LibJS: Use premade shape when creating mapped arguments objects

Knocks out a 0.4% profile item on Speedometer 3.

Libraries/LibJS/Runtime/AbstractOperations.cpp

@@ -1101,13 +1101,13 @@ Object* create_mapped_arguments_object(VM& vm, FunctionObject& function, Nonnull
         auto value = arguments[index];
 
         // b. Perform ! CreateDataPropertyOrThrow(obj, ! ToString(𝔽(index)), val).
-        MUST(object->create_data_property_or_throw(index, value));
+        object->indexed_properties().put(index, value);
 
         // c. Set index to index + 1.
     }
 
     // 16. Perform ! DefinePropertyOrThrow(obj, "length", PropertyDescriptor { [[Value]]: 𝔽(len), [[Writable]]: true, [[Enumerable]]: false, [[Configurable]]: true }).
-    MUST(object->define_property_or_throw(vm.names.length, { .value = Value(length), .writable = true, .enumerable = false, .configurable = true }));
+    object->put_direct(realm.intrinsics().mapped_arguments_object_length_offset(), Value(length));
 
     // 17. Let mappedNames be a new empty List.
     HashTable<FlyString> mapped_names;
@@ -1147,10 +1147,10 @@ Object* create_mapped_arguments_object(VM& vm, FunctionObject& function, Nonnull
 
     // 20. Perform ! DefinePropertyOrThrow(obj, @@iterator, PropertyDescriptor { [[Value]]: %Array.prototype.values%, [[Writable]]: true, [[Enumerable]]: false, [[Configurable]]: true }).
     auto array_prototype_values = realm.intrinsics().array_prototype_values_function();
-    MUST(object->define_property_or_throw(vm.well_known_symbol_iterator(), { .value = array_prototype_values, .writable = true, .enumerable = false, .configurable = true }));
+    object->put_direct(realm.intrinsics().mapped_arguments_object_well_known_symbol_iterator_offset(), array_prototype_values);
 
     // 21. Perform ! DefinePropertyOrThrow(obj, "callee", PropertyDescriptor { [[Value]]: func, [[Writable]]: true, [[Enumerable]]: false, [[Configurable]]: true }).
-    MUST(object->define_property_or_throw(vm.names.callee, { .value = &function, .writable = true, .enumerable = false, .configurable = true }));
+    object->put_direct(realm.intrinsics().mapped_arguments_object_callee_offset(), Value(&function));
 
     // 22. Return obj.
     return object;

Libraries/LibJS/Runtime/ArgumentsObject.cpp

@@ -13,7 +13,7 @@ namespace JS {
 GC_DEFINE_ALLOCATOR(ArgumentsObject);
 
 ArgumentsObject::ArgumentsObject(Realm& realm, Environment& environment)
-    : Object(ConstructWithPrototypeTag::Tag, realm.intrinsics().object_prototype(), MayInterfereWithIndexedPropertyAccess::Yes)
+    : Object(realm.intrinsics().mapped_arguments_object_shape(), MayInterfereWithIndexedPropertyAccess::Yes)
     , m_environment(environment)
 {
 }

Libraries/LibJS/Runtime/Intrinsics.cpp

@@ -229,6 +229,15 @@ void Intrinsics::initialize_intrinsics(Realm& realm)
     m_unmapped_arguments_object_well_known_symbol_iterator_offset = m_unmapped_arguments_object_shape->lookup(StringOrSymbol(vm.well_known_symbol_iterator())).value().offset;
     m_unmapped_arguments_object_callee_offset = m_unmapped_arguments_object_shape->lookup(vm.names.callee.to_string_or_symbol()).value().offset;
 
+    m_mapped_arguments_object_shape = heap().allocate<Shape>(realm);
+    m_mapped_arguments_object_shape->set_prototype_without_transition(m_object_prototype);
+    m_mapped_arguments_object_shape->add_property_without_transition(vm.names.length, Attribute::Writable | Attribute::Configurable);
+    m_mapped_arguments_object_shape->add_property_without_transition(vm.well_known_symbol_iterator(), Attribute::Writable | Attribute::Configurable);
+    m_mapped_arguments_object_shape->add_property_without_transition(vm.names.callee, Attribute::Writable | Attribute::Configurable);
+    m_mapped_arguments_object_length_offset = m_mapped_arguments_object_shape->lookup(vm.names.length.to_string_or_symbol()).value().offset;
+    m_mapped_arguments_object_well_known_symbol_iterator_offset = m_mapped_arguments_object_shape->lookup(StringOrSymbol(vm.well_known_symbol_iterator())).value().offset;
+    m_mapped_arguments_object_callee_offset = m_mapped_arguments_object_shape->lookup(vm.names.callee.to_string_or_symbol()).value().offset;
+
     // Normally Realm::create() takes care of this, but these are allocated via Heap::allocate().
     m_function_prototype->initialize(realm);
     m_object_prototype->initialize(realm);
@@ -406,6 +415,7 @@ void Intrinsics::visit_edges(Visitor& visitor)
     visitor.visit(m_normal_function_shape);
     visitor.visit(m_native_function_shape);
     visitor.visit(m_unmapped_arguments_object_shape);
+    visitor.visit(m_mapped_arguments_object_shape);
     visitor.visit(m_proxy_constructor);
     visitor.visit(m_async_from_sync_iterator_prototype);
     visitor.visit(m_async_generator_prototype);

Libraries/LibJS/Runtime/Intrinsics.h

@@ -45,6 +45,11 @@ public:
     [[nodiscard]] u32 unmapped_arguments_object_well_known_symbol_iterator_offset() const { return m_unmapped_arguments_object_well_known_symbol_iterator_offset; }
     [[nodiscard]] u32 unmapped_arguments_object_callee_offset() const { return m_unmapped_arguments_object_callee_offset; }
 
+    [[nodiscard]] GC::Ref<Shape> mapped_arguments_object_shape() { return *m_mapped_arguments_object_shape; }
+    [[nodiscard]] u32 mapped_arguments_object_length_offset() const { return m_mapped_arguments_object_length_offset; }
+    [[nodiscard]] u32 mapped_arguments_object_well_known_symbol_iterator_offset() const { return m_mapped_arguments_object_well_known_symbol_iterator_offset; }
+    [[nodiscard]] u32 mapped_arguments_object_callee_offset() const { return m_mapped_arguments_object_callee_offset; }
+
     [[nodiscard]] GC::Ref<Accessor> throw_type_error_accessor() { return *m_throw_type_error_accessor; }
 
     // Not included in JS_ENUMERATE_NATIVE_OBJECTS due to missing distinct prototype
@@ -169,6 +174,11 @@ private:
     u32 m_unmapped_arguments_object_well_known_symbol_iterator_offset { 0 };
     u32 m_unmapped_arguments_object_callee_offset { 0 };
 
+    GC::Ptr<Shape> m_mapped_arguments_object_shape;
+    u32 m_mapped_arguments_object_length_offset { 0 };
+    u32 m_mapped_arguments_object_well_known_symbol_iterator_offset { 0 };
+    u32 m_mapped_arguments_object_callee_offset { 0 };
+
     GC::Ptr<Accessor> m_throw_type_error_accessor;
 
     // Not included in JS_ENUMERATE_NATIVE_OBJECTS due to missing distinct prototype