[PATCH] D88799: [MemCpyOpt] Check for throwing calls during call slot optimization

[Nikita Popov via Phabricator via llvm-commits]

nikic added inline comments.


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Comment at: llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp:835
+    }
+  }
+
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Replying to @efriedma's comment on https://reviews.llvm.org/D88805#inline-824472: I believe checking for throwing instructions rather than guaranteed-to-transfer is correct here, because cpyDest cannot be read between the call and the copy, as a precondition for the call-slot optimization. So even if one of the instructions does not return, an early write to cpyDest will not be observable, with two caveats:
 * The call itself might read cpyDest. We explicitly protect against this below (see the getModRefInfo and callCapturesBefore checks).
 * We might throw and the catching code might read cpyDest. That's what we protect against here.


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  https://reviews.llvm.org/D88799/new/

https://reviews.llvm.org/D88799