diff --git a/llvm/lib/Target/RISCV/RISCVTargetTransformInfo.h b/llvm/lib/Target/RISCV/RISCVTargetTransformInfo.h
--- a/llvm/lib/Target/RISCV/RISCVTargetTransformInfo.h
+++ b/llvm/lib/Target/RISCV/RISCVTargetTransformInfo.h
@@ -112,6 +112,11 @@
                                              Optional<FastMathFlags> FMF,
                                              TTI::TargetCostKind CostKind);
 
+  InstructionCost getExtendedReductionCost(unsigned Opcode, bool IsUnsigned,
+                                           Type *ResTy, VectorType *ValTy,
+                                           Optional<FastMathFlags> FMF,
+                                           TTI::TargetCostKind CostKind);
+
   bool isElementTypeLegalForScalableVector(Type *Ty) const {
     return TLI->isLegalElementTypeForRVV(Ty);
   }
diff --git a/llvm/lib/Target/RISCV/RISCVTargetTransformInfo.cpp b/llvm/lib/Target/RISCV/RISCVTargetTransformInfo.cpp
--- a/llvm/lib/Target/RISCV/RISCVTargetTransformInfo.cpp
+++ b/llvm/lib/Target/RISCV/RISCVTargetTransformInfo.cpp
@@ -377,6 +377,43 @@
   return (LT.first - 1) + BaseCost + Log2_32_Ceil(VL);
 }
 
+InstructionCost RISCVTTIImpl::getExtendedReductionCost(
+    unsigned Opcode, bool IsUnsigned, Type *ResTy, VectorType *ValTy,
+    Optional<FastMathFlags> FMF, TTI::TargetCostKind CostKind) {
+  if (isa<FixedVectorType>(ValTy) && !ST->useRVVForFixedLengthVectors())
+    return BaseT::getExtendedReductionCost(Opcode, IsUnsigned, ResTy, ValTy,
+                                           FMF, CostKind);
+
+  // Skip if scalar size of ResTy is bigger than ELEN.
+  if (ResTy->getScalarSizeInBits() > ST->getELEN())
+    return BaseT::getExtendedReductionCost(Opcode, IsUnsigned, ResTy, ValTy,
+                                           FMF, CostKind);
+
+  int ISD = TLI->InstructionOpcodeToISD(Opcode);
+  assert(ISD && "Invalid opcode");
+
+  std::pair<InstructionCost, MVT> LT = TLI->getTypeLegalizationCost(DL, ValTy);
+
+  switch (ISD) {
+  case ISD::ADD:
+    if (ResTy->getScalarSizeInBits() == 2 * LT.second.getScalarSizeInBits())
+      // vwredsum and vwredsumu.
+      return (LT.first - 1) +
+             getArithmeticReductionCost(Instruction::Add, ValTy, FMF, CostKind);
+    break;
+  case ISD::FADD:
+    if (ResTy->getScalarSizeInBits() == 2 * LT.second.getScalarSizeInBits())
+      // vfwredosum and vfwredusum.
+      return (LT.first - 1) + getArithmeticReductionCost(Instruction::FAdd,
+                                                         ValTy, FMF, CostKind);
+    break;
+  default:
+    break;
+  }
+  return BaseT::getExtendedReductionCost(Opcode, IsUnsigned, ResTy, ValTy, FMF,
+                                         CostKind);
+}
+
 void RISCVTTIImpl::getUnrollingPreferences(Loop *L, ScalarEvolution &SE,
                                            TTI::UnrollingPreferences &UP,
                                            OptimizationRemarkEmitter *ORE) {