RFR: 8373134: C2: Min/Max users of Min/Max uses should be enqueued for GVN [v8]

[Emanuel Peter]

On Fri, 9 Jan 2026 16:14:17 GMT, Galder Zamarreño <galder at openjdk.org> wrote:

>> Min/Max users of Min/Max uses need to be enqueued respectively to the GVN worklist to see if further optimizations can be applied. Without this, there are cases where additional potential ideal/identity optimizations are not applied. I need this fix to test min/max reassociation implementation with IR tests reliably.
>> 
>> Aside from the fix itself, I've refactored `MaxNode` to `MinMaxNode` and added a `is_MinMax` node query to simplify the fix.
>> 
>> I have also removed the Min/Max exceptions in `PhaseIterGVN::verify_Identity_for` since this fix fixes `compiler/codegen/TestBooleanVect.java` with `-XX:VerifyIterativeGVN=1110`.
>> 
>> To test this I've created a template framework test that validates the fix. I have tested with all Min/Max combinations including Float16, which I've verified with Intel SDE. Float16 does not use `Argument.NUMBER_42` because there's no support for it yet, see [JDK-8373977](https://bugs.openjdk.org/browse/JDK-8373977).
>> 
>> During development I noticed that the test only failed when the test had `b, a` parameters in that order, so I added tests for both cases as `a, b` and `b, a` so that all possible orders are covered and they don't slip in the future.
>> 
>> I've run tier1-3 tests on linux/x64 successfully.
>
> Galder Zamarreño has updated the pull request incrementally with two additional commits since the last revision:
> 
>  - Update test/hotspot/jtreg/compiler/igvn/TestMinMaxIdentity.java
>    
>    Co-authored-by: Emanuel Peter <emanuel.peter at oracle.com>
>  - Fix style

Looks good to me now, thanks for the updates :)

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Marked as reviewed by epeter (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/28895#pullrequestreview-3649370155