src/conflicts.c

   1 /* Find and resolve or report look-ahead conflicts for bison,
   2    Copyright 1984, 1989, 1992, 2000, 2001 Free Software Foundation, Inc.
   3
   4    This file is part of Bison, the GNU Compiler Compiler.
   5
   6    Bison is free software; you can redistribute it and/or modify it
   7    under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 2, or (at your option)
   9    any later version.
  10
  11    Bison is distributed in the hope that it will be useful, but
  12    WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with Bison; see the file COPYING.  If not, write to the Free
  18    Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
  19    02111-1307, USA.  */
  20
  21 #include "system.h"
  22 #include "getargs.h"
  23 #include "xalloc.h"
  24 #include "files.h"
  25 #include "gram.h"
  26 #include "state.h"
  27 #include "lalr.h"
  28 #include "conflicts.h"
  29 #include "reader.h"
  30 #include "LR0.h"
  31
  32 int any_conflicts = 0;
  33 errs **err_table = NULL;
  34 int expected_conflicts;
  35 static char *conflicts = NULL;
  36
  37 static unsigned *shiftset = NULL;
  38 static unsigned *lookaheadset = NULL;
  39 static int src_total;
  40 static int rrc_total;
  41 static int src_count;
  42 static int rrc_count;
  43 \f
  44
  45 static inline void
  46 log_resolution (int state, int LAno, int token, char *resolution)
  47 {
  48   obstack_fgrow4 (&output_obstack,
  49                   _("\
  50 Conflict in state %d between rule %d and token %s resolved as %s.\n"),
  51                   state, LAruleno[LAno], tags[token], resolution);
  52 }
  53
  54
  55 /*------------------------------------------------------------------.
  56 | Turn off the shift recorded for the specified token in the        |
  57 | specified state.  Used when we resolve a shift-reduce conflict in |
  58 | favor of the reduction.                                           |
  59 `------------------------------------------------------------------*/
  60
  61 static void
  62 flush_shift (int state, int token)
  63 {
  64   shifts *shiftp;
  65   int k, i;
  66
  67   shiftp = shift_table[state];
  68
  69   if (shiftp)
  70     {
  71       k = shiftp->nshifts;
  72       for (i = 0; i < k; i++)
  73         {
  74           if (shiftp->shifts[i]
  75               && token == accessing_symbol[shiftp->shifts[i]])
  76             (shiftp->shifts[i]) = 0;
  77         }
  78     }
  79 }
  80
  81
  82 /*------------------------------------------------------------------.
  83 | Attempt to resolve shift-reduce conflict for one rule by means of |
  84 | precedence declarations.  It has already been checked that the    |
  85 | rule has a precedence.  A conflict is resolved by modifying the   |
  86 | shift or reduce tables so that there is no longer a conflict.     |
  87 `------------------------------------------------------------------*/
  88
  89 static void
  90 resolve_sr_conflict (int state, int lookaheadnum)
  91 {
  92   int i;
  93   int mask;
  94   unsigned *fp1;
  95   unsigned *fp2;
  96   int redprec;
  97   errs *errp = (errs *) xcalloc (sizeof (errs) + ntokens * sizeof (short), 1);
  98   short *errtokens = errp->errs;
  99
 100   /* find the rule to reduce by to get precedence of reduction  */
 101   redprec = rprec[LAruleno[lookaheadnum]];
 102
 103   mask = 1;
 104   fp1 = LA + lookaheadnum * tokensetsize;
 105   fp2 = lookaheadset;
 106   for (i = 0; i < ntokens; i++)
 107     {
 108       if ((mask & *fp2 & *fp1) && sprec[i])
 109         /* Shift-reduce conflict occurs for token number i
 110            and it has a precedence.
 111            The precedence of shifting is that of token i.  */
 112         {
 113           if (sprec[i] < redprec)
 114             {
 115               log_resolution (state, lookaheadnum, i, _("reduce"));
 116               *fp2 &= ~mask;    /* flush the shift for this token */
 117               flush_shift (state, i);
 118             }
 119           else if (sprec[i] > redprec)
 120             {
 121               log_resolution (state, lookaheadnum, i, _("shift"));
 122               *fp1 &= ~mask;    /* flush the reduce for this token */
 123             }
 124           else
 125             {
 126               /* Matching precedence levels.
