From dc884aa0d3f73f800fe64a9130bf3168325fff84 Mon Sep 17 00:00:00 2001
From: Andreas Kling <kling@serenityos.org>
Date: Sun, 2 Jul 2023 15:05:17 +0200
Subject: [PATCH] LibJS/Bytecode: Remove unnecessary variable environment stack

The var environments will unwind as needed with the ExecutionContext
and there's no need to include it in the unwind info.

We still need to do this for lexical environments though, since they
can have short local lifetimes inside a function.
---
 Userland/Libraries/LibJS/Bytecode/BasicBlock.h    | 1 -
 Userland/Libraries/LibJS/Bytecode/Interpreter.cpp | 6 ++----
 Userland/Libraries/LibJS/Bytecode/Interpreter.h   | 5 -----
 3 files changed, 2 insertions(+), 10 deletions(-)

diff --git a/Userland/Libraries/LibJS/Bytecode/BasicBlock.h b/Userland/Libraries/LibJS/Bytecode/BasicBlock.h
index 653989de31..dde4c1bed1 100644
--- a/Userland/Libraries/LibJS/Bytecode/BasicBlock.h
+++ b/Userland/Libraries/LibJS/Bytecode/BasicBlock.h
@@ -19,7 +19,6 @@ struct UnwindInfo {
     BasicBlock const* finalizer;
 
     JS::GCPtr<Environment> lexical_environment;
-    JS::GCPtr<Environment> variable_environment;
 };
 
 class BasicBlock {
diff --git a/Userland/Libraries/LibJS/Bytecode/Interpreter.cpp b/Userland/Libraries/LibJS/Bytecode/Interpreter.cpp
index 317ebe5bd1..bb9d8bb884 100644
--- a/Userland/Libraries/LibJS/Bytecode/Interpreter.cpp
+++ b/Userland/Libraries/LibJS/Bytecode/Interpreter.cpp
@@ -221,7 +221,7 @@ Interpreter::ValueAndFrame Interpreter::run_and_return_frame(Realm& realm, Execu
     if (in_frame)
         push_register_window(in_frame, executable.number_of_registers);
     else
-        push_register_window(make<RegisterWindow>(MarkedVector<Value>(vm().heap()), MarkedVector<GCPtr<Environment>>(vm().heap()), MarkedVector<GCPtr<Environment>>(vm().heap()), Vector<UnwindInfo> {}), executable.number_of_registers);
+        push_register_window(make<RegisterWindow>(), executable.number_of_registers);
 
     for (;;) {
         Bytecode::InstructionStreamIterator pc(m_current_block->instruction_stream());
@@ -244,7 +244,6 @@ Interpreter::ValueAndFrame Interpreter::run_and_return_frame(Realm& realm, Execu
                     break;
                 if (unwind_context.handler) {
                     vm().running_execution_context().lexical_environment = unwind_context.lexical_environment;
-                    vm().running_execution_context().variable_environment = unwind_context.variable_environment;
                     m_current_block = unwind_context.handler;
                     unwind_context.handler = nullptr;
 
@@ -361,8 +360,7 @@ void Interpreter::enter_unwind_context(Optional<Label> handler_target, Optional<
         m_current_executable,
         handler_target.has_value() ? &handler_target->block() : nullptr,
         finalizer_target.has_value() ? &finalizer_target->block() : nullptr,
-        vm().running_execution_context().lexical_environment,
-        vm().running_execution_context().variable_environment);
+        vm().running_execution_context().lexical_environment);
 }
 
 void Interpreter::leave_unwind_context()
diff --git a/Userland/Libraries/LibJS/Bytecode/Interpreter.h b/Userland/Libraries/LibJS/Bytecode/Interpreter.h
index 515c50089e..50e8913d37 100644
--- a/Userland/Libraries/LibJS/Bytecode/Interpreter.h
+++ b/Userland/Libraries/LibJS/Bytecode/Interpreter.h
@@ -26,16 +26,12 @@ struct RegisterWindow {
             visitor.visit(value);
         for (auto const& environment : saved_lexical_environments)
             visitor.visit(environment);
-        for (auto const& environment : saved_variable_environments)
-            visitor.visit(environment);
         for (auto& context : unwind_contexts) {
             visitor.visit(context.lexical_environment);
-            visitor.visit(context.variable_environment);
         }
     }
     Vector<Value> registers;
     Vector<GCPtr<Environment>> saved_lexical_environments;
-    Vector<GCPtr<Environment>> saved_variable_environments;
     Vector<UnwindInfo> unwind_contexts;
 };
 
@@ -70,7 +66,6 @@ public:
     Value& reg(Register const& r) { return registers()[r.index()]; }
 
     auto& saved_lexical_environment_stack() { return window().saved_lexical_environments; }
-    auto& saved_variable_environment_stack() { return window().saved_variable_environments; }
     auto& unwind_contexts() { return window().unwind_contexts; }
 
     void jump(Label const& label)