[C++] Drastically improve multi-threaded performance (antlr#3550)

Thanks guys. A major advancement.

runtime-testsuite/resources/org/antlr/v4/test/runtime/templates/Cpp.test.stg

@@ -93,7 +93,7 @@ public:
   virtual std::unique_ptr\<antlr4::Token> nextToken() override {
     if (dynamic_cast\<PositionAdjustingLexerATNSimulator *>(_interpreter) == nullptr) {
       delete _interpreter;
-      _interpreter = new PositionAdjustingLexerATNSimulator(this, _atn, _decisionToDFA, _sharedContextCache);
+      _interpreter = new PositionAdjustingLexerATNSimulator(this, *_atn, *_decisionToDFA, _sharedContextCache);
     }
 
     return antlr4::Lexer::nextToken();

runtime/Cpp/runtime/src/Parser.cpp

@@ -28,10 +28,25 @@
 
 using namespace antlr4;
 using namespace antlr4::atn;
-
 using namespace antlrcpp;
 
-std::map<std::vector<uint16_t>, atn::ATN> Parser::bypassAltsAtnCache;
+namespace {
+
+struct BypassAltsAtnCache final {
+  std::shared_mutex mutex;
+  /// This field maps from the serialized ATN string to the deserialized <seealso cref="ATN"/> with
+  /// bypass alternatives.
+  ///
+  /// <seealso cref= ATNDeserializationOptions#isGenerateRuleBypassTransitions() </seealso>
+  std::map<std::vector<uint16_t>, std::unique_ptr<const atn::ATN>> map;
+};
+
+BypassAltsAtnCache* getBypassAltsAtnCache() {
+  static BypassAltsAtnCache* const instance = new BypassAltsAtnCache();
+  return instance;
+}
+
+}
 
 Parser::TraceListener::TraceListener(Parser *outerInstance_) : outerInstance(outerInstance_) {
 }
@@ -214,25 +229,30 @@ TokenFactory<CommonToken>* Parser::getTokenFactory() {
 
 
 const atn::ATN& Parser::getATNWithBypassAlts() {
-  std::vector<uint16_t> serializedAtn = getSerializedATN();
+  const std::vector<uint16_t> &serializedAtn = getSerializedATN();
   if (serializedAtn.empty()) {
     throw UnsupportedOperationException("The current parser does not support an ATN with bypass alternatives.");
   }
-
-  std::lock_guard<std::mutex> lck(_mutex);
-
   // XXX: using the entire serialized ATN as key into the map is a big resource waste.
   //      How large can that thing become?
-  if (bypassAltsAtnCache.find(serializedAtn) == bypassAltsAtnCache.end())
+  auto *cache = getBypassAltsAtnCache();
   {
-    atn::ATNDeserializationOptions deserializationOptions;
-    deserializationOptions.setGenerateRuleBypassTransitions(true);
-
-    atn::ATNDeserializer deserializer(deserializationOptions);
-    bypassAltsAtnCache[serializedAtn] = deserializer.deserialize(serializedAtn);
+    std::shared_lock<std::shared_mutex> lock(cache->mutex);
+    auto existing = cache->map.find(serializedAtn);
+    if (existing != cache->map.end()) {
+      return *existing->second;
+    }
   }
 
-  return bypassAltsAtnCache[serializedAtn];
+  atn::ATNDeserializationOptions deserializationOptions;
+  deserializationOptions.setGenerateRuleBypassTransitions(true);
+  atn::ATNDeserializer deserializer(deserializationOptions);
+  auto atn = deserializer.deserialize(serializedAtn);
+
+  {
+    std::unique_lock<std::shared_mutex> lock(cache->mutex);
+    return *cache->map.insert(std::make_pair(serializedAtn, std::move(atn))).first->second;
+  }
 }
 
 tree::pattern::ParseTreePattern Parser::compileParseTreePattern(const std::string &pattern, int patternRuleIndex) {

runtime/Cpp/runtime/src/Parser.h

@@ -448,12 +448,6 @@ namespace antlr4 {
     tree::ParseTreeTracker _tracker;
 
