[Bug c++/78655] gcc doesn't exploit the fact that the result of pointer addition can not be nullptr

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78655

--- Comment #7 from Richard Biener <rguenth at gcc dot gnu.org> ---
Note the original testcase is already optimized with GCC 8 due to the fix for
PR35878 and enabling it for all standard modes.