对于全域通用子运算式最佳化，编译器会搜寻整个函式中有没有通用子运算式。
For global common subexpression optimization, the compiler searches entire functions for common subexpressions.
传回范围的集合(一个集合对一个符合的子运算式)，而且它们的属性都是唯读的。
A collection of ranges is returned, one for each matched subexpression, and their properties are read-only.
对于区域通用子运算式最佳化，编译器会检查程序码的短区段中有没有通用子运算式。
For local common subexpression optimization, the compiler examines short sections of code for common subexpressions.
应用推荐