[PATCH] D101722: [SCEV] Don't require ControlsExit for gt/lt NoWrap

[Philip Reames via Phabricator via llvm-commits]

reames added a comment.

@nikic I'm increasingly thinking that the computeBECount logic is just wrong.  I believe you can trip the overflow to zero case with a loop with explicit (correct) flags.  There's some comments and a guard on negative steps which appear incorrect, and I'm guessing were an attempt to work around an existing bug.

I think we need to change the computeBECount function to correctly compute the trip count for the overflowing (computation) case, but doing that "cheap enough" has has me slightly stuck.  I was hoping to get a patch up for this in the next day or two once I had some time to sit down and focus on that aspect.


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D101722/new/

https://reviews.llvm.org/D101722