This started to happen after UseCompressedOops test was enabled back by JDK-8217580:

Command line: [/home/shade/trunks/jdk-jdk/build/linux-x86_64-server-fastdebug/images/jdk/bin/java -cp /home/shade/trunks/jdk-jdk/build/linux-x86_64-server-fastdebug/test-support/jtreg_test_hotspot_jtreg_runtime_CompressedOops_UseCompressedOops_java/classes/0/runtime/CompressedOops/UseCompressedOops.d:/home/shade/trunks/jdk-jdk/test/hotspot/jtreg/runtime/CompressedOops:/home/shade/trunks/jdk-jdk/build/linux-x86_64-server-fastdebug/test-support/jtreg_test_hotspot_jtreg_runtime_CompressedOops_UseCompressedOops_java/classes/0/test/lib:/home/shade/trunks/jdk-jdk/test/lib:/home/shade/Install/jtreg/lib/javatest.jar:/home/shade/Install/jtreg/lib/jtreg.jar -XX:+PrintCompressedOopsMode -Xms32m -XX:+UseShenandoahGC -XX:-UseCompressedOops -Xmx32m -version ]
STDERR:
 stdout: [[0.001s][warning][arguments] -XX:+PrintCompressedOopsMode is deprecated. Will use -Xlog:gc+heap+coops=info instead.
];
 stderr: [Error: VM option 'UseShenandoahGC' is experimental and must be enabled via -XX:+UnlockExperimentalVMOptions.
Error: The unlock option must precede 'UseShenandoahGC'.