gcc/real.h

   1 /* Definitions of floating-point access for GNU compiler.
   2    Copyright (C) 1989-2013 Free Software Foundation, Inc.
   3
   4    This file is part of GCC.
   5
   6    GCC is free software; you can redistribute it and/or modify it under
   7    the terms of the GNU General Public License as published by the Free
   8    Software Foundation; either version 3, or (at your option) any later
   9    version.
  10
  11    GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  12    WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14    for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with GCC; see the file COPYING3.  If not see
  18    <http://www.gnu.org/licenses/>.  */
  19
  20 #ifndef GCC_REAL_H
  21 #define GCC_REAL_H
  22
  23 #include "machmode.h"
  24
  25 /* An expanded form of the represented number.  */
  26
  27 /* Enumerate the special cases of numbers that we encounter.  */
  28 enum real_value_class {
  29   rvc_zero,
  30   rvc_normal,
  31   rvc_inf,
  32   rvc_nan
  33 };
  34
  35 #define SIGNIFICAND_BITS        (128 + HOST_BITS_PER_LONG)
  36 #define EXP_BITS                (32 - 6)
  37 #define MAX_EXP                 ((1 << (EXP_BITS - 1)) - 1)
  38 #define SIGSZ                   (SIGNIFICAND_BITS / HOST_BITS_PER_LONG)
  39 #define SIG_MSB                 ((unsigned long)1 << (HOST_BITS_PER_LONG - 1))
  40
  41 struct GTY(()) real_value {
  42   /* Use the same underlying type for all bit-fields, so as to make
  43      sure they're packed together, otherwise REAL_VALUE_TYPE_SIZE will
  44      be miscomputed.  */
  45   unsigned int /* ENUM_BITFIELD (real_value_class) */ cl : 2;
  46   unsigned int decimal : 1;
  47   unsigned int sign : 1;
  48   unsigned int signalling : 1;
  49   unsigned int canonical : 1;
  50   unsigned int uexp : EXP_BITS;
  51   unsigned long sig[SIGSZ];
  52 };
  53
  54 #define REAL_EXP(REAL) \
  55   ((int)((REAL)->uexp ^ (unsigned int)(1 << (EXP_BITS - 1))) \
  56    - (1 << (EXP_BITS - 1)))
  57 #define SET_REAL_EXP(REAL, EXP) \
  58   ((REAL)->uexp = ((unsigned int)(EXP) & (unsigned int)((1 << EXP_BITS) - 1)))
  59
  60 /* Various headers condition prototypes on #ifdef REAL_VALUE_TYPE, so it
  61    needs to be a macro.  We do need to continue to have a structure tag
  62    so that other headers can forward declare it.  */
  63 #define REAL_VALUE_TYPE struct real_value
  64
  65 /* We store a REAL_VALUE_TYPE into an rtx, and we do this by putting it in
  66    consecutive "w" slots.  Moreover, we've got to compute the number of "w"
  67    slots at preprocessor time, which means we can't use sizeof.  Guess.  */
  68
  69 #define REAL_VALUE_TYPE_SIZE (SIGNIFICAND_BITS + 32)
  70 #define REAL_WIDTH \
  71   (REAL_VALUE_TYPE_SIZE/HOST_BITS_PER_WIDE_INT \
  72    + (REAL_VALUE_TYPE_SIZE%HOST_BITS_PER_WIDE_INT ? 1 : 0)) /* round up */
  73
  74 /* Verify the guess.  */
  75 extern char test_real_width
  76   [sizeof (REAL_VALUE_TYPE) <= REAL_WIDTH * sizeof (HOST_WIDE_INT) ? 1 : -1];
  77
  78 /* Calculate the format for CONST_DOUBLE.  We need as many slots as
  79    are necessary to overlay a REAL_VALUE_TYPE on them.  This could be
  80    as many as four (32-bit HOST_WIDE_INT, 128-bit REAL_VALUE_TYPE).
