[Bug tree-optimization/67328] range test rather than single bit test for code testing enum values

[tetra2005 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67328

--- Comment #6 from Yuri Gribov <tetra2005 at gmail dot com> ---
(In reply to Oleg Endo from comment #5)
> PR 67731 maybe related or dup?

Related but not a dup. This bug is caused by frontend folding two bitfield
accesses to a single comparison which prevented generation of bit test later in
tree-opt.