RFR: 8332163: C2 SuperWord: refactor PacksetGraph and SuperWord::output into VTransformGraph [v10]

[Emanuel Peter]

On Tue, 2 Jul 2024 11:24:16 GMT, Christian Hagedorn <chagedorn at openjdk.org> wrote:

>> Emanuel Peter has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   tabs and includes
>
> Nice refactoring. It was a little bit difficult to review. But I think it overall looks good. 
> 
> Here are some comments about a first pass. Feel free to also do some of the suggestions separately if you agree with them since the PR is already quite big.

@chhagedorn thanks again for all the review comments! I now addressed everything, except for the complaint that I repeatedly used `_vtransform.arena()`. But I don't know any better alternative. Your suggestion of using a `_arena` field in the `SuperWordVTransformBuilder` is not a great idea, because it suggests that this `_arena` has the life-time of the builder. But it should be the life-time of the vtransform, which outlives the builder. So it would have to be a `_vtransform_arena` field, at which point I might as well use `_vtransform.arena()` as it is now. Let me know if you have any better idea.

And please re-review ;)

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PR Comment: https://git.openjdk.org/jdk/pull/19719#issuecomment-2206217110