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I am trying to experiment with the JVMCI and its existence in the JDK using the following from a mailing list-

private static void JVMCIQueries() {
    // Check if the JDK used supports JVMCI?
    String vm_version = System.getProperty("java.vm.version");
    System.out.printf("java.vm.version = %s%n", vm_version);

    HotSpotDiagnosticMXBean bean = ManagementFactory.getPlatformMXBean(HotSpotDiagnosticMXBean.class);

    // Is JVMCI enabled by default?
    VMOption enableJVMCI = bean.getVMOption("EnableJVMCI");
    System.out.println(enableJVMCI);

    // Is the system using the JVMCI compiler for normal compilations?
    VMOption useJVMCICompiler = bean.getVMOption("UseJVMCICompiler");
    System.out.println(useJVMCICompiler);

    // What compiler is selected?
    String compiler = System.getProperty("jvmci.Compiler");
    System.out.printf("jvmci.Compiler = %s%n", compiler);
}

(edit) With VM arguments as :

-XX:+UnlockExperimentalVMOptions -XX:+EnableJVMCI -XX:+UseJVMCICompiler

Java 10(2018-03-20) Result

java.vm.version = 10+46
VM option: EnableJVMCI value: true  origin: VM_CREATION (read-only)
VM option: UseJVMCICompiler value: true  origin: VM_CREATION (read-only)
jvmci.Compiler = null

Java 9.0.4 Result

java.vm.version = 9.0.4+11
VM option: EnableJVMCI value: true  origin: VM_CREATION (read-only)
VM option: UseJVMCICompiler value: true  origin: VM_CREATION (read-only)
jvmci.Compiler = null

but this is accompanied by logs which complains 

jdk.vm.ci.common.JVMCIError: no JVMCI compiler selected
  at jdk.internal.vm.ci/jdk.vm.ci.hotspot.HotSpotJVMCICompilerConfig$DummyCompilerFactory.compileMethod(HotSpotJVMCICompilerConfig.java:45)
  at jdk.internal.vm.ci/jdk.vm.ci.hotspot.HotSpotJVMCICompilerConfig$DummyCompilerFactory.compileMethod(HotSpotJVMCICompilerConfig.java:42)
  at jdk.internal.vm.ci/jdk.vm.ci.hotspot.HotSpotJVMCIRuntime.compileMethod(HotSpotJVMCIRuntime.java:433)

When with both the versions the jvmci.Compiler value is null, what does no JVMCI compiler selected exactly mean here for 9.0.4(why not in 10)?

This might sound silly or unrelated, but am I falling back to the part where I should be aware of Does Java 9 include Graal? ? Since I thought, even if 9.0.4 doesn't, I haven't specified the same on Java10 either(the -Djvmci.Compiler flag). Any default configurations that might have changed?

Note: Using MacOS(x64) for all of the above.

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