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[git-p4: depot-paths = "//depot/code/antlr4/main/": change = 6778]
This commit is contained in:
parrt 2010-03-27 10:59:24 -08:00
parent 09974258fb
commit 63342b1b1e
5 changed files with 491 additions and 33 deletions
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16
tool/src/org/antlr/v4/analysis/AnalysisPipeline.java
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@ -37,29 +37,27 @@ public class AnalysisPipeline {
// BUILD DFA FOR EACH DECISION IN NONLEXER
for (DecisionState s : g.nfa.decisionToNFAState) {
System.out.println("\nDECISION "+s.decision);
// TRY LINEAR APPROX FIXED LOOKAHEAD FIRST
LinearApproximator lin = new LinearApproximator(g, s.decision);
DFA dfa = lin.createDFA(s);
// IF NOT LINEAR APPROX, TRY NFA TO DFA CONVERSION
if ( dfa==null ) dfa = createDFA(s);
if ( dfa==null ) {
dfa = createDFA(s);
}
g.setLookaheadDFA(s.decision, dfa);
}
}
public DFA createDFA(DecisionState s) {
// TRY STACK LIMITED LL(*) ANALYSIS
StackLimitedNFAToDFAConverter conv = new StackLimitedNFAToDFAConverter(g, s);
PredictionDFAFactory conv = new PredictionDFAFactory(g, s);
DFA dfa = conv.createDFA();
System.out.print("DFA="+dfa);
// RECURSION LIMITED LL(*) ANALYSIS IF THAT FAILS
// Only do recursion limited version if we get dangling states in stack
// limited version. Ambiguities are ok since recursion limited would
// see same thing.
if ( !dfa.valid() ) {
conv = new RecursionLimitedNFAToDFAConverter(g, s);
dfa = conv.createDFA();
System.out.print("DFA="+dfa);
System.out.print("invalid DFA");
}
conv.issueAmbiguityWarnings();

4
tool/src/org/antlr/v4/analysis/PredicateResolver.java
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@ -12,8 +12,8 @@ import java.util.*;
/** */
public class PredicateResolver {
StackLimitedNFAToDFAConverter converter;
public PredicateResolver(StackLimitedNFAToDFAConverter converter) {
PredictionDFAFactory converter;
public PredicateResolver(PredictionDFAFactory converter) {
this.converter = converter;
}

474
tool/src/org/antlr/v4/analysis/PredictionDFAFactory.java Normal file
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@ -0,0 +1,474 @@
package org.antlr.v4.analysis;
import org.antlr.v4.automata.*;
import org.antlr.v4.misc.IntervalSet;
import org.antlr.v4.misc.OrderedHashSet;
import org.antlr.v4.tool.ErrorManager;
import org.antlr.v4.tool.Grammar;
import org.antlr.v4.tool.Rule;
import java.util.*;
/** Code that embodies the NFA conversion to DFA. A new object is needed
* per DFA (also required for thread safety if multiple conversions
* launched).
*/
public class PredictionDFAFactory {
Grammar g;
DecisionState nfaStartState;
/** DFA we are creating */
DFA dfa;
/** Stack depth max; same as Bermudez's m */
int m = 1;
/** A list of DFA states we still need to process during NFA conversion */
List<DFAState> work = new LinkedList<DFAState>();
/** Each alt in an NFA derived from a grammar must have a DFA state that
* predicts it lest the parser not know what to do. Nondeterminisms can
* lead to this situation (assuming no semantic predicates can resolve
* the problem) and when for some reason, I cannot compute the lookahead
* (which might arise from an error in the algorithm or from
* left-recursion etc...).
*/
public Set<Integer> unreachableAlts;
/** Track all DFA states with ambiguous configurations.
