gcc/dfp.cc

   1 /* Decimal floating point support.
   2    Copyright (C) 2005-2024 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 #include "config.h"
  21 #include "system.h"
  22 #include "coretypes.h"
  23 #include "tm.h"
  24 #include "tree.h"
  25 #include "dfp.h"
  26
  27 /* The order of the following headers is important for making sure
  28    decNumber structure is large enough to hold decimal128 digits.  */
  29
  30 #include "decimal128.h"
  31 #include "decimal64.h"
  32 #include "decimal32.h"
  33
  34 #ifndef WORDS_BIGENDIAN
  35 #define WORDS_BIGENDIAN 0
  36 #endif
  37
  38 /* Initialize R (a real with the decimal flag set) from DN.  Can
  39    utilize status passed in via CONTEXT, if a previous operation had
  40    interesting status.  */
  41
  42 static void
  43 decimal_from_decnumber (REAL_VALUE_TYPE *r, decNumber *dn, decContext *context)
  44 {
  45   memset (r, 0, sizeof (REAL_VALUE_TYPE));
  46
  47   r->cl = rvc_normal;
  48   if (decNumberIsNaN (dn))
  49     r->cl = rvc_nan;
  50   if (decNumberIsInfinite (dn))
  51     r->cl = rvc_inf;
  52   if (context->status & DEC_Overflow)
  53     r->cl = rvc_inf;
  54   if (decNumberIsNegative (dn))
  55     r->sign = 1;
  56   r->decimal = 1;
  57
  58   if (r->cl != rvc_normal)
  59     return;
  60
  61   decContextDefault (context, DEC_INIT_DECIMAL128);
  62   context->traps = 0;
  63
  64   decimal128FromNumber ((decimal128 *) r->sig, dn, context);
  65 }
  66
  67 /* Create decimal encoded R from string S.  */
  68
  69 void
  70 decimal_real_from_string (REAL_VALUE_TYPE *r, const char *s)
  71 {
  72   decNumber dn;
  73   decContext set;
  74   decContextDefault (&set, DEC_INIT_DECIMAL128);
  75   set.traps = 0;
  76
  77   decNumberFromString (&dn, s, &set);
  78
  79   /* It would be more efficient to store directly in decNumber format,
  80      but that is impractical from current data structure size.
  81      Encoding as a decimal128 is much more compact.  */
  82   decimal_from_decnumber (r, &dn, &set);
  83 }
  84
  85 /* Initialize a decNumber from a REAL_VALUE_TYPE.  */
  86
  87 static void
  88 decimal_to_decnumber (const REAL_VALUE_TYPE *r, decNumber *dn)
  89 {
  90   decContext set;
  91   decContextDefault (&set, DEC_INIT_DECIMAL128);
  92   set.traps = 0;
  93
  94   switch (r->cl)
  95     {
  96     case rvc_zero:
  97       decNumberZero (dn);
  98       break;
  99     case rvc_inf:
 100       decNumberFromString (dn, "Infinity", &set);
 101       break;
 102     case rvc_nan:
 103       if (r->signalling)
 104         decNumberFromString (dn, "snan", &set);
 105       else
 106         decNumberFromString (dn, "nan", &set);
 107       break;
 108     case rvc_normal:
 109       if (!r->decimal)
 110         {
 111           /* dconst{1,2,m1,half} are used in various places in
 112              the middle-end and optimizers, allow them here
 113              as an exception by converting them to decimal.  */
 114           if (memcmp (r, &dconst1, sizeof (*r)) == 0)
 115             {
 116               decNumberFromString (dn, "1", &set);
 117               break;
 118             }
 119           if (memcmp (r, &dconst2, sizeof (*r)) == 0)
 120             {
 121               decNumberFromString (dn, "2", &set);
 122               break;
 123             }
 124           if (memcmp (r, &dconstm1, sizeof (*r)) == 0)
 125             {
 126               decNumberFromString (dn, "-1", &set);
 127               break;
 128             }
 129           if (memcmp (r, &dconsthalf, sizeof (*r)) == 0)
 130             {
 131               decNumberFromString (dn, "0.5", &set);
 132               break;
 133             }
 134           gcc_unreachable ();
 135         }
 136       decimal128ToNumber ((const decimal128 *) r->sig, dn);
 137       break;
