RFR: 8324890: C2 SuperWord: refactor out VLoop, make unrolling_analysis static, remove init/reset mechanism [v2]

[Emanuel Peter]

On Thu, 1 Feb 2024 19:03:17 GMT, Vladimir Kozlov <kvn at openjdk.org> wrote:

>> Emanuel Peter has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains 12 additional commits since the last revision:
>> 
>>  - Merge branch 'master' into JDK-8324890
>>  - _vtrace is moved to VLoop
>>  - comment update
>>  - cosmetics
>>  - rename in preconditions
>>  - remove loop_transform_helper
>>  - fix small bug
>>  - preallocate memory
>>  - more refactoring
>>  - moved mark_reductions
>>  - ... and 2 more: https://git.openjdk.org/jdk/compare/f740d7dd...25e3710e
>
> src/hotspot/share/opto/loopnode.cpp line 4866:
> 
>> 4864: 
>> 4865:   // Auto-vectorize main-loop
>> 4866:   if (C->do_superword() && C->has_loops() && !C->major_progress()) {
> 
> Should we rename `do_superword()` too?

@vnkozlov yes, but later, I would say. It simply caries the same values as `UseSuperWord`. I guess eventually we may have different AutoVectorization components, and it may be better to have a unified AutoVectorization option. Is it ok to leave that to the future, and leave it in for now?

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PR Review Comment: https://git.openjdk.org/jdk/pull/17624#discussion_r1475759263