Seen in jdk_jfr tests like:

$ CONF=linux-x86_64-server-fastdebug make run-test TEST=jdk/jfr/event/oldobject/TestShenandoah.java

# Internal Error (/home/shade/trunks/jdk/src/hotspot/share/opto/phaseX.cpp:1367), pid=483318, tid=483340
# assert(dead != C->root()) failed: killing root, eh?

Current CompileTask:
C2: 1353 486 4 java.io.DataInputStream::readUTF (501 bytes)

Stack: [0x00007ff89c8f8000,0x00007ff89c9f9000], sp=0x00007ff89c9f2f50, free space=1003k
Native frames: (J=compiled Java code, j=interpreted, Vv=VM code, C=native code)
V [libjvm.so+0x167e614] PhaseIterGVN::remove_globally_dead_node(Node*)+0x404
V [libjvm.so+0x13796d1] PhaseIdealLoop::build_and_optimize(LoopOptsMode)+0x551
V [libjvm.so+0xaafcc7] PhaseIdealLoop::optimize(PhaseIterGVN&, LoopOptsMode)+0x287
V [libjvm.so+0x18a7400] ShenandoahBarrierC2Support::expand(Compile*, PhaseIterGVN&)+0x70
V [libjvm.so+0x17ccfd3] ShenandoahBarrierSetC2::expand_barriers(Compile*, PhaseIterGVN&) const+0x13
V [libjvm.so+0xaad1fd] Compile::Optimize()+0x12fd
V [libjvm.so+0xaae71e] Compile::Compile(ciEnv*, ciMethod*, int, Options, DirectiveSet*)+0x127e
V [libjvm.so+0x8cdecb] C2Compiler::compile_method(ciEnv*, ciMethod*, int, bool, DirectiveSet*)+0x69b
V [libjvm.so+0xac0118] CompileBroker::invoke_compiler_on_method(CompileTask*)+0xe48
V [libjvm.so+0xac0e88] CompileBroker::compiler_thread_loop()+0x648
V [libjvm.so+0x1a20b1c] JavaThread::thread_main_inner()+0x28c
V [libjvm.so+0x1a26734] Thread::call_run()+0x104
V [libjvm.so+0x15ff56c] thread_native_entry(Thread*)+0x10c

Bisection points to JDK-8278413.