 127                  For left association, keep only the reduction.
 128                  For right association, keep only the shift.
 129                  For nonassociation, keep neither.  */
 130
 131               switch (sassoc[i])
 132                 {
 133                 case right_assoc:
 134                   log_resolution (state, lookaheadnum, i, _("shift"));
 135                   break;
 136
 137                 case left_assoc:
 138                   log_resolution (state, lookaheadnum, i, _("reduce"));
 139                   break;
 140
 141                 case non_assoc:
 142                   log_resolution (state, lookaheadnum, i, _("an error"));
 143                   break;
 144                 }
 145
 146               if (sassoc[i] != right_assoc)
 147                 {
 148                   *fp2 &= ~mask;        /* flush the shift for this token */
 149                   flush_shift (state, i);
 150                 }
 151               if (sassoc[i] != left_assoc)
 152                 {
 153                   *fp1 &= ~mask;        /* flush the reduce for this token */
 154                 }
 155               if (sassoc[i] == non_assoc)
 156                 {
 157                   /* Record an explicit error for this token.  */
 158                   *errtokens++ = i;
 159                 }
 160             }
 161         }
 162
 163       mask <<= 1;
 164       if (mask == 0)
 165         {
 166           mask = 1;
 167           fp2++;
 168           fp1++;
 169         }
 170     }
 171   errp->nerrs = errtokens - errp->errs;
 172   if (errp->nerrs)
 173     {
 174       /* Some tokens have been explicitly made errors.  Allocate
 175          a permanent errs structure for this state, to record them.  */
 176       i = (char *) errtokens - (char *) errp;
 177       err_table[state] = (errs *) xcalloc ((unsigned int) i, 1);
 178       bcopy (errp, err_table[state], i);
 179     }
 180   else
 181     err_table[state] = 0;
 182   free (errp);
 183 }
 184
 185
 186 static void
 187 set_conflicts (int state)
 188 {
 189   int i;
 190   int k;
 191   shifts *shiftp;
 192   unsigned *fp2;
 193   unsigned *fp3;
 194   unsigned *fp4;
 195   unsigned *fp1;
 196   int symbol;
 197
 198   if (consistent[state])
 199     return;
 200
 201   for (i = 0; i < tokensetsize; i++)
 202     lookaheadset[i] = 0;
 203
 204   shiftp = shift_table[state];
 205   if (shiftp)
 206     {
 207       k = shiftp->nshifts;
 208       for (i = 0; i < k; i++)
 209         {
 210           symbol = accessing_symbol[shiftp->shifts[i]];
 211           if (ISVAR (symbol))
 212             break;
 213           SETBIT (lookaheadset, symbol);
 214         }
 215     }
 216
 217   k = lookaheads[state + 1];
 218   fp4 = lookaheadset + tokensetsize;
 219
 220   /* Loop over all rules which require lookahead in this state.  First
 221      check for shift-reduce conflict, and try to resolve using
 222      precedence */
 223   for (i = lookaheads[state]; i < k; i++)
 224     if (rprec[LAruleno[i]])
 225       {
 226         fp1 = LA + i * tokensetsize;
 227         fp2 = fp1;
 228         fp3 = lookaheadset;
 229
 230         while (fp3 < fp4)
 231           {
 232             if (*fp2++ & *fp3++)
 233               {
 234                 resolve_sr_conflict (state, i);
 235                 break;
 236               }
 237           }
 238       }
 239
 240
 241   /* Loop over all rules which require lookahead in this state.  Check
 242      for conflicts not resolved above.  */
 243   for (i = lookaheads[state]; i < k; i++)
 244     {
 245       fp1 = LA + i * tokensetsize;
 246       fp2 = fp1;
 247       fp3 = lookaheadset;
 248
 249       while (fp3 < fp4)
 250         {
 251           if (*fp2++ & *fp3++)
 252             {
 253               conflicts[state] = 1;
 254               any_conflicts = 1;
 255             }
 256         }
 257
 258       fp2 = fp1;
 259       fp3 = lookaheadset;
 260
 261       while (fp3 < fp4)
 262         *fp3++ |= *fp2++;
 263     }
 264 }
 265
 266 void
 267 solve_conflicts (void)
 268 {
 269   int i;
 270
 271   conflicts = XCALLOC (char, nstates);
 272   shiftset = XCALLOC (unsigned, tokensetsize);
 273   lookaheadset = XCALLOC (unsigned, tokensetsize);
 274
 275   err_table = XCALLOC (errs *, nstates);
 276
 277   any_conflicts = 0;
 278
 279   for (i = 0; i < nstates; i++)
 280     set_conflicts (i);
 281 }
 282
 283
 284 /*---------------------------------------------.
