libiberty/floatformat.c

   1 /* IEEE floating point support routines, for GDB, the GNU Debugger.
   2    Copyright 1991, 1994, 1999, 2000, 2003, 2005, 2006, 2010, 2012
   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 half, single and double, big and little endian.  */
  81 const struct floatformat floatformat_ieee_half_big =
  82 {
  83   floatformat_big, 16, 0, 1, 5, 15, 31, 6, 10,
  84   floatformat_intbit_no,
  85   "floatformat_ieee_half_big",
  86   floatformat_always_valid,
  87   NULL
  88 };
  89 const struct floatformat floatformat_ieee_half_little =
  90 {
  91   floatformat_little, 16, 0, 1, 5, 15, 31, 6, 10,
  92   floatformat_intbit_no,
  93   "floatformat_ieee_half_little",
  94   floatformat_always_valid,
  95   NULL
  96 };
  97 const struct floatformat floatformat_ieee_single_big =
  98 {
  99   floatformat_big, 32, 0, 1, 8, 127, 255, 9, 23,
 100   floatformat_intbit_no,
 101   "floatformat_ieee_single_big",
 102   floatformat_always_valid,
 103   NULL
 104 };
 105 const struct floatformat floatformat_ieee_single_little =
 106 {
 107   floatformat_little, 32, 0, 1, 8, 127, 255, 9, 23,
 108   floatformat_intbit_no,
 109   "floatformat_ieee_single_little",
 110   floatformat_always_valid,
 111   NULL
 112 };
 113 const struct floatformat floatformat_ieee_double_big =
 114 {
 115   floatformat_big, 64, 0, 1, 11, 1023, 2047, 12, 52,
 116   floatformat_intbit_no,
 117   "floatformat_ieee_double_big",
 118   floatformat_always_valid,
 119   NULL
 120 };
 121 const struct floatformat floatformat_ieee_double_little =
 122 {
 123   floatformat_little, 64, 0, 1, 11, 1023, 2047, 12, 52,
 124   floatformat_intbit_no,
 125   "floatformat_ieee_double_little",
 126   floatformat_always_valid,
 127   NULL
 128 };
 129
 130 /* floatformat for IEEE double, little endian byte order, with big endian word
 131    ordering, as on the ARM.  */
 132
 133 const struct floatformat floatformat_ieee_double_littlebyte_bigword =
 134 {
 135   floatformat_littlebyte_bigword, 64, 0, 1, 11, 1023, 2047, 12, 52,
 136   floatformat_intbit_no,
 137   "floatformat_ieee_double_littlebyte_bigword",
 138   floatformat_always_valid,
 139   NULL
 140 };
 141
 142 /* floatformat for VAX.  Not quite IEEE, but close enough.  */
 143
 144 const struct floatformat floatformat_vax_f =
 145 {
 146   floatformat_vax, 32, 0, 1, 8, 129, 0, 9, 23,
 147   floatformat_intbit_no,
 148   "floatformat_vax_f",
 149   floatformat_always_valid,
 150   NULL
 151 };
 152 const struct floatformat floatformat_vax_d =
 153 {
 154   floatformat_vax, 64, 0, 1, 8, 129, 0, 9, 55,
 155   floatformat_intbit_no,
 156   "floatformat_vax_d",
 157   floatformat_always_valid,
 158   NULL
 159 };
 160 const struct floatformat floatformat_vax_g =
 161 {
 162   floatformat_vax, 64, 0, 1, 11, 1025, 0, 12, 52,
 163   floatformat_intbit_no,
 164   "floatformat_vax_g",
 165   floatformat_always_valid,
 166   NULL
 167 };
 168
 169 static int floatformat_i387_ext_is_valid (const struct floatformat *fmt,
 170                                           const void *from);
 171
 172 static int
 173 floatformat_i387_ext_is_valid (const struct floatformat *fmt, const void *from)
 174 {
 175   /* In the i387 double-extended format, if the exponent is all ones,
