[Bug middle-end/66872] fold a & ((1 << b) - 1) to a & ~(-1 << b)

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66872

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2015-07-15
     Ever confirmed|0                           |1

--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> ---
I think we can assume (on gimple) that andn is available and thus
"canonicalize"
to andn form when possible.  The transform at least makes one binary operation
an unary operation.