  81
  82    A number of places assume that there are always at least two 'w'
  83    slots in a CONST_DOUBLE, so we provide them even if one would suffice.  */
  84
  85 #if REAL_WIDTH == 1
  86 # define CONST_DOUBLE_FORMAT     "ww"
  87 #else
  88 # if REAL_WIDTH == 2
  89 #  define CONST_DOUBLE_FORMAT    "ww"
  90 # else
  91 #  if REAL_WIDTH == 3
  92 #   define CONST_DOUBLE_FORMAT   "www"
  93 #  else
  94 #   if REAL_WIDTH == 4
  95 #    define CONST_DOUBLE_FORMAT  "wwww"
  96 #   else
  97 #    if REAL_WIDTH == 5
  98 #     define CONST_DOUBLE_FORMAT "wwwww"
  99 #    else
 100 #     if REAL_WIDTH == 6
 101 #      define CONST_DOUBLE_FORMAT "wwwwww"
 102 #     else
 103        #error "REAL_WIDTH > 6 not supported"
 104 #     endif
 105 #    endif
 106 #   endif
 107 #  endif
 108 # endif
 109 #endif
 110
 111
 112 /* Describes the properties of the specific target format in use.  */
 113 struct real_format
 114 {
 115   /* Move to and from the target bytes.  */
 116   void (*encode) (const struct real_format *, long *,
 117                   const REAL_VALUE_TYPE *);
 118   void (*decode) (const struct real_format *, REAL_VALUE_TYPE *,
 119                   const long *);
 120
 121   /* The radix of the exponent and digits of the significand.  */
 122   int b;
 123
 124   /* Size of the significand in digits of radix B.  */
 125   int p;
 126
 127   /* Size of the significant of a NaN, in digits of radix B.  */
 128   int pnan;
 129
 130   /* The minimum negative integer, x, such that b**(x-1) is normalized.  */
 131   int emin;
 132
 133   /* The maximum integer, x, such that b**(x-1) is representable.  */
 134   int emax;
 135
 136   /* The bit position of the sign bit, for determining whether a value
 137      is positive/negative, or -1 for a complex encoding.  */
 138   int signbit_ro;
 139
 140   /* The bit position of the sign bit, for changing the sign of a number,
 141      or -1 for a complex encoding.  */
 142   int signbit_rw;
 143
 144   /* Default rounding mode for operations on this format.  */
 145   bool round_towards_zero;
 146   bool has_sign_dependent_rounding;
 147
 148   /* Properties of the format.  */
 149   bool has_nans;
 150   bool has_inf;
 151   bool has_denorm;
 152   bool has_signed_zero;
 153   bool qnan_msb_set;
 154   bool canonical_nan_lsbs_set;
 155 };
 156
 157
 158 /* The target format used for each floating point mode.
 159    Float modes are followed by decimal float modes, with entries for
 160    float modes indexed by (MODE - first float mode), and entries for
 161    decimal float modes indexed by (MODE - first decimal float mode) +
 162    the number of float modes.  */
 163 extern const struct real_format *
 164   real_format_for_mode[MAX_MODE_FLOAT - MIN_MODE_FLOAT + 1
 165                        + MAX_MODE_DECIMAL_FLOAT - MIN_MODE_DECIMAL_FLOAT + 1];
 166
 167 #define REAL_MODE_FORMAT(MODE)                                          \
 168   (real_format_for_mode[DECIMAL_FLOAT_MODE_P (MODE)                     \
 169                         ? (((MODE) - MIN_MODE_DECIMAL_FLOAT)            \
 170                            + (MAX_MODE_FLOAT - MIN_MODE_FLOAT + 1))     \
 171                         : ((MODE) - MIN_MODE_FLOAT)])
 172
 173 #define FLOAT_MODE_FORMAT(MODE) \
 174   (REAL_MODE_FORMAT (SCALAR_FLOAT_MODE_P (MODE)? (MODE) \
 175                                                : GET_MODE_INNER (MODE)))
 176
 177 /* The following macro determines whether the floating point format is
 178    composite, i.e. may contain non-consecutive mantissa bits, in which
 179    case compile-time FP overflow may not model run-time overflow.  */