 176      then the integer bit must be set.  If the exponent is neither 0
 177      nor ~0, the intbit must also be set.  Only if the exponent is
 178      zero can it be zero, and then it must be zero.  */
 179   unsigned long exponent, int_bit;
 180   const unsigned char *ufrom = (const unsigned char *) from;
 181
 182   exponent = get_field (ufrom, fmt->byteorder, fmt->totalsize,
 183                         fmt->exp_start, fmt->exp_len);
 184   int_bit = get_field (ufrom, fmt->byteorder, fmt->totalsize,
 185                        fmt->man_start, 1);
 186
 187   if ((exponent == 0) != (int_bit == 0))
 188     return 0;
 189   else
 190     return 1;
 191 }
 192
 193 const struct floatformat floatformat_i387_ext =
 194 {
 195   floatformat_little, 80, 0, 1, 15, 0x3fff, 0x7fff, 16, 64,
 196   floatformat_intbit_yes,
 197   "floatformat_i387_ext",
 198   floatformat_i387_ext_is_valid,
 199   NULL
 200 };
 201 const struct floatformat floatformat_m68881_ext =
 202 {
 203   /* Note that the bits from 16 to 31 are unused.  */
 204   floatformat_big, 96, 0, 1, 15, 0x3fff, 0x7fff, 32, 64,
 205   floatformat_intbit_yes,
 206   "floatformat_m68881_ext",
 207   floatformat_always_valid,
 208   NULL
 209 };
 210 const struct floatformat floatformat_i960_ext =
 211 {
 212   /* Note that the bits from 0 to 15 are unused.  */
 213   floatformat_little, 96, 16, 17, 15, 0x3fff, 0x7fff, 32, 64,
 214   floatformat_intbit_yes,
 215   "floatformat_i960_ext",
 216   floatformat_always_valid,
 217   NULL
 218 };
 219 const struct floatformat floatformat_m88110_ext =
 220 {
 221   floatformat_big, 80, 0, 1, 15, 0x3fff, 0x7fff, 16, 64,
 222   floatformat_intbit_yes,
 223   "floatformat_m88110_ext",
 224   floatformat_always_valid,
 225   NULL
 226 };
 227 const struct floatformat floatformat_m88110_harris_ext =
 228 {
 229   /* Harris uses raw format 128 bytes long, but the number is just an ieee
 230      double, and the last 64 bits are wasted. */
 231   floatformat_big,128, 0, 1, 11,  0x3ff,  0x7ff, 12, 52,
 232   floatformat_intbit_no,
 233   "floatformat_m88110_ext_harris",
 234   floatformat_always_valid,
 235   NULL
 236 };
 237 const struct floatformat floatformat_arm_ext_big =
 238 {
 239   /* Bits 1 to 16 are unused.  */
 240   floatformat_big, 96, 0, 17, 15, 0x3fff, 0x7fff, 32, 64,
 241   floatformat_intbit_yes,
 242   "floatformat_arm_ext_big",
 243   floatformat_always_valid,
 244   NULL
 245 };
 246 const struct floatformat floatformat_arm_ext_littlebyte_bigword =
 247 {
 248   /* Bits 1 to 16 are unused.  */
 249   floatformat_littlebyte_bigword, 96, 0, 17, 15, 0x3fff, 0x7fff, 32, 64,
 250   floatformat_intbit_yes,
 251   "floatformat_arm_ext_littlebyte_bigword",
 252   floatformat_always_valid,
 253   NULL
 254 };
 255 const struct floatformat floatformat_ia64_spill_big =
 256 {
 257   floatformat_big, 128, 0, 1, 17, 65535, 0x1ffff, 18, 64,
 258   floatformat_intbit_yes,
 259   "floatformat_ia64_spill_big",
 260   floatformat_always_valid,
 261   NULL
 262 };
 263 const struct floatformat floatformat_ia64_spill_little =
 264 {
 265   floatformat_little, 128, 0, 1, 17, 65535, 0x1ffff, 18, 64,
 266   floatformat_intbit_yes,
 267   "floatformat_ia64_spill_little",
 268   floatformat_always_valid,
 269   NULL
 270 };
 271 const struct floatformat floatformat_ia64_quad_big =
