RFR: 8322735: C2: minor improvements of bubble sort used in SuperWord::packset_sort

[Denghui Dong]

On Thu, 4 Jan 2024 12:36:01 GMT, Emanuel Peter <epeter at openjdk.org> wrote:

> And a more fundamental question: Why do we need this improvement? Do you see any timing bottleneck and improvement? And what is faster: bubbling up or down?
> 
> And do you know why we sort at all in `extend_packlist` and why we do it again and again?

Sorry, I don't know the theory or implementation of `superword`. (I hope to grasp it someday...)

I just found it when browsing the code. This change is trivial; if you think it's unnecessary, I'm fine with closing it.

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PR Comment: https://git.openjdk.org/jdk/pull/17190#issuecomment-1877328019