jasder
/
antlr
1
0
Fork 1
Code Issues Pull Requests Releases 1 Wiki Activity

Add ATN optimization to collapse multiple alternatives to a single SetTransition where possible. Currently disabled for parser grammars since the code generator doesn't support set transitions.

This commit is contained in:
Sam Harwell 2012-07-31 13:32:55 -05:00
parent 1f4df2ea5a
commit 5019278204
2 changed files with 104 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
runtime/Java/src/org/antlr/v4/runtime/atn/ATNState.java
View File

@ -137,6 +137,10 @@ public class ATNState {
transitions.set(i, e);
}
public Transition removeTransition(int index) {
return transitions.remove(index);
}
public int getStateType() {
return serializationTypes.get(this.getClass());
}

100
tool/src/org/antlr/v4/automata/ATNOptimizer.java
View File

@ -32,8 +32,19 @@ package org.antlr.v4.automata;
import org.antlr.v4.runtime.atn.ATN;
import org.antlr.v4.runtime.atn.ATNState;
import org.antlr.v4.runtime.atn.AtomTransition;
import org.antlr.v4.runtime.atn.BlockEndState;
import org.antlr.v4.runtime.atn.DecisionState;
import org.antlr.v4.runtime.atn.EpsilonTransition;
import org.antlr.v4.runtime.atn.NotSetTransition;
import org.antlr.v4.runtime.atn.RangeTransition;
import org.antlr.v4.runtime.atn.SetTransition;
import org.antlr.v4.runtime.atn.Transition;
import org.antlr.v4.runtime.misc.Interval;
import org.antlr.v4.runtime.misc.IntervalSet;
import org.antlr.v4.runtime.misc.NotNull;
import org.antlr.v4.tool.Grammar;
import org.antlr.v4.tool.Rule;
import java.util.List;
@ -44,9 +55,98 @@ import java.util.List;
public class ATNOptimizer {
public static void optimize(@NotNull Grammar g, @NotNull ATN atn) {
optimizeSets(g, atn);
optimizeStates(atn);
}
private static void optimizeSets(Grammar g, ATN atn) {
if (g.isParser()) {
// parser codegen doesn't currently support SetTransition
return;
}
int removedStates = 0;
List<DecisionState> decisions = atn.decisionToState;
for (DecisionState decision : decisions) {
if (decision.ruleIndex >= 0) {
Rule rule = g.getRule(decision.ruleIndex);
if (Character.isLowerCase(rule.name.charAt(0))) {
// parser codegen doesn't currently support SetTransition
continue;
}
}
IntervalSet setTransitions = new IntervalSet();
for (int i = 0; i < decision.getNumberOfTransitions(); i++) {
Transition epsTransition = decision.transition(i);
if (!(epsTransition instanceof EpsilonTransition)) {
continue;
}
if (epsTransition.target.getNumberOfTransitions() != 1) {
continue;
}
Transition transition = epsTransition.target.transition(0);
if (!(transition.target instanceof BlockEndState)) {
continue;
}
if (transition instanceof NotSetTransition) {
// TODO: not yet implemented
continue;
}
if (transition instanceof AtomTransition
|| transition instanceof RangeTransition
|| transition instanceof SetTransition)
{
setTransitions.add(i);
}
}
// due to min alt resolution policies, can only collapse sequential alts
for (int i = setTransitions.getIntervals().size() - 1; i >= 0; i--) {
Interval interval = setTransitions.getIntervals().get(i);
if (interval.length() <= 1) {
continue;
}
ATNState blockEndState = decision.transition(interval.a).target.transition(0).target;
IntervalSet matchSet = new IntervalSet();
for (int j = interval.a; j <= interval.b; j++) {
Transition matchTransition = decision.transition(j).target.transition(0);
if (matchTransition instanceof NotSetTransition) {
throw new UnsupportedOperationException("Not yet implemented.");
} else {
matchSet.addAll(matchTransition.label());
}
}
Transition newTransition;
if (matchSet.getIntervals().size() == 1) {
if (matchSet.size() == 1) {
newTransition = new AtomTransition(blockEndState, matchSet.getMinElement());
} else {
Interval matchInterval = matchSet.getIntervals().get(0);
newTransition = new RangeTransition(blockEndState, matchInterval.a, matchInterval.b);
}
} else {
newTransition = new SetTransition(blockEndState, matchSet);
}
decision.transition(interval.a).target.setTransition(0, newTransition);
for (int j = interval.a + 1; j <= interval.b; j++) {
Transition removed = decision.removeTransition(interval.a + 1);
atn.removeState(removed.target);
removedStates++;
}
}
}
System.out.println("ATN optimizer removed " + removedStates + " states by collapsing sets.");
}
private static void optimizeStates(ATN atn) {
List<ATNState> states = atn.states;