Hi Claes, Mandy,
On 03/25/2016 02:51 AM, Mandy Chung wrote:
Hi Claes,
This is a good interesting work to generate BoundMethodHandle$Species_* classes at
link time. This will save the class generation time. Instead of Class.forName, you
may want to have a class (similar to SystemModules [1]) that will be updated at link
time so that BoundMethodHandle can reference it statically to determine what species
are generated at link time and even return statically Class<?> of the generated
class.
You may still want to load this classes lazily when needed. Otherwise
the BMH.CLASS_CACHE could simply be pre-populated with name -> Class<?>
entries at appropriate early time.
About CNFE, the new Class.forName(Module, String) method does not throw CNFE
that you could use instead (if not static reference as suggested above). If
not found, it will return null.
This plugin accesses the non-public methods in BoundMethodHandle and has to
invoke it via reflection. With module boundary enforced now, maybe we could
consider moving to some internal package to share with this jlink plugin.
I think there are tests needed to be updated when a new plugin is added.
Mandy
[1]
http://hg.openjdk.java.net/jdk9/dev/jdk/file/3abd25870915/src/java.base/share/classes/jdk/internal/module/SystemModules.java
One thing to consider is the following: the names of the classes obey a
particular convention which is now hardcoded in two places: the
BoundMethodHandle and the GenerateBMHClassesPlugin. You could have a
method with the following signature in BoundMethodHandle$Factory:
Map.Entry<String, byte[]> generateConcreteBMHClassBytes(String types)
...which would also return the name of the class derived from the types
which you would then use to derive the path of the .class file in the
module of the image. Also, this method - although package-private
becomes part of the API and that should be written in a comment.
What do you think?
Regards, Peter
On Mar 24, 2016, at 6:42 AM, Claes Redestad <claes.redes...@oracle.com> wrote:
Hi,
please review this patch which add an enabled-by-default plugin to generate a
configurable list of BoundMethodHandle$Species_*-classes using jlink.
Bug: https://bugs.openjdk.java.net/browse/JDK-8152641
Webrev: http://cr.openjdk.java.net/~redestad/8152641/webrev.01/
This plugin adds the --generate-bmh flag to jlink, which takes a
comma-separated list of shortened species type strings.
As an example: --generate-bmh LL,L3,L4 will generate
BoundMethodHandle$Species_LL, ...$Species_L3 and ...$Species_L4 and add
them to the java.base module.
The Species class lookup in BoundMethodHandle will first check if there is a
generated class, otherwise generate it as previously. Adding an exceptional
path might seem problematic, but as the code generation is magnitudes more
expensive than the exception it doesn't seem fruitful to go to lengths to avoid
the CNFE.
More notes along with some results can be found here:
http://cr.openjdk.java.net/~redestad/scratch/bmh_species_gen.txt
Thanks!
/Claes