 285 | Count the number of shift/reduce conflicts.  |
 286 `---------------------------------------------*/
 287
 288 static void
 289 count_sr_conflicts (int state)
 290 {
 291   int i;
 292   int k;
 293   int mask;
 294   shifts *shiftp;
 295   unsigned *fp1;
 296   unsigned *fp2;
 297   unsigned *fp3;
 298   int symbol;
 299
 300   src_count = 0;
 301
 302   shiftp = shift_table[state];
 303   if (!shiftp)
 304     return;
 305
 306   for (i = 0; i < tokensetsize; i++)
 307     {
 308       shiftset[i] = 0;
 309       lookaheadset[i] = 0;
 310     }
 311
 312   k = shiftp->nshifts;
 313   for (i = 0; i < k; i++)
 314     {
 315       if (!shiftp->shifts[i])
 316         continue;
 317       symbol = accessing_symbol[shiftp->shifts[i]];
 318       if (ISVAR (symbol))
 319         break;
 320       SETBIT (shiftset, symbol);
 321     }
 322
 323   k = lookaheads[state + 1];
 324   fp3 = lookaheadset + tokensetsize;
 325
 326   for (i = lookaheads[state]; i < k; i++)
 327     {
 328       fp1 = LA + i * tokensetsize;
 329       fp2 = lookaheadset;
 330
 331       while (fp2 < fp3)
 332         *fp2++ |= *fp1++;
 333     }
 334
 335   fp1 = shiftset;
 336   fp2 = lookaheadset;
 337
 338   while (fp2 < fp3)
 339     *fp2++ &= *fp1++;
 340
 341   mask = 1;
 342   fp2 = lookaheadset;
 343   for (i = 0; i < ntokens; i++)
 344     {
 345       if (mask & *fp2)
 346         src_count++;
 347
 348       mask <<= 1;
 349       if (mask == 0)
 350         {
 351           mask = 1;
 352           fp2++;
 353         }
 354     }
 355 }
 356
 357
 358 /*----------------------------------------------.
 359 | Count the number of reduce/reduce conflicts.  |
 360 `----------------------------------------------*/
 361
 362 static void
 363 count_rr_conflicts (int state)
 364 {
 365   int i;
 366   int j;
 367   int count;
 368   unsigned mask;
 369   unsigned *baseword;
 370   unsigned *wordp;
 371   int m;
 372   int n;
 373
 374   rrc_count = 0;
 375
 376   m = lookaheads[state];
 377   n = lookaheads[state + 1];
 378
 379   if (n - m < 2)
 380     return;
 381
 382   mask = 1;
 383   baseword = LA + m * tokensetsize;
 384   for (i = 0; i < ntokens; i++)
 385     {
 386       wordp = baseword;
 387
 388       count = 0;
 389       for (j = m; j < n; j++)
 390         {
 391           if (mask & *wordp)
 392             count++;
 393
 394           wordp += tokensetsize;
 395         }
 396
 397       if (count >= 2)
 398         rrc_count++;
 399
 400       mask <<= 1;
 401       if (mask == 0)
 402         {
 403           mask = 1;
 404           baseword++;
 405         }
 406     }
 407 }
 408
 409 /*--------------------------------------------------------------.
 410 | Return a human readable string which reports shift/reduce and |
 411 | reduce/reduce conflict numbers (SRC_NUM, RRC_NUM).            |
 412 `--------------------------------------------------------------*/
 413
 414 static const char *
 415 conflict_report (int src_num, int rrc_num)
 416 {
 417   static char res[4096];
 418   char *cp = res;
 419
 420   if (src_num == 1)
 421     {
 422       sprintf (cp, _(" 1 shift/reduce conflict"));
 423       cp += strlen (cp);
 424     }
 425   else if (src_num > 1)
 426     {
 427       sprintf (cp, _(" %d shift/reduce conflicts"), src_num);
 428       cp += strlen (cp);
 429     }
 430
 431   if (src_num > 0 && rrc_num > 0)
 432     {
 433       sprintf (cp, _(" and"));
 434       cp += strlen (cp);
 435     }
 436
 437   if (rrc_num == 1)
 438     {
 439       sprintf (cp, _(" 1 reduce/reduce conflict"));
 440       cp += strlen (cp);
 441     }
 442   else if (rrc_num > 1)
 443     {
 444       sprintf (cp, _(" %d reduce/reduce conflicts"), rrc_num);
 445       cp += strlen (cp);
 446     }
 447
 448   *cp++ = '.';
 449   *cp++ = '\n';
 450   *cp++ = '\0';
 451
 452   return res;
 453 }
 454
 455
 456 /*---------------------------------------------.
