[VPlan] Handle VPIRPhi in VPRecipeBase::isPhi (NFC).

Also handle VPIRPhi in VPRecipeBase::isPhi, to simplify existing code
dealing with VPIRPhis.

Suggested as part of #136455.

Author: fhahn

llvm/lib/Transforms/Vectorize/LoopVectorize.cpp

@@ -9324,10 +9324,8 @@ static void addScalarResumePhis(VPRecipeBuilder &Builder, VPlan &Plan,
   VPBuilder ScalarPHBuilder(ScalarPH);
   VPValue *OneVPV = Plan.getOrAddLiveIn(
       ConstantInt::get(Plan.getCanonicalIV()->getScalarType(), 1));
-  for (VPRecipeBase &ScalarPhiR : *Plan.getScalarHeader()) {
-    auto *ScalarPhiIRI = dyn_cast<VPIRPhi>(&ScalarPhiR);
-    if (!ScalarPhiIRI)
-      break;
+  for (VPRecipeBase &ScalarPhiR : Plan.getScalarHeader()->phis()) {
+    auto *ScalarPhiIRI = cast<VPIRPhi>(&ScalarPhiR);
 
     // TODO: Extract final value from induction recipe initially, optimize to
     // pre-computed end value together in optimizeInductionExitUsers.
@@ -9381,10 +9379,8 @@ collectUsersInExitBlocks(Loop *OrigLoop, VPRecipeBuilder &Builder,
     if (ExitVPBB->getNumPredecessors() == 0)
       continue;
 
-    for (VPRecipeBase &R : *ExitVPBB) {
-      auto *ExitIRI = dyn_cast<VPIRPhi>(&R);
-      if (!ExitIRI)
-        break;
+    for (VPRecipeBase &R : ExitVPBB->phis()) {
+      auto *ExitIRI = cast<VPIRPhi>(&R);
       if (ExitVPBB->getSinglePredecessor() != Plan.getMiddleBlock()) {
         assert(ExitIRI->getNumOperands() ==
                    ExitVPBB->getPredecessors().size() &&
@@ -10579,10 +10575,9 @@ static void preparePlanForMainVectorLoop(VPlan &MainPlan, VPlan &EpiPlan) {
     EpiWidenedPhis.insert(
         cast<PHINode>(R.getVPSingleValue()->getUnderlyingValue()));
   }
-  for (VPRecipeBase &R : make_early_inc_range(*MainPlan.getScalarHeader())) {
-    auto *VPIRInst = dyn_cast<VPIRPhi>(&R);
-    if (!VPIRInst)
-      break;
+  for (VPRecipeBase &R :
+       make_early_inc_range(MainPlan.getScalarHeader()->phis())) {
+    auto *VPIRInst = cast<VPIRPhi>(&R);
     if (EpiWidenedPhis.contains(&VPIRInst->getIRPhi()))
       continue;
     // There is no corresponding wide induction in the epilogue plan that would

llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp

@@ -274,7 +274,8 @@ InstructionCost VPRecipeBase::computeCost(ElementCount VF,
 bool VPRecipeBase::isPhi() const {
   return (getVPDefID() >= VPFirstPHISC && getVPDefID() <= VPLastPHISC) ||
          (isa<VPInstruction>(this) &&
-          cast<VPInstruction>(this)->getOpcode() == Instruction::PHI);
+          cast<VPInstruction>(this)->getOpcode() == Instruction::PHI) ||
+         isa<VPIRPhi>(this);
 }
 
 bool VPRecipeBase::isScalarCast() const {

llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp

@@ -874,10 +874,8 @@ void VPlanTransforms::optimizeInductionExitUsers(
   VPBlockBase *MiddleVPBB = Plan.getMiddleBlock();
   VPTypeAnalysis TypeInfo(Plan.getCanonicalIV()->getScalarType());
   for (VPIRBasicBlock *ExitVPBB : Plan.getExitBlocks()) {
-    for (VPRecipeBase &R : *ExitVPBB) {
-      auto *ExitIRI = dyn_cast<VPIRPhi>(&R);
-      if (!ExitIRI)
-        break;
+    for (VPRecipeBase &R : ExitVPBB->phis()) {
+      auto *ExitIRI = cast<VPIRPhi>(&R);
 
       for (auto [Idx, PredVPBB] : enumerate(ExitVPBB->getPredecessors())) {
         VPValue *Escape = nullptr;
@@ -2505,11 +2503,8 @@ void VPlanTransforms::handleUncountableEarlyExit(
   // Update the exit phis in the early exit block.
   VPBuilder MiddleBuilder(NewMiddle);
   VPBuilder EarlyExitB(VectorEarlyExitVPBB);
-  for (VPRecipeBase &R : *VPEarlyExitBlock) {
-    auto *ExitIRI = dyn_cast<VPIRPhi>(&R);
-    if (!ExitIRI)
-      break;
-
+  for (VPRecipeBase &R : VPEarlyExitBlock->phis()) {
+    auto *ExitIRI = cast<VPIRPhi>(&R);
     PHINode &ExitPhi = ExitIRI->getIRPhi();
     VPValue *IncomingFromEarlyExit = RecipeBuilder.getVPValueOrAddLiveIn(
         ExitPhi.getIncomingValueForBlock(UncountableExitingBlock));