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From "Rana Dasgupta" <rdasg...@gmail.com>
Subject Re: [DRLVM] adding write barriers to Jitrino.JET
Date Wed, 31 May 2006 21:10:37 GMT
On 5/31/06, Ivan Volosyuk <ivan.volosyuk@gmail.com> wrote:
> 2006/5/31, Mikhail Fursov <mike.fursov@gmail.com>:
> >> No, this method is used to store operand stack item to local
> variable.  If
> >> you're interested in writing to fields then Compiler::gen_field_op is
> the
> >> right place. We can generate a call to VM or GC helper in this method.
> To
> >> create a call to any VM helper (which may throw Exception or force GC)
> you
> >> should use Compiler::gen_call_vm() method.
> >FYI: Write barrier GC implementation doesn't throw exceptions or
> >starts garbage collection. The whole idea of write barriers is to make
> >them as lightweight as possible.

  gen_call_vm() is  more heavyweight( as Ivan explains above ), but that's
why the  higher level goals of this feature development would be good to
know. Prototyping in .Jet cannot really have a performance focus.
 Weldon, would it be right to call this a proof of concept, to be later
redone in the .OPT jit when necessary?

>> It seems not to be a problem to implement WB support in Jitrino.JET,
> let's
> >> discuss requirements and design.
> >> How will it affect VM or GC ? The WBs will also require support from
> both VM
> >> and GC. Do you have ideas on VM/GC interface for this?
> > >Also what will be usage and testing scenarios in the nearest future?
> >The VM<>GC interfaces is already exists in DRLVM. The only interface
> >is missing: JIT->VM helper.

  Not sure that I understood what you said here...are you saying that the
VM_GC interface has (stubbed out) barriers related entries( eg.,
gc_requires_barrier()/gc_write_barrier()), but the JIT->VM Helper runtime
support interface does not have the necessary barrier helper entries in this
code version?

  It may be worth considering if we want JET to just call the barrier
functionality( with from/to/and slot locations )and the barrier helper
actually do everything ... including generating the store. May be
unconventional, but more modular.


> Ivan
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