8370481: C2 SuperWord: Long/Integer.compareUnsigned return wrong value in SLP

[rm-gh-8]

Backporting JDK-8370481: C2 SuperWord: Long/Integer.compareUnsigned return wrong value in SLP.

This PR fixes a C2 auto-vectorization correctness bug.

Please note that this PR introduces a regression for unsigned I/L EQ/NE in SLP that will be fixed by JDK-8370794 (dependent PR).

For parity with Oracle JDK.

Ran related tests on linux-x64, linux-aarch64, macos-aarch64 and windows-x64:

make test TEST=test/hotspot/jtreg/compiler/c2/irTests/TestVectorConditionalMove.java
make test TEST=hotspot_compiler

Results:

windows-x64-specific-test.log
windows-x64-specific-2-test.log
macos-aarch64-specific-test.log
macos-aarch64-specific-2-test.log
linux-x64-specific-test.log
linux-x64-specific-2-test.log
linux-aarch64-specific-test.log
linux-aarch64-specific-2-test.log

---

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---

Progress

• Change must not contain extraneous whitespace
• Commit message must refer to an issue
• JDK-8370481 needs maintainer approval

Issue

• JDK-8370481: C2 SuperWord: Long/Integer.compareUnsigned return wrong value in SLP (Bug - P3 - Requested)

Reviewing

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Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk25u-dev.git pull/728/head:pull/728
$ git checkout pull/728

Update a local copy of the PR:
$ git checkout pull/728
$ git pull https://git.openjdk.org/jdk25u-dev.git pull/728/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 728

View PR using the GUI difftool:
$ git pr show -t 728

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk25u-dev/pull/728.diff

Using Webrev

Link to Webrev Comment

[bridgekeeper]

👋 Welcome back rmesde! A progress list of the required criteria for merging this PR into pr/725 will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

[openjdk]

❗ This change is not yet ready to be integrated.
See the Progress checklist in the description for automated requirements.

[openjdk]

This backport pull request has now been updated with issue from the original commit.

[mlbridge]

Webrevs

• 02: Full - Incremental (7e0b016e)
• 01: Full - Incremental (7351fb66)
• 00: Full (7351fb66)

[rm-gh-8]

/approval request for backport of JDK-8370481: C2 SuperWord: Long/Integer.compareUnsigned return wrong value in SLP.

This PR fixes a C2 auto-vectorization correctness bug.

Please note that this PR introduces a regression for unsigned I/L EQ/NE in SLP that will be fixed by JDK-8370794 (dependent PR).

For parity with Oracle JDK.

Low-moderate risk — a narrowly-scoped fix to C2, but the new ShouldNotReachHere() would crash a JVM if an unexpected comparison reaches it.

[openjdk]

@rm-gh-8
8370481: The approval request has been created successfully.

[openjdk-notifier]

The parent pull request that this pull request depends on has now been integrated and the target branch of this pull request has been updated. This means that changes from the dependent pull request can start to show up as belonging to this pull request, which may be confusing for reviewers. To remedy this situation, simply merge the latest changes from the new target branch into this pull request by running commands similar to these in the local repository for your personal fork:

git checkout JDK-8370481-V25
git fetch https://git.openjdk.org/jdk25u-dev.git master
git merge FETCH_HEAD
# if there are conflicts, follow the instructions given by git merge
git commit -m "Merge master"
git push