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LibJS: Skip some declarative env allocations in function instantiation

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If all lexical declaration use local variables then there is no need
to allocate declarative environment.

With this change we skip ~3x more environment allocations on Github.
This commit is contained in:
Aliaksandr Kalenik
2024-05-04 22:36:56 +02:00
committed by Andreas Kling
parent 5da9af435e
commit f21c0f9dcd
3 changed files with 13 additions and 2 deletions
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4
Userland/Libraries/LibJS/Runtime/ECMAScriptFunctionObject.cpp
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@@ -308,7 +308,7 @@ ECMAScriptFunctionObject::ECMAScriptFunctionObject(DeprecatedFlyString name, Byt
// 30. If strict is false, then
if (!m_strict) {
bool can_elide_declarative_environment = !m_contains_direct_call_to_eval && (!scope_body || !scope_body->has_lexical_declarations());
bool can_elide_declarative_environment = !m_contains_direct_call_to_eval && (!scope_body || !scope_body->has_non_local_lexical_declarations());
if (can_elide_declarative_environment) {
lex_environment_size = var_environment_size;
} else {
@@ -870,7 +870,7 @@ ThrowCompletionOr<void> ECMAScriptFunctionObject::function_declaration_instantia
// Optimization: We avoid creating empty top-level declarative environments in non-strict mode, if both of these conditions are true:
// 1. there is no direct call to eval() within this function
// 2. there are no lexical declarations that would go into the environment
bool can_elide_declarative_environment = !m_contains_direct_call_to_eval && (!scope_body || !scope_body->has_lexical_declarations());
bool can_elide_declarative_environment = !m_contains_direct_call_to_eval && (!scope_body || !scope_body->has_non_local_lexical_declarations());
if (can_elide_declarative_environment) {
lex_environment = var_environment;
} else {