RFR: 8333684: C2 SuperWord: multiple smaller refactorings in preparation for JDK-8332163

[Emanuel Peter]

On Wed, 12 Jun 2024 11:07:27 GMT, Christian Hagedorn <chagedorn at openjdk.org> wrote:

> You do not seem to be using the actual unique input at the call sites and only care about whether there is a unique input or not (all checks are against nullptr).

I do not need it now, but will after a further refactoring. So I'd like to have it already available to keep the noise in the next refactoring down.

> I'm not sure if "unique" could be misleading as in "only once" in the entire pack.

Ok, I could do that. That would be closer to the old name `same_inputs`.

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PR Review Comment: https://git.openjdk.org/jdk/pull/19573#discussion_r1636348212