Draft JEP on enhanced volatiles
paul.sandoz at oracle.com
Mon Feb 10 11:46:44 UTC 2014
On Feb 9, 2014, at 1:52 PM, Remi Forax <forax at univ-mlv.fr> wrote:
> On 02/08/2014 06:52 PM, Brian Goetz wrote:
>>> can you be a little more specific and provide the way
>>> foo.volatile.compareAndSet is compiled with this example:
>> Hey, the JEP isn't even out of draft yet! Stop asking hard questions.
>> The current strawman, though, is to expose direct (CP-ready) MH forms (Lookup API / constant pool format TBD) for field get/set with fence, array element get/set with fence, field CAS, and array element CAS. Then the static compiler translates
>> LDC #MH[lookupFieldCASer(foo)]
>> aload n
>> aload m
>> invokevirtual "invokeExact"
> wow, you bring out the big guns !
> I see a big issue with this approach, it requires to change the JVM spec each time you want to add a new operation.
Yes, although realistically i would expect new operations only to be added with each major release.
> Moreover, overloads of LDC are usually re-written by JVMs has private opcodes, so why not directly use new opcodes,
> it will take less space in the classfile too.
More work than expanding the kinds of method handle?
I have not looked at this in detail but perhaps there might be a few new reference_kind items (for get/put/static fields) that can refer to a new constant pool entry consisting of a pair of CONSTANT_Fieldref_info and CONSTANT_InterfaceMethodref_info for VirtualXXX iface?
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