8384107: [lworld] Update runtime/contended tests to run the same testing for value classes

[shivshah-oracle]

Added OopMapsValue and OopMapsSameGroupValue, mirrors OopMaps tests using Integer instances to test contended oop maps with value class objects.

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• JDK-8384107: [lworld] Update runtime/contended tests to run the same testing for value classes (Enhancement - P4)

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• Frederic Parain (@fparain - Committer)

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8384107: [lworld] Update runtime/contended tests to run the same testing for value classes

Reviewed-by: fparain

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At the time when this comment was updated there had been 213 new commits pushed to the lworld branch:

• 4824ac0: 8383164: [lworld] javadoc updates for value class serialization
• cc40808: 8384105: [lworld] serviceability/jvmti/valhalla/SampledObjectAllocValue/SampledObjectAllocValue.java fails after JDK-8382702
• 6b9eb7d: 8384283: [lworld] Post-parse call devirtualization with unloaded return type fails
• ... and 210 more: https://git.openjdk.org/valhalla/compare/5814c9d438c8e71a9e129c689ef58765a7f1d5a1...lworld

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• 01: Full - Incremental (32a4863f)
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[fparain]

As they are currently written, these tests don't exercise interactions between contended or oopmap code and value types. The classes with @Contended annotations are using j.l.Object typed fields, which the VM handles as regular reference fields, not values, for both layout decisions and oopmap generation.

To test interactions between @Contended and value fields, I'd recommend declaring a small value types, less than 56 bits, so it can be flattened (the declared value class Point with two int fields is too big to be flattened), and then declare contended fields using the exact type of the field, not a super type.

To test contended/value types/oopmap interactions, I'd recommend to declare a value type containing a reference type and a small primitive type (for instance value record Opt(Object o, boolean b) { } ), and then declare contended fields of this exact type. This kind of value type would be flattened in VMs using compressed oops, and not flattened in VMs using full size oops, creating two distinct patterns of field layouts including oops and contended padding.

[shivshah-oracle]

As they are currently written, these tests don't exercise interactions between contended or oopmap code and value types. The classes with @Contended annotations are using j.l.Object typed fields, which the VM handles as regular reference fields, not values, for both layout decisions and oopmap generation.

To test interactions between @Contended and value fields, I'd recommend declaring a small value types, less than 56 bits, so it can be flattened (the declared value class Point with two int fields is too big to be flattened), and then declare contended fields using the exact type of the field, not a super type.

To test contended/value types/oopmap interactions, I'd recommend to declare a value type containing a reference type and a small primitive type (for instance value record Opt(Object o, boolean b) { } ), and then declare contended fields of this exact type. This kind of value type would be flattened in VMs using compressed oops, and not flattened in VMs using full size oops, creating two distinct patterns of field layouts including oops and contended padding.

Updated using Small(int x) for flattened value fields and Opt(Object o, boolean b) for oop map interaction testing, with exact types on all @contended fields.

[fparain]

Looks good to me.
Thank you for the changes.

[shivshah-oracle]

/integrate

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@shivshah-oracle
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