On Tue, Jul 07, 2015 at 05:20:52PM -0700, Eliot Miranda wrote:
> Hi David,
> 
> On Tue, Jul 7, 2015 at 4:33 PM, David T. Lewis <lewis at mail.msen.com> wrote:
> >
> > The problem was introduced in Compiler-eem.300, which does this:
> >
> >     Use the size/emitPushNClosureTemps: api in block generation.
> >
> > There are two affected methods:
> >
> >     BlockNode>>sizeCodeForEvaluatedClosureValue:
> >     BlockNode>>emitCodeForEvaluatedClosureValue:encoder:
> >
> > Reverting these two methods fixes the problem.
> >
> > I don't know the background on this change but my guess would be that
> > it is something that works on a stack interpreter but not on a context
> > interpreter, so maybe the methods need to be tweaked to account for the
> > difference.
> >
> 
> It should make no difference to the code produced.  It adds a new way of
> saying "push N nils" that allows the Sista bytecode set to use its
> "pushNClosureNils" bytecode to push several nils in one bytecode.  But with
> the standard encoder EncoderForV3PlusClosures exactly the same code as the
> previous version should be produced.
> 
> How do the changes in the compiler cause the crash?
> 

I don't know.

I'm doing brute-force debugging, just rolling the versions back until the
problem goes away.

All I can say with confidence is that those two methods changes, followed by
a system recompile, result in an image that crashes a context interpreter VM.
Reverting these two methods and recompiling brings the image back to a sane
condition.

It might turn out to be a trivial problem, but I am suggesting that we should
temporarily revert and work it out after the 4.6 release.

Dave