Pick Vector Dotproduct improvements.

llvm/include/llvm/Analysis/TargetTransformInfo.h

@@ -213,6 +213,12 @@ typedef TargetTransformInfo TTI;
 /// for IR-level transformations.
 class TargetTransformInfo {
 public:
+  enum PartialReductionExtendKind { PR_None, PR_SignExtend, PR_ZeroExtend };
+
+  /// Get the kind of extension that an instruction represents.
+  static PartialReductionExtendKind
+  getPartialReductionExtendKind(Instruction *I);
+
   /// Construct a TTI object using a type implementing the \c Concept
   /// API below.
   ///
@@ -1257,6 +1263,20 @@ class TargetTransformInfo {
   /// \return if target want to issue a prefetch in address space \p AS.
   bool shouldPrefetchAddressSpace(unsigned AS) const;
 
+  /// \return The cost of a partial reduction, which is a reduction from a
+  /// vector to another vector with fewer elements of larger size. They are
+  /// represented by the llvm.experimental.partial.reduce.add intrinsic, which
+  /// takes an accumulator and a binary operation operand that itself is fed by
+  /// two extends. An example of an operation that uses a partial reduction is a
+  /// dot product, which reduces two vectors to another of 4 times fewer and 4
+  /// times larger elements.
+  InstructionCost
+  getPartialReductionCost(unsigned Opcode, Type *InputTypeA, Type *InputTypeB,
+                          Type *AccumType, ElementCount VF,
+                          PartialReductionExtendKind OpAExtend,
+                          PartialReductionExtendKind OpBExtend,
+                          std::optional<unsigned> BinOp = std::nullopt) const;
+
   /// \return The maximum interleave factor that any transform should try to
   /// perform for this target. This number depends on the level of parallelism
   /// and the number of execution units in the CPU.
@@ -2034,6 +2054,20 @@ class TargetTransformInfo::Concept {
   /// \return if target want to issue a prefetch in address space \p AS.
   virtual bool shouldPrefetchAddressSpace(unsigned AS) const = 0;
 
+  /// \return The cost of a partial reduction, which is a reduction from a
+  /// vector to another vector with fewer elements of larger size. They are
+  /// represented by the llvm.experimental.partial.reduce.add intrinsic, which
+  /// takes an accumulator and a binary operation operand that itself is fed by
+  /// two extends. An example of an operation that uses a partial reduction is a
+  /// dot product, which reduces two vectors to another of 4 times fewer and 4
+  /// times larger elements.
+  virtual InstructionCost
+  getPartialReductionCost(unsigned Opcode, Type *InputTypeA, Type *InputTypeB,
+                          Type *AccumType, ElementCount VF,
+                          PartialReductionExtendKind OpAExtend,
+                          PartialReductionExtendKind OpBExtend,
+                          std::optional<unsigned> BinOp) const = 0;
+
   virtual unsigned getMaxInterleaveFactor(ElementCount VF) = 0;
   virtual InstructionCost getArithmeticInstrCost(
       unsigned Opcode, Type *Ty, TTI::TargetCostKind CostKind,
@@ -2669,6 +2703,16 @@ class TargetTransformInfo::Model final : public TargetTransformInfo::Concept {
     return Impl.shouldPrefetchAddressSpace(AS);
   }
 
+  InstructionCost getPartialReductionCost(
+      unsigned Opcode, Type *InputTypeA, Type *InputTypeB, Type *AccumType,
+      ElementCount VF, PartialReductionExtendKind OpAExtend,
+      PartialReductionExtendKind OpBExtend,
+      std::optional<unsigned> BinOp = std::nullopt) const override {
+    return Impl.getPartialReductionCost(Opcode, InputTypeA, InputTypeB,
+                                        AccumType, VF, OpAExtend, OpBExtend,
+                                        BinOp);
+  }
+
   unsigned getMaxInterleaveFactor(ElementCount VF) override {
     return Impl.getMaxInterleaveFactor(VF);
   }

llvm/include/llvm/Analysis/TargetTransformInfoImpl.h

@@ -543,6 +543,15 @@ class TargetTransformInfoImplBase {
   bool enableWritePrefetching() const { return false; }
   bool shouldPrefetchAddressSpace(unsigned AS) const { return !AS; }
 