 180 #define MODE_COMPOSITE_P(MODE) \
 181   (FLOAT_MODE_P (MODE) \
 182    && FLOAT_MODE_FORMAT (MODE)->pnan < FLOAT_MODE_FORMAT (MODE)->p)
 183
 184 /* Accessor macros for format properties.  */
 185 #define MODE_HAS_NANS(MODE) \
 186   (FLOAT_MODE_P (MODE) && FLOAT_MODE_FORMAT (MODE)->has_nans)
 187 #define MODE_HAS_INFINITIES(MODE) \
 188   (FLOAT_MODE_P (MODE) && FLOAT_MODE_FORMAT (MODE)->has_inf)
 189 #define MODE_HAS_SIGNED_ZEROS(MODE) \
 190   (FLOAT_MODE_P (MODE) && FLOAT_MODE_FORMAT (MODE)->has_signed_zero)
 191 #define MODE_HAS_SIGN_DEPENDENT_ROUNDING(MODE) \
 192   (FLOAT_MODE_P (MODE) \
 193    && FLOAT_MODE_FORMAT (MODE)->has_sign_dependent_rounding)
 194
 195 /* True if the given mode has a NaN representation and the treatment of
 196    NaN operands is important.  Certain optimizations, such as folding
 197    x * 0 into 0, are not correct for NaN operands, and are normally
 198    disabled for modes with NaNs.  The user can ask for them to be
 199    done anyway using the -funsafe-math-optimizations switch.  */
 200 #define HONOR_NANS(MODE) \
 201   (MODE_HAS_NANS (MODE) && !flag_finite_math_only)
 202
 203 /* Like HONOR_NANs, but true if we honor signaling NaNs (or sNaNs).  */
 204 #define HONOR_SNANS(MODE) (flag_signaling_nans && HONOR_NANS (MODE))
 205
 206 /* As for HONOR_NANS, but true if the mode can represent infinity and
 207    the treatment of infinite values is important.  */
 208 #define HONOR_INFINITIES(MODE) \
 209   (MODE_HAS_INFINITIES (MODE) && !flag_finite_math_only)
 210
 211 /* Like HONOR_NANS, but true if the given mode distinguishes between
 212    positive and negative zero, and the sign of zero is important.  */
 213 #define HONOR_SIGNED_ZEROS(MODE) \
 214   (MODE_HAS_SIGNED_ZEROS (MODE) && flag_signed_zeros)
 215
 216 /* Like HONOR_NANS, but true if given mode supports sign-dependent rounding,
 217    and the rounding mode is important.  */
 218 #define HONOR_SIGN_DEPENDENT_ROUNDING(MODE) \
 219   (MODE_HAS_SIGN_DEPENDENT_ROUNDING (MODE) && flag_rounding_math)
 220
 221 /* Declare functions in real.c.  */
 222
 223 /* Binary or unary arithmetic on tree_code.  */
 224 extern bool real_arithmetic (REAL_VALUE_TYPE *, int, const REAL_VALUE_TYPE *,
 225                              const REAL_VALUE_TYPE *);
 226
 227 /* Compare reals by tree_code.  */
 228 extern bool real_compare (int, const REAL_VALUE_TYPE *, const REAL_VALUE_TYPE *);
 229
 230 /* Determine whether a floating-point value X is infinite.  */
 231 extern bool real_isinf (const REAL_VALUE_TYPE *);
 232
 233 /* Determine whether a floating-point value X is a NaN.  */
 234 extern bool real_isnan (const REAL_VALUE_TYPE *);
 235
 236 /* Determine whether a floating-point value X is finite.  */
 237 extern bool real_isfinite (const REAL_VALUE_TYPE *);
 238
 239 /* Determine whether a floating-point value X is negative.  */
 240 extern bool real_isneg (const REAL_VALUE_TYPE *);
 241
 242 /* Determine whether a floating-point value X is minus zero.  */
 243 extern bool real_isnegzero (const REAL_VALUE_TYPE *);
 244
 245 /* Compare two floating-point objects for bitwise identity.  */
 246 extern bool real_identical (const REAL_VALUE_TYPE *, const REAL_VALUE_TYPE *);
 247
 248 /* Extend or truncate to a new mode.  */
 249 extern void real_convert (REAL_VALUE_TYPE *, enum machine_mode,
 250                           const REAL_VALUE_TYPE *);
 251
 252 /* Return true if truncating to NEW is exact.  */
 253 extern bool exact_real_truncate (enum machine_mode, const REAL_VALUE_TYPE *);
 254
 255 /* Render R as a decimal floating point constant.  */
