[PATCH] D157062: [ValueTracking] Improve the coverage of isKnownToBeAPowerOfTwo for vscale

[Nikita Popov via Phabricator via llvm-commits]

nikic added reviewers: nikic, goldstein.w.n.
nikic added inline comments.
Herald added a subscriber: StephenFan.


================
Comment at: llvm/lib/Analysis/ValueTracking.cpp:2022
+  if (Q.CxtI &&
+      (match(V, m_VScale()) || match(V, m_Shl(m_VScale(), m_Value())))) {
     const Function *F = Q.CxtI->getFunction();
----------------
This isn't correct. A shift left of vscale can be zero if all bits get shifted out. There is no special interaction between vscale and shl.


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  https://reviews.llvm.org/D157062/new/

https://reviews.llvm.org/D157062