C PROGRAM FOR CONSTANT PROPAGATION AND FOLDING

#include<stdio.h>
#include<string.h>
#include<ctype.h>
#include<conio.h>
void input();
void output();
void change(int p,char *res);
void constant();
struct expr
{
char op[2],op1[5],op2[5],res[5];
int flag;
}arr[10];
int n;
void main()
{
clrscr();
input();
constant();
output();
getch();
}
void input()
{
int i;
printf("\n\nEnter the maximum number of  expressions : ");
scanf("%d",&n);
printf("\nEnter the input : \n");
for(i=0;i<n;i++)
{
scanf("%s",arr[i].op);
scanf("%s",arr[i].op1);
scanf("%s",arr[i].op2);
scanf("%s",arr[i].res);
arr[i].flag=0;
}
}
void constant()
{
int i;
int op1,op2,res;
char op,res1[5];
for(i=0;i<n;i++)
{
if(isdigit(arr[i].op1[0]) && isdigit(arr[i].op2[0]) || strcmp(arr[i].op,"=")==0) /*if both digits, store them in variables*/
{
op1=atoi(arr[i].op1);
op2=atoi(arr[i].op2);
op=arr[i].op[0];
switch(op)
{
case '+':
res=op1+op2;
break;
case '-':
res=op1-op2;
break;
case '*':
res=op1*op2;
break;
case '/':
res=op1/op2;
break;
case '=':
res=op1;
break;
}
sprintf(res1,"%d",res);
arr[i].flag=1; /*eliminate expr and replace any operand below that uses result of this expr */
change(i,res1);
}
}
}
void output()
{
int i=0;
printf("\nOptimized code is : ");
for(i=0;i<n;i++)
{
if(!arr[i].flag)
{
printf("\n%s %s %s %s",arr[i].op,arr[i].op1,arr[i].op2,arr[i].res);
}
}
}
void change(int p,char *res)
{
int i;
for(i=p+1;i<n;i++)
{
if(strcmp(arr[p].res,arr[i].op1)==0)
strcpy(arr[i].op1,res);
else if(strcmp(arr[p].res,arr[i].op2)==0)
strcpy(arr[i].op2,res);
}
}
/*
INPUT:

Enter the maximum number of  expressions : 4

Enter the input :
= 3 - a
+ a b t1
+ a c t2
+ t1 t2 t3

OUTPUT:
Optimized code is :
+ 3 b t1
+ 3 c t2
+ t1 t2 t3
*/

C PROGRAM FOR LOOP UNROLLING

/* Loop unrolling, also known as loop unwinding, is a loop transformation technique that 

attempts to optimize a program's execution speed at the expense of its binary size, which is an 

approach known as the space-time tradeoff. The transformation can be undertaken manually by 

the programmer or by an optimizing compiler. */

#include<stdio.h>
#include<conio.h>
void main()
{
unsigned int n;
int x;
char ch;
clrscr();
printf("\nEnter N\n");
scanf("%u",&n);
printf("\n1. Loop Roll\n2. Loop UnRoll\n");
printf("\nEnter ur choice\n");
scanf(" %c",&ch);
switch(ch)
{
case '1':
x=countbit1(n);
printf("\nLoop Roll: Count of  1's    :  %d" ,x);
break;
case '2':
x=countbit2(n);
printf("\nLoop UnRoll:  Count of 1's  :  %d" ,x);
break;
default:
printf("\n Wrong Choice\n");

}
getch();
}
int countbit1(unsigned int n)
{
    int bits = 0,i=0;
    while (n != 0)
    {
if (n & 1) bits++;
n >>= 1;
i++;
    }
    printf("\n no of iterations  %d",i);
    return bits;
}
int countbit2(unsigned int n)
{
    int bits = 0,i=0;
    while (n != 0)
    {
if (n & 1) bits++;
if (n & 2) bits++;
if (n & 4) bits++;
if (n & 8) bits++;
n >>= 4;
i++;
    }
    printf("\n no of iterations  %d",i);
    return bits;
}