Indicates a path in HotSpot JVMCI related code that is unsupported in the current execution environment. For example, certain operations are not supported by JVMCI code running in an ahead of time compiled native image. This usually reflects functionality only needed in non-native image execution that would require a more complex implementation to support in a native image. An example of such functionality is ResolvedJavaType#isLocal(). This can be conveniently implemented when JVMCI is running on the HotSpot heap as we can obtain the Class mirror for the ResolvedJavaType and call Class#isLocalClass(). In a native image, there is no Class mirror available in the native image heap so implementing this would involve a call into VM native code that in turn would make an upcall into Java code executing on the HotSpot heap. We have opted to defer implementing functionality such as this until there's a demonstrated need for it.