1 /* 2 * [The "BSD license"] 3 * Copyright (c) 2010 Terence Parr 4 * All rights reserved. 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 1. Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 3. The name of the author may not be used to endorse or promote products 15 * derived from this software without specific prior written permission. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 18 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 19 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 20 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 21 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 22 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 26 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 27 */ 28 package org.antlr.analysis; 29 30 import org.antlr.misc.OrderedHashSet; 31 import org.antlr.misc.Utils; 32 import org.antlr.runtime.Token; 33 import org.antlr.tool.ErrorManager; 34 35 import java.util.*; 36 37 /** Code that embodies the NFA conversion to DFA. A new object is needed 38 * per DFA (also required for thread safety if multiple conversions 39 * launched). 40 */ 41 public class NFAToDFAConverter { 42 /** A list of DFA states we still need to process during NFA conversion */ 43 protected List<DFAState> work = new LinkedList<DFAState>(); 44 45 /** While converting NFA, we must track states that 46 * reference other rule's NFAs so we know what to do 47 * at the end of a rule. We need to know what context invoked 48 * this rule so we can know where to continue looking for NFA 49 * states. I'm tracking a context tree (record of rule invocation 50 * stack trace) for each alternative that could be predicted. 51 */ 52 protected NFAContext[] contextTrees; 53 54 /** We are converting which DFA? */ 55 protected DFA dfa; 56 57 public static boolean debug = false; 58 59 /** Should ANTLR launch multiple threads to convert NFAs to DFAs? 60 * With a 2-CPU box, I note that it's about the same single or 61 * multithreaded. Both CPU meters are going even when single-threaded 62 * so I assume the GC is killing us. Could be the compiler. When I 63 * run java -Xint mode, I get about 15% speed improvement with multiple 64 * threads. 65 */ 66 public static boolean SINGLE_THREADED_NFA_CONVERSION = true; 67 68 protected boolean computingStartState = false; 69 70 public NFAToDFAConverter(DFA dfa) { 71 this.dfa = dfa; 72 int nAlts = dfa.getNumberOfAlts(); 73 initContextTrees(nAlts); 74 } 75 76 public void convert() { 77 //dfa.conversionStartTime = System.currentTimeMillis(); 78 79 // create the DFA start state 80 dfa.startState = computeStartState(); 81 82 // while more DFA states to check, process them 83 while ( work.size()>0 && 84 !dfa.nfa.grammar.NFAToDFAConversionExternallyAborted() ) 85 { 86 DFAState d = work.get(0); 87 if ( dfa.nfa.grammar.composite.watchNFAConversion ) { 88 System.out.println("convert DFA state "+d.stateNumber+ 89 " ("+d.nfaConfigurations.size()+" nfa states)"); 90 } 91 int k = dfa.getUserMaxLookahead(); 92 if ( k>0 && k==d.getLookaheadDepth() ) { 93 // we've hit max lookahead, make this a stop state 94 //System.out.println("stop state @k="+k+" (terminated early)"); 95 /* 96 List<Label> sampleInputLabels = d.dfa.probe.getSampleNonDeterministicInputSequence(d); 97 String input = d.dfa.probe.getInputSequenceDisplay(sampleInputLabels); 98 System.out.println("sample input: "+input); 99 */ 100 resolveNonDeterminisms(d); 101 // Check to see if we need to add any semantic predicate transitions 102 if ( d.isResolvedWithPredicates() ) { 103 addPredicateTransitions(d); 104 } 105 else { 106 d.setAcceptState(true); // must convert to accept state at k 107 } 108 } 109 else { 110 findNewDFAStatesAndAddDFATransitions(d); 111 } 112 work.remove(0); // done with it; remove from work list 113 } 114 115 // Find all manual syn preds (gated). These are not discovered 116 // in tryToResolveWithSemanticPredicates because they are implicitly 117 // added to every edge by code gen, DOT generation etc... 118 dfa.findAllGatedSynPredsUsedInDFAAcceptStates(); 119 } 120 121 /** From this first NFA state of a decision, create a DFA. 122 * Walk each alt in decision and compute closure from the start of that 123 * rule, making sure that the closure does not include other alts within 124 * that same decision. The idea is to associate a specific alt number 125 * with the starting closure so we can trace the alt number for all states 126 * derived from this. At a stop state in the DFA, we can return this alt 127 * number, indicating which alt is predicted. 128 * 129 * If this DFA is derived from an loop back NFA state, then the first 130 * transition is actually the exit branch of the loop. Rather than make 131 * this alternative one, let's make this alt n+1 where n is the number of 132 * alts in this block. This is nice to keep the alts of the block 1..n; 133 * helps with error messages. 134 * 135 * I handle nongreedy in findNewDFAStatesAndAddDFATransitions 136 * when nongreedy and EOT transition. Make state with EOT emanating 137 * from it the accept state. 138 */ 139 protected DFAState computeStartState() { 140 NFAState alt = dfa.decisionNFAStartState; 141 DFAState startState = dfa.newState(); 142 computingStartState = true; 143 int i = 0; 144 int altNum = 1; 145 while ( alt!=null ) { 146 // find the set of NFA states reachable without consuming 147 // any input symbols for each alt. Keep adding to same 148 // overall closure that will represent the DFA start state, 149 // but track the alt number 150 NFAContext initialContext = contextTrees[i]; 151 // if first alt is derived from loopback/exit branch of loop, 152 // make alt=n+1 for n alts instead of 1 153 if ( i==0 && 154 dfa.getNFADecisionStartState().decisionStateType==NFAState.LOOPBACK ) 155 { 156 int numAltsIncludingExitBranch = dfa.nfa.grammar 157 .getNumberOfAltsForDecisionNFA(dfa.decisionNFAStartState); 158 altNum = numAltsIncludingExitBranch; 159 closure((NFAState)alt.transition[0].target, 160 altNum, 161 initialContext, 162 SemanticContext.EMPTY_SEMANTIC_CONTEXT, 163 startState, 164 true 165 ); 166 altNum = 1; // make next alt the first 167 } 168 else { 169 closure((NFAState)alt.transition[0].target, 170 altNum, 171 initialContext, 172 SemanticContext.EMPTY_SEMANTIC_CONTEXT, 173 startState, 174 true 175 ); 176 altNum++; 177 } 178 i++; 179 180 // move to next alternative 181 if ( alt.transition[1] ==null ) { 182 break; 183 } 184 alt = (NFAState)alt.transition[1].target; 185 } 186 187 // now DFA start state has the complete closure for the decision 188 // but we have tracked which alt is associated with which 189 // NFA states. 190 dfa.addState(startState); // make sure dfa knows about this state 191 work.add(startState); 192 computingStartState = false; 193 return startState; 194 } 195 196 /** From this node, add a d--a-->t transition for all 197 * labels 'a' where t is a DFA node created 198 * from the set of NFA states reachable from any NFA 199 * state in DFA state d. 200 */ 201 protected void findNewDFAStatesAndAddDFATransitions(DFAState d) { 202 //System.out.println("work on DFA state "+d); 203 OrderedHashSet<Label> labels = d.getReachableLabels(); 204 //System.out.println("reachable labels="+labels); 205 206 /* 207 System.out.println("|reachable|/|nfaconfigs|="+ 208 labels.size()+"/"+d.getNFAConfigurations().size()+"="+ 209 labels.size()/(float)d.getNFAConfigurations().size()); 210 */ 211 212 // normally EOT is the "default" clause and decisions just 213 // choose that last clause when nothing else matches. DFA conversion 214 // continues searching for a unique sequence that predicts the 215 // various alts or until it finds EOT. So this rule 216 // 217 // DUH : ('x'|'y')* "xy!"; 218 // 219 // does not need a greedy indicator. The following rule works fine too 220 // 221 // A : ('x')+ ; 222 // 223 // When the follow branch could match what is in the loop, by default, 224 // the nondeterminism is resolved in favor of the loop. You don't 225 // get a warning because the only way to get this condition is if 226 // the DFA conversion hits the end of the token. In that case, 227 // we're not *sure* what will happen next, but it could be anything. 228 // Anyway, EOT is the default case which means it will never be matched 229 // as resolution goes to the lowest alt number. Exit branches are 230 // always alt n+1 for n alts in a block. 231 // 232 // When a loop is nongreedy and we find an EOT transition, the DFA 233 // state should become an accept state, predicting exit of loop. It's 234 // just reversing the resolution of ambiguity. 235 // TODO: should this be done in the resolveAmbig method? 236 Label EOTLabel = new Label(Label.EOT); 237 boolean containsEOT = labels!=null && labels.contains(EOTLabel); 238 if ( !dfa.isGreedy() && containsEOT ) { 239 convertToEOTAcceptState(d); 240 return; // no more work to do on this accept state 241 } 242 243 // if in filter mode for lexer, want to match shortest not longest 244 // string so if we see an EOT edge emanating from this state, then 245 // convert this state to an accept state. This only counts for 246 // The Tokens rule as all other decisions must continue to look for 247 // longest match. 