From 269f9c68638d9ccd3c5dc41575ba093290c989ac Mon Sep 17 00:00:00 2001
From: Andreas Kling <kling@serenityos.org>
Date: Sun, 27 Mar 2022 03:19:32 +0200
Subject: [PATCH] LibWeb: Add fast-paths for wrapping already-wrapped C++
 objects

If a C++ object already has a JS wrapper, we don't need to go through
the expensive type checks to figure out which kind of wrapper to create.
Instead, just return the wrapper we already have!

This gives a noticeable increase in smoothness on Acid3, where ~10% of
CPU time was previously spent doing RTTI type checks in wrap(). With
these changes, it's down to ~1%.
---
 Userland/Libraries/LibWeb/Bindings/CSSRuleWrapperFactory.cpp | 3 +++
 Userland/Libraries/LibWeb/Bindings/EventWrapperFactory.cpp   | 3 +++
 Userland/Libraries/LibWeb/Bindings/NodeWrapperFactory.cpp    | 3 +++
 3 files changed, 9 insertions(+)

diff --git a/Userland/Libraries/LibWeb/Bindings/CSSRuleWrapperFactory.cpp b/Userland/Libraries/LibWeb/Bindings/CSSRuleWrapperFactory.cpp
index 54cdc9643e..e20db17db7 100644
--- a/Userland/Libraries/LibWeb/Bindings/CSSRuleWrapperFactory.cpp
+++ b/Userland/Libraries/LibWeb/Bindings/CSSRuleWrapperFactory.cpp
@@ -14,6 +14,9 @@ namespace Web::Bindings {
 
 CSSRuleWrapper* wrap(JS::GlobalObject& global_object, CSS::CSSRule& rule)
 {
+    if (rule.wrapper())
+        return static_cast<CSSRuleWrapper*>(rule.wrapper());
+
     if (is<CSS::CSSStyleRule>(rule))
         return static_cast<CSSRuleWrapper*>(wrap_impl(global_object, verify_cast<CSS::CSSStyleRule>(rule)));
     return static_cast<CSSRuleWrapper*>(wrap_impl(global_object, rule));
diff --git a/Userland/Libraries/LibWeb/Bindings/EventWrapperFactory.cpp b/Userland/Libraries/LibWeb/Bindings/EventWrapperFactory.cpp
index a048827b68..e5d974cef4 100644
--- a/Userland/Libraries/LibWeb/Bindings/EventWrapperFactory.cpp
+++ b/Userland/Libraries/LibWeb/Bindings/EventWrapperFactory.cpp
@@ -22,6 +22,9 @@ namespace Web::Bindings {
 
 EventWrapper* wrap(JS::GlobalObject& global_object, DOM::Event& event)
 {
+    if (event.wrapper())
+        return static_cast<EventWrapper*>(event.wrapper());
+
     if (is<DOM::CustomEvent>(event))
         return static_cast<CustomEventWrapper*>(wrap_impl(global_object, static_cast<DOM::CustomEvent&>(event)));
     if (is<CSS::MediaQueryListEvent>(event))
diff --git a/Userland/Libraries/LibWeb/Bindings/NodeWrapperFactory.cpp b/Userland/Libraries/LibWeb/Bindings/NodeWrapperFactory.cpp
index db09082939..2040879901 100644
--- a/Userland/Libraries/LibWeb/Bindings/NodeWrapperFactory.cpp
+++ b/Userland/Libraries/LibWeb/Bindings/NodeWrapperFactory.cpp
@@ -176,6 +176,9 @@ namespace Web::Bindings {
 
 NodeWrapper* wrap(JS::GlobalObject& global_object, DOM::Node& node)
 {
+    if (node.wrapper())
+        return static_cast<NodeWrapper*>(node.wrapper());
+
     if (is<DOM::Document>(node))
         return static_cast<NodeWrapper*>(wrap_impl(global_object, verify_cast<DOM::Document>(node)));
     if (is<DOM::DocumentType>(node))