Lanai: Avoid implicit iterator conversions, NFC

[dexonsmith]

Summary

Avoid implicit conversions from MachineInstrBundleIterator to
MachineInstr* in the Lanai backend.

[dexonsmith]

+jpienaar

[jpienaar]

Looks good, thanks.

[dexonsmith]

Committed in r274942.

lib/Target/Lanai/LanaiFrameLowering.cpp

void LanaiFrameLowering::replaceAdjDynAllocPseudo(MachineFunction &MF) const {
   const LanaiInstrInfo &LII =
       *static_cast<const LanaiInstrInfo *>(STI.getInstrInfo());
   unsigned MaxCallFrameSize = MF.getFrameInfo()->getMaxCallFrameSize();
 
   for (MachineFunction::iterator MBB = MF.begin(), E = MF.end(); MBB != E;
        ++MBB) {
     MachineBasicBlock::iterator MBBI = MBB->begin();
     while (MBBI != MBB->end()) {
-      MachineInstr *MI = MBBI++;
-      if (MI->getOpcode() == Lanai::ADJDYNALLOC) {
-        DebugLoc DL = MI->getDebugLoc();
-        unsigned Dst = MI->getOperand(0).getReg();
-        unsigned Src = MI->getOperand(1).getReg();
+      MachineInstr &MI = *MBBI++;
+      if (MI.getOpcode() == Lanai::ADJDYNALLOC) {
+        DebugLoc DL = MI.getDebugLoc();
+        unsigned Dst = MI.getOperand(0).getReg();
+        unsigned Src = MI.getOperand(1).getReg();
 
         BuildMI(*MBB, MI, DL, LII.get(Lanai::ADD_I_LO), Dst)
             .addReg(Src)
             .addImm(MaxCallFrameSize);
-        MI->eraseFromParent();
+        MI.eraseFromParent();
       }
     }
   }
 }
 
 // Generates the following sequence for function entry:
 //   st %fp,-4[*%sp]        !push old FP
 //   add %sp,8,%fp          !generate new FP