[RISCV] Reuse RISCVDAGToDAGISel member TTI in doPeepholeMaskedRVV. NFC

[luke]

Fix commit message

[craig.topper]

LGTM

llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp

bool RISCVDAGToDAGISel::doPeepholeMaskedRVV(SDNode *N) {
 
   unsigned MaskOpIdx = I->MaskOpIdx;
 
   if (!usesAllOnesMask(N, MaskOpIdx))
     return false;
 
   // Retrieve the tail policy operand index, if any.
   std::optional<unsigned> TailPolicyOpIdx;
-  const RISCVInstrInfo &TII = *Subtarget->getInstrInfo();
-  const MCInstrDesc &MaskedMCID = TII.get(N->getMachineOpcode());
+  const MCInstrDesc &MaskedMCID = TII->get(N->getMachineOpcode());
 
   bool UseTUPseudo = false;
   if (RISCVII::hasVecPolicyOp(MaskedMCID.TSFlags)) {
     // Some operations are their own TU.
     if (I->UnmaskedTUPseudo == I->UnmaskedPseudo) {
       UseTUPseudo = true;
     } else {
       TailPolicyOpIdx = getVecPolicyOpIdx(N, MaskedMCID);
       if (!(N->getConstantOperandVal(*TailPolicyOpIdx) &
             RISCVII::TAIL_AGNOSTIC)) {
         // Keep the true-masked instruction when there is no unmasked TU
         // instruction
         if (I->UnmaskedTUPseudo == I->MaskedPseudo)
           return false;
         UseTUPseudo = true;
       }
     }
   }
 
   unsigned Opc = UseTUPseudo ? I->UnmaskedTUPseudo : I->UnmaskedPseudo;
 
   // If this instruction is tail agnostic, the unmasked instruction should not
   // have a tied destination.
 #ifndef NDEBUG
-  const MCInstrDesc &MCID = TII.get(Opc);
+  const MCInstrDesc &MCID = TII->get(Opc);
   bool HasTiedDest = RISCVII::isFirstDefTiedToFirstUse(MCID);
   assert((UseTUPseudo == HasTiedDest) && "Unexpected pseudo to transform to");
 #endif
 
   SmallVector<SDValue, 8> Ops;
   // Skip the merge operand at index 0 if !UseTUPseudo.
   for (unsigned I = !UseTUPseudo, E = N->getNumOperands(); I != E; I++) {
     // Skip the mask, the policy, and the Glue.