311452 2026-04-03 17:07:20 -0700 Build Time Improvement: Move variant-heavy inline functions from CalcTree headers to .cpp files 2026-04-07 11:12:50 -0700 1 1 1 Unclassified WebKit New Bugs WebKit Nightly Build Unspecified Unspecified RESOLVED FIXED InRadar P2 Normal --- 1 bfulgham bfulgham sam simon.fraser webkit-bug-importer oldest_to_newest 2196737 0 bfulgham 2026-04-03 17:07:20 -0700 The CSSCalc::Node (38-type variant) and Style::Calculation::Node (33-type variant) trigger expensive mpark::variant template instantiations (constructor, destructor, move_constructor, switchOn dispatch) in every translation unit that includes their headers. This patch moves convenience functions that create, move, or switchOn these variant types from inline definitions in headers to their corresponding .cpp files. This avoids unnecessary variant template instantiation in files that include the headers but don't call these functions. (1) CSSCalcTree.h => CSSCalcTree.cpp: * isNumeric() (switchOn over 38-type variant)add(), multiply(), subtract() * makeChildWithValueBasedOn() (4 overloads) (2) StyleCalculationTree.h => StyleCalculationTree.cpp: * number(), percentage(), dimension() * add(), multiply(), subtract(), blend() Note: Trivial move constructors/operators (Children, ChildOrNone) were left inline to avoid runtime overhead on hot paths. 2196742 1 bfulgham 2026-04-03 17:35:41 -0700 Build data from -ftrace-time comparing builds: 1. -21.13s (21.26s -> 0.12s, -99.4%) [221 -> 1 TUs] WebCore::CSSCalc::Child::switchOn<(lambda ... 2. -21.01s (21.13s -> 0.12s, -99.4%) [221 -> 1 TUs] WTF::visitOneVariant<0UL, WTF::Visitor<(lambda ... 3. -4.60s (4.64s -> 0.03s, -99.3%) [221 -> 1 TUs] WTF::visitOneVariant<32UL, WTF::Visitor<(lambda ... 4. -2.90s (2.90s -> 0.00s, -100.0%) [200 -> 0 TUs] WebCore::CSSCalc::Child::switchOn<(lambda ... 5. -2.84s (2.84s -> 0.00s, -100.0%) [200 -> 0 TUs] WTF::visitOneVariant<0UL, WTF::Visitor<(lambda ... 6. -1.46s (1.46s -> 0.00s, -99.7%) [229 -> 1 TUs] WebCore::Style::Calculation::makeChild<WebCore::Style::Calculation::Blend> 7. -1.41s (1.42s -> 0.00s, -99.7%) [229 -> 1 TUs] WebCore::Style::Calculation::ChildConstruction<WebCore::Style::Calculation::Blend>::make 8. -1.15s (1.15s -> 0.00s, -99.6%) [221 -> 1 TUs] WebCore::CSSCalc::makeChild<WebCore::CSSCalc::Negate> 9. -1.11s (1.11s -> 0.00s, -99.6%) [221 -> 1 TUs] WebCore::CSSCalc::ChildConstruction<WebCore::CSSCalc::Negate>::make 10. -0.99s (0.99s -> 0.00s, -99.6%) [229 -> 1 TUs] WebCore::Style::Calculation::makeChild<WebCore::Style::Calculation::Negate> 2196743 2 webkit-bug-importer 2026-04-03 17:35:57 -0700 <rdar://problem/174049948> 2196745 3 bfulgham 2026-04-03 17:38:39 -0700 Pull request: https://github.com/WebKit/WebKit/pull/62009 2197701 4 ews-feeder 2026-04-07 11:12:47 -0700 Committed 310727@main (0bd48dfc0abc): <https://commits.webkit.org/310727@main> Reviewed commits have been landed. Closing PR #62009 and removing active labels.