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LibJS: Don't punish large arrays with generic indexed property storage

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This patch rethinks the way indexed property storage works:

Instead of having a cut-off point at 200 elements where we always move
to generic property storage, we now allow arrays to stay in simple mode
as long as we don't create a gap/hole larger than 200 elements.

We also simplify generic storage to only have a hash map (for now)
instead of juggling both a vector and a hash map. This is mostly fine
since the vast majority of arrays get to stay simple now.

This is a huge speedup on anything that uses basic JS arrays with more
than 200 elements in them. :^)
This commit is contained in:
Andreas Kling 2021-03-21 11:33:45 +01:00
parent dee0c46c9b
commit d0664ce6c9
3 changed files with 52 additions and 93 deletions
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13
Userland/Libraries/LibJS/Runtime/IndexedProperties.h
View file

@ -32,9 +32,6 @@
namespace JS {
const u32 SPARSE_ARRAY_THRESHOLD = 200;
const u32 MIN_PACKED_RESIZE_AMOUNT = 20;
struct ValueAndAttributes {
Value value;
PropertyAttributes attributes { default_attributes };
@ -88,6 +85,8 @@ public:
private:
friend GenericIndexedPropertyStorage;
void grow_storage_if_needed();
size_t m_array_size { 0 };
Vector<Value> m_packed_elements;
};
@ -105,16 +104,14 @@ public:
virtual ValueAndAttributes take_first() override;
virtual ValueAndAttributes take_last() override;
virtual size_t size() const override { return m_packed_elements.size() + m_sparse_elements.size(); }
virtual size_t size() const override { return m_sparse_elements.size(); }
virtual size_t array_like_size() const override { return m_array_size; }
virtual void set_array_like_size(size_t new_size) override;
const Vector<ValueAndAttributes>& packed_elements() const { return m_packed_elements; }
const HashMap<u32, ValueAndAttributes>& sparse_elements() const { return m_sparse_elements; }
private:
size_t m_array_size { 0 };
Vector<ValueAndAttributes> m_packed_elements;
HashMap<u32, ValueAndAttributes> m_sparse_elements;
};
@ -141,7 +138,7 @@ class IndexedProperties {
public:
IndexedProperties() = default;
IndexedProperties(Vector<Value>&& values)
explicit IndexedProperties(Vector<Value> values)
: m_storage(make<SimpleIndexedPropertyStorage>(move(values)))
{
}
@ -174,8 +171,6 @@ public:
for (auto& value : static_cast<SimpleIndexedPropertyStorage&>(*m_storage).elements())
callback(value);
} else {
for (auto& element : static_cast<const GenericIndexedPropertyStorage&>(*m_storage).packed_elements())
callback(element.value);
for (auto& element : static_cast<const GenericIndexedPropertyStorage&>(*m_storage).sparse_elements())
callback(element.value.value);
}