> 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. It would surely make a fine thesis.

tim
--
tim Rowledge; tim at rowledge.org; http://www.rowledge.org/tim
Useful random insult:- Doesn't just know nothing; doesn't even suspect much.