* By reaching the same DFA state, a path through the NFA for some input
* is able to reach the same NFA state by starting at more than one
* alternative's left edge. If the context is the same or conflicts,
* then we have ambiguity. If the context is different, it's simply
* nondeterministic and we should keep looking for edges that will
* render it deterministic. If we run out of things to add to the DFA,
* we'll get a dangling state; it's non-LL(*). Later we may find that predicates
* resolve the issue, but track ambiguous states anyway.
*/
public Set<DFAState> ambiguousStates = new HashSet<DFAState>();
/** The set of states w/o emanating edges (and w/o resolving sem preds). */
public Set<DFAState> danglingStates = new HashSet<DFAState>();
/** Was a syntactic ambiguity resolved with predicates? Any DFA
* state that predicts more than one alternative, must be resolved
* with predicates or it should be reported to the user.
*/
public Set<DFAState> resolvedWithSemanticPredicates = new HashSet<DFAState>();
/** Tracks alts insufficiently covered.
* For example, p1||true gets reduced to true and so leaves
* whole alt uncovered. This maps alt num to the set of (Token)
* locations in grammar of uncovered elements.
*/
public Map<DFAState, List<Integer>> statesWithIncompletelyCoveredAlts = new HashMap<DFAState, List<Integer>>();
public boolean hasPredicateBlockedByAction = false;
/** Recursion is limited to a particular depth. Which state tripped it? */
public DFAState recursionOverflowState;
/** Which state found multiple recursive alts? */
public DFAState abortedDueToMultipleRecursiveAltsAt;
/** Are there any loops in this DFA? */
// public boolean cyclic = false;
/** Used to prevent the closure operation from looping to itself and
* hence looping forever. Sensitive to the NFA state, the alt, and
* the stack context.
*/
Set<NFAConfig> closureBusy;
Resolver resolver;
public static boolean debug = false;
public PredictionDFAFactory(Grammar g, DecisionState nfaStartState) {
this.g = g;
this.nfaStartState = nfaStartState;
dfa = new DFA(g, nfaStartState);
dfa.converter = this;
resolver = new Resolver(this);
}
public DFA createDFA() {
closureBusy = new HashSet<NFAConfig>();
computeStartState();
dfa.addState(dfa.startState); // make sure dfa knows about this state
work.add(dfa.startState);
// while more DFA states to check, process them
while ( work.size()>0 ) {
DFAState d = work.get(0);
reach(d);
resolver.resolveDeadState(d);
work.remove(0); // we're done with this DFA state
}
unreachableAlts = getUnreachableAlts();
closureBusy = null; // wack all that memory used during closure
return dfa;
}
/** From this node, add a d--a-->t transition for all
* labels 'a' where t is a DFA node created
* from the set of NFA states reachable from any NFA
* configuration in DFA state d.
*/
void reach(DFAState d) {
OrderedHashSet<IntervalSet> labels = DFA.getReachableLabels(d);
for (IntervalSet label : labels) {
DFAState t = reach(d, label);
if ( debug ) {
System.out.println("DFA state after reach -" +
label.toString(g)+"->"+t);
}
// nothing was reached by label; we must have resolved
// all NFA configs in d, when added to work, that point at label
if ( t==null ) continue;
// if ( t.getUniqueAlt()==NFA.INVALID_ALT_NUMBER ) {
// // Only compute closure if a unique alt number is not known.
// // If a unique alternative is mentioned among all NFA
// // configurations then there is no possibility of needing to look
// // beyond this state; also no possibility of a nondeterminism.
// // This optimization May 22, 2006 just dropped -Xint time
// // for analysis of Java grammar from 11.5s to 2s! Wow.
