[Libre-soc-bugs] [Bug 981] Support PowerPC ABI in cavatools

[bugzilla-daemon at libre-soc.org]

https://bugs.libre-soc.org/show_bug.cgi?id=981

--- Comment #15 from Andrey Miroshnikov <andrey at technepisteme.xyz> ---
(In reply to Dmitry Selyutin from comment #13)
> Hi Andrey, some questions from my side.
> 
> 1. Am I right that works on cavatools itself are frozen and the commits will
> not be used?

We're missing most of the code required to actually use cavatools (no support
for PowerISA). So at present these commits cannot be used (*they will be in the
future*, so this task will be funded of course).

Luke mentioned in #c10:

(In reply to Luke Kenneth Casson Leighton from comment #10)
> reminder that this is why cavatools has its own memory-allocator
> override and iirc free() is a stub that does not actually de-allocate.
> you'll need to look at the source code closely to confirm, then
> copy-cat that in ISACaller.

So perhaps you could do an investigation (doesn't require new code, just
document your findings) on what it would take to re-use the cavatools code in
ISACaller. This can be funded as moving towards cavatools support.
If it's not a lot of work to actually modify ISACaller code, then could be
considered as a sub-task, but prioritise research.

> 2. Am I right that we need to continue to work on 982 to allow a thin set of
> syscalls (I suggest the same limited set as in cavatools, not more)?

Yes, that's correct.

> 3. What'd be the budget? The only reason I set budget in 982 so low is that
> I counted on 981 being used. And, in fact, considering amount of work and
> progress, even at this point I expected this task budget plus the amount
> from 982bassigned to me at this point already.
> 
> Could you please clarify your vision on this?

Dmitry, I'm happy for you to get most of the budget for bug #982, as well as
the entirety of bug #981, with the included research sub-task I've suggested
above.

(In reply to Dmitry Selyutin from comment #14)
> I must confess that it is a strange news. During our meetings I mentioned
> several times that I'm working on this, discussed the budget and whether
> this task should be moved or not, did all works and then found it's
> effectively cancelled. I'd prefer not to waste my energy and do something
> more practical if I knew that in advance. Please provide some rationale.

I apologise Dmitry, there's been much confusion and I'm catching up myself.
The reason I said to focus on ISACaller, is because we can use it right now, to
aid both general LibreSOC development, as well plan for cavatools work (the
original scope of this grant was simply too ambitious, so we'll need more time
and resources to get what intially planned).
That said, given your rapid progress, I'm not against you studying cavatools a
little more, even just to learn about some of its tricks which we can carry
over to ISACaller (until we have sufficient funding and people to actually port
PowerISA over to cavatools).

Luke, I hope this is satisfactory. My reasoning to those answers is primarily
to get the grant over and done with, while at the same time giving Dmitry the
opportunity to expand our knowledge and potentially improve ISACaller.

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