8377171: [lworld] Comment warnings for internal valhalla annotations

[liach]

Add some warning comments for value-related annotations in jdk.internal, to discourage their misuse.

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Progress

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Issue

• JDK-8377171: [lworld] Comment warnings for internal valhalla annotations (Enhancement - P4)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/valhalla.git pull/2023/head:pull/2023
$ git checkout pull/2023

Update a local copy of the PR:
$ git checkout pull/2023
$ git pull https://git.openjdk.org/valhalla.git pull/2023/head

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$ git pr checkout 2023

View PR using the GUI difftool:
$ git pr show -t 2023

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Download this PR as a diff file:
https://git.openjdk.org/valhalla/pull/2023.diff

Using Webrev

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[bridgekeeper]

👋 Welcome back liach! A progress list of the required criteria for merging this PR into lworld will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

[openjdk]

❗ This change is not yet ready to be integrated.
See the Progress checklist in the description for automated requirements.

[mlbridge]

Webrevs

• 01: Full - Incremental (6a3ed516)
• 00: Full (c710005d)

[merykitty]

I think there is no need to discourage usages of these annotations more than the fact that they are internal APIs. Furthermore, it is also really helpful when people use them experimentally, which can help us uncover implementation issues with these configurations.

[liach]

These annotations only promise the performance features from the JVM and has nothing to do with the future language semantics proposed by project Valhalla. I think the warnings I added are adequate about how they are not going to correspond to future Java language features.

[merykitty]

Your reasoning implies that internal annotations somehow often corresponds to future language semantics, which is not the case.

[bridgekeeper]

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