RegAllocGreedy.cpp

    NamedRegionTimer T("Rewriter", TimerGroupName, TimePassesIsEnabled);
    std::auto_ptr<VirtRegRewriter> rewriter(createVirtRegRewriter());
    rewriter->runOnMachineFunction(*MF, *VRM, LIS);
  }

  // The pass output is in VirtRegMap. Release all the transient data.
  releaseMemory();

  return true;
}