Branch: refs/heads/main
Home: https://github.com/WebKit/WebKit
Commit: edd953757f9fb56212a3fd02b16b79a1e8f51d8d
https://github.com/WebKit/WebKit/commit/edd953757f9fb56212a3fd02b16b79a1e8f51d8d
Author: Sosuke Suzuki <[email protected]>
Date: 2026-08-10 (Mon, 10 Aug 2026)
Changed paths:
M Source/JavaScriptCore/runtime/StructureRareData.cpp
M Source/JavaScriptCore/runtime/StructureRareData.h
Log Message:
-----------
[JSC] Shrink `StructureRareData` back to 96 bytes
https://bugs.webkit.org/show_bug.cgi?id=321423
Reviewed by Keith Miller.
317978@main appended a 2-bit TriState bit-field to StructureRareData, whose
members already filled exactly 96 bytes. The new field spilled into byte 97,
so sizeof(StructureRareData) became 104 and its IsoSubspace cell grew from
96 to 112 bytes.
Make m_activeReplacementWatchpointSet a 30-bit bit-field so that it shares a
32-bit word with m_cachedHasDefaultToPrimitiveFastAndNonObservable. The counter
tracks the number of entries in m_replacementWatchpointSets, which is bounded by
the number of property offsets and cannot approach 2^30. Also add a
static_assert on sizeof(StructureRareData) so that this does not regress
silently again; like the existing PropertyWatchpointMap assert it is NDEBUG-only
because HashTable grows in debug builds.
* Source/JavaScriptCore/runtime/StructureRareData.h:
Canonical link: https://commits.webkit.org/318955@main
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