278700 2024-08-26 22:29:12 -0700 Reduce ThreadSafeRefCounted compile time 2024-08-28 15:25:50 -0700 1 1 1 Unclassified WebKit Web Template Framework WebKit Nightly Build Unspecified Unspecified RESOLVED FIXED InRadar P2 Normal --- 278821 1 g_squelart g_squelart webkit-bug-importer oldest_to_newest 2055533 0 g_squelart 2024-08-26 22:29:12 -0700 Found with -ftime-trace and ClangBuildAnalyzer, the top-3 "templates that took longest to instantiate" are: > 110395 ms (35802 times, avg 3 ms): WTF::Function<void ()>::Function<(lambda at /Volumes/WebKit/Internal/WebKit/WebKitBuild/Debug/usr/local/include/wtf/ThreadSafeRefCounted.h:143:27), void> > 76389 ms (35802 times, avg 2 ms): WTF::makeUnique<WTF::Detail::CallableWrapper<(lambda at /Volumes/WebKit/Internal/WebKit/WebKitBuild/Debug/usr/local/include/wtf/ThreadSafeRefCounted.h:143:27), void>, (lambda at /Volumes/WebKit/Internal/WebKit/WebKitBuil... > 66481 ms (35802 times, avg 1 ms): std::make_unique<WTF::Detail::CallableWrapper<(lambda at /Volumes/WebKit/Internal/WebKit/WebKitBuild/Debug/usr/local/include/wtf/ThreadSafeRefCounted.h:143:27), void>, (lambda at /Volumes/WebKit/Internal/WebKit/WebKitBui... And at #25 of "Template sets that took longest to instantiate": > 129369 ms (35838 times, avg 3 ms): WTF::ThreadSafeRefCounted<$>::deref This is due to ThreadSafeRefCounted<T, DestructionThread>::deref doing a `switch` on the templated enum `DestructionThread`, and for some of them moving a lambda into a `WTF::Function`, which itself always calls WTF::makeUnique. By changing this `switch` into a sequence of `if constexpr` blocks, it's possible to pretty much squash these big compile times out of the top-1000, only leaving a small template set taking less than 4% of the original time: > 4666 ms (2065 times, avg 2 ms): WTF::ThreadSafeRefCounted<$>::deref 2055534 1 webkit-bug-importer 2024-08-26 22:29:20 -0700 <rdar://problem/134756505> 2055535 2 g_squelart 2024-08-26 22:40:28 -0700 Pull request: https://github.com/WebKit/WebKit/pull/32749 2056102 3 ews-feeder 2024-08-28 15:25:48 -0700 Committed 282871@main (9ed2e706b2c7): <https://commits.webkit.org/282871@main> Reviewed commits have been landed. Closing PR #32749 and removing active labels.