whee.diff

commit 5def8e66eeb15278a55055e06ce798059459abed
Author: Andreas Kling <kling@serenityos.org>
Date:   Fri Oct 8 02:25:46 2021 +0200

    LibJS: WIP optimization

diff --git a/Userland/Libraries/LibJS/AST.cpp b/Userland/Libraries/LibJS/AST.cpp
index 8eb93d3ded..1f5928da62 100644
--- a/Userland/Libraries/LibJS/AST.cpp
+++ b/Userland/Libraries/LibJS/AST.cpp
@@ -195,7 +195,7 @@ Value FunctionExpression::instantiate_ordinary_function_expression(Interpreter&
         scope->create_immutable_binding(global_object, name(), false);
     }
 
-    auto closure = ECMAScriptFunctionObject::create(global_object, used_name, body(), parameters(), function_length(), scope, kind(), is_strict_mode(), might_need_arguments_object(), is_arrow_function());
+    auto closure = ECMAScriptFunctionObject::create(global_object, used_name, body(), parameters(), function_length(), scope, kind(), is_strict_mode(), might_need_arguments_object(), might_have_direct_eval(), is_arrow_function());
 
     // FIXME: 6. Perform SetFunctionName(closure, name).
     // FIXME: 7. Perform MakeConstructor(closure).
@@ -3190,7 +3190,7 @@ void ScopeNode::block_declaration_instantiation(GlobalObject& global_object, Env
 
         if (is<FunctionDeclaration>(declaration)) {
             auto& function_declaration = static_cast<FunctionDeclaration const&>(declaration);
-            auto* function = ECMAScriptFunctionObject::create(global_object, function_declaration.name(), function_declaration.body(), function_declaration.parameters(), function_declaration.function_length(), environment, function_declaration.kind(), function_declaration.is_strict_mode(), function_declaration.might_need_arguments_object());
+            auto* function = ECMAScriptFunctionObject::create(global_object, function_declaration.name(), function_declaration.body(), function_declaration.parameters(), function_declaration.function_length(), environment, function_declaration.kind(), function_declaration.is_strict_mode(), function_declaration.might_need_arguments_object(), function_declaration.might_have_direct_eval());
             VERIFY(is<DeclarativeEnvironment>(*environment));
             static_cast<DeclarativeEnvironment&>(*environment).initialize_or_set_mutable_binding({}, global_object, function_declaration.name(), function);
         }
@@ -3334,7 +3334,7 @@ ThrowCompletionOr<void> Program::global_declaration_instantiation(Interpreter& i
     });
 
     for (auto& declaration : functions_to_initialize) {
-        auto* function = ECMAScriptFunctionObject::create(global_object, declaration.name(), declaration.body(), declaration.parameters(), declaration.function_length(), &global_environment, declaration.kind(), declaration.is_strict_mode(), declaration.might_need_arguments_object());
+        auto* function = ECMAScriptFunctionObject::create(global_object, declaration.name(), declaration.body(), declaration.parameters(), declaration.function_length(), &global_environment, declaration.kind(), declaration.is_strict_mode(), declaration.might_need_arguments_object(), declaration.might_have_direct_eval());
         global_environment.create_global_function_binding(declaration.name(), function, false);
         if (auto* exception = interpreter.exception())
             return throw_completion(exception->value());
diff --git a/Userland/Libraries/LibJS/AST.h b/Userland/Libraries/LibJS/AST.h
index 3952c5a8db..72eae6a10b 100644
--- a/Userland/Libraries/LibJS/AST.h
+++ b/Userland/Libraries/LibJS/AST.h
@@ -441,11 +441,12 @@ public:
     i32 function_length() const { return m_function_length; }
     bool is_strict_mode() const { return m_is_strict_mode; }
     bool might_need_arguments_object() const { return m_might_need_arguments_object; }
+    bool might_have_direct_eval() const { return m_might_have_direct_eval; }
     bool is_arrow_function() const { return m_is_arrow_function; }
     FunctionKind kind() const { return m_kind; }
 
 protected:
-    FunctionNode(FlyString name, NonnullRefPtr<Statement> body, Vector<Parameter> parameters, i32 function_length, FunctionKind kind, bool is_strict_mode, bool might_need_arguments_object, bool is_arrow_function)
+    FunctionNode(FlyString name, NonnullRefPtr<Statement> body, Vector<Parameter> parameters, i32 function_length, FunctionKind kind, bool is_strict_mode, bool might_need_arguments_object, bool might_have_direct_eval, bool is_arrow_function)
         : m_name(move(name))
         , m_body(move(body))
         , m_parameters(move(parameters))
@@ -453,6 +454,7 @@ protected:
         , m_kind(kind)
         , m_is_strict_mode(is_strict_mode)
         , m_might_need_arguments_object(might_need_arguments_object)
+        , m_might_have_direct_eval(might_have_direct_eval)
         , m_is_arrow_function(is_arrow_function)
     {
         if (m_is_arrow_function)
@@ -476,6 +478,7 @@ private:
     FunctionKind m_kind;
     bool m_is_strict_mode { false };
     bool m_might_need_arguments_object { false };
+    bool m_might_have_direct_eval { false };
     bool m_is_arrow_function { false };
 };
 