   private:
-    /// This field maps from the serialized ATN string to the deserialized <seealso cref="ATN"/> with
-    /// bypass alternatives.
-    ///
-    /// <seealso cref= ATNDeserializationOptions#isGenerateRuleBypassTransitions() </seealso>
-    static std::map<std::vector<uint16_t>, atn::ATN> bypassAltsAtnCache;
-
     /// When setTrace(true) is called, a reference to the
     /// TraceListener is stored here so it can be easily removed in a
     /// later call to setTrace(false). The listener itself is

runtime/Cpp/runtime/src/Recognizer.h

@@ -53,7 +53,7 @@ namespace antlr4 {
     /// For interpreters, we don't know their serialized ATN despite having
     /// created the interpreter from it.
     /// </summary>
-    virtual const std::vector<uint16_t> getSerializedATN() const {
+    virtual const std::vector<uint16_t>& getSerializedATN() const {
       throw "there is no serialized ATN";
     }
 

runtime/Cpp/runtime/src/atn/ATN.cpp

@@ -20,67 +20,16 @@ using namespace antlr4;
 using namespace antlr4::atn;
 using namespace antlrcpp;
 
-ATN::ATN() : ATN(ATNType::LEXER, 0) {
-}
+ATN::ATN() : ATN(ATNType::LEXER, 0) {}
 
-ATN::ATN(ATN &&other) {
-  // All source vectors are implicitly cleared by the moves.
-  states = std::move(other.states);
-  decisionToState = std::move(other.decisionToState);
-  ruleToStartState = std::move(other.ruleToStartState);
-  ruleToStopState = std::move(other.ruleToStopState);
-  grammarType = std::move(other.grammarType);
-  maxTokenType = std::move(other.maxTokenType);
-  ruleToTokenType = std::move(other.ruleToTokenType);
-  lexerActions = std::move(other.lexerActions);
-  modeToStartState = std::move(other.modeToStartState);
-}
-
-ATN::ATN(ATNType grammarType_, size_t maxTokenType_) : grammarType(grammarType_), maxTokenType(maxTokenType_) {
-}
+ATN::ATN(ATNType grammarType_, size_t maxTokenType_) : grammarType(grammarType_), maxTokenType(maxTokenType_) {}
 
 ATN::~ATN() {
   for (ATNState *state : states) {
     delete state;
   }
 }
 
-/**
- * Required to be defined (even though not used) as we have an explicit move assignment operator.
- */
-ATN& ATN::operator = (ATN &other) noexcept {
-  states = other.states;
-  decisionToState = other.decisionToState;
-  ruleToStartState = other.ruleToStartState;
-  ruleToStopState = other.ruleToStopState;
-  grammarType = other.grammarType;
-  maxTokenType = other.maxTokenType;
-  ruleToTokenType = other.ruleToTokenType;
-  lexerActions = other.lexerActions;
-  modeToStartState = other.modeToStartState;
-
-  return *this;
-}
-
-/**
- * Explicit move assignment operator to make this the preferred assignment. With implicit copy/move assignment
- * operators it seems the copy operator is preferred causing trouble when releasing the allocated ATNState instances.
- */
-ATN& ATN::operator = (ATN &&other) noexcept {
-  // All source vectors are implicitly cleared by the moves.
-  states = std::move(other.states);
-  decisionToState = std::move(other.decisionToState);
-  ruleToStartState = std::move(other.ruleToStartState);
-  ruleToStopState = std::move(other.ruleToStopState);
-  grammarType = std::move(other.grammarType);
-  maxTokenType = std::move(other.maxTokenType);
-  ruleToTokenType = std::move(other.ruleToTokenType);
-  lexerActions = std::move(other.lexerActions);
-  modeToStartState = std::move(other.modeToStartState);
-
-  return *this;
-}
-
 misc::IntervalSet ATN::nextTokens(ATNState *s, RuleContext *ctx) const {
   LL1Analyzer analyzer(*this);
   return analyzer.LOOK(s, ctx);
@@ -89,7 +38,7 @@ misc::IntervalSet ATN::nextTokens(ATNState *s, RuleContext *ctx) const {
 
