RFR: 8373134: C2: Min/Max users of Min/Max uses should be enqueued for GVN [v2]
Galder Zamarreño
galder at openjdk.org
Thu Dec 18 15:05:08 UTC 2025
> 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 with a new target base due to a merge or a rebase. The pull request now contains nine commits:
- Merge branch 'master' into topic.uses-min-max
- Test Float16
- Only apply to uses that match original IR node
- Merge branch 'master' into topic.uses-min-max
- Use is_MinMax() instead of spelling out individual Min/Max opcodes
- Refactor MaxNode to MinMaxNode and add is_MinMax() query
- Add max(a, max(b, c)) patterns to add users of use
- Add templated test
- Remove exclude or Min/Max in verify identity
-------------
Changes: https://git.openjdk.org/jdk/pull/28895/files
Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=28895&range=01
Stats: 268 lines in 9 files changed: 196 ins; 21 del; 51 mod
Patch: https://git.openjdk.org/jdk/pull/28895.diff
Fetch: git fetch https://git.openjdk.org/jdk.git pull/28895/head:pull/28895
PR: https://git.openjdk.org/jdk/pull/28895
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