编译原理-1-述.ppt

术语 语义分析(semantic analysis) The parsed program is further analyzed to determine whether it conforms to the source language’s contextual constraints:scope rules, type rules e.g. To relate each applied occurrence of an identifier in the source program to the corresponding declaration. 中间代码生成 源程序的内部(中间)表示 三元式、四元式 ( * id3 t1 t2 ) t2 = id3 * t1 id1:= id2 + id3 * 60 (1) (inttoreal, 60 - t1 ) (2) (* , id3 t1 t2 ) (3) (+ , id2 t2 t3 ) (4) (:= , t3 - id1 ) 中间代码生成(intermediate code generation) This is where the intermediate representation of the source program is created.We want this representation to be easy to generate,and easy to translate into the target program.The representation can have a variety of forms, but a common one is called three-address code or 4- tuple code. 代码优化 id1:= id2 + id3 * 60 (1) (inttoreal 60 - t1 ) (2) ( * id3 t1 t2 ) (3) ( + id2 t2 t3 ) (4) ( := t3 - id1 ) 变换 ? （1） ( * id3 60.0 t1 ) ( 2）（ + id2 t1 id1 ) 代码优化 t1 = b* c t1 = b* c t2 = t1+ 0 t2 = t1 + t1 t3 = b* c a = t2 t4 = t2 + t3 a = t4 代码优化(code optimization) Intermediate code optimization The optimizer accepts input in the intermediate representation and output a version still in the intermediate representation .In this phase,the compiler attempts to produce the smallest,fastest and most efficient running result by applying various techniques. Object code optimization 目标代码生成 (* , id3 60.0 t1 ) (+ , id2 t1 id1 ) movf id3,R2 mulf #60.0,R2 movf id2,R1 addf R2,R1 movf R1,id1 符号表管理 记录源程序中使用的名字 收集每个名字的各种属性信息 类型、作用域、分配存储信息 Const1 常量 值：35 Var1 变量 类型：实 层次：2 符号表(symbol table) Symbol table is a data structure which is employed to associate identifiers with their attributes . An identifier’s attribute consists of information relevant to contextual analysis,and is obtained from the identifier’s declaration. 出错处理 检查错误、报告出错信息、排错、恢复编译工作 * * *