 272 {
 273   floatformat_big, 128, 0, 1, 15, 16383, 0x7fff, 16, 112,
 274   floatformat_intbit_no,
 275   "floatformat_ia64_quad_big",
 276   floatformat_always_valid,
 277   NULL
 278 };
 279 const struct floatformat floatformat_ia64_quad_little =
 280 {
 281   floatformat_little, 128, 0, 1, 15, 16383, 0x7fff, 16, 112,
 282   floatformat_intbit_no,
 283   "floatformat_ia64_quad_little",
 284   floatformat_always_valid,
 285   NULL
 286 };
 287
 288 static int
 289 floatformat_ibm_long_double_is_valid (const struct floatformat *fmt,
 290                                       const void *from)
 291 {
 292   const unsigned char *ufrom = (const unsigned char *) from;
 293   const struct floatformat *hfmt = fmt->split_half;
 294   long top_exp, bot_exp;
 295   int top_nan = 0;
 296
 297   top_exp = get_field (ufrom, hfmt->byteorder, hfmt->totalsize,
 298                        hfmt->exp_start, hfmt->exp_len);
 299   bot_exp = get_field (ufrom + 8, hfmt->byteorder, hfmt->totalsize,
 300                        hfmt->exp_start, hfmt->exp_len);
 301
 302   if ((unsigned long) top_exp == hfmt->exp_nan)
 303     top_nan = mant_bits_set (hfmt, ufrom);
 304
 305   /* A NaN is valid with any low part.  */
 306   if (top_nan)
 307     return 1;
 308
 309   /* An infinity, zero or denormal requires low part 0 (positive or
 310      negative).  */
 311   if ((unsigned long) top_exp == hfmt->exp_nan || top_exp == 0)
 312     {
 313       if (bot_exp != 0)
 314         return 0;
 315
 316       return !mant_bits_set (hfmt, ufrom + 8);
 317     }
 318
 319   /* The top part is now a finite normal value.  The long double value
 320      is the sum of the two parts, and the top part must equal the
 321      result of rounding the long double value to nearest double.  Thus
 322      the bottom part must be <= 0.5ulp of the top part in absolute
 323      value, and if it is < 0.5ulp then the long double is definitely
 324      valid.  */
 325   if (bot_exp < top_exp - 53)
 326     return 1;
 327   if (bot_exp > top_exp - 53 && bot_exp != 0)
 328     return 0;
 329   if (bot_exp == 0)
 330     {
 331       /* The bottom part is 0 or denormal.  Determine which, and if
 332          denormal the first two set bits.  */
 333       int first_bit = -1, second_bit = -1, cur_bit;
 334       for (cur_bit = 0; (unsigned int) cur_bit < hfmt->man_len; cur_bit++)
 335         if (get_field (ufrom + 8, hfmt->byteorder, hfmt->totalsize,
 336                        hfmt->man_start + cur_bit, 1))
 337           {
 338             if (first_bit == -1)
 339               first_bit = cur_bit;
 340             else
 341               {
 342                 second_bit = cur_bit;
 343                 break;
 344               }
 345           }
 346       /* Bottom part 0 is OK.  */
 347       if (first_bit == -1)
 348         return 1;
 349       /* The real exponent of the bottom part is -first_bit.  */
 350       if (-first_bit < top_exp - 53)
 351         return 1;
 352       if (-first_bit > top_exp - 53)
 353         return 0;
 354       /* The bottom part is at least 0.5ulp of the top part.  For this
 355          to be OK, the bottom part must be exactly 0.5ulp (i.e. no
 356          more bits set) and the top part must have last bit 0.  */
