[PATCH] D148903: [PGO] Avoid potential const_cast UB (NFC)

[Christian Ulmann via Phabricator via llvm-commits]

Dinistro added a comment.

Added a comment to the critical UB causing part. Again, while there might be a way to keep constness, it requires extended changes. Fixing UB should be done first, afterwards, we can think about refactorings that allow us to keep constness where possible.



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Comment at: llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp:840
   BasicBlock *InstrBB =
       isa<IndirectBrInst>(TI) ? nullptr : SplitCriticalEdge(TI, SuccNum);
   if (!InstrBB) {
----------------
This full function is shared between the instrumentation and the use pass. Keeping const will always result in UB, as the SplitCriticalEdge function will be called with `TI`, which should be of type `const Instruction *`.
I fail to see how a templated edge class would help in resolving this issue, could you elaborate @xur ?

I believe that splitting the logic between instrument and usage might help to reduce the complexity and push const in some places, but that requires extended changes to the algorithms. 


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https://reviews.llvm.org/D148903