[Bug c/69825] False -Wdiv-by-zero warning when it should be short-circuited

[dgilbert at redhat dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69825

--- Comment #1 from Dr. David Alan Gilbert <dgilbert at redhat dot com> ---
Oops, forgot to mention; this is on fedora 23 x86-64.