src/conflicts.c

   1 /* Find and resolve or report look-ahead conflicts for bison,
   2    Copyright 1984, 1989, 1992, 2000 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;
  34 int expected_conflicts;
  35 static char *conflicts;
  36
  37 static unsigned *shiftset;
  38 static unsigned *lookaheadset;
  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 initialize_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     sprintf (cp, _(" 1 shift/reduce conflict"));
 422   else if (src_num > 1)
 423     sprintf (cp, _(" %d shift/reduce conflicts"), src_num);
 424   cp += strlen (cp);
 425
 426   if (src_num > 0 && rrc_num > 0)
 427     sprintf (cp, _(" and"));
 428   cp += strlen (cp);
 429
 430   if (rrc_num == 1)
 431     sprintf (cp, _(" 1 reduce/reduce conflict"));
 432   else if (rrc_num > 1)
 433     sprintf (cp, _(" %d reduce/reduce conflicts"), rrc_num);
 434   cp += strlen (cp);
 435
 436   *cp++ = '.';
 437   *cp++ = '\n';
 438   *cp++ = '\0';
 439
 440   return res;
 441 }
 442
 443
 444 /*---------------------------------------------.
 445 | Compute and give a report on the conflicts.  |
 446 `---------------------------------------------*/
 447
 448 void
 449 print_conflicts (void)
 450 {
 451   int i;
 452
 453   src_total = 0;
 454   rrc_total = 0;
 455
 456   /* Count the total number of conflicts, and if wanted, give a
 457      detailed report in FOUTPUT.  */
 458   for (i = 0; i < nstates; i++)
 459     {
 460       if (conflicts[i])
 461         {
 462           count_sr_conflicts (i);
 463           count_rr_conflicts (i);
 464           src_total += src_count;
 465           rrc_total += rrc_count;
 466
 467           if (verbose_flag)
 468             {
 469               obstack_fgrow1 (&output_obstack, _("State %d contains"), i);
 470               obstack_sgrow (&output_obstack,
 471                              conflict_report (src_count, rrc_count));
 472             }
 473         }
 474     }
 475
 476   /* Report the total number of conflicts on STDERR.  */
 477   if (yacc_flag)
 478     {
 479       /* If invoked with `--yacc', use the output format specified by
 480          POSIX.  */
 481       fprintf (stderr, _("conflicts: "));
 482       if (src_total > 0)
 483         fprintf (stderr, _(" %d shift/reduce"), src_total);
 484       if (src_total > 0 && rrc_total > 0)
 485         fprintf (stderr, ",");
 486       if (rrc_total > 0)
 487         fprintf (stderr, _(" %d reduce/reduce"), rrc_total);
 488       putc ('\n', stderr);
 489     }
 490   else
 491     {
 492       fprintf (stderr, _("%s contains"), infile);
 493       fputs (conflict_report (src_total, rrc_total), stderr);
 494     }
 495 }
 496
 497
 498 void
 499 print_reductions (int state)
 500 {
 501   int i;
 502   int j;
 503   int k;
 504   unsigned *fp1;
 505   unsigned *fp2;
 506   unsigned *fp3;
 507   unsigned *fp4;
 508   int rule;
 509   int symbol;
 510   unsigned mask;
 511   int m;
 512   int n;
 513   int default_LA;
 514   int default_rule = 0;
 515   int cmax;
 516   int count;
 517   shifts *shiftp;
 518   errs *errp;
 519   int nodefault = 0;
 520
 521   for (i = 0; i < tokensetsize; i++)
 522     shiftset[i] = 0;
 523
 524   shiftp = shift_table[state];
 525   if (shiftp)
 526     {
 527       k = shiftp->nshifts;
 528       for (i = 0; i < k; i++)
 529         {
 530           if (!shiftp->shifts[i])
 531             continue;
 532           symbol = accessing_symbol[shiftp->shifts[i]];
 533           if (ISVAR (symbol))
 534             break;
 535           /* if this state has a shift for the error token,
 536              don't use a default rule.  */
 537           if (symbol == error_token_number)
 538             nodefault = 1;
 539           SETBIT (shiftset, symbol);
 540         }
 541     }
 542
 543   errp = err_table[state];
 544   if (errp)
 545     {
 546       k = errp->nerrs;
 547       for (i = 0; i < k; i++)
 548         {
 549           if (!errp->errs[i])
 550             continue;
 551           symbol = errp->errs[i];
 552           SETBIT (shiftset, symbol);
 553         }
 554     }
 555
 556   m = lookaheads[state];
 557   n = lookaheads[state + 1];
 558
 559   if (n - m == 1 && !nodefault)
 560     {
 561       default_rule = LAruleno[m];
 562
 563       fp1 = LA + m * tokensetsize;
 564       fp2 = shiftset;
 565       fp3 = lookaheadset;
 566       fp4 = lookaheadset + tokensetsize;
 567
 568       while (fp3 < fp4)
 569         *fp3++ = *fp1++ & *fp2++;
 570
 571       mask = 1;
 572       fp3 = lookaheadset;
 573
 574       for (i = 0; i < ntokens; i++)
 575         {
 576           if (mask & *fp3)
 577             obstack_fgrow3 (&output_obstack,
 578                             _("    %-4s\t[reduce using rule %d (%s)]\n"),
 579                             tags[i], default_rule, tags[rlhs[default_rule]]);