// closure(t); // add any NFA states reachable via epsilon
// }
try {
closure(t); // add any NFA states reachable via epsilon
}
catch (RecursionOverflowSignal ros) {
recursionOverflowState = d;
ErrorManager.recursionOverflow(g.fileName, d, ros.state, ros.altNum, ros.depth);
}
catch (MultipleRecursiveAltsSignal mras) {
abortedDueToMultipleRecursiveAltsAt = d;
ErrorManager.multipleRecursiveAlts(g.fileName, d, mras.recursiveAltSet);
}
catch (AnalysisTimeoutSignal at) {// TODO: nobody throws yet
ErrorManager.analysisTimeout();
}
addTransition(d, label, t); // make d-label->t transition
}
// Add semantic predicate transitions if we resolved when added to work list
if ( d.resolvedWithPredicates ) addPredicateTransitions(d);
}
/** Add t if not in DFA yet, resolving nondet's and then make d-label->t */
void addTransition(DFAState d, IntervalSet label, DFAState t) {
DFAState existing = dfa.stateSet.get(t);
if ( existing != null ) { // seen before; point at old one
d.addEdge(new Edge(existing, label));
return;
}
// resolve any syntactic conflicts by choosing a single alt or
// by using semantic predicates if present.
resolver.resolveAmbiguities(t);
// If deterministic, don't add this state; it's an accept state
// Just return as a valid DFA state
int alt = t.getUniquelyPredictedAlt();
if ( alt > 0 ) { // uniquely predicts an alt?
System.out.println(t+" predicts "+alt);
// Define new stop state
dfa.addAcceptState(alt, t);
}
else {
System.out.println("ADD "+t);
work.add(t); // unresolved, add to work list to continue NFA conversion
dfa.addState(t); // add state we've never seen before
}
d.addEdge(new Edge(t, label));
}
/** Given the set of NFA states in DFA state d, find all NFA states
* reachable traversing label arcs. By definition, there can be
* only one DFA state reachable by a single label from DFA state d so we must
* find and merge all NFA states reachable via label. Return a new
* DFAState that has all of those NFA states with their context.
*
* Because we cannot jump to another rule nor fall off the end of a rule
* via a non-epsilon transition, NFA states reachable from d have the
* same configuration as the NFA state in d. So if NFA state 7 in d's
* configurations can reach NFA state 13 then 13 will be added to the
* new DFAState (labelDFATarget) with the same configuration as state
* 7 had.
*/
public DFAState reach(DFAState d, IntervalSet label) {
//System.out.println("reach "+label.toString(g)+" from "+d.stateNumber);
DFAState labelTarget = dfa.newState();
for (NFAConfig c : d.nfaConfigs) {
int n = c.state.getNumberOfTransitions();
for (int i=0; i<n; i++) { // for each transition
Transition t = c.state.transition(i);
// when we added this state as target of some other state,
// we tried to resolve any conflicts. Ignore anything we
// were able to fix previously
if ( c.resolved || c.resolvedWithPredicate) continue;
// found a transition with label; does it collide with label?
if ( !t.isEpsilon() && !t.label().and(label).isNil() ) {
// add NFA target to (potentially) new DFA state
labelTarget.addNFAConfig(t.target, c.alt, c.context, c.semanticContext);
}
}
}
// if we couldn't find any non-resolved edges to add, return nothing
if ( labelTarget.nfaConfigs.size()==0 ) return null;
return labelTarget;
}
/** From this first NFA state of a decision, create a DFA.
* Walk each alt in decision and compute closure from the start of that
* rule, making sure that the closure does not include other alts within
* that same decision. The idea is to associate a specific alt number
* with the starting closure so we can trace the alt number for all states
* derived from this. At a stop state in the DFA, we can return this alt
* number, indicating which alt is predicted.
*/
public void computeStartState() {
DFAState d = dfa.newState();
dfa.startState = d;
// add config for each alt start, then add closure for those states
for (int altNum=1; altNum<=dfa.nAlts; altNum++) {
Transition t = nfaStartState.transition(altNum-1);
NFAState altStart = t.target;
d.addNFAConfig(altStart, altNum,
NFAContext.EMPTY,
SemanticContext.EMPTY_SEMANTIC_CONTEXT);
}
closure(d);
}
/** For all NFA states (configurations) merged in d,
* compute the epsilon closure; that is, find all NFA states reachable
* from the NFA states in d via purely epsilon transitions.
