"DU iteration must converge quickly" assert in split if with unsafe accesses

# Internal Error (/home/roland/hs10/hotspot/src/share/vm/opto/node.cpp:177), pid=20592, tid=20633
# assert(_refresh_tick < 2*100000) failed: DU iteration must converge quickly

V [libjvm.so+0x9ff332] report_vm_error(char const*, int, char const*, char const*, ...)+0x10b
V [libjvm.so+0x1099bde] DUIterator::reset(DUIterator const&)+0x1c6
V [libjvm.so+0x832bec] DUIterator::operator=(DUIterator const&)+0x40
V [libjvm.so+0x1209116] PhaseIdealLoop::do_split_if(Node*)+0x344
V [libjvm.so+0xf31d67] PhaseIdealLoop::split_if_with_blocks_post(Node*)+0x835
V [libjvm.so+0xf328cc] PhaseIdealLoop::split_if_with_blocks(VectorSet&, Node_Stack&)+0x1c0
V [libjvm.so+0xf249a5] PhaseIdealLoop::build_and_optimize(bool, bool)+0xed1
V [libjvm.so+0x9825e7] PhaseIdealLoop::PhaseIdealLoop(PhaseIterGVN&, bool, bool)+0xbf
V [libjvm.so+0x973870] Compile::Optimize()+0xcca
V [libjvm.so+0x96c316] Compile::Compile(ciEnv*, C2Compiler*, ciMethod*, int, bool, bool, bool, DirectiveSet*)+0x11f4