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tried optimization concerning recomputing DFA states in DFA, but didn't help much. left in as comment for now.

This commit is contained in:
Terence Parr 2012-08-01 14:51:37 -07:00
parent 0cfe3b4206
commit b0c9a9c7c2
1 changed files with 21 additions and 0 deletions
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21
runtime/Java/src/org/antlr/v4/runtime/atn/ParserATNSimulator.java
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@ -475,8 +475,29 @@ public class ParserATNSimulator<Symbol extends Token> extends ATNSimulator {
// will get error no matter what.
throw noViableAlt(input, outerContext, previous, startIndex);
}
// create new target state; we'll add to DFA after it's complete
DFAState D = new DFAState(reach);
// It's often the case that D will already exist in the DFA
// and so it's a waste to compute all of the fields over the next
// big chunk of code. However, I tried inserting the following
// short circuit, but it didn't have much effect. I
// figured that this would be a big impact for multi threading,
// but it also didn't see much of an impact.
// synchronized (dfa) {
// DFAState existing = dfa.states.get(D);
// if ( existing!=null ) {
// addDFAEdge(dfa, previousD, t, existing);
// if ( existing.isAcceptState ) return existing.prediction;
// previous = D.configs;
// previousD = D;
// input.consume();
// t = input.LA(1);
// continue;
// }
// }
int predictedAlt = getUniqueAlt(reach);
if ( predictedAlt!=ATN.INVALID_ALT_NUMBER ) {
// NO CONFLICT, UNIQUE PREDICTED ALT