@@ -485,9 +488,9 @@ class FunctionDeclaration final
 public:
     static bool must_have_name() { return true; }
 
-    FunctionDeclaration(SourceRange source_range, FlyString const& name, NonnullRefPtr<Statement> body, Vector<Parameter> parameters, i32 function_length, FunctionKind kind, bool is_strict_mode, bool might_need_arguments_object)
+    FunctionDeclaration(SourceRange source_range, FlyString const& name, NonnullRefPtr<Statement> body, Vector<Parameter> parameters, i32 function_length, FunctionKind kind, bool is_strict_mode, bool might_need_arguments_object, bool might_have_direct_eval)
         : Declaration(source_range)
-        , FunctionNode(name, move(body), move(parameters), function_length, kind, is_strict_mode, might_need_arguments_object, false)
+        , FunctionNode(name, move(body), move(parameters), function_length, kind, is_strict_mode, might_need_arguments_object, might_have_direct_eval, false)
     {
     }
 
@@ -511,9 +514,9 @@ class FunctionExpression final
 public:
     static bool must_have_name() { return false; }
 
-    FunctionExpression(SourceRange source_range, FlyString const& name, NonnullRefPtr<Statement> body, Vector<Parameter> parameters, i32 function_length, FunctionKind kind, bool is_strict_mode, bool might_need_arguments_object, bool is_arrow_function = false)
+    FunctionExpression(SourceRange source_range, FlyString const& name, NonnullRefPtr<Statement> body, Vector<Parameter> parameters, i32 function_length, FunctionKind kind, bool is_strict_mode, bool might_need_arguments_object, bool might_have_direct_eval, bool is_arrow_function = false)
         : Expression(source_range)
-        , FunctionNode(name, move(body), move(parameters), function_length, kind, is_strict_mode, might_need_arguments_object, is_arrow_function)
+        , FunctionNode(name, move(body), move(parameters), function_length, kind, is_strict_mode, might_need_arguments_object, might_have_direct_eval, is_arrow_function)
     {
     }
 
diff --git a/Userland/Libraries/LibJS/Parser.cpp b/Userland/Libraries/LibJS/Parser.cpp
index 94f803d0f9..39c21d5bd5 100644
--- a/Userland/Libraries/LibJS/Parser.cpp
+++ b/Userland/Libraries/LibJS/Parser.cpp
@@ -658,7 +658,7 @@ RefPtr<FunctionExpression> Parser::try_parse_arrow_function_expression(bool expe
     return create_ast_node<FunctionExpression>(
         { m_state.current_token.filename(), rule_start.position(), position() }, "", move(body),
         move(parameters), function_length, FunctionKind::Regular, body->in_strict_mode(),
-        /* might_need_arguments_object */ false, /* is_arrow_function */ true);
+        /* might_need_arguments_object */ false, /* might_have_direct_eval */ false, /* is_arrow_function */ true);
 }
 
 RefPtr<Statement> Parser::try_parse_labelled_statement(AllowLabelledFunction allow_function)
@@ -977,12 +977,12 @@ NonnullRefPtr<ClassExpression> Parser::parse_class_expression(bool expect_class_
             constructor = create_ast_node<FunctionExpression>(
                 { m_state.current_token.filename(), rule_start.position(), position() }, class_name, move(constructor_body),
                 Vector { FunctionNode::Parameter { FlyString { "args" }, nullptr, true } }, 0, FunctionKind::Regular,
-                /* is_strict_mode */ true, /* might_need_arguments_object */ false);
+                /* is_strict_mode */ true, /* might_need_arguments_object */ false, /* might_have_direct_eval */ true);
         } else {
             constructor = create_ast_node<FunctionExpression>(
                 { m_state.current_token.filename(), rule_start.position(), position() }, class_name, move(constructor_body),
                 Vector<FunctionNode::Parameter> {}, 0, FunctionKind::Regular,
-                /* is_strict_mode */ true, /* might_need_arguments_object */ false);
+                /* is_strict_mode */ true, /* might_need_arguments_object */ false, /* might_have_direct_eval */ true);
         }
     }
 
