LibJS: Add fast_is<T>() for things that were hot in RTTI

This gives a ~4% speedup when parsing the largest Discord JS file.

Userland/Libraries/LibJS/AST.h

@@ -67,7 +67,18 @@ public:
     virtual bool is_identifier() const { return false; }
     virtual bool is_scope_node() const { return false; }
     virtual bool is_program() const { return false; }
+    virtual bool is_class_declaration() const { return false; }
     virtual bool is_function_declaration() const { return false; }
+    virtual bool is_variable_declaration() const { return false; }
+    virtual bool is_import_call() const { return false; }
+    virtual bool is_array_expression() const { return false; }
+    virtual bool is_object_expression() const { return false; }
+    virtual bool is_string_literal() const { return false; }
+    virtual bool is_update_expression() const { return false; }
+    virtual bool is_call_expression() const { return false; }
+    virtual bool is_labelled_statement() const { return false; }
+    virtual bool is_iteration_statement() const { return false; }
+    virtual bool is_class_method() const { return false; }
 
 protected:
     explicit ASTNode(SourceRange source_range)
@@ -106,6 +117,8 @@ public:
     NonnullRefPtr<Statement>& labelled_item() { return m_labelled_item; }
 
 private:
+    virtual bool is_labelled_statement() const final { return true; }
+
     FlyString m_label;
     NonnullRefPtr<Statement> m_labelled_item;
 };
@@ -126,6 +139,9 @@ public:
     using Statement::Statement;
 
     virtual Completion loop_evaluation(Interpreter&, GlobalObject&, Vector<FlyString> const&) const = 0;
+
+private:
+    virtual bool is_iteration_statement() const final { return true; }
 };
 
 class EmptyStatement final : public Statement {
@@ -1124,6 +1140,8 @@ public:
     bool is_use_strict_directive() const { return m_is_use_strict_directive; };
 
 private:
+    virtual bool is_string_literal() const override { return true; }
+
     String m_value;
     bool m_is_use_strict_directive;
 };
@@ -1272,6 +1290,7 @@ public:
     virtual Optional<FlyString> private_bound_identifier() const override;
 
 private:
+    virtual bool is_class_method() const override { return true; }
     NonnullRefPtr<Expression> m_key;
     NonnullRefPtr<FunctionExpression> m_function;
     Kind m_kind;
@@ -1387,6 +1406,8 @@ public:
     StringView name() const { return m_class_expression->name(); }
 
 private:
+    virtual bool is_class_declaration() const override { return true; }
+
     friend ExportStatement;
 
     NonnullRefPtr<ClassExpression> m_class_expression;
@@ -1439,6 +1460,8 @@ public:
     Expression const& callee() const { return m_callee; }
 
 protected:
+    virtual bool is_call_expression() const override { return true; }
+
     Completion throw_type_error_for_callee(Interpreter&, GlobalObject&, Value callee_value, StringView call_type) const;
 
     NonnullRefPtr<Expression> m_callee;
@@ -1546,6 +1569,8 @@ public:
     virtual void generate_bytecode(Bytecode::Generator&) const override;
 
 private:
+    virtual bool is_update_expression() const override { return true; }
+
     UpdateOp m_op;
     NonnullRefPtr<Expression> m_argument;
     bool m_prefixed;
@@ -1614,6 +1639,8 @@ public:
     virtual bool is_lexical_declaration() const override { return m_declaration_kind != DeclarationKind::Var; }
 
 private:
+    virtual bool is_variable_declaration() const override { return true; }
+
     DeclarationKind m_declaration_kind;
     NonnullRefPtrVector<VariableDeclarator> m_declarations;
 };
@@ -1672,6 +1699,8 @@ public:
     Optional<SourceRange> const& invalid_property_range() const { return m_first_invalid_property_range; }
 
 private:
+    virtual bool is_object_expression() const override { return true; }
+
     NonnullRefPtrVector<ObjectProperty> m_properties;
     Optional<SourceRange> m_first_invalid_property_range;
 };
@@ -1691,6 +1720,8 @@ public:
     virtual void generate_bytecode(Bytecode::Generator&) const override;
 
 private:
+    virtual bool is_array_expression() const override { return true; }
+
     Vector<RefPtr<Expression>> m_elements;
 };
 
@@ -1851,6 +1882,8 @@ public:
     virtual Completion execute(Interpreter&, GlobalObject&) const override;
 
 private:
+    virtual bool is_import_call() const override { return true; }
+
     NonnullRefPtr<Expression> m_specifier;
     RefPtr<Expression> m_options;
 };
@@ -2070,7 +2103,40 @@ inline bool ASTNode::fast_is<ScopeNode>() const { return is_scope_node(); }
 template<>
 inline bool ASTNode::fast_is<Program>() const { return is_program(); }
 
+template<>
+inline bool ASTNode::fast_is<ClassDeclaration>() const { return is_class_declaration(); }
+
 template<>
 inline bool ASTNode::fast_is<FunctionDeclaration>() const { return is_function_declaration(); }
 
+template<>
+inline bool ASTNode::fast_is<VariableDeclaration>() const { return is_variable_declaration(); }
+
+template<>
+inline bool ASTNode::fast_is<ArrayExpression>() const { return is_array_expression(); }
+
+template<>
+inline bool ASTNode::fast_is<ObjectExpression>() const { return is_object_expression(); }
+
+template<>
+inline bool ASTNode::fast_is<ImportCall>() const { return is_import_call(); }
+
+template<>
+inline bool ASTNode::fast_is<StringLiteral>() const { return is_string_literal(); }
+
+template<>
+inline bool ASTNode::fast_is<UpdateExpression>() const { return is_update_expression(); }
+
+template<>
+inline bool ASTNode::fast_is<CallExpression>() const { return is_call_expression(); }
+
+template<>
+inline bool ASTNode::fast_is<LabelledStatement>() const { return is_labelled_statement(); }
+
+template<>
+inline bool ASTNode::fast_is<IterationStatement>() const { return is_iteration_statement(); }
+
+template<>
+inline bool ASTNode::fast_is<ClassMethod>() const { return is_class_method(); }
+
 }

Userland/Libraries/LibJS/Runtime/ECMAScriptFunctionObject.h

@@ -134,4 +134,7 @@ private:
     FunctionKind m_kind : 3 { FunctionKind::Normal };
 };
 
+template<>
+inline bool Object::fast_is<ECMAScriptFunctionObject>() const { return is_ecmascript_function_object(); }
+
 }