[Bug c/59852] Support sparse-style __attribute__((bitwise)) (type attribute)

[josh at joshtriplett dot org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59852

--- Comment #6 from Josh Triplett <josh at joshtriplett dot org> ---
(In reply to Tom Tromey from comment #5)
> (In reply to Josh Triplett from comment #4)
> > Also note that arithmetic operations between a bitwise and a known-zero
> > value do not warn.
> 
> I'm curious about this too.
> If it means that the warnings should be deferred until after
> optimization, then it seems like maybe a difficult problem.
> On the other extreme, if this just refers to constant expressions,
> making this a purely front-end feature, then it seems more tractable.

Sparse does it for constant expressions only, as far as I can tell.