8305895: Implementation: JEP 450: Compact Object Headers (Experimental)

[rkennke]

WIP, in favor of #13961

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Progress

• Change must be properly reviewed (1 review required, with at least 1 Reviewer)
• Change must not contain extraneous whitespace
• Commit message must refer to an issue
• Change requires CSR request JDK-8306000 to be approved

Integration blockers

 ⚠️ Too few reviewers with at least role reviewer found (have 0, need at least 1) (failed with updated jcheck configuration in pull request)
 ⚠️ Whitespace errors (failed with updated jcheck configuration in pull request)

Issues

• JDK-8305895: Implementation: JEP 450: Compact Object Headers (Experimental) (Enhancement - P4)
• JDK-8306000: Add experimental -XX:+UseCompactObjectHeaders flag (CSR)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk.git pull/17872/head:pull/17872
$ git checkout pull/17872

Update a local copy of the PR:
$ git checkout pull/17872
$ git pull https://git.openjdk.org/jdk.git pull/17872/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 17872

View PR using the GUI difftool:
$ git pr show -t 17872

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk/pull/17872.diff

[bridgekeeper]

👋 Welcome back rkennke! 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]

@rkennke The following labels will be automatically applied to this pull request:

• core-libs
• graal
• hotspot
• serviceability
• shenandoah

When this pull request is ready to be reviewed, an "RFR" email will be sent to the corresponding mailing lists. If you would like to change these labels, use the /label pull request command.

[openjdk]

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

[openjdk]

@rkennke this pull request can not be integrated into master 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 8305895-v3
git fetch https://git.openjdk.org/jdk.git master
git merge FETCH_HEAD
# resolve conflicts and follow the instructions given by git merge
git commit -m "Merge master"
git push

[rkennke]

Will re-open when ready in Lilliput