RFR: 8350864: C2: verify structural invariants of the Ideal graph [v5]

[Marc Chevalier]

On Tue, 9 Sep 2025 08:15:26 GMT, Emanuel Peter <epeter at openjdk.org> wrote:

>> I don't understand.
>
> I would still consider adding `OuterStripMinedLoop` here, to capture that it has a similar structure. Even if you also verify below specific things for `OuterStripMinedLoop`. Just to check that all these loop structures have the same kind of backedge shape.
> And then make a switch out of it, with a default case that fails. In case we add yet another `Loop` shape, we would then catch that and add the logic for it.
> 
> But actually: do not all `Loop` shapes have this backedge pattern? Or are there some that have a `IfFalse` on the backedge? Because then you could also add `LoopNode` with `LoopEndNode`.

Same as before: we extend the checks later.

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PR Review Comment: https://git.openjdk.org/jdk/pull/26362#discussion_r2333895804