[Incremental compilation]: Merge pull request #32219 from davidungar/quick-dependency-bug-fix #32230
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…ug-fix Simplest fix to a dependency bug.
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@swift-ci please test |
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@slavapestov , @CodaFi , @DougGregor |
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@swift-ci please nominate |
slavapestov
approved these changes
Jun 6, 2020
tkremenek
approved these changes
Jun 9, 2020
AnthonyLatsis
added
swift 5.3
🍒 release cherry pick
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Fixes a regression from 5.2. Undo a dependency optimization that causes miscompiles.
Explanation: In order to realize a benefit from type-body-fingerprints, code was added to omit a dependency wherein a file A depended upon a type defined in that same file A. However, if that same type is also used subsequently to its definition in the same file A, the omission causes miscompiles because a use of that type in file B depends upon file A. The omission causes file A to be insensitive to changes in the type, and thus causes the use in file B to be insensitive to changes in the type. In the future, refinements in the dependency system may well allow us to reenable this optimization, but for now, we need to disable the optimization in order to prevent miscompilations.
Origination: d09c906 Fed 27, 11:38 pm
Risk: Zero, because all it does is add dependencies. It effectively puts us back to pre-type-body-fingerprints.
Reviewed by: Slava Pestov
Testing: CI PR tests + the perturbation tester
Radar:rdar://64074744