Bug 252904

Summary:	Performance regression on selector match benchmark (add UNLIKELY to help branch prediction)
Product:	WebKit	Reporter:	Matthieu Dubet <m_dubet>
Component:	WebCore Misc.	Assignee:	Nobody <webkit-unassigned>
Status:	RESOLVED FIXED
Severity:	Normal	CC:	webkit-bug-importer
Priority:	P2	Keywords:	InRadar
Version:	WebKit Nightly Build
Hardware:	Unspecified
OS:	Unspecified

Description Matthieu Dubet 2023-02-24 07:36:40 PST

The introduction of css-nesting (original VS resolved selector list) has introduced a small performance regression on selector matching benchmark.

https://perf.webkit.org/v3/#/charts?since=1663309346443&paneList=((22-1649-null-null-(5-2.5-500)))

Adding a UNLIKELY to help the compiler mitigate the performance decrease in the most frequent case (no nesting) could help.

Comment 1 Radar WebKit Bug Importer 2023-02-24 07:37:10 PST

<rdar://problem/105883716>

Comment 2 Matthieu Dubet 2023-02-24 14:03:16 PST

Pull request: https://github.com/WebKit/WebKit/pull/10665

Comment 3 Matthieu Dubet 2023-03-17 08:43:07 PDT

Pull request: https://github.com/WebKit/WebKit/pull/11656

Comment 4 EWS 2023-03-17 14:59:52 PDT

Committed 261809@main (29a558295527): <https://commits.webkit.org/261809@main>

Reviewed commits have been landed. Closing PR #11656 and removing active labels.