 138     default:
 139       gcc_unreachable ();
 140     }
 141
 142   /* Fix up sign bit.  */
 143   if (r->sign != decNumberIsNegative (dn))
 144     dn->bits ^= DECNEG;
 145 }
 146
 147 /* Encode a real into an IEEE 754 decimal32 type.  */
 148
 149 void
 150 encode_decimal32 (const struct real_format *fmt ATTRIBUTE_UNUSED,
 151                   long *buf, const REAL_VALUE_TYPE *r)
 152 {
 153   decNumber dn;
 154   decimal32 d32;
 155   decContext set;
 156   int32_t image;
 157
 158   decContextDefault (&set, DEC_INIT_DECIMAL128);
 159   set.traps = 0;
 160
 161   decimal_to_decnumber (r, &dn);
 162   decimal32FromNumber (&d32, &dn, &set);
 163
 164   memcpy (&image, d32.bytes, sizeof (int32_t));
 165   buf[0] = image;
 166 }
 167
 168 /* Decode an IEEE 754 decimal32 type into a real.  */
 169
 170 void
 171 decode_decimal32 (const struct real_format *fmt ATTRIBUTE_UNUSED,
 172                   REAL_VALUE_TYPE *r, const long *buf)
 173 {
 174   decNumber dn;
 175   decimal32 d32;
 176   decContext set;
 177   int32_t image;
 178
 179   decContextDefault (&set, DEC_INIT_DECIMAL128);
 180   set.traps = 0;
 181
 182   image = buf[0];
 183   memcpy (&d32.bytes, &image, sizeof (int32_t));
 184
 185   decimal32ToNumber (&d32, &dn);
 186   decimal_from_decnumber (r, &dn, &set);
 187 }
 188
 189 /* Encode a real into an IEEE 754 decimal64 type.  */
 190
 191 void
 192 encode_decimal64 (const struct real_format *fmt ATTRIBUTE_UNUSED,
 193                   long *buf, const REAL_VALUE_TYPE *r)
 194 {
 195   decNumber dn;
 196   decimal64 d64;
 197   decContext set;
 198   int32_t image;
 199
 200   decContextDefault (&set, DEC_INIT_DECIMAL128);
 201   set.traps = 0;
 202
 203   decimal_to_decnumber (r, &dn);
 204   decimal64FromNumber (&d64, &dn, &set);
 205
 206   if (WORDS_BIGENDIAN == FLOAT_WORDS_BIG_ENDIAN)
 207     {
 208       memcpy (&image, &d64.bytes[0], sizeof (int32_t));
 209       buf[0] = image;
 210       memcpy (&image, &d64.bytes[4], sizeof (int32_t));
 211       buf[1] = image;
 212     }
 213   else
 214     {
 215       memcpy (&image, &d64.bytes[4], sizeof (int32_t));
 216       buf[0] = image;
 217       memcpy (&image, &d64.bytes[0], sizeof (int32_t));
 218       buf[1] = image;
 219     }
 220 }
 221
 222 /* Decode an IEEE 754 decimal64 type into a real.  */
 223
 224 void
 225 decode_decimal64 (const struct real_format *fmt ATTRIBUTE_UNUSED,
 226                   REAL_VALUE_TYPE *r, const long *buf)
 227 {
 228   decNumber dn;
 229   decimal64 d64;
 230   decContext set;
 231   int32_t image;
 232
 233   decContextDefault (&set, DEC_INIT_DECIMAL128);
 234   set.traps = 0;
 235
 236   if (WORDS_BIGENDIAN == FLOAT_WORDS_BIG_ENDIAN)
 237     {
 238       image = buf[0];
 239       memcpy (&d64.bytes[0], &image, sizeof (int32_t));
 240       image = buf[1];
 241       memcpy (&d64.bytes[4], &image, sizeof (int32_t));
 242     }
 243   else
 244     {
 245       image = buf[1];
 246       memcpy (&d64.bytes[0], &image, sizeof (int32_t));
 247       image = buf[0];
 248       memcpy (&d64.bytes[4], &image, sizeof (int32_t));
 249     }
 250
 251   decimal64ToNumber (&d64, &dn);
 252   decimal_from_decnumber (r, &dn, &set);
 253 }
 254
 255 /* Encode a real into an IEEE 754 decimal128 type.  */
 256
 257 void
 258 encode_decimal128 (const struct real_format *fmt ATTRIBUTE_UNUSED,
 259                    long *buf, const REAL_VALUE_TYPE *r)
 260 {
 261   decNumber dn;
 262   decContext set;
 263   decimal128 d128;
 264   int32_t image;
 265
 266   decContextDefault (&set, DEC_INIT_DECIMAL128);
 267   set.traps = 0;
 268
 269   decimal_to_decnumber (r, &dn);
 270   decimal128FromNumber (&d128, &dn, &set);
 271
 272   if (WORDS_BIGENDIAN == FLOAT_WORDS_BIG_ENDIAN)
 273     {
 274       memcpy (&image, &d128.bytes[0], sizeof (int32_t));
