RFR: 8375038: C2: Enforce that Ideal() returns the root of the subgraph if any change was made by checking the node hash [v2]

[Benoît Maillard]

On Fri, 30 Jan 2026 09:19:32 GMT, Marc Chevalier <mchevalier at openjdk.org> wrote:

>> Benoît Maillard has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Update src/hotspot/share/opto/node.cpp
>>   
>>   Co-authored-by: Roberto Castañeda Lozano <robcasloz at users.noreply.github.com>
>
> Is it going to be added in testing? Maybe we can at least add it to
> https://github.com/openjdk/jdk/blob/42370e22c5bc4ebd40fd500a2e6e9e07f0b8bcd8/test/hotspot/jtreg/compiler/c2/TestVerifyIterativeGVN.java#L24-L37
> 
> There starts to be a lot of sub-flags in this flag. Would is be meaningful to merge the new one with
> https://github.com/openjdk/jdk/blob/42370e22c5bc4ebd40fd500a2e6e9e07f0b8bcd8/src/hotspot/share/opto/c2_globals.hpp#L702
> Since it's also about verifying whether something changed? That would mean fixing everything before merging this, alas. And if I'm fine with merged flags that enable more things than maybe useful, I can also spam the `1`s for `VerifyIterativeGVN`.

Thank you for your reviews @marc-chevalier @merykitty!

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PR Comment: https://git.openjdk.org/jdk/pull/29421#issuecomment-3882994837