public void markDirty(Instruction s,Register symb){
  HashSet<Register> set=dirtyMap.get(s);
  if (set == null) {
    set=new HashSet<Register>(3);
    dirtyMap.put(s,set);
  }
  set.add(symb);
}

public void markDirty ( Instruction s , Register symb ) { HashSet < Register > set = dirtyMap . get ( s ) ; if ( set == null ) { set = new HashSet < Register > ( 3 ) ; dirtyMap . put ( s , set ) ; } set . add ( symb ) ; }
records that the real value of a symbolic register is cached in a dirty scratch register at a given instruction that is a gc point .
