一个语法分析程序并生成四元式中间代码.doc

编写一个语法分析程序并生成四元式中间代码班级 学号 姓名： 指导老师： 一、 实验目的：1、 学习编译的基本原理；2、 巩固课堂学习的知识；3、 会对最基本的语句进行分析，转换成四元式；二、 实验内容： 编制一个大型程序，可以对小型的EL语言程序进行翻译，可以处理最基本的语句如：if语句，while语句等；三、 实验硬件和软件平台：INTEL C433MHz Cpu128Mb SDRAMTPWMicrosoft Windows XP SP1四、 步骤和算法描述：1、 先对输入的语句进行词法分析，建立各种表格；2、 对程序进行语法分析，建立四元式；对部分程序语句进行翻译，生成相应的四元式，及出错处理五 源程序：10program elcompiler(input,output,f); const reser=20; type alfa=packed array1.9 of char; opr=(jmp,prt,jeq,jne,jgt,jlt,jge,jle,add,sub,mul,did,ass,umi,jsr,ret,inp,out,xxx); 中间代码的操作码符号 instruction=record 四元式 op:opr; arg1,arg2,result:integer; end; symset=set of 0.45; obj=1.45; var reserve:array0.reser of alfa; 保留字表 token,id:alfa; line:array1.80 of char; 输入缓冲区 ch,ch1:char; quad:array0.300 of instruction; 四元式表 table:array0.100 of 符号表 recordname:alfa; level:integer; case cat:obj of 2 : (val:integer); 18,7: (addr:integer) end; mnemonic:arrayopr of array1.3 of char; cp,tp,new,nxq:integer; cc,ii,i,j,k,num:integer; kind,l,err:integer; filename:string; 外部文件名 f:text;procedure getchar; 从扫描缓冲区取一字符 begin if cc=ii then 如果已取到缓冲区的最后，则从外部 文件再读一行 begin if eof(f) then begin writeln(program incomplete!); close(f); exit end; cc:=0; ii:=0; cc is input to buffer pointer; ii is output pointer from buffer; while not eoln(f) do begin cc:=cc+1; read(f,linecc); write(linecc) end; readln(f); writeln; cc:=cc+1; linecc:= ; end; ii:=ii+1; ch:=lineii end; procedure getnbc; 读取非空字符 label l; begin l:getchar; while ch= do getchar; if ch= then begin repeat getchar until ch=;goto l end 跳过注解 end;procedure retract; 退回一 字符 begin ii:=ii-1 end;procedure scanner; 词法分析过程 begin getnbc; if ch in a.z then symbol is id or reserve begin k:=0; repeat if k10 then begin k:=k+1; tokenk:=ch end; getchar until not(ch ina.z,0.9); retract; if k10 then repeat k:=k+1; tokenk:= until k=10; id:=token; i:=0; j:=reser; repeat k:=(i+j) div 2; 对半查找保留字表 if id=reservek then i:=k+1 until ij; if i-1j then kind:=k else kind:=21 变量的类别 end else if ch in 0.9 then begin 整数 k:=0; num:=0; kind:=22; repeat num:=10*num+(ord(ch)-ord(0); k:=k+1; getnbc; until not(ch in 0.9); retract end else begin case ch of +,-:begin ch1:=ch; retract; retract; getchar; if (ch=) or (ch=() then 区分单目双目算符 if ch1=+ then kind:=32 else kind:=33 else if ch1=+ then kind:=34 else kind:=35; getchar end; *:kind:=36; /:kind:=37; ,:kind:=23; .:kind:=26; ;:begin writeln; kind:=24 end; (:kind:=27; ):kind:=28; :kind:=29; :kind:=30; =:kind:=38; : begin getnbc; if ch= then kind:=44 else begin retract; kind:=25 end end; #:kind:=47; :kind:=45; :kind:=46; :begin getnbc; if ch= then kind:=43 else begin retract; kind:=40 end end; then kind:=41 else begin kind:=39; retract end end; else; end; end end;procedure error(n:integer); 出错处理 begin write(*, ,ii-2,n:2); err:=err+1; case n of 0:writeln(lack program); 1:writeln(ought to= );2:writeln(lack=); 3:writeln(expected indent); 4:writeln(expected factor); 5:writeln(expeced ,;); 6:writeln(expected begin or functin); 7:writeln(expected statement) ; 8:writeln(expectedbegin); 9:writeln(expect ,); 10:writeln(num is too big); 11:writeln(indent isnt specify); 12:writeln(cant assign to const); 13:writeln(expeced :=); 14:writeln(expected (); 16:writeln(ought to then); 17:writeln(expected endor;); 18:writeln(ought to do); 19:writeln(expected ;on.); 20:writeln(expeced rop); 22:writeln(expected ); 23:writeln(may be to lack*); 25:writeln(to lack type specify); 26:writeln(indent double