[Vm-dev] Tracing a Spur Image from Smalltalk

[Eliot Miranda]

On Fri, Feb 26, 2016 at 11:27 AM, David T. Lewis <lewis at mail.msen.com>
wrote:

>
> That is very good news! The Cuis folks will be happy to hear about this
> also, as there has been recent discussion on the Cuis list about how to do
> a transition to Spur format.
>

Alas the tracer is unlikely to work as one needs to add extra methods.  I
have been remiss in helping the Cuis folks transition.  I have been
distracted with 64-bit work.  The situation right now is that a script that
installs the revised Float (SmallFloat64 & BoxedFloat64) hierarchy needs
rewriting for Cuis and I haven't got round to it.  Forgive me.




> If I recall right, the issue with tracing and resuming on Cog had to do
> with resuming in the middle of a method of a jitted method. I don't think
> that I ever positively confirmed that theory, but things worked fine under
> an interpreter and it was a trivial step to re-save from Cog.
>

At least from the image level the difference in e.g. pc in the active
context shouldn't be visible.  If it is then there's a bug in Cog.


>
> Dave
>
> >
> > I've updated the SystemTracer package to trace a Spur-format image.
> >
> > This works as far as I can tell, producing a header that looks just like
> > the
> > header produced by the VM and the objects written also look good. I can
> > also
> > open the image in RSqueak, but not on Spur. It crashes immediately and
> > produces a Smalltalk backtrace that looks like it never manages to return
> > from the image-saving method (but the names in the Stack-trace all look
> > ok,
> > leading me to believe that enough objects got written ok to figure out
> > classes, method names, find the right Process to run and so forth).
> >
> > Curiously, the old SystemTracer2 class that writes Cog-format images also
> > produces images that cannot be opened by Cog VMs, only Interpreter VMs.
> So
> > I
> > assume there are other assumptions that maybe the JIT makes when starting
> > up.
> >
> > So my question is, what assumptions could there be, and where could I
> > start
> > looking.
> >
> > Cheers,
> > Tim
> >
> > (If you're wondering why I'm using the Smalltalk-level tracing at all -
> in
> > our quest to create (with RSqueakVM) a Squeak VM that runs Squeak code
> > fast
> > enough that we no longer have to rely on C code from plugins or optional
> > primitives, we're trying to see how far we can push this, and e.g. write
> > the
> > image from within itself, too.)
> >
> >
> >
> > --
> > View this message in context:
> > http://forum.world.st/Tracing-a-Spur-Image-from-Smalltalk-tp4881224.html
> > Sent from the Squeak VM mailing list archive at Nabble.com.
> >
>
>
>


-- 
_,,,^..^,,,_
best, Eliot
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