[Bug middle-end/111446] genmatch should warn/error out on recusive match patterns

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111446

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #1)
> Note originally I intended to have (match (...)) inlined in the match IL
> itself,
> so any such checking should not only check for direct recursion but indirect
> as well - all SCCs are unsupported.
> 
> (match (one @0)
>  (negate @0))
> 
> (match (zero @0)
>  (negate (one @0)))
> 
> (match (one @0)
>  (negate (zero @0)))

Yes I guess the easiest/best way to implement this is to walk the predicate
definitions to make sure they don't loop back.