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

Galder Zamarreño galder at openjdk.org
Thu Dec 18 11:37:53 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.

-------------

Commit messages:
 - 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=00
  Issue: https://bugs.openjdk.org/browse/JDK-8373134
  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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