 357       if (second_bit != -1)
 358         return 0;
 359       return !get_field (ufrom, hfmt->byteorder, hfmt->totalsize,
 360                          hfmt->man_start + hfmt->man_len - 1, 1);
 361     }
 362   else
 363     {
 364       /* The bottom part is at least 0.5ulp of the top part.  For this
 365          to be OK, it must be exactly 0.5ulp (i.e. no explicit bits
 366          set) and the top part must have last bit 0.  */
 367       if (get_field (ufrom, hfmt->byteorder, hfmt->totalsize,
 368                      hfmt->man_start + hfmt->man_len - 1, 1))
 369         return 0;
 370       return !mant_bits_set (hfmt, ufrom + 8);
 371     }
 372 }
 373
 374 const struct floatformat floatformat_ibm_long_double =
 375 {
 376   floatformat_big, 128, 0, 1, 11, 1023, 2047, 12, 52,
 377   floatformat_intbit_no,
 378   "floatformat_ibm_long_double",
 379   floatformat_ibm_long_double_is_valid,
 380   &floatformat_ieee_double_big
 381 };
 382 \f
 383
 384 #ifndef min
 385 #define min(a, b) ((a) < (b) ? (a) : (b))
 386 #endif
 387
 388 /* Return 1 if any bits are explicitly set in the mantissa of UFROM,
 389    format FMT, 0 otherwise.  */
 390 static int
 391 mant_bits_set (const struct floatformat *fmt, const unsigned char *ufrom)
 392 {
 393   unsigned int mant_bits, mant_off;
 394   int mant_bits_left;
 395
 396   mant_off = fmt->man_start;
 397   mant_bits_left = fmt->man_len;
 398   while (mant_bits_left > 0)
 399     {
 400       mant_bits = min (mant_bits_left, 32);
 401
 402       if (get_field (ufrom, fmt->byteorder, fmt->totalsize,
 403                      mant_off, mant_bits) != 0)
 404         return 1;
 405
 406       mant_off += mant_bits;
 407       mant_bits_left -= mant_bits;
 408     }
 409   return 0;
 410 }
 411
 412 /* Extract a field which starts at START and is LEN bits long.  DATA and
 413    TOTAL_LEN are the thing we are extracting it from, in byteorder ORDER.  */
 414 static unsigned long
 415 get_field (const unsigned char *data, enum floatformat_byteorders order,
 416            unsigned int total_len, unsigned int start, unsigned int len)
 417 {
 418   unsigned long result = 0;
 419   unsigned int cur_byte;
 420   int lo_bit, hi_bit, cur_bitshift = 0;
 421   int nextbyte = (order == floatformat_little) ? 1 : -1;
 422
 423   /* Start is in big-endian bit order!  Fix that first.  */
 424   start = total_len - (start + len);
 425
 426   /* Start at the least significant part of the field.  */
 427   if (order == floatformat_little)
 428     cur_byte = start / FLOATFORMAT_CHAR_BIT;
 429   else
 430     cur_byte = (total_len - start - 1) / FLOATFORMAT_CHAR_BIT;
 431
 432   lo_bit = start % FLOATFORMAT_CHAR_BIT;
 433   hi_bit = min (lo_bit + len, FLOATFORMAT_CHAR_BIT);
 434
 435   do
 436     {
 437       unsigned int shifted = *(data + cur_byte) >> lo_bit;
 438       unsigned int bits = hi_bit - lo_bit;
 439       unsigned int mask = (1 << bits) - 1;
 440       result |= (shifted & mask) << cur_bitshift;
 441       len -= bits;
 442       cur_bitshift += bits;
 443       cur_byte += nextbyte;
 444       lo_bit = 0;
 445       hi_bit = min (len, FLOATFORMAT_CHAR_BIT);
 446     }
 447   while (len != 0);
 448
 449   return result;
 450 }
 451
 452 /* Convert from FMT to a double.