@@ -1962,6 +1962,7 @@ NonnullRefPtr<FunctionNodeType> Parser::parse_function_node(u8 parse_options)
     TemporaryChange continue_context_rollback(m_state.in_continue_context, false);
     TemporaryChange class_field_initializer_rollback(m_state.in_class_field_initializer, false);
     TemporaryChange might_need_arguments_object_rollback(m_state.function_might_need_arguments_object, false);
+    TemporaryChange might_have_direct_eval_rollback(m_state.function_might_have_direct_eval, false);
 
     constexpr auto is_function_expression = IsSame<FunctionNodeType, FunctionExpression>;
     auto function_kind = (parse_options & FunctionNodeParseOptions::IsGeneratorFunction) != 0 ? FunctionKind::Generator : FunctionKind::Regular;
@@ -2010,7 +2011,8 @@ NonnullRefPtr<FunctionNodeType> Parser::parse_function_node(u8 parse_options)
     return create_ast_node<FunctionNodeType>(
         { m_state.current_token.filename(), rule_start.position(), position() },
         name, move(body), move(parameters), function_length,
-        function_kind, has_strict_directive, m_state.function_might_need_arguments_object);
+        function_kind, has_strict_directive, m_state.function_might_need_arguments_object,
+        m_state.function_might_have_direct_eval);
 }
 
 Vector<FunctionNode::Parameter> Parser::parse_formal_parameters(int& function_length, u8 parse_options)
@@ -3136,8 +3138,14 @@ Token Parser::consume()
     // NOTE: This is the bare minimum needed to decide whether we might need an arguments object
     // in a function expression or declaration. ("might" because the AST implements some further
     // conditions from the spec that rule out the need for allocating one)
-    if (old_token.type() == TokenType::Identifier && old_token.value().is_one_of("arguments"sv, "eval"sv))
-        m_state.function_might_need_arguments_object = true;
+    if (old_token.type() == TokenType::Identifier) {
+        bool is_arguments = old_token.value() == "arguments"sv;
+        bool is_eval = old_token.value() == "eval"sv;
+        if (is_arguments || is_eval)
+            m_state.function_might_need_arguments_object = true;
+        if (is_eval)
+            m_state.function_might_have_direct_eval = true;
+    }
     return old_token;
 }
 
diff --git a/Userland/Libraries/LibJS/Parser.h b/Userland/Libraries/LibJS/Parser.h
index 4613aaf8fd..3ef468db52 100644
--- a/Userland/Libraries/LibJS/Parser.h
+++ b/Userland/Libraries/LibJS/Parser.h
@@ -254,6 +254,7 @@ private:
         bool string_legacy_octal_escape_sequence_in_scope { false };
         bool in_class_field_initializer { false };
         bool function_might_need_arguments_object { false };
+        bool function_might_have_direct_eval { false };
 
         ParserState(Lexer, Program::Type);
     };
diff --git a/Userland/Libraries/LibJS/Runtime/ECMAScriptFunctionObject.cpp b/Userland/Libraries/LibJS/Runtime/ECMAScriptFunctionObject.cpp
index e998236294..c47e9191ac 100644
--- a/Userland/Libraries/LibJS/Runtime/ECMAScriptFunctionObject.cpp
+++ b/Userland/Libraries/LibJS/Runtime/ECMAScriptFunctionObject.cpp
@@ -24,7 +24,7 @@
 
 namespace JS {
 
-ECMAScriptFunctionObject* ECMAScriptFunctionObject::create(GlobalObject& global_object, FlyString name, Statement const& ecmascript_code, Vector<FunctionNode::Parameter> parameters, i32 m_function_length, Environment* parent_scope, FunctionKind kind, bool is_strict, bool might_need_arguments_object, bool is_arrow_function)
+ECMAScriptFunctionObject* ECMAScriptFunctionObject::create(GlobalObject& global_object, FlyString name, Statement const& ecmascript_code, Vector<FunctionNode::Parameter> parameters, i32 m_function_length, Environment* parent_scope, FunctionKind kind, bool is_strict, bool might_need_arguments_object, bool might_have_direct_eval, bool is_arrow_function)
 {
     Object* prototype = nullptr;
     switch (kind) {
@@ -35,10 +35,10 @@ ECMAScriptFunctionObject* ECMAScriptFunctionObject::create(GlobalObject& global_
         prototype = global_object.generator_function_prototype();
         break;
     }
-    return global_object.heap().allocate<ECMAScriptFunctionObject>(global_object, move(name), ecmascript_code, move(parameters), m_function_length, parent_scope, *prototype, kind, is_strict, might_need_arguments_object, is_arrow_function);
+    return global_object.heap().allocate<ECMAScriptFunctionObject>(global_object, move(name), ecmascript_code, move(parameters), m_function_length, parent_scope, *prototype, kind, is_strict, might_need_arguments_object, might_have_direct_eval, is_arrow_function);
 }
 
