RFR: 8177845: Need a mechanism to load Graal

Doug Simon doug.simon at oracle.com
Wed Apr 19 07:16:08 UTC 2017

(adding hotspot-compiler-dev)

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-8177673, 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.



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

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