6.0: [MoveOnlyAddressChecker] Fix representation for consumed fields. #72497
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The function is long and will get longer.
The name `livenessUses` doesn't readily communicate the fact that those uses are all non-consuming.
Previously, whenever an instruction was recorded as a final consume, a new entry was added to finalBlockConsumes. Here, this is changed to add the new bits being consumed by the instruction to the preexisting SmallBitVector, if there is one.
An instruction can consume multiple (discontiguous) fields. Use a SmallBitVector to track the fields consumed by an instruction rather than a TypeTreeLeafRange. rdar://125103951
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@swift-ci please test |
tbkka
approved these changes
Mar 21, 2024
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Explanation: Fix a class of overconsumes by teaching the move-only address checker that an instruction can consume multiple fields.
An instruction can consume multiple fields of an aggregate which is being checked. For example,
apply %fn(%field1, %field3). Where%field1and%field3are noncontiguous fields of some struct.Previously, for a single instruction, the checker only tracked a single contiguous range of bits which the instruction consumed. It couldn't represent instructions such as this apply. Consequently, it failed to recognize that fields of the aggregate beyond the first it examined were consumed by the instruction. The result was an overconsume of each field beyond the first.
Here, this is fixed by associating a vector of bits with each instruction.
Scope: Affects move-only checking.
Issue: rdar://125103951
Original PR: #72463
Risk: Low.
Testing: Added test case that was previously miscompiled.
Reviewer: Joe Groff ( @jckarter )