ScratchRegister result = null;
  private ScratchRegister getPhysicalScratchRegister(OPT_Register r) {    ScratchRegister result = null;    for (Iterator i = scratchInUse.iterator(); i.hasNext(); ) {      ScratchRegister sr = (ScratchRegister)i.next();      if (sr.scratch == r) {        return sr;      }    }    return null;  }