[PATCH] D69617: [LoopUnroll] countToEliminateCompares(): fix handling of [in]equality predicates (PR43840)

[Roman Lebedev via Phabricator via llvm-commits]

lebedev.ri added inline comments.


================
Comment at: llvm/lib/Transforms/Utils/LoopUnrollPeel.cpp:267
+        SE.isKnownPredicate(Pred, NextIterVal, RightSCEV) &&
+        !SE.isKnownPredicate(ICmpInst::getInversePredicate(Pred), NextIterVal,
+                             RightSCEV)) {
----------------
fhahn wrote:
> I think we don't need to check the inverse predicate is known, when we already know the regular predicate is known, which is the previous check. Similarly, we already know know `SE.isKnownPredicate(ICmpInst::getInversePredicate(Pred), IterVal, RightSCEV)`, so we should not need to check `!SE.isKnownPredicate(Pred, IterVal, RightSCEV) `
> 
> It might be worth having those 2 as an assertion though, in case I am missing something.
This is indeed a mess.
I believe this is what you had in mind?


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  https://reviews.llvm.org/D69617/new/

https://reviews.llvm.org/D69617