LibJS: Use Vector instead of HashMap in DeclarativeEnvironment

Constructing the HashMap in DeclarativeEnvironment was by far the most
expensive thing when making JavaScript function calls.

As it turns out, we don't really need this to be a HashMap in the first
place, as lookups are cached (by EnvironmentCoordinate) after the first
access, so after that we were not even looking in the HashMap, going
directly to the bindings Vector instead.

This reduces function_declaration_instantiation() from 16% to 9% when
idling in "Biolab Disaster". It also reduces has_binding() from 3% to
1% on the same content.

With these changes, we now actually get to idle a little bit between
game frames on my machine. :^)

1 files changed, 1 insertions, 1 deletions

diff --git a/Userland/Utilities/js.cpp b/Userland/Utilities/js.cpp
index 6672cd01fa..c9ec2e29b5 100644
--- a/Userland/Utilities/js.cpp
+++ b/Userland/Utilities/js.cpp
@@ -1612,7 +1612,7 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
                 auto const& variable = interpreter->global_object();
                 list_all_properties(variable.shape(), variable_name);
 
-                for (String& name : global_environment.declarative_record().bindings()) {
+                for (auto const& name : global_environment.declarative_record().bindings()) {
                     if (name.starts_with(variable_name)) {
                         results.empend(name);
                         results.last().invariant_offset = variable_name.length();