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%{
#include<stdio.h>
#include<string.h>
#include<stdlib.h>
#include<ctype.h>
void apply(char);
void load_num(char);
void load_var(char);
void store_var(char);
int yyerror(char *);
int yylex();
int reg_count=0;
struct instruction {
char op1;
char op2;
char opr;
};
%}
%token IDENT NUM
%type expr
%left '+'
%left '*''/'
%left '-'
%%
statement: IDENT '=' expr ';' { store_var((char)$1); }
;
expr: expr '+' expr {apply('+');}
| expr '-' expr {apply('-');}
| expr '*' expr {apply('*');}
| NUM {load_num((char)$1); $$=(char)$1;}
| IDENT {load_var((char)$1); $$=(char)$1;}
;
%%
void apply(char opr) {
switch(opr) {
case '+':
printf("ADD ");
break;
case '-':
printf("SUB ");
break;
case '*': printf("MUL ");
}
printf("R%d, R%d, R%d\n", reg_count-2, reg_count-2, reg_count-1);
}
void load_num(char num) {
printf("LD R%d, #%c\n", reg_count++, num);
}
void load_var(char var) {
printf("LD R%d, %c\n", reg_count++, var);
}
void store_var(char var) {
printf("ST %c, R%d\n", var, reg_count-1);
}
int yyerror(char *s) {
printf("ERROR: %s",s);
exit(0);
}
int main() {
yyparse();
}
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