From 22c803d8e50616170e336a5902cf3d8aeaf2a115 Mon Sep 17 00:00:00 2001
From: Andreas Kling <kling@serenityos.org>
Date: Thu, 10 Jun 2021 01:07:53 +0200
Subject: [PATCH] LibJS: Always keep the global object in bytecode VM register
 $1

---
 Userland/Libraries/LibJS/Bytecode/Generator.h     | 2 +-
 Userland/Libraries/LibJS/Bytecode/Interpreter.cpp | 1 +
 Userland/Libraries/LibJS/Bytecode/Register.h      | 7 +++++++
 3 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/Userland/Libraries/LibJS/Bytecode/Generator.h b/Userland/Libraries/LibJS/Bytecode/Generator.h
index f3d8fabf6e..7410ff1918 100644
--- a/Userland/Libraries/LibJS/Bytecode/Generator.h
+++ b/Userland/Libraries/LibJS/Bytecode/Generator.h
@@ -99,7 +99,7 @@ private:
     NonnullOwnPtrVector<BasicBlock> m_root_basic_blocks;
     NonnullOwnPtr<StringTable> m_string_table;
 
-    u32 m_next_register { 1 };
+    u32 m_next_register { 2 };
     u32 m_next_block { 1 };
     Vector<Label> m_continuable_scopes;
     Vector<Label> m_breakable_scopes;
diff --git a/Userland/Libraries/LibJS/Bytecode/Interpreter.cpp b/Userland/Libraries/LibJS/Bytecode/Interpreter.cpp
index 0d36b5ac46..fb2a493d83 100644
--- a/Userland/Libraries/LibJS/Bytecode/Interpreter.cpp
+++ b/Userland/Libraries/LibJS/Bytecode/Interpreter.cpp
@@ -59,6 +59,7 @@ Value Interpreter::run(Executable const& executable)
     auto block = &executable.basic_blocks.first();
     m_register_windows.append(make<RegisterWindow>());
     registers().resize(executable.number_of_registers);
+    registers()[Register::global_object_index] = Value(&global_object());
 
     for (;;) {
         Bytecode::InstructionStreamIterator pc(block->instruction_stream());
diff --git a/Userland/Libraries/LibJS/Bytecode/Register.h b/Userland/Libraries/LibJS/Bytecode/Register.h
index ce2895b513..1de1826c3a 100644
--- a/Userland/Libraries/LibJS/Bytecode/Register.h
+++ b/Userland/Libraries/LibJS/Bytecode/Register.h
@@ -13,6 +13,7 @@ namespace JS::Bytecode {
 class Register {
 public:
     constexpr static u32 accumulator_index = 0;
+    constexpr static u32 global_object_index = 1;
 
     static Register accumulator()
     {
@@ -20,6 +21,12 @@ public:
         return accumulator;
     }
 
+    static Register global_object()
+    {
+        static Register global_object(global_object_index);
+        return global_object;
+    }
+
     explicit Register(u32 index)
         : m_index(index)
     {