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

[via llvm-commits]

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@@ -499,6 +494,10 @@ SmallVector<VPRegisterUsage, 8> llvm::calculateRegisterUsageForPlan(
     return TTICapture.getRegUsageForType(VectorType::get(Ty, VF));
   };
 
+  if (auto *CanIV = LoopRegion->getCanonicalIV())
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ayalz wrote:

When/Can CanIV be null / LoopRegion be a replicating one?

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