6.0: [SILGen] Store_borrow into in_guaranteed. #74209
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If a marked location is used by `store_borrow`s, then all its users are `store_borrow`s or `dealloc_stack`s, so there's nothing to destroy.
Don't create a copy in order to pass a value `@in_guaranteed`. Just `store_borrow` the value. rdar://128710064
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@swift-ci please test |
tbkka
approved these changes
Jun 7, 2024
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Explanation: Fix a move-checker diagnose-on-valid.
When generating reabstraction thunks, it may be necessary to convert a value to an address. This is done by creating a temporary allocation and somehow storing the value to it. Previously, if the value was
@guaranteed, this always entailed creating a copy of the value and storing the copy. The copy was necessary because thestoreinstruction consumes the value. This was a particular problem for non-copyable types: the move-checker doesn't currently promotecopy_value+storetostore_borrow. As a result the copy remained and was diagnosed.Here, the extra copy is eliminated by using the
store_borrowinstruction instead which doesn't consume the stored value. This required teaching the move-checker not to insert destroys after last uses of guaranteedalloc_stacks(i.e. those which arestore_borrowdestinations).Scope: Affects noncopyable code and reabstraction thunks.
Issue: rdar://128710064
Original PR: #74157
Risk: Low.
Testing: Added tests.
Reviewer: Joe Groff ( @jckarter )