From 0a911178cea4fcfb462eb7e256c51ed75756c7c8 Mon Sep 17 00:00:00 2001
From: Andreas Kling <kling@serenityos.org>
Date: Fri, 19 Mar 2021 11:28:44 +0100
Subject: [PATCH] LibJS: Add fast_is<T> for StringObject and GlobalObject

Both of these are quite hot in profiles.
---
 Userland/Libraries/LibJS/Runtime/GlobalObject.h | 5 +++++
 Userland/Libraries/LibJS/Runtime/Object.h       | 5 +++++
 Userland/Libraries/LibJS/Runtime/StringObject.h | 4 ++++
 3 files changed, 14 insertions(+)

diff --git a/Userland/Libraries/LibJS/Runtime/GlobalObject.h b/Userland/Libraries/LibJS/Runtime/GlobalObject.h
index 6261a23077..1062a3f75d 100644
--- a/Userland/Libraries/LibJS/Runtime/GlobalObject.h
+++ b/Userland/Libraries/LibJS/Runtime/GlobalObject.h
@@ -76,6 +76,8 @@ protected:
     void add_constructor(const FlyString& property_name, ConstructorType*&, Object* prototype);
 
 private:
+    virtual bool is_global_object() const final { return true; }
+
     JS_DECLARE_NATIVE_FUNCTION(gc);
     JS_DECLARE_NATIVE_FUNCTION(is_nan);
     JS_DECLARE_NATIVE_FUNCTION(is_finite);
@@ -131,4 +133,7 @@ inline GlobalObject* Shape::global_object() const
     return static_cast<GlobalObject*>(m_global_object);
 }
 
+template<>
+inline bool Object::fast_is<GlobalObject>() const { return is_global_object(); }
+
 }
diff --git a/Userland/Libraries/LibJS/Runtime/Object.h b/Userland/Libraries/LibJS/Runtime/Object.h
index 0e496fefb3..d80d67642d 100644
--- a/Userland/Libraries/LibJS/Runtime/Object.h
+++ b/Userland/Libraries/LibJS/Runtime/Object.h
@@ -112,6 +112,8 @@ public:
     virtual bool is_array() const { return false; }
     virtual bool is_function() const { return false; }
     virtual bool is_typed_array() const { return false; }
+    virtual bool is_string_object() const { return false; }
+    virtual bool is_global_object() const { return false; }
 
     virtual const char* class_name() const override { return "Object"; }
     virtual void visit_edges(Cell::Visitor&) override;
@@ -152,6 +154,9 @@ public:
     void enable_transitions() { m_transitions_enabled = true; }
     void disable_transitions() { m_transitions_enabled = false; }
 
+    template<typename T>
+    bool fast_is() const = delete;
+
 protected:
     enum class GlobalObjectTag { Tag };
     enum class ConstructWithoutPrototypeTag { Tag };
diff --git a/Userland/Libraries/LibJS/Runtime/StringObject.h b/Userland/Libraries/LibJS/Runtime/StringObject.h
index 7fb32ebc63..7ba1b1ae4c 100644
--- a/Userland/Libraries/LibJS/Runtime/StringObject.h
+++ b/Userland/Libraries/LibJS/Runtime/StringObject.h
@@ -46,9 +46,13 @@ public:
     }
 
 private:
+    virtual bool is_string_object() const final { return true; }
     virtual void visit_edges(Visitor&) override;
 
     PrimitiveString& m_string;
 };
 
+template<>
+inline bool Object::fast_is<StringObject>() const { return is_string_object(); }
+
 }