8379695: [lworld] Update GCBasher to use value classes

[lmesnik]

The GCbasher si a GC stress test that create a lot of different objects and arrays.

It would be makes sense to update it to create a lot of different value classes and arrays of value types. It helps to ensure that GC works with different type of classes.

Please, note that after this fix GCbasher is going to enable preview always.
Do we want to keep original test while value classes are still preview feature?
I think that it is not needed, however if someone thinks it is good idea, I can add gcbasher-nopreview and keep until we start removing @enablePreview from our tests.

In the long term the problem might be that some structure are flattened, and test start generating less objects. However they are much more diverse now.

UPDATE. There are 3 possible approaches to maintain value/non-value classes

1. keep old version of gcbahser
2. keep value/non-value classes in different directories and have 2 tests with different @compile commands to choose different files
3. add @ValueClass annotation and support javac plugin that change value class attribute during compilation. In this case we need to add 'PREVEW_MODE' when tests are compiles with --enable-preview and this pluign.

The 2) and 3) might work well to maintain value/non-value variants of tests. While it looks overcompilcated for gcbasher. So I prefer to either have 'gcbasher-novalue' or use only variant with --enable-preview.

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Issue

• JDK-8379695: [lworld] Update GCBasher to use value classes (Enhancement - P4)

Reviewers

• Paul Hübner (@Arraying - Committer)

Reviewing

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8379695: [lworld] Update GCBasher to use value classes

Reviewed-by: phubner

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At the time when this comment was updated there had been 118 new commits pushed to the lworld branch:

• 2cbe244: 8337056: [lworld] Document APIs that require Identity objects as parameters
• de4e3f5: 8381608: [lworld] Remove vmTestbase/nsk/jdi/Accessible/modifiers/modifiers001/TestDescription.java from ProblemList-enable-preview.txt
• 1218987: Merge
• ... and 115 more: https://git.openjdk.org/valhalla/compare/8ee2ecbd7ae1d7e7047de6e1030d01aaa346eec7...lworld

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[Arraying]

Thank you for working on this!

Please, note that after this fix GCbasher is going to enable preview always.
Do we want to keep original test while value classes are still preview feature?
I think that it is not needed, however if someone thinks it is good idea, I can add gcbasher-nopreview and keep until we start removing @enablePreview from our tests.

My opinion is that we would lose quite a bit of test coverage w/o preview if we get rid of GCBasher. I think I'd like to see both, at least over a transitionary period.

keep old version of gcbahser

I think this would be the pragmatic choice. However, we should probably introduce a comment in both source files indicating that they are mirrored.

[lmesnik]

I think this would be the pragmatic choice. However, we should probably introduce a comment in both source files indicating that they are mirrored.
Agree, let wait for https://bugs.openjdk.org/browse/JDK-8380084 is implemented and use annotation to mark value classes so gcbasher might works with and without --enable-preview.

[Arraying]

Looks fine. My understanding is that javac will automatically run the required plugin when --enable-preview is provided so nothing changes on the test side of things.

[Arraying]

While it is good to have as many value classes as possible, I am not sure what we gain here. But I guess it could be worth testing nonetheless.

[lmesnik]

/integrate

[openjdk]

Going to push as commit 92c5e58.
Since your change was applied there have been 120 commits pushed to the lworld branch:

• 3372f27: 8381740: [lworld] Disable TestLWorld::test9 until JDK-8302217 is fixed
• 3fe5fe3: 8381700: [lworld] move ProblemList entry for tools/javac/processing/model/element/TestValueClasses.java to ProblemList.txt
• 2cbe244: 8337056: [lworld] Document APIs that require Identity objects as parameters
• ... and 117 more: https://git.openjdk.org/valhalla/compare/8ee2ecbd7ae1d7e7047de6e1030d01aaa346eec7...lworld

Your commit was automatically rebased without conflicts.

[openjdk]

@lmesnik Pushed as commit 92c5e58.

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