Implement ShenandoahHeap::requires_barriers()

[rkennke]

This add proper implementation of requires_barriers() for ShenandoahHeap, and adds some comments to CollectedHeap about it.

Testing (with a few other fixes in the pipeline):

• java/lang/Continuation (-XX:+UseShenandoahGC -XX:ShenandoahGCMode=aggressive)
• java/lang/Thread/virtual (-XX:+UseShenandoahGC -XX:ShenandoahGCMode=aggressive)

---

Progress

• Change must not contain extraneous whitespace

Reviewers

• Ron Pressler (@pron - Reviewer)

Download

$ git fetch https://git.openjdk.java.net/loom pull/29/head:pull/29
$ git checkout pull/29

[bridgekeeper]

👋 Welcome back rkennke! A progress list of the required criteria for merging this PR into fibers 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 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:

Implement ShenandoahHeap::requires_barriers()

Reviewed-by: rpressler

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

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[mlbridge]

Webrevs

• 01: Full - Incremental (1095d76)
• 00: Full (a5e9003)

[rkennke]

/integrate

[openjdk]

@rkennke
Your change (at version 1095d76) is now ready to be sponsored by a Committer.

[pron]

/sponsor

[openjdk]

@pron @rkennke Pushed as commit 026a3eb.

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