Re: [avr-llvm-devel] Current Status?

[Borja F. <bor...@gm...>]

I can't really say, maybe Eric can help here. What I use to develope the
backend is a pdf of the instruction set, but it doesnt specify what devices
are supported for each instruction.

2012/1/11 Sherard Dames <sc...@gm...>

> Thanks for responding Borja. I do have a question, posed to everyone
> really. Does anyone know where I can find a reference for which
> instructions are available for which AVR architectures? Haven't been
> able to stumble upon one in my searches.
>
> Thanks,
>
> On Tue, 2012-01-10 at 17:35 +0100, Borja Ferrer wrote:
> > Hello everybody,
> >
> > Sorry about the delay of my reply, but I'm very busy this month with
> > my finals. First thing I would like to say is to welcome Sherard. As a
> > short summary, the current status to answer Sherard's question is:
> >
> > Basically most of what is required to compile sequential code (no
> > jumps) is implemented, this includes all memory addressing modes,
> > arithmetic instructions, function calls, passing arguments, etc. Last
> > thing I finished working on before Christmas was frames and stack
> > manipulation. So we can now allocate automatic variables on the stack,
> > pass arguments using the stack, and spill registers.
> > Next thing I'm going to work on are jumps and conditional code, I'll
> > head into this in February when I'm done with my finals, I only had
> > time to implement the jmp instruction which was pretty fast to do, but
> > conditional code requires a lot more of work.
> >
> > Please don't look or work on any code in SVN because that is going to
> > be removed, and I doubt it even compiles with the latest LLVM release.
> > It's my fault because i haven't uploaded yet any of the work I've done
> > out of trunk to SVN but i want to have something in shape before
> > commiting it, I think I will do it once conditional code is done.
> > Looking in SVN is misleading because it looks as the project is dead,
> > but that is totally wrong because we're getting a lot done out of
> > there.
> >
> > About patches, I would say most of them are updated, I commited a
> > patch some weeks ago for the register allocator, but if you want to
> > check them it's ok. Related to code, i think patches are the only
> > useful thing SVN has now, the backend code will go away.
> >
> > Since the LLVM backend code is not yet commited, I would suggest as
> > John said working on regression tests, we're going to need this soon,
> > and we're getting behind on this because we need a good test suite to
> > catch as many errors as possible, so patches there are welcome.
> > Something similar to what the MSP430 backend has would be a decent
> > start. Tests related to arithmetic ops, function calls, testing ABI,
> > and other things you can think of that dont require jumps.
> > Also on the other side, a lot of work is needed in Clang, we need to
> > support many of the custom extensions AVR has like address spaces or
> > interrupt handlers, so work is needed there aswell. We discussed some
> > months ago about how to deal with address spaces but we didnt reach to
> > any formal decisions, so if you want to work on that aswell you're
> > welcome. In fact, if you want to work both with tests and this that
> > would be great :)
> >
> > Another thing, I've noticed that the new register allocator in 3.0
> > uses less stack memory than IAR or GCC so that is something positive.
> > I see a lot of potential in getting better code than gcc in the
> > future, because with the current generated code which is not optimized
> > at all (i want to leave that for a later stage) we're getting in par
> > or improving what gcc does and sometimes getting a bit longer code but
> > nothing that is too bad to worry. But once we introduce custom patters
> > for instruction selection things will improve exponentially.
> >
> > If you want to ask any specific questions after this general summary?
> >
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