RFR: 8355585: Aarch64: Add aarch64 backend for Float16 vector operations [v4]

[Emanuel Peter]

On Wed, 21 May 2025 12:13:53 GMT, Bhavana Kilambi <bkilambi at openjdk.org> wrote:

>>> Looks good. I'm assuming you've tested both SVE and Neon.
>> 
>> Yes, this was tested on both SVE and Neon (N1/V1/V2 architectures).
>
>> @Bhavana-Kilambi I'm getting timeouts with your new test: `compiler/vectorization/TestFloat16VectorOperations.java`
>> 
>> At least on `linux-aarch64-debug` and `windows-x64-debug`, but not all tests have completed yet, so more could be failing.
>> 
>> Not sure if it is relevant, but both had extra flag `-XX:-UseTLAB`, we add this flag in our additional stress testing.
> 
> Thanks for letting me know. This test by default takes a very long time to finish. As i added more flags (to test various vector sizes) to be tested, it probably ran way too long than anticipated and resulted in the timeout error. I will update with a patch to remove testing these extra flags for now. I did try to increase the default timeout value but the test continued to run for more than 20 min after which I had to terminate. I feel the best for now is to remove the additional tests for various vector sizes that I have added. I will update the patch soon.

@Bhavana-Kilambi Ok, yes, 20min is a bit excessive 😆 

Generally, we should periodically run all vector tests with various `MaxVectorSize` settings. But doing that all the time is often too time consuming. For some specific tests, it can make sense though to iterate over multiple sizes.

I wonder if you could also reduce the runtime of the test in other ways? Maybe reduce the warmup? It seems a bit excessive to do `10000` warmup iterations, which each execute a loop with many iterations themselves.

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PR Comment: https://git.openjdk.org/jdk/pull/25096#issuecomment-2898027287