248 // [Taking back out a few days later on Jan 17, 2006. This could 249 // be an option for the future, but this was wrong soluion for 250 // filtering.] 251 /* 252 if ( dfa.nfa.grammar.type==Grammar.LEXER && containsEOT ) { 253 String filterOption = (String)dfa.nfa.grammar.getOption("filter"); 254 boolean filterMode = filterOption!=null && filterOption.equals("true"); 255 if ( filterMode && d.dfa.isTokensRuleDecision() ) { 256 DFAState t = reach(d, EOTLabel); 257 if ( t.getNFAConfigurations().size()>0 ) { 258 convertToEOTAcceptState(d); 259 //System.out.println("state "+d+" has EOT target "+t.stateNumber); 260 return; 261 } 262 } 263 } 264 */ 265 266 int numberOfEdgesEmanating = 0; 267 Map<Integer, Transition> targetToLabelMap = new HashMap<Integer, Transition>(); 268 // for each label that could possibly emanate from NFAStates of d 269 int numLabels = 0; 270 if ( labels!=null ) { 271 numLabels = labels.size(); 272 } 273 for (int i=0; i<numLabels; i++) { 274 Label label = labels.get(i); 275 DFAState t = reach(d, label); 276 if ( debug ) { 277 System.out.println("DFA state after reach "+label+" "+d+"-" + 278 label.toString(dfa.nfa.grammar)+"->"+t); 279 } 280 if ( t==null ) { 281 // nothing was reached by label due to conflict resolution 282 // EOT also seems to be in here occasionally probably due 283 // to an end-of-rule state seeing it even though we'll pop 284 // an invoking state off the state; don't bother to conflict 285 // as this labels set is a covering approximation only. 286 continue; 287 } 288 //System.out.println("dfa.k="+dfa.getUserMaxLookahead()); 289 if ( t.getUniqueAlt()==NFA.INVALID_ALT_NUMBER ) { 290 // Only compute closure if a unique alt number is not known. 291 // If a unique alternative is mentioned among all NFA 292 // configurations then there is no possibility of needing to look 293 // beyond this state; also no possibility of a nondeterminism. 294 // This optimization May 22, 2006 just dropped -Xint time 295 // for analysis of Java grammar from 11.5s to 2s! Wow. 296 closure(t); // add any NFA states reachable via epsilon 297 } 298 299 /* 300 System.out.println("DFA state after closure "+d+"-"+ 301 label.toString(dfa.nfa.grammar)+ 302 "->"+t); 303 */ 304 305 // add if not in DFA yet and then make d-label->t 306 DFAState targetState = addDFAStateToWorkList(t); 307 308 numberOfEdgesEmanating += 309 addTransition(d, label, targetState, targetToLabelMap); 310 311 // lookahead of target must be one larger than d's k 312 // We are possibly setting the depth of a pre-existing state 313 // that is equal to one we just computed...not sure if that's 314 // ok. 315 targetState.setLookaheadDepth(d.getLookaheadDepth() + 1); 316 } 317 318 //System.out.println("DFA after reach / closures:\n"+dfa); 319 if ( !d.isResolvedWithPredicates() && numberOfEdgesEmanating==0 ) { 320 //System.out.println("dangling DFA state "+d+"\nAfter reach / closures:\n"+dfa); 321 // TODO: can fixed lookahead hit a dangling state case? 322 // TODO: yes, with left recursion 323 //System.err.println("dangling state alts: "+d.getAltSet()); 324 dfa.probe.reportDanglingState(d); 325 // turn off all configurations except for those associated with 326 // min alt number; somebody has to win else some input will not 327 // predict any alt. 328 int minAlt = resolveByPickingMinAlt(d, null); 329 // force it to be an accept state 330 // don't call convertToAcceptState() which merges stop states. 331 // other states point at us; don't want them pointing to dead states 332 d.setAcceptState(true); // might be adding new accept state for alt 333 dfa.setAcceptState(minAlt, d); 334 //convertToAcceptState(d, minAlt); // force it to be an accept state 335 } 336 337 // Check to see if we need to add any semantic predicate transitions 338 // might have both token and predicated edges from d 339 if ( d.isResolvedWithPredicates() ) { 340 addPredicateTransitions(d); 341 } 342 } 343 344 /** Add a transition from state d to targetState with label in normal case. 345 * if COLLAPSE_ALL_INCIDENT_EDGES, however, try to merge all edges from 346 * d to targetState; this means merging their labels. Another optimization 347 * is to reduce to a single EOT edge any set of edges from d to targetState 348 * where there exists an EOT state. EOT is like the wildcard so don't 349 * bother to test any other edges. Example: 350 * 351 * NUM_INT 352 * : '1'..'9' ('0'..'9')* ('l'|'L')? 353 * | '0' ('x'|'X') ('0'..'9'|'a'..'f'|'A'..'F')+ ('l'|'L')? 354 * | '0' ('0'..'7')* ('l'|'L')? 355 * ; 356 * 357 * The normal decision to predict alts 1, 2, 3 is: 358 * 359 * if ( (input.LA(1)>='1' && input.LA(1)<='9') ) { 360 * alt7=1; 361 * } 362 * else if ( input.LA(1)=='0' ) { 363 * if ( input.LA(2)=='X'||input.LA(2)=='x' ) { 364 * alt7=2; 365 * } 366 * else if ( (input.LA(2)>='0' && input.LA(2)<='7') ) { 367 * alt7=3; 368 * } 369 * else if ( input.LA(2)=='L'||input.LA(2)=='l' ) { 370 * alt7=3; 371 * } 372 * else { 373 * alt7=3; 374 * } 375 * } 376 * else error 377 * 378 * Clearly, alt 3 is predicted with extra work since it tests 0..7 379 * and [lL] before finally realizing that any character is actually 380 * ok at k=2. 381 * 382 * A better decision is as follows: 383 * 384 * if ( (input.LA(1)>='1' && input.LA(1)<='9') ) { 385 * alt7=1; 386 * } 387 * else if ( input.LA(1)=='0' ) { 388 * if ( input.LA(2)=='X'||input.LA(2)=='x' ) { 389 * alt7=2; 390 * } 391 * else { 392 * alt7=3; 393 * } 394 * } 395 * 396 * The DFA originally has 3 edges going to the state the predicts alt 3, 397 * but upon seeing the EOT edge (the "else"-clause), this method 398 * replaces the old merged label (which would have (0..7|l|L)) with EOT. 399 * The code generator then leaves alt 3 predicted with a simple else- 400 * clause. :) 401 * 402 * The only time the EOT optimization makes no sense is in the Tokens 403 * rule. We want EOT to truly mean you have matched an entire token 404 * so don't bother actually rewinding to execute that rule unless there 405 * are actions in that rule. For now, since I am not preventing 406 * backtracking from Tokens rule, I will simply allow the optimization. 407 */ 408 protected static int addTransition(DFAState d, 409 Label label, 410 DFAState targetState, 411 Map<Integer, Transition> targetToLabelMap) 412 { 413 //System.out.println(d.stateNumber+"-"+label.toString(dfa.nfa.grammar)+"->"+targetState.stateNumber); 414 int n = 0; 415 if ( DFAOptimizer.COLLAPSE_ALL_PARALLEL_EDGES ) { 416 // track which targets we've hit 417 Integer tI = Utils.integer(targetState.stateNumber); 418 Transition oldTransition = targetToLabelMap.get(tI); 419 if ( oldTransition!=null ) { 420 //System.out.println("extra transition to "+tI+" upon "+label.toString(dfa.nfa.grammar)); 421 // already seen state d to target transition, just add label 422 // to old label unless EOT 423 if ( label.getAtom()==Label.EOT ) { 424 // merge with EOT means old edge can go away 425 oldTransition.label = new Label(Label.EOT); 426 } 427 else { 428 // don't add anything to EOT, it's essentially the wildcard 429 if ( oldTransition.label.getAtom()!=Label.EOT ) { 430 // ok, not EOT, add in this label to old label 431 oldTransition.label.add(label); 432 } 433 //System.out.println("label updated to be "+oldTransition.label.toString(dfa.nfa.grammar)); 434 } 435 } 436 else { 437 // make a transition from d to t upon 'a' 438 n = 1; 439 label = (Label)label.clone(); // clone in case we alter later 440 int transitionIndex = d.addTransition(targetState, label); 441 Transition trans = d.getTransition(transitionIndex); 442 // track target/transition pairs 443 targetToLabelMap.put(tI, trans); 444 } 445 } 446 else { 447 n = 1; 448 d.addTransition(targetState, label); 449 } 450 return n; 451 } 452 453 /** For all NFA states (configurations) merged in d, 454 * compute the epsilon closure; that is, find all NFA states reachable 455 * from the NFA states in d via purely epsilon transitions. 456 */ 457 public void closure(DFAState d) { 458 if ( debug ) { 459 System.out.println("closure("+d+")"); 460 } 461 462 List<NFAConfiguration> configs = new ArrayList<NFAConfiguration>(); 463 // Because we are adding to the configurations in closure 464 // must clone initial list so we know when to stop doing closure 465 configs.addAll(d.nfaConfigurations); 466 // for each NFA configuration in d (abort if we detect non-LL(*) state) 467 int numConfigs = configs.size(); 468 for (int i = 0; i < numConfigs; i++) { 469 NFAConfiguration c = configs.get(i); 470 if ( c.singleAtomTransitionEmanating ) { 471 continue; // ignore NFA states w/o epsilon transitions 472 } 473 //System.out.println("go do reach for NFA state "+c.state); 474 // figure out reachable NFA states from each of d's nfa states 475 // via epsilon transitions. 