 453    FROM is the address of the extended float.
 454    Store the double in *TO.  */
 455
 456 void
 457 floatformat_to_double (const struct floatformat *fmt,
 458                        const void *from, double *to)
 459 {
 460   const unsigned char *ufrom = (const unsigned char *) from;
 461   double dto;
 462   long exponent;
 463   unsigned long mant;
 464   unsigned int mant_bits, mant_off;
 465   int mant_bits_left;
 466
 467   /* Split values are not handled specially, since the top half has
 468      the correctly rounded double value (in the only supported case of
 469      split values).  */
 470
 471   exponent = get_field (ufrom, fmt->byteorder, fmt->totalsize,
 472                         fmt->exp_start, fmt->exp_len);
 473
 474   /* If the exponent indicates a NaN, we don't have information to
 475      decide what to do.  So we handle it like IEEE, except that we
 476      don't try to preserve the type of NaN.  FIXME.  */
 477   if ((unsigned long) exponent == fmt->exp_nan)
 478     {
 479       int nan = mant_bits_set (fmt, ufrom);
 480
 481       /* On certain systems (such as GNU/Linux), the use of the
 482          INFINITY macro below may generate a warning that can not be
 483          silenced due to a bug in GCC (PR preprocessor/11931).  The
 484          preprocessor fails to recognise the __extension__ keyword in
 485          conjunction with the GNU/C99 extension for hexadecimal
 486          floating point constants and will issue a warning when
 487          compiling with -pedantic.  */
 488       if (nan)
 489         dto = NAN;
 490       else
 491         dto = INFINITY;
 492
 493       if (get_field (ufrom, fmt->byteorder, fmt->totalsize, fmt->sign_start, 1))
 494         dto = -dto;
 495
 496       *to = dto;
 497
 498       return;
 499     }
 500
 501   mant_bits_left = fmt->man_len;
 502   mant_off = fmt->man_start;
 503   dto = 0.0;
 504
 505   /* Build the result algebraically.  Might go infinite, underflow, etc;
 506      who cares. */
 507
 508   /* For denorms use minimum exponent.  */
 509   if (exponent == 0)
 510     exponent = 1 - fmt->exp_bias;
 511   else
 512     {
 513       exponent -= fmt->exp_bias;
 514
 515       /* If this format uses a hidden bit, explicitly add it in now.
 516          Otherwise, increment the exponent by one to account for the
 517          integer bit.  */
 518
 519       if (fmt->intbit == floatformat_intbit_no)
 520         dto = ldexp (1.0, exponent);
 521       else
 522         exponent++;
 523     }
 524
 525   while (mant_bits_left > 0)
 526     {
 527       mant_bits = min (mant_bits_left, 32);
 528
 529       mant = get_field (ufrom, fmt->byteorder, fmt->totalsize,
 530                          mant_off, mant_bits);
 531
 532       dto += ldexp ((double) mant, exponent - mant_bits);
 533       exponent -= mant_bits;
 534       mant_off += mant_bits;
 535       mant_bits_left -= mant_bits;
 536     }
 537
 538   /* Negate it if negative.  */
 539   if (get_field (ufrom, fmt->byteorder, fmt->totalsize, fmt->sign_start, 1))
 540     dto = -dto;
 541   *to = dto;
 542 }
 543 \f
 544 static void put_field (unsigned char *, enum floatformat_byteorders,
 545                        unsigned int,
 546                        unsigned int,
 547                        unsigned int,
 548                        unsigned long);
 549
 550 /* Set a field which starts at START and is LEN bits long.  DATA and
 551    TOTAL_LEN are the thing we are extracting it from, in byteorder ORDER.  */
