8319777: Zero: Support 8-byte cmpxchg

[shipilev]

See related discussion in JDK-8318776 that targets to require supports_cx8() unconditionally.

I think we can claim Zero is supports_cx8() == true, because we have enough fallbacks for 8-byte CASes to work. Note that some code already reaches for these without checking for supports_cx8(), so the proverbial horses have already left the barn.

I ran tests with JDK-8319883 applied to fix known problems with x86_32 Zero.

Additional testing:

• Linux x86_32 Zero release; jcstress
• Linux x86_32 Zero fastdebug, compiler/unsafe java/lang/invoke/VarHandles
• Linux x86_32 Zero fastdebug, bootcycle-images

---

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

Issue

• JDK-8319777: Zero: Support 8-byte cmpxchg (Enhancement - P4)

Reviewers

• David Holmes (@dholmes-ora - Reviewer)
• Thomas Stuefe (@tstuefe - Reviewer)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk.git pull/16614/head:pull/16614
$ git checkout pull/16614

Update a local copy of the PR:
$ git checkout pull/16614
$ git pull https://git.openjdk.org/jdk.git pull/16614/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 16614

View PR using the GUI difftool:
$ git pr show -t 16614

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk/pull/16614.diff

Webrev

Link to Webrev Comment

[bridgekeeper]

👋 Welcome back shade! 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]

@shipilev The following label will be automatically applied to this pull request:

• hotspot

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

[mlbridge]

Webrevs

• 01: Full - Incremental (783330fa)
• 00: Full (83c93a3c)

[dholmes-ora]

Looks good - thanks. Sorry for the delay - swamped at the moment.

[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:

8319777: Zero: Support 8-byte cmpxchg

Reviewed-by: dholmes, stuefe

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 30 new commits pushed to the master branch:

• 3452210: 8283140: Remove unused encoding classes/operands from x86_64.ad
• f0b7eb5: 8304020: Speed up test/jdk/java/util/zip/ZipFile/TestTooManyEntries.java and clarify its purpose
• ffa35d8: 8301997: Move method resolution information out of the cpCache
• 891d8cf: 8319986: Invalid/inconsistent description and example for DateFormat
• 536b1ce: 8320130: Problemlist 2 vmTestbase/nsk/jdi/StepRequest/addClassFilter_rt tests with Xcomp
• 0bda467: 8319187: Add three eMudhra emSign roots
• 3c6ffca: 8318219: RISC-V: C2 ExpandBits
• 77a6966: 8320053: GHA: Cross-compile gtest code
• 4f4d00f: 8319966: AIX: expected [[0:i4]] but found [[0:I4]] after JDK-8319882
• 2e34a2e: 8318671: Potential uninitialized uintx value after JDK-8317683
• ... and 20 more: https://git.openjdk.org/jdk/compare/9c98270737cd2019f230e9359bb9298f8df2ca35...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.

[tstuefe]

Good.

[shipilev]

Thanks all, I am integrating and paying extra attention to build/test pipelines for these.

/integrate

[openjdk]

Going to push as commit 6b96bb6.
Since your change was applied there have been 81 commits pushed to the master branch:

• 020c900: 8320052: Zero: Use __atomic built-ins for atomic RMW operations
• 30d8953: 8275889: Search dialog has redundant scrollbars
• cee54de: 8319988: Wrong heading for inherited nested classes
• 32098ce: 8320348: test/jdk/java/io/File/GetAbsolutePath.windowsDriveRelative fails if working directory is not on drive C
• a2c0fa6: 8320372: test/jdk/sun/security/x509/DNSName/LeadingPeriod.java validity check failed
• 3aefd1c: 8320234: Merge doclint.Env.AccessKind with tool.AccessKind
• d6d7bdc: 8319817: Charset constructor should make defensive copy of aliases
• 0712b22: 8320147: Remove DumpSharedSpaces
• 6e86904: 8319973: AArch64: Save and restore FPCR in the call stub
• 04fd17e: 8320410: Reflow markdown in building.md
• ... and 71 more: https://git.openjdk.org/jdk/compare/9c98270737cd2019f230e9359bb9298f8df2ca35...master

Your commit was automatically rebased without conflicts.

[openjdk]

@shipilev Pushed as commit 6b96bb6.

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