Post-merge bug: Derby fails with assert(p != __null) failed: named projection 2 not found

[Roland Westrelin]

Here is a cleaner fix:

http://cr.openjdk.java.net/~roland/shenandoah/find_bottom_mem/webrev.01/

>  1) Is this backportable? I.e. should the same fix go to sh/jdk9 and sh/jdk9?

Yes.

>  2) I see two other mentions of OptoRuntime::rethrow_stub in asserts, should new entry points be
> added there as well?

The asserts are good (because they are CallLeaf nodes).

Roland.