$ cd test/hotspot/jtreg/testlibrary/ctw
$ make
$ cd dist
$ wget https://repo1.maven.org/maven2/com/liferay/com.liferay.wiki.service/2.0.8/com.liferay.wiki.service-2.0.8.jar
$ JAVA_OPTIONS="-XX:+AbortVMOnCompilationFailure -XX:+UnlockExperimentalVMOptions -XX:+UseShenandoahGC -XX:+ShenandoahVerifyOptoBarriers" ./ctw.sh com.liferay.wiki.service-2.0.8.jar

# Internal Error (/home/shade/trunks/jdk-jdk/src/hotspot/share/compiler/compileBroker.cpp:2009), pid=18437, tid=18447
# fatal error: Not compilable at tier 4: malformed control flow
#
# JRE version: OpenJDK Runtime Environment (15.0) (fastdebug build 15-internal+0-adhoc.shade.jdk-jdk)
# Java VM: OpenJDK 64-Bit Server VM (fastdebug 15-internal+0-adhoc.shade.jdk-jdk, mixed mode, sharing, tiered, compressed oops, shenandoah gc, linux-amd64)
# Problematic frame:
# V [libjvm.so+0x882133] CompileBroker::post_compile(CompilerThread*, CompileTask*, bool, ciEnv*, int, char const*)+0x1b3

It looks Shenandoah-specific, as I could not get it to fail with G1. (It requires additional -XX:MaxNodeLimit=240000 -XX:NodeLimitFudgeFactor=6000 to get past the node limits).