[PATCH] D157292: [ValueTracking] Fix the correct of isKnownToBeAPowerOfTwo

[Allen zhong via Phabricator via llvm-commits]

Allen created this revision.
Allen added reviewers: goldstein.w.n, nikic.
Herald added subscribers: StephenFan, hiraditya.
Herald added a project: All.
Allen requested review of this revision.
Herald added a project: LLVM.
Herald added a subscriber: llvm-commits.

https://reviews.llvm.org/D157292

Files:
  llvm/lib/Analysis/ValueTracking.cpp


Index: llvm/lib/Analysis/ValueTracking.cpp
===================================================================
--- llvm/lib/Analysis/ValueTracking.cpp
+++ llvm/lib/Analysis/ValueTracking.cpp
@@ -2018,13 +2018,27 @@
       return true;
   if (match(V, m_Power2()))
       return true;
-  if (Q.CxtI &&
-      (match(V, m_VScale()) || match(V, m_Shl(m_VScale(), m_Value())))) {
+  if (Q.CxtI && match(V, m_VScale())) {
     const Function *F = Q.CxtI->getFunction();
     // The vscale_range indicates vscale is a power-of-two.
     return F->hasFnAttribute(Attribute::VScaleRange);
   }
 
+  const APInt *Shift;
+  if (Q.CxtI && match(V, m_Shl(m_VScale(), m_APInt(Shift)))) {
+    const Function *F = Q.CxtI->getFunction();
+    // The vscale_range indicates vscale is a power-of-two.
+    if (F->hasFnAttribute(Attribute::VScaleRange)) {
+      Attribute Attr = F->getFnAttribute(Attribute::VScaleRange);
+      if (std::optional<unsigned> MaxVScale = Attr.getVScaleRangeMax()) {
+        unsigned Bitwidth = V->getType()->getScalarSizeInBits();
+		// Make sure the value don't get shifted out
+        if (Log2_32(*MaxVScale) + Shift->getZExtValue() < Bitwidth)
+          return true;
+      }
+    }
+  }
+
   // 1 << X is clearly a power of two if the one is not shifted off the end.  If
   // it is shifted off the end then the result is undefined.
   if (match(V, m_Shl(m_One(), m_Value())))


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