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

[Zhengyu Gu]

On Wed, 1 Jun 2022 16:10:03 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

>> Zhengyu Gu has updated the pull request incrementally with two additional commits since the last revision:
>> 
>>  - Fix
>>  - NMethod::heal_nmethod() does not need to handle ref-update
>
> All right then!

Thanks, @shipilev

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