[PATCH] D132450: StructurizeCFG: Set Undef for non-predecessors in setPhiValues()

[Sameer Sahasrabuddhe via Phabricator via llvm-commits]

sameerds added inline comments.


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Comment at: llvm/lib/Transforms/Scalar/StructurizeCFG.cpp:687-689
+              // If this is not flow node and not the incoming block before
+              // structurization, then this block does not contribute any value
+              // to the phi.
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This is the core idea. But it's not obvious how the code implements this. Would be good to have an explanation of the Stack and the Incomings set. For example, why do we need to erase Current from Incomings? Somewhere in the traversal, the Stack seems to ensure that undefs are added to phis at intermediate Flow blocks ... needs explanation of why it always works.


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  https://reviews.llvm.org/D132450/new/

https://reviews.llvm.org/D132450