[Vm-dev] processor emulation, and Status of PowerPC

[Boris Shingarov]

>   
>
> Well given that two of the solutions work fine and that Boris Shingarov is investigating using the Gem5 simulators, trying to unify has no point.  It’s just work.  But if it excites you, go for it.  I don’t have spare cycles :-)

Alright, now that my name got mentioned in this discussion, I'll chime 
in to explain where we are with that project.

The idea is to use the widely-adopted GDB interfaces to drive the 
debugging of the VM on a wide range of targets, so that the difference 
between Simulation and Production mode is erased. Indeed I have booted 
up Cog interchangeably on purely-software-emulated CPU, on hard-silicon, 
and on FPGA, completely transparently to Cog and the VMSimulator.

More interestingly, the Smalltalk API to the underlying GDB is designed 
to admit also other backends, such as the Angr symbolic execution 
engine.  This will server as the basis of Cog's formal verification 
(although I have not yet booted full Cog symbolically, only small 
fragments).

What works today?  We have been running simulations of existing i386 and 
ARM Cog both on gem5 and on off-the-shelf hardware for several months, 
both in Squeak and Pharo host images (the code for both environments is 
publicly available).

The all-new PowerPC backend successfully boots to the Reader prompt.  
The code is available at

https://github.com/shingarov/opensmalltalk-vm

https://github.com/shingarov/SmallRSP

https://github.com/shingarov/Pharo-ArchC

https://github.com/shingarov/MachineArithmetic

Setting it up is highly nontrivial, but not a 
"kids-please-don't-try-this-at-home" kind of deal.  On the contrary, I 
invite everyone interested and I am willing to show you how to run it.

This is obviously a very long way from being usable for actual Smalltalk 
app development by customers; if there is interest, we can talk about 
what the next steps need to be.