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LibJS/JIT: Add fast path for GetById of Array.length

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Array.length is magical (since it has to reflect the number of elements
in the object's property storage).

We now handle it specially in jitted code, giving us a massive speed-up
on Kraken/ai-astar.js (and probably many other things as well) :^)
This commit is contained in:
Andreas Kling 2023-11-12 15:04:23 +01:00
parent e41f0d9dec
commit b532dedc91
3 changed files with 65 additions and 0 deletions
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1
Userland/Libraries/LibJS/Runtime/Array.cpp
View file

@ -64,6 +64,7 @@ NonnullGCPtr<Array> Array::create_from(Realm& realm, Vector<Value> const& elemen
Array::Array(Object& prototype)
: Object(ConstructWithPrototypeTag::Tag, prototype)
{
m_has_magical_length_property = true;
}
// 10.4.2.4 ArraySetLength ( A, Desc ), https://tc39.es/ecma262/#sec-arraysetlength

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

@ -221,6 +221,8 @@ public:
static FlatPtr may_interfere_with_indexed_property_access_offset() { return OFFSET_OF(Object, m_may_interfere_with_indexed_property_access); }
static FlatPtr indexed_properties_offset() { return OFFSET_OF(Object, m_indexed_properties); }
static FlatPtr has_magical_length_property_offset() { return OFFSET_OF(Object, m_has_magical_length_property); }
protected:
enum class GlobalObjectTag { Tag };
enum class ConstructWithoutPrototypeTag { Tag };
@ -238,6 +240,8 @@ protected:
// [[ParameterMap]]
bool m_has_parameter_map { false };
bool m_has_magical_length_property { false };
private:
void set_shape(Shape& shape) { m_shape = &shape; }