Re: [PATCH] target/xtensa: import core lx106

[Max Filippov]

On Sun, Apr 24, 2022 at 10:40 PM Simon Safar <simon@simonsafar.com> wrote:
> On Sat, Apr 23, 2022, at 2:26 PM, Max Filippov wrote:
> > It's for a (future...) Lisp compiler! Somewhat in the style of MicroPython; 
> > the idea
> > is to make code editable on the fly, without reflashing (... or restarting, 
> > even).
>
> Interesting. Do you use libisa or do you do instruction encoding on your own?
>
> It's my own; it's generating opcodes from the tree of tables in the Xtensa 
> reference.
> A large part of the actual code looks a lot like those tables themselves; 
> there are still
> some missing parts for some (e.g. overriding some defaults on which 
> instruction is
> taking what kinds of parameters), which I'm just filling in on the go.

I see. I once did something like that for QEMU TCG:
https://github.com/OSLL/qemu-xtensa/commit/53604287d6fdad1ce9659135a8ecbb569be90380

> It's fairly hacky, but it might fit together well with the eventual purpose 
> of maybe
> running some of this in that 40k RAM onboard & keeping it all Lisp.

40k of RAM is a reasonable concern (: I would guess though that libisa + xtensa
core description are purely code and constant data, and as such they may be
put into FLASH and not consume any RAM.

> (I'll put it up somewhere eventually once it's not a complete mess & starts 
> doing
> something interesting! assuming this ever happens, of course.)

Have fun and good luck!

-- 
Thanks.
-- Max