[llvm] [VPlan] Add initial VPScalarEvolution, use to get trip count SCEV (NFC) (PR #94464)

[Florian Hahn via llvm-commits]

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@@ -683,10 +683,9 @@ void VPlanTransforms::optimizeForVFAndUF(VPlan &Plan, ElementCount BestVF,
              m_BranchOnCond(m_Not(m_ActiveLaneMask(m_VPValue(), m_VPValue())))))
     return;
 
-  Type *IdxTy =
-      Plan.getCanonicalIV()->getStartValue()->getLiveInIRValue()->getType();
-  const SCEV *TripCount = createTripCountSCEV(IdxTy, PSE);
   ScalarEvolution &SE = *PSE.getSE();
+  const SCEV *TripCount =
+      vputils::getSCEVExprForVPValue(Plan.getTripCount(), SE);
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fhahn wrote:

Yes, will also entail to remove the region and header phis.

https://github.com/llvm/llvm-project/pull/94464