code optimization techniques: a)strength reduction b) constant folding

### tac.txt #####
1 sq b - c
2 * 2 c c
3 := c - res
4 + a b no1
5 - res no1 res
6 + 3 5 pi
7 := pi - x
8 / x 2 res1

##### pr_11a.c ######

/*

10) WAP to implement following code optimization techniques:

a)strength reduction   b) constant folding

*/

#include<stdio.h>

struct holder

{

char seqno[3],op[3],arg1[8],arg2[8],result[8];

}tac[50];

int cnt=0,i,j,k;

char hunted[8];

int is_const(char arg[8])

{

for(j=0;j<strlen(arg);j++)

if(!isdigit(arg[j]))

return(0);

return(1);

}

void strength_red()

{

//check * sign and try to replace it by + and sq by *

for(i=0;i<cnt;i++)

{

if(strcmp(tac[i].op,"*")==0)

{

if(atoi(tac[i].arg1)==2 && !(is_const(tac[i].arg2)) )

{

strcpy(tac[i].op,"+");

strcpy(tac[i].arg1,tac[i].arg2);

}

else if(atoi(tac[i].arg2)==2 && !(is_const(tac[i].arg1)))

{

strcpy(tac[i].op,"+");

strcpy(tac[i].arg2,tac[i].arg1);

}

}

if(strcmp(tac[i].op,"/")==0 && atoi(tac[i].arg2)==2)

{

strcpy(tac[i].op,"*");

strcpy(tac[i].arg2,"0.5");

}

if(strcmp(tac[i].op,"sq")==0)

{

strcpy(tac[i].op,"*");

strcpy(tac[i].arg2,tac[i].arg1);

}

}

}

void const_folding()

{

//hunt var1 = const +/-/*// const and then  insted of arg1 place result replece const

int val=0;

for(i=0;i<cnt;i++)

{

if(is_const(tac[i].arg1)&&is_const(tac[i].arg2))

{

if(strcmp("+",tac[i].op)==0)

sprintf(tac[i].arg1,"%d",atoi(tac[i].arg1)+atoi(tac[i].arg2));

if(strcmp("-",tac[i].op)==0)

sprintf(tac[i].arg1,"%d",atoi(tac[i].arg1)-atoi(tac[i].arg2));

if(strcmp("*",tac[i].op)==0)

sprintf(tac[i].arg1,"%d",atoi(tac[i].arg1)*atoi(tac[i].arg2));

if(strcmp("/",tac[i].op)==0)

sprintf(tac[i].arg1,"%d",atoi(tac[i].arg1)/atoi(tac[i].arg2));

sprintf(tac[i].arg2,"-");

sprintf(tac[i].op,":=");

}

} 

}

int main()

{

FILE * fin =fopen("tac.txt","r");

int i;

while(!feof(fin))

{

fscanf(fin,"%s%s%s%s%s",tac[cnt].seqno,tac[cnt].op,tac[cnt].arg1,tac[cnt].arg2,tac[cnt].result);

cnt++;

}

cnt--;

printf("\n\t\t*** $$ PURE INPUT $$ ****");

printf("\n\tIndex\tOP\tArg1\tArg2\tResult");

for(i=0;i<cnt;i++)

{

printf("\n\t%s\t%s\t%s\t%s\t%s",tac[i].seqno,tac[i].op,tac[i].arg1,tac[i].arg2,tac[i].result);

}

strength_red();

const_folding();

printf("\n\t\t*** After Process ****");

printf("\n\tIndex\tOP\tArg1\tArg2\tResult");

for(i=0;i<cnt;i++)

{

printf("\n\t%s\t%s\t%s\t%s\t%s",tac[i].seqno,tac[i].op,tac[i].arg1,tac[i].arg2,tac[i].result);

}

fclose(fin);

}

#### output #####

pr@prashant-HP:~/LEX&YACC/11$ cc pr_11a.c

pr@prashant-HP:~/LEX&YACC/11$ ./a.out

*** $$ PURE INPUT $$ ****

Index OP Arg1 Arg2 Result

1 sq b - c

2 * 2 c c

3 := c - res

4 + a b no1

5 - res no1 res

6 + 3 5 pi

7 := pi - x

8 / x 2 res1

*** After Process ****

Index OP Arg1 Arg2 Result

1 * b b c

2 + c c c

3 := c - res

4 + a b no1

5 - res no1 res

6 := 8 - pi

7 := pi - x

8 * x 0.5 res1pr@prashant-HP:~/LEX&YACC/11$