Even after recent fixes like
https://bugs.openjdk.org/browse/JDK-8305765
the test runtime/CompressedOops/CompressedClassPointers.java fails on AIX.

example output of a failing test:
----------System.err:(22/1306)----------
 stdout: [[0.015s][info][gc,metaspace] Compressed class space mapped at: 0x0000012200000000-0x0000012240000000, reserved size: 1073741824
[0.015s][info][gc,metaspace] Narrow klass base: 0x0000012200000000, Narrow klass shift: 0, Narrow klass range: 0x40000000
];
 stderr: [OpenJDK 64-Bit Server VM warning: Shared spaces are not supported in this VM
openjdk version "23-internal" 2024-01-03
OpenJDK Runtime Environment (build 23-internal-adhoc.sapmachine.jdk)
OpenJDK 64-Bit Server VM (build 23-internal-adhoc.sapmachine.jdk, mixed mode)
]
 exitValue = 0

java.lang.RuntimeException: 'Narrow klass base: 0x0000000000000000' missing from stdout/stderr
at jdk.test.lib.process.OutputAnalyzer.shouldContain(OutputAnalyzer.java:244)
at CompressedClassPointers.largeHeapTestNoCoop(CompressedClassPointers.java:265)
at CompressedClassPointers.main(CompressedClassPointers.java:351)
at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:103)
at java.base/java.lang.reflect.Method.invoke(Method.java:580)
at com.sun.javatest.regtest.agent.MainActionHelper$AgentVMRunnable.run(MainActionHelper.java:333)
at java.base/java.lang.Thread.run(Thread.java:1570)

This error results from the fact, that on AIX the shmat() allocation granularity is 256MB instead of the standard Pagesize (4KB or 64KB).