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

[Roland Westrelin]

> It reverts the part back to original jdk11 upstream because we no longer
> need to insert into the control flow there. Is that not ok?

Ah ok. That change is good.

>> cfgnode.hpp
>> 
>> That change doesn't seem needed
>
> Are you sure? We do have a corresponding call to step_over_gc_barrier()
> in jdk/jdk too.
>
> http://hg.openjdk.java.net/jdk/jdk/file/ce8bab2c4185/src/hotspot/share/opto/cfgnode.cpp#l1451

cfgnode.*h*pp

The following change which removes:

306   Node* dominated_by(Node* prev_dom, PhaseIterGVN* igvn);

and adds it back:

393   Node* dominated_by(Node* prev_dom, PhaseIterGVN* igvn);


Roland.