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

[Marc Chevalier]

On Tue, 9 Sep 2025 08:29:51 GMT, Emanuel Peter <epeter at openjdk.org> wrote:

>> I thought about that and I think the current situation is ok. The pattern is not something highly mutable, it's mostly some hardcoded thing. I don't think it's hard to figure out what you're expecting. I'm very reluctant to add some ugliness to the patterns who must stay readable, to be easy to verify by a human. It could be solved with more templates tho.
>
> Once we have more complex patterns, will it really be that easy to see what was expected?
> All you will see is what we actually got. You are already all about good reporting, so I just noticed a hole here.
> You know the code better, so I'll leave it up to you in the end ;)

That is not quite true! We will also print the path from the center, so we know how we arrived at the point that has an unexpected type. We can both use the pattern and follow it, or our general knowledge of the IR to see that something looks wrong in the displayed part.

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PR Review Comment: https://git.openjdk.org/jdk/pull/26362#discussion_r2333006921