forgetest1
/
antlr
forked from jasder/antlr
1
0
Fork 0
Code Issues Pull Requests 1 Releases Wiki Activity

Initialize DFA.precedenceDfa when the DFA instance is created

This commit is contained in:
Sam Harwell 2015-01-31 16:10:03 -06:00
parent 84fb456aac
commit bc98e5b687
2 changed files with 37 additions and 73 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

49
runtime/Java/src/org/antlr/v4/runtime/atn/ParserATNSimulator.java
View File

@ -369,12 +369,17 @@ public class ParserATNSimulator extends ATNSimulator {
// But, do we still need an initial state?
try {
DFAState s0;
/* Threading note: dfa.s0 is the final value set on the DFA instance
* which affects branch choice in this method. If dfa.s0 is null
* (i.e. it has not been set), then we take the "slow" path through
* the initialization code to ensure a correct start state is used.
*/
if (dfa.s0 == null) {
if (dfa.isPrecedenceDfa()) {
// the start state for a precedence DFA depends on the current
// parser precedence, and is provided by a DFA method.
s0 = dfa.getPrecedenceStartState(parser.getPrecedence());
}
else {
// the start state for a "regular" DFA is just s0
s0 = dfa.s0;
}
if (s0 == null) {
if ( outerContext ==null ) outerContext = ParserRuleContext.EMPTY;
if ( debug || debug_list_atn_decisions ) {
System.out.println("predictATN decision "+ dfa.decision+
@ -382,25 +387,6 @@ public class ParserATNSimulator extends ATNSimulator {
", outerContext="+ outerContext.toString(parser));
}
/* If this is not a precedence DFA, we check the ATN start state
* to determine if this ATN start state is the decision for the
* closure block that determines whether a precedence rule
* should continue or complete.
*
* Threading note: cannot check the dfa.isPrecedenceDfa()
* condition here, because it's possible for that value to
* return true prior to dfa.s0 being set to the precedence start
* state. Calling dfa.setPrecedenceDfa(true) multiple times is
* safe, and the one-time performance overhead only occurs if
* multiple threads try to initialize the same DFA start state
* at the same time.
*/
if (dfa.atnStartState instanceof StarLoopEntryState) {
if (((StarLoopEntryState)dfa.atnStartState).precedenceRuleDecision) {
dfa.setPrecedenceDfa(true);
}
}
boolean fullCtx = false;
ATNConfigSet s0_closure =
computeStartState(dfa.atnStartState,
@ -422,19 +408,6 @@ public class ParserATNSimulator extends ATNSimulator {
s0 = addDFAState(dfa, new DFAState(s0_closure));
dfa.s0 = s0;
}
} else if (dfa.isPrecedenceDfa()) {
/* Threading note: if dfa.s0 was not null, then
* dfa.isPrecedenceDfa() must have already been set to the
* correct value.
*/
// the start state for a precedence DFA depends on the current
// parser precedence, and is provided by a DFA method.
s0 = dfa.getPrecedenceStartState(parser.getPrecedence());
}
else {
// the start state for a "regular" DFA is just s0
s0 = dfa.s0;
}
int alt = execATN(dfa, s0, input, index, outerContext);

61
runtime/Java/src/org/antlr/v4/runtime/dfa/DFA.java
View File

@ -34,6 +34,7 @@ import org.antlr.v4.runtime.Vocabulary;
import org.antlr.v4.runtime.VocabularyImpl;
import org.antlr.v4.runtime.atn.ATNConfigSet;
import org.antlr.v4.runtime.atn.DecisionState;
import org.antlr.v4.runtime.atn.StarLoopEntryState;
import org.antlr.v4.runtime.misc.NotNull;
import org.antlr.v4.runtime.misc.Nullable;
@ -63,10 +64,9 @@ public class DFA {
/**
* {@code true} if this DFA is for a precedence decision; otherwise,
* {@code false}. This is the backing field for {@link #isPrecedenceDfa},
* {@link #setPrecedenceDfa}.
* {@code false}. This is the backing field for {@link #isPrecedenceDfa}.
*/
private volatile boolean precedenceDfa;
private final boolean precedenceDfa;
public DFA(DecisionState atnStartState) {
this(atnStartState, 0);
@ -75,6 +75,20 @@ public class DFA {
public DFA(DecisionState atnStartState, int decision) {
this.atnStartState = atnStartState;
this.decision = decision;
boolean precedenceDfa = false;
if (atnStartState instanceof StarLoopEntryState) {
if (((StarLoopEntryState)atnStartState).precedenceRuleDecision) {
precedenceDfa = true;
DFAState precedenceState = new DFAState(new ATNConfigSet());
precedenceState.edges = new DFAState[0];
precedenceState.isAcceptState = false;
precedenceState.requiresFullContext = false;
this.s0 = precedenceState;
}
}
this.precedenceDfa = precedenceDfa;
}
/**
@ -149,43 +163,20 @@ public class DFA {
}
/**
* Sets whether this is a precedence DFA. If the specified value differs
* from the current DFA configuration, the following actions are taken;
* otherwise no changes are made to the current DFA.
*
* <ul>
* <li>The {@link #states} map is cleared</li>
* <li>If {@code precedenceDfa} is {@code false}, the initial state
* {@link #s0} is set to {@code null}; otherwise, it is initialized to a new
* {@link DFAState} with an empty outgoing {@link DFAState#edges} array to
* store the start states for individual precedence values.</li>
* <li>The {@link #precedenceDfa} field is updated</li>
* </ul>
* Sets whether this is a precedence DFA.
*
* @param precedenceDfa {@code true} if this is a precedence DFA; otherwise,
* {@code false}
*
* @throws UnsupportedOperationException if {@code precedenceDfa} does not
* match the value of {@link #isPrecedenceDfa} for the current DFA.
*
* @deprecated This method no longer performs any action.
*/
@Deprecated
public final void setPrecedenceDfa(boolean precedenceDfa) {
// Synchronize on this.states since we alter the map and other code
// which updates the DFA synchronizes on states, not on the DFA instance
// itself.
synchronized (this.states) {
if (this.precedenceDfa != precedenceDfa) {
this.states.clear();
// must set precedenceDfa before s0 to ensure correct branches
// are followed in adaptivePredict
this.precedenceDfa = precedenceDfa;
if (precedenceDfa) {
DFAState precedenceState = new DFAState(new ATNConfigSet());
precedenceState.edges = new DFAState[0];
precedenceState.isAcceptState = false;
precedenceState.requiresFullContext = false;
this.s0 = precedenceState;
}
else {
this.s0 = null;
}
}
if (precedenceDfa != isPrecedenceDfa()) {
throw new UnsupportedOperationException("The precedenceDfa field cannot change after a DFA is constructed.");
}
}