8349162: [lworld] VM Flags controlling flattening need an update

[fparain]

This patch is mostly about VM flags update and internal renaming.

Renaming a few symbols to make them consistent with previous code cleanup:

• data_for_oop() -> payload_address()
• first_field_offset() -> payload_offset()
• LayoutKind::PAYLOAD -> LayoutKind::BUFFERED (it is only used to describe layout in buffered values, and it makes it an adjective like the other LayoutKind values)

VM flags controlling flattening:

• size based VM flags are removed: FlatArrayElementMaxSize, InlineFieldMaxFlatSize. For now, FlatArrayElementMaxOops is still present because some compiler tests rely on it, but it will be removed eventually
• InlineArrayAtomicAccess has been removed, use AlwaysAtomicAccesses instead
• new VM flags to control the generation of the new layouts: NonAtomicValueFlattening, AtomicValueFlattening, NullableValueFlattening. Note that that those flags control the generation of the layouts, not the way they are used (see flags below)
• new VM flags to control use of flat layouts: UseFlatField, UseFlatArray

Example:
To enable flattening of nullable fields, the flag combination is -XX:+NullableValueFlattening -XX:+UseFlatField

The new VM flags controlling flattening are flags for testing or troubleshooting (they should probably be turned into DIAGNOSTIC flags before preview). They are not designed for performance tuning.

Feel free to propose new names for those flags if you think they are not explicit enough.

Thank you,

Fred

---

Progress

• Change must not contain extraneous whitespace

Issue

• JDK-8349162: [lworld] VM Flags controlling flattening need an update (Bug - P3)

Reviewers

• Tobias Hartmann (@TobiHartmann - Committer)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/valhalla.git pull/1345/head:pull/1345
$ git checkout pull/1345

Update a local copy of the PR:
$ git checkout pull/1345
$ git pull https://git.openjdk.org/valhalla.git pull/1345/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 1345

View PR using the GUI difftool:
$ git pr show -t 1345

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/valhalla/pull/1345.diff

Using Webrev

Link to Webrev Comment

[bridgekeeper]

👋 Welcome back fparain! 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]

@fparain This change now passes all automated pre-integration checks.

ℹ️ This project also has non-automated pre-integration requirements. Please see the file CONTRIBUTING.md for details.

After integration, the commit message for the final commit will be:

8349162: [lworld] VM Flags controlling flattening need an update

Reviewed-by: thartmann

You can use pull request commands such as /summary, /contributor and /issue to adjust it as needed.

At the time when this comment was updated there had been no new commits pushed to the lworld branch. If another commit should be pushed before you perform the /integrate command, your PR will be automatically rebased. If you prefer to avoid any potential automatic rebasing, please check the documentation for the /integrate command for further details.

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[openjdk]

@fparain this pull request can not be integrated into lworld due to one or more merge conflicts. To resolve these merge conflicts and update this pull request you can run the following commands in the local repository for your personal fork:

git checkout renaming
git fetch https://git.openjdk.org/valhalla.git lworld
git merge FETCH_HEAD
# resolve conflicts and follow the instructions given by git merge
git commit -m "Merge lworld"
git push

[mlbridge]

Webrevs

• 05: Full (958de774)
• 04: Full - Incremental (74b55a39)
• 03: Full (cc2eab84)
• 02: Full - Incremental (c8ca53a8)
• 01: Full - Incremental (ee8a2fd0)
• 00: Full (f42da7fb)

[TobiHartmann]

Just a quick drive-by comment: Java code should use 4-whitespace indentation. Same for other files.

[fparain]

After a discussion with Tobias, we agreed on a more consistent scheme for flags names:

• UseFlatArray -> UseArrayFlattening
• UseFlatField -> UseFieldFlattening
• NonAtomicValueFlattening -> UseNonAtomicValueFlattening
• AtomicValueFlattening -> UseAtomicValueFlattening
• NullableValueFlattening -> UseNullableValueFlattening

[TobiHartmann]

Looks good!

[fparain]

Thank you for the reviews.

[fparain]

/integrate

[openjdk]

Going to push as commit 9786bf3.

[openjdk]

@fparain Pushed as commit 9786bf3.

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