+  InstructionCost
+  getPartialReductionCost(unsigned Opcode, Type *InputTypeA, Type *InputTypeB,
+                          Type *AccumType, ElementCount VF,
+                          TTI::PartialReductionExtendKind OpAExtend,
+                          TTI::PartialReductionExtendKind OpBExtend,
+                          std::optional<unsigned> BinOp = std::nullopt) const {
+    return InstructionCost::getInvalid();
+  }
+
   unsigned getMaxInterleaveFactor(ElementCount VF) const { return 1; }
 
   InstructionCost getArithmeticInstrCost(

llvm/include/llvm/CodeGen/SelectionDAG.h

@@ -1587,6 +1587,11 @@ class SelectionDAG {
   /// the target's desired shift amount type.
   SDValue getShiftAmountOperand(EVT LHSTy, SDValue Op);
 
+  /// Create the DAG equivalent of vector_partial_reduce where Op1 and Op2 are
+  /// its operands and ReducedTY is the intrinsic's return type.
+  SDValue getPartialReduceAdd(SDLoc DL, EVT ReducedTy, SDValue Op1,
+                              SDValue Op2);
+
   /// Expand the specified \c ISD::VAARG node as the Legalize pass would.
   SDValue expandVAArg(SDNode *Node);
 

llvm/include/llvm/CodeGen/TargetLowering.h

@@ -454,6 +454,13 @@ class TargetLoweringBase {
     return true;
   }
 
+  /// Return true if the @llvm.experimental.vector.partial.reduce.* intrinsic
+  /// should be expanded using generic code in SelectionDAGBuilder.
+  virtual bool
+  shouldExpandPartialReductionIntrinsic(const IntrinsicInst *I) const {
+    return true;
+  }
+
   /// Return true if the @llvm.get.active.lane.mask intrinsic should be expanded
   /// using generic code in SelectionDAGBuilder.
   virtual bool shouldExpandGetActiveLaneMask(EVT VT, EVT OpVT) const {

llvm/lib/Analysis/TargetTransformInfo.cpp

@@ -829,6 +829,15 @@ bool TargetTransformInfo::shouldPrefetchAddressSpace(unsigned AS) const {
   return TTIImpl->shouldPrefetchAddressSpace(AS);
 }
 
+InstructionCost TargetTransformInfo::getPartialReductionCost(
+    unsigned Opcode, Type *InputTypeA, Type *InputTypeB, Type *AccumType,
+    ElementCount VF, PartialReductionExtendKind OpAExtend,
+    PartialReductionExtendKind OpBExtend, std::optional<unsigned> BinOp) const {
+  return TTIImpl->getPartialReductionCost(Opcode, InputTypeA, InputTypeB,
+                                          AccumType, VF, OpAExtend, OpBExtend,
+                                          BinOp);
+}
+
 unsigned TargetTransformInfo::getMaxInterleaveFactor(ElementCount VF) const {
   return TTIImpl->getMaxInterleaveFactor(VF);
 }
@@ -940,6 +949,15 @@ InstructionCost TargetTransformInfo::getShuffleCost(
   return Cost;
 }
 
+TargetTransformInfo::PartialReductionExtendKind
+TargetTransformInfo::getPartialReductionExtendKind(Instruction *I) {
+  if (isa<SExtInst>(I))
+    return PR_SignExtend;
+  if (isa<ZExtInst>(I))
+    return PR_ZeroExtend;
+  return PR_None;
+}
+
 TTI::CastContextHint
 TargetTransformInfo::getCastContextHint(const Instruction *I) {
   if (!I)

llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp

@@ -74,6 +74,7 @@
 #include <cassert>
 #include <cstdint>
 #include <cstdlib>
+#include <deque>
 #include <limits>
 #include <optional>
 #include <set>
@@ -2411,6 +2412,35 @@ SDValue SelectionDAG::getShiftAmountOperand(EVT LHSTy, SDValue Op) {
   return getZExtOrTrunc(Op, SDLoc(Op), ShTy);
 }
 
