Regression from JDK-8330386.

java -Xmx1G -XX:+IgnoreUnrecognizedVMOptions -XX:CompileCommand=quiet -XX:CompileCommand=compileonly,*Test*::* -Xcomp -XX:MaxRAMPercentage=6.25 Test.java

# A fatal error has been detected by the Java Runtime Environment:
#
# Internal Error (/workspace/open/src/hotspot/share/opto/node.hpp:891), pid=1322428, tid=1322442
# assert(is_Bool()) failed: invalid node class: Phi

Current CompileTask:
C2:4477 107 b 4 Test::mainTest (814 bytes)

Stack: [0x0000fffd1a3d0000,0x0000fffd1a5d0000], sp=0x0000fffd1a5cb710, free space=2029k
Native frames: (J=compiled Java code, j=interpreted, Vv=VM code, C=native code)
V [libjvm.so+0x11a8530] Matcher::collect_null_checks(Node*, Node*)+0x3a0 (node.hpp:891)
V [libjvm.so+0x11b1474] Matcher::xform(Node*, int)+0x10c4
V [libjvm.so+0x11b4774] Matcher::match()+0xf40
V [libjvm.so+0x8cdbb4] Compile::Code_Gen()+0x90
V [libjvm.so+0x8d0134] Compile::Compile(ciEnv*, ciMethod*, int, Options, DirectiveSet*)+0x1540
V [libjvm.so+0x72bd30] C2Compiler::compile_method(ciEnv*, ciMethod*, int, bool, DirectiveSet*)+0x17c
V [libjvm.so+0x8dbd8c] CompileBroker::invoke_compiler_on_method(CompileTask*)+0x7cc
V [libjvm.so+0x8dc8d4] CompileBroker::compiler_thread_loop()+0x514
V [libjvm.so+0xd3f34c] JavaThread::thread_main_inner()+0xcc
V [libjvm.so+0x159f660] Thread::call_run()+0xac
V [libjvm.so+0x12f6a04] thread_native_entry(Thread*)+0x130
C [libpthread.so.0+0x7950] start_thread+0x190