use with_capacity to reduce re-allocations fixes #3896 (#3961)

* use with_capacity to reduce allocations

* Update to use const generics over runtime param

* add comment above with_capacity

* - move OWN_PROPS
- add profiling marks in more places

* use const in trait instead

Author: jasonwilliams

core/engine/src/builtins/array/mod.rs

@@ -190,6 +190,9 @@ impl BuiltInObject for Array {
 }
 
 impl BuiltInConstructor for Array {
+    const P: usize = 41;
+    const SP: usize = 5;
+
     const LENGTH: usize = 1;
 
     const STANDARD_CONSTRUCTOR: fn(&StandardConstructors) -> &StandardConstructor =

core/engine/src/builtins/array_buffer/mod.rs

@@ -374,6 +374,8 @@ impl BuiltInObject for ArrayBuffer {
 }
 
 impl BuiltInConstructor for ArrayBuffer {
+    const P: usize = 9;
+    const SP: usize = 2;
     const LENGTH: usize = 1;
 
     const STANDARD_CONSTRUCTOR: fn(&StandardConstructors) -> &StandardConstructor =

core/engine/src/builtins/array_buffer/shared.rs

@@ -155,6 +155,8 @@ impl BuiltInObject for SharedArrayBuffer {
 
 impl BuiltInConstructor for SharedArrayBuffer {
     const LENGTH: usize = 1;
+    const P: usize = 6;
+    const SP: usize = 1;
 
     const STANDARD_CONSTRUCTOR: fn(&StandardConstructors) -> &StandardConstructor =
         StandardConstructors::shared_array_buffer;

core/engine/src/builtins/async_function/mod.rs

@@ -52,6 +52,8 @@ impl BuiltInObject for AsyncFunction {
 
 impl BuiltInConstructor for AsyncFunction {
     const LENGTH: usize = 1;
+    const P: usize = 1;
+    const SP: usize = 0;
 
     const STANDARD_CONSTRUCTOR: fn(&StandardConstructors) -> &StandardConstructor =
         StandardConstructors::async_function;

core/engine/src/builtins/async_generator_function/mod.rs

@@ -57,6 +57,8 @@ impl BuiltInObject for AsyncGeneratorFunction {
 
 impl BuiltInConstructor for AsyncGeneratorFunction {
     const LENGTH: usize = 1;
+    const P: usize = 2;
+    const SP: usize = 0;
 
     const STANDARD_CONSTRUCTOR: fn(&StandardConstructors) -> &StandardConstructor =
         StandardConstructors::async_generator_function;

core/engine/src/builtins/bigint/mod.rs

@@ -65,6 +65,8 @@ impl BuiltInObject for BigInt {
 
 impl BuiltInConstructor for BigInt {
     const LENGTH: usize = 1;
+    const P: usize = 3;
+    const SP: usize = 2;
 
     const STANDARD_CONSTRUCTOR: fn(&StandardConstructors) -> &StandardConstructor =
         StandardConstructors::bigint;

core/engine/src/builtins/boolean/mod.rs

@@ -51,6 +51,8 @@ impl BuiltInObject for Boolean {
 
 impl BuiltInConstructor for Boolean {
     const LENGTH: usize = 1;
+    const P: usize = 2;
+    const SP: usize = 0;
 
     const STANDARD_CONSTRUCTOR: fn(&StandardConstructors) -> &StandardConstructor =
         StandardConstructors::boolean;

core/engine/src/builtins/builder.rs

@@ -135,6 +135,9 @@ impl ApplyToObject for OrdinaryObject {
     fn apply_to(self, _: &JsObject) {}
 }
 
+// The number of properties that are always present in a standard constructor. See build method
+const OWN_PROPS: usize = 3;
+
 /// Builder for creating built-in objects, like `Array`.
 ///
 /// The marker `ObjectType` restricts the methods that can be called depending on the
@@ -528,6 +531,7 @@ impl<'ctx> BuiltInBuilder<'ctx, OrdinaryObject> {
 }
 
 impl<'ctx> BuiltInBuilder<'ctx, Callable<Constructor>> {
+    /// Create a new builder for a constructor function setting the properties ahead of time for optimizations (less reallocations)
     pub(crate) fn from_standard_constructor<SC: BuiltInConstructor>(
         realm: &'ctx Realm,
     ) -> BuiltInConstructorWithPrototype<'ctx> {
@@ -537,11 +541,11 @@ impl<'ctx> BuiltInBuilder<'ctx, Callable<Constructor>> {
             function: SC::constructor,
             name: js_string!(SC::NAME),
             length: SC::LENGTH,
-            object_property_table: PropertyTableInner::default(),
-            object_storage: Vec::default(),
+            object_property_table: PropertyTableInner::with_capacity(SC::SP + OWN_PROPS),
+            object_storage: Vec::with_capacity(SC::SP + OWN_PROPS),
             object: constructor.constructor(),
-            prototype_property_table: PropertyTableInner::default(),
-            prototype_storage: Vec::default(),
+            prototype_property_table: PropertyTableInner::with_capacity(SC::P),
+            prototype_storage: Vec::with_capacity(SC::P),
             prototype: constructor.prototype(),
             __proto__: Some(realm.intrinsics().constructors().function().prototype()),
             inherits: Some(realm.intrinsics().constructors().object().prototype()),

core/engine/src/builtins/dataview/mod.rs

@@ -167,6 +167,8 @@ impl BuiltInObject for DataView {
 
 impl BuiltInConstructor for DataView {
     const LENGTH: usize = 1;
+    const P: usize = 24;
+    const SP: usize = 0;
 
     const STANDARD_CONSTRUCTOR: fn(&StandardConstructors) -> &StandardConstructor =
         StandardConstructors::data_view;

core/engine/src/builtins/date/mod.rs

@@ -185,6 +185,8 @@ impl BuiltInObject for Date {
 
 impl BuiltInConstructor for Date {
     const LENGTH: usize = 7;
+    const P: usize = 47;
+    const SP: usize = 3;
 
     const STANDARD_CONSTRUCTOR: fn(&StandardConstructors) -> &StandardConstructor =
         StandardConstructors::date;