8263375: Support stack watermarks in Zero VM

[shipilev]

Zero VM supports most of GCs. Since JDK 16, Shenandoah uses stack watermarks, so Zero has to support those if Shenandoah+Zero support is to remain. This PR adds the stack watermark support in Zero VM. This should also be useful as other projects, notably Loom, mature and depend on stack watermarks.

Zero already calls into Hotspot safepoint machinery to do things, and it seems only the hooks for on_iteration and on_unwind are missing. AFAICS, Zero only has on-return safepoints, renamed it to be more precise.

@fisk, do you see any obvious problems with this patch?

Additional testing:

• Linux x86_64 Zero hotspot_gc_shenandoah now passes

---

Progress

• Change must not contain extraneous whitespace
• Commit message must refer to an issue
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Issue

• JDK-8263375: Support stack watermarks in Zero VM

Reviewers

• Erik Österlund (@fisk - Reviewer)

Reviewing

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Checkout this PR locally:
$ git fetch https://git.openjdk.java.net/jdk pull/4728/head:pull/4728
$ git checkout pull/4728

Update a local copy of the PR:
$ git checkout pull/4728
$ git pull https://git.openjdk.java.net/jdk pull/4728/head

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Checkout this PR locally:
$ git pr checkout 4728

View PR using the GUI difftool:
$ git pr show -t 4728

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Download this PR as a diff file:
https://git.openjdk.java.net/jdk/pull/4728.diff

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[openjdk]

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[mlbridge]

Webrevs

• 01: Full - Incremental (d809aad2)
• 00: Full (d68b31a8)

[fisk]

Looks good in general, would just like slightly more precise hooks as explained in a comment above. It will probably work without that though.

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[fisk]

Looks good.

[openjdk]

@shipilev 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:

8263375: Support stack watermarks in Zero VM

Reviewed-by: eosterlund

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

At the time when this comment was updated there had been 3 new commits pushed to the master branch:

• 02822e1: 8272377: assert preconditions that are ensured when created in add_final_edges
• a58cf16: 8272563: assert(is_double_stack() && !is_virtual()) failed: type check
• 0e14bf7: 8273176: handle latest VS2019 in abstract_vm_version

Please see this link for an up-to-date comparison between the source branch of this pull request and the master branch.
As there are no conflicts, your changes will automatically be rebased on top of these commits when integrating. If you prefer to avoid this automatic rebasing, please check the documentation for the /integrate command for further details.

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[shipilev]

Thanks, @fisk! I suppose there are no other interested parties for this kind of patch, so I'll integrate this soon.

[shipilev]

/integrate

[openjdk]

Going to push as commit 857a930.
Since your change was applied there have been 11 commits pushed to the master branch:

• 6cfe314: 8272970: Parallelize runtime/InvocationTests/
• a9a83b2: 8273256: runtime/cds/appcds/TestEpsilonGCWithCDS.java fails due to Unrecognized VM option 'ObjectAlignmentInBytes=64' on x86_32
• 1a5a2b6: 8271745: Correct block size for KW,KWP mode and use fixed IV for KWP mode for SunJCE
• 2f01a6f: 8273157: Add convenience methods to Messager
• 9689f61: 8272788: Nonleaf ranked locks should not be safepoint_check_never
• 4ee0dac: 8273248: ProblemList java/lang/instrument/BootClassPath/BootClassPathTest.sh on all configs
• 655ea6d: 8270489: Support archived heap objects in EpsilonGC
• dacd197: 8273217: Make ParHeapInspectTask _safepoint_check_never
• 02822e1: 8272377: assert preconditions that are ensured when created in add_final_edges
• a58cf16: 8272563: assert(is_double_stack() && !is_virtual()) failed: type check
• ... and 1 more: https://git.openjdk.java.net/jdk/compare/f1c5e26e48ca2db0fc2b7ad2cf1bda4853bdeea9...master

Your commit was automatically rebased without conflicts.

[openjdk]

@shipilev Pushed as commit 857a930.

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