Please review these changes that make jdk.internal.vm.compiler an upgradable 
compiler.
The primary requirement for this is to remove all usage of JDK internals from 
Graal.
While this most involves changes in Graal, there remain a few capabilities that 
must
be exposed via JVMCI. Namely:

1. Graal needs a copy of jdk.internal.misc.VM.savedProps so that it can Graal 
initialize
   can use system properties that are guaranteed not to have been modified by 
application
   code (Graal initialization is lazy and may occur after application code has 
been run).

2. Truffle needs to be able to trigger JVMCI initialization so that it can 
select the Graal
   optimized implementation of the Truffle runtime.

These capabilities have been added to jdk.vm.ci.services.Services. A comment has
also been added to this class to denote the current methods to be removed
in a subsequent bug to update the JDK copy of Graal with the upstream version 
which
no longer uses the methods. The methods destined for removal are:

exportJVMCITo(Class<?> requestor)
load(Class<S> service)
loadSingle(Class<S> service, boolean required)

The first one is no longer needed as JVMCI exports itself to Graal service 
providers
it loads via private API and Graal re-exports[1] JVMCI to any module the 
extends Graal.
The latter 2 are no longer required as Graal uses the standard ServiceLoader. 
This API
is only useful for JVMCI-8 where a hidden JVMCI class loader is used.

These changes have been tested against upstream Graal. To make the Graal tests 
pass, 2 extra
minor changes were required:

1. In JDK-8177663, HotSpotMemoryAccessProviderImpl::checkRead was added and 
throws IllegalArgumentException
   on all error paths except one which throws AssertionError. The latter was a 
mistake and has been
   fixed to also throw IllegalArgumentException.
2. An invalid assertion has been removed from 
HotSpotResolvedObjectTypeImpl::isDefinitelyResolvedWithRespectTo.
   Up to JDK 8, it was true that all classes in java.* packages were loaded by 
the boot class loader.
   This is no longer true in JDK 9 with classes like java.sql being loaded by 
platform class loader.

As hinted above, a subsequent bug will be required to pull in the latest 
upstream Graal and
remove use of JDK internal API from the jdk.aot module. The qualified exports to
jdk.vm.internal.compiler and jdk.aot can then be removed.

-Doug

https://bugs.openjdk.java.net/browse/JDK-8177845
http://cr.openjdk.java.net/~dnsimon/8177845/

[1] 
http://openjdk.java.net/projects/jigsaw/spec/issues/#IndirectQualifiedReflectiveAccess
   


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