From d87005736e2522e52702e2c07035c6eab1590f36 Mon Sep 17 00:00:00 2001
From: raskad <32105367+raskad@users.noreply.github.com>
Date: Thu, 19 Dec 2024 19:48:12 +0000
Subject: [PATCH] Skip creation of arguments object if possible (#4087)
* Skip creation of arguments object if possible
* fix lints
---
core/ast/src/scope.rs | 35 ++++++++++++++++++++
core/engine/src/bytecompiler/declarations.rs | 4 +++
2 files changed, 39 insertions(+)
diff --git a/core/ast/src/scope.rs b/core/ast/src/scope.rs
index 08481649955..f453299712a 100644
--- a/core/ast/src/scope.rs
+++ b/core/ast/src/scope.rs
@@ -18,6 +18,7 @@ struct Binding {
lex: bool,
strict: bool,
escapes: bool,
+ accessed: bool,
}
/// A scope maps bound identifiers to their binding positions.
@@ -259,6 +260,7 @@ impl Scope {
.iter_mut()
.find(|b| &b.name == name)
{
+ binding.accessed = true;
if crossed_function_border || eval_or_with {
binding.escapes = true;
}
@@ -296,6 +298,7 @@ impl Scope {
lex: !function_scope,
strict: false,
escapes: self.is_global(),
+ accessed: false,
});
BindingLocator::declarative(
name,
@@ -320,6 +323,7 @@ impl Scope {
lex: true,
strict,
escapes: self.is_global(),
+ accessed: false,
});
}
@@ -583,6 +587,37 @@ impl FunctionScopes {
&self.function_scope
}
+ /// Returns if the arguments object is accessed in this function.
+ #[must_use]
+ pub fn arguments_object_accessed(&self) -> bool {
+ if self
+ .function_scope
+ .inner
+ .bindings
+ .borrow()
+ .first()
+ .filter(|b| b.name == "arguments" && b.accessed)
+ .is_some()
+ {
+ return true;
+ }
+
+ if let Some(scope) = &self.parameters_eval_scope {
+ if scope
+ .inner
+ .bindings
+ .borrow()
+ .first()
+ .filter(|b| b.name == "arguments" && b.accessed)
+ .is_some()
+ {
+ return true;
+ }
+ }
+
+ false
+ }
+
/// Returns the parameters eval scope for this function.
#[must_use]
pub fn parameters_eval_scope(&self) -> Option<&Scope> {
diff --git a/core/engine/src/bytecompiler/declarations.rs b/core/engine/src/bytecompiler/declarations.rs
index 06b91d9293c..73b9d430722 100644
--- a/core/engine/src/bytecompiler/declarations.rs
+++ b/core/engine/src/bytecompiler/declarations.rs
@@ -974,6 +974,10 @@ impl ByteCompiler<'_> {
}
}
+ if arguments_object_needed {
+ arguments_object_needed = scopes.arguments_object_accessed();
+ }
+
// 19-20
drop(self.push_declarative_scope(scopes.parameters_eval_scope()));