[VPlan] Use VPlan::getRegion to shorten code (NFC) (#164287)

Author: artagnon

llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp

@@ -2092,8 +2092,8 @@ struct VPCSEDenseMapInfo : public DenseMapInfo<VPSingleDefRecipe *> {
     // Recipes in replicate regions implicitly depend on predicate. If either
     // recipe is in a replicate region, only consider them equal if both have
     // the same parent.
-    const VPRegionBlock *RegionL = L->getParent()->getParent();
-    const VPRegionBlock *RegionR = R->getParent()->getParent();
+    const VPRegionBlock *RegionL = L->getRegion();
+    const VPRegionBlock *RegionR = R->getRegion();
     if (((RegionL && RegionL->isReplicator()) ||
          (RegionR && RegionR->isReplicator())) &&
         L->getParent() != R->getParent())
@@ -3867,8 +3867,7 @@ void VPlanTransforms::materializePacksAndUnpacks(VPlan &Plan) {
         // required lanes implicitly.
         // TODO: Remove once replicate regions are unrolled completely.
         auto IsCandidateUnpackUser = [Def](VPUser *U) {
-          VPRegionBlock *ParentRegion =
-              cast<VPRecipeBase>(U)->getParent()->getParent();
+          VPRegionBlock *ParentRegion = cast<VPRecipeBase>(U)->getRegion();
           return U->usesScalars(Def) &&
                  (!ParentRegion || !ParentRegion->isReplicator());
         };