LibJS/JIT: Fast paths for object==object and Array.length #21910
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There are more fast paths to be added here, just starting with this one since it's heavy on Kraken/ai-astar.js :^)
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| @@ -221,6 +221,8 @@ class Object : public Cell { | |||
| 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); } | |||
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| static FlatPtr has_magical_length_property_offset() { return OFFSET_OF(Object, m_has_magical_length_property); } | |||
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This might belong as a youtube comment, but I was thinking that since you're adding a magic property to Array, why not call it isArray, instead of has_magical_length_property_offset? Then you also have a clear fast path for Array.isArray() (ES5).
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That doesn't seem safe if the value is a Proxy object 🤔
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ahh yes. I wrote my comment wrong. I actually meant the m_has_magical_length_property = true; property in the Array constructor. Sorry for the confusion.
Moulberry
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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) :^)
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Combined, these yield a strong ~2.7x speed-up on Kraken/ai-astar.js :^)