[Bug tree-optimization/71336] Suboptimal code generated for "(a & 1) ? (CST1 + CST2) : CST1"

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71336

--- Comment #8 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #6)
> Sorry this one is more correct
> Something like (very much pesdu code):
> (simplify
>  (cond (eq (bit_and@0 @1 int_pow2p@2) integer_zerop) INTEGET_CST@3
> INTEGER_CST@4)
>  (switch
>   (if (@3 u> @4 && exact_pow2(@3 - @4))
>    (convert (plus (mult (rshift @0:typeu @2) (minus @3:typeu @4:typeu))
> @4:typeu)))
>   (if (@4 u> @3 && exact_pow2(@4 - @3))
>    (convert (minus (mult (rshift @0:typeu @2) (minus @4:typeu @3:typeu))
> @3:typeu))
>  ))
> 
> The mult could be changed to lshift to be more correct.

I should note, the above is now only possible because of the recent changes I
did to phi-opt.  You no longer need to open code anything in phi-opt for things
like this bug, just add them to match.pd and be done with it :).