[Bug tree-optimization/116768] [12/13/14/15 regression] Strict aliasing breaks autovectorization with -O3

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116768

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Here is a testcase which does NOT need -mavx to fail and fails on aarch64 too:
```
#define numwords 2
typedef struct {
  unsigned words[numwords];
} Child;

typedef struct {
  Child child;
} Parent;

Parent my_or(Parent x, const Parent *y) {
  const Child *y_child = &y->child;
  for (int i = 0; i < numwords; i++) {
    x.child.words[i] |= y_child->words[i];
  }
  return x;
}

int main() {
  Parent bs[4];
  __builtin_memset(bs, 0, sizeof(bs));

  bs[0].child.words[0] = 1;
  for (int i = 1; i <= 3; i++) {
    bs[i] = my_or(bs[i], &bs[i - 1]);
  }
  return bs[2].child.words[0];
}
```