8345146: [PPC64] Make intrinsic conversions between bit representations of half precision values and floats

[TheRealMDoerr]

Almost clean backport of JDK-8345146. Two hunks had to be integrated manually due to unrelated differences in the context. The test updates had to be integrated manually because the RISCV part is not backported. TestFloat16VectorConvChain.java is not in 21u (introduced by openjdk/jdk@55fd1ed).

Original PR with performance numbers: openjdk/jdk#22433

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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
• JDK-8345146 needs maintainer approval

Issue

• JDK-8345146: [PPC64] Make intrinsic conversions between bit representations of half precision values and floats (Enhancement - P3 - Requested)

Reviewers

• Richard Reingruber (@reinrich - Reviewer)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk21u-dev.git pull/1295/head:pull/1295
$ git checkout pull/1295

Update a local copy of the PR:
$ git checkout pull/1295
$ git pull https://git.openjdk.org/jdk21u-dev.git pull/1295/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 1295

View PR using the GUI difftool:
$ git pr show -t 1295

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk21u-dev/pull/1295.diff

Using Webrev

Link to Webrev Comment

[bridgekeeper]

👋 Welcome back mdoerr! 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 (baf816a6)

[reinrich]

Looks good.
Cheers, Richard.

[openjdk]

⚠️ @TheRealMDoerr 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.

[TheRealMDoerr]

Thanks for the review!

[TheRealMDoerr]

/approval request JDK-8289551 is a JDK20 feature. It's very slow without the intrinsics. That impacts some of the jtreg tests, too. Therefore, I'm requesting JDK21u backport. Performance numbers are shown in the original PR. x86_64 and aarch64 have the intrinsics backported even to JDK20 (JDK-8302976). The backport is almost clean, has been reviewed and tested for several weeks.

[openjdk]

@TheRealMDoerr
8345146: The approval request has been created successfully.