Assertion failed: int pressure is incorrect

[Andrew Haley]

I'm occasionally seeing this:

# A fatal error has been detected by the Java Runtime Environment:
#
#  Internal Error (/scratch1/large-codecache/hotspot/src/share/vm/opto/ifg.cpp:693), pid=9212, tid=4395909313024
#  assert(int_pressure.current_pressure() == count_int_pressure(liveout)) failed: the int pressure is incorrect
#

Does anyone know what might cause this?  Perhaps a bug in my back
end?  If not, can I please have some advice about how to debug it?

I'm only seeing this with a fairly recent cut of JDK9.

Thanks,
Andrew,