Significantly improve performance of SyntaxVisitor #2536
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Added a commit that stores which slots in |
There are two core ideas here: - Before this change, we were allocating `Syntax.Info` for every visited node. We need a heap-allocated object here because `Syntax` can access its parent. In most cases, however, the syntax node was not stored by the visitor and we would just destroy the `Syntax.Info` after finishing the `visit` call. Instead, check if `Syntax.Info` is uniquely referenced, which means that the the node was not stored. In that case, don’t deallocate the memory but place it into a reuse pool. I have seen reductions in `malloc` calls from ~50,000 to ~100 (500x) in `testEmptyVisitorPerformance`. - Now retain and release calls made up a significant portion of the visitor’s performance. Add some annotations to eliminate reference counting. I added comments for the remaining retain calls. I measured that this improves the performance of the `EmptyParametersRule` in SwiftLint by ~35% compared to `509.0.0` (and by ~50% compared to `510.0.0`). Fixes swiftlang#2091 rdar://114330163
This gets us another ~3% performance improvement in SwiftLint listing time.
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There are two core ideas here:
Syntax.Infofor every visited node. We need a heap-allocated object here becauseSyntaxcan access its parent. In most cases, however, the syntax node was not stored by the visitor and we would just destroy theSyntax.Infoafter finishing thevisitcall. Instead, check ifSyntax.Infois uniquely referenced, which means that the the node was not stored. In that case, don’t deallocate the memory but place it into a reuse pool. I have seen reductions inmalloccalls from ~50,000 to ~100 (500x) intestEmptyVisitorPerformance.I measured that this improves the performance of the
EmptyParametersRulein SwiftLint by ~35% compared to509.0.0(and by ~50% compared to510.0.0).Fixes #2091
rdar://114330163