*/
public void closure(DFAState d) {
if ( debug ) {
System.out.println("closure("+d+")");
}
// Only the start state initiates pred collection; gets turned
// off maybe by actions later hence we need a parameter to carry
// it forward
boolean collectPredicates = (d == dfa.startState);
// TODO: can we avoid this separate list by directly filling d.nfaConfigs?
// OH: concurrent modification. dup initialconfigs? works for lexers, try here to save configs param
List<NFAConfig> configs = new ArrayList<NFAConfig>();
for (NFAConfig c : d.nfaConfigs) {
closure(c.state, c.alt, c.context, c.semanticContext, collectPredicates, configs);
}
d.nfaConfigs.addAll(configs); // Add new NFA configs to DFA state d
closureBusy.clear();
if ( debug ) {
System.out.println("after closure("+d+")");
}
//System.out.println("after closure d="+d);
}
/** Where can we get from NFA state s traversing only epsilon transitions?
*
* A closure operation should abort if that computation has already
* been done or a computation with a conflicting context has already
* been done. If proposed NFA config's state and alt are the same
* there is potentially a problem. If the stack context is identical
* then clearly the exact same computation is proposed. If a context
* is a suffix of the other, then again the computation is in an
* identical context. beta $ and beta alpha $ are considered the same stack.
* We could walk configurations linearly doing the comparison instead
* of a set for exact matches but it's much slower because you can't
* do a Set lookup. I use exact match as ANTLR
* always detect the conflict later when checking for context suffixes...
* I check for left-recursive stuff and terminate before analysis to
* avoid need to do this more expensive computation.
*
* TODO: remove altNum if we don't reorder for loopback nodes
*/
public void closure(NFAState s, int altNum, NFAContext context,
SemanticContext semanticContext,
boolean collectPredicates,
List<NFAConfig> configs)
{
NFAConfig proposedNFAConfig = new NFAConfig(s, altNum, context, semanticContext);
if ( closureBusy.contains(proposedNFAConfig) ) return;
closureBusy.add(proposedNFAConfig);
// p itself is always in closure
configs.add(proposedNFAConfig);
if ( s instanceof RuleStopState ) {
ruleStopStateClosure(s, altNum, context, semanticContext, collectPredicates, configs);
}
else {
commonClosure(s, altNum, context, semanticContext, collectPredicates, configs);
}
}
// if we have context info and we're at rule stop state, do
// local follow for invokingRule and global follow for other links
void ruleStopStateClosure(NFAState s, int altNum, NFAContext context,
SemanticContext semanticContext,
boolean collectPredicates,
List<NFAConfig> configs)
{
Rule invokingRule = null;
if ( context!= NFAContext.EMPTY) {
// if stack not empty, get invoking rule from top of stack
invokingRule = context.returnState.rule;
}
//System.out.println("FOLLOW of "+s+" context="+context);
// follow all static FOLLOW links
int n = s.getNumberOfTransitions();
for (int i=0; i<n; i++) {
Transition t = s.transition(i);
if ( !(t instanceof EpsilonTransition) ) continue; // ignore EOF transitions
// Chase global FOLLOW links if they don't point at invoking rule
// else follow link to context state only
if ( t.target.rule != invokingRule ) {
//System.out.println("OFF TO "+t.target);
closure(t.target, altNum, context, semanticContext, collectPredicates, configs);
}
else { // t.target is in invoking rule; only follow context's link
if ( t.target == context.returnState ) {
//System.out.println("OFF TO CALL SITE "+t.target);
// go only to specific call site; pop context
NFAContext newContext = context.parent; // "pop" invoking state
closure(t.target, altNum, newContext, semanticContext, collectPredicates, configs);
}
}
}
return;
}
void commonClosure(NFAState s, int altNum, NFAContext context,
SemanticContext semanticContext, boolean collectPredicates,
List<NFAConfig> configs)
{
int n = s.getNumberOfTransitions();
for (int i=0; i<n; i++) {
Transition t = s.transition(i);
if ( t instanceof RuleTransition) {
NFAState retState = ((RuleTransition)t).followState;
NFAContext newContext = context;
if ( !context.contains(((RuleTransition)t).followState) ) { // !recursive?