 275       buf[0] = image;
 276       memcpy (&image, &d128.bytes[4], sizeof (int32_t));
 277       buf[1] = image;
 278       memcpy (&image, &d128.bytes[8], sizeof (int32_t));
 279       buf[2] = image;
 280       memcpy (&image, &d128.bytes[12], sizeof (int32_t));
 281       buf[3] = image;
 282     }
 283   else
 284     {
 285       memcpy (&image, &d128.bytes[12], sizeof (int32_t));
 286       buf[0] = image;
 287       memcpy (&image, &d128.bytes[8], sizeof (int32_t));
 288       buf[1] = image;
 289       memcpy (&image, &d128.bytes[4], sizeof (int32_t));
 290       buf[2] = image;
 291       memcpy (&image, &d128.bytes[0], sizeof (int32_t));
 292       buf[3] = image;
 293     }
 294 }
 295
 296 /* Decode an IEEE 754 decimal128 type into a real.  */
 297
 298 void
 299 decode_decimal128 (const struct real_format *fmt ATTRIBUTE_UNUSED,
 300                    REAL_VALUE_TYPE *r, const long *buf)
 301 {
 302   decNumber dn;
 303   decimal128 d128;
 304   decContext set;
 305   int32_t image;
 306
 307   decContextDefault (&set, DEC_INIT_DECIMAL128);
 308   set.traps = 0;
 309
 310   if (WORDS_BIGENDIAN == FLOAT_WORDS_BIG_ENDIAN)
 311     {
 312       image = buf[0];
 313       memcpy (&d128.bytes[0],  &image, sizeof (int32_t));
 314       image = buf[1];
 315       memcpy (&d128.bytes[4],  &image, sizeof (int32_t));
 316       image = buf[2];
 317       memcpy (&d128.bytes[8],  &image, sizeof (int32_t));
 318       image = buf[3];
 319       memcpy (&d128.bytes[12], &image, sizeof (int32_t));
 320     }
 321   else
 322     {
 323       image = buf[3];
 324       memcpy (&d128.bytes[0],  &image, sizeof (int32_t));
 325       image = buf[2];
 326       memcpy (&d128.bytes[4],  &image, sizeof (int32_t));
 327       image = buf[1];
 328       memcpy (&d128.bytes[8],  &image, sizeof (int32_t));
 329       image = buf[0];
 330       memcpy (&d128.bytes[12], &image, sizeof (int32_t));
 331     }
 332
 333   decimal128ToNumber (&d128, &dn);
 334   decimal_from_decnumber (r, &dn, &set);
 335 }
 336
 337 /* Helper function to convert from a binary real internal
 338    representation.  */
 339
 340 static void
 341 decimal_to_binary (REAL_VALUE_TYPE *to, const REAL_VALUE_TYPE *from,
 342                    const real_format *fmt)
 343 {
 344   char string[256];
 345   if (from->cl == rvc_normal)
 346     {
 347       const decimal128 *const d128 = (const decimal128 *) from->sig;
 348       decimal128ToString (d128, string);
 349     }
 350   else
 351     real_to_decimal (string, from, sizeof (string), 0, 1);
 352   real_from_string3 (to, string, fmt);
 353 }
 354
 355
 356 /* Helper function to convert from a binary real internal
 357    representation.  */
 358
 359 static void
 360 decimal_from_binary (REAL_VALUE_TYPE *to, const REAL_VALUE_TYPE *from)
 361 {
 362   char string[256];
 363
 364   /* We convert to string, then to decNumber then to decimal128.  */
 365   real_to_decimal (string, from, sizeof (string), 0, 1);
 366   decimal_real_from_string (to, string);
 367   /* When a canonical NaN is originally created, it is not marked as
 368      decimal.  Ensure the result of converting to another decimal type
 369      (which passes through this function) is also marked as
 370      canonical.  */
 371   if (from->cl == rvc_nan && from->canonical)
 372     to->canonical = 1;
 373 }
 374
 375 /* Helper function to real.cc:do_compare() to handle decimal internal
 376    representation including when one of the operands is still in the
 377    binary internal representation.  */
 378
 379 int
 380 decimal_do_compare (const REAL_VALUE_TYPE *a, const REAL_VALUE_TYPE *b,
 381                     int nan_result)
 382 {
 383   decContext set;
 384   decNumber dn, dn2, dn3;
 385   REAL_VALUE_TYPE a1, b1;
 386
 387   /* If either operand is non-decimal, create temporary versions.  */