476 // Fill configsInClosure rather than altering d configs inline 477 closure(dfa.nfa.getState(c.state), 478 c.alt, 479 c.context, 480 c.semanticContext, 481 d, 482 false); 483 } 484 //System.out.println("after closure d="+d); 485 d.closureBusy = null; // wack all that memory used during closure 486 } 487 488 /** Where can we get from NFA state p traversing only epsilon transitions? 489 * Add new NFA states + context to DFA state d. Also add semantic 490 * predicates to semantic context if collectPredicates is set. We only 491 * collect predicates at hoisting depth 0, meaning before any token/char 492 * have been recognized. This corresponds, during analysis, to the 493 * initial DFA start state construction closure() invocation. 494 * 495 * There are four cases of interest (the last being the usual transition): 496 * 497 * 1. Traverse an edge that takes us to the start state of another 498 * rule, r. We must push this state so that if the DFA 499 * conversion hits the end of rule r, then it knows to continue 500 * the conversion at state following state that "invoked" r. By 501 * construction, there is a single transition emanating from a rule 502 * ref node. 503 * 504 * 2. Reach an NFA state associated with the end of a rule, r, in the 505 * grammar from which it was built. We must add an implicit (i.e., 506 * don't actually add an epsilon transition) epsilon transition 507 * from r's end state to the NFA state following the NFA state 508 * that transitioned to rule r's start state. Because there are 509 * many states that could reach r, the context for a rule invocation 510 * is part of a call tree not a simple stack. When we fall off end 511 * of rule, "pop" a state off the call tree and add that state's 512 * "following" node to d's NFA configuration list. The context 513 * for this new addition will be the new "stack top" in the call tree. 514 * 515 * 3. Like case 2, we reach an NFA state associated with the end of a 516 * rule, r, in the grammar from which NFA was built. In this case, 517 * however, we realize that during this NFA→DFA conversion, no state 518 * invoked the current rule's NFA. There is no choice but to add 519 * all NFA states that follow references to r's start state. This is 520 * analogous to computing the FOLLOW(r) in the LL(k) world. By 521 * construction, even rule stop state has a chain of nodes emanating 522 * from it that points to every possible following node. This case 523 * is conveniently handled then by the 4th case. 524 * 525 * 4. Normal case. If p can reach another NFA state q, then add 526 * q to d's configuration list, copying p's context for q's context. 527 * If there is a semantic predicate on the transition, then AND it 528 * with any existing semantic context. 529 * 530 * Current state p is always added to d's configuration list as it's part 531 * of the closure as well. 532 * 533 * When is a closure operation in a cycle condition? While it is 534 * very possible to have the same NFA state mentioned twice 535 * within the same DFA state, there are two situations that 536 * would lead to nontermination of closure operation: 537 * 538 * o Whenever closure reaches a configuration where the same state 539 * with same or a suffix context already exists. This catches 540 * the IF-THEN-ELSE tail recursion cycle and things like 541 * 542 * a : A a | B ; 543 * 544 * the context will be $ (empty stack). 545 * 546 * We have to check 547 * larger context stacks because of (...)+ loops. For 548 * example, the context of a (...)+ can be nonempty if the 549 * surrounding rule is invoked by another rule: 550 * 551 * a : b A | X ; 552 * b : (B|)+ ; // nondeterministic by the way 553 * 554 * The context of the (B|)+ loop is "invoked from item 555 * a : . b A ;" and then the empty alt of the loop can reach back 556 * to itself. The context stack will have one "return 557 * address" element and so we must check for same state, same 558 * context for arbitrary context stacks. 559 * 560 * Idea: If we've seen this configuration before during closure, stop. 561 * We also need to avoid reaching same state with conflicting context. 562 * Ultimately analysis would stop and we'd find the conflict, but we 563 * should stop the computation. Previously I only checked for 564 * exact config. Need to check for same state, suffix context 565 * not just exact context. 566 * 567 * o Whenever closure reaches a configuration where state p 568 * is present in its own context stack. This means that 569 * p is a rule invocation state and the target rule has 570 * been called before. NFAContext.MAX_RECURSIVE_INVOCATIONS 571 * (See the comment there also) determines how many times 572 * it's possible to recurse; clearly we cannot recurse forever. 573 * Some grammars such as the following actually require at 574 * least one recursive call to correctly compute the lookahead: 575 * 576 * a : L ID R 577 * | b 578 * ; 579 * b : ID 580 * | L a R 581 * ; 582 * 583 * Input L ID R is ambiguous but to figure this out, ANTLR 584 * needs to go a->b->a->b to find the L ID sequence. 585 * 586 * Do not allow closure to add a configuration that would 587 * allow too much recursion. 588 * 589 * This case also catches infinite left recursion. 590 */ 591 public void closure(NFAState p, 592 int alt, 593 NFAContext context, 594 SemanticContext semanticContext, 595 DFAState d, 596 boolean collectPredicates) 597 { 598 if ( debug ){ 599 System.out.println("closure at "+p.enclosingRule.name+" state "+p.stateNumber+"|"+ 600 alt+" filling DFA state "+d.stateNumber+" with context "+context 601 ); 602 } 603 604 // if ( DFA.MAX_TIME_PER_DFA_CREATION>0 && 605 // System.currentTimeMillis() - d.dfa.conversionStartTime >= 606 // DFA.MAX_TIME_PER_DFA_CREATION ) 607 // { 608 // // bail way out; we've blown up somehow 609 // throw new AnalysisTimeoutException(d.dfa); 610 // } 611 612 NFAConfiguration proposedNFAConfiguration = 613 new NFAConfiguration(p.stateNumber, 614 alt, 615 context, 616 semanticContext); 617 618 // Avoid infinite recursion 619 if ( closureIsBusy(d, proposedNFAConfiguration) ) { 620 if ( debug ) { 621 System.out.println("avoid visiting exact closure computation NFA config: "+ 622 proposedNFAConfiguration+" in "+p.enclosingRule.name); 623 System.out.println("state is "+d.dfa.decisionNumber+"."+d.stateNumber); 624 } 625 return; 626 } 627 628 // set closure to be busy for this NFA configuration 629 d.closureBusy.add(proposedNFAConfiguration); 630 631 // p itself is always in closure 632 d.addNFAConfiguration(p, proposedNFAConfiguration); 633 634 // Case 1: are we a reference to another rule? 635 Transition transition0 = p.transition[0]; 636 if ( transition0 instanceof RuleClosureTransition ) { 637 int depth = context.recursionDepthEmanatingFromState(p.stateNumber); 638 // Detect recursion by more than a single alt, which indicates 639 // that the decision's lookahead language is potentially non-regular; terminate 640 if ( depth == 1 && d.dfa.getUserMaxLookahead()==0 ) { // k=* only 641 d.dfa.recursiveAltSet.add(alt); // indicate that this alt is recursive 642 if ( d.dfa.recursiveAltSet.size()>1 ) { 643 //System.out.println("recursive alts: "+d.dfa.recursiveAltSet.toString()); 644 d.abortedDueToMultipleRecursiveAlts = true; 645 throw new NonLLStarDecisionException(d.dfa); 646 } 647 /* 648 System.out.println("alt "+alt+" in rule "+p.enclosingRule+" dec "+d.dfa.decisionNumber+ 649 " ctx: "+context); 650 System.out.println("d="+d); 651 */ 652 } 653 // Detect an attempt to recurse too high 654 // if this context has hit the max recursions for p.stateNumber, 655 // don't allow it to enter p.stateNumber again 656 if ( depth >= NFAContext.MAX_SAME_RULE_INVOCATIONS_PER_NFA_CONFIG_STACK ) { 657 /* 658 System.out.println("OVF state "+d); 659 System.out.println("proposed "+proposedNFAConfiguration); 660 */ 661 d.abortedDueToRecursionOverflow = true; 662 d.dfa.probe.reportRecursionOverflow(d, proposedNFAConfiguration); 663 if ( debug ) { 664 System.out.println("analysis overflow in closure("+d.stateNumber+")"); 665 } 666 return; 667 } 668 669 // otherwise, it's cool to (re)enter target of this rule ref 670 RuleClosureTransition ref = (RuleClosureTransition)transition0; 671 // first create a new context and push onto call tree, 672 // recording the fact that we are invoking a rule and 673 // from which state (case 2 below will get the following state 674 // via the RuleClosureTransition emanating from the invoking state 675 // pushed on the stack). 676 // Reset the context to reflect the fact we invoked rule 677 NFAContext newContext = new NFAContext(context, p); 678 //System.out.println("invoking rule "+ref.rule.name); 679 // System.out.println(" context="+context); 680 // traverse epsilon edge to new rule 681 NFAState ruleTarget = (NFAState)ref.target; 682 closure(ruleTarget, alt, newContext, semanticContext, d, collectPredicates); 683 } 684 // Case 2: end of rule state, context (i.e., an invoker) exists 685 else if ( p.isAcceptState() && context.parent!