 misc::IntervalSet const& ATN::nextTokens(ATNState *s) const {
   if (!s->_nextTokenUpdated) {
-    std::unique_lock<std::mutex> lock { _mutex };
+    std::unique_lock<std::mutex> lock(_mutex);
     if (!s->_nextTokenUpdated) {
       s->_nextTokenWithinRule = nextTokens(s, nullptr);
       s->_nextTokenUpdated = true;

runtime/Cpp/runtime/src/atn/ATN.h

@@ -16,15 +16,27 @@
 namespace antlr4 {
 namespace atn {
 
+  class LexerATNSimulator;
+  class ParserATNSimulator;
+
   class ANTLR4CPP_PUBLIC ATN {
   public:
     static constexpr size_t INVALID_ALT_NUMBER = 0;
 
     /// Used for runtime deserialization of ATNs from strings.
     ATN();
-    ATN(ATN &&other);
+
     ATN(ATNType grammarType, size_t maxTokenType);
-    virtual ~ATN();
+
+    ATN(const ATN&) = delete;
+
+    ATN(ATN&&) = delete;
+
+    ~ATN();
+
+    ATN& operator=(const ATN&) = delete;
+
+    ATN& operator=(ATN&&) = delete;
 
     std::vector<ATNState *> states;
 
@@ -60,33 +72,30 @@ namespace atn {
 
     std::vector<TokensStartState *> modeToStartState;
 
-    ATN& operator = (ATN &other) noexcept;
-    ATN& operator = (ATN &&other) noexcept;
-
     /// <summary>
     /// Compute the set of valid tokens that can occur starting in state {@code s}.
     ///  If {@code ctx} is null, the set of tokens will not include what can follow
     ///  the rule surrounding {@code s}. In other words, the set will be
     ///  restricted to tokens reachable staying within {@code s}'s rule.
     /// </summary>
-    virtual misc::IntervalSet nextTokens(ATNState *s, RuleContext *ctx) const;
+    misc::IntervalSet nextTokens(ATNState *s, RuleContext *ctx) const;
 
     /// <summary>
     /// Compute the set of valid tokens that can occur starting in {@code s} and
     /// staying in same rule. <seealso cref="Token#EPSILON"/> is in set if we reach end of
     /// rule.
     /// </summary>
-    virtual misc::IntervalSet const& nextTokens(ATNState *s) const;
+    misc::IntervalSet const& nextTokens(ATNState *s) const;
 
-    virtual void addState(ATNState *state);
+    void addState(ATNState *state);
 
-    virtual void removeState(ATNState *state);
+    void removeState(ATNState *state);
 
-    virtual int defineDecisionState(DecisionState *s);
+    int defineDecisionState(DecisionState *s);
 
-    virtual DecisionState *getDecisionState(size_t decision) const;
+    DecisionState *getDecisionState(size_t decision) const;
 
-    virtual size_t getNumberOfDecisions() const;
+    size_t getNumberOfDecisions() const;
 
     /// <summary>
     /// Computes the set of input symbols which could follow ATN state number
@@ -106,12 +115,17 @@ namespace atn {
     /// specified state in the specified context. </returns>
     /// <exception cref="IllegalArgumentException"> if the ATN does not contain a state with
     /// number {@code stateNumber} </exception>
-    virtual misc::IntervalSet getExpectedTokens(size_t stateNumber, RuleContext *context) const;
+    misc::IntervalSet getExpectedTokens(size_t stateNumber, RuleContext *context) const;
 
     std::string toString() const;
 
   private:
+    friend class LexerATNSimulator;
+    friend class ParserATNSimulator;
+
     mutable std::mutex _mutex;
+    mutable std::shared_mutex _stateMutex;
+    mutable std::shared_mutex _edgeMutex;
   };
 
 } // namespace atn