 388   if (!a->decimal)
 389     {
 390       decimal_from_binary (&a1, a);
 391       a = &a1;
 392     }
 393   if (!b->decimal)
 394     {
 395       decimal_from_binary (&b1, b);
 396       b = &b1;
 397     }
 398
 399   /* Convert into decNumber form for comparison operation.  */
 400   decContextDefault (&set, DEC_INIT_DECIMAL128);
 401   set.traps = 0;
 402   decimal128ToNumber ((const decimal128 *) a->sig, &dn2);
 403   decimal128ToNumber ((const decimal128 *) b->sig, &dn3);
 404
 405   /* Finally, do the comparison.  */
 406   decNumberCompare (&dn, &dn2, &dn3, &set);
 407
 408   /* Return the comparison result.  */
 409   if (decNumberIsNaN (&dn))
 410     return nan_result;
 411   else if (decNumberIsZero (&dn))
 412     return 0;
 413   else if (decNumberIsNegative (&dn))
 414     return -1;
 415   else
 416     return 1;
 417 }
 418
 419 /* Helper to round_for_format, handling decimal float types.  */
 420
 421 void
 422 decimal_round_for_format (const struct real_format *fmt, REAL_VALUE_TYPE *r)
 423 {
 424   decNumber dn;
 425   decContext set;
 426
 427   /* Real encoding occurs later.  */
 428   if (r->cl != rvc_normal)
 429     return;
 430
 431   decContextDefault (&set, DEC_INIT_DECIMAL128);
 432   set.traps = 0;
 433   decimal128ToNumber ((decimal128 *) r->sig, &dn);
 434
 435   if (fmt == &decimal_quad_format)
 436     {
 437       /* The internal format is already in this format.  */
 438       return;
 439     }
 440   else if (fmt == &decimal_single_format)
 441     {
 442       decimal32 d32;
 443       decContextDefault (&set, DEC_INIT_DECIMAL32);
 444       set.traps = 0;
 445
 446       decimal32FromNumber (&d32, &dn, &set);
 447       decimal32ToNumber (&d32, &dn);
 448     }
 449   else if (fmt == &decimal_double_format)
 450     {
 451       decimal64 d64;
 452       decContextDefault (&set, DEC_INIT_DECIMAL64);
 453       set.traps = 0;
 454
 455       decimal64FromNumber (&d64, &dn, &set);
 456       decimal64ToNumber (&d64, &dn);
 457     }
 458   else
 459     gcc_unreachable ();
 460
 461   decimal_from_decnumber (r, &dn, &set);
 462 }
 463
 464 /* Extend or truncate to a new mode.  Handles conversions between
 465    binary and decimal types.  */
 466
 467 void
 468 decimal_real_convert (REAL_VALUE_TYPE *r, const real_format *fmt,
 469                       const REAL_VALUE_TYPE *a)
 470 {
 471   if (a->decimal && fmt->b == 10)
 472     return;
 473   if (a->decimal)
 474       decimal_to_binary (r, a, fmt);
 475   else
 476       decimal_from_binary (r, a);
 477 }
 478
 479 /* Render R_ORIG as a decimal floating point constant.  Emit DIGITS
 480    significant digits in the result, bounded by BUF_SIZE.  If DIGITS
 481    is 0, choose the maximum for the representation.  If
 482    CROP_TRAILING_ZEROS, strip trailing zeros.  Currently, not honoring
 483    DIGITS or CROP_TRAILING_ZEROS.  */
 484
 485 void
 486 decimal_real_to_decimal (char *str, const REAL_VALUE_TYPE *r_orig,
 487                          size_t buf_size,
 488                          size_t digits ATTRIBUTE_UNUSED,
 489                          int crop_trailing_zeros ATTRIBUTE_UNUSED)
 490 {
 491   const decimal128 *const d128 = (const decimal128*) r_orig->sig;
 492
 493   /* decimal128ToString requires space for at least 24 characters;
 494      Require two more for suffix.  */
 495   gcc_assert (buf_size >= 24);
 496   decimal128ToString (d128, str);
 497 }
 498
 499 static bool
 500 decimal_do_add (REAL_VALUE_TYPE *r, const REAL_VALUE_TYPE *op0,
 501                 const REAL_VALUE_TYPE *op1, int subtract_p)
 502 {
 503   decNumber dn;
 504   decContext set;
 505   decNumber dn2, dn3;
 506
 507   decimal_to_decnumber (op0, &dn2);
 508   decimal_to_decnumber (op1, &dn3);
 509
 510   decContextDefault (&set, DEC_INIT_DECIMAL128);
