通过表达式演算局部优化中间代码

常量合并，删除公共子表达式是中间代码优化时采用的有效技术，但在表达式间能进行的运算仅限于常量之间，极大地限制了可优化的范围，选择一类简单而基本的表达式及表达式运算，在正规化表示的基础上进行表达式的静态运算，尽可能地了化简要表达式，压缩代码代度并找出更锪公共子表达式，以达到更好的优化效果。

Optimize Intermediate Code in Basic Block through Expression Calculus

Constant folding, common subexpression elimination are effective techniques in optimizing intermediate code. But operations on expressions are confined to those on constants. It will greatly limit the range of optimization. In this paper, we manage to choose a set of basic expressions and their corresponding operations, perform static expression operations on the standerdized expressions so as to simply expressions, shorten code and find as more common subexpression as possible in order to get better result of optimization.