6.1: [SILCombine] Fix apply(convert_function(@guaranteed)) with an @owned operand. #78529
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A partial revert of 428ab47.
The operands to the original apply are cast via an ownership forwarding instruction to the appropriate type for the rewritten apply. ``` %converted = convert_function %original to $(NewTy) -> () apply %converted(%operand) ``` -> ``` %cast = cast %operand to $OriginalTy apply %original(%cast) ``` Previously, when an original operand is owned but the new apply does not consume that operand, the newly added cast would consume the original operand (an owned value)--something the original code being replaced did not do. ``` %converted = convert_function %original to $(NewTy) -> () apply %converted(%operand : @guaranteed) // %operand remains available ``` -> ``` %cast = cast %operand to $OriginalTy // consumes %operand! apply %original(%cast : @guaranteed) // %operand is not available! ``` This is incorrect for the complementary reasons that the result of the cast is leaked and any uses of the original operand subsequent to the new apply are uses-after-consume. Here, this is fixed by borrowing the original operand before casting in this case. rdar://142570727
On main type annotations are not always required but on 6.1 they are.
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@swift-ci please test |
tbkka
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Jan 9, 2025
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Explanation: Fix SIL ownership invalidity introduced by SILCombine.
The pass rewrites applies of cast functions to applies of uncast functions, casting the arguments instead. When an argument is a value (not an address), the introduced cast consumes the value. If the argument is owned but the original apply did not consume it, it's incorrect to replace that original apply with a sequence instructions that do consume it (i.e. the cast). To avoid this, in this situation, borrow the value before casting it.
Also, enable this optimization for
try_applyinstructions.Scope: Affects optimized code.
Issue: rdar://142570727
Original PR: #78507
Risk: Low.
Testing: Added tests.
Reviewer: Erik Eckstein ( @eeckstein ), Andrew Trick ( @atrick )