VirtRegMap.cpp

        PhysReg = MI.getOperand(TiedOp).getReg();
        if (SubIdx) {
          unsigned SuperReg = findSuperReg(RC, PhysReg, SubIdx, TRI);
          assert(SuperReg && TRI->getSubReg(SuperReg, SubIdx) == PhysReg &&
                 "Can't find corresponding super-register!");
          PhysReg = SuperReg;
        }
      } else {
        PhysReg = VRM.getPhys(VirtReg);
        if (ReusedOperands.isClobbered(PhysReg)) {
          // Another def has taken the assigned physreg. It must have been a
          // use&def which got it due to reuse. Undo the reuse!
          PhysReg = ReusedOperands.GetRegForReload(PhysReg, &MI, 
                               Spills, MaybeDeadStores, RegKills, KillOps, VRM);
        }
      }

      assert(PhysReg && "VR not assigned a physical register?");
      RegInfo->setPhysRegUsed(PhysReg);
      unsigned RReg = SubIdx ? TRI->getSubReg(PhysReg, SubIdx) : PhysReg;
      ReusedOperands.markClobbered(RReg);
      MI.getOperand(i).setReg(RReg);

      if (!MO.isDead()) {
        MachineInstr *&LastStore = MaybeDeadStores[StackSlot];
        SpillRegToStackSlot(MBB, MII, -1, PhysReg, StackSlot, RC, true,
                          LastStore, Spills, ReMatDefs, RegKills, KillOps, VRM);
        NextMII = next(MII);

        // Check to see if this is a noop copy.  If so, eliminate the
        // instruction before considering the dest reg to be changed.
        {
          unsigned Src, Dst, SrcSR, DstSR;
          if (TII->isMoveInstr(MI, Src, Dst, SrcSR, DstSR) && Src == Dst) {
            ++NumDCE;
            DOUT << "Removing now-noop copy: " << MI;
            InvalidateKills(MI, RegKills, KillOps);
            VRM.RemoveMachineInstrFromMaps(&MI);
            MBB.erase(&MI);
            Erased = true;
            UpdateKills(*LastStore, RegKills, KillOps, TRI);
            goto ProcessNextInst;
          }
        }
      }    
    }
  ProcessNextInst:
    DistanceMap.insert(std::make_pair(&MI, Dist++));
    if (!Erased && !BackTracked) {
      for (MachineBasicBlock::iterator II = &MI; II != NextMII; ++II)
        UpdateKills(*II, RegKills, KillOps, TRI);
    }
    MII = NextMII;
  }

}

llvm::Spiller* llvm::createSpiller() {
  switch (SpillerOpt) {
  default: assert(0 && "Unreachable!");
  case local:
    return new LocalSpiller();
  case simple:
    return new SimpleSpiller();
  }
}