[PATCH] D62990: [SCEV]When safe, compute MinStart as unsigned_min(Start - Stride) + Stride in computeMaxBECountForLT

[Philip Reames via Phabricator via llvm-commits]

reames added a comment.

I may be missing the obvious, but the code as written appears to be assuming the post-increment form of the induction variable is passed in, not the pre-increment form.  What ensures that?

If I'm reading this right, you're basically trying to get a more specific range for Start, using the fact proved by the loop entry guard right?  I've seen such cases come up several times recently in things I've worked on, maybe it's time to add a getUnsignedRangeAtScope(SCEV, Loop) variant?  (Just as we have a getSCEVAtScope)


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  rL LLVM

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https://reviews.llvm.org/D62990