=null ) { 686 NFAState whichStateInvokedRule = context.invokingState; 687 RuleClosureTransition edgeToRule = 688 (RuleClosureTransition)whichStateInvokedRule.transition[0]; 689 NFAState continueState = edgeToRule.followState; 690 NFAContext newContext = context.parent; // "pop" invoking state 691 closure(continueState, alt, newContext, semanticContext, d, collectPredicates); 692 } 693 // Case 3: end of rule state, nobody invoked this rule (no context) 694 // Fall thru to be handled by case 4 automagically. 695 // Case 4: ordinary NFA->DFA conversion case: simple epsilon transition 696 else { 697 // recurse down any epsilon transitions 698 if ( transition0!=null && transition0.isEpsilon() ) { 699 boolean collectPredicatesAfterAction = collectPredicates; 700 if ( transition0.isAction() && collectPredicates ) { 701 collectPredicatesAfterAction = false; 702 /* 703 if ( computingStartState ) { 704 System.out.println("found action during prediction closure "+((ActionLabel)transition0.label).actionAST.token); 705 } 706 */ 707 } 708 closure((NFAState)transition0.target, 709 alt, 710 context, 711 semanticContext, 712 d, 713 collectPredicatesAfterAction 714 ); 715 } 716 else if ( transition0!=null && transition0.isSemanticPredicate() ) { 717 SemanticContext labelContext = transition0.label.getSemanticContext(); 718 if ( computingStartState ) { 719 if ( collectPredicates ) { 720 // only indicate we can see a predicate if we're collecting preds 721 // Could be computing start state & seen an action before this. 722 dfa.predicateVisible = true; 723 } 724 else { 725 // this state has a pred, but we can't see it. 726 dfa.hasPredicateBlockedByAction = true; 727 // System.out.println("found pred during prediction but blocked by action found previously"); 728 } 729 } 730 // continue closure here too, but add the sem pred to ctx 731 SemanticContext newSemanticContext = semanticContext; 732 if ( collectPredicates ) { 733 // AND the previous semantic context with new pred 734 // do not hoist syn preds from other rules; only get if in 735 // starting state's rule (i.e., context is empty) 736 int walkAlt = 737 dfa.decisionNFAStartState.translateDisplayAltToWalkAlt(alt); 738 NFAState altLeftEdge = 739 dfa.nfa.grammar.getNFAStateForAltOfDecision(dfa.decisionNFAStartState,walkAlt); 740 /* 741 System.out.println("state "+p.stateNumber+" alt "+alt+" walkAlt "+walkAlt+" trans to "+transition0.target); 742 System.out.println("DFA start state "+dfa.decisionNFAStartState.stateNumber); 743 System.out.println("alt left edge "+altLeftEdge.stateNumber+ 744 ", epsilon target "+ 745 altLeftEdge.transition(0).target.stateNumber); 746 */ 747 if ( !labelContext.isSyntacticPredicate() || 748 p==altLeftEdge.transition[0].target ) 749 { 750 //System.out.println("&"+labelContext+" enclosingRule="+p.enclosingRule); 751 newSemanticContext = 752 SemanticContext.and(semanticContext, labelContext); 753 } 754 } 755 closure((NFAState)transition0.target, 756 alt, 757 context, 758 newSemanticContext, 759 d, 760 collectPredicates); 761 } 762 Transition transition1 = p.transition[1]; 763 if ( transition1!=null && transition1.isEpsilon() ) { 764 closure((NFAState)transition1.target, 765 alt, 766 context, 767 semanticContext, 768 d, 769 collectPredicates); 770 } 771 } 772 773 // don't remove "busy" flag as we want to prevent all 774 // references to same config of state|alt|ctx|semCtx even 775 // if resulting from another NFA state 776 } 777 778 /** A closure operation should abort if that computation has already 779 * been done or a computation with a conflicting context has already 780 * been done. If proposed NFA config's state and alt are the same 781 * there is potentially a problem. If the stack context is identical 782 * then clearly the exact same computation is proposed. If a context 783 * is a suffix of the other, then again the computation is in an 784 * identical context. ?$ and ??$ are considered the same stack. 785 * We could walk configurations linearly doing the comparison instead 786 * of a set for exact matches but it's much slower because you can't 787 * do a Set lookup. I use exact match as ANTLR 788 * always detect the conflict later when checking for context suffixes... 789 * I check for left-recursive stuff and terminate before analysis to 790 * avoid need to do this more expensive computation. 791 * 792 * 12-31-2007: I had to use the loop again rather than simple 793 * closureBusy.contains(proposedNFAConfiguration) lookup. The 794 * semantic context should not be considered when determining if 795 * a closure operation is busy. I saw a FOLLOW closure operation 796 * spin until time out because the predicate context kept increasing 797 * in size even though it's same boolean value. This seems faster also 798 * because I'm not doing String.equals on the preds all the time. 799 * 800 * 05-05-2008: Hmm...well, i think it was a mistake to remove the sem 801 * ctx check below...adding back in. Coincides with report of ANTLR 802 * getting super slow: http://www.antlr.org:8888/browse/ANTLR-235 803 * This could be because it doesn't properly compute then resolve 804 * a predicate expression. Seems to fix unit test: 805 * TestSemanticPredicates.testSemanticContextPreventsEarlyTerminationOfClosure() 806 * Changing back to Set from List. Changed a large grammar from 8 minutes 807 * to 11 seconds. Cool. Closing ANTLR-235. 808 */ 809 public static boolean closureIsBusy(DFAState d, 810 NFAConfiguration proposedNFAConfiguration) 811 { 812 return d.closureBusy.contains(proposedNFAConfiguration); 813 /* 814 int numConfigs = d.closureBusy.size(); 815 // Check epsilon cycle (same state, same alt, same context) 816 for (int i = 0; i < numConfigs; i++) { 817 NFAConfiguration c = (NFAConfiguration) d.closureBusy.get(i); 818 if ( proposedNFAConfiguration.state==c.state && 819 proposedNFAConfiguration.alt==c.alt && 820 proposedNFAConfiguration.semanticContext.equals(c.semanticContext) && 821 proposedNFAConfiguration.context.suffix(c.context) ) 822 { 823 return true; 824 } 825 } 826 return false; 827 */ 828 } 829 830 /** Given the set of NFA states in DFA state d, find all NFA states 831 * reachable traversing label arcs. By definition, there can be 832 * only one DFA state reachable by an atom from DFA state d so we must 833 * find and merge all NFA states reachable via label. Return a new 834 * DFAState that has all of those NFA states with their context (i.e., 835 * which alt do they predict and where to return to if they fall off 836 * end of a rule). 837 * 838 * Because we cannot jump to another rule nor fall off the end of a rule 839 * via a non-epsilon transition, NFA states reachable from d have the 840 * same configuration as the NFA state in d. So if NFA state 7 in d's 841 * configurations can reach NFA state 13 then 13 will be added to the 842 * new DFAState (labelDFATarget) with the same configuration as state 843 * 7 had. 844 * 845 * This method does not see EOT transitions off the end of token rule 846 * accept states if the rule was invoked by somebody. 847 */ 848 public DFAState reach(DFAState d, Label label) { 849 //System.out.println("reach "+label.toString(dfa.nfa.grammar)+" from "+d.stateNumber); 850 DFAState labelDFATarget = dfa.newState(); 851 852 // for each NFA state in d with a labeled edge, 853 // add in target states for label 854 //System.out.println("size(d.state="+d.stateNumber+")="+d.nfaConfigurations.size()); 855 //System.out.println("size(labeled edge states)="+d.configurationsWithLabeledEdges.size()); 856 List<NFAConfiguration> configs = d.configurationsWithLabeledEdges; 857 int numConfigs = configs.size(); 858 for (int i = 0; i < numConfigs; i++) { 859 NFAConfiguration c = configs.get(i); 860 if ( c.resolved || c.resolveWithPredicate ) { 861 continue; // the conflict resolver indicates we must leave alone 862 } 863 NFAState p = dfa.nfa.getState(c.state); 864 // by design of the grammar->NFA conversion, only transition 0 865 // may have a non-epsilon edge. 866 Transition edge = p.transition[0]; 867 if ( edge==null || !c.singleAtomTransitionEmanating ) { 868 continue; 869 } 870 Label edgeLabel = edge.label; 871 872 // SPECIAL CASE 873 // if it's an EOT transition on end of lexer rule, but context 874 // stack is not empty, then don't see the EOT; the closure 875 // will have added in the proper states following the reference 876 // to this rule in the invoking rule. In other words, if 877 // somebody called this rule, don't see the EOT emanating from 878 // this accept state. 879 if ( c.context.parent!