;
 374       mant_off += mant_bits;
 375       mant_bits_left -= mant_bits;
 376     }
 377
 378   /* Negate it if negative.  */
 379   if (get_field (ufrom, fmt->byteorder, fmt->totalsize, fmt->sign_start, 1))
 380     dto = -dto;
 381   *to = dto;
 382 }
 383 \f
 384 static void put_field PARAMS ((unsigned char *, enum floatformat_byteorders,
 385                                unsigned int,
 386                                unsigned int,
 387                                unsigned int,
 388                                unsigned long));
 389
 390 /* Set a field which starts at START and is LEN bits long.  DATA and
 391    TOTAL_LEN are the thing we are extracting it from, in byteorder ORDER.  */
 392 static void
 393 put_field (data, order, total_len, start, len, stuff_to_put)
 394      unsigned char *data;
 395      enum floatformat_byteorders order;
 396      unsigned int total_len;
 397      unsigned int start;
 398      unsigned int len;
 399      unsigned long stuff_to_put;
 400 {
 401   unsigned int cur_byte;
 402   int cur_bitshift;
 403
 404   /* Start at the least significant part of the field.  */
 405   cur_byte = (start + len) / FLOATFORMAT_CHAR_BIT;
 406   if (order == floatformat_little)
 407     cur_byte = (total_len / FLOATFORMAT_CHAR_BIT) - cur_byte - 1;
 408   cur_bitshift =
 409     ((start + len) % FLOATFORMAT_CHAR_BIT) - FLOATFORMAT_CHAR_BIT;
 410   *(data + cur_byte) &=
 411     ~(((1 << ((start + len) % FLOATFORMAT_CHAR_BIT)) - 1) << (-cur_bitshift));
 412   *(data + cur_byte) |=
 413     (stuff_to_put & ((1 << FLOATFORMAT_CHAR_BIT) - 1)) << (-cur_bitshift);
 414   cur_bitshift += FLOATFORMAT_CHAR_BIT;
 415   if (order == floatformat_little)
 416     ++cur_byte;
 417   else
 418     --cur_byte;
 419
 420   /* Move towards the most significant part of the field.  */
 421   while ((unsigned int) cur_bitshift < len)
 422     {
 423       if (len - cur_bitshift < FLOATFORMAT_CHAR_BIT)
 424         {
 425           /* This is the last byte.  */
 426           *(data + cur_byte) &=
 427             ~((1 << (len - cur_bitshift)) - 1);
 428           *(data + cur_byte) |= (stuff_to_put >> cur_bitshift);
 429         }
 430       else
 431         *(data + cur_byte) = ((stuff_to_put >> cur_bitshift)
 432                               & ((1 << FLOATFORMAT_CHAR_BIT) - 1));
 433       cur_bitshift += FLOATFORMAT_CHAR_BIT;
 434       if (order == floatformat_little)
 435         ++cur_byte;
 436       else
 437         --cur_byte;
 438     }
 439 }
 440
 441 /* The converse: convert the double *FROM to an extended float
 442    and store where TO points.  Neither FROM nor TO have any alignment
 443    restrictions.  */
 444
 445 void
 446 floatformat_from_double (fmt, from, to)
 447      const struct floatformat *fmt;
 448      const double *from;
 449      char *to;
 450 {
 451   double dfrom;
 452   int exponent;
 453   double mant;
 454   unsigned int mant_bits, mant_off;
 455   int mant_bits_left;
 456   unsigned char *uto = (unsigned char *)to;
 457
 458   dfrom = *from;
 459   memset (uto, 0, fmt->totalsize / FLOATFORMAT_CHAR_BIT);
 460
 461   /* If negative, set the sign bit.  */
 462   if (dfrom < 0)
 463     {
 464       put_field (uto, fmt->byteorder, fmt->totalsize, fmt->sign_start, 1, 1);
 465       dfrom = -dfrom;
 466     }
 467
 468   if (dfrom == 0)
 469     {
 470       /* 0.0.  */
 471       return;
 472     }
 473
 474   if (dfrom != dfrom)
 475     {
 476       /* NaN.  */
 477       put_field (uto, fmt->byteorder, fmt->totalsize, fmt->exp_start,
 478                  fmt->exp_len, fmt->exp_nan);
 479       /* Be sure it's not infinity, but NaN value is irrelevant.  */
 480       put_field (uto, fmt->byteorder, fmt->totalsize, fmt->man_start,
 481                  32, 1);
 482       return;
 483     }
 484
 485   if (dfrom + dfrom == dfrom)
 486     {
 487       /* This can only happen for an infinite value (or zero, which we
 488          already handled above).  */
 489       put_field (uto, fmt->byteorder, fmt->totalsize, fmt->exp_start,
 490                  fmt->exp_len, fmt->exp_nan);