 457 | Compute and give a report on the conflicts.  |
 458 `---------------------------------------------*/
 459
 460 void
 461 print_conflicts (FILE *out)
 462 {
 463   int i;
 464
 465   src_total = 0;
 466   rrc_total = 0;
 467
 468   /* Count the total number of conflicts, and if wanted, give a
 469      detailed report in FOUTPUT.  */
 470   for (i = 0; i < nstates; i++)
 471     {
 472       if (conflicts[i])
 473         {
 474           count_sr_conflicts (i);
 475           count_rr_conflicts (i);
 476           src_total += src_count;
 477           rrc_total += rrc_count;
 478
 479           if (verbose_flag)
 480             {
 481               fprintf (out, _("State %d contains"), i);
 482               fputs (conflict_report (src_count, rrc_count), out);
 483             }
 484         }
 485     }
 486
 487   /* Report the total number of conflicts on STDERR.  */
 488   if (yacc_flag)
 489     {
 490       /* If invoked with `--yacc', use the output format specified by
 491          POSIX.  */
 492       fprintf (stderr, _("conflicts: "));
 493       if (src_total > 0)
 494         fprintf (stderr, _(" %d shift/reduce"), src_total);
 495       if (src_total > 0 && rrc_total > 0)
 496         fprintf (stderr, ",");
 497       if (rrc_total > 0)
 498         fprintf (stderr, _(" %d reduce/reduce"), rrc_total);
 499       putc ('\n', stderr);
 500     }
 501   else
 502     {
 503       fprintf (stderr, _("%s contains"), infile);
 504       fputs (conflict_report (src_total, rrc_total), stderr);
 505     }
 506 }
 507
 508
 509 void
 510 print_reductions (int state)
 511 {
 512   int i;
 513   int j;
 514   int k;
 515   unsigned *fp1;
 516   unsigned *fp2;
 517   unsigned *fp3;
 518   unsigned *fp4;
 519   int rule;
 520   int symbol;
 521   unsigned mask;
 522   int m;
 523   int n;
 524   int default_LA;
 525   int default_rule = 0;
 526   int cmax;
 527   int count;
 528   shifts *shiftp;
 529   errs *errp;
 530   int nodefault = 0;
 531
 532   for (i = 0; i < tokensetsize; i++)
 533     shiftset[i] = 0;
 534
 535   shiftp = shift_table[state];
 536   if (shiftp)
 537     {
 538       k = shiftp->nshifts;
 539       for (i = 0; i < k; i++)
 540         {
 541           if (!shiftp->shifts[i])
 542             continue;
 543           symbol = accessing_symbol[shiftp->shifts[i]];
 544           if (ISVAR (symbol))
 545             break;
 546           /* if this state has a shift for the error token,
 547              don't use a default rule.  */
 548           if (symbol == error_token_number)
 549             nodefault = 1;
 550           SETBIT (shiftset, symbol);
 551         }
 552     }
 553
 554   errp = err_table[state];
 555   if (errp)
 556     {
 557       k = errp->nerrs;
 558       for (i = 0; i < k; i++)
 559         {
 560           if (!errp->errs[i])
 561             continue;
 562           symbol = errp->errs[i];
 563           SETBIT (shiftset, symbol);
 564         }
 565     }
 566
 567   m = lookaheads[state];
 568   n = lookaheads[state + 1];
 569
 570   if (n - m == 1 && !nodefault)
 571     {
 572       default_rule = LAruleno[m];
 573
 574       fp1 = LA + m * tokensetsize;
 575       fp2 = shiftset;
 576       fp3 = lookaheadset;
 577       fp4 = lookaheadset + tokensetsize;
 578
 579       while (fp3 < fp4)
 580         *fp3++ = *fp1++ & *fp2++;
 581
 582       mask = 1;
 583       fp3 = lookaheadset;
 584
 585       for (i = 0; i < ntokens; i++)
 586         {
 587           if (mask & *fp3)
 588             obstack_fgrow3 (&output_obstack,
 589                             _("    %-4s\t[reduce using rule %d (%s)]\n"),
 590                             tags[i], default_rule, tags[rlhs[default_rule]]);
 591
 592           mask <<= 1;
 593           if (mask == 0)
 594             {
 595               mask = 1;
 596               fp3++;
 597             }
 598         }
 599
 600       obstack_fgrow2 (&output_obstack,
 601                       _("    $default\treduce using rule %d (%s)\n\n"),
 602                       default_rule, tags[rlhs[default_rule]]);
 603     }
 604   else if (n - m >= 1)
 605     {
 606       cmax = 0;
 607       default_LA = -1;
 608       fp4 = lookaheadset + tokensetsize;
 609
 610       if (!nodefault)