// first create a new context and push onto call tree,
// recording the fact that we are invoking a rule and
// from which state.
newContext = new NFAContext(context, retState);
}
// traverse epsilon edge to new rule
closure(t.target, altNum, newContext, semanticContext, collectPredicates, configs);
}
else if ( t instanceof ActionTransition ) {
collectPredicates = false; // can't see past actions
closure(t.target, altNum, context, semanticContext, collectPredicates, configs);
}
else if ( t instanceof PredicateTransition ) {
SemanticContext labelContext = ((PredicateTransition)t).semanticContext;
SemanticContext newSemanticContext = semanticContext;
if ( collectPredicates ) {
// AND the previous semantic context with new pred
// int walkAlt =
// dfa.decisionNFAStartState.translateDisplayAltToWalkAlt(alt);
NFAState altLeftEdge = dfa.decisionNFAStartState.transition(altNum-1).target;
/*
System.out.println("state "+p.stateNumber+" alt "+alt+" walkAlt "+walkAlt+" trans to "+transition0.target);
System.out.println("DFA start state "+dfa.decisionNFAStartState.stateNumber);
System.out.println("alt left edge "+altLeftEdge.stateNumber+
", epsilon target "+
altLeftEdge.transition(0).target.stateNumber);
*/
// do not hoist syn preds from other rules; only get if in
// starting state's rule (i.e., context is empty)
if ( !labelContext.isSyntacticPredicate() || s==altLeftEdge ) {
System.out.println("&"+labelContext+" enclosingRule="+s.rule);
newSemanticContext =
SemanticContext.and(semanticContext, labelContext);
}
}
else {
// if we're not collecting, means we saw an action previously. that blocks this pred
hasPredicateBlockedByAction = true;
}
closure(t.target, altNum, context, newSemanticContext, collectPredicates, configs);
}
else if ( t.isEpsilon() ) {
closure(t.target, altNum, context, semanticContext, collectPredicates, configs);
}
}
}
/** for each NFA config in d, look for "predicate required" sign we set
* during nondeterminism resolution.
*
* Add the predicate edges sorted by the alternative number; I'm fairly
* sure that I could walk the configs backwards so they are added to
* the predDFATarget in the right order, but it's best to make sure.
* Predicates succeed in the order they are specifed. Alt i wins
* over alt i+1 if both predicates are true.
*/
protected void addPredicateTransitions(DFAState d) {
List<NFAConfig> configsWithPreds = new ArrayList<NFAConfig>();
// get a list of all configs with predicates
for (NFAConfig c : d.nfaConfigs) {
if ( c.resolvedWithPredicate) {
configsWithPreds.add(c);
}
}
// Sort ascending according to alt; alt i has higher precedence than i+1
Collections.sort(configsWithPreds,
new Comparator<NFAConfig>() {
public int compare(NFAConfig a, NFAConfig b) {
if ( a.alt < b.alt ) return -1;
else if ( a.alt > b.alt ) return 1;
return 0;
}
});
List<NFAConfig> predConfigsSortedByAlt = configsWithPreds;
// Now, we can add edges emanating from d for these preds in right order
for (NFAConfig c : predConfigsSortedByAlt) {
DFAState predDFATarget = dfa.newState();
// new DFA state is a target of the predicate from d
predDFATarget.addNFAConfig(c.state,
c.alt,
c.context,
c.semanticContext);
dfa.addAcceptState(c.alt, predDFATarget);
// add a transition to pred target from d
d.addEdge(new PredicateEdge(c.semanticContext, predDFATarget));
}
}
public Set<Integer> getUnreachableAlts() {
Set<Integer> unreachable = new HashSet<Integer>();
for (int alt=1; alt<=dfa.nAlts; alt++) {
if ( dfa.altToAcceptStates[alt]==null ) unreachable.add(alt);
}
return unreachable;
}
void issueAmbiguityWarnings() { resolver.issueAmbiguityWarnings(); }
}

26
tool/src/org/antlr/v4/analysis/Resolver.java
View File

@ -13,11 +13,11 @@ import java.util.*;
/** Code "module" that knows how to resolve LL(*) nondeterminisms. */
public class Resolver {
StackLimitedNFAToDFAConverter converter;
PredictionDFAFactory converter;
PredicateResolver semResolver;
public Resolver(StackLimitedNFAToDFAConverter converter) {
public Resolver(PredictionDFAFactory converter) {
this.converter = converter;
semResolver = new PredicateResolver(converter);
}
@ -101,21 +101,7 @@ public class Resolver {
// suffix of t.ctx or vice versa (if alts differ).
