Can a struct alias its own initial and only member?

For example, is this code valid, or does it invoke undefined behavior by violating the aliasing rules?

int x;
struct s { int i; } y;
x = 1;
y = *(struct s *)&x;
printf("%d\n", y.i);

My interest is in using a technique based on this to develop a portable method for performing aliased reads.

Update: here is the intended usage case, a little bit different, but it should be valid if and only if the above is valid:

static inline uint32_t read32(const unsigned char *p)
{
    struct a { char r[4]; };
    union b { struct a r; uint32_t x; } tmp;
    tmp.r = *(struct a *)p;
    return tmp.x;
}

GCC, as desired, compiles this to a single 32-bit load, and it seems to avoid the aliasing issues that could happen if p actually points to a type other than char. In other words, it seems to act as a portable replacement for the GNU C __attribute__((__may_alias__)) attribute. But I'm uncertain whether it's really well-defined...