Example 8: An example to illustrate assembly level alias analysis (source C code)


#include <stdlib.h>

void foo(int **x, int **y)
{
    *x = malloc(sizeof(int));
    **x = 2;
    *y = *x;
    return;
}

int a = 0, b = 1;
void main(void)
{
    int *p,*q,*r;
    int t[10]; /* temperal variable */

    p = &a;
    q = &b;
    r = p;
    /* before foo(): p and r point to the same memory location */
    foo(&p, &q);
    /* after foo(): p and q point to the same memory location */    

    /* test RAR and common sub-expression elimination */
    t[0] = *p;
    t[1] = *q;
    t[2] = *r;
    t[3] = *p;

    /* test WAR */
    *p = 10;

    /* test RAW */
    t[4] = *p;
    t[5] = *q;
    t[6] = *r;

    /* test WAW */
    *p = 11;
    *q = 12;
    *r = 13;
    return;
}