End lifetime and deallocating deinits #7858
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@swift-ci Please smoke test and merge |
This is the lifetime ending variant of fix_lifetime. It is a lie to the ownership verifier that a value is being consumed along a path. Its intention is to be used to allow for the static verification of ownership in deallocating deinits which for compatibility with objective-c have weird ownership behavior. See the commit merged with this commit for more information.
…inits using end_lifetime. The issue here is that: 1. Self is passed into deallocating deinits at +1. 2. Destroying deinits take in self as a +0 value that is then returned at +1. This means that the lifetime of self can not be modeled statically in a deallocating deinit without analyzing the body of the destroying deinit (something that violates semantic sil). Thus we add an artifical destroy of self before the actual destroy of self so that the verifier can understand that self is being properly balanced. rdar://29791263
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@swift-ci Please smoke test and merge |
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@swift-ci Please smoke test and merge |
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This PR contains two commits:
b4923b2. This commit adds a new SIL instruction called end_lifetime. It is the destroying use equivalent of fix_lifetime. Its intent is to enable SILGen to in certain cases lie about ownership to the verifier to fix some corner cases. It is eliminated when the ownership model eliminator runs.
0e89d6e. This uses end_lifetime to special case the lifetime of self in destructors. Specifically:
a. Self is passed into deallocating deinits at +1.
b. Destroying deinits take in self as a +0 value that is then returned at +1.
This means that the lifetime of self can not be modeled statically in a
deallocating deinit without analyzing the body of the destroying deinit
(something that violates semantic sil). Thus we add an artifical destroy of
self before the actual destroy of self so that the verifier can understand
that self is being properly balanced.
rdar://29791263