[DCE] Don't delete instructions which consume escaping values. #80766
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When DCE deletes instructions as dead, if the instruction ends one of its operands lifetimes, it must insert a compensating lifetime end. When the def block of the value and the parent block of the instruction are different, it uses lifetime completion. Lifetime completion relies on complete liveness, which doesn't and can't exist for values with pointer escapes. The result is ending lifetimes too early. Avoid this scenario by marking such instructions live. In the fullness of time, it may be possible to track the deleted instruction's "location" even in the face of deletions of adjacent instructions and parent blocks and to insert the lifetime end at that location. rdar://149007151
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@swift-ci please test |
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@swift-ci please benchmark |
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@swift-ci please test source compatibility |
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@swift-ci please test windows platform |
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This is the fix for #80731 |
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When DCE deletes instructions as dead, if the instruction ends one of its operands lifetimes, it must insert a compensating lifetime end. When the def block of the value and the parent block of the instruction are different, it uses lifetime completion. Lifetime completion relies on complete liveness, which doesn't and can't exist for values with pointer escapes. The result is ending lifetimes too early.
Avoid this scenario by marking such instructions live.
In the fullness of time, it may be possible to track the deleted instruction's "location" even in the face of deletions of adjacent instructions and parent blocks and to insert the lifetime end at that location.
rdar://149007151