 491       return;
 492     }
 493
 494   mant = frexp (dfrom, &exponent);
 495   if (exponent + fmt->exp_bias - 1 > 0)
 496     put_field (uto, fmt->byteorder, fmt->totalsize, fmt->exp_start,
 497                fmt->exp_len, exponent + fmt->exp_bias - 1);
 498   else
 499     {
 500       /* Handle a denormalized number.  FIXME: What should we do for
 501          non-IEEE formats?  */
 502       put_field (uto, fmt->byteorder, fmt->totalsize, fmt->exp_start,
 503                  fmt->exp_len, 0);
 504       mant = ldexp (mant, exponent + fmt->exp_bias - 1);
 505     }
 506
 507   mant_bits_left = fmt->man_len;
 508   mant_off = fmt->man_start;
 509   while (mant_bits_left > 0)
 510     {
 511       unsigned long mant_long;
 512       mant_bits = mant_bits_left < 32 ? mant_bits_left : 32;
 513
 514       mant *= 4294967296.0;
 515       mant_long = (unsigned long)mant;
 516       mant -= mant_long;
 517
 518       /* If the integer bit is implicit, and we are not creating a
 519          denormalized number, then we need to discard it.  */
 520       if ((unsigned int) mant_bits_left == fmt->man_len
 521           && fmt->intbit == floatformat_intbit_no
 522           && exponent + fmt->exp_bias - 1 > 0)
 523         {
 524           mant_long &= 0x7fffffff;
 525           mant_bits -= 1;
 526         }
 527       else if (mant_bits < 32)
 528         {
 529           /* The bits we want are in the most significant MANT_BITS bits of
 530              mant_long.  Move them to the least significant.  */
 531           mant_long >>= 32 - mant_bits;
 532         }
 533
 534       put_field (uto, fmt->byteorder, fmt->totalsize,
 535                  mant_off, mant_bits, mant_long);
 536       mant_off += mant_bits;
 537       mant_bits_left -= mant_bits;
 538     }
 539 }
 540
 541 /* Return non-zero iff the data at FROM is a valid number in format FMT.  */
 542
 543 int
 544 floatformat_is_valid (fmt, from)
 545      const struct floatformat *fmt;
 546      const char *from;
 547 {
 548   return fmt->is_valid (fmt, from);
 549 }
 550
 551
 552 #ifdef IEEE_DEBUG
 553
 554 #include <stdio.h>
 555
 556 /* This is to be run on a host which uses IEEE floating point.  */
 557
 558 void
 559 ieee_test (n)
 560      double n;
 561 {
 562   double result;
 563
 564   floatformat_to_double (&floatformat_ieee_double_little, (char *) &n,
 565                          &result);
 566   if ((n != result && (! isnan (n) || ! isnan (result)))
 567       || (n < 0 && result >= 0)
 568       || (n >= 0 && result < 0))
 569     printf ("Differ(to): %.20g -> %.20g\n", n, result);
 570
 571   floatformat_from_double (&floatformat_ieee_double_little, &n,
 572                            (char *) &result);
 573   if ((n != result && (! isnan (n) || ! isnan (result)))
 574       || (n < 0 && result >= 0)
 575       || (n >= 0 && result < 0))
 576     printf ("Differ(from): %.20g -> %.20g\n", n, result);
 577
 578 #if 0
 579   {
 580     char exten[16];
 581
 582     floatformat_from_double (&floatformat_m68881_ext, &n, exten);
 583     floatformat_to_double (&floatformat_m68881_ext, exten, &result);
 584     if (n != result)
 585       printf ("Differ(to+from): %.20g -> %.20g\n", n, result);
 586   }
 587 #endif
 588
 589 #if IEEE_DEBUG > 1
 590   /* This is to be run on a host which uses 68881 format.  */
 591   {
 592     long double ex = *(long double *)exten;
 593     if (ex != n)
 594       printf ("Differ(from vs. extended): %.20g\n", n);
 595   }
 596 #endif
 597 }
 598
 599 int
 600 main ()
 601 {
 602   ieee_test (0.0);
 603   ieee_test (0.5);
 604   ieee_test (256.0);
 605   ieee_test (0.12345);
 606   ieee_test (234235.78907234);
 607   ieee_test (-512.0);
 608   ieee_test (-0.004321);
 609   ieee_test (1.2E-70);
 610   ieee_test (1.2E-316);
 611   ieee_test (4.9406564584124654E-324);
 612   ieee_test (- 4.9406564584124654E-324);
 613   ieee_test (- 0.0);
 614   ieee_test (- INFINITY);
 615   ieee_test (- NAN);
 616   ieee_test (INFINITY);
 617   ieee_test (NAN);
 618   return 0;
 619 }
 620 #endif