Revert "[RISCV] Refine cost on Min/Max reduction (#79402)"

This reverts commit 2800448.

llvm/lib/Target/RISCV/RISCVTargetTransformInfo.cpp

@@ -970,42 +970,13 @@ RISCVTTIImpl::getMinMaxReductionCost(Intrinsic::ID IID, VectorType *Ty,
   }
 
   // IR Reduction is composed by two vmv and one rvv reduction instruction.
-  unsigned SplitOp;
-  SmallVector<unsigned, 3> Opcodes;
-  switch (IID) {
-  default:
-    llvm_unreachable("Unsupported intrinsic");
-  case Intrinsic::smax:
-    SplitOp = RISCV::VMAX_VV;
-    Opcodes = {RISCV::VMV_S_X, RISCV::VREDMAX_VS, RISCV::VMV_X_S};
-    break;
-  case Intrinsic::smin:
-    SplitOp = RISCV::VMIN_VV;
-    Opcodes = {RISCV::VMV_S_X, RISCV::VREDMIN_VS, RISCV::VMV_X_S};
-    break;
-  case Intrinsic::umax:
-    SplitOp = RISCV::VMAXU_VV;
-    Opcodes = {RISCV::VMV_S_X, RISCV::VREDMAXU_VS, RISCV::VMV_X_S};
-    break;
-  case Intrinsic::umin:
-    SplitOp = RISCV::VMINU_VV;
-    Opcodes = {RISCV::VMV_S_X, RISCV::VREDMINU_VS, RISCV::VMV_X_S};
-    break;
-  case Intrinsic::maxnum:
-    SplitOp = RISCV::VFMAX_VV;
-    Opcodes = {RISCV::VFMV_S_F, RISCV::VFREDMAX_VS, RISCV::VFMV_F_S};
-    break;
-  case Intrinsic::minnum:
-    SplitOp = RISCV::VFMIN_VV;
-    Opcodes = {RISCV::VFMV_S_F, RISCV::VFREDMIN_VS, RISCV::VFMV_F_S};
-    break;
-  }
-  // Add a cost for data larger than LMUL8
-  InstructionCost SplitCost =
-      (LT.first > 1) ? (LT.first - 1) *
-                           getRISCVInstructionCost(SplitOp, LT.second, CostKind)
-                     : 0;
-  return SplitCost + getRISCVInstructionCost(Opcodes, LT.second, CostKind);
+  InstructionCost BaseCost = 2;
+
+  if (CostKind == TTI::TCK_CodeSize)
+    return (LT.first - 1) + BaseCost;
+
+  unsigned VL = getEstimatedVLFor(Ty);
+  return (LT.first - 1) + BaseCost + Log2_32_Ceil(VL);
 }
 
 InstructionCost