 256 extern void real_to_decimal (char *, const REAL_VALUE_TYPE *, size_t,
 257                              size_t, int);
 258
 259 /* Render R as a decimal floating point constant, rounded so as to be
 260    parsed back to the same value when interpreted in mode MODE.  */
 261 extern void real_to_decimal_for_mode (char *, const REAL_VALUE_TYPE *, size_t,
 262                                       size_t, int, enum machine_mode);
 263
 264 /* Render R as a hexadecimal floating point constant.  */
 265 extern void real_to_hexadecimal (char *, const REAL_VALUE_TYPE *,
 266                                  size_t, size_t, int);
 267
 268 /* Render R as an integer.  */
 269 extern HOST_WIDE_INT real_to_integer (const REAL_VALUE_TYPE *);
 270 extern void real_to_integer2 (HOST_WIDE_INT *, HOST_WIDE_INT *,
 271                               const REAL_VALUE_TYPE *);
 272
 273 /* Initialize R from a decimal or hexadecimal string.  Return -1 if
 274    the value underflows, +1 if overflows, and 0 otherwise.  */
 275 extern int real_from_string (REAL_VALUE_TYPE *, const char *);
 276 /* Wrapper to allow different internal representation for decimal floats. */
 277 extern void real_from_string3 (REAL_VALUE_TYPE *, const char *, enum machine_mode);
 278
 279 /* Initialize R from an integer pair HIGH/LOW.  */
 280 extern void real_from_integer (REAL_VALUE_TYPE *, enum machine_mode,
 281                                unsigned HOST_WIDE_INT, HOST_WIDE_INT, int);
 282
 283 extern long real_to_target_fmt (long *, const REAL_VALUE_TYPE *,
 284                                 const struct real_format *);
 285 extern long real_to_target (long *, const REAL_VALUE_TYPE *, enum machine_mode);
 286
 287 extern void real_from_target_fmt (REAL_VALUE_TYPE *, const long *,
 288                                   const struct real_format *);
 289 extern void real_from_target (REAL_VALUE_TYPE *, const long *,
 290                               enum machine_mode);
 291
 292 extern void real_inf (REAL_VALUE_TYPE *);
 293
 294 extern bool real_nan (REAL_VALUE_TYPE *, const char *, int, enum machine_mode);
 295
 296 extern void real_maxval (REAL_VALUE_TYPE *, int, enum machine_mode);
 297
 298 extern void real_2expN (REAL_VALUE_TYPE *, int, enum machine_mode);
 299
 300 extern unsigned int real_hash (const REAL_VALUE_TYPE *);
 301
 302
 303 /* Target formats defined in real.c.  */
 304 extern const struct real_format ieee_single_format;
 305 extern const struct real_format mips_single_format;
 306 extern const struct real_format motorola_single_format;
 307 extern const struct real_format spu_single_format;
 308 extern const struct real_format ieee_double_format;
 309 extern const struct real_format mips_double_format;
 310 extern const struct real_format motorola_double_format;
 311 extern const struct real_format ieee_extended_motorola_format;
 312 extern const struct real_format ieee_extended_intel_96_format;
 313 extern const struct real_format ieee_extended_intel_96_round_53_format;
 314 extern const struct real_format ieee_extended_intel_128_format;
 315 extern const struct real_format ibm_extended_format;
 316 extern const struct real_format mips_extended_format;
 317 extern const struct real_format ieee_quad_format;
 318 extern const struct real_format mips_quad_format;
 319 extern const struct real_format vax_f_format;
 320 extern const struct real_format vax_d_format;
 321 extern const struct real_format vax_g_format;
 322 extern const struct real_format real_internal_format;
 323 extern const struct real_format decimal_single_format;
