8375548: [lworld] C2: Support value class arrays with compiler replay

[chhagedorn]

When using compiler replay with --enable-preview with array store/load profiling, we only create ObjArrayKlass objects instead of subclass objects (i.e. RefArrayKlass or FlatArrayKlass). The reason is that we are directly resolving klasses with SystemDirectory::resolve_or_fail():

valhalla/src/hotspot/share/ci/ciReplay.cpp

Line 557 in a4fb7eb

k = SystemDictionary::resolve_or_fail(klass_name, _loader, true, THREAD);

This method will call InstanceKlass::array_klass() at some point which directly creates an ObjArrayKlass object. This let's the replayed compilation fail when trying to speculate on an value class array which expects a subclass of ObjArrayKlass.

The fix I propose is to make sure that we are always creating subclass objects by explicitly using ArrayProperties::DEFAULT when parsing an ArrayKlass during replay compilation.

I added a compiler replay test which triggers the same assert as shown in the report.

Thanks,
Christian

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Issue

• JDK-8375548: [lworld] C2: Support value class arrays with compiler replay (Bug - P4)

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[TobiHartmann]

This will always create the default refined klass. Shouldn't we keep track of which refined klass was actually referenced in the replay file and then create that particular one here?

[chhagedorn]

Good point! I reverted this fix and added proper support for value class arrays by dumping the array properties to the replay file. I've also added some more extended testing.

[chhagedorn]

I've shared some code with this class which already did some of the things required for the new tests.