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LibJS: Make accessing the current function's arguments cheaper

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Instead of going through an environment record, make arguments of the
currently executing function generate references via the argument index,
which can later be resolved directly through the ExecutionContext.
This commit is contained in:
Ali Mohammad Pur 2021-10-07 20:13:22 +03:30 • committed by Andreas Kling
parent da296ffd56
commit 12b283f32f
5 changed files with 207 additions and 4 deletions
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42
Userland/Libraries/LibJS/Runtime/Reference.cpp
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@ -48,6 +48,31 @@ void Reference::put_value(GlobalObject& global_object, Value value)
}
VERIFY(m_base_type == BaseType::Environment);
// Note: Optimisation, not from the spec.
if (m_function_argument_index.has_value()) {
// Note: Modifying this binding requires us to sync with the environment.
if (!m_base_environment) {
auto real_reference = global_object.vm().resolve_binding(m_name.as_string(), m_referenced_function_context->lexical_environment);
m_base_environment = real_reference.m_base_environment;
}
if (!global_object.vm().execution_context_stack().is_empty() && m_referenced_function_context == &global_object.vm().running_execution_context()) {
auto& arguments = m_referenced_function_context->arguments;
auto index = m_function_argument_index.value();
if (arguments.size() > index) {
arguments[index] = value;
} else {
arguments.ensure_capacity(index + 1);
for (size_t i = arguments.size(); i < index; ++i)
arguments.append(js_undefined());
arguments.append(value);
}
m_base_environment->set_mutable_binding(global_object, name().as_string(), value, is_strict());
return;
}
}
VERIFY(m_base_environment);
if (m_environment_coordinate.has_value())
static_cast<DeclarativeEnvironment*>(m_base_environment)->set_mutable_binding_direct(global_object, m_environment_coordinate->index, value, m_strict);
@ -80,6 +105,17 @@ Value Reference::get_value(GlobalObject& global_object) const
}
VERIFY(m_base_type == BaseType::Environment);
// Note: Optimisation, not from the spec.
if (m_function_argument_index.has_value()) {
if (!global_object.vm().execution_context_stack().is_empty() && m_referenced_function_context == &global_object.vm().running_execution_context())
return global_object.vm().argument(m_function_argument_index.value());
if (!m_base_environment) {
auto real_reference = global_object.vm().resolve_binding(m_name.as_string(), m_referenced_function_context->lexical_environment);
m_base_environment = real_reference.m_base_environment;
}
}
VERIFY(m_base_environment);
if (m_environment_coordinate.has_value())
return static_cast<DeclarativeEnvironment*>(m_base_environment)->get_binding_value_direct(global_object, m_environment_coordinate->index, m_strict);
@ -141,6 +177,12 @@ bool Reference::delete_(GlobalObject& global_object)
VERIFY(m_base_type == BaseType::Environment);
// Note: Optimisation, not from the spec.
if (m_function_argument_index.has_value()) {
// This is a direct reference to a function argument.
return false;
}
// c. Return ? base.DeleteBinding(ref.[[ReferencedName]]).
return m_base_environment->delete_binding(global_object, m_name.as_string());
}