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

[via llvm-commits]

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@@ -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();
+  }
+  auto CheckEVLRecipiesInsts = [&](const VPRecipeBase *R) {
+    if (isa<VPEVLBasedIVPHIRecipe>(R)) {
+      if (!Header || VPBB != Header) {
+        errs() << "EVL PHI recipe not in entry block!\n";
+        return false;
+      }
+      if (EVLFound.contains(VPDef::VPEVLBasedIVPHISC)) {
+        errs() << "EVL PHI recipe inserted more than once!\n";
+        return false;
+      }
+      EVLFound.insert(VPDef::VPEVLBasedIVPHISC);
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ayalz wrote:

The contains() can be folded to check the result of insert(), to search once instead of twice.

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