+SDValue SelectionDAG::getPartialReduceAdd(SDLoc DL, EVT ReducedTy, SDValue Op1,
+                                          SDValue Op2) {
+  EVT FullTy = Op2.getValueType();
+
+  unsigned Stride = ReducedTy.getVectorMinNumElements();
+  unsigned ScaleFactor = FullTy.getVectorMinNumElements() / Stride;
+
+  // Collect all of the subvectors
+  std::deque<SDValue> Subvectors = {Op1};
+  for (unsigned I = 0; I < ScaleFactor; I++) {
+    auto SourceIndex = getVectorIdxConstant(I * Stride, DL);
+    Subvectors.push_back(
+        getNode(ISD::EXTRACT_SUBVECTOR, DL, ReducedTy, {Op2, SourceIndex}));
+  }
+
+  // Flatten the subvector tree
+  while (Subvectors.size() > 1) {
+    Subvectors.push_back(
+        getNode(ISD::ADD, DL, ReducedTy, {Subvectors[0], Subvectors[1]}));
+    Subvectors.pop_front();
+    Subvectors.pop_front();
+  }
+
+  assert(Subvectors.size() == 1 &&
+         "There should only be one subvector after tree flattening");
+
+  return Subvectors[0];
+}
+
 SDValue SelectionDAG::expandVAArg(SDNode *Node) {
   SDLoc dl(Node);
   const TargetLowering &TLI = getTargetLoweringInfo();

llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp

@@ -8000,34 +8000,15 @@ void SelectionDAGBuilder::visitIntrinsicCall(const CallInst &I,
     return;
   }
   case Intrinsic::experimental_vector_partial_reduce_add: {
-    SDValue OpNode = getValue(I.getOperand(1));
-    EVT ReducedTy = EVT::getEVT(I.getType());
-    EVT FullTy = OpNode.getValueType();
 
-    unsigned Stride = ReducedTy.getVectorMinNumElements();
-    unsigned ScaleFactor = FullTy.getVectorMinNumElements() / Stride;
-
-    // Collect all of the subvectors
-    std::deque<SDValue> Subvectors;
-    Subvectors.push_back(getValue(I.getOperand(0)));
-    for (unsigned i = 0; i < ScaleFactor; i++) {
-      auto SourceIndex = DAG.getVectorIdxConstant(i * Stride, sdl);
-      Subvectors.push_back(DAG.getNode(ISD::EXTRACT_SUBVECTOR, sdl, ReducedTy,
-                                       {OpNode, SourceIndex}));
-    }
-
-    // Flatten the subvector tree
-    while (Subvectors.size() > 1) {
-      Subvectors.push_back(DAG.getNode(ISD::ADD, sdl, ReducedTy,
-                                       {Subvectors[0], Subvectors[1]}));
-      Subvectors.pop_front();
-      Subvectors.pop_front();
+    if (!TLI.shouldExpandPartialReductionIntrinsic(cast<IntrinsicInst>(&I))) {
+      visitTargetIntrinsic(I, Intrinsic);
+      return;
     }
 
-    assert(Subvectors.size() == 1 &&
-           "There should only be one subvector after tree flattening");
-
-    setValue(&I, Subvectors[0]);
+    setValue(&I, DAG.getPartialReduceAdd(sdl, EVT::getEVT(I.getType()),
+                                         getValue(I.getOperand(0)),
+                                         getValue(I.getOperand(1))));
     return;
   }
   case Intrinsic::experimental_cttz_elts: {

llvm/lib/Target/AArch64/AArch64ISelLowering.cpp

@@ -1971,6 +1971,16 @@ bool AArch64TargetLowering::shouldExpandGetActiveLaneMask(EVT ResVT,
   return false;
 }
 
+bool AArch64TargetLowering::shouldExpandPartialReductionIntrinsic(
+    const IntrinsicInst *I) const {
+  if (I->getIntrinsicID() != Intrinsic::experimental_vector_partial_reduce_add)
+    return true;
+
+  EVT VT = EVT::getEVT(I->getType());
+  return VT != MVT::nxv4i32 && VT != MVT::nxv2i64 && VT != MVT::v4i32 &&
+         VT != MVT::v2i32;
+}
+
 bool AArch64TargetLowering::shouldExpandCttzElements(EVT VT) const {
   if (!Subtarget->isSVEorStreamingSVEAvailable())
     return true;
@@ -21250,6 +21260,64 @@ static SDValue tryCombineWhileLo(SDNode *N,
   return SDValue(N, 0);
 }
 
