[Bug tree-optimization/116648] unswitch does not handle `if (a & b)` where a is invariant

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116648

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
I should say I noticed this while looking into PR 116647.  Fixing this will
almost definitely make PR 116647 latent though.