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

[Allen zhong via Phabricator via llvm-commits]

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this PR tries to match the following pattern, seperate from D156881 <https://reviews.llvm.org/D156881>

  %vscale = call i64 @llvm.vscale.i64()
  %shift = shl nuw nsw i64 %vscale, 11


Now, we only check the shl recursively when the OrZero is true.


https://reviews.llvm.org/D157062

Files:
  llvm/lib/Analysis/ValueTracking.cpp


Index: llvm/lib/Analysis/ValueTracking.cpp
===================================================================
--- llvm/lib/Analysis/ValueTracking.cpp
+++ llvm/lib/Analysis/ValueTracking.cpp
@@ -2018,7 +2018,8 @@
       return true;
   if (match(V, m_Power2()))
       return true;
-  if (Q.CxtI && match(V, m_VScale())) {
+  if (Q.CxtI &&
+      (match(V, m_VScale()) || match(V, m_Shl(m_VScale(), m_Value())))) {
     const Function *F = Q.CxtI->getFunction();
     // The vscale_range indicates vscale is a power-of-two.
     return F->hasFnAttribute(Attribute::VScaleRange);


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