8366441: AArch64: Support WFET in OnSpinWait

[ruben-arm]

Hi,

This is a backport of 8366441: AArch64: Support WFET in OnSpinWait (openjdk/jdk#27030)

There is a difference from the original commit - in the test/hotspot/gtest/aarch64/asmtest.out.h file generated using aarch64-asmtest.py.

Testing:

• fastdebug test/hotspot/jtreg/compiler/onSpinWait/TestOnSpinWaitAArch64.java on Arm Cortex-X925 and Arm Neoverse V2 cores
• release and fastdebug hotspot tier1, tier2, tier3 - on AArch64, x86_64

Thank you,
Ruben

---

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---

Progress

• Change must not contain extraneous whitespace
• Commit message must refer to an issue
• JDK-8366441 needs maintainer approval

Issue

• JDK-8366441: AArch64: Support WFET in OnSpinWait (Enhancement - P4 - Requested)

Reviewers

• Andrew Haley (@theRealAph - Reviewer)

Reviewing

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Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk26u.git pull/209/head:pull/209
$ git checkout pull/209

Update a local copy of the PR:
$ git checkout pull/209
$ git pull https://git.openjdk.org/jdk26u.git pull/209/head

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Checkout this PR locally:
$ git pr checkout 209

View PR using the GUI difftool:
$ git pr show -t 209

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Download this PR as a diff file:
https://git.openjdk.org/jdk26u/pull/209.diff

Using Webrev

Link to Webrev Comment

[bridgekeeper]

👋 Welcome back ruben-arm! 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.

[openjdk]

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

[mlbridge]

Webrevs

• 00: Full (b2a951f0)

[ruben-arm]

/approval request The motivation behind backporting is performance improvement related to Thread.onSpinWait - specific data on improvements is available at openjdk/jdk#27030 (in comment added on 5 February).
This doesn't change the behaviour unless a respective command line option is supplied, therefore is expected to be a low risk.

[openjdk]

@ruben-arm
8366441: The approval request has been created successfully.

[bridgekeeper]

@ruben-arm 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 issue a /touch or /keepalive command to the pull request. Feel free to ask for assistance if you need help with progressing this pull request towards integration!

[ruben-arm]

/keepalive

[openjdk]

@ruben-arm The pull request is being re-evaluated and the inactivity timeout has been reset.