RFR: 8371674: C2 fails with Missed optimization opportunity in PhaseIterGVN for MoveL2D [v2]

[Benoît Maillard]

On Wed, 19 Nov 2025 10:12:06 GMT, Emanuel Peter <epeter at openjdk.org> wrote:

>> Benoît Maillard has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Rename test and add comment
>
> Looks good to me, thanks for working on this :)
> 
> I've been wondering how we could well test and reproduce all these issues in the past. One idea was to have some sort of special `OpaqueDelayNode` that would fold away in a very specific phase, or maybe at a random time. For example, during post-loop-opts, and then it would exactly trigger your condition here. That would allow us to even have IR rules, and make sure the fix really keeps on working. I had once filed this: [JDK-8357805](https://bugs.openjdk.org/browse/JDK-8357805).

@eme64 Thanks for the review!

I think that's a great idea, I have also been thinking about this exact problem but I didn't think of intrinsified identity methods. I would be happy to discuss that at some point, I may have some ideas as well.

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PR Comment: https://git.openjdk.org/jdk/pull/28290#issuecomment-3552464210