[jdk19] RFR: 8290250: Shenandoah: disable Loom for iu mode

[Zhengyu Gu]

On Wed, 13 Jul 2022 18:39:51 GMT, Zhengyu Gu <zgu at openjdk.org> wrote:

> Please review this trivial patch to disable Loom for Shenandoah iu mode (an experimental feature).
> 
> Test:
> - [x] hotspot_gc_shenandoah
> - [x] jdk_loom with Shenandoah + iu
> - [x] hotspot_loom with Shenandoah + iu

> _Mailing list message from [Erik Osterlund](mailto:erik.osterlund at oracle.com) on [shenandoah-dev](mailto:shenandoah-dev at mail.openjdk.org):_
> 
> Hi Zhengyu,
> 
> I suppose requires_barriers needs to return true when marking is active with IU, as you need barriers even on newly allocated objects then, as I was discussing.
> 
> /Erik

Tried that, still not working.
I can not see how it can be Loom specific? but seems it's only exposed by `Skynet`

Thanks,

-Zhengyu

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PR: https://git.openjdk.org/jdk19/pull/140