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LibJS: Make JS::Shape smaller by using OwnPtr<HashMap> for transitions

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Many shapes don't have any forward transitions to cache, so we can save
a bunch of memory (and time) by only creating the cache maps when
actually needed.
This commit is contained in:
Andreas Kling 2022-01-31 12:43:30 +01:00
parent 51e5cc4e13
commit 1469057033
2 changed files with 21 additions and 11 deletions
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28
Userland/Libraries/LibJS/Runtime/Shape.cpp
View file

@ -25,12 +25,14 @@ Shape* Shape::create_unique_clone() const
Shape* Shape::get_or_prune_cached_forward_transition(TransitionKey const& key)
{
auto it = m_forward_transitions.find(key);
if (it == m_forward_transitions.end())
if (!m_forward_transitions)
return nullptr;
auto it = m_forward_transitions->find(key);
if (it == m_forward_transitions->end())
return nullptr;
if (!it->value) {
// The cached forward transition has gone stale (from garbage collection). Prune it.
m_forward_transitions.remove(it);
m_forward_transitions->remove(it);
return nullptr;
}
return it->value;
@ -38,12 +40,14 @@ Shape* Shape::get_or_prune_cached_forward_transition(TransitionKey const& key)
Shape* Shape::get_or_prune_cached_prototype_transition(Object* prototype)
{
auto it = m_prototype_transitions.find(prototype);
if (it == m_prototype_transitions.end())
if (!m_prototype_transitions)
return nullptr;
auto it = m_prototype_transitions->find(prototype);
if (it == m_prototype_transitions->end())
return nullptr;
if (!it->value) {
// The cached prototype transition has gone stale (from garbage collection). Prune it.
m_prototype_transitions.remove(it);
m_prototype_transitions->remove(it);
return nullptr;
}
return it->value;
@ -55,7 +59,9 @@ Shape* Shape::create_put_transition(const StringOrSymbol& property_name, Propert
if (auto* existing_shape = get_or_prune_cached_forward_transition(key))
return existing_shape;
auto* new_shape = heap().allocate_without_global_object<Shape>(*this, property_name, attributes, TransitionType::Put);
m_forward_transitions.set(key, new_shape);
if (!m_forward_transitions)
m_forward_transitions = make<HashMap<TransitionKey, WeakPtr<Shape>>>();
m_forward_transitions->set(key, new_shape);
return new_shape;
}
@ -65,7 +71,9 @@ Shape* Shape::create_configure_transition(const StringOrSymbol& property_name, P
if (auto* existing_shape = get_or_prune_cached_forward_transition(key))
return existing_shape;
auto* new_shape = heap().allocate_without_global_object<Shape>(*this, property_name, attributes, TransitionType::Configure);
m_forward_transitions.set(key, new_shape);
if (!m_forward_transitions)
m_forward_transitions = make<HashMap<TransitionKey, WeakPtr<Shape>>>();
m_forward_transitions->set(key, new_shape);
return new_shape;
}
@ -74,7 +82,9 @@ Shape* Shape::create_prototype_transition(Object* new_prototype)
if (auto* existing_shape = get_or_prune_cached_prototype_transition(new_prototype))
return existing_shape;
auto* new_shape = heap().allocate_without_global_object<Shape>(*this, new_prototype);
m_prototype_transitions.set(new_prototype, new_shape);
if (!m_prototype_transitions)
m_prototype_transitions = make<HashMap<Object*, WeakPtr<Shape>>>();
m_prototype_transitions->set(new_prototype, new_shape);
return new_shape;
}

4
Userland/Libraries/LibJS/Runtime/Shape.h
View file

@ -106,8 +106,8 @@ private:
mutable OwnPtr<HashMap<StringOrSymbol, PropertyMetadata>> m_property_table;
HashMap<TransitionKey, WeakPtr<Shape>> m_forward_transitions;
HashMap<Object*, WeakPtr<Shape>> m_prototype_transitions;
OwnPtr<HashMap<TransitionKey, WeakPtr<Shape>>> m_forward_transitions;
OwnPtr<HashMap<Object*, WeakPtr<Shape>>> m_prototype_transitions;
Shape* m_previous { nullptr };
StringOrSymbol m_property_name;
Object* m_prototype { nullptr };