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

---

• I confirm that I make this contribution in accordance with the OpenJDK Interim AI Policy.

---

Progress

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

Integration blocker

 ⚠️ Dependency #725 must be integrated first

Issue

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

Reviewing

Using git

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

• 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.