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LibJS: Stop eagerly creating the backing store for IndexedProperties

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The vast majority of objects do not, and are unlikely to ever need
indexed property storage. By delaying the creation of the backing
store of IndexedProperties we reduce the memory used by each object
and reduce allocation and deallocation by somewhere between 20 and
30%
This commit is contained in:
Anonymous 2022-02-11 22:46:17 -08:00 • committed by Andreas Kling
parent d1cc67bbe1
commit 34a4ce7955
2 changed files with 32 additions and 4 deletions
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23
Userland/Libraries/LibJS/Runtime/IndexedProperties.cpp
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@ -77,6 +77,10 @@ bool SimpleIndexedPropertyStorage::set_array_like_size(size_t new_size)
return true;
}
GenericIndexedPropertyStorage::GenericIndexedPropertyStorage()
{
}
GenericIndexedPropertyStorage::GenericIndexedPropertyStorage(SimpleIndexedPropertyStorage&& storage)
{
m_array_size = storage.array_like_size();
@ -216,11 +220,14 @@ void IndexedPropertyIterator::skip_empty_indices()
Optional<ValueAndAttributes> IndexedProperties::get(u32 index) const
{
if (!m_storage)
return {};
return m_storage->get(index);
}
void IndexedProperties::put(u32 index, Value value, PropertyAttributes attributes)
{
ensure_storage();
if (m_storage->is_simple_storage() && (attributes != default_attributes || index > (array_like_size() + SPARSE_ARRAY_HOLE_THRESHOLD))) {
switch_to_generic_storage();
}
@ -230,12 +237,14 @@ void IndexedProperties::put(u32 index, Value value, PropertyAttributes attribute
void IndexedProperties::remove(u32 index)
{
VERIFY(m_storage);
VERIFY(m_storage->has_index(index));
m_storage->remove(index);
}
bool IndexedProperties::set_array_like_size(size_t new_size)
{
ensure_storage();
auto current_array_like_size = array_like_size();
// We can't use simple storage for lengths that don't fit in an i32.
@ -252,6 +261,8 @@ bool IndexedProperties::set_array_like_size(size_t new_size)
size_t IndexedProperties::real_size() const
{
if (!m_storage)
return 0;
if (m_storage->is_simple_storage()) {
auto& packed_elements = static_cast<const SimpleIndexedPropertyStorage&>(*m_storage).elements();
size_t size = 0;
@ -266,6 +277,8 @@ size_t IndexedProperties::real_size() const
Vector<u32> IndexedProperties::indices() const
{
if (!m_storage)
return {};
if (m_storage->is_simple_storage()) {
const auto& storage = static_cast<const SimpleIndexedPropertyStorage&>(*m_storage);
const auto& elements = storage.elements();
@ -285,8 +298,18 @@ Vector<u32> IndexedProperties::indices() const
void IndexedProperties::switch_to_generic_storage()
{
if (!m_storage) {
m_storage = make<GenericIndexedPropertyStorage>();
return;
}
auto& storage = static_cast<SimpleIndexedPropertyStorage&>(*m_storage);
m_storage = make<GenericIndexedPropertyStorage>(move(storage));
}
void IndexedProperties::ensure_storage()
{
if (!m_storage)
m_storage = make<SimpleIndexedPropertyStorage>();
}
}