define) else ; end end;procedure test(s1,s2:symset;m:integer); 测试单词的合法 begin if not(kind in s1) then begin error(m); s1:=s1+s2; while not (kind in s1) do scanner end end;procedure gen(op:opr;ag1,ag2,result:integer); 生成中间代码 begin quadcp.op:=op;quadcp.arg1:=ag1; quadcp.arg2:=ag2;quadcp.result:=result; cp:=cp+1;nxq:=cp; end;procedure blk(lev,tp:integer;sys:symset); var tp0,cp0,dp:integer; chain:integer; function entry(iden:alfa):integer; var i:integer; begin i:=tp;:=iden; while iden do i:=i+1; entry:=i end;procedure fill(k:obj); 填写符号表 var i:integer; begin for i:=tp0 to tp do tp0 本分程序符号表首址 if =id then begin error(26); exit end; tp:=tp+1; with tabletp do begin name:=id; cat:=k; level:=lev; case k of 2: begin if num22767 then const 说明 begin error(10); num:=22767 end; val:=num; end; 18:begin addr:=dp; dp:=dp+1 end; var 说明7:addr:=0; function 说明 end end end;procedure constdec; 说明处理 begin if kind=21 then 变量 begin scanner if kind in 38,44 then =,:= begin if kind=44 then error(1); scanner; if kind=22 then begin fill(2); scanner end else error(4) end else error(2) end else error(3) end;procedure vardec; var说明处理 begin if kind=21 then begin fill(18); scanner end else error(4); end;procedure listquad; 显示中间代码结果 var i:integer; begin for i:=cp0 to cp-1 do with quadi do writeln(i:3,mnemonicop:6,arg1:6,arg2:6,result:6); end;procedure listtable; 显示符号表 var i:integer; begin for i:=1 to tp do with tablei do writeln(name:5,cat:5,level:5,val:5,addr:5); end;function newtemp:integer; 取一临时变量序号 begin new:=new+1; newtemp:=new end;procedure bp(p,t:integer); 回填四元式链 var q:integer; begin q:=p; while q0 do begin p:=quadq.result; quadq.result:=t; q:=p end end;function merg(p1,p2:integer):integer; 并链 var p:integer; begin if p2=0 then merg:=p1 else begin p:=p2; while quadp.result 0 do p:=quadp.result; quadp.result:=p1; end end;procedure statement(var schain:integer; sys :symset); 语句分析处理 var i,j,k,q,place:integer; ttc,ffc,slchain,s2chain:integer; function exp(sys:symset):integer; 表达式处理 var addop,e1place,e2place,t:integer; function term(sys:symset):integer; 项处理 var mulop,t1place,t2place,t:integer; function fact(sys:symset):integer; 因子处理 var i,j,k,f,f1,t1:integer; queue:array1.5 of integer; 存实参队列 begin test(27,21,22,sys,6); if kind=21 then 变量 begin i:=entry(id); if i=0 then begin error(11);scanner end else with tablei do case cat of 2:begin j:=val;fact:=j+10000;scanner end; 常数 18:begin j:=lev-level; k:=addr; lev当前层次 fact:=100*j+k;scanner; 变量地址 end; 7: begin scanner;f:=1; 函数调用 if kind=27 then begin scanner; k:=4; k+1是形参开始单元 queuef:=exp(28,23+sys); ), while kind=23 do begin scanner; f:=f+1; queuef:=exp(28,23+sys); end; if kind=28 then ) begin scanner; for f1:=1 to f do 传递实在参数 gen(ass,queuef1,0,dp+k+f1) end else error(22) end; f:=lev-level; f为相对当前的外层层次 gen(jsr,0,f,addr); 调函数 t1:=newtemp; gen(ass,dp,0,t1); 返回结果在dp单元 fact:=t1; 函数结果作为因子 end end case end else if kind=22 then 数 begin fact:=10000+num;scanner end elseif kind=27 then (,表达式) begin scanner;j:=exp(28+sys); if kind=28 then scanner else error(22); fact:=j; end; test(sys,27,23); end; begin 项 t1place:=fact(sys+3,36,37); div,*,/ while kind in 3,36,37 do begin mulop:=kind;scanner; t2place:=fact(sys+3,36,37); t:=newtemp; if mulop=36 then gen(mul,t1place,t2place,t) else gen(did,t1place,t2place,t); t1place:=t; end; term:=t1place; end; begin 表达式 if kind in 32,33 then 单目+or- begin addop:=kind;scanner; e1place:=term(sys+34,35); 