 552 static void
 553 put_field (unsigned char *data, enum floatformat_byteorders order,
 554            unsigned int total_len, unsigned int start, unsigned int len,
 555            unsigned long stuff_to_put)
 556 {
 557   unsigned int cur_byte;
 558   int lo_bit, hi_bit;
 559   int nextbyte = (order == floatformat_little) ? 1 : -1;
 560
 561   /* Start is in big-endian bit order!  Fix that first.  */
 562   start = total_len - (start + len);
 563
 564   /* Start at the least significant part of the field.  */
 565   if (order == floatformat_little)
 566     cur_byte = start / FLOATFORMAT_CHAR_BIT;
 567   else
 568     cur_byte = (total_len - start - 1) / FLOATFORMAT_CHAR_BIT;
 569
 570   lo_bit = start % FLOATFORMAT_CHAR_BIT;
 571   hi_bit = min (lo_bit + len, FLOATFORMAT_CHAR_BIT);
 572
 573   do
 574     {
 575       unsigned char *byte_ptr = data + cur_byte;
 576       unsigned int bits = hi_bit - lo_bit;
 577       unsigned int mask = ((1 << bits) - 1) << lo_bit;
 578       *byte_ptr = (*byte_ptr & ~mask) | ((stuff_to_put << lo_bit) & mask);
 579       stuff_to_put >>= bits;
 580       len -= bits;
 581       cur_byte += nextbyte;
 582       lo_bit = 0;
 583       hi_bit = min (len, FLOATFORMAT_CHAR_BIT);
 584     }
 585   while (len != 0);
 586 }
 587
 588 /* The converse: convert the double *FROM to an extended float
 589    and store where TO points.  Neither FROM nor TO have any alignment
 590    restrictions.  */
 591
 592 void
 593 floatformat_from_double (const struct floatformat *fmt,
 594                          const double *from, void *to)
 595 {
 596   double dfrom;
 597   int exponent;
 598   double mant;
 599   unsigned int mant_bits, mant_off;
 600   int mant_bits_left;
 601   unsigned char *uto = (unsigned char *) to;
 602
 603   dfrom = *from;
 604   memset (uto, 0, fmt->totalsize / FLOATFORMAT_CHAR_BIT);
 605
 606   /* Split values are not handled specially, since a bottom half of
 607      zero is correct for any value representable as double (in the
 608      only supported case of split values).  */
 609
 610   /* If negative, set the sign bit.  */
 611   if (dfrom < 0)
 612     {
 613       put_field (uto, fmt->byteorder, fmt->totalsize, fmt->sign_start, 1, 1);
 614       dfrom = -dfrom;
 615     }
 616
 617   if (dfrom == 0)
 618     {
 619       /* 0.0.  */
 620       return;
 621     }
 622
 623   if (dfrom != dfrom)
 624     {
 625       /* NaN.  */
 626       put_field (uto, fmt->byteorder, fmt->totalsize, fmt->exp_start,
 627                  fmt->exp_len, fmt->exp_nan);
 628       /* Be sure it's not infinity, but NaN value is irrelevant.  */
 629       put_field (uto, fmt->byteorder, fmt->totalsize, fmt->man_start,
 630                  32, 1);
 631       return;
 632     }
 633
 634   if (dfrom + dfrom == dfrom)
 635     {
 636       /* This can only happen for an infinite value (or zero, which we
 637          already handled above).  */
 638       put_field (uto, fmt->byteorder, fmt->totalsize, fmt->exp_start,
 639                  fmt->exp_len, fmt->exp_nan);
 640       return;
 641     }
 642
 643   mant = frexp (dfrom, &exponent);
 644   if (exponent + fmt->exp_bias - 1 > 0)
 645     put_field (uto, fmt->byteorder, fmt->totalsize, fmt->exp_start,
 646                fmt->exp_len, exponent + fmt->exp_bias - 1);
 647   else
 648     {
 649       /* Handle a denormalized number.  FIXME: What should we do for
 650          non-IEEE formats?  */
 651       put_field (uto, fmt->byteorder, fmt->totalsize, fmt->exp_start,
