RFR: 8318776: Require supports_cx8 to always be true [v4]

[David Holmes]

On Tue, 21 Nov 2023 16:58:21 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

>> This looks great!
>
>> Thanks for the review @fisk ! I have to wait for a few Zero related PRs to get integrated then re-merge, before I can integrate.
> 
> Zero patches were pushed, please re-merge. I checked current mainline works well with at least linux-arm-zero-fastdebug, and I would like to re-test it with this patch.

@shipilev  I have re-merged and update the Zero changes (ifdef around `_saupports_cx8`).

@viktorklang-ora and/or @DougLea could I ask you to look at the `java.util.concurrent.AtomicLongFieldUpdater` changes please.

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PR Comment: https://git.openjdk.org/jdk/pull/16625#issuecomment-1821983975