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

[Emanuel Peter]

On Tue, 11 Nov 2025 15:32:04 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/micro/org/openjdk/bench/vm/compiler/VectorThroughputForIterationCount.java line 225:
> 
>> 223:         for (int i = startIndex; i < startIndex + length; i++) {
>> 224:             c[i] = a[i] + b[i];
>> 225:         }
> 
> You could forceinline them, just for good measure. Up to you.

Wait, you are doing some kind of special warmup above. Why? Do you maybe NOT want the methods to inline? Any other reason for the warmup?

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PR Review Comment: https://git.openjdk.org/jdk/pull/22629#discussion_r2514682741