RFR: 8308088: Improve class check in CollectedHeap::is_oop

[Zhengyu Gu]

On Mon, 15 May 2023 10:25:15 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> See the bug for more details.
> 
> Additional testing:
>  - [x] Linux x86_64 fastdebug, `tier1`
>  - [x] Linux x86_64 fastdebug, `tier2`
>  - [x] Linux x86_64 fastdebug, `tier3`

Wait, you are calling `k->is_klass()` here, you do need `acquire` here.

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Changes requested by zgu (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/13982#pullrequestreview-1427289394