RFR: 8307084: C2: Vectorized drain loop is not executed for some small trip counts [v3]

[Fei Gao]

On Tue, 11 Nov 2025 15:27:38 GMT, Emanuel Peter <epeter at openjdk.org> wrote:

>> Fei Gao has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 11 commits:
>> 
>>  - Fixed new test failures after rebasing and refined parts of the code to address review comments
>>  - Merge branch 'master' into optimize-atomic-post
>>  - Merge branch 'master' into optimize-atomic-post
>>  - Clean up comments for consistency and add spacing for readability
>>  - Fix some corner case failures and refined part of code
>>  - Merge branch 'master' into optimize-atomic-post
>>  - Refine ascii art, rename some variables and resolve conflicts
>>  - Merge branch 'master' into optimize-atomic-post
>>  - Add necessary ASCII art, refactor insert_post_loop() and rename
>>    "atomic post loop" with "vectorized drain loop.
>>  - Merge branch 'master' into optimize-atomic-post
>>  - ... and 1 more: https://git.openjdk.org/jdk/compare/eab5644a...e21a830f
>
> test/hotspot/jtreg/compiler/loopopts/superword/TestVectorizedDrainLoop.java line 85:
> 
>> 83:         }
>> 84:         return sum;
>> 85:     }
> 
> Since recently, this now also auto vectorizes. Maybe this method should not be compiled, if it is part of verification?

That makes sense. Thanks!

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PR Review Comment: https://git.openjdk.org/jdk/pull/22629#discussion_r2517948392