-ECMAScriptFunctionObject::ECMAScriptFunctionObject(FlyString name, Statement const& ecmascript_code, Vector<FunctionNode::Parameter> formal_parameters, i32 function_length, Environment* parent_scope, Object& prototype, FunctionKind kind, bool strict, bool might_need_arguments_object, bool is_arrow_function)
+ECMAScriptFunctionObject::ECMAScriptFunctionObject(FlyString name, Statement const& ecmascript_code, Vector<FunctionNode::Parameter> formal_parameters, i32 function_length, Environment* parent_scope, Object& prototype, FunctionKind kind, bool strict, bool might_need_arguments_object, bool might_have_direct_eval, bool is_arrow_function)
     : FunctionObject(prototype)
     , m_environment(parent_scope)
     , m_formal_parameters(move(formal_parameters))
@@ -49,6 +49,7 @@ ECMAScriptFunctionObject::ECMAScriptFunctionObject(FlyString name, Statement con
     , m_function_length(function_length)
     , m_kind(kind)
     , m_might_need_arguments_object(might_need_arguments_object)
+    , m_might_have_direct_eval(might_have_direct_eval)
     , m_is_arrow_function(is_arrow_function)
 {
     // NOTE: This logic is from OrdinaryFunctionCreate, https://tc39.es/ecma262/#sec-ordinaryfunctioncreate
@@ -344,7 +345,9 @@ ThrowCompletionOr<void> ECMAScriptFunctionObject::function_declaration_instantia
 
     Environment* lex_environment;
 
-    if (!is_strict_mode())
+    // Optimization: We avoid creating empty declarative environments in non-strict mode, if we believe there is no
+    //               direct eval() within this function that could screw things up.
+    if (!is_strict_mode() && (m_might_have_direct_eval || (scope_body && scope_body->has_lexical_declarations())))
         lex_environment = new_declarative_environment(*var_environment);
     else
         lex_environment = var_environment;
@@ -367,7 +370,7 @@ ThrowCompletionOr<void> ECMAScriptFunctionObject::function_declaration_instantia
     VERIFY(!vm.exception());
 
     for (auto& declaration : functions_to_initialize) {
-        auto* function = ECMAScriptFunctionObject::create(global_object(), declaration.name(), declaration.body(), declaration.parameters(), declaration.function_length(), lex_environment, declaration.kind(), declaration.is_strict_mode(), declaration.might_need_arguments_object());
+        auto* function = ECMAScriptFunctionObject::create(global_object(), declaration.name(), declaration.body(), declaration.parameters(), declaration.function_length(), lex_environment, declaration.kind(), declaration.is_strict_mode(), declaration.might_need_arguments_object(), declaration.might_have_direct_eval());
         var_environment->set_mutable_binding(global_object(), declaration.name(), function, false);
     }
 
diff --git a/Userland/Libraries/LibJS/Runtime/ECMAScriptFunctionObject.h b/Userland/Libraries/LibJS/Runtime/ECMAScriptFunctionObject.h
index b936997988..f4425c958f 100644
--- a/Userland/Libraries/LibJS/Runtime/ECMAScriptFunctionObject.h
+++ b/Userland/Libraries/LibJS/Runtime/ECMAScriptFunctionObject.h
@@ -28,9 +28,9 @@ public:
         Global,
     };
 
-    static ECMAScriptFunctionObject* create(GlobalObject&, FlyString name, Statement const& ecmascript_code, Vector<FunctionNode::Parameter> parameters, i32 m_function_length, Environment* parent_scope, FunctionKind, bool is_strict, bool might_need_arguments_object = true, bool is_arrow_function = false);
+    static ECMAScriptFunctionObject* create(GlobalObject&, FlyString name, Statement const& ecmascript_code, Vector<FunctionNode::Parameter> parameters, i32 m_function_length, Environment* parent_scope, FunctionKind, bool is_strict, bool might_need_arguments_object = true, bool might_have_direct_eval = true, bool is_arrow_function = false);
 
-    ECMAScriptFunctionObject(FlyString name, Statement const& ecmascript_code, Vector<FunctionNode::Parameter> parameters, i32 m_function_length, Environment* parent_scope, Object& prototype, FunctionKind, bool is_strict, bool might_need_arguments_object, bool is_arrow_function);
+    ECMAScriptFunctionObject(FlyString name, Statement const& ecmascript_code, Vector<FunctionNode::Parameter> parameters, i32 m_function_length, Environment* parent_scope, Object& prototype, FunctionKind, bool is_strict, bool might_need_arguments_object, bool might_have_direct_eval, bool is_arrow_function);
     virtual void initialize(GlobalObject&) override;
     virtual ~ECMAScriptFunctionObject();
 
@@ -101,6 +101,7 @@ private:
     i32 m_function_length { 0 };
     FunctionKind m_kind { FunctionKind::Regular };
     bool m_might_need_arguments_object { true };
+    bool m_might_have_direct_eval { true };
     bool m_is_arrow_function { false };
     bool m_has_simple_parameter_list { false };
 };