[ISel/RISCV] Fix fixed-vector [l]lrint lowering (#145898)

Make the fixed-vector lowering of ISD::[L]LRINT use the custom-lowering
routine, lowerVectorXRINT, and fix issues in lowerVectorXRINT related to
this new functionality.

Author: artagnon

llvm/lib/Target/RISCV/RISCVISelLowering.cpp

@@ -1505,7 +1505,8 @@ RISCVTargetLowering::RISCVTargetLowering(const TargetMachine &TM,
                            VT, Custom);
 
         setOperationAction({ISD::FTRUNC, ISD::FCEIL, ISD::FFLOOR, ISD::FROUND,
-                            ISD::FROUNDEVEN, ISD::FRINT, ISD::FNEARBYINT},
+                            ISD::FROUNDEVEN, ISD::FRINT, ISD::LRINT,
+                            ISD::LLRINT, ISD::FNEARBYINT},
                            VT, Custom);
 
         setCondCodeAction(VFPCCToExpand, VT, Expand);
@@ -3208,7 +3209,14 @@ static RISCVFPRndMode::RoundingMode matchRoundingOp(unsigned Opc) {
   case ISD::VP_FROUND:
     return RISCVFPRndMode::RMM;
   case ISD::FRINT:
+  case ISD::LRINT:
+  case ISD::LLRINT:
+  case ISD::STRICT_FRINT:
+  case ISD::STRICT_LRINT:
+  case ISD::STRICT_LLRINT:
   case ISD::VP_FRINT:
+  case ISD::VP_LRINT:
+  case ISD::VP_LLRINT:
     return RISCVFPRndMode::DYN;
   }
 
@@ -3458,28 +3466,34 @@ lowerFTRUNC_FCEIL_FFLOOR_FROUND(SDValue Op, SelectionDAG &DAG,
 // Expand vector LRINT and LLRINT by converting to the integer domain.
 static SDValue lowerVectorXRINT(SDValue Op, SelectionDAG &DAG,
                                 const RISCVSubtarget &Subtarget) {
-  MVT VT = Op.getSimpleValueType();
-  assert(VT.isVector() && "Unexpected type");
-
   SDLoc DL(Op);
+  MVT DstVT = Op.getSimpleValueType();
   SDValue Src = Op.getOperand(0);
-  MVT ContainerVT = VT;
+  MVT SrcVT = Src.getSimpleValueType();
+  assert(SrcVT.isVector() && DstVT.isVector() &&
+         !(SrcVT.isFixedLengthVector() ^ DstVT.isFixedLengthVector()) &&
+         "Unexpected type");
 
-  if (VT.isFixedLengthVector()) {
-    ContainerVT = getContainerForFixedLengthVector(DAG, VT, Subtarget);
-    Src = convertToScalableVector(ContainerVT, Src, DAG, Subtarget);
+  MVT DstContainerVT = DstVT;
+  MVT SrcContainerVT = SrcVT;
+
+  if (DstVT.isFixedLengthVector()) {
+    DstContainerVT = getContainerForFixedLengthVector(DAG, DstVT, Subtarget);
+    SrcContainerVT = getContainerForFixedLengthVector(DAG, SrcVT, Subtarget);
+    Src = convertToScalableVector(SrcContainerVT, Src, DAG, Subtarget);
   }
 
-  auto [Mask, VL] = getDefaultVLOps(VT, ContainerVT, DL, DAG, Subtarget);
-  SDValue Truncated = DAG.getNode(
-      RISCVISD::VFCVT_RM_X_F_VL, DL, ContainerVT, Src, Mask,
-      DAG.getTargetConstant(RISCVFPRndMode::DYN, DL, Subtarget.getXLenVT()),
-      VL);
+  auto [Mask, VL] = getDefaultVLOps(SrcVT, SrcContainerVT, DL, DAG, Subtarget);
+  SDValue Res =
+      DAG.getNode(RISCVISD::VFCVT_RM_X_F_VL, DL, DstContainerVT, Src, Mask,
+                  DAG.getTargetConstant(matchRoundingOp(Op.getOpcode()), DL,
+                                        Subtarget.getXLenVT()),
+                  VL);
 
-  if (!VT.isFixedLengthVector())
-    return Truncated;
+  if (!DstVT.isFixedLengthVector())
+    return Res;
 
-  return convertFromScalableVector(VT, Truncated, DAG, Subtarget);
+  return convertFromScalableVector(DstVT, Res, DAG, Subtarget);
 }
 
 static SDValue