8378250: C2 VectorAPI : wrong result with MUL reduction at various AVX levels

[missa-prime]

Hi all,

This pull request contains a backport of commit ee0d6cd9 from the openjdk/jdk repository.

The commit being backported was authored by Jatin Bhateja on 31 Mar 2026 and was reviewed by Emanuel Peter.

Thanks!

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

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Progress

• Change must be properly reviewed (1 review required, with at least 1 Reviewer)
• JDK-8378250 needs maintainer approval
• Change must not contain extraneous whitespace
• Commit message must refer to an issue

Issue

• JDK-8378250: C2 VectorAPI : wrong result with MUL reduction at various AVX levels (Bug - P3 - Requested)

Reviewers

• Aleksey Shipilev (@shipilev - Reviewer)
• Paul Hohensee (@phohensee - Reviewer)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk26u.git pull/213/head:pull/213
$ git checkout pull/213

Update a local copy of the PR:
$ git checkout pull/213
$ git pull https://git.openjdk.org/jdk26u.git pull/213/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 213

View PR using the GUI difftool:
$ git pr show -t 213

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk26u/pull/213.diff

Using Webrev

Link to Webrev Comment

[bridgekeeper]

👋 Welcome back missa! 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]

❗ 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 (0dc5d4a1)

[missa-prime]

It looks like the clean tag wasn't applied to this backport PR because the trunk PR operated on different filenames (e.g., ByteVector128Tests.java instead of Byte128VectorTests.java). The PR that renamed those files wasn't backported. The actual code changes in this backport PR are still the same though.

[missa-prime]

@shipilev @phohensee Review?

[shipilev]

All right, thanks.

[openjdk]

⚠️ @missa-prime This change is now ready for you to apply for maintainer approval. This can be done directly in each associated issue or by using the /approval command.

[bridgekeeper]

@missa-prime This pull request has been inactive for more than 4 weeks and will be automatically closed if another 4 weeks passes without any activity. To avoid this, simply issue a /touch or /keepalive command to the pull request. Feel free to ask for assistance if you need help with progressing this pull request towards integration!

[missa-prime]

/touch

[openjdk]

@missa-prime The pull request is being re-evaluated and the inactivity timeout has been reset.