[llvm] [VPlan] Return partial reduction cost only for VPPartialReductionRecipe (NFC) (PR #167846)

[Florian Hahn via llvm-commits]

https://github.com/fhahn updated https://github.com/llvm/llvm-project/pull/167846

>From e37535fe7d2bfa210f42ea550d622be657669c13 Mon Sep 17 00:00:00 2001
From: Florian Hahn <flo at fhahn.com>
Date: Thu, 13 Nov 2025 08:27:21 +0000
Subject: [PATCH] [VPlan] Return partial reduction cost only for
 VPPartialReductionRecipe (NFC)

Now that the cost of extends/multiplies with partial reductions is
accounted for in VPExpression recipes,
VPPartialReductionRecipe::computeCost and just return the cost of the
partial reduction intrinsic, without accounting for any casts.
---
 .../lib/Transforms/Vectorize/VPlanRecipes.cpp | 93 +------------------
 1 file changed, 5 insertions(+), 88 deletions(-)

diff --git a/llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp b/llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp
index fca6554ad77c6..2bad1d0cea62c 100644
--- a/llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp
+++ b/llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp
@@ -307,94 +307,11 @@ bool VPRecipeBase::isScalarCast() const {
 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);
-  }
-
-  // If the partial reduction is predicated, a select will be operand 1.
-  // If it isn't predicated and the mul isn't operating on a constant, then it
-  // should have been turned into a VPExpressionRecipe.
-  // FIXME: Replace the entire function with this once all partial reduction
-  // variants are bundled into VPExpressionRecipe.
-  if (!match(Op, m_Mul(m_VPValue(), m_ConstantInt(MulConst)))) {
-    auto *PhiType = Ctx.Types.inferScalarType(getChainOp());
-    auto *InputType = Ctx.Types.inferScalarType(getVecOp());
-    return CondCost + Ctx.TTI.getPartialReductionCost(
-                          getOpcode(), InputType, InputType, PhiType, VF,
-                          TTI::PR_None, TTI::PR_None, {}, Ctx.CostKind);
-  }
-
-  VPRecipeBase *OpR = Op->getDefiningRecipe();
-  Type *InputTypeA = nullptr, *InputTypeB = nullptr;
-  TTI::PartialReductionExtendKind ExtAType = TTI::PR_None,
-                                  ExtBType = TTI::PR_None;
-
-  auto GetExtendKind = [](VPRecipeBase *R) {
-    if (!R)
-      return TTI::PR_None;
-    auto *WidenCastR = dyn_cast<VPWidenCastRecipe>(R);
-    if (!WidenCastR)
-      return TTI::PR_None;
-    if (WidenCastR->getOpcode() == Instruction::CastOps::ZExt)
-      return TTI::PR_ZeroExtend;
-    if (WidenCastR->getOpcode() == Instruction::CastOps::SExt)
-      return TTI::PR_SignExtend;
-    return TTI::PR_None;
-  };
-
-  // Pick out opcode, type/ext information and use sub side effects from a widen
-  // recipe.
-  auto HandleWiden = [&](VPWidenRecipe *Widen) {
-    if (match(Widen, m_Sub(m_ZeroInt(), m_VPValue(Op)))) {
-      Widen = dyn_cast<VPWidenRecipe>(Op);
-    }
-    Opcode = Widen->getOpcode();
-    VPRecipeBase *ExtAR = Widen->getOperand(0)->getDefiningRecipe();
-    VPRecipeBase *ExtBR = Widen->getOperand(1)->getDefiningRecipe();
-    InputTypeA = Ctx.Types.inferScalarType(ExtAR ? ExtAR->getOperand(0)
-                                                 : Widen->getOperand(0));
-    InputTypeB = Ctx.Types.inferScalarType(ExtBR ? ExtBR->getOperand(0)
-                                                 : Widen->getOperand(1));
-    ExtAType = GetExtendKind(ExtAR);
-    ExtBType = GetExtendKind(ExtBR);
-
-    using namespace VPlanPatternMatch;
-    const APInt *C;
-    if (!ExtBR && match(Widen->getOperand(1), m_APInt(C)) &&
-        canConstantBeExtended(C, InputTypeA, ExtAType)) {
-      InputTypeB = InputTypeA;
-      ExtBType = ExtAType;
-    }
-  };
-
-  if (isa<VPWidenCastRecipe>(OpR)) {
-    InputTypeA = Ctx.Types.inferScalarType(OpR->getOperand(0));
-    ExtAType = GetExtendKind(OpR);
-  } else if (isa<VPReductionPHIRecipe>(OpR)) {
-    if (auto RedPhiOp1R = dyn_cast_or_null<VPWidenCastRecipe>(getOperand(1))) {
-      InputTypeA = Ctx.Types.inferScalarType(RedPhiOp1R->getOperand(0));
-      ExtAType = GetExtendKind(RedPhiOp1R);
-    } else if (auto Widen = dyn_cast_or_null<VPWidenRecipe>(getOperand(1)))
-      HandleWiden(Widen);
-  } else if (auto Widen = dyn_cast<VPWidenRecipe>(OpR)) {
-    HandleWiden(Widen);
-  } else if (auto Reduction = dyn_cast<VPPartialReductionRecipe>(OpR)) {
-    return CondCost + Reduction->computeCost(VF, Ctx);
-  }
-  auto *PhiType = Ctx.Types.inferScalarType(getOperand(1));
-  return CondCost + Ctx.TTI.getPartialReductionCost(
-                        getOpcode(), InputTypeA, InputTypeB, PhiType, VF,
-                        ExtAType, ExtBType, Opcode, Ctx.CostKind);
-  ;
+  auto *PhiType = Ctx.Types.inferScalarType(getChainOp());
+  auto *InputType = Ctx.Types.inferScalarType(getVecOp());
+  return Ctx.TTI.getPartialReductionCost(getOpcode(), InputType, InputType,
+                                         PhiType, VF, TTI::PR_None,
+                                         TTI::PR_None, {}, Ctx.CostKind);
 }
 
 void VPPartialReductionRecipe::execute(VPTransformState &State) {