RFR: 8286829: Shenandoah: fix Shenandoah Loom support [v3]

[Stefan Karlsson]

On Wed, 1 Jun 2022 12:28:28 GMT, Zhengyu Gu <zgu at openjdk.org> wrote:

>> Um, this conversation seems to be "resolved" without the answer.
>
> Hmm... somehow, my comments gone missing.
> 
> Yes, I am award of it, but could not find a better place, any suggestions are welcome.
> 
> ZGC takes the similar hit [here](https://github.com/openjdk/jdk/blob/master/src/hotspot/share/gc/z/zMark.cpp#L289).
> 
> Let's get this in for correctness and work on optimizing it in followup CR.
> 
> Thanks.

Both `obj->is_instance()` and `obj->is_stackChunk()` in `relativize_stack_chunk` checks the same Klass::_kind field, so I would be surprised if you would be able to find a perf regression here. We checked the marking times before and  after adding relativize_stack_chunk, and couldn't see any difference.

-------------

PR: https://git.openjdk.java.net/jdk/pull/8924