[Bug rtl-optimization/57359] wrong code for union access at -O3 on x86_64-linux

[dhazeghi at yahoo dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57359

--- Comment #8 from Dara Hazeghi <dhazeghi at yahoo dot com> ---
Okay, here is I think a more clear example.  However, from what Jakub says
above, this is probably undefined.

int printf(const char *, ...);

union
{
    int i;
    long long ll;
} u;

long long *pll =  &u.ll;
int *pi = &u.i;

int a = 1, *pa = &a;

void
foo ()
{
    int i = 0;
    for (; i <= 1; i++)
    {
        *pll = a;
        *pi = 0;
        a = *pa;
    }
}

int
main ()
{
    foo ();
    printf ("%d\n", u.i);
    return 0;
}