RFR (11): [backport] 8221766: Load-reference barriers for Shenandoah

[Roland Westrelin]

> In jdk11, we don't use it *not yet*. We have sprinkled a bunch of code
> over Ideal() calls to do the things that we do via BSC2::ideal_node() in
> jdk12 and up.
>
> I believe the corresponding code in sh/jdk11 is in ifnode.cpp:
>
> https://builds.shipilev.net/patch-openjdk-shenandoah-jdk11/src/hotspot/share/opto/ifnode.cpp.udiff.html

Ok. Looks good then.

Roland.