Andreas Kling 43aecd3f90 LibJS: Skip property-table key marking for non-dictionary shapes ...

Shape::visit_edges used to walk every entry of m_property_table and
call PropertyKey::visit_edges on each key. For non-dictionary shapes
that work is redundant: m_property_table is a lazily built cache of
the transition chain, and every key it contains was originally
inserted as some ancestor shape's m_property_key, which is already
kept alive via m_previous.

Intrinsic shapes populated through add_property_without_transition()
in Intrinsics.cpp are not dictionaries and have no m_previous to
reach their keys through, but each of those keys is either a
vm.names.* string or a well-known symbol and is strongly rooted by
the VM for its whole lifetime, so skipping them here is safe too.

Measured on the main WebWorker used by https://www.maptiler.com/maps/
this cuts out ~98% of the PropertyKey::visit_edges calls made by
Shape::visit_edges each GC, reducing time spent in GC by ~1.3 seconds
on my Linux PC while initially loading the map.

2026-04-23 02:14:01 +02:00

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