 580
 581           mask <<= 1;
 582           if (mask == 0)
 583             {
 584               mask = 1;
 585               fp3++;
 586             }
 587         }
 588
 589       obstack_fgrow2 (&output_obstack,
 590                       _("    $default\treduce using rule %d (%s)\n\n"),
 591                       default_rule, tags[rlhs[default_rule]]);
 592     }
 593   else if (n - m >= 1)
 594     {
 595       cmax = 0;
 596       default_LA = -1;
 597       fp4 = lookaheadset + tokensetsize;
 598
 599       if (!nodefault)
 600         for (i = m; i < n; i++)
 601           {
 602             fp1 = LA + i * tokensetsize;
 603             fp2 = shiftset;
 604             fp3 = lookaheadset;
 605
 606             while (fp3 < fp4)
 607               *fp3++ = *fp1++ & (~(*fp2++));
 608
 609             count = 0;
 610             mask = 1;
 611             fp3 = lookaheadset;
 612             for (j = 0; j < ntokens; j++)
 613               {
 614                 if (mask & *fp3)
 615                   count++;
 616
 617                 mask <<= 1;
 618                 if (mask == 0)
 619                   {
 620                     mask = 1;
 621                     fp3++;
 622                   }
 623               }
 624
 625             if (count > cmax)
 626               {
 627                 cmax = count;
 628                 default_LA = i;
 629                 default_rule = LAruleno[i];
 630               }
 631
 632             fp2 = shiftset;
 633             fp3 = lookaheadset;
 634
 635             while (fp3 < fp4)
 636               *fp2++ |= *fp3++;
 637           }
 638
 639       for (i = 0; i < tokensetsize; i++)
 640         shiftset[i] = 0;
 641
 642       if (shiftp)
 643         {
 644           k = shiftp->nshifts;
 645           for (i = 0; i < k; i++)
 646             {
 647               if (!shiftp->shifts[i])
 648                 continue;
 649               symbol = accessing_symbol[shiftp->shifts[i]];
 650               if (ISVAR (symbol))
 651                 break;
 652               SETBIT (shiftset, symbol);
 653             }
 654         }
 655
 656       mask = 1;
 657       fp1 = LA + m * tokensetsize;
 658       fp2 = shiftset;
 659       for (i = 0; i < ntokens; i++)
 660         {
 661           int defaulted = 0;
 662
 663           if (mask & *fp2)
 664             count = 1;
 665           else
 666             count = 0;
 667
 668           fp3 = fp1;
 669           for (j = m; j < n; j++)
 670             {
 671               if (mask & *fp3)
 672                 {
 673                   if (count == 0)
 674                     {
 675                       if (j != default_LA)
 676                         {
 677                           rule = LAruleno[j];
 678                           obstack_fgrow3 (&output_obstack,
 679                                    _("    %-4s\treduce using rule %d (%s)\n"),
 680                                    tags[i], rule, tags[rlhs[rule]]);
 681                         }
 682                       else
 683                         defaulted = 1;
 684
 685                       count++;
 686                     }
 687                   else
 688                     {
 689                       if (defaulted)
 690                         {
 691                           rule = LAruleno[default_LA];
 692                           obstack_fgrow3 (&output_obstack,
 693                                    _("    %-4s\treduce using rule %d (%s)\n"),
 694                                    tags[i], rule, tags[rlhs[rule]]);
 695                           defaulted = 0;
 696                         }
 697                       rule = LAruleno[j];
 698                       obstack_fgrow3 (&output_obstack,
 699                                _("    %-4s\t[reduce using rule %d (%s)]\n"),
 700                                tags[i], rule, tags[rlhs[rule]]);
 701                     }
 702                 }
 703
 704               fp3 += tokensetsize;
 705             }
 706
 707           mask <<= 1;
 708           if (mask == 0)
 709             {
 710               mask = 1;
 711               /* We tried incrementing just fp1, and just fp2; both seem wrong.
 712                  It seems necessary to increment both in sync.  */
 713               fp1++;
 714               fp2++;
 715             }
 716         }
 717
 718       if (default_LA >= 0)
 719         obstack_fgrow2 (&output_obstack,
 720                         _("    $default\treduce using rule %d (%s)\n"),
 721                         default_rule, tags[rlhs[default_rule]]);
 722
 723       obstack_1grow (&output_obstack, '\n');
 724     }
 725 }
 726
 727
 728 void
 729 finalize_conflicts (void)
 730 {
 731   XFREE (conflicts);
 732   XFREE (shiftset);
 733   XFREE (lookaheadset);
 734 }