This was detected by the Zero no precompiled headers builder here:
http://builder.classpath.org/jenkins/job/OpenJDK9_hs_rt_Zero_no_pch/9/console
The relevant compile error is:
In file included from /var/lib/jenkins/jobs/OpenJDK9_hs_rt_Zero_no_pch/workspace/openjdk9/hs-rt/hotspot/src/share/vm/gc/g1/g1BiasedArray.cpp:26:0:
/var/lib/jenkins/jobs/OpenJDK9_hs_rt_Zero_no_pch/workspace/openjdk9/hs-rt/hotspot/src/share/vm/gc/g1/g1BiasedArray.hpp:148:23: error: ���MemRegion��� has not been declared
/var/lib/jenkins/jobs/OpenJDK9_hs_rt_Zero_no_pch/workspace/openjdk9/hs-rt/hotspot/src/share/vm/gc/g1/g1BiasedArray.hpp: In member function ���void G1BiasedMappedArray<T>::set_by_address(int, T)���:
/var/lib/jenkins/jobs/OpenJDK9_hs_rt_Zero_no_pch/workspace/openjdk9/hs-rt/hotspot/src/share/vm/gc/g1/g1BiasedArray.hpp:149:44: error: request for member ���start��� in ���range���, which is of non-class type ���int���
/var/lib/jenkins/jobs/OpenJDK9_hs_rt_Zero_no_pch/workspace/openjdk9/hs-rt/hotspot/src/share/vm/gc/g1/g1BiasedArray.hpp:150:43: error: request for member ���last��� in ���range���, which is of non-class type ���int���
make[8]: *** [g1BiasedArray.o] Error 1
make[8]: *** Waiting for unfinished jobs....
It seems the patch for JDK-8079792 introduced this.