5.9: [ClosureSpecializer] Don't release trivial noescape try_apply argument twice. #66274
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When a specialization is created, in the original function, releases are added in two different places: (1) `ClosureSpecCloner::populateCloned` (2) `rewriteApplyInst` In the former, releases are added for closures which are guaranteed or trivial noescape (but with owned convention). In the latter, releases are added for closures that are owned. Previously, when emitting releases at (2), whether the closure was trivial noescape wasn't considered. The result was inserting the releases twice, an overrelease. Here, fix (2) to recognize trivial noescape as not +1. rdar://110058964
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@swift-ci please test |
tbkka
approved these changes
Jun 1, 2023
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Description: ClosureSpecializer creates releases for the closure passed as an parameter to a
try_applythat is specialized. These releases are created in (1)ClosureSpecCloner::populateClonedand (2)rewriteApplyInst, depending on the effective ownership of the closure: in (1) they are inserted for closures passed without an increment of the retain count (done e.g. for closures passed as an@guaranteedparameter); in (2) they are inserted for closures passed with an increment of the retain count (done e.g. for closures passed as an@ownedparameter).Among the closures that are passed without an increment of the retain count are those which are noescape (
SILFunctionType::isTrivialNoEscape). That is true even when the closure is passed as an@ownedparameter. The condition of (1) under which releases are added for the closure correctly included consideration of theisTrivialNoEscapepredicate of the closure's type; consequently that code inserts releases in both of thetry_apply's destination blocks. The condition of (2) under which releases were added for the closure incorrectly failed to consider theisTrivialNoEscapepredicate; consequently, that code also inserted releases in both of the destination blocks. The result was adding two releases in each destination block, one of each of which was an overrelease.The fix is just to consider the
isTrivialNoEscapepredicate in (2).Risk: Low. The patch adds a predicate to the bailout condition of (2) that complements an existing use of the same predicate in the condition of (1).
Scope: Narrow. This only affects releases for noescape closures passed as owned arguments to
try_applys which are specialized.Original PR: #66263
Reviewed By: Erik Eckstein ( @eeckstein ), Arnold Schwaigofer ( @aschwaighofer )
Testing: Added test case that previously inserted double release.
Resolves: rdar://110058964