[llvm] [VPlan] Allow tail folding with IVs with outside users (PR #182322)

[Andrei Elovikov via llvm-commits]

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@@ -2,11 +2,7 @@
 ; RUN: opt < %s -passes=loop-vectorize -force-vector-width=4 -force-vector-interleave=1 -S | FileCheck %s
 
 
-; The vectorizer should refuse to fold the tail by masking because
-; %conv is used outside of the loop. Test for this by checking that
-; %n.vec, the vector trip count, is rounded down to the next multiple of
-; 4. If folding the tail, it would have been rounded up instead.
-; Test case for #76069(https://github.com/llvm/llvm-project/issues/76069).
+; TODO: Move this test into tail-folding-iv-outside-user.ll
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eas wrote:

I think it would be better to move/copy it under `VPlan/` and check the dump after tail folding transformation, preferrably prior/as part of this PR.

https://github.com/llvm/llvm-project/pull/182322