[InlineSpiller] Clean-up isSpillCandBB

[skatkov]

Summary

This is mostly NFC except that for end of BB not previous slot is used.
Idx is used to find a def of sibling live interval in that slot.
The def on end of MBB and previous slot of end MBB should be the same,
so it should be NFC.

[rnk]

lgtm

llvm/lib/CodeGen/InlineSpiller.cpp

bool HoistSpillHelper::rmFromMergeableSpills(MachineInstr &Spill,
   std::pair<int, VNInfo *> MIdx = std::make_pair(StackSlot, OrigVNI);
   return MergeableSpills[MIdx].erase(&Spill);
 }
 
 /// Check BB to see if it is a possible target BB to place a hoisted spill,
 /// i.e., there should be a living sibling of OrigReg at the insert point.
 bool HoistSpillHelper::isSpillCandBB(LiveInterval &OrigLI, VNInfo &OrigVNI,
                                      MachineBasicBlock &BB, Register &LiveReg) {
-  SlotIndex Idx;
+  SlotIndex Idx = IPA.getLastInsertPoint(OrigLI, BB);
   Register OrigReg = OrigLI.reg();
-  MachineBasicBlock::iterator MI = IPA.getLastInsertPointIter(OrigLI, BB);
-  if (MI != BB.end())
-    Idx = LIS.getInstructionIndex(*MI);
-  else
-    Idx = LIS.getMBBEndIdx(&BB).getPrevSlot();
   SmallSetVector<Register, 16> &Siblings = Virt2SiblingsMap[OrigReg];
   assert(OrigLI.getVNInfoAt(Idx) == &OrigVNI && "Unexpected VNI");
 
   for (const Register &SibReg : Siblings) {
     LiveInterval &LI = LIS.getInterval(SibReg);
     VNInfo *VNI = LI.getVNInfoAt(Idx);
     if (VNI) {
       LiveReg = SibReg;