Graal (i.e. the module jdk.internal.vm.compiler) seems to be missing from the Java 9 EA for MacOS. I noticed this with b166 and it is still so in b167.
As it is perfectly possible to download the source, configure the build to include graal, and build it, I suspect this is possibly an oversight in the packaging of the EA on MacOS, due to that AOT is only to be supported on Linux. But graal per se should surely be included on all platforms?
How to test:
java --list-modules | grep jdk.internal.vm.compiler
(finds compiler on Linux; finds nothing on MacOS)
java -XX:+UnlockExperimentalVMOptions -XX:+EnableJVMCI -XX:+UseJVMCICompiler -XX:+BootstrapJVMCI -version
(Works on Linux; complains about "no JVMCI compiler selected" on MacOS)