RFR: 8323577: C2 SuperWord: remove AlignVector restrictions on IR tests added in JDK-8305055

[Christian Hagedorn]

On Thu, 11 Jan 2024 10:16:14 GMT, Emanuel Peter <epeter at openjdk.org> wrote:

> These IR rules were restricted in [JDK-8305055](https://bugs.openjdk.org/browse/JDK-8305055), [PR for comparison](https://git.openjdk.org/jdk/pull/13236).
> 
> This had to be done because those cases were no longer vectorized with `AlignVector` after my bugfix [JDK-8298935](https://bugs.openjdk.org/browse/JDK-8298935), they were "collateral damage". Before this bugfix, we would vectorize, even though the alignment constraints had rejected some memops, but then they were re-intriduced during pair extension. This re-introduction led to this bug for other reasons. I proposed to restore vectorization (i.e. fix the "collateral damage") by improving alignment-constraints ([JDK-8303827](https://bugs.openjdk.org/browse/JDK-8303827)).
> 
> Since I had to already completely rework the alignment constraints because of a bug, I relaxed the constraints:
> [JDK-8310190](https://bugs.openjdk.org/browse/JDK-8310190)
> 
> Now I can remove the restrictions on those rules.

Looks good!

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Marked as reviewed by chagedorn (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/17369#pullrequestreview-1815556911