[Bug middle-end/113574] wrong code with shift and _BitInt(1) at any opt level

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113574

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Note I was thinking I might hit this with 1 sized bit field but that seems to
work:
```
struct f
{
  unsigned ub1:1;
}t;
void
foo(unsigned short ub16)
{
  t.ub1 = (ub16 << 2);
}
int
main(void)
{
  unsigned short t2 = 0xfef1;
  foo(t2);
  if (t.ub1)
    __builtin_abort();
  return 0;
}
```