if (VM.VerifyAssertions) VM.assert(s.operator != PHI);
if (VM.VerifyAssertions) VM._assert(s.operator != PHI);
  public void registerUnknown (OPT_Instruction s, OPT_BasicBlock b) {    if (VM.VerifyAssertions) VM.assert(s.operator != PHI);    // setup an array of all heap variables    // TODO: for efficiency, cache a copy of 'all'     Iterator vars = heapVariables.values().iterator();    OPT_HeapOperand[] all = new OPT_HeapOperand[heapVariables.size()];    for (int i = 0; i < all.length; i++) {      all[i] = new OPT_HeapOperand((OPT_HeapVariable)vars.next());      all[i].setInstruction(s);      // record that all[i] is def'ed in b      all[i].getHeapVariable().registerDef(b);    }    // record that s uses and defs all heap variables    uses.put(s, all);    defs.put(s, all);    // record that instruction s can exit the procedure    exits.add(s);  }