[ARM] Basic getArithmeticReductionCost reduction costs

This adds some basic costs for MVE reductions - currently just costing
the simple legal add vectors as a single MVE instruction. More complex
costing can be added in the future when the framework more readily
allows it.

Differential Revision: https://reviews.llvm.org/D88980

Author: davemgreen

llvm/lib/Target/ARM/ARMTargetTransformInfo.cpp

@@ -20,6 +20,7 @@
 #include "llvm/IR/DerivedTypes.h"
 #include "llvm/IR/Instruction.h"
 #include "llvm/IR/Instructions.h"
+#include "llvm/IR/Intrinsics.h"
 #include "llvm/IR/IntrinsicInst.h"
 #include "llvm/IR/IntrinsicsARM.h"
 #include "llvm/IR/PatternMatch.h"
@@ -1409,6 +1410,29 @@ unsigned ARMTTIImpl::getGatherScatterOpCost(unsigned Opcode, Type *DataTy,
   return ScalarCost;
 }
 
+int ARMTTIImpl::getArithmeticReductionCost(unsigned Opcode, VectorType *ValTy,
+                                           bool IsPairwiseForm,
+                                           TTI::TargetCostKind CostKind) {
+  EVT ValVT = TLI->getValueType(DL, ValTy);
+  int ISD = TLI->InstructionOpcodeToISD(Opcode);
+  if (!ST->hasMVEIntegerOps() || !ValVT.isSimple() || ISD != ISD::ADD)
+    return BaseT::getArithmeticReductionCost(Opcode, ValTy, IsPairwiseForm,
+                                             CostKind);
+
+  std::pair<int, MVT> LT = TLI->getTypeLegalizationCost(DL, ValTy);
+
+  static const CostTblEntry CostTblAdd[]{
+      {ISD::ADD, MVT::v16i8, 1},
+      {ISD::ADD, MVT::v8i16, 1},
+      {ISD::ADD, MVT::v4i32, 1},
+  };
+  if (const auto *Entry = CostTableLookup(CostTblAdd, ISD, LT.second))
+    return Entry->Cost * ST->getMVEVectorCostFactor() * LT.first;
+
+  return BaseT::getArithmeticReductionCost(Opcode, ValTy, IsPairwiseForm,
+                                           CostKind);
+}
+
 int ARMTTIImpl::getIntrinsicInstrCost(const IntrinsicCostAttributes &ICA,
                                       TTI::TargetCostKind CostKind) {
   // Currently we make a somewhat optimistic assumption that active_lane_mask's

llvm/lib/Target/ARM/ARMTargetTransformInfo.h

@@ -247,6 +247,10 @@ class ARMTTIImpl : public BasicTTIImplBase<ARMTTIImpl> {
                                   Align Alignment, TTI::TargetCostKind CostKind,
                                   const Instruction *I = nullptr);
 
+  int getArithmeticReductionCost(unsigned Opcode, VectorType *ValTy,
+                                 bool IsPairwiseForm,
+                                 TTI::TargetCostKind CostKind);
+
   int getIntrinsicInstrCost(const IntrinsicCostAttributes &ICA,
                             TTI::TargetCostKind CostKind);