RFR: 8307084: C2: Vectorized drain loop is not executed for some small trip counts

[Emanuel Peter]

On Wed, 3 Sep 2025 17:08:08 GMT, Fei Gao <fgao at openjdk.org> wrote:

>> I'm a little sick and don't feel very focused, so I'll have to look at the PR next week.
>> 
>> BTW: I just integrated https://github.com/openjdk/jdk/pull/24278 which may have silent merge conflicts, so it would be good if you merged and tested again. Once you do that I could also run some internal testing, if you like :)
>
>> BTW: I just integrated https://github.com/openjdk/jdk/pull/24278 which may have silent merge conflicts, so it would be good if you merged and tested again.
> 
> Hi @eme64 , I’ve rebased the patch onto the latest JDK, and all tier1 to tier3 tests have passed on my local AArch64 and x86 machines.
> 
>> It would be good if you re-ran the benchmarks. It seems the last ones you did in December of 2024.
> We should see that we have various benchmarks, both for array and MemorySegment.
> You could look at the array benchmarks from here: https://github.com/openjdk/jdk/pull/22070
> 
> I also re-verified the benchmark from [PR #22070](https://github.com/openjdk/jdk/pull/22070) on 128-bit, 256-bit, and 512-bit vector machines. The results show no significant regressions and performance changes are consistent with the previous round described in [perf results]( https://bugs.openjdk.org/browse/JDK-8307084?focusedId=14729524&page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel#comment-14729524). 
> 
>> Once you do that I could also run some internal testing, if you like :)
> 
> I’d really appreciate it if you could run some internal testing at a time you think is suitable.
> Thanks :)

@fg1417 Are you still working on this?

-------------

PR Comment: https://git.openjdk.org/jdk/pull/22629#issuecomment-3415539539