[llvm] [LV, VP]VP intrinsics support for the Loop Vectorizer + adding new tail-folding mode using EVL. (PR #76172)

[via llvm-commits]

================
@@ -202,7 +202,58 @@ static bool verifyVPBasicBlock(const VPBasicBlock *VPBB,
   for (const VPRecipeBase &R : *VPBB)
     RecipeNumbering[&R] = Cnt++;
 
+  // Check if EVL recipes exist only in Entry block and only once.
+  DenseSet<unsigned> EVLFound;
+  const VPBlockBase *Header = nullptr;
+  const VPBlockBase *Exit = nullptr;
+  const VPlan *Plan = VPBB->getPlan();
+  if (Plan && Plan->getEntry()->getNumSuccessors() == 1) {
+    Header = Plan->getVectorLoopRegion()->getEntry();
+    Exit = Plan->getVectorLoopRegion()->getExiting();
+  }
----------------
ayalz wrote:

Suffice and clearer to indicate if VPBB `IsHeader` and/or `IsExiting`, by checking if its parent is a region whose entry and/or exit is VPBB?

https://github.com/llvm/llvm-project/pull/76172