[PATCH] D88460: Strlen loop idiom recognition

Wed Oct 7 15:38:04 PDT 2020

efriedma added inline comments.

================
Comment at: llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp:1691
+  }
+  if (!ResInst)
+    return false;
----------------
anjankgk wrote:
> 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?
How do you know it's a sub instruction?

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

https://reviews.llvm.org/D88460