 324 extern const struct real_format decimal_double_format;
 325 extern const struct real_format decimal_quad_format;
 326 extern const struct real_format ieee_half_format;
 327 extern const struct real_format arm_half_format;
 328
 329
 330 /* ====================================================================== */
 331 /* Crap.  */
 332
 333 #define REAL_ARITHMETIC(value, code, d1, d2) \
 334   real_arithmetic (&(value), code, &(d1), &(d2))
 335
 336 #define REAL_VALUES_IDENTICAL(x, y)     real_identical (&(x), &(y))
 337 #define REAL_VALUES_EQUAL(x, y)         real_compare (EQ_EXPR, &(x), &(y))
 338 #define REAL_VALUES_LESS(x, y)          real_compare (LT_EXPR, &(x), &(y))
 339
 340 /* Determine whether a floating-point value X is infinite.  */
 341 #define REAL_VALUE_ISINF(x)             real_isinf (&(x))
 342
 343 /* Determine whether a floating-point value X is a NaN.  */
 344 #define REAL_VALUE_ISNAN(x)             real_isnan (&(x))
 345
 346 /* Determine whether a floating-point value X is negative.  */
 347 #define REAL_VALUE_NEGATIVE(x)          real_isneg (&(x))
 348
 349 /* Determine whether a floating-point value X is minus zero.  */
 350 #define REAL_VALUE_MINUS_ZERO(x)        real_isnegzero (&(x))
 351
 352 /* IN is a REAL_VALUE_TYPE.  OUT is an array of longs.  */
 353 #define REAL_VALUE_TO_TARGET_LONG_DOUBLE(IN, OUT)                       \
 354   real_to_target (OUT, &(IN),                                           \
 355                   mode_for_size (LONG_DOUBLE_TYPE_SIZE, MODE_FLOAT, 0))
 356
 357 #define REAL_VALUE_TO_TARGET_DOUBLE(IN, OUT) \
 358   real_to_target (OUT, &(IN), mode_for_size (64, MODE_FLOAT, 0))
 359
 360 /* IN is a REAL_VALUE_TYPE.  OUT is a long.  */
 361 #define REAL_VALUE_TO_TARGET_SINGLE(IN, OUT) \
 362   ((OUT) = real_to_target (NULL, &(IN), mode_for_size (32, MODE_FLOAT, 0)))
 363
 364 #define REAL_VALUE_FROM_INT(r, lo, hi, mode) \
 365   real_from_integer (&(r), mode, lo, hi, 0)
 366
 367 #define REAL_VALUE_FROM_UNSIGNED_INT(r, lo, hi, mode) \
 368   real_from_integer (&(r), mode, lo, hi, 1)
 369
 370 /* Real values to IEEE 754 decimal floats.  */
 371
 372 /* IN is a REAL_VALUE_TYPE.  OUT is an array of longs.  */
 373 #define REAL_VALUE_TO_TARGET_DECIMAL128(IN, OUT) \
 374   real_to_target (OUT, &(IN), mode_for_size (128, MODE_DECIMAL_FLOAT, 0))
 375
 376 #define REAL_VALUE_TO_TARGET_DECIMAL64(IN, OUT) \
 377   real_to_target (OUT, &(IN), mode_for_size (64, MODE_DECIMAL_FLOAT, 0))
 378
 379 /* IN is a REAL_VALUE_TYPE.  OUT is a long.  */
 380 #define REAL_VALUE_TO_TARGET_DECIMAL32(IN, OUT) \
 381   ((OUT) = real_to_target (NULL, &(IN), mode_for_size (32, MODE_DECIMAL_FLOAT, 0)))
 382
 383 extern REAL_VALUE_TYPE real_value_truncate (enum machine_mode,
 384                                             REAL_VALUE_TYPE);
 385
 386 #define REAL_VALUE_TO_INT(plow, phigh, r) \
 387   real_to_integer2 (plow, phigh, &(r))
 388
 389 extern REAL_VALUE_TYPE real_value_negate (const REAL_VALUE_TYPE *);
 390 extern REAL_VALUE_TYPE real_value_abs (const REAL_VALUE_TYPE *);
 391
 392 extern int significand_size (enum machine_mode);
 393
 394 extern REAL_VALUE_TYPE real_from_string2 (const char *, enum machine_mode);
 395
 396 #define REAL_VALUE_ATOF(s, m) \
 397   real_from_string2 (s, m)
 398
 399 #define CONST_DOUBLE_ATOF(s, m) \
 400   CONST_DOUBLE_FROM_REAL_VALUE (real_from_string2 (s, m), m)
 401
 402 #define REAL_VALUE_FIX(r) \
 403   real_to_integer (&(r))
 404
 405 /* ??? Not quite right.  */
 406 #define REAL_VALUE_UNSIGNED_FIX(r) \
 407   real_to_integer (&(r))
 408
 409 /* ??? These were added for Paranoia support.  */
 410