=null && edgeLabel.label==Label.EOT ) { 880 continue; 881 } 882 883 // Labels not unique at this point (not until addReachableLabels) 884 // so try simple int label match before general set intersection 885 //System.out.println("comparing "+edgeLabel+" with "+label); 886 if ( Label.intersect(label, edgeLabel) ) { 887 // found a transition with label; 888 // add NFA target to (potentially) new DFA state 889 NFAConfiguration newC = labelDFATarget.addNFAConfiguration( 890 (NFAState)edge.target, 891 c.alt, 892 c.context, 893 c.semanticContext); 894 } 895 } 896 if ( labelDFATarget.nfaConfigurations.size()==0 ) { 897 // kill; it's empty 898 dfa.setState(labelDFATarget.stateNumber, null); 899 labelDFATarget = null; 900 } 901 return labelDFATarget; 902 } 903 904 /** Walk the configurations of this DFA state d looking for the 905 * configuration, c, that has a transition on EOT. State d should 906 * be converted to an accept state predicting the c.alt. Blast 907 * d's current configuration set and make it just have config c. 908 * 909 * TODO: can there be more than one config with EOT transition? 910 * That would mean that two NFA configurations could reach the 911 * end of the token with possibly different predicted alts. 912 * Seems like that would be rare or impossible. Perhaps convert 913 * this routine to find all such configs and give error if >1. 914 */ 915 protected void convertToEOTAcceptState(DFAState d) { 916 Label eot = new Label(Label.EOT); 917 int numConfigs = d.nfaConfigurations.size(); 918 for (int i = 0; i < numConfigs; i++) { 919 NFAConfiguration c = d.nfaConfigurations.get(i); 920 if ( c.resolved || c.resolveWithPredicate ) { 921 continue; // the conflict resolver indicates we must leave alone 922 } 923 NFAState p = dfa.nfa.getState(c.state); 924 Transition edge = p.transition[0]; 925 Label edgeLabel = edge.label; 926 if ( edgeLabel.equals(eot) ) { 927 //System.out.println("config with EOT: "+c); 928 d.setAcceptState(true); 929 //System.out.println("d goes from "+d); 930 d.nfaConfigurations.clear(); 931 d.addNFAConfiguration(p,c.alt,c.context,c.semanticContext); 932 //System.out.println("to "+d); 933 return; // assume only one EOT transition 934 } 935 } 936 } 937 938 /** Add a new DFA state to the DFA if not already present. 939 * If the DFA state uniquely predicts a single alternative, it 940 * becomes a stop state; don't add to work list. Further, if 941 * there exists an NFA state predicted by > 1 different alternatives 942 * and with the same syn and sem context, the DFA is nondeterministic for 943 * at least one input sequence reaching that NFA state. 944 */ 945 protected DFAState addDFAStateToWorkList(DFAState d) { 946 DFAState existingState = dfa.addState(d); 947 if ( d != existingState ) { 948 // already there...use/return the existing DFA state. 949 // But also set the states[d.stateNumber] to the existing 950 // DFA state because the closureIsBusy must report 951 // infinite recursion on a state before it knows 952 // whether or not the state will already be 953 // found after closure on it finishes. It could be 954 // referring to a state that will ultimately not make it 955 // into the reachable state space and the error 956 // reporting must be able to compute the path from 957 // start to the error state with infinite recursion 958 dfa.setState(d.stateNumber, existingState); 959 return existingState; 960 } 961 962 // if not there, then examine new state. 963 964 // resolve syntactic conflicts by choosing a single alt or 965 // by using semantic predicates if present. 966 resolveNonDeterminisms(d); 967 968 // If deterministic, don't add this state; it's an accept state 969 // Just return as a valid DFA state 970 int alt = d.getUniquelyPredictedAlt(); 971 if ( alt!=NFA.INVALID_ALT_NUMBER ) { // uniquely predicts an alt? 972 d = convertToAcceptState(d, alt); 973 /* 974 System.out.println("convert to accept; DFA "+d.dfa.decisionNumber+" state "+d.stateNumber+" uniquely predicts alt "+ 975 d.getUniquelyPredictedAlt()); 976 */ 977 } 978 else { 979 // unresolved, add to work list to continue NFA conversion 980 work.add(d); 981 } 982 return d; 983 } 984 985 protected DFAState convertToAcceptState(DFAState d, int alt) { 986 // only merge stop states if they are deterministic and no 987 // recursion problems and only if they have the same gated pred 988 // context! 989 // Later, the error reporting may want to trace the path from 990 // the start state to the nondet state 991 if ( DFAOptimizer.MERGE_STOP_STATES && 992 d.getNonDeterministicAlts()==null && 993 !d.abortedDueToRecursionOverflow && 994 !d.abortedDueToMultipleRecursiveAlts ) 995 { 996 // check to see if we already have an accept state for this alt 997 // [must do this after we resolve nondeterminisms in general] 998 DFAState acceptStateForAlt = dfa.getAcceptState(alt); 999 if ( acceptStateForAlt!=null ) { 1000 // we already have an accept state for alt; 1001 // Are their gate sem pred contexts the same? 1002 // For now we assume a braindead version: both must not 1003 // have gated preds or share exactly same single gated pred. 1004 // The equals() method is only defined on Predicate contexts not 1005 // OR etc... 1006 SemanticContext gatedPreds = d.getGatedPredicatesInNFAConfigurations(); 1007 SemanticContext existingStateGatedPreds = 1008 acceptStateForAlt.getGatedPredicatesInNFAConfigurations(); 1009 if ( (gatedPreds==null && existingStateGatedPreds==null) || 1010 ((gatedPreds!=null && existingStateGatedPreds!=null) && 1011 gatedPreds.equals(existingStateGatedPreds)) ) 1012 { 1013 // make this d.statenumber point at old DFA state 1014 dfa.setState(d.stateNumber, acceptStateForAlt); 1015 dfa.removeState(d); // remove this state from unique DFA state set 1016 d = acceptStateForAlt; // use old accept state; throw this one out 1017 return d; 1018 } 1019 // else consider it a new accept state; fall through. 1020 } 1021 } 1022 d.setAcceptState(true); // new accept state for alt 1023 dfa.setAcceptState(alt, d); 1024 return d; 1025 } 1026 1027 /** If > 1 NFA configurations within this DFA state have identical 1028 * NFA state and context, but differ in their predicted 1029 * TODO update for new context suffix stuff 3-9-2005 1030 * alternative then a single input sequence predicts multiple alts. 1031 * The NFA decision is therefore syntactically indistinguishable 1032 * from the left edge upon at least one input sequence. We may 1033 * terminate the NFA to DFA conversion for these paths since no 1034 * paths emanating from those NFA states can possibly separate 1035 * these conjoined twins once interwined to make things 1036 * deterministic (unless there are semantic predicates; see below). 1037 * 1038 * Upon a nondeterministic set of NFA configurations, we should 1039 * report a problem to the grammar designer and resolve the issue 1040 * by aribitrarily picking the first alternative (this usually 1041 * ends up producing the most natural behavior). Pick the lowest 1042 * alt number and just turn off all NFA configurations 1043 * associated with the other alts. Rather than remove conflicting 1044 * NFA configurations, I set the "resolved" bit so that future 1045 * computations will ignore them. In this way, we maintain the 1046 * complete DFA state with all its configurations, but prevent 1047 * future DFA conversion operations from pursuing undesirable 1048 * paths. Remember that we want to terminate DFA conversion as 1049 * soon as we know the decision is deterministic *or* 1050 * nondeterministic. 1051 * 1052 * [BTW, I have convinced myself that there can be at most one 1053 * set of nondeterministic configurations in a DFA state. Only NFA 1054 * configurations arising from the same input sequence can appear 1055 * in a DFA state. There is no way to have another complete set 1056 * of nondeterministic NFA configurations without another input 1057 * sequence, which would reach a different DFA state. Therefore, 1058 * the two nondeterministic NFA configuration sets cannot collide 1059 * in the same DFA state.] 1060 * 1061 * Consider DFA state {(s|1),(s|2),(s|3),(t|3),(v|4)} where (s|a) 1062 * is state 's' and alternative 'a'. Here, configuration set 1063 * {(s|1),(s|2),(s|3)} predicts 3 different alts. Configurations 1064 * (s|2) and (s|3) are "resolved", leaving {(s|1),(t|3),(v|4)} as 1065 * items that must still be considered by the DFA conversion 1066 * algorithm in DFA.findNewDFAStatesAndAddDFATransitions(). 1067 * 1068 * Consider the following grammar where alts 1 and 2 are no 1069 * problem because of the 2nd lookahead symbol. Alts 3 and 4 are 1070 * identical and will therefore reach the rule end NFA state but 1071 * predicting 2 different alts (no amount of future lookahead 1072 * will render them deterministic/separable): 1073 * 1074 * a : A B 1075 * | A C 1076 * | A 1077 * | A 1078 * ; 1079 * 1080 * Here is a (slightly reduced) NFA of this grammar: 1081 * 1082 * (1)-A->(2)-B->(end)-EOF->(8) 1083 * | ^ 1084 * (2)-A->(3)-C----| 1085 * | ^ 1086 * (4)-A->(5)------| 1087 * | ^ 1088 * (6)-A->(7)------| 1089 * 1090 * where (n) is NFA state n. To begin DFA conversion, the start 1091 * state is created: 1092 * 1093 * {(1|1),(2|2),(4|3),(6|4)} 1094 * 1095 * Upon A, all NFA configurations lead to new NFA states yielding 1096 * new DFA state: 1097 * 1098 * {(2|1),(3|2),(5|3),(7|4),(end|3),(end|4)} 1099 * 1100 * where the configurations with state end in them are added 1101 * during the epsilon closure operation. State end predicts both 1102 * alts 3 and 4. An error is reported, the latter configuration is 1103 * flagged as resolved leaving the DFA state as: 1104 * 1105 * {(2|1),(3|2),(5|3),(7|4|resolved),(end|3),(end|4|resolved)} 1106 * 1107 * As NFA configurations are added to a DFA state during its 1108 * construction, the reachable set of labels is computed. Here 1109 * reachable is {B,C,EOF} because there is at least one NFA state 1110 * in the DFA state that can transition upon those symbols. 