// Also a conflict if s.ctx or t.ctx is empty
boolean altConflict = s.alt != t.alt;
if ( !altConflict ) continue;
boolean ctxConflict = false;
if ( converter instanceof StackLimitedNFAToDFAConverter) {
// TODO: figure out if conflict rule is same for stack limited; as of 3/12/10 i think so
// doesn't matter how we limit stack, once we the same context on both
// stack tops (even if one is subset of other) we can't ever resolve ambig.
// We are at same NFA state, predicting diff alts, and if we ever fall off
// end of rule, we'll do the same thing in both cases.
//ctxConflict = s.context.equals(t.context);
ctxConflict = s.context.conflictsWith(t.context);
}
else {
ctxConflict = s.context.conflictsWith(t.context);
}
boolean ctxConflict = s.context.conflictsWith(t.context);
if ( altConflict && ctxConflict ) {
//System.out.println("ctx conflict between "+s+" and "+t);
ambiguousAlts.add(s.alt);
@ -130,11 +116,11 @@ public class Resolver {
}
public void resolveAmbiguities(DFAState d) {
if ( StackLimitedNFAToDFAConverter.debug ) {
if ( unused_StackLimitedNFAToDFAConverter.debug ) {
System.out.println("resolveNonDeterminisms "+d.toString());
}
Set<Integer> ambiguousAlts = getAmbiguousAlts(d);
if ( StackLimitedNFAToDFAConverter.debug && ambiguousAlts!=null ) {
if ( unused_StackLimitedNFAToDFAConverter.debug && ambiguousAlts!=null ) {
System.out.println("ambig alts="+ambiguousAlts);
}
@ -147,7 +133,7 @@ public class Resolver {
boolean resolved =
semResolver.tryToResolveWithSemanticPredicates(d, ambiguousAlts);
if ( resolved ) {
if ( StackLimitedNFAToDFAConverter.debug ) {
if ( unused_StackLimitedNFAToDFAConverter.debug ) {
System.out.println("resolved DFA state "+d.stateNumber+" with pred");
}
d.resolvedWithPredicates = true;

4
tool/src/org/antlr/v4/automata/DFA.java
View File

@ -1,6 +1,6 @@
package org.antlr.v4.automata;
import org.antlr.v4.analysis.StackLimitedNFAToDFAConverter;
import org.antlr.v4.analysis.PredictionDFAFactory;
import org.antlr.v4.misc.IntervalSet;
import org.antlr.v4.misc.OrderedHashSet;
import org.antlr.v4.tool.Grammar;
@ -54,7 +54,7 @@ public class DFA {
/** Unique state numbers per DFA */
int stateCounter = 0;
public StackLimitedNFAToDFAConverter converter;
public PredictionDFAFactory converter;
public DFA(Grammar g, DecisionState startState) {
this.g = g;