RFR: 8371536: C2: VerifyIterativeGVN should assert on first detected failure [v9]

[Emanuel Peter]

On Wed, 28 Jan 2026 17:08:37 GMT, Benoît Maillard <bmaillard at openjdk.org> wrote:

>> You could even make that a debug only field of `PhaseIterGVN` and override it for `PhaseCCP`.
>
> Following a discussion with @mhaessig, I decided to replace the `_iterGVN` boolean field by an enum field, and refactor `is_IterGVN` using this new field. 
> 
> ```c++
> enum class PhaseValuesType {
>     gvn,
>     iter_gvn,
>     ccp
>   };

Yet another option: You just pass the `Phase`, and check if it is PhaseIterGVN etc.

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PR Review Comment: https://git.openjdk.org/jdk/pull/28295#discussion_r2740385322