[Bug middle-end/64309] if (1 & (1 << n)) not simplified to if (n == 0)

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64309

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |missed-optimization
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2014-12-15
          Component|rtl-optimization            |middle-end
     Ever confirmed|0                           |1

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
Confirmed.  Sth like

 (simplify
  (ne (bit_and (lshift integer_onep @0) integer_onep) integer_zerop)
  (eq @0 { build_zero_cst (TREE_TYPE (@0)); })

with eventually also covering if ((1 & (1<< n)) == 0) -> if (n & 1 == 0)

You can extend this to cover the other cases you mention.