Update comment, use VPCostContext CostKind

Author: lukel97

llvm/lib/Transforms/Vectorize/LoopVectorize.cpp

@@ -5108,8 +5108,8 @@ InstructionCost LoopVectorizationCostModel::expectedCost(ElementCount VF) {
     // unconditionally executed. For the scalar case, we may not always execute
     // the predicated block, if it is an if-else block. Thus, scale the block's
     // cost by the probability of executing it.
-    // getPredBlockCostDivisor won't include blocks that are only predicated due
-    // to tail folded loops
+    // getPredBlockCostDivisor will return 1 for blocks that are only predicated
+    // by the header mask when folding the tail.
     if (VF.isScalar())
       BlockCost /= getPredBlockCostDivisor(CostKind, BB);
 
@@ -6758,8 +6758,7 @@ bool VPCostContext::skipCostComputation(Instruction *UI, bool IsVector) const {
          SkipCostComputation.contains(UI);
 }
 
-unsigned VPCostContext::getPredBlockCostDivisor(
-    TargetTransformInfo::TargetCostKind CostKind, BasicBlock *BB) const {
+unsigned VPCostContext::getPredBlockCostDivisor(BasicBlock *BB) const {
   return CM.getPredBlockCostDivisor(CostKind, BB);
 }
 

llvm/lib/Transforms/Vectorize/VPlanHelpers.h

@@ -354,8 +354,7 @@ struct VPCostContext {
 
   /// \returns how much the cost of a predicated block should be divided by.
   /// Forwards to LoopVectorizationCostModel::getPredBlockCostDivisor.
-  unsigned getPredBlockCostDivisor(TargetTransformInfo::TargetCostKind CostKind,
-                                   BasicBlock *BB) const;
+  unsigned getPredBlockCostDivisor(BasicBlock *BB) const;
 
   /// Returns the OperandInfo for \p V, if it is a live-in.
   TargetTransformInfo::OperandValueInfo getOperandInfo(VPValue *V) const;

llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp

@@ -3349,7 +3349,7 @@ InstructionCost VPReplicateRecipe::computeCost(ElementCount VF,
     // Scale the cost by the probability of executing the predicated blocks.
     // This assumes the predicated block for each vector lane is equally
     // likely.
-    ScalarCost /= Ctx.getPredBlockCostDivisor(Ctx.CostKind, UI->getParent());
+    ScalarCost /= Ctx.getPredBlockCostDivisor(UI->getParent());
     return ScalarCost;
   }
   case Instruction::Load: