Branch: refs/heads/main
Home: https://github.com/WebKit/WebKit
Commit: 058338e8d64f6c036d5c619c0efe3eb4a2c2e0f4
https://github.com/WebKit/WebKit/commit/058338e8d64f6c036d5c619c0efe3eb4a2c2e0f4
Author: Tyler Wilcock <[email protected]>
Date: 2026-05-13 (Wed, 13 May 2026)
Changed paths:
M Source/WebCore/accessibility/AXCoreObject.cpp
Log Message:
-----------
AX: Reduce parent lookups in unignoredChildren pre-order traversal
https://bugs.webkit.org/show_bug.cgi?id=314691
rdar://176932652
Reviewed by Dominic Mazzoni.
Samples taken during AX queries showed nextSiblingIncludingIgnored
as ~95% of time in stitchedUnignoredChildren -> unignoredChildren ->
nextInPreOrder. Each call went through parentObject(), a virtual call
whose cost varies by subclass (HashMap lookup on AXIsolatedObject; DOM
traversal + axObjectCache lookup on AccessibilityRenderObject /
AccessibilityNodeObject) but is always non-trivial. The traversal was
paying for that lookup twice per ascended level. Two adjustments cut
the per-hop work:
1. nextInPreOrder: replace the pre-loop nextSiblingIncludingIgnored()
call + in-loop parentObject() ascent with a single loop that fetches
parent once per level. In the non-cross-frame case, the sibling-search
parent and ascent parent are the same value, so the ascent reuses it
via WTF::move, eliminating the duplicate parentObject() call and the
accompanying RefPtr ref()/deref() per ascended level.
2. unignoredChildren: for ignored or invalid descendants, inline the
descent step (matching nextInPreOrder's Column / TableHeaderContainer
role guard via shouldSetChildIndexInParent()) instead of falling back
to nextInPreOrder(). The function already had its own sibling-or-
ascend loop that caches parent + siblings across sibling hops, but the
nextInPreOrder() fallback was invalidating that cache every time the
traversal crossed an ignored descendant. With the fallback gone,
cached parent/siblings now survive through ignored-descendant
traversal, and the per-hop cost drops to descendant->indexInParent() + a
vector index.
* Source/WebCore/accessibility/AXCoreObject.cpp:
(WebCore::AXCoreObject::unignoredChildren):
(WebCore::AXCoreObject::nextInPreOrder):
Canonical link: https://commits.webkit.org/313164@main
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