LibJS: Memoize failed calls of try_parse_arrow_function_expression()

luteresa · Apr 12, 2021 · 8c80eb8 · 8c80eb8
1 parent 435bd84
commit 8c80eb8
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Showing 2 changed files with 46 additions and 4 deletions.
diff --git a/Userland/Libraries/LibJS/Parser.cpp b/Userland/Libraries/LibJS/Parser.cpp
@@ -627,11 +627,14 @@ NonnullRefPtr<Expression> Parser::parse_primary_expression()
 
  switch (m_parser_state.m_current_token.type()) {
  case TokenType::ParenOpen: {
+ auto paren_position = position();
  consume(TokenType::ParenOpen);
- if (match(TokenType::ParenClose) || match(TokenType::Identifier) || match(TokenType::TripleDot)) {
+ if ((match(TokenType::ParenClose) || match(TokenType::Identifier) || match(TokenType::TripleDot)) && !try_parse_arrow_function_expression_failed_at_position(paren_position)) {
  auto arrow_function_result = try_parse_arrow_function_expression(true);
  if (!arrow_function_result.is_null())
  return arrow_function_result.release_nonnull();
+
+ set_try_parse_arrow_function_expression_failed_at_position(paren_position, true);
  }
  auto expression = parse_expression(0);
  consume(TokenType::ParenClose);
@@ -651,9 +654,13 @@ NonnullRefPtr<Expression> Parser::parse_primary_expression()
  syntax_error("'super' keyword unexpected here");
  return create_ast_node<SuperExpression>({ m_parser_state.m_current_token.filename(), rule_start.position(), position() });
  case TokenType::Identifier: {
- auto arrow_function_result = try_parse_arrow_function_expression(false);
- if (!arrow_function_result.is_null())
- return arrow_function_result.release_nonnull();
+ if (!try_parse_arrow_function_expression_failed_at_position(position())) {
+ auto arrow_function_result = try_parse_arrow_function_expression(false);
+ if (!arrow_function_result.is_null())
+ return arrow_function_result.release_nonnull();
+
+ set_try_parse_arrow_function_expression_failed_at_position(position(), true);
+ }
  return create_ast_node<Identifier>({ m_parser_state.m_current_token.filename(), rule_start.position(), position() }, consume().value());
  }
  case TokenType::NumericLiteral:
@@ -2039,6 +2046,20 @@ Position Parser::position() const
  };
 }
 
+bool Parser::try_parse_arrow_function_expression_failed_at_position(const Position& position) const
+{
+ auto it = m_token_memoizations.find(position);
+ if (it == m_token_memoizations.end())
+ return false;
+
+ return (*it).value.try_parse_arrow_function_expression_failed;
+}
+
+void Parser::set_try_parse_arrow_function_expression_failed_at_position(const Position& position, bool failed)
+{
+ m_token_memoizations.set(position, { failed });
+}
+
 void Parser::syntax_error(const String& message, Optional<Position> position)
 {
  if (!position.has_value())

diff --git a/Userland/Libraries/LibJS/Parser.h b/Userland/Libraries/LibJS/Parser.h
@@ -147,6 +147,10 @@ class Parser {
  }
  }
 
+ struct TokenMemoization {
+ bool try_parse_arrow_function_expression_failed;
+ };
+
 private:
  friend class ScopePusher;
 
@@ -172,6 +176,9 @@ class Parser {
  void discard_saved_state();
  Position position() const;
 
+ bool try_parse_arrow_function_expression_failed_at_position(const Position&) const;
+ void set_try_parse_arrow_function_expression_failed_at_position(const Position&, bool);
+
  struct RulePosition {
  AK_MAKE_NONCOPYABLE(RulePosition);
  AK_MAKE_NONMOVABLE(RulePosition);
@@ -220,9 +227,23 @@ class Parser {
  explicit ParserState(Lexer);
  };
 
+ class PositionKeyTraits {
+ public:
+ static int hash(const Position& position)
+ {
+ return int_hash(position.line) ^ int_hash(position.column);
+ }
+
+ static bool equals(const Position& a, const Position& b)
+ {
+ return a.column == b.column && a.line == b.line;
+ }
+ };
+
  Vector<Position> m_rule_starts;
  ParserState m_parser_state;
  FlyString m_filename;
  Vector<ParserState> m_saved_state;
+ HashMap<Position, TokenMemoization, PositionKeyTraits> m_token_memoizations;
 };
 }