[Bug middle-end/80917] missed bit information propagation

[glisse at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80917

--- Comment #2 from Marc Glisse <glisse at gcc dot gnu.org> ---
For this special case, we could simplify

  a_6 = a_5(D) + 4;
  _2 = a_6 & 2;

to

  _2 = a_5(D) & 2;

I believe we already have a similar transform with | 4 instead of + 4.