[RISCV] Promote SETCC and VP_SETCC of f16 vectors when only have zvfhmin (#66866)

This patch implements the promotion of fp16 vectors SETCC and VP_SETCC
when we only have zvfhmin but no zvfh.

Author: jacquesguan

llvm/lib/CodeGen/SelectionDAG/LegalizeVectorOps.cpp

@@ -173,6 +173,12 @@ class VectorLegalizer {
   /// result is truncated back to the original scalar type.
   void PromoteReduction(SDNode *Node, SmallVectorImpl<SDValue> &Results);
 
+  /// Implements vector setcc operation promotion.
+  ///
+  /// All vector operands are promoted to a vector type with larger element
+  /// type.
+  void PromoteSETCC(SDNode *Node, SmallVectorImpl<SDValue> &Results);
+
 public:
   VectorLegalizer(SelectionDAG& dag) :
       DAG(dag), TLI(dag.getTargetLoweringInfo()) {}
@@ -603,6 +609,31 @@ void VectorLegalizer::PromoteReduction(SDNode *Node,
   Results.push_back(Res);
 }
 
+void VectorLegalizer::PromoteSETCC(SDNode *Node,
+                                   SmallVectorImpl<SDValue> &Results) {
+  MVT VecVT = Node->getOperand(0).getSimpleValueType();
+  MVT NewVecVT = TLI.getTypeToPromoteTo(Node->getOpcode(), VecVT);
+
+  unsigned ExtOp = VecVT.isFloatingPoint() ? ISD::FP_EXTEND : ISD::ANY_EXTEND;
+
+  SDLoc DL(Node);
+  SmallVector<SDValue, 5> Operands(Node->getNumOperands());
+
+  Operands[0] = DAG.getNode(ExtOp, DL, NewVecVT, Node->getOperand(0));
+  Operands[1] = DAG.getNode(ExtOp, DL, NewVecVT, Node->getOperand(1));
+  Operands[2] = Node->getOperand(2);
+
+  if (Node->getOpcode() == ISD::VP_SETCC) {
+    Operands[3] = Node->getOperand(3); // mask
+    Operands[4] = Node->getOperand(4); // evl
+  }
+
+  SDValue Res = DAG.getNode(Node->getOpcode(), DL, Node->getSimpleValueType(0),
+                            Operands, Node->getFlags());
+
+  Results.push_back(Res);
+}
+
 void VectorLegalizer::Promote(SDNode *Node, SmallVectorImpl<SDValue> &Results) {
   // For a few operations there is a specific concept for promotion based on
   // the operand's type.
@@ -638,6 +669,11 @@ void VectorLegalizer::Promote(SDNode *Node, SmallVectorImpl<SDValue> &Results) {
     // Promote the operation by extending the operand.
     PromoteReduction(Node, Results);
     return;
+  case ISD::VP_SETCC:
+  case ISD::SETCC:
+    // Promote the operation by extending the operand.
+    PromoteSETCC(Node, Results);
+    return;
   case ISD::FP_ROUND:
   case ISD::FP_EXTEND:
     // These operations are used to do promotion so they can't be promoted

llvm/lib/Target/RISCV/RISCVISelLowering.cpp

@@ -822,11 +822,11 @@ RISCVTargetLowering::RISCVTargetLowering(const TargetMachine &TM,
 
     // TODO: support more ops.
     static const unsigned ZvfhminPromoteOps[] = {
-        ISD::FMINNUM,    ISD::FMAXNUM,    ISD::FADD,        ISD::FSUB,
-        ISD::FMUL,       ISD::FMA,        ISD::FDIV,        ISD::FSQRT,
-        ISD::FABS,       ISD::FNEG,       ISD::FCOPYSIGN,   ISD::FCEIL,
-        ISD::FFLOOR,     ISD::FROUND,     ISD::FROUNDEVEN,  ISD::FRINT,
-        ISD::FNEARBYINT, ISD::IS_FPCLASS, ISD::SPLAT_VECTOR};
+        ISD::FMINNUM,    ISD::FMAXNUM,    ISD::FADD,         ISD::FSUB,
+        ISD::FMUL,       ISD::FMA,        ISD::FDIV,         ISD::FSQRT,
+        ISD::FABS,       ISD::FNEG,       ISD::FCOPYSIGN,    ISD::FCEIL,
+        ISD::FFLOOR,     ISD::FROUND,     ISD::FROUNDEVEN,   ISD::FRINT,
+        ISD::FNEARBYINT, ISD::IS_FPCLASS, ISD::SPLAT_VECTOR, ISD::SETCC};
 
     // TODO: support more vp ops.
     static const unsigned ZvfhminPromoteVPOps[] = {
@@ -837,7 +837,7 @@ RISCVTargetLowering::RISCVTargetLowering(const TargetMachine &TM,
         ISD::VP_FMINNUM,     ISD::VP_FMAXNUM,      ISD::VP_FCEIL,
         ISD::VP_FFLOOR,      ISD::VP_FROUND,       ISD::VP_FROUNDEVEN,
         ISD::VP_FCOPYSIGN,   ISD::VP_FROUNDTOZERO, ISD::VP_FRINT,
-        ISD::VP_FNEARBYINT};
+        ISD::VP_FNEARBYINT,  ISD::VP_SETCC};
 
     // Sets common operation actions on RVV floating-point vector types.
     const auto SetCommonVFPActions = [&](MVT VT) {
@@ -5392,6 +5392,11 @@ static SDValue SplitVPOp(SDValue Op, SelectionDAG &DAG) {
           DAG.SplitEVL(Op.getOperand(j), Op.getValueType(), DL);
       continue;
     }
+    if (!Op.getOperand(j).getValueType().isVector()) {
+      LoOperands[j] = Op.getOperand(j);
+      HiOperands[j] = Op.getOperand(j);
+      continue;
+    }
     std::tie(LoOperands[j], HiOperands[j]) =
         DAG.SplitVector(Op.getOperand(j), DL);
   }
@@ -6079,6 +6084,11 @@ SDValue RISCVTargetLowering::LowerOperation(SDValue Op,
       return DAG.getSetCC(DL, VT, RHS, LHS, CCVal);
     }
 
+    if (Op.getOperand(0).getSimpleValueType() == MVT::nxv32f16 &&
+        (Subtarget.hasVInstructionsF16Minimal() &&
+         !Subtarget.hasVInstructionsF16()))
+      return SplitVectorOp(Op, DAG);
+
     return lowerFixedLengthVectorSetccToRVV(Op, DAG);
   }
   case ISD::ADD:
@@ -6246,6 +6256,10 @@ SDValue RISCVTargetLowering::LowerOperation(SDValue Op,
   case ISD::VP_FP_TO_UINT:
     return lowerVPFPIntConvOp(Op, DAG);
   case ISD::VP_SETCC:
+    if (Op.getOperand(0).getSimpleValueType() == MVT::nxv32f16 &&
+        (Subtarget.hasVInstructionsF16Minimal() &&
+         !Subtarget.hasVInstructionsF16()))
+      return SplitVPOp(Op, DAG);
     if (Op.getOperand(0).getSimpleValueType().getVectorElementType() == MVT::i1)
       return lowerVPSetCCMaskOp(Op, DAG);
     [[fallthrough]];