Many crashes with SIGILL have been seen on PPC64 since JDK-8319055:

# V [libjvm.so+0xd3fa54] AttachOperation::ReplyWriter::write_fully(void const*, int)+0x74

Stack: [0x0000000118f00000,0x000000011911d888], sp=0x000000011911cf00, free space=2163k
Native frame:
iar: 0x0000000000000000 (unknown module)::(unknown function)+?
lr: 0x090000000cb98a54 libjvm.so::AttachOperation::ReplyWriter::write_fully(void const*, int)+0x74 (C++ uses_alloca saves_lr stores_bc gpr_saved:1 fixedparms:3 parmsonstk:1)
sp: 0x000000011911cf00 (base - 0x988)
rtoc: 0x0000000000000000 (invalid)
|---stackaddr----| |----lrsave------|: <function name>
0x000000011911cfd0 - 0x090000000cb988e4 libjvm.so::AttachOperation::ReplyWriter::write_reply(int, char const*, int)+0xa4 (C++ uses_alloca saves_lr stores_bc gpr_saved:1 fixedparms:4 parmsonstk:1)
0x000000011911d0d0 - 0x090000000cb987d0 libjvm.so::AttachOperation::ReplyWriter::write_reply(int, bufferedStream*)+0x70 (C++ uses_alloca saves_lr stores_bc gpr_saved:1 fixedparms:3 parmsonstk:1)
0x000000011911d180 - 0x090000000cb9867c libjvm.so::attachStream::flush_reply()+0x5c (C++ uses_alloca saves_lr stores_bc gpr_saved:1 fixedparms:1 parmsonstk:1)
0x000000011911d220 - 0x090000000cb9b308 libjvm.so::attachStream::complete()+0x48 (C++ uses_alloca saves_lr stores_bc gpr_saved:1 fixedparms:1 parmsonstk:1)
0x000000011911d2d0 - 0x090000000cb97bc8 libjvm.so::AttachListenerThread::thread_entry(JavaThread*, JavaThread*)+0x488 (C++ uses_alloca saves_lr stores_bc gpr_saved:1 fixedparms:2 parmsonstk:1)
0x000000011911d470 - 0x090000000c2c4104 libjvm.so::JavaThread::thread_main_inner()+0x184 (C++ uses_alloca saves_lr stores_bc gpr_saved:1 fixedparms:1 parmsonstk:1)
0x000000011911d570 - 0x090000000c2c27a8 libjvm.so::JavaThread::run()+0x1c8 (C++ uses_alloca saves_lr stores_bc gpr_saved:1 fixedparms:1 parmsonstk:1)
0x000000011911d600 - 0x090000000c0819f8 libjvm.so::Thread::call_run()+0x1d8 (C++ uses_alloca saves_lr stores_bc gpr_saved:1 fixedparms:1 parmsonstk:1)
0x000000011911d6a0 - 0x090000000c080784 libjvm.so::thread_native_entry(Thread*)+0x244 (C++ uses_alloca saves_lr stores_bc gpr_saved:1 fixedparms:1 parmsonstk:1)
0x000000011911d7a0 - 0x090000000056204c libpthreads.a::_pthread_body+0xec (C saves_lr stores_bc gpr_saved:1 fixedparms:1 )
0x000000011911d820 - 0x0000000000000000

They disappear when backing out JDK-8319055.
Reproducible by e.g. "make run-test TEST=runtime/cds/DumpSymbolAndStringTable.java".