[llvm] [VPlan] Implement VPReductionRecipe::computeCost(). NFC (PR #107790)

[Florian Hahn via llvm-commits]

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@@ -1897,6 +1897,30 @@ void VPReductionEVLRecipe::execute(VPTransformState &State) {
   State.set(this, NewRed, 0, /*IsScalar*/ true);
 }
 
+InstructionCost VPReductionRecipe::computeCost(ElementCount VF,
+                                               VPCostContext &Ctx) const {
+  RecurKind RdxKind = RdxDesc.getRecurrenceKind();
+  Type *ElementTy = RdxDesc.getRecurrenceType();
+  auto *VectorTy = dyn_cast<VectorType>(ToVectorTy(ElementTy, VF));
+  TTI::TargetCostKind CostKind = TTI::TCK_RecipThroughput;
+  unsigned Opcode = RdxDesc.getOpcode();
+
+  if (VectorTy == nullptr)
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fhahn wrote:

 That's a bit surprising, do you know under which conditions that may happen?


https://github.com/llvm/llvm-project/pull/107790