enum = null;
bbEnum = null;
  OPT_LTDominatorInfo(OPT_BasicBlock block) {    semiDominator = 0;    dominator = null;    parent = null;    bucket = new java.util.HashSet();    ancestor = null;    label = block;    size = 1;    child = null;    enum = null;  }  /**   *   This method returns the set of blocks that dominates the passed   *   block, i.e., it answers the question "Who dominates me?"   *   *   @param block the block of interest   *   @param ir    the governing ir   *   @return a BitVector containing those blocks that dominate the passed one   */  public OPT_BitVector dominators(OPT_BasicBlock block, OPT_IR ir) {    // Currently this set is computed on demand.  We may want to cache    // the result for reuse.  The cost of computing is the height of the    // the dominator tree.    OPT_BitVector dominators = new OPT_BitVector(ir.getMaxBasicBlockNumber()+1);    dominators.set(block.getNumber());    while ((block = getIdom(block)) != null) {      dominators.set(block.getNumber());    }    return  dominators;  }