[llvm] [LV] Use VPReductionRecipe for partial reductions (PR #147513)

[Florian Hahn via llvm-commits]

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@@ -304,134 +303,6 @@ bool VPRecipeBase::isScalarCast() const {
   return VPI && Instruction::isCast(VPI->getOpcode());
 }
 
-InstructionCost
-VPPartialReductionRecipe::computeCost(ElementCount VF,
-                                      VPCostContext &Ctx) const {
-  std::optional<unsigned> Opcode;
-  VPValue *Op = getVecOp();
-  uint64_t MulConst;
-
-  InstructionCost CondCost = 0;
-  if (isConditional()) {
-    CmpInst::Predicate Pred = CmpInst::BAD_ICMP_PREDICATE;
-    auto *VecTy = Ctx.Types.inferScalarType(Op);
-    auto *CondTy = Ctx.Types.inferScalarType(getCondOp());
-    CondCost = Ctx.TTI.getCmpSelInstrCost(Instruction::Select, VecTy, CondTy,
-                                          Pred, Ctx.CostKind);
-  }
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fhahn wrote:

Oh that’s surprising, are we forming partial reductions for those cases? If not than it would be good to check first why the behavior changed, because that would be somewhat unexpected. I think we also have the predicate cost on main, but maybe the difference would be that after moving we may already have and pass the correct vector types?

https://github.com/llvm/llvm-project/pull/147513