SIGSEGV in ShenandoahBarrierC2Support::verify_raw_mem for malformed control flow graph

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# A fatal error has been detected by the Java Runtime Environment:
#
# SIGSEGV (0xb) at pc=0x0000000108e73613, pid=79526, tid=42243
#
# JRE version: OpenJDK Runtime Environment (18.0) (fastdebug build 18-internal+0-adhoc.fool.jdk)
# Java VM: OpenJDK 64-Bit Server VM (fastdebug 18-internal+0-adhoc.fool.jdk, mixed mode, sharing, compressed oops, compressed class ptrs, shenandoah gc, bsd-amd64)
# Problematic frame:
# V [libjvm.dylib+0x1073613] ShenandoahBarrierC2Support::verify_raw_mem(RootNode*)+0x633
#