8299038: Add AArch64 backend support for auto-vectorized FP16 conversions

[Bhavana-Kilambi]

This patch adds aarch64 backend support for auto-vectorized FP16 conversions namely, half precision to single precision and vice versa. Both Neon and SVE versions are included. The performance of this patch was tested on aarch64 machines with vector size of 128-bit, 256-bit and 512-bit.

Following are the performance improvements in throughput observed with the vectorized version versus the scalar code (which is the current implementation) for the JMH micro benchmark -
test/micro/org/openjdk/bench/java/math/Fp16ConversionBenchmark.java

Benchmark                               128-bit  256-bit  512-bit
Fp16ConversionBenchmark.float16ToFloat  6.02     8.72     24.71
Fp16ConversionBenchmark.floatToFloat16  2.00     3.29     10.84

The numbers shown are the ratios between throughput of vectorized version and that of the scalar version.

---

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-8299038: Add AArch64 backend support for auto-vectorized FP16 conversions

Reviewers

• Xiaohong Gong (@XiaohongGong - Committer)
• Nick Gasson (@nick-arm - Reviewer)

Reviewing

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Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk pull/11825/head:pull/11825
$ git checkout pull/11825

Update a local copy of the PR:
$ git checkout pull/11825
$ git pull https://git.openjdk.org/jdk pull/11825/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 11825

View PR using the GUI difftool:
$ git pr show -t 11825

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk/pull/11825.diff

[bridgekeeper]

👋 Welcome back bkilambi! 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]

@Bhavana-Kilambi The following label will be automatically applied to this pull request:

• hotspot-compiler

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[mlbridge]

Webrevs

• 01: Full - Incremental (49c0b7b7)
• 00: Full (4ba1cf5d)

[XiaohongGong]

Looks good to me. Thanks!

[openjdk]

@Bhavana-Kilambi 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:

8299038: Add AArch64 backend support for auto-vectorized FP16 conversions

Reviewed-by: xgong, ngasson

You can use pull request commands such as /summary, /contributor and /issue to adjust it as needed.

At the time when this comment was updated there had been 178 new commits pushed to the master branch:

• 6fea233: 8299960: Speed up test/hotspot/jtreg/compiler/c2/irTests/TestVectorizeURShiftSubword.java
• 7c1ebcc: 8299962: Speed up compiler/intrinsics/unsafe/DirectByteBufferTest.java and HeapByteBufferTest.java
• abfd7e8: 8300113: C2: Single-bit fields with signed type in TypePtr after JDK-8297933
• 83f2c9a: 8293410: Remove GenerateRangeChecks flag
• 50e7df9: 8300024: Replace use of JNI_COMMIT mode with mode 0
• fe7fca0: 8300032: DwarfParser resource leak
• 12edd6f: 8300052: PdhDll::PdhCollectQueryData and PdhLookupPerfNameByIndex will never be NULL
• 7bcd5f4: 8297914: Remove java_lang_Class::process_archived_mirror()
• 4be94e4: Merge
• 87865e0: 8299502: Usage of constructors of primitive wrapper classes should be avoided in javax.xml API docs
• ... and 168 more: https://git.openjdk.org/jdk/compare/a9ce7726a722c9deba659dff3f87b7e72d6c4997...master

As there are no conflicts, your changes will automatically be rebased on top of these commits when integrating. If you prefer to avoid this automatic rebasing, please check the documentation for the /integrate command for further details.

As you do not have Committer status in this project an existing Committer must agree to sponsor your change. Possible candidates are the reviewers of this PR (@XiaohongGong, @nick-arm) but any other Committer may sponsor as well.

➡️ To flag this PR as ready for integration with the above commit message, type /integrate in a new comment. (Afterwards, your sponsor types /sponsor in a new comment to perform the integration).

[Bhavana-Kilambi]

/integrate

[openjdk]

@Bhavana-Kilambi
Your change (at version 49c0b7b) is now ready to be sponsored by a Committer.

[nick-arm]

/sponsor

[openjdk]

Going to push as commit 98d75f1.
Since your change was applied there have been 179 commits pushed to the master branch:

• cac72a6: 8300053: Shenandoah: Handle more GCCauses in ShenandoahControlThread::request_gc
• 6fea233: 8299960: Speed up test/hotspot/jtreg/compiler/c2/irTests/TestVectorizeURShiftSubword.java
• 7c1ebcc: 8299962: Speed up compiler/intrinsics/unsafe/DirectByteBufferTest.java and HeapByteBufferTest.java
• abfd7e8: 8300113: C2: Single-bit fields with signed type in TypePtr after JDK-8297933
• 83f2c9a: 8293410: Remove GenerateRangeChecks flag
• 50e7df9: 8300024: Replace use of JNI_COMMIT mode with mode 0
• fe7fca0: 8300032: DwarfParser resource leak
• 12edd6f: 8300052: PdhDll::PdhCollectQueryData and PdhLookupPerfNameByIndex will never be NULL
• 7bcd5f4: 8297914: Remove java_lang_Class::process_archived_mirror()
• 4be94e4: Merge
• ... and 169 more: https://git.openjdk.org/jdk/compare/a9ce7726a722c9deba659dff3f87b7e72d6c4997...master

Your commit was automatically rebased without conflicts.

[openjdk]

@nick-arm @Bhavana-Kilambi Pushed as commit 98d75f1.

💡 You may see a message that your pull request was closed with unmerged commits. This can be safely ignored.