[PATCH] D98422: [Alias] Add a ah-hoc pattern with two PHI for isKnownNonEqual

[Nikita Popov via Phabricator via llvm-commits]

nikic added a comment.

Can you please add tests for this functionality in llvm/test/Analysis/ValueTracking/known-non-equal.ll? These are simpler than going through BasicAA.



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Comment at: llvm/lib/Analysis/ValueTracking.cpp:2548
+      // to the PHI's block.
+      if (Q.DT->dominates(PN1->getParent(), Pred)) {
+        // loop:
----------------
I don't understand why this code is needed. For your example you are comparing `%cmp.0` and `%mul = mul nsw i32 %cmp.0, 2`, which should already be recognized as non-equal. What is this backedge check for?


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Comment at: llvm/lib/Analysis/ValueTracking.cpp:2553
+        //   ...
+        //   %inc = add i32 %cmp.0, 1
+        //   br label %loop
----------------
`%inc` is not used in the phi nodes, so it's not clear what the relation is. Maybe you meant to replace `%mul` with `%inc`?


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