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[Java:Runtime] perf(runtime): Optimize thread safety and performance for DFA state management #4842

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[Java:Runtime] perf(runtime): Optimize thread safety and performance for DFA state management #4842

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19 changes: 9 additions & 10 deletions runtime/Java/src/org/antlr/v4/runtime/atn/LexerATNSimulator.java
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Original file line number Diff line number Diff line change
Expand Up @@ -687,18 +687,17 @@ protected DFAState addDFAState(ATNConfigSet configs) {
}

DFA dfa = decisionToDFA[mode];
synchronized (dfa.states) {
DFAState existing = dfa.states.get(proposed);
if ( existing!=null ) return existing;

DFAState newState = proposed;
DFAState existing = dfa.states.get(proposed);
if ( existing!=null ) return existing;

newState.stateNumber = dfa.states.size();
configs.setReadonly(true);
newState.configs = configs;
dfa.states.put(newState, newState);
return newState;
}
DFAState newState = proposed;

newState.stateNumber = dfa.states.size();
configs.setReadonly(true);
newState.configs = configs;
dfa.states.put(newState, newState);
return newState;
}


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28 changes: 13 additions & 15 deletions runtime/Java/src/org/antlr/v4/runtime/atn/ParserATNSimulator.java
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Original file line number Diff line number Diff line change
Expand Up @@ -2101,26 +2101,24 @@ protected DFAState addDFAState(DFA dfa, DFAState D) {
return D;
}

synchronized (dfa.states) {
DFAState existing = dfa.states.get(D);
DFAState existing = dfa.states.get(D);

if ( existing!=null ) {
if ( trace_atn_sim ) System.out.println("addDFAState " + D + " exists");
return existing;
}
if ( existing!=null ) {
if ( trace_atn_sim ) System.out.println("addDFAState " + D + " exists");
return existing;
}

D.stateNumber = dfa.states.size();
D.stateNumber = dfa.states.size();

if (!D.configs.isReadonly()) {
D.configs.optimizeConfigs(this);
D.configs.setReadonly(true);
}
if (!D.configs.isReadonly()) {
D.configs.optimizeConfigs(this);
D.configs.setReadonly(true);
}

if ( trace_atn_sim ) System.out.println("addDFAState new "+D);
if ( trace_atn_sim ) System.out.println("addDFAState new "+D);

dfa.states.put(D, D);
return D;
}
dfa.states.put(D, D);
return D;
}

protected void reportAttemptingFullContext(DFA dfa, BitSet conflictingAlts, ATNConfigSet configs, int startIndex, int stopIndex) {
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4 changes: 2 additions & 2 deletions runtime/Java/src/org/antlr/v4/runtime/dfa/DFA.java
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Expand Up @@ -16,17 +16,17 @@
import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;

public class DFA {
/** A set of all DFA states. Use {@link Map} so we can get old state back
* ({@link Set} only allows you to see if it's there).
*/

public final Map<DFAState, DFAState> states = new HashMap<DFAState, DFAState>();
public final Map<DFAState, DFAState> states = new ConcurrentHashMap<>();

public volatile DFAState s0;

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