[RISCV] Use MachineInstr::isFullCopy in a few places. NFC

Instead of checking that there's no subregisters.

Author: lukel97

llvm/lib/Target/RISCV/RISCVVLOptimizer.cpp

@@ -1346,9 +1346,7 @@ RISCVVLOptimizer::checkUsers(const MachineInstr &MI) const {
     const MachineInstr &UserMI = *UserOp.getParent();
     LLVM_DEBUG(dbgs() << "  Checking user: " << UserMI << "\n");
 
-    if (UserMI.isCopy() && UserMI.getOperand(0).getReg().isVirtual() &&
-        UserMI.getOperand(0).getSubReg() == RISCV::NoSubRegister &&
-        UserMI.getOperand(1).getSubReg() == RISCV::NoSubRegister) {
+    if (UserMI.isFullCopy() && UserMI.getOperand(0).getReg().isVirtual()) {
       LLVM_DEBUG(dbgs() << "    Peeking through uses of COPY\n");
       Worklist.insert_range(llvm::make_pointer_range(
           MRI->use_operands(UserMI.getOperand(0).getReg())));

llvm/lib/Target/RISCV/RISCVVectorMaskDAGMutation.cpp

@@ -40,9 +40,8 @@
 namespace llvm {
 
 static bool isCopyToV0(const MachineInstr &MI) {
-  return MI.isCopy() && MI.getOperand(0).getReg() == RISCV::V0 &&
-         MI.getOperand(1).getReg().isVirtual() &&
-         MI.getOperand(1).getSubReg() == RISCV::NoSubRegister;
+  return MI.isFullCopy() && MI.getOperand(0).getReg() == RISCV::V0 &&
+         MI.getOperand(1).getReg().isVirtual();
 }
 
 static bool isSoleUseCopyToV0(SUnit &SU) {