其实，学过编译原理的人都知道，到了中间代码级别那些赋值、入栈、出栈、跳转、调用指令时，能优化的余地已经很小，绝不可能对性能产生翻天覆地的变化。


---根据sun的官方文档，hotspot的优化级别显然比指令既要高，

Based upon the platform configuration, it will select a compiler, Java heap configuration, and garbage collector that produce good to excellent performance for most applications.