双目+or- if addop=33 then begin t:=newtemp; gen(umi,e1place,0,t);e1place:=t; end end else e1place:=term(sys+34,35); while kind in 34,35 do begin addop:=kind;scanner; e2place:=term(sys+34,35); t:=newtemp; if addop=34 then gen(add,e1place,e2place,t) else gen(sub,e1place,e2place,t); e1place:=t; end; exp:=e1place; end; procedure condition(var tc,fc:integer;sys:symset); 条件表达式处理 var cond1,cond2,relop:integer; begin cond1:=exp(38,43+sys); if not(kind in 38,43) then begin error(20);scanner end else begin relop:=kind;scanner; cond2:=exp(38,43+sys); tc:=cp; case relop of 38:gen(jeq,cond1,cond2,0); 39:gen(jlt,cond1,cond2,0); 40:gen(jgt,cond1,cond2,0); 41:gen(jne,cond1,cond2,0); 42:gen(jle,cond1,cond2,0); 43:gen(jge,cond1,cond2,0); end;fc:=cp; gen(jmp,0,0,0); end end; begin if kind=21 then 赋值语句 begin i:=entry(id); if i=0 then begin error(11);scanner end else if tablei.cat 18 then if tablei.cat=7 then k:=0 else begin error(12);i:=0 end 把赋值给常量错 else begin j:=lev-tablei.level; k:=100*j+tablei.addr end; scanner; if kind=44 then := begin scanner; place:=exp(sys);gen(ass,place,0,k); schain:=0; end else error(13); end else if kind =8 then begin scanner;condition(ttc,ffc,sys+16); if kind=16 then begin scanner; bp(ttc,nxq); statement(slchain,sys); end else error (16); if kind=5 then begin scanner; q:=nxq;gen(jmp,0,0,0);bp(ffc,nxq); slchain:=merg(slchain,q); statement(s2chain,sys); end else schain:=merg(ffc,slchain); end else if kind=19 then begin scanner; q:=nxq;condition(ttc,ffc,sys+4); if kind=4 then do begin scanner; bp(ttc,nxq); statement(slchain,sys); bp(slchain,q);gen(jmp,0,0,q); schain:=ffc; end else error(18); end else if kind =1 then begin scanner;statement(schain,sys); while kind=24 do ; begin scanner;bp(schain,nxq); statement(schain,sys); end; if kind=6 then end begin scanner;bp(schain,nxq);schain:=0 end else error(17); expected end end else if kind=14 then read 语句 begin scanner; if kind 27 then error(14) else begin scanner; if kind=21 then begin i:=entry(id);j:=tablei.level; k:=tablei.addr;q:=j*100+k; gen(inp,0,0,q);scanner; while kind=23 do , begin scanner; if kind =21 then begin i:=entry(id);j:=tablei.level; k:=tablei.addr;q:=j*100+k; gen(inp,0,0,q) end else error(4); scanner; end; if kind=28 then scanner else error(22) ) end else error(4); end; schain:=0; end else if kind=20 then write 语句 begin scanner; if kind27 then error(14) else repeat scanner; place:=exp(28,23+sys); gen(out,0,0,place); until kind23; if kind28 then error(22); scanner;schain:=0 end; test(sys,19); 空语句自动匹配 end; begin blk 分程序处理 dp:=5;tp0:=tp;tabletp.addr:=cp;cp0:=cp; gen(jmp,0,0,0); 跳过函数说明的语句体代码 if kind=27 then ( 处理形参说 明 begin scanner; vardec; while kind=23 do , begin scanner;vardec; end; if kind=25 then begin scanner; if(kind=9) or (kind=15) then scanner else error(25); end; if kind=28 then scanner else error(22); ) end; if kind=25 then : begin scanner; if(kind=9) or (kind=15) then scanner else error(25); end; type is integer or real? if kind=24 then scanner else error(5); ; if kind=2 then const 处理常量说明 begin scanner; repeat scanner; while kind=23 do , begin scanner;constdec end; if kind=24 then scanner else error(5) ; until kind21; end; if kind=18 then var 处理变量说明 begin scanner; repeat vardec; while kind=23 do , begin scanner;vardec end; if kind=25 then : begin scanner; if(kind=9) or (kind=15) then scanner else error(25) end; integer or real if kind=24 then scann