1111 * 1112 * The final DFA looks like: 1113 * 1114 * {(1|1),(2|2),(4|3),(6|4)} 1115 * | 1116 * v 1117 * {(2|1),(3|2),(5|3),(7|4),(end|3),(end|4)} -B-> (end|1) 1118 * | | 1119 * C ----EOF-> (8,3) 1120 * | 1121 * v 1122 * (end|2) 1123 * 1124 * Upon AB, alt 1 is predicted. Upon AC, alt 2 is predicted. 1125 * Upon A EOF, alt 3 is predicted. Alt 4 is not a viable 1126 * alternative. 1127 * 1128 * The algorithm is essentially to walk all the configurations 1129 * looking for a conflict of the form (s|i) and (s|j) for i!=j. 1130 * Use a hash table to track state+context pairs for collisions 1131 * so that we have O(n) to walk the n configurations looking for 1132 * a conflict. Upon every conflict, track the alt number so 1133 * we have a list of all nondeterministically predicted alts. Also 1134 * track the minimum alt. Next go back over the configurations, setting 1135 * the "resolved" bit for any that have an alt that is a member of 1136 * the nondeterministic set. This will effectively remove any alts 1137 * but the one we want from future consideration. 1138 * 1139 * See resolveWithSemanticPredicates() 1140 * 1141 * AMBIGUOUS TOKENS 1142 * 1143 * With keywords and ID tokens, there is an inherit ambiguity in that 1144 * "int" can be matched by ID also. Each lexer rule has an EOT 1145 * transition emanating from it which is used whenever the end of 1146 * a rule is reached and another token rule did not invoke it. EOT 1147 * is the only thing that can be seen next. If two rules are identical 1148 * like "int" and "int" then the 2nd def is unreachable and you'll get 1149 * a warning. We prevent a warning though for the keyword/ID issue as 1150 * ID is still reachable. This can be a bit weird. '+' rule then a 1151 * '+'|'+=' rule will fail to match '+' for the 2nd rule. 1152 * 1153 * If all NFA states in this DFA state are targets of EOT transitions, 1154 * (and there is more than one state plus no unique alt is predicted) 1155 * then DFA conversion will leave this state as a dead state as nothing 1156 * can be reached from this state. To resolve the ambiguity, just do 1157 * what flex and friends do: pick the first rule (alt in this case) to 1158 * win. This means you should put keywords before the ID rule. 1159 * If the DFA state has only one NFA state then there is no issue: 1160 * it uniquely predicts one alt. :) Problem 1161 * states will look like this during conversion: 1162 * 1163 * DFA 1:{9|1, 19|2, 14|3, 20|2, 23|2, 24|2, ...}-<EOT>->5:{41|3, 42|2} 1164 * 1165 * Worse, when you have two identical literal rules, you will see 3 alts 1166 * in the EOT state (one for ID and one each for the identical rules). 1167 */ 1168 public void resolveNonDeterminisms(DFAState d) { 1169 if ( debug ) { 1170 System.out.println("resolveNonDeterminisms "+d.toString()); 1171 } 1172 boolean conflictingLexerRules = false; 1173 Set<Integer> nondeterministicAlts = d.getNonDeterministicAlts(); 1174 if ( debug && nondeterministicAlts!=null ) { 1175 System.out.println("nondet alts="+nondeterministicAlts); 1176 } 1177 1178 // CHECK FOR AMBIGUOUS EOT (if |allAlts|>1 and EOT state, resolve) 1179 // grab any config to see if EOT state; any other configs must 1180 // transition on EOT to get to this DFA state as well so all 1181 // states in d must be targets of EOT. These are the end states 1182 // created in NFAFactory.build_EOFState 1183 NFAConfiguration anyConfig = d.nfaConfigurations.get(0); 1184 NFAState anyState = dfa.nfa.getState(anyConfig.state); 1185 1186 // if d is target of EOT and more than one predicted alt 1187 // indicate that d is nondeterministic on all alts otherwise 1188 // it looks like state has no problem 1189 if ( anyState.isEOTTargetState() ) { 1190 Set<Integer> allAlts = d.getAltSet(); 1191 // is more than 1 alt predicted? 1192 if ( allAlts!=null && allAlts.size()>1 ) { 1193 nondeterministicAlts = allAlts; 1194 // track Tokens rule issues differently than other decisions 1195 if ( d.dfa.isTokensRuleDecision() ) { 1196 dfa.probe.reportLexerRuleNondeterminism(d,allAlts); 1197 //System.out.println("Tokens rule DFA state "+d+" nondeterministic"); 1198 conflictingLexerRules = true; 1199 } 1200 } 1201 } 1202 1203 // if no problems return unless we aborted work on d to avoid inf recursion 1204 if ( !d.abortedDueToRecursionOverflow && nondeterministicAlts==null ) { 1205 return; // no problems, return 1206 } 1207 1208 // if we're not a conflicting lexer rule and we didn't abort, report ambig 1209 // We should get a report for abort so don't give another 1210 if ( !d.abortedDueToRecursionOverflow && !conflictingLexerRules ) { 1211 // TODO: with k=x option set, this is called twice for same state 1212 dfa.probe.reportNondeterminism(d, nondeterministicAlts); 1213 // TODO: how to turn off when it's only the FOLLOW that is 1214 // conflicting. This used to shut off even alts i,j < n 1215 // conflict warnings. :( 1216 } 1217 1218 // ATTEMPT TO RESOLVE WITH SEMANTIC PREDICATES 1219 boolean resolved = 1220 tryToResolveWithSemanticPredicates(d, nondeterministicAlts); 1221 if ( resolved ) { 1222 if ( debug ) { 1223 System.out.println("resolved DFA state "+d.stateNumber+" with pred"); 1224 } 1225 d.resolvedWithPredicates = true; 1226 dfa.probe.reportNondeterminismResolvedWithSemanticPredicate(d); 1227 return; 1228 } 1229 1230 // RESOLVE SYNTACTIC CONFLICT BY REMOVING ALL BUT ONE ALT 1231 resolveByChoosingFirstAlt(d, nondeterministicAlts); 1232 1233 //System.out.println("state "+d.stateNumber+" resolved to alt "+winningAlt); 1234 } 1235 1236 protected int resolveByChoosingFirstAlt(DFAState d, Set<Integer> nondeterministicAlts) { 1237 int winningAlt; 1238 if ( dfa.isGreedy() ) { 1239 winningAlt = resolveByPickingMinAlt(d,nondeterministicAlts); 1240 } 1241 else { 1242 // If nongreedy, the exit alt shout win, but only if it's 1243 // involved in the nondeterminism! 1244 /* 1245 System.out.println("resolving exit alt for decision="+ 1246 dfa.decisionNumber+" state="+d); 1247 System.out.println("nondet="+nondeterministicAlts); 1248 System.out.println("exit alt "+exitAlt); 1249 */ 1250 int exitAlt = dfa.getNumberOfAlts(); 1251 if ( nondeterministicAlts.contains(Utils.integer(exitAlt)) ) { 1252 // if nongreedy and exit alt is one of those nondeterministic alts 1253 // predicted, resolve in favor of what follows block 1254 winningAlt = resolveByPickingExitAlt(d,nondeterministicAlts); 1255 } 1256 else { 1257 winningAlt = resolveByPickingMinAlt(d,nondeterministicAlts); 1258 } 1259 } 1260 return winningAlt; 1261 } 1262 1263 /** Turn off all configurations associated with the 1264 * set of incoming nondeterministic alts except the min alt number. 1265 * There may be many alts among the configurations but only turn off 1266 * the ones with problems (other than the min alt of course). 1267 * 1268 * If nondeterministicAlts is null then turn off all configs 'cept those 1269 * associated with the minimum alt. 1270 * 1271 * Return the min alt found. 1272 */ 1273 protected int resolveByPickingMinAlt(DFAState d, Set<Integer> nondeterministicAlts) { 1274 int min; 1275 if ( nondeterministicAlts!=null ) { 1276 min = getMinAlt(nondeterministicAlts); 1277 } 1278 else { 1279 min = d.minAltInConfigurations; 1280 } 1281 1282 turnOffOtherAlts(d, min, nondeterministicAlts); 1283 1284 return min; 1285 } 1286 1287 /** Resolve state d by choosing exit alt, which is same value as the 1288 * number of alternatives. Return that exit alt. 1289 */ 1290 protected int resolveByPickingExitAlt(DFAState d, Set<Integer> nondeterministicAlts) { 1291 int exitAlt = dfa.getNumberOfAlts(); 1292 turnOffOtherAlts(d, exitAlt, nondeterministicAlts); 1293 return exitAlt; 1294 } 1295 1296 /** turn off all states associated with alts other than the good one 1297 * (as long as they are one of the nondeterministic ones) 1298 */ 1299 protected static void turnOffOtherAlts(DFAState d, int min, Set<Integer> nondeterministicAlts) { 1300 int numConfigs = d.nfaConfigurations.size(); 1301 for (int i = 0; i < numConfigs; i++) { 1302 NFAConfiguration configuration = d.nfaConfigurations.get(i); 1303 if ( configuration.alt!=min ) { 1304 if ( nondeterministicAlts==null || 1305 nondeterministicAlts.contains(Utils.integer(configuration.alt)) ) 1306 { 1307 configuration.resolved = true; 1308 } 1309 } 1310 } 1311 } 1312 1313 protected static int getMinAlt(Set<Integer> nondeterministicAlts) { 1314 int min = Integer.MAX_VALUE; 1315 for (Integer altI : nondeterministicAlts) { 1316 int alt = altI; 1317 if ( alt < min ) { 1318 min = alt; 1319 } 1320 } 1321 return min; 1322 } 1323 1324 /** See if a set of nondeterministic alternatives can be disambiguated 1325 * with the semantic predicate contexts of the alternatives. 