 611         for (i = m; i < n; i++)
 612           {
 613             fp1 = LA + i * tokensetsize;
 614             fp2 = shiftset;
 615             fp3 = lookaheadset;
 616
 617             while (fp3 < fp4)
 618               *fp3++ = *fp1++ & (~(*fp2++));
 619
 620             count = 0;
 621             mask = 1;
 622             fp3 = lookaheadset;
 623             for (j = 0; j < ntokens; j++)
 624               {
 625                 if (mask & *fp3)
 626                   count++;
 627
 628                 mask <<= 1;
 629                 if (mask == 0)
 630                   {
 631                     mask = 1;
 632                     fp3++;
 633                   }
 634               }
 635
 636             if (count > cmax)
 637               {
 638                 cmax = count;
 639                 default_LA = i;
 640                 default_rule = LAruleno[i];
 641               }
 642
 643             fp2 = shiftset;
 644             fp3 = lookaheadset;
 645
 646             while (fp3 < fp4)
 647               *fp2++ |= *fp3++;
 648           }
 649
 650       for (i = 0; i < tokensetsize; i++)
 651         shiftset[i] = 0;
 652
 653       if (shiftp)
 654         {
 655           k = shiftp->nshifts;
 656           for (i = 0; i < k; i++)
 657             {
 658               if (!shiftp->shifts[i])
 659                 continue;
 660               symbol = accessing_symbol[shiftp->shifts[i]];
 661               if (ISVAR (symbol))
 662                 break;
 663               SETBIT (shiftset, symbol);
 664             }
 665         }
 666
 667       mask = 1;
 668       fp1 = LA + m * tokensetsize;
 669       fp2 = shiftset;
 670       for (i = 0; i < ntokens; i++)
 671         {
 672           int defaulted = 0;
 673
 674           if (mask & *fp2)
 675             count = 1;
 676           else
 677             count = 0;
 678
 679           fp3 = fp1;
 680           for (j = m; j < n; j++)
 681             {
 682               if (mask & *fp3)
 683                 {
 684                   if (count == 0)
 685                     {
 686                       if (j != default_LA)
 687                         {
 688                           rule = LAruleno[j];
 689                           obstack_fgrow3 (&output_obstack,
 690                                    _("    %-4s\treduce using rule %d (%s)\n"),
 691                                    tags[i], rule, tags[rlhs[rule]]);
 692                         }
 693                       else
 694                         defaulted = 1;
 695
 696                       count++;
 697                     }
 698                   else
 699                     {
 700                       if (defaulted)
 701                         {
 702                           rule = LAruleno[default_LA];
 703                           obstack_fgrow3 (&output_obstack,
 704                                    _("    %-4s\treduce using rule %d (%s)\n"),
 705                                    tags[i], rule, tags[rlhs[rule]]);
 706                           defaulted = 0;
 707                         }
 708                       rule = LAruleno[j];
 709                       obstack_fgrow3 (&output_obstack,
 710                                _("    %-4s\t[reduce using rule %d (%s)]\n"),
 711                                tags[i], rule, tags[rlhs[rule]]);
 712                     }
 713                 }
 714
 715               fp3 += tokensetsize;
 716             }
 717
 718           mask <<= 1;
 719           if (mask == 0)
 720             {
 721               mask = 1;
 722               /* We tried incrementing just fp1, and just fp2; both seem wrong.
 723                  It seems necessary to increment both in sync.  */
 724               fp1++;
 725               fp2++;
 726             }
 727         }
 728
 729       if (default_LA >= 0)
 730         obstack_fgrow2 (&output_obstack,
 731                         _("    $default\treduce using rule %d (%s)\n"),
 732                         default_rule, tags[rlhs[default_rule]]);
 733
 734       obstack_1grow (&output_obstack, '\n');
 735     }
 736 }
 737
 738
 739 void
 740 free_conflicts (void)
 741 {
 742   XFREE (conflicts);
 743   XFREE (shiftset);
 744   XFREE (lookaheadset);
 745 }