From 8bdf6441b182674c0803750313888daf17f0220c Mon Sep 17 00:00:00 2001
From: Andreas Kling <kling@serenityos.org>
Date: Mon, 31 Jan 2022 15:55:54 +0100
Subject: [PATCH] LibJS: Use u32 for the JS::Shape property count

We don't need to support more than 2^32 object properties anyway, so
there's no point in using 64-bit property counts.

This small reduction in memory usage makes test-js run ~10% faster on
x86_64 locally.
---
 Userland/Libraries/LibJS/Runtime/Shape.cpp | 13 ++++++-------
 Userland/Libraries/LibJS/Runtime/Shape.h   |  6 +++---
 2 files changed, 9 insertions(+), 10 deletions(-)

diff --git a/Userland/Libraries/LibJS/Runtime/Shape.cpp b/Userland/Libraries/LibJS/Runtime/Shape.cpp
index e07cfd01fa9..0b0f2f96b7b 100644
--- a/Userland/Libraries/LibJS/Runtime/Shape.cpp
+++ b/Userland/Libraries/LibJS/Runtime/Shape.cpp
@@ -150,11 +150,6 @@ FLATTEN HashMap<StringOrSymbol, PropertyMetadata> const& Shape::property_table()
     return *m_property_table;
 }
 
-size_t Shape::property_count() const
-{
-    return m_property_count;
-}
-
 Vector<Shape::Property> Shape::property_table_ordered() const
 {
     auto vec = Vector<Shape::Property>();
@@ -207,7 +202,9 @@ void Shape::add_property_to_unique_shape(const StringOrSymbol& property_name, Pr
     VERIFY(is_unique());
     VERIFY(m_property_table);
     VERIFY(!m_property_table->contains(property_name));
-    m_property_table->set(property_name, { m_property_table->size(), attributes });
+    m_property_table->set(property_name, { static_cast<u32>(m_property_table->size()), attributes });
+
+    VERIFY(m_property_count < NumericLimits<u32>::max());
     ++m_property_count;
 }
 
@@ -238,8 +235,10 @@ void Shape::add_property_without_transition(StringOrSymbol const& property_name,
 {
     VERIFY(property_name.is_valid());
     ensure_property_table();
-    if (m_property_table->set(property_name, { m_property_count, attributes }) == AK::HashSetResult::InsertedNewEntry)
+    if (m_property_table->set(property_name, { m_property_count, attributes }) == AK::HashSetResult::InsertedNewEntry) {
+        VERIFY(m_property_count < NumericLimits<u32>::max());
         ++m_property_count;
+    }
 }
 
 FLATTEN void Shape::add_property_without_transition(PropertyKey const& property_name, PropertyAttributes attributes)
diff --git a/Userland/Libraries/LibJS/Runtime/Shape.h b/Userland/Libraries/LibJS/Runtime/Shape.h
index 55247bed2d3..b2712880c56 100644
--- a/Userland/Libraries/LibJS/Runtime/Shape.h
+++ b/Userland/Libraries/LibJS/Runtime/Shape.h
@@ -19,7 +19,7 @@
 namespace JS {
 
 struct PropertyMetadata {
-    size_t offset { 0 };
+    u32 offset { 0 };
     PropertyAttributes attributes { 0 };
 };
 
@@ -70,7 +70,7 @@ public:
 
     Optional<PropertyMetadata> lookup(const StringOrSymbol&) const;
     const HashMap<StringOrSymbol, PropertyMetadata>& property_table() const;
-    size_t property_count() const;
+    u32 property_count() const { return m_property_count; }
 
     struct Property {
         StringOrSymbol key;
@@ -107,7 +107,7 @@ private:
     Shape* m_previous { nullptr };
     StringOrSymbol m_property_name;
     Object* m_prototype { nullptr };
-    size_t m_property_count { 0 };
+    u32 m_property_count { 0 };
 
     PropertyAttributes m_attributes { 0 };
     TransitionType m_transition_type : 6 { TransitionType::Invalid };