 511   set.traps = 0;
 512
 513   if (subtract_p)
 514     decNumberSubtract (&dn, &dn2, &dn3, &set);
 515   else
 516     decNumberAdd (&dn, &dn2, &dn3, &set);
 517
 518   decimal_from_decnumber (r, &dn, &set);
 519
 520   /* Return true, if inexact.  */
 521   return (set.status & DEC_Inexact);
 522 }
 523
 524 /* Compute R = OP0 * OP1.  */
 525
 526 static bool
 527 decimal_do_multiply (REAL_VALUE_TYPE *r, const REAL_VALUE_TYPE *op0,
 528                      const REAL_VALUE_TYPE *op1)
 529 {
 530   decContext set;
 531   decNumber dn, dn2, dn3;
 532
 533   decimal_to_decnumber (op0, &dn2);
 534   decimal_to_decnumber (op1, &dn3);
 535
 536   decContextDefault (&set, DEC_INIT_DECIMAL128);
 537   set.traps = 0;
 538
 539   decNumberMultiply (&dn, &dn2, &dn3, &set);
 540   decimal_from_decnumber (r, &dn, &set);
 541
 542   /* Return true, if inexact.  */
 543   return (set.status & DEC_Inexact);
 544 }
 545
 546 /* Compute R = OP0 / OP1.  */
 547
 548 static bool
 549 decimal_do_divide (REAL_VALUE_TYPE *r, const REAL_VALUE_TYPE *op0,
 550                    const REAL_VALUE_TYPE *op1)
 551 {
 552   decContext set;
 553   decNumber dn, dn2, dn3;
 554
 555   decimal_to_decnumber (op0, &dn2);
 556   decimal_to_decnumber (op1, &dn3);
 557
 558   decContextDefault (&set, DEC_INIT_DECIMAL128);
 559   set.traps = 0;
 560
 561   decNumberDivide (&dn, &dn2, &dn3, &set);
 562   decimal_from_decnumber (r, &dn, &set);
 563
 564   /* Return true, if inexact.  */
 565   return (set.status & DEC_Inexact);
 566 }
 567
 568 /* Set R to A truncated to an integral value toward zero (decimal
 569    floating point).  */
 570
 571 void
 572 decimal_do_fix_trunc (REAL_VALUE_TYPE *r, const REAL_VALUE_TYPE *a)
 573 {
 574   decNumber dn, dn2;
 575   decContext set;
 576
 577   decContextDefault (&set, DEC_INIT_DECIMAL128);
 578   set.traps = 0;
 579   set.round = DEC_ROUND_DOWN;
 580   decimal128ToNumber ((const decimal128 *) a->sig, &dn2);
 581
 582   decNumberToIntegralValue (&dn, &dn2, &set);
 583   decimal_from_decnumber (r, &dn, &set);
 584 }
 585
 586 /* Render decimal float value R as an integer.  */
 587
 588 HOST_WIDE_INT
 589 decimal_real_to_integer (const REAL_VALUE_TYPE *r)
 590 {
 591   decContext set;
 592   decNumber dn, dn2, dn3;
 593   REAL_VALUE_TYPE to;
 594   char string[256];
 595
 596   decContextDefault (&set, DEC_INIT_DECIMAL128);
 597   set.traps = 0;
 598   set.round = DEC_ROUND_DOWN;
 599   decimal128ToNumber ((const decimal128 *) r->sig, &dn);
 600
 601   decNumberToIntegralValue (&dn2, &dn, &set);
 602   decNumberZero (&dn3);
 603   decNumberRescale (&dn, &dn2, &dn3, &set);
 604
 605   /* Convert to REAL_VALUE_TYPE and call appropriate conversion
 606      function.  */
 607   decNumberToString (&dn, string);
 608   real_from_string (&to, string);
 609   return real_to_integer (&to);
 610 }
 611
 612 /* Likewise, but returns a wide_int with PRECISION.  *FAIL is set if the
 613    value does not fit.  */
 614
 615 wide_int
 616 decimal_real_to_integer (const REAL_VALUE_TYPE *r, bool *fail, int precision)
 617 {
 618   decContext set;
 619   decNumber dn, dn2, dn3;
 620   REAL_VALUE_TYPE to;
 621   char string[256];
 622
 623   decContextDefault (&set, DEC_INIT_DECIMAL128);
 624   set.traps = 0;
 625   set.round = DEC_ROUND_DOWN;
 626   decimal128ToNumber ((const decimal128 *) r->sig, &dn);
 627
 628   decNumberToIntegralValue (&dn2, &dn, &set);
 629   decNumberZero (&dn3);
 630   decNumberRescale (&dn, &dn2, &dn3, &set);
 631
 632   /* Convert to REAL_VALUE_TYPE and call appropriate conversion
 633      function.  */
 634   decNumberToString (&dn, string);
 635   real_from_string (&to, string);
 636   return real_to_integer (&to, fail, precision);
 637 }
 638
 639 /* Perform the decimal floating point operation described by CODE.
