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

[via llvm-commits]

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@@ -8455,6 +8454,7 @@ VPlanPtr LoopVectorizationPlanner::tryToBuildVPlanWithVPRecipes(
                             m_Specific(Plan->getCanonicalIV()), m_VPValue())) &&
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ayalz wrote:

Above is another instance which could use `Plan->getCanonicalIVInv()`, possibly as a first step towards turning it into a region value.

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