[PATCH] D108848: [LoopDeletion] Separate logic in breakBackedgeIfNotTaken using symboic max trip count [nfc]

[Philip Reames via Phabricator via llvm-commits]

reames added a comment.

Well, it turns out the answer is that I'm a bloody idiot.  The code is definitely wrong, not sure why I didn't notice this before.

The issue is that we use isKnownNonZero to filter the canProveOnFirstIteration call.  This filtering depends on a *lower bound* of the actual trip count.  My change passed an *upper bound*.  That results in us failing to call canProveOnFirstIteration for cases we can prove a loop exit is taken.

Working on a fix now.  May end up just reverting depending on whether the fix is reasonable clean on the newer code or not.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D108848/new/

https://reviews.llvm.org/D108848