RFR: 8342393: Promote commutative vector IR node sharing [v2]

[Emanuel Peter]

On Wed, 8 Jan 2025 12:47:23 GMT, Emanuel Peter <epeter at openjdk.org> wrote:

>> Assertion check added.
>
> Where did you add it? I don't see it in the constructor or `add_flag`.

I also wonder: if the flag `is_commutative_operation` is available at the `Node` level, and not just `VectorNode`, then should this logic here not be at `Node::hash` rather than `VectorNode::hash`? Otherwise, the flag should probably be called `is_commutative_vector_operation`, right?

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PR Review Comment: https://git.openjdk.org/jdk/pull/22863#discussion_r1907134128