294247 2025-06-10 04:29:12 -0700 [JSC] Skip index-type update in `tryCloneArrayFromFast` when `fillMode` is `Empty` 2025-06-11 04:03:22 -0700 1 1 1 Unclassified WebKit JavaScriptCore WebKit Local Build Unspecified Unspecified RESOLVED FIXED InRadar P2 Normal --- 1 sosuke sosuke webkit-bug-importer oldest_to_newest 2122694 0 sosuke 2025-06-10 04:29:12 -0700 `tryCloneArrayFromFast` adjusts the result’s index type if the source array contains holes, on the assumption that the holes will be filled with `undefined`. This adjustment is valid only when `fillMode` is `Undefined`, but the current implementation also performs it when `fillMode` is `Empty`. This patch changes to prevents the index-type update when `fillMode` is `Empty`. TipOfTree Patched array-prototype-concat-empty 7.7375+-0.1340 ^ 5.3688+-0.1247 ^ definitely 1.4412x faster 2122695 1 sosuke 2025-06-10 04:29:59 -0700 Pull request: https://github.com/WebKit/WebKit/pull/46536 2122970 2 ews-feeder 2025-06-11 04:02:47 -0700 Committed 296082@main (14ddbfed34e8): <https://commits.webkit.org/296082@main> Reviewed commits have been landed. Closing PR #46536 and removing active labels. 2122971 3 webkit-bug-importer 2025-06-11 04:03:22 -0700 <rdar://problem/153064115>