[RISCV] Use Subtarget member variable instead of getting it from MachineFunction. NFC (#159664)

Author: topperc

llvm/lib/Target/RISCV/RISCVISelLowering.cpp

@@ -23464,7 +23464,6 @@ RISCVTargetLowering::LowerReturn(SDValue Chain, CallingConv::ID CallConv,
                                  const SmallVectorImpl<SDValue> &OutVals,
                                  const SDLoc &DL, SelectionDAG &DAG) const {
   MachineFunction &MF = DAG.getMachineFunction();
-  const RISCVSubtarget &STI = MF.getSubtarget<RISCVSubtarget>();
 
   // Stores the assignment of the return value to a location.
   SmallVector<CCValAssign, 16> RVLocs;
@@ -23499,8 +23498,8 @@ RISCVTargetLowering::LowerReturn(SDValue Chain, CallingConv::ID CallConv,
       Register RegLo = VA.getLocReg();
       Register RegHi = RVLocs[++i].getLocReg();
 
-      if (STI.isRegisterReservedByUser(RegLo) ||
-          STI.isRegisterReservedByUser(RegHi))
+      if (Subtarget.isRegisterReservedByUser(RegLo) ||
+          Subtarget.isRegisterReservedByUser(RegHi))
         MF.getFunction().getContext().diagnose(DiagnosticInfoUnsupported{
             MF.getFunction(),
             "Return value register required, but has been reserved."});
@@ -23516,7 +23515,7 @@ RISCVTargetLowering::LowerReturn(SDValue Chain, CallingConv::ID CallConv,
       Val = convertValVTToLocVT(DAG, Val, VA, DL, Subtarget);
       Chain = DAG.getCopyToReg(Chain, DL, VA.getLocReg(), Val, Glue);
 
-      if (STI.isRegisterReservedByUser(VA.getLocReg()))
+      if (Subtarget.isRegisterReservedByUser(VA.getLocReg()))
         MF.getFunction().getContext().diagnose(DiagnosticInfoUnsupported{
             MF.getFunction(),
             "Return value register required, but has been reserved."});
@@ -23553,11 +23552,11 @@ RISCVTargetLowering::LowerReturn(SDValue Chain, CallingConv::ID CallConv,
     if (Kind == "supervisor")
       RetOpc = RISCVISD::SRET_GLUE;
     else if (Kind == "rnmi") {
-      assert(STI.hasFeature(RISCV::FeatureStdExtSmrnmi) &&
+      assert(Subtarget.hasFeature(RISCV::FeatureStdExtSmrnmi) &&
              "Need Smrnmi extension for rnmi");
       RetOpc = RISCVISD::MNRET_GLUE;
     } else if (Kind == "qci-nest" || Kind == "qci-nonest") {
-      assert(STI.hasFeature(RISCV::FeatureVendorXqciint) &&
+      assert(Subtarget.hasFeature(RISCV::FeatureVendorXqciint) &&
              "Need Xqciint for qci-(no)nest");
       RetOpc = RISCVISD::QC_C_MILEAVERET_GLUE;
     } else
@@ -23571,10 +23570,9 @@ void RISCVTargetLowering::validateCCReservedRegs(
     const SmallVectorImpl<std::pair<llvm::Register, llvm::SDValue>> &Regs,
     MachineFunction &MF) const {
   const Function &F = MF.getFunction();
-  const RISCVSubtarget &STI = MF.getSubtarget<RISCVSubtarget>();
 
-  if (llvm::any_of(Regs, [&STI](auto Reg) {
-        return STI.isRegisterReservedByUser(Reg.first);
+  if (llvm::any_of(Regs, [this](auto Reg) {
+        return Subtarget.isRegisterReservedByUser(Reg.first);
       }))
     F.getContext().diagnose(DiagnosticInfoUnsupported{
         F, "Argument register required, but has been reserved."});