1326 * 1327 * Without semantic predicates, syntactic conflicts are resolved 1328 * by simply choosing the first viable alternative. In the 1329 * presence of semantic predicates, you can resolve the issue by 1330 * evaluating boolean expressions at run time. During analysis, 1331 * this amounts to suppressing grammar error messages to the 1332 * developer. NFA configurations are always marked as "to be 1333 * resolved with predicates" so that 1334 * DFA.findNewDFAStatesAndAddDFATransitions() will know to ignore 1335 * these configurations and add predicate transitions to the DFA 1336 * after adding token/char labels. 1337 * 1338 * During analysis, we can simply make sure that for n 1339 * ambiguously predicted alternatives there are at least n-1 1340 * unique predicate sets. The nth alternative can be predicted 1341 * with "not" the "or" of all other predicates. NFA configurations without 1342 * predicates are assumed to have the default predicate of 1343 * "true" from a user point of view. When true is combined via || with 1344 * another predicate, the predicate is a tautology and must be removed 1345 * from consideration for disambiguation: 1346 * 1347 * a : b | B ; // hoisting p1||true out of rule b, yields no predicate 1348 * b : {p1}? B | B ; 1349 * 1350 * This is done down in getPredicatesPerNonDeterministicAlt(). 1351 */ 1352 protected boolean tryToResolveWithSemanticPredicates(DFAState d, 1353 Set<Integer> nondeterministicAlts) 1354 { 1355 Map<Integer, SemanticContext> altToPredMap = 1356 getPredicatesPerNonDeterministicAlt(d, nondeterministicAlts); 1357 1358 if ( altToPredMap.isEmpty() ) { 1359 return false; 1360 } 1361 1362 //System.out.println("nondeterministic alts with predicates: "+altToPredMap); 1363 dfa.probe.reportAltPredicateContext(d, altToPredMap); 1364 1365 if ( nondeterministicAlts.size()-altToPredMap.size()>1 ) { 1366 // too few predicates to resolve; just return 1367 return false; 1368 } 1369 1370 // Handle case where 1 predicate is missing 1371 // Case 1. Semantic predicates 1372 // If the missing pred is on nth alt, !(union of other preds)==true 1373 // so we can avoid that computation. If naked alt is ith, then must 1374 // test it with !(union) since semantic predicated alts are order 1375 // independent 1376 // Case 2: Syntactic predicates 1377 // The naked alt is always assumed to be true as the order of 1378 // alts is the order of precedence. The naked alt will be a tautology 1379 // anyway as it's !(union of other preds). This implies 1380 // that there is no such thing as noviable alt for synpred edges 1381 // emanating from a DFA state. 1382 if ( altToPredMap.size()==nondeterministicAlts.size()-1 ) { 1383 // if there are n-1 predicates for n nondeterministic alts, can fix 1384 org.antlr.misc.BitSet ndSet = org.antlr.misc.BitSet.of(nondeterministicAlts); 1385 org.antlr.misc.BitSet predSet = org.antlr.misc.BitSet.of(altToPredMap); 1386 int nakedAlt = ndSet.subtract(predSet).getSingleElement(); 1387 SemanticContext nakedAltPred; 1388 if ( nakedAlt == max(nondeterministicAlts) ) { 1389 // the naked alt is the last nondet alt and will be the default clause 1390 nakedAltPred = new SemanticContext.TruePredicate(); 1391 } 1392 else { 1393 // pretend naked alternative is covered with !(union other preds) 1394 // unless one of preds from other alts is a manually specified synpred 1395 // since those have precedence same as alt order. Missing synpred 1396 // is true so that alt wins (or is at least attempted). 1397 // Note: can't miss any preds on alts (can't be here) if auto backtrack 1398 // since it prefixes all. 1399 // In LL(*) paper, i'll just have algorithm emit warning about uncovered 1400 // pred 1401 SemanticContext unionOfPredicatesFromAllAlts = 1402 getUnionOfPredicates(altToPredMap); 1403 //System.out.println("all predicates "+unionOfPredicatesFromAllAlts); 1404 if ( unionOfPredicatesFromAllAlts.isSyntacticPredicate() ) { 1405 nakedAltPred = new SemanticContext.TruePredicate(); 1406 } 1407 else { 1408 nakedAltPred = 1409 SemanticContext.not(unionOfPredicatesFromAllAlts); 1410 } 1411 } 1412 1413 //System.out.println("covering naked alt="+nakedAlt+" with "+nakedAltPred); 1414 1415 altToPredMap.put(Utils.integer(nakedAlt), nakedAltPred); 1416 // set all config with alt=nakedAlt to have the computed predicate 1417 int numConfigs = d.nfaConfigurations.size(); 1418 for (int i = 0; i < numConfigs; i++) { // TODO: I don't think we need to do this; altToPredMap has it 1419 //7/27/10 theok, I removed it and it still seems to work with everything; leave in anyway just in case 1420 NFAConfiguration configuration = d.nfaConfigurations.get(i); 1421 if ( configuration.alt == nakedAlt ) { 1422 configuration.semanticContext = nakedAltPred; 1423 } 1424 } 1425 } 1426 1427 if ( altToPredMap.size()==nondeterministicAlts.size() ) { 1428 // RESOLVE CONFLICT by picking one NFA configuration for each alt 1429 // and setting its resolvedWithPredicate flag 1430 // First, prevent a recursion warning on this state due to 1431 // pred resolution 1432 if ( d.abortedDueToRecursionOverflow ) { 1433 d.dfa.probe.removeRecursiveOverflowState(d); 1434 } 1435 int numConfigs = d.nfaConfigurations.size(); 1436 //System.out.println("pred map="+altToPredMap); 1437 for (int i = 0; i < numConfigs; i++) { 1438 NFAConfiguration configuration = d.nfaConfigurations.get(i); 1439 SemanticContext semCtx = altToPredMap.get(Utils.integer(configuration.alt)); 1440 if ( semCtx!=null ) { 1441 // resolve (first found) with pred 1442 // and remove alt from problem list 1443 //System.out.println("c="+configuration); 1444 configuration.resolveWithPredicate = true; 1445 // altToPredMap has preds from all alts; store into "annointed" config 1446 configuration.semanticContext = semCtx; // reset to combined 1447 altToPredMap.remove(Utils.integer(configuration.alt)); 1448 1449 // notify grammar that we've used the preds contained in semCtx 1450 if ( semCtx.isSyntacticPredicate() ) { 1451 dfa.nfa.grammar.synPredUsedInDFA(dfa, semCtx); 1452 } 1453 } 1454 else if ( nondeterministicAlts.contains(Utils.integer(configuration.alt)) ) { 1455 // resolve all configurations for nondeterministic alts 1456 // for which there is no predicate context by turning it off 1457 configuration.resolved = true; 1458 } 1459 } 1460 return true; 1461 } 1462 1463 return false; // couldn't fix the problem with predicates 1464 } 1465 1466 /** Return a mapping from nondeterministc alt to combined list of predicates. 1467 * If both (s|i|semCtx1) and (t|i|semCtx2) exist, then the proper predicate 1468 * for alt i is semCtx1||semCtx2 because you have arrived at this single 1469 * DFA state via two NFA paths, both of which have semantic predicates. 1470 * We ignore deterministic alts because syntax alone is sufficient 1471 * to predict those. Do not include their predicates. 1472 * 1473 * Alts with no predicate are assumed to have {true}? pred. 1474 * 1475 * When combining via || with "true", all predicates are removed from 1476 * consideration since the expression will always be true and hence 1477 * not tell us how to resolve anything. So, if any NFA configuration 1478 * in this DFA state does not have a semantic context, the alt cannot 1479 * be resolved with a predicate. 1480 * 1481 * If nonnull, incidentEdgeLabel tells us what NFA transition label 1482 * we did a reach on to compute state d. d may have insufficient 1483 * preds, so we really want this for the error message. 1484 */ 1485 protected Map<Integer, SemanticContext> getPredicatesPerNonDeterministicAlt(DFAState d, 1486 Set<Integer> nondeterministicAlts) 1487 { 1488 // map alt to combined SemanticContext 1489 Map<Integer, SemanticContext> altToPredicateContextMap = 1490 new HashMap<Integer, SemanticContext>(); 1491 // init the alt to predicate set map 1492 Map<Integer, OrderedHashSet<SemanticContext>> altToSetOfContextsMap = 1493 new HashMap<Integer, OrderedHashSet<SemanticContext>>(); 1494 for (Integer altI : nondeterministicAlts) { 1495 altToSetOfContextsMap.put(altI, new OrderedHashSet<SemanticContext>()); 1496 } 1497 1498 /* 1499 List<Label> sampleInputLabels = d.dfa.probe.getSampleNonDeterministicInputSequence(d); 1500 String input = d.dfa.probe.getInputSequenceDisplay(sampleInputLabels); 1501 System.out.println("sample input: "+input); 1502 */ 1503 1504 // for each configuration, create a unique set of predicates 1505 // Also, track the alts with at least one uncovered configuration 1506 // (one w/o a predicate); tracks tautologies like p1||true 1507 Map<Integer, Set<Token>> altToLocationsReachableWithoutPredicate = new HashMap<Integer, Set<Token>>(); 1508 Set<Integer> nondetAltsWithUncoveredConfiguration = new HashSet<Integer>(); 1509 //System.out.println("configs="+d.nfaConfigurations); 1510 //System.out.println("configs with preds?"