 411 /* Return floor log2(R).  */
 412 extern int real_exponent (const REAL_VALUE_TYPE *);
 413
 414 /* R = A * 2**EXP.  */
 415 extern void real_ldexp (REAL_VALUE_TYPE *, const REAL_VALUE_TYPE *, int);
 416
 417 /* **** End of software floating point emulator interface macros **** */
 418 \f
 419 /* Constant real values 0, 1, 2, -1 and 0.5.  */
 420
 421 extern REAL_VALUE_TYPE dconst0;
 422 extern REAL_VALUE_TYPE dconst1;
 423 extern REAL_VALUE_TYPE dconst2;
 424 extern REAL_VALUE_TYPE dconstm1;
 425 extern REAL_VALUE_TYPE dconsthalf;
 426
 427 #define dconst_e()  (*dconst_e_ptr ())
 428 #define dconst_third()  (*dconst_third_ptr ())
 429 #define dconst_sqrt2()  (*dconst_sqrt2_ptr ())
 430
 431 /* Function to return the real value special constant 'e'.  */
 432 extern const REAL_VALUE_TYPE * dconst_e_ptr (void);
 433
 434 /* Returns the special REAL_VALUE_TYPE corresponding to 1/3.  */
 435 extern const REAL_VALUE_TYPE * dconst_third_ptr (void);
 436
 437 /* Returns the special REAL_VALUE_TYPE corresponding to sqrt(2).  */
 438 extern const REAL_VALUE_TYPE * dconst_sqrt2_ptr (void);
 439
 440 /* Function to return a real value (not a tree node)
 441    from a given integer constant.  */
 442 REAL_VALUE_TYPE real_value_from_int_cst (const_tree, const_tree);
 443
 444 /* Given a CONST_DOUBLE in FROM, store into TO the value it represents.  */
 445 #define REAL_VALUE_FROM_CONST_DOUBLE(to, from) \
 446   ((to) = *CONST_DOUBLE_REAL_VALUE (from))
 447
 448 /* Return a CONST_DOUBLE with value R and mode M.  */
 449 #define CONST_DOUBLE_FROM_REAL_VALUE(r, m) \
 450   const_double_from_real_value (r, m)
 451 extern rtx const_double_from_real_value (REAL_VALUE_TYPE, enum machine_mode);
 452
 453 /* Replace R by 1/R in the given machine mode, if the result is exact.  */
 454 extern bool exact_real_inverse (enum machine_mode, REAL_VALUE_TYPE *);
 455
 456 /* Return true if arithmetic on values in IMODE that were promoted
 457    from values in TMODE is equivalent to direct arithmetic on values
 458    in TMODE.  */
 459 bool real_can_shorten_arithmetic (enum machine_mode, enum machine_mode);
 460
 461 /* In tree.c: wrap up a REAL_VALUE_TYPE in a tree node.  */
 462 extern tree build_real (tree, REAL_VALUE_TYPE);
 463
 464 /* Calculate R as X raised to the integer exponent N in mode MODE.  */
 465 extern bool real_powi (REAL_VALUE_TYPE *, enum machine_mode,
 466                        const REAL_VALUE_TYPE *, HOST_WIDE_INT);
 467
 468 /* Standard round to integer value functions.  */
 469 extern void real_trunc (REAL_VALUE_TYPE *, enum machine_mode,
 470                         const REAL_VALUE_TYPE *);
 471 extern void real_floor (REAL_VALUE_TYPE *, enum machine_mode,
 472                         const REAL_VALUE_TYPE *);
 473 extern void real_ceil (REAL_VALUE_TYPE *, enum machine_mode,
 474                        const REAL_VALUE_TYPE *);
 475 extern void real_round (REAL_VALUE_TYPE *, enum machine_mode,
 476                         const REAL_VALUE_TYPE *);
 477
 478 /* Set the sign of R to the sign of X.  */
 479 extern void real_copysign (REAL_VALUE_TYPE *, const REAL_VALUE_TYPE *);
 480
 481 /* Check whether the real constant value given is an integer.  */
 482 extern bool real_isinteger (const REAL_VALUE_TYPE *c, enum machine_mode mode);
 483
 484 /* Write into BUF the maximum representable finite floating-point
 485    number, (1 - b**-p) * b**emax for a given FP format FMT as a hex
 486    float string.  BUF must be large enough to contain the result.  */
 487 extern void get_max_float (const struct real_format *, char *, size_t);
 488 #endif /* ! GCC_REAL_H */