+SDValue tryLowerPartialReductionToDot(SDNode *N,
+                                      const AArch64Subtarget *Subtarget,
+                                      SelectionDAG &DAG) {
+
+  assert(N->getOpcode() == ISD::INTRINSIC_WO_CHAIN &&
+         getIntrinsicID(N) ==
+             Intrinsic::experimental_vector_partial_reduce_add &&
+         "Expected a partial reduction node");
+
+  bool Scalable = N->getValueType(0).isScalableVector();
+  if (Scalable && !Subtarget->isSVEorStreamingSVEAvailable())
+    return SDValue();
+  if (!Scalable && (!Subtarget->isNeonAvailable() || !Subtarget->hasDotProd()))
+    return SDValue();
+
+  SDLoc DL(N);
+
+  // The narrower of the two operands. Used as the accumulator
+  auto NarrowOp = N->getOperand(1);
+  auto MulOp = N->getOperand(2);
+  if (MulOp->getOpcode() != ISD::MUL)
+    return SDValue();
+
+  auto ExtA = MulOp->getOperand(0);
+  auto ExtB = MulOp->getOperand(1);
+  bool IsSExt = ExtA->getOpcode() == ISD::SIGN_EXTEND;
+  bool IsZExt = ExtA->getOpcode() == ISD::ZERO_EXTEND;
+  if (ExtA->getOpcode() != ExtB->getOpcode() || (!IsSExt && !IsZExt))
+    return SDValue();
+
+  auto A = ExtA->getOperand(0);
+  auto B = ExtB->getOperand(0);
+  if (A.getValueType() != B.getValueType())
+    return SDValue();
+
+  unsigned Opcode = 0;
+
+  if (IsSExt)
+    Opcode = AArch64ISD::SDOT;
+  else if (IsZExt)
+    Opcode = AArch64ISD::UDOT;
+
+  assert(Opcode != 0 && "Unexpected dot product case encountered.");
+
+  EVT ReducedType = N->getValueType(0);
+  EVT MulSrcType = A.getValueType();
+
+  // Dot products operate on chunks of four elements so there must be four times
+  // as many elements in the wide type
+  if ((ReducedType == MVT::nxv4i32 && MulSrcType == MVT::nxv16i8) ||
+      (ReducedType == MVT::nxv2i64 && MulSrcType == MVT::nxv8i16) ||
+      (ReducedType == MVT::v4i32 && MulSrcType == MVT::v16i8) ||
+      (ReducedType == MVT::v2i32 && MulSrcType == MVT::v8i8))
+    return DAG.getNode(Opcode, DL, ReducedType, NarrowOp, A, B);
+
+  return SDValue();
+}
+
 static SDValue performIntrinsicCombine(SDNode *N,
                                        TargetLowering::DAGCombinerInfo &DCI,
                                        const AArch64Subtarget *Subtarget) {
@@ -21258,6 +21326,12 @@ static SDValue performIntrinsicCombine(SDNode *N,
   switch (IID) {
   default:
     break;
+  case Intrinsic::experimental_vector_partial_reduce_add: {
+    if (auto Dot = tryLowerPartialReductionToDot(N, Subtarget, DAG))
+      return Dot;
+    return DAG.getPartialReduceAdd(SDLoc(N), N->getValueType(0),
+                                   N->getOperand(1), N->getOperand(2));
+  }
   case Intrinsic::aarch64_neon_vcvtfxs2fp:
   case Intrinsic::aarch64_neon_vcvtfxu2fp:
     return tryCombineFixedPointConvert(N, DCI, DAG);

llvm/lib/Target/AArch64/AArch64ISelLowering.h

@@ -991,6 +991,9 @@ class AArch64TargetLowering : public TargetLowering {
 
   bool shouldExpandGetActiveLaneMask(EVT VT, EVT OpVT) const override;
 
+  bool
+  shouldExpandPartialReductionIntrinsic(const IntrinsicInst *I) const override;
+
   bool shouldExpandCttzElements(EVT VT) const override;
 
   /// If a change in streaming mode is required on entry to/return from a