Introduce readfirstlane if dst reg is sgpr

Author: PankajDwivedi-25

llvm/lib/Target/AMDGPU/SIISelLowering.cpp

@@ -3220,6 +3220,7 @@ SITargetLowering::LowerReturn(SDValue Chain, CallingConv::ID CallConv,
                               const SDLoc &DL, SelectionDAG &DAG) const {
   MachineFunction &MF = DAG.getMachineFunction();
   SIMachineFunctionInfo *Info = MF.getInfo<SIMachineFunctionInfo>();
+  const SIRegisterInfo *TRI = getSubtarget()->getRegisterInfo();
 
   if (AMDGPU::isKernel(CallConv)) {
     return AMDGPUTargetLowering::LowerReturn(Chain, CallConv, isVarArg, Outs,
@@ -3275,8 +3276,9 @@ SITargetLowering::LowerReturn(SDValue Chain, CallingConv::ID CallConv,
     default:
       llvm_unreachable("Unknown loc info!");
     }
-    Arg = DAG.getNode(ISD::INTRINSIC_WO_CHAIN, DL, Arg.getValueType(),
-                      ReadFirstLane, Arg);
+    if (TRI->isSGPRPhysReg(VA.getLocReg()))
+      Arg = DAG.getNode(ISD::INTRINSIC_WO_CHAIN, DL, Arg.getValueType(),
+                        ReadFirstLane, Arg);
     Chain = DAG.getCopyToReg(Chain, DL, VA.getLocReg(), Arg, Glue);
     Glue = Chain.getValue(1);
     RetOps.push_back(DAG.getRegister(VA.getLocReg(), VA.getLocVT()));