This paper discusses the target of loops optimization and various methods of program transformation which can significantly reduce the access time to subscripted variables, diminish some types of dependence, increase the " depth " of software pipelining, and merge some iterations of loops in order to make code compaction easier 程序變換可大大減少下標變數的訪問時間;消除某些類型的相關,提高軟件流水的“深度”;合并多個循環,有利于進行代碼壓縮。