[RISCV][GISel] Handle FP instructions in the default case of register bank selection. NFC

Use isPreISelGenericFloatingPointOpcode to to indicate when to use
an FP ValueMapping.

Author: topperc

llvm/lib/Target/RISCV/GISel/RISCVRegisterBankInfo.cpp

@@ -329,19 +329,6 @@ RISCVRegisterBankInfo::getInstrMapping(const MachineInstr &MI) const {
     OpdsMapping[2] = GPRValueMapping;
     OpdsMapping[3] = GPRValueMapping;
     break;
-  case TargetOpcode::G_FMA: {
-    LLT Ty = MRI.getType(MI.getOperand(0).getReg());
-    std::fill_n(OpdsMapping.begin(), 4, getFPValueMapping(Ty.getSizeInBits()));
-    break;
-  }
-  case TargetOpcode::G_FPEXT:
-  case TargetOpcode::G_FPTRUNC: {
-    LLT ToTy = MRI.getType(MI.getOperand(0).getReg());
-    LLT FromTy = MRI.getType(MI.getOperand(1).getReg());
-    OpdsMapping[0] = getFPValueMapping(ToTy.getSizeInBits());
-    OpdsMapping[1] = getFPValueMapping(FromTy.getSizeInBits());
-    break;
-  }
   case TargetOpcode::G_FPTOSI:
   case TargetOpcode::G_FPTOUI: {
     LLT Ty = MRI.getType(MI.getOperand(1).getReg());
@@ -356,11 +343,6 @@ RISCVRegisterBankInfo::getInstrMapping(const MachineInstr &MI) const {
     OpdsMapping[1] = GPRValueMapping;
     break;
   }
-  case TargetOpcode::G_FCONSTANT: {
-    LLT Ty = MRI.getType(MI.getOperand(0).getReg());
-    OpdsMapping[0] = getFPValueMapping(Ty.getSizeInBits());
-    break;
-  }
   case TargetOpcode::G_FCMP: {
     LLT Ty = MRI.getType(MI.getOperand(2).getReg());
 
@@ -375,9 +357,16 @@ RISCVRegisterBankInfo::getInstrMapping(const MachineInstr &MI) const {
     // By default map all scalars to GPR.
     for (unsigned Idx = 0; Idx < NumOperands; ++Idx) {
        auto &MO = MI.getOperand(Idx);
-       if (!MO.isReg())
+       if (!MO.isReg() || !MO.getReg())
+         continue;
+       LLT Ty = MRI.getType(MO.getReg());
+       if (!Ty.isValid())
          continue;
-       OpdsMapping[Idx] = GPRValueMapping;
+
+       if (isPreISelGenericFloatingPointOpcode(Opc))
+         OpdsMapping[Idx] = getFPValueMapping(Ty.getSizeInBits());
+       else
+         OpdsMapping[Idx] = GPRValueMapping;
     }
     break;
   }