ShenandoahBarrierSetC2::escape_is_barrier_node

[Roland Westrelin]

Hi Aleksey,

> A question for you. We have a staged code in sh/jdk, which has this change in
> ShenandoahBarrierSetC2::escape_is_barrier_node:
>   http://hg.openjdk.java.net/shenandoah/jdk/rev/3f2b4cc07dbd#l1.47

I think it's fine to keep that change because we remove barriers on
newly allocated objects and that code is for barriers on newly allocated
non escaping objects. The reason we hit AFAICT is:

changeset:   56234:3f2b4cc07dbd
tag:         tip
user:        shade
date:        Thu Jun 06 22:24:23 2019 +0200
summary:     C2 LRB self-fixup

because it adds a new edge to the load barrier and so a path to the
barrier from a newly allocated object even when we don't apply the
barrier to the object itself but to a field loaded from that object.

Actually, I would say it's a left over from when we had an option to not
optimize out barriers on newly allocated objects and has not been needed
for a while.

Roland.