8279676: Dubious YMM register clearing in x86_64 arraycopy stubs

[shipilev]

See discussion in the bug.

Additional testing, TR3970X (Zen 2, AVX2):

• Linux x86_64 fastdebug hotspot_compiler_arraycopy
• Linux x86_64 fastdebug tier1
• Linux x86_64 fastdebug tier2
• Linux x86_64 fastdebug tier3

Additional testing, i5-11500 (Rocket Lake, AVX-512):

• Linux x86_64 fastdebug hotspot_compiler_arraycopy
• Linux x86_64 fastdebug tier1
• Linux x86_64 fastdebug tier2
• Linux x86_64 fastdebug tier3

Targeted arraycopy microbenchmarks find a barely noticeable improvement on TR 3970X and i5-11500 with UseAVX=2.

---

Progress

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

Issue

• JDK-8279676: Dubious YMM register clearing in x86_64 arraycopy stubs

Reviewers

• Vladimir Kozlov (@vnkozlov - Reviewer)
• Vladimir Ivanov (@iwanowww - Reviewer)
• Nils Eliasson (@neliasso - Reviewer)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.java.net/jdk pull/7016/head:pull/7016
$ git checkout pull/7016

Update a local copy of the PR:
$ git checkout pull/7016
$ git pull https://git.openjdk.java.net/jdk pull/7016/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 7016

View PR using the GUI difftool:
$ git pr show -t 7016

Using diff file

Download this PR as a diff file:
https://git.openjdk.java.net/jdk/pull/7016.diff

[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-compiler

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

• 00: Full (dc1a6633)

[vnkozlov]

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:

8279676: Dubious YMM register clearing in x86_64 arraycopy stubs

Reviewed-by: kvn, vlivanov, neliasso

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:

• 6714184: 8279700: Parallel: Simplify ScavengeRootsTask constructor API
• cfee451: 8273914: Indy string concat changes order of operations
• c3d0a94: 8279833: Loop optimization issue in String.encodeUTF8_UTF16
• 9e02447: 8279834: Alpine Linux fails to build when --with-source-date enabled
• 08e14c6: 8278207: G1: Tighten verification in G1ResetSkipCompactingClosure
• c08b2ac: 8225093: Special property jdk.boot.class.path.append should not default to empty string
• 4c52eb3: 8279669: test/jdk/com/sun/jdi/TestScaffold.java uses wrong condition
• d46410c: 8279785: JFR: 'jfr configure' should show default values
• 2bbeae3: 8279668: x86: AVX2 versions of vpxor should be asserted
• 3121898: 8279703: G1: Remove unused force_not_compacted local in G1CalculatePointersClosure::do_heap_region
• ... and 20 more: https://git.openjdk.java.net/jdk/compare/dee447f8ae788c6c1f6cd1e1fcb93faceab37b6c...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.

[iwanowww]

Looks good.

[neliasso]

Looks good!

[shipilev]

Thanks for reviews!

/integrate

[openjdk]

Going to push as commit 525b20f.
Since your change was applied there have been 39 commits pushed to the master branch:

• 4f0b650: 8278581: Improve reference processing statistics log output
• bd339aa: 8277627: Fix copyright years in some jvmci files
• 319d230: 8277463: JFileChooser with Metal L&F doesn't show non-canonical UNC path in - Look in
• 13bfb49: 6496103: isFileHidingEnabled return false by default
• f16f6a9: 8279821: JFR: Log warnings properly when loading a misconfigured .jfc file
• 1c688f4: 8279900: compiler/vectorization/TestPopCountVectorLong.java fails due to vpopcntdq is not supported
• 3aaa098: 8276694: Pattern trailing unescaped backslash causes internal error
• 36f41cb: 8279884: Use better file for cygwin source permission check
• c4518e2: 8278868: Add x86 vectorization support for Long.bitCount()
• 6714184: 8279700: Parallel: Simplify ScavengeRootsTask constructor API
• ... and 29 more: https://git.openjdk.java.net/jdk/compare/dee447f8ae788c6c1f6cd1e1fcb93faceab37b6c...master

Your commit was automatically rebased without conflicts.

[openjdk]

@shipilev Pushed as commit 525b20f.

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