 640    For a unary operation, OP1 will be NULL.  This function returns
 641    true if the result may be inexact due to loss of precision.  */
 642
 643 bool
 644 decimal_real_arithmetic (REAL_VALUE_TYPE *r, enum tree_code code,
 645                          const REAL_VALUE_TYPE *op0,
 646                          const REAL_VALUE_TYPE *op1)
 647 {
 648   REAL_VALUE_TYPE a, b;
 649
 650   /* If either operand is non-decimal, create temporaries.  */
 651   if (!op0->decimal)
 652     {
 653       decimal_from_binary (&a, op0);
 654       op0 = &a;
 655     }
 656   if (op1 && !op1->decimal)
 657     {
 658       decimal_from_binary (&b, op1);
 659       op1 = &b;
 660     }
 661
 662   switch (code)
 663     {
 664     case PLUS_EXPR:
 665       return decimal_do_add (r, op0, op1, 0);
 666
 667     case MINUS_EXPR:
 668       return decimal_do_add (r, op0, op1, 1);
 669
 670     case MULT_EXPR:
 671       return decimal_do_multiply (r, op0, op1);
 672
 673     case RDIV_EXPR:
 674       return decimal_do_divide (r, op0, op1);
 675
 676     case MIN_EXPR:
 677       if (op1->cl == rvc_nan)
 678         *r = *op1;
 679       else if (real_compare (UNLT_EXPR, op0, op1))
 680         *r = *op0;
 681       else
 682         *r = *op1;
 683       return false;
 684
 685     case MAX_EXPR:
 686       if (op1->cl == rvc_nan)
 687         *r = *op1;
 688       else if (real_compare (LT_EXPR, op0, op1))
 689         *r = *op1;
 690       else
 691         *r = *op0;
 692       return false;
 693
 694     case NEGATE_EXPR:
 695       {
 696         *r = *op0;
 697         /* Flip sign bit.  */
 698         decimal128FlipSign ((decimal128 *) r->sig);
 699         /* Keep sign field in sync.  */
 700         r->sign ^= 1;
 701       }
 702       return false;
 703
 704     case ABS_EXPR:
 705       {
 706         *r = *op0;
 707         /* Clear sign bit.  */
 708         decimal128ClearSign ((decimal128 *) r->sig);
 709         /* Keep sign field in sync.  */
 710         r->sign = 0;
 711       }
 712       return false;
 713
 714     case FIX_TRUNC_EXPR:
 715       decimal_do_fix_trunc (r, op0);
 716       return false;
 717
 718     default:
 719       gcc_unreachable ();
 720     }
 721 }
 722
 723 /* Fills R with the largest finite value representable in mode MODE.
 724    If SIGN is nonzero, R is set to the most negative finite value.  */
 725
 726 void
 727 decimal_real_maxval (REAL_VALUE_TYPE *r, int sign, machine_mode mode)
 728 {
 729   const char *max;
 730
 731   switch (mode)
 732     {
 733     case E_SDmode:
 734       max = "9.999999E96";
 735       break;
 736     case E_DDmode:
 737       max = "9.999999999999999E384";
 738       break;
 739     case E_TDmode:
 740       max = "9.999999999999999999999999999999999E6144";
 741       break;
 742     default:
 743       gcc_unreachable ();
 744     }
 745
 746   decimal_real_from_string (r, max);
 747   if (sign)
 748     decimal128SetSign ((decimal128 *) r->sig, 1);
 749
 750   r->sign = sign;
 751 }