[Bug middle-end/54571] Missed optimization converting between bit sets

["pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=54571

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #1)
> Confirmed.  The natural place to optimize this is the tree level phiopt pass.
> 
>   <bb 2>:
>   _3 = x_2(D) & 2;
>   if (_3 != 0)
>     goto <bb 3>;
>   else
>     goto <bb 4>;
> 
>   <bb 3>:
>   y_5 = y_4(D) | 1;
> 
>   <bb 4>:
>   # y_1 = PHI <y_4(D)(2), y_5(3)>
> 
> where we should handle
> 
> int f1(int x, int y, int d) { int tem; if ((tem = x & d)) y |= tem; return
> y; }
> 
> as well.  Yes, that's just y |= x & d, but it falls out naturally if the
> transform is implemented in a generic enough way.


This one should be easy to add to match.pd:

(simplify
 (cond @1 (ior @2 INTEGER_CST@3) @2)
 (ior @2 (bit_and (negate (convert @1)) @3)))


(bit_and (negate (convert thurth_value@1)) integer_onep)
should be just converted to:
@1
Which is not done right now, I fill that as a bug.