RFR: 8310190: C2 SuperWord: AlignVector is broken, generates misaligned packs [v22]

[Emanuel Peter]

On Wed, 6 Dec 2023 12:36:30 GMT, Christian Hagedorn <chagedorn at openjdk.org> wrote:

>> Emanuel Peter has updated the pull request incrementally with two additional commits since the last revision:
>> 
>>  - add newline suggested by Faye
>>  - improve the alignment proof, make it more explicit
>
> Impressive work! I'm still working my way through the proofs but here are some first comments.

@chhagedorn @fg1417 thanks for the first passes of reviews!

I think I want to follow Christian's idea, and refactor `SuperWord::pack_alignment_solution` into a separate class.
I will make it a bit more general if I can, so that future vectorizers can use it as well.
I'll call it `AlignmentSolver`, which returns a `AlignmentSolution`.
Wrapping it like this allows me to split the code more into sub-functions, without having to pass massive amounts of parameters.
Hopefully that will make the code more readable.

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PR Comment: https://git.openjdk.org/jdk/pull/14785#issuecomment-1843329419