if (guard == null) return;
  private static void insertTrueGuard (OPT_Instruction inst,				       OPT_RegisterOperand guard) {    OPT_Instruction trueGuard = Move.create(GUARD_MOVE, guard.copyD2D(), 					    new OPT_TrueGuardOperand());    trueGuard.position = inst.position;    trueGuard.bcIndex  = inst.bcIndex;    inst.insertBefore (trueGuard);    OPT_DefUse.updateDUForNewInstruction(trueGuard);  }