8302976: C2 intrinsification of Float.floatToFloat16 and Float.float16ToFloat yields different result than the interpreter

[vnkozlov]

Backport JDK-8302976 "C2 intrinsification of Float.floatToFloat16 and Float.float16ToFloat yields different result than the interpreter".

Backport did not apply cleanly because of NULL to nullptr changes in JDK 21. And because these intrinsics were implemented for RISC-V port only in JDK 21 and I have to exclude corresponding changes from backport.

The fix was pushed into JDK 21 two weeks ago. No issues were found since then.

---

Progress

• Change must be properly reviewed (1 review required, with at least 1 Reviewer)
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• Commit message must refer to an issue

Issue

• JDK-8302976: C2 intrinsification of Float.floatToFloat16 and Float.float16ToFloat yields different result than the interpreter

Reviewers

• Vladimir Ivanov (@iwanowww - Reviewer)
• Tobias Hartmann (@TobiHartmann - Reviewer)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk20u.git pull/21/head:pull/21
$ git checkout pull/21

Update a local copy of the PR:
$ git checkout pull/21
$ git pull https://git.openjdk.org/jdk20u.git pull/21/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 21

View PR using the GUI difftool:
$ git pr show -t 21

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk20u/pull/21.diff

[bridgekeeper]

👋 Welcome back kvn! 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 backport pull request has now been updated with issue from the original commit.

[mlbridge]

Webrevs

• 00: Full (1741e8b0)

[vnkozlov]

@iwanowww, @jatin-bhateja, @sviswa7 please review this backport. Changes: removed RISC-V changes and resolved merge conflicts without changes to new code (surrounding code uses nullptr in JDK 21 vs NULL in JDK 20u).

[iwanowww]

Looks good.

[openjdk]

@vnkozlov 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:

8302976: C2 intrinsification of Float.floatToFloat16 and Float.float16ToFloat yields different result than the interpreter

Reviewed-by: vlivanov, thartmann

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[TobiHartmann]

Looks good.

[vnkozlov]

Thank you, Vladimir and Tobias.

[vnkozlov]

/integrate

[openjdk]

Going to push as commit 59a3f4f.

[openjdk]

@vnkozlov Pushed as commit 59a3f4f.

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