8321308: AArch64: Fix matching predication for cbz/cbnz

[bulasevich]

Clean backport to improve aarch code generation for array length if (a.length > 0)

Testing: jtreg tier1-3 on linux-aarch64.

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Progress

• Change must not contain extraneous whitespace
• Commit message must refer to an issue
• JDK-8321308 needs maintainer approval

Issue

• JDK-8321308: AArch64: Fix matching predication for cbz/cbnz (Enhancement - P4 - Rejected)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk21u-dev.git pull/940/head:pull/940
$ git checkout pull/940

Update a local copy of the PR:
$ git checkout pull/940
$ git pull https://git.openjdk.org/jdk21u-dev.git pull/940/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 940

View PR using the GUI difftool:
$ git pr show -t 940

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk21u-dev/pull/940.diff

Webrev

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[bridgekeeper]

👋 Welcome back bulasevich! A progress list of the required criteria for merging this PR into master 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

• 00: Full (4ee63cfc)

[openjdk]

This backport pull request has now been updated with issue from the original commit.

[openjdk]

⚠️ @bulasevich This change is now ready for you to apply for maintainer approval. This can be done directly in each associated issue or by using the /approval command.

[bulasevich]

/approval request This simple change applies cleanly to jdk21. The change fixes the matching rules to use a single instruction for unsigned comparison and branch, which is also useful for jdk-21.
Testing: tier1-3 on linux-aarch64.

[openjdk]

@bulasevich
8321308: The approval request has been created successfully.

[jerboaa]

We should not backport about anything to JDK 21. Especially when it comes to performance improvements. This P4 enhancement doesn't strike me as anything important enough for a stable update release. Let's be more diligent with performance enhancements. You may consider backporting to 23u.

/approve no

[openjdk]

@jerboaa
8321308: The approval request has been rejected.

[bridgekeeper]

@bulasevich This pull request has been inactive for more than 4 weeks and will be automatically closed if another 4 weeks passes without any activity. To avoid this, simply add a new comment to the pull request. Feel free to ask for assistance if you need help with progressing this pull request towards integration!