S6 CSE COMPILER LAB : PARSER FOR INTERMEDIATE CODE GENERATION

                              

       /*  PARSER  FOR INTERMEDIATE CODE GENERATION   */

Yacc program

%{

#include<stdio.h>

#include<stdlib.h>

#include<ctype.h>

#include<string.h>

%}

%token id digit

%left '+''-'

%left '*''/'

%left '^'

%right '='

%nonassoc UMINUS

%%

S:id {push();}'='E {pop();}

E:E'+' {push();}T {pop3();}

  |E'-' {push();}T {pop3();}

  |T

  ;

T:T'*' {push();}F {pop3();}

 |T '/' {push();}F {pop3();}

 |T'^' {push();}F {pop3();}

 |F

 ;

F:id {push();}

 |digit {push();}

 |'('E')'

 |'-' {push();}F {pop2();} %prec UMINUS

 ;

%%

#include "lex.yy.c"

char stack[10][10],var[10]="\0",temp[10]="\0";

int top=0;

char i='0';

int main()

 {

  yyparse();

  yylex();

  return 0;

 }

yyerror(char *s)

 {

  printf("%s\n",s);

 }

push()

{

top++;

strcpy(stack[top],yytext);

}

pop3()

{

 printf("\nt%c=%s%s%s",i,stack[top-2],stack[top-1],stack[top]);

 top=top-2;

 temp[0]=i;

 strcpy(var,"t");

 strcat(var,temp);

 strcpy(stack[top],var);

 i++;

}

pop()

{

 printf("\n%s=%s\n",stack[top-1],stack[top]);

}

pop2()

{

 printf("\nt%c=%s%s",i,stack[top-1],stack[top]);

 top--;

 temp[0]=i;

 strcpy(var,"t");

 strcat(var,temp);

 strcpy(stack[top],var);

i++;

}

Lex program

%{

#include "y.tab.h"

%}

%%

[0-9]+ {return digit;}

[a-z]+ {return id;}

[ \t]  ;

[\n] {return 0;}

.    {return yytext[0];}

%%

 OUTPUT

a=b+c

t0=b+c

a=t0

c=x*y+d

t0=x*y

t1=t0+d

c=t1