[llvm] [VPlan] Make canonical IV part of the region (PR #156262)

[via llvm-commits]

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@@ -9552,6 +9548,7 @@ static SmallVector<Instruction *> preparePlanForEpilogueVectorLoop(
     EPI.VectorTripCount = EPResumeVal->getOperand(0);
   }
   VPValue *VPV = Plan.getOrAddLiveIn(EPResumeVal);
+  VPValue *IV = VectorLoop->getCanonicalIV();
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ayalz wrote:

This replaces an `if (auto *IV = dyn_cast...`

https://github.com/llvm/llvm-project/pull/156262