[PATCH] D88460: Strlen loop idiom recognition

Wed Oct 7 15:31:41 PDT 2020

anjankgk added inline comments.

================
Comment at: llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp:1691
+  }
+  if (!ResInst)
+    return false;
----------------
efriedma wrote:
> anjankgk wrote:
> > efriedma wrote:
> > > I'm not sure how ResInst is connected to the rest of this transform; why are we transforming the operand of some random PHI node?
> > I added a comment for clarity - 
> >   // Finally, we find the phi node that corresponds to the distance between the
> >   // pointers and replace it's uses by the call to strlen in the transformed
> >   // code.
> > 
> The patch doesn't appear to prove that anywhere.
I am getting the `sub` instruction saved in ResInst and replacing that in line# 1689. Is that something that you prefer to be done in a different way?

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  https://reviews.llvm.org/D88460/new/

https://reviews.llvm.org/D88460