From ed60d6371354e848c8ce9ef7e1c38fa5c8040ae2 Mon Sep 17 00:00:00 2001
From: Haled Odat <8566042+HalidOdat@users.noreply.github.com>
Date: Tue, 1 Aug 2023 10:17:04 +0200
Subject: [PATCH] Implement optimization identifier

---
 boa_ast/src/operations.rs               | 60 +++++++++++++++++++++++++
 boa_engine/src/bytecompiler/function.rs | 18 +++++++-
 2 files changed, 77 insertions(+), 1 deletion(-)

diff --git a/boa_ast/src/operations.rs b/boa_ast/src/operations.rs
index 09d7634d06b..09dab5a6745 100644
--- a/boa_ast/src/operations.rs
+++ b/boa_ast/src/operations.rs
@@ -2156,3 +2156,63 @@ impl<'ast> Visitor<'ast> for ReturnsValueVisitor {
         ControlFlow::Continue(())
     }
 }
+
+/// Returns `true` if the given statement can optimize local variables.
+#[must_use]
+pub fn can_optimize_local_variables<'a, N>(node: &'a N) -> bool
+where
+    &'a N: Into<NodeRef<'a>>,
+{
+    CanOptimizeLocalVariables.visit(node.into()).is_continue()
+}
+
+/// The [`Visitor`] used for [`returns_value`].
+#[derive(Debug)]
+struct CanOptimizeLocalVariables;
+
+impl<'ast> Visitor<'ast> for CanOptimizeLocalVariables {
+    type BreakTy = ();
+
+    fn visit_with(&mut self, _node: &'ast crate::statement::With) -> ControlFlow<Self::BreakTy> {
+        ControlFlow::Break(())
+    }
+
+    fn visit_call(&mut self, node: &'ast crate::expression::Call) -> ControlFlow<Self::BreakTy> {
+        if let Expression::Identifier(identifier) = node.function() {
+            if identifier.sym() == Sym::EVAL {
+                return ControlFlow::Break(());
+            }
+        }
+
+        try_break!(node.function().visit_with(self));
+
+        for arg in node.args() {
+            try_break!(arg.visit_with(self));
+        }
+
+        ControlFlow::Continue(())
+    }
+
+    fn visit_function(&mut self, _node: &'ast Function) -> ControlFlow<Self::BreakTy> {
+        ControlFlow::Break(())
+    }
+
+    fn visit_arrow_function(&mut self, _node: &'ast ArrowFunction) -> ControlFlow<Self::BreakTy> {
+        ControlFlow::Break(())
+    }
+
+    fn visit_async_function(&mut self, _node: &'ast AsyncFunction) -> ControlFlow<Self::BreakTy> {
+        ControlFlow::Break(())
+    }
+
+    fn visit_async_arrow_function(
+        &mut self,
+        _node: &'ast AsyncArrowFunction,
+    ) -> ControlFlow<Self::BreakTy> {
+        ControlFlow::Break(())
+    }
+
+    fn visit_class(&mut self, _node: &'ast Class) -> ControlFlow<Self::BreakTy> {
+        ControlFlow::Break(())
+    }
+}
diff --git a/boa_engine/src/bytecompiler/function.rs b/boa_engine/src/bytecompiler/function.rs
index 986fef08dcd..01045f7660a 100644
--- a/boa_engine/src/bytecompiler/function.rs
+++ b/boa_engine/src/bytecompiler/function.rs
@@ -7,7 +7,10 @@ use crate::{
     vm::{CodeBlock, CodeBlockFlags, Opcode},
     Context,
 };
-use boa_ast::function::{FormalParameterList, FunctionBody};
+use boa_ast::{
+    function::{FormalParameterList, FunctionBody},
+    operations::can_optimize_local_variables,
+};
 use boa_gc::Gc;
 use boa_interner::Sym;
 
@@ -148,6 +151,19 @@ impl FunctionCompiler {
             compiler.async_handler = Some(compiler.push_handler());
         }
 
+        let can_optimize_params = can_optimize_local_variables(parameters);
+        let can_optimize_body = can_optimize_local_variables(body);
+        println!("Can optimize params: {can_optimize_params}");
+        println!("Can optimize body: {can_optimize_body}");
+
+        let can_optimize = can_optimize_params
+            && can_optimize_body
+            && !parameters.has_arguments()
+            && !parameters.has_duplicates()
+            && !parameters.has_rest_parameter()
+            && parameters.is_simple();
+        println!("Can optimize function: {can_optimize}");
+
         let (env_label, additional_env) = compiler.function_declaration_instantiation(
             body,
             parameters,