Untitled

Why does __sync_add_and_fetch work for a 64 bit variable on a 32 bit system?
value = dest;
While(!CAS8B(&dest,value,value + 1))
{
    value = dest;
}

oldValue = *dest;
do {
    newValue = oldValue+1;
} while (!compare_and_swap(dest, &oldValue, newValue));

bool compare_and_swap (int *dest, int *oldVal, int newVal)
{
  do atomically {
    if ( *oldVal == *dest ) {
        *dest = newVal;
        return true;
    } else {
        *oldVal = *dest;
        return false;
    }
  }
}