8345995: [lworld] Flat arrays need to be redesigned to support new flat layouts

[fparain]

Here's a redesign of flat arrays to support multiple flat layouts (NON_ATOMIC_FLAT, ATOMIC_FLAT, NULLABLE_ATOMIC_FLAT). The patch contains a lot of cleanup and simplification of the flat arrays access code.

This patch has been tested in interpreted mode only on both x86_64 and aarch64.

Unfortunately, it currently triggers a number of failures when run with JITs enabled. After a discussion with Tobias, this PR will probably not be integrated until a patch for the JITs is available.

Regards,

Fred

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Progress

• Change must not contain extraneous whitespace

Issue

• JDK-8345995: [lworld] Flat arrays need to be redesigned to support new flat layouts (Enhancement - P3)

Reviewing

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Checkout this PR locally:
$ git fetch https://git.openjdk.org/valhalla.git pull/1315/head:pull/1315
$ git checkout pull/1315

Update a local copy of the PR:
$ git checkout pull/1315
$ git pull https://git.openjdk.org/valhalla.git pull/1315/head

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$ git pr checkout 1315

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[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 is no longer ready for integration - check the PR body for details.

[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 array_ext_hdr
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

• 03: Full - Incremental (048b88c4)
• 02: Full - Incremental (5fe9f5f5)
• 01: Full (962bc4bb)
• 00: Full (57ffb382)