+d.atLeastOneConfigurationHasAPredicate); 1511 //System.out.println("configs with preds="+d.configurationsWithPredicateEdges); 1512 int numConfigs = d.nfaConfigurations.size(); 1513 for (int i = 0; i < numConfigs; i++) { 1514 NFAConfiguration configuration = d.nfaConfigurations.get(i); 1515 Integer altI = Utils.integer(configuration.alt); 1516 // if alt is nondeterministic, combine its predicates 1517 if ( nondeterministicAlts.contains(altI) ) { 1518 // if there is a predicate for this NFA configuration, OR in 1519 if ( configuration.semanticContext != 1520 SemanticContext.EMPTY_SEMANTIC_CONTEXT ) 1521 { 1522 Set<SemanticContext> predSet = altToSetOfContextsMap.get(altI); 1523 predSet.add(configuration.semanticContext); 1524 } 1525 else { 1526 // if no predicate, but it's part of nondeterministic alt 1527 // then at least one path exists not covered by a predicate. 1528 // must remove predicate for this alt; track incomplete alts 1529 nondetAltsWithUncoveredConfiguration.add(altI); 1530 /* 1531 NFAState s = dfa.nfa.getState(configuration.state); 1532 System.out.println("###\ndec "+dfa.decisionNumber+" alt "+configuration.alt+ 1533 " enclosing rule for nfa state not covered "+ 1534 s.enclosingRule); 1535 if ( s.associatedASTNode!=null ) { 1536 System.out.println("token="+s.associatedASTNode.token); 1537 } 1538 System.out.println("nfa state="+s); 1539 1540 if ( s.incidentEdgeLabel!=null && Label.intersect(incidentEdgeLabel, s.incidentEdgeLabel) ) { 1541 Set<Token> locations = altToLocationsReachableWithoutPredicate.get(altI); 1542 if ( locations==null ) { 1543 locations = new HashSet<Token>(); 1544 altToLocationsReachableWithoutPredicate.put(altI, locations); 1545 } 1546 locations.add(s.associatedASTNode.token); 1547 } 1548 */ 1549 } 1550 } 1551 } 1552 1553 // For each alt, OR together all unique predicates associated with 1554 // all configurations 1555 // Also, track the list of incompletely covered alts: those alts 1556 // with at least 1 predicate and at least one configuration w/o a 1557 // predicate. We want this in order to report to the decision probe. 1558 List<Integer> incompletelyCoveredAlts = new ArrayList<Integer>(); 1559 for (Integer altI : nondeterministicAlts) { 1560 Set<SemanticContext> contextsForThisAlt = altToSetOfContextsMap.get(altI); 1561 if ( nondetAltsWithUncoveredConfiguration.contains(altI) ) { // >= 1 config has no ctx 1562 if ( contextsForThisAlt.size()>0 ) { // && at least one pred 1563 incompletelyCoveredAlts.add(altI); // this alt incompleted covered 1564 } 1565 continue; // don't include at least 1 config has no ctx 1566 } 1567 SemanticContext combinedContext = null; 1568 for (SemanticContext ctx : contextsForThisAlt) { 1569 combinedContext = 1570 SemanticContext.or(combinedContext,ctx); 1571 } 1572 altToPredicateContextMap.put(altI, combinedContext); 1573 } 1574 1575 if ( incompletelyCoveredAlts.size()>0 ) { 1576 /* 1577 System.out.println("prob in dec "+dfa.decisionNumber+" state="+d); 1578 FASerializer serializer = new FASerializer(dfa.nfa.grammar); 1579 String result = serializer.serialize(dfa.startState); 1580 System.out.println("dfa: "+result); 1581 System.out.println("incomplete alts: "+incompletelyCoveredAlts); 1582 System.out.println("nondet="+nondeterministicAlts); 1583 System.out.println("nondetAltsWithUncoveredConfiguration="+ nondetAltsWithUncoveredConfiguration); 1584 System.out.println("altToCtxMap="+altToSetOfContextsMap); 1585 System.out.println("altToPredicateContextMap="+altToPredicateContextMap); 1586 */ 1587 for (int i = 0; i < numConfigs; i++) { 1588 NFAConfiguration configuration = d.nfaConfigurations.get(i); 1589 Integer altI = Utils.integer(configuration.alt); 1590 if ( incompletelyCoveredAlts.contains(altI) && 1591 configuration.semanticContext == SemanticContext.EMPTY_SEMANTIC_CONTEXT ) 1592 { 1593 NFAState s = dfa.nfa.getState(configuration.state); 1594 /* 1595 System.out.print("nondet config w/o context "+configuration+ 1596 " incident "+(s.incidentEdgeLabel!=null?s.incidentEdgeLabel.toString(dfa.nfa.grammar):null)); 1597 if ( s.associatedASTNode!=null ) { 1598 System.out.print(" token="+s.associatedASTNode.token); 1599 } 1600 else System.out.println(); 1601 */ 1602 // We want to report getting to an NFA state with an 1603 // incoming label, unless it's EOF, w/o a predicate. 1604 if ( s.incidentEdgeLabel!=null && s.incidentEdgeLabel.label != Label.EOF ) { 1605 if ( s.associatedASTNode==null || s.associatedASTNode.token==null ) { 1606 ErrorManager.internalError("no AST/token for nonepsilon target w/o predicate"); 1607 } 1608 else { 1609 Set<Token> locations = altToLocationsReachableWithoutPredicate.get(altI); 1610 if ( locations==null ) { 1611 locations = new HashSet<Token>(); 1612 altToLocationsReachableWithoutPredicate.put(altI, locations); 1613 } 1614 locations.add(s.associatedASTNode.token); 1615 } 1616 } 1617 } 1618 } 1619 dfa.probe.reportIncompletelyCoveredAlts(d, 1620 altToLocationsReachableWithoutPredicate); 1621 } 1622 1623 return altToPredicateContextMap; 1624 } 1625 1626 /** OR together all predicates from the alts. Note that the predicate 1627 * for an alt could itself be a combination of predicates. 1628 */ 1629 protected static SemanticContext getUnionOfPredicates(Map<?, SemanticContext> altToPredMap) { 1630 Iterator<SemanticContext> iter; 1631 SemanticContext unionOfPredicatesFromAllAlts = null; 1632 iter = altToPredMap.values().iterator(); 1633 while ( iter.hasNext() ) { 1634 SemanticContext semCtx = iter.next(); 1635 if ( unionOfPredicatesFromAllAlts==null ) { 1636 unionOfPredicatesFromAllAlts = semCtx; 1637 } 1638 else { 1639 unionOfPredicatesFromAllAlts = 1640 SemanticContext.or(unionOfPredicatesFromAllAlts,semCtx); 1641 } 1642 } 1643 return unionOfPredicatesFromAllAlts; 1644 } 1645 1646 /** for each NFA config in d, look for "predicate required" sign set 1647 * during nondeterminism resolution. 1648 * 1649 * Add the predicate edges sorted by the alternative number; I'm fairly 1650 * sure that I could walk the configs backwards so they are added to 1651 * the predDFATarget in the right order, but it's best to make sure. 1652 * Predicates succeed in the order they are specifed. Alt i wins 1653 * over alt i+1 if both predicates are true. 1654 */ 1655 protected void addPredicateTransitions(DFAState d) { 1656 List<NFAConfiguration> configsWithPreds = new ArrayList<NFAConfiguration>(); 1657 // get a list of all configs with predicates 1658 int numConfigs = d.nfaConfigurations.size(); 1659 for (int i = 0; i < numConfigs; i++) { 1660 NFAConfiguration c = d.nfaConfigurations.get(i); 1661 if ( c.resolveWithPredicate ) { 1662 configsWithPreds.add(c); 1663 } 1664 } 1665 // Sort ascending according to alt; alt i has higher precedence than i+1 1666 Collections.sort(configsWithPreds, 1667 new Comparator<NFAConfiguration>() { 1668 @Override 1669 public int compare(NFAConfiguration a, NFAConfiguration b) { 1670 if ( a.alt < b.alt ) return -1; 1671 else if ( a.alt > b.alt ) return 1; 1672 return 0; 1673 } 1674 }); 1675 List<NFAConfiguration> predConfigsSortedByAlt = configsWithPreds; 1676 // Now, we can add edges emanating from d for these preds in right order 1677 for (int i = 0; i < predConfigsSortedByAlt.size(); i++) { 1678 NFAConfiguration c = predConfigsSortedByAlt.get(i); 1679 DFAState predDFATarget = d.dfa.getAcceptState(c.alt); 1680 if ( predDFATarget==null ) { 1681 predDFATarget = dfa.newState(); // create if not there. 1682 // create a new DFA state that is a target of the predicate from d 1683 predDFATarget.addNFAConfiguration(dfa.nfa.getState(c.state), 1684 c.alt, 1685 c.context, 1686 c.semanticContext); 1687 predDFATarget.setAcceptState(true); 1688 dfa.setAcceptState(c.alt, predDFATarget); 1689 DFAState existingState = dfa.addState(predDFATarget); 1690 if ( predDFATarget != existingState ) { 1691 // already there...use/return the existing DFA state that 1692 // is a target of this predicate. Make this state number 1693 // point at the existing state 1694 dfa.setState(predDFATarget.stateNumber, existingState); 1695 predDFATarget = existingState; 1696 } 1697 } 1698 // add a transition to pred target from d 1699 d.addTransition(predDFATarget, new PredicateLabel(c.semanticContext)); 1700 } 1701 } 1702 1703 protected void initContextTrees(int numberOfAlts) { 1704 contextTrees = new NFAContext[numberOfAlts]; 1705 for (int i = 0; i < contextTrees.length; i++) { 1706 int alt = i+1; 1707 // add a dummy root node so that an NFA configuration can 1708 // always point at an NFAContext. If a context refers to this 1709 // node then it implies there is no call stack for 1710 // that configuration 1711 contextTrees[i] = new NFAContext(null, null); 1712 } 1713 } 1714 1715 public static int max(Set<Integer> s) { 1716 if ( s==null ) { 1717 return Integer.MIN_VALUE; 1718 } 1719 int i = 0; 1720 int m = 0; 1721 for (Integer value : s) { 1722 i++; 1723 Integer I = value; 1724 if ( i==1 ) { // init m with first value 1725 m = I; 1726 continue; 1727 } 1728 if ( I>m ) { 1729 m = I; 1730 } 1731 } 1732 return m; 1733 } 1734 } 1735