[Bug middle-end/67809] Empty pointer-chasing loops aren't optimized out

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67809

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
And it is not legal to do if you catch other undefined behavior like trapping
on invalid memory locations.