public boolean isDirty(Instruction s,Register r){
  HashSet<Register> set=dirtyMap.get(s);
  if (set == null) {
    return false;
  }
 else {
    return set.contains(r);
  }
}

public boolean isDirty ( Instruction s , Register r ) { HashSet < Register > set = dirtyMap . get ( s ) ; if ( set == null ) { return false ; } else { return set . contains ( r ) ; } }
at gc point s , is the value of register r cached in a dirty scratch register ?
