We noticed that compiler/vectorapi/VectorMaskCompareNotTest.java fails when running on Power8 on which we don't use the 128 Bit VectorRegisters by default (-XX:-SuperwordUseVSX).
Like on RISC-V without RVV, ofLargestShape(long.class) falls back to 64 bits (see getMaxVectorBitSize in VectorShape.java),
leading to VectorShape.forBitSize(32) which is unsupported and throws IllegalArgumentException.

Error log:
```
----------System.out:(0/0)----------
----------System.err:(16/1209)----------
WARNING: Using incubator modules: jdk.incubator.vector
java.lang.ExceptionInInitializerError
at java.base/jdk.internal.misc.Unsafe.ensureClassInitialized0(Native Method)
at java.base/jdk.internal.misc.Unsafe.ensureClassInitialized(Unsafe.java:1195)
at java.base/jdk.internal.reflect.MethodHandleAccessorFactory.ensureClassInitialized(MethodHandleAccessorFactory.java:341)
at java.base/jdk.internal.reflect.MethodHandleAccessorFactory.newMethodAccessor(MethodHandleAccessorFactory.java:72)
at java.base/jdk.internal.reflect.ReflectionFactory.newMethodAccessor(ReflectionFactory.java:119)
at java.base/java.lang.reflect.Method.acquireMethodAccessor(Method.java:711)
at java.base/java.lang.reflect.Method.invoke(Method.java:562)
at com.sun.javatest.regtest.agent.MainWrapper$MainTask.run(MainWrapper.java:138)
at java.base/java.lang.Thread.run(Thread.java:1474)
Caused by: java.lang.IllegalArgumentException: Bad vector bit-size: 32
at jdk.incubator.vector/jdk.incubator.vector.VectorShape.forBitSize(VectorShape.java:142)
at compiler.vectorapi.VectorMaskCompareNotTest.<clinit>(VectorMaskCompareNotTest.java:56)
... 9 more
STATUS:Failed.`main' threw exception: java.lang.ExceptionInInitializerError
```