JDK-8311946 added support for jtreg @require property `vm.libgraal.enabled`. This property is true when libgraal is used as the (Java) JIT compiler.

However, the name could be misleading, since libgraal can be "enabled" for use by non-CompilerBroker compilations, without being used as the JIT compiler. This would be the case in a distro that ships GraalJS (for example) atop libgraal, while leaving C2 active for Java code.