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

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

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

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
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)))