5.9: [InstructionDeleter] Don't delete-as dead instructions which produce owned move-only values. #68111
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Build failures are caused by lacking the overhaul to the SIL testing infrastructure on the release/5.9. Will raise a further patch to adapt. |
Deleting instructions which produce such values could result in shortening the lifetime of a move-only value. This is illegal because according to language rules, the lifetime of move-only values is fixed. rdar://114351349
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Description: Many passes use the InstructionDeleter, requesting that it try to delete an instruction if its dead. The deleter has a number of checks to determine what counts as "dead".
Among those checks is an early exit, affirming that an instruction which satisfies a few other conditions is indeed dead if it satisfies
getSingleValueCopyOrCast. At least one instruction (move_value) satisfying that predicate may produce an owned move-only value. Such an instruction must not be deleted as dead.Here, an additional condition is added prior to considering the
getSingleValueCopyOrCastpredicate; namely, whether the instruction produces an owned move-only value. If it does, the deleter determines that the instruction is not dead and does not delete it.Risk: Low.
Scope: Narrow. The change only affects move-only values.
Original PR: #68108
Reviewed By: Andrew Trick ( @atrick )
Testing: Added a test.
Resolves: rdar://114351349