if (SUPRESS_DU_FOR_PHYSICALS && reg.isPhysical()) return;
  static void removeDef(OPT_RegisterOperand regOp) {        OPT_Register reg = regOp.register;    if (regOp == reg.defList) {      reg.defList = reg.defList.getNext();    } else {      OPT_RegisterOperand prev = reg.defList;      OPT_RegisterOperand curr = prev.getNext();      while (curr != regOp) {        prev = curr;        curr = curr.getNext();      }      prev.setNext(curr.getNext());    }    if (DEBUG) {      VM.sysWrite("removed a def " + regOp.instruction + "\n");      printDefs(reg);    }  }