[Bug c/81783] -Wtautological-compare could do better

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81783

--- Comment #2 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
I have a patch, but as usually, there's a problem with constants coming from
macros...