RFR: 8356760: VectorAPI: Optimize VectorMask.fromLong for all-true/all-false cases [v3]

[Jatin Bhateja]

On Mon, 7 Jul 2025 03:42:27 GMT, erifan <duke at openjdk.org> wrote:

> > What if during iterative GVN a constant -1 seeps through IR graph and gets connected to the input of VectorLongToMaskNode, you won't be able to create maskAll true in that case?
> 
> Yes, this PR doesn't support this case. Maybe we should do this optimization in `ideal`. If `VectorLongToMask` is not supported, then try to convert it to `maskAll` or `Replicate` in intrinsic.
> 

I would suggest extending VectorLongToMaskNode::Ideal for completeness of the solution.

-------------

PR Review Comment: https://git.openjdk.org/jdk/pull/25793#discussion_r2189445358