if (SUPRESS_DU_FOR_PHYSICALS && reg.isPhysical()) return;
  static void removeUse(OPT_RegisterOperand regOp) {    OPT_Register reg = regOp.register;    if (regOp == reg.useList) {      reg.useList = reg.useList.getNext();    } else {      OPT_RegisterOperand prev = reg.useList;      OPT_RegisterOperand curr = prev.getNext();      while (curr != regOp) {        prev = curr;        curr = curr.getNext();      }      prev.setNext(curr.getNext());    }    reg.useCount--;    if (DEBUG) {      VM.sysWrite("removed a use " + regOp.instruction + "\n");      printUses(reg);    }  }