8383823: C2: Meet not symmetric for TypeAryKlassPtr types

[hgqxjj]

Description:

While working on another C2 type-analysis PR (#30690), I used TypeKlassPtr::filter(). This exposed a Meet Not Symmetric assert in some GHA test jobs involving TypeAryKlassPtr.

The issue is in TypeAryKlassPtr::xmeet(). meet_aryptr() may widen the outer array klass pointer from Constant to NotNull, but the element klass pointer may still keep the more precise type computed before that widening.The resulting TypeAryKlassPtr can then fail the meet/dual symmetry check and trigger the Meet Not Symmetric assert.

Solution:

When meet_aryptr() returns NOT_SUBTYPE and widens the outer array klass pointer from Constant to NotNull, recompute the element klass pointer meet after lowering AnyNull element klass pointers to NotNull.

Test:

GHA

No standalone regression test has been added yet. I have not yet been able to reduce the failure to a small standalone test case.

The issue is reproducible through the other in-progress C2 type-analysis PR (#30690) which uses TypeKlassPtr::filter(). With this fix applied, the Meet Not Symmetric assert no longer reproduces in those GHA test jobs.

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Issue

• JDK-8383823: C2: Meet not symmetric for TypeAryKlassPtr types (Bug - P4)

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