On Sun, Feb 23, 2020 at 11:17 AM tim Rowledge <tim at rowledge.org> wrote:

>
>
> > On 2020-02-23, at 4:42 AM, Fabio Niephaus <lists at fniephaus.com> wrote:
> >
> > On Sun, Feb 23, 2020 at 1:48 AM tim Rowledge <tim at rowledge.org> wrote:
> > >
> > >
> > > Well, that's interesting. The bug is different on a Raspberry Pi (I
> was hoping non-existent) because the bitblt code is quite different as a
> result of the Pi Foundation paying to get much faster ARM assembler blt
> code written.
> > > Same sort of pattern but not identical. Sigh. This will be 'fun' to
> investigate.
> >
> > Hi Tim,
> > Seems very similar to this:
> > <image.png>
> >
> > This is what it looked like on GraalSqueak without the fix. Note that
> GraalSqueak's BitBlt is written in Java, so it cannot read past forms etc.
> Maybe this is also the case on ARM for some reason?
>
> Yes, that is interesting. It certainly looks identical - so at least the
> bug should be the same to fix!
>
> Having to think about the ARM specialised code reminds me - we really,
> really ought to try to make a way to JIT the blit. I did an ARM version 30+
> years ago but it was all rather simpler back then; no cache to fart around
> with (not just no cache instructions with strange permissions stuff,
> actually no cache at all) and simple monochrome Forms.
>
> We have the key components to hand. It seems like an idea that could be
> widely useful.


I dare say it is trivial with the framework we have in the JIT (but then it
applies only to the JIT VM, not the stack interpreter).


> It would surely make a fine thesis.
>

Dan Amelang's Gezira is much more interesting.  We should productize that.
We have to accept that we badly need a pixel independent imaging model that
can be compiled to and executed by the GPU. The world has moved on and
Squeak is limited by its graphics infrastructure.


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