[AMDGPU] Implement llvm.lround intrinsic lowering. (#98970)

Summary:
This patch enables the target-independent lowering of llvm.lround via
GlobalISel. For SelectionDAG, the instrinsic is custom lowered for
AMDGPU. In order to support vector floating point input for llvm.lround,
this patch extends the target independent APIs and provide support for
scalarizing. pr98950 is needed to let verifier allow vector floating
point types

Test Plan: 

Reviewers: 

Subscribers: 

Tasks: 

Tags: 


Differential Revision: https://phabricator.intern.facebook.com/D60251041

Author: sgundapa

llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp

@@ -3881,6 +3881,17 @@ LegalizerHelper::lower(MachineInstr &MI, unsigned TypeIdx, LLT LowerHintTy) {
     return lowerFMad(MI);
   case TargetOpcode::G_FFLOOR:
     return lowerFFloor(MI);
+  case TargetOpcode::G_LROUND:
+  case TargetOpcode::G_LLROUND: {
+    Register DstReg = MI.getOperand(0).getReg();
+    Register SrcReg = MI.getOperand(1).getReg();
+    LLT SrcTy = MRI.getType(SrcReg);
+    auto Round = MIRBuilder.buildInstr(TargetOpcode::G_INTRINSIC_ROUND, {SrcTy},
+                                       {SrcReg});
+    MIRBuilder.buildFPTOSI(DstReg, Round);
+    MI.eraseFromParent();
+    return Legalized;
+  }
   case TargetOpcode::G_INTRINSIC_ROUND:
     return lowerIntrinsicRound(MI);
   case TargetOpcode::G_FRINT: {

llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp

@@ -3439,6 +3439,16 @@ bool SelectionDAGLegalize::ExpandNode(SDNode *Node) {
   case ISD::FP_TO_UINT_SAT:
     Results.push_back(TLI.expandFP_TO_INT_SAT(Node, DAG));
     break;
+  case ISD::LROUND:
+  case ISD::LLROUND: {
+    SDValue Arg = Node->getOperand(0);
+    EVT ArgVT = Arg.getValueType();
+    EVT ResVT = Node->getValueType(0);
+    SDLoc dl(Node);
+    SDValue RoundNode = DAG.getNode(ISD::FROUND, dl, ArgVT, Arg);
+    Results.push_back(DAG.getNode(ISD::FP_TO_SINT, dl, ResVT, RoundNode));
+    break;
+  }
   case ISD::VAARG:
     Results.push_back(DAG.expandVAArg(Node));
     Results.push_back(Results[0].getValue(1));

llvm/lib/CodeGen/TargetLoweringBase.cpp

@@ -824,13 +824,16 @@ void TargetLoweringBase::initActions() {
                      Expand);
 
   // These library functions default to expand.
-  setOperationAction({ISD::FCBRT,      ISD::FLOG,    ISD::FLOG2,  ISD::FLOG10,
-                      ISD::FEXP,       ISD::FEXP2,   ISD::FEXP10, ISD::FFLOOR,
-                      ISD::FNEARBYINT, ISD::FCEIL,   ISD::FRINT,  ISD::FTRUNC,
-                      ISD::LROUND,     ISD::LLROUND, ISD::LRINT,  ISD::LLRINT,
-                      ISD::FROUNDEVEN, ISD::FTAN,    ISD::FACOS,  ISD::FASIN,
-                      ISD::FATAN,      ISD::FCOSH,   ISD::FSINH,  ISD::FTANH},
-                     {MVT::f32, MVT::f64, MVT::f128}, Expand);
+  setOperationAction(
+      {ISD::FCBRT, ISD::FLOG,   ISD::FLOG2,  ISD::FLOG10,     ISD::FEXP,
+       ISD::FEXP2, ISD::FEXP10, ISD::FFLOOR, ISD::FNEARBYINT, ISD::FCEIL,
+       ISD::FRINT, ISD::FTRUNC, ISD::LRINT,  ISD::LLRINT,     ISD::FROUNDEVEN,
+       ISD::FTAN,  ISD::FACOS,  ISD::FASIN,  ISD::FATAN,      ISD::FCOSH,
+       ISD::FSINH, ISD::FTANH},
+      {MVT::f32, MVT::f64, MVT::f128}, Expand);
+
+  setOperationAction({ISD::LROUND, ISD::LLROUND},
+                     {MVT::f32, MVT::f64, MVT::f128}, LibCall);
 
   setOperationAction({ISD::FTAN, ISD::FACOS, ISD::FASIN, ISD::FATAN, ISD::FCOSH,
                       ISD::FSINH, ISD::FTANH},

llvm/lib/Target/AMDGPU/AMDGPUISelLowering.cpp

@@ -397,6 +397,8 @@ AMDGPUTargetLowering::AMDGPUTargetLowering(const TargetMachine &TM,
 
   setOperationAction(ISD::FLOG2, MVT::f32, Custom);
   setOperationAction(ISD::FROUND, {MVT::f32, MVT::f64}, Custom);
+  setOperationAction({ISD::LROUND, ISD::LLROUND},
+                     {MVT::f16, MVT::f32, MVT::f64}, Expand);
 
   setOperationAction(
       {ISD::FLOG, ISD::FLOG10, ISD::FEXP, ISD::FEXP2, ISD::FEXP10}, MVT::f32,

llvm/lib/Target/AMDGPU/AMDGPULegalizerInfo.cpp

@@ -1131,6 +1131,11 @@ AMDGPULegalizerInfo::AMDGPULegalizerInfo(const GCNSubtarget &ST_,
        .scalarize(0)
        .lower();
 
+  getActionDefinitionsBuilder({G_LROUND, G_LLROUND})
+      .clampScalar(0, S16, S64)
+      .scalarize(0)
+      .lower();
+
   getActionDefinitionsBuilder(G_INTRINSIC_FPTRUNC_ROUND)
       .customFor({S16, S32})
       .scalarize(0)

llvm/lib/Target/X86/X86ISelLowering.cpp

@@ -849,8 +849,8 @@ X86TargetLowering::X86TargetLowering(const X86TargetMachine &TM,
     setOperationAction(ISD::FNEARBYINT, MVT::f80, Expand);
     setOperationAction(ISD::FROUNDEVEN, MVT::f80, Expand);
     setOperationAction(ISD::FMA, MVT::f80, Expand);
-    setOperationAction(ISD::LROUND, MVT::f80, Expand);
-    setOperationAction(ISD::LLROUND, MVT::f80, Expand);
+    setOperationAction(ISD::LROUND, MVT::f80, LibCall);
+    setOperationAction(ISD::LLROUND, MVT::f80, LibCall);
     setOperationAction(ISD::LRINT, MVT::f80, Custom);
     setOperationAction(ISD::LLRINT, MVT::f80, Custom);