OPT_DominatorsPhase dom = new OPT_DominatorsPhase();
OPT_DominatorsPhase dom = new OPT_DominatorsPhase(false);
  void internalUpdateCFGFrequencies(OPT_IR ir) {    // Create an up to date loop structure tree    OPT_DominatorsPhase dom = new OPT_DominatorsPhase();    dom.perform(ir);    OPT_LSTGraph lst = ir.HIRInfo.LoopStructureTree;    if (lst == null) {      throw new OPT_OptimizingCompilerException("null loop structure tree");    }    // enumerate each basic block ...    for (Enumeration e = ir.getBasicBlocks(); e.hasMoreElements(); ) {      OPT_BasicBlock bb = (OPT_BasicBlock)e.nextElement();      // set the estimate count for this basic block      int depth = lst.getLoopNestDepth(bb);      if (DEBUG) 	VM.sysWrite("Depth is " + depth + "\n");      int freq = 1;      for (int i=0; i<depth; i++) 	freq *= LOOP_MULTIPLIER;      basicBlockMap.put(bb,new Double(freq));    }  }