jdk.internal.vm.compiler is a stripped down version of Graal. As Graal contains overlapped packages, Graal currently builds a module named `jdk.internal.vm.compiler` and replace the one in JDK using `--patch-module` to disable the hash check that is used to ensure only upgradeable modules to be upgraded [1]:

   --upgrade-module-path=graal.jar \
   --patch-module=jdk.internal.vm.compiler=.jar

The above will not work once JDK-8177844 is resolved since jdk.internal.vm.compiler is not upgradeable. Graal should build a module with a different name e.g. `graal.vm.compiler` since jdk.internal.vm.compiler can't be upgraded.

Two possible solutions to explore:
1. Repackaging - this option is undesirable as it makes the merge process complicated.

2. Load graal.vm.compiler in a child layer and replace the ServiceLoader.load(Class, ClassLoader) call to load the JVMCI provider with ServiceLoader.load(Layer, Class)
 
[1] http://mail.openjdk.java.net/pipermail/jigsaw-dev/2017-February/011413.html