if -Xconcgc, -XX:+UseConcMarkSweepGC or other flags enable CMS GC, all compiler/jvmci tests fail w/
jdk.vm.ci.common.JVMCIError: unimplemented
at jdk.vm.ci.common.JVMCIError.unimplemented(JVMCIError.java:36)
at jdk.vm.ci.hotspot.HotSpotVMConfig.<init>(HotSpotVMConfig.java:95)
at jdk.vm.ci.hotspot.HotSpotJVMCIRuntime.<init>(HotSpotJVMCIRuntime.java:128)
at jdk.vm.ci.hotspot.HotSpotJVMCIRuntime.<init>(HotSpotJVMCIRuntime.java:40)
at jdk.vm.ci.hotspot.HotSpotJVMCIRuntime$DelayedInit.<clinit>(HotSpotJVMCIRuntime.java:67)
at jdk.vm.ci.hotspot.HotSpotJVMCIRuntime.runtime(HotSpotJVMCIRuntime.java:82)
at jdk.vm.ci.runtime.JVMCI.initializeRuntime(Native Method)
at jdk.vm.ci.runtime.JVMCI.<clinit>(JVMCI.java:58)
at jdk.vm.ci.runtime.test.TypeUniverse.<clinit>(TypeUniverse.java:50)

UseSerialGC leads to the same exception.