From a3af7ca1a039e87e0740de06c660797fb610dfde Mon Sep 17 00:00:00 2001
From: Aliaksandr Kalenik <kalenik.aliaksandr@gmail.com>
Date: Wed, 30 Jul 2025 12:10:17 +0200
Subject: [PATCH] LibJS: Skip PrivateEnvironment allocation if possible

If class doesn't have any private fields, we could avoid allocating
PrivateEnvironment for it.

This allows us to skip thousands of unnecessary PrivateEnvironment
allocations on Discord.
---
 Libraries/LibJS/Bytecode/ASTCodegen.cpp | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/Libraries/LibJS/Bytecode/ASTCodegen.cpp b/Libraries/LibJS/Bytecode/ASTCodegen.cpp
index 32dfc18cc5b..cb376d2e5a5 100644
--- a/Libraries/LibJS/Bytecode/ASTCodegen.cpp
+++ b/Libraries/LibJS/Bytecode/ASTCodegen.cpp
@@ -2892,11 +2892,14 @@ Bytecode::CodeGenerationErrorOr<Optional<ScopedOperand>> ClassExpression::genera
     if (m_super_class)
         super_class = TRY(m_super_class->generate_bytecode(generator)).value();
 
-    generator.emit<Op::CreatePrivateEnvironment>();
-
+    bool did_emit_private_environment_allocation = false;
     for (auto const& element : m_elements) {
         auto opt_private_name = element->private_bound_identifier();
         if (opt_private_name.has_value()) {
+            if (!did_emit_private_environment_allocation) {
+                generator.emit<Op::CreatePrivateEnvironment>();
+                did_emit_private_environment_allocation = true;
+            }
             generator.emit<Op::AddPrivateName>(generator.intern_identifier(*opt_private_name));
         }
     }
@@ -2920,7 +2923,9 @@ Bytecode::CodeGenerationErrorOr<Optional<ScopedOperand>> ClassExpression::genera
     auto dst = choose_dst(generator, preferred_dst);
     generator.emit_with_extra_slots<Op::NewClass, Optional<Operand>>(elements.size(), dst, super_class.has_value() ? super_class->operand() : Optional<Operand> {}, *this, lhs_name, elements);
 
-    generator.emit<Op::LeavePrivateEnvironment>();
+    if (did_emit_private_environment_allocation) {
+        generator.emit<Op::LeavePrivateEnvironment>();
+    }
 
     return dst;
 }