In LogParser.java around 724, when the tool is starting up it goes to fill in the types based on the tags in the xml input file. Below

    void type(String id, String name) {
        assert type(id) == null;

calls
    String type(String id) {
        String result = types.get(id);
        if (result == null) {
            reportInternalError(id);
        }

but we are just starting to fill in the types table so it is empty at this point leading to the reportInternalError()


See here for the whole file:
http://hg.openjdk.java.net/jdk9/jdk9/hotspot/file/b756e7a2ec33/src/share/tools/LogCompilation/src/com/sun/hotspot/tools/compiler/LogParser.java