[6.2][cxx-interop] Delay lowering unowned convention until ownership elimination #84768
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…elimination Explanation: Unowned result conventions do not work well with OSSA. Retain the result right after the call when we come out of OSSA so we can treat the returned value as if it was owned when we do optimizations. This fix a miscompilation due to the DestroyAddrHoisting pass hoisting destroys above copies with unowned sources. When the destroyed object was the last reference to the pointed memory the copy is happening too late resulting in a use after free. Issues: rdar://160462854 Original PRs: swiftlang#84612 Risk: We change where retaining of the unowned return values happen in the optimization pipeline. It is hard to anticipate all the possible effects but it should make the optimizer more correct. Testing: Added a compiler test. Reviewers: @eeckstein, @atrick
Xazax-hun
added
c++ interop
|
@swift-ci please test |
DougGregor
approved these changes
Oct 8, 2025
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Explanation: Unowned result conventions do not work well with OSSA. Retain the result right after the call when we come out of OSSA so we can treat the returned value as if it was owned when we do optimizations.
This fix a miscompilation due to the DestroyAddrHoisting pass hoisting destroys above copies with unowned sources. When the destroyed object was the last reference to the pointed memory the copy is happening too late resulting in a use after free.
Issues: rdar://160462854
Original PRs: #84612
Risk: We change where retaining of the unowned return values happen in the optimization pipeline. It is hard to anticipate all the possible effects but it should make the optimizer more correct.
Testing: Added a compiler test.
Reviewers: @eeckstein, @atrick