 652                  fmt->exp_len, 0);
 653       mant = ldexp (mant, exponent + fmt->exp_bias - 1);
 654     }
 655
 656   mant_bits_left = fmt->man_len;
 657   mant_off = fmt->man_start;
 658   while (mant_bits_left > 0)
 659     {
 660       unsigned long mant_long;
 661       mant_bits = mant_bits_left < 32 ? mant_bits_left : 32;
 662
 663       mant *= 4294967296.0;
 664       mant_long = (unsigned long)mant;
 665       mant -= mant_long;
 666
 667       /* If the integer bit is implicit, and we are not creating a
 668          denormalized number, then we need to discard it.  */
 669       if ((unsigned int) mant_bits_left == fmt->man_len
 670           && fmt->intbit == floatformat_intbit_no
 671           && exponent + fmt->exp_bias - 1 > 0)
 672         {
 673           mant_long &= 0x7fffffff;
 674           mant_bits -= 1;
 675         }
 676       else if (mant_bits < 32)
 677         {
 678           /* The bits we want are in the most significant MANT_BITS bits of
 679              mant_long.  Move them to the least significant.  */
 680           mant_long >>= 32 - mant_bits;
 681         }
 682
 683       put_field (uto, fmt->byteorder, fmt->totalsize,
 684                  mant_off, mant_bits, mant_long);
 685       mant_off += mant_bits;
 686       mant_bits_left -= mant_bits;
 687     }
 688 }
 689
 690 /* Return non-zero iff the data at FROM is a valid number in format FMT.  */
 691
 692 int
 693 floatformat_is_valid (const struct floatformat *fmt, const void *from)
 694 {
 695   return fmt->is_valid (fmt, from);
 696 }
 697
 698
 699 #ifdef IEEE_DEBUG
 700
 701 #include <stdio.h>
 702
 703 /* This is to be run on a host which uses IEEE floating point.  */
 704
 705 void
 706 ieee_test (double n)
 707 {
 708   double result;
 709
 710   floatformat_to_double (&floatformat_ieee_double_little, &n, &result);
 711   if ((n != result && (! isnan (n) || ! isnan (result)))
 712       || (n < 0 && result >= 0)
 713       || (n >= 0 && result < 0))
 714     printf ("Differ(to): %.20g -> %.20g\n", n, result);
 715
 716   floatformat_from_double (&floatformat_ieee_double_little, &n, &result);
 717   if ((n != result && (! isnan (n) || ! isnan (result)))
 718       || (n < 0 && result >= 0)
 719       || (n >= 0 && result < 0))
 720     printf ("Differ(from): %.20g -> %.20g\n", n, result);
 721
 722 #if 0
 723   {
 724     char exten[16];
 725
 726     floatformat_from_double (&floatformat_m68881_ext, &n, exten);
 727     floatformat_to_double (&floatformat_m68881_ext, exten, &result);
 728     if (n != result)
 729       printf ("Differ(to+from): %.20g -> %.20g\n", n, result);
 730   }
 731 #endif
 732
 733 #if IEEE_DEBUG > 1
 734   /* This is to be run on a host which uses 68881 format.  */
 735   {
 736     long double ex = *(long double *)exten;
 737     if (ex != n)
 738       printf ("Differ(from vs. extended): %.20g\n", n);
 739   }
 740 #endif
 741 }
 742
 743 int
 744 main (void)
 745 {
 746   ieee_test (0.0);
 747   ieee_test (0.5);
 748   ieee_test (1.1);
 749   ieee_test (256.0);
 750   ieee_test (0.12345);
 751   ieee_test (234235.78907234);
 752   ieee_test (-512.0);
 753   ieee_test (-0.004321);
 754   ieee_test (1.2E-70);
 755   ieee_test (1.2E-316);
 756   ieee_test (4.9406564584124654E-324);
 757   ieee_test (- 4.9406564584124654E-324);
 758   ieee_test (- 0.0);
 759   ieee_test (- INFINITY);
 760   ieee_test (- NAN);
 761   ieee_test (INFINITY);
 762   ieee_test (NAN);
 763   return 0;
 764 }
 765 #endif