8277654: Shenandoah: Don't produce new memory state in C2 LRB runtime call

[rkennke]

The runtime call in expanded Shenandoah LRB doesn't need to produce (and consume) raw memory state. I believe this is a left-over from when the LRB (or WB) allocated from TLABs, and would mess with TLAB pointers, when not ordered correctly. (Also, we used to require ordering with RBs back when we had them, but we already removed that memory dependency on -8 offset)

Testing:

• hotspot_gc_shenandoah
• specjvm -XX:+UseShenandoahGC
• tier1
• tier2
• tier3

---

Progress

• Change must not contain extraneous whitespace
• Commit message must refer to an issue
• Change must be properly reviewed

Issue

• JDK-8277654: Shenandoah: Don't produce new memory state in C2 LRB runtime call

Reviewers

• Roland Westrelin (@rwestrel - Reviewer)
• Aleksey Shipilev (@shipilev - Reviewer)

Reviewing

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Checkout this PR locally:
$ git fetch https://git.openjdk.java.net/jdk pull/6526/head:pull/6526
$ git checkout pull/6526

Update a local copy of the PR:
$ git checkout pull/6526
$ git pull https://git.openjdk.java.net/jdk pull/6526/head

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Checkout this PR locally:
$ git pr checkout 6526

View PR using the GUI difftool:
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https://git.openjdk.java.net/jdk/pull/6526.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:

• hotspot-gc
• shenandoah

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[mlbridge]

Webrevs

• 01: Full - Incremental (06c2b9eb)
• 00: Full (294389df)

[rwestrel]

Looks good to me.

[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:

8277654: Shenandoah: Don't produce new memory state in C2 LRB runtime call

Reviewed-by: roland, shade

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 80 new commits pushed to the master branch:

• 05ab176: 8277797: Remove undefined/unused SharedRuntime::trampoline_size()
• ad51d06: 8277789: G1: G1CardSetConfiguration prefixes num_ and max_ used interchangeably
• 614c6e6: 8277878: Fix compiler tests after JDK-8275908
• 960bdde: 8277904: G1: Remove G1CardSetArray::max_entries
• 45e8973: 8277896: Remove unused BOTConstants member methods
• e5676f8: 8277450: Record number of references into collection set during gc
• 2622ab3: 8277928: Fix compilation on macosx-aarch64 after 8276108
• 37de442: 8275241: Unused ArrayList is created in RequestEngine.addHooks
• 72bacf8: 8276108: Wrong instruction generation in aarch64 backend
• e3e5908: 8277847: Support toolGuide tag in class-level documentation
• ... and 70 more: https://git.openjdk.java.net/jdk/compare/32839ba012f0a0a66e249cd8d12b94499d82ec0a...master

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.

➡️ To integrate this PR with the above commit message to the master branch, type /integrate in a new comment.

[shipilev]

Looks okay. Does it affect performance in any way?

[rkennke]

Looks okay. Does it affect performance in any way?

I couldn't see any benefits or regressions in specjvm.

[rkennke]

/integrate

[openjdk]

Going to push as commit 3d39f09.
Since your change was applied there have been 80 commits pushed to the master branch:

• 05ab176: 8277797: Remove undefined/unused SharedRuntime::trampoline_size()
• ad51d06: 8277789: G1: G1CardSetConfiguration prefixes num_ and max_ used interchangeably
• 614c6e6: 8277878: Fix compiler tests after JDK-8275908
• 960bdde: 8277904: G1: Remove G1CardSetArray::max_entries
• 45e8973: 8277896: Remove unused BOTConstants member methods
• e5676f8: 8277450: Record number of references into collection set during gc
• 2622ab3: 8277928: Fix compilation on macosx-aarch64 after 8276108
• 37de442: 8275241: Unused ArrayList is created in RequestEngine.addHooks
• 72bacf8: 8276108: Wrong instruction generation in aarch64 backend
• e3e5908: 8277847: Support toolGuide tag in class-level documentation
• ... and 70 more: https://git.openjdk.java.net/jdk/compare/32839ba012f0a0a66e249cd8d12b94499d82ec0a...master

Your commit was automatically rebased without conflicts.

[openjdk]

@rkennke Pushed as commit 3d39f09.

💡 You may see a message that your pull request was closed with unmerged commits. This can be safely ignored.