Re: [avr-llvm-devel] New backend implementation

[John M. <ato...@gm...>]

Hi,

There are only three devs right now. I'm not sure what the status is of the
others or how much time they have for the project.
I'm still interested in working on an avr lllvm port. Main line changes
broke our port not long after the 2.7 release. I got frustrated trying to
hunt down the problem and basically have been taking a break.

On Fri, Sep 24, 2010 at 10:01 AM, Borja Ferrer <bor...@gm...>wrote:

> Hello John,
> I havent created yet a SF account, but i could create one right now. I'm
> currently developing for version 2.7, v2.8 is going to be released in a few
> days so i will need to update my code for then because there has been some
> changes in the interfaces. What i thought is to wait for the release, update
> my code to make it compatible and then merge it into here.
> Yes there are places that are a bit farther ahead, but others not. For
> example, i've seen you've already added some code thinking on memory
> addresses for IO and that stuff but i havent touched that at all yet.
>
> As a side note, if it's possible to know, how many devs are involved in the
> project and what is the time availability of them. Im asking this because i
> noticed last commit was from march and you're the only one that is really
> commiting code, so i want to know what is the status of the project and if
> there are any plans.
>
> Thanks.
>
> 2010/9/24 John Myers <ato...@gm...>
>
> Hi,
>>
>> I also think merging the projects would be good. Do you have a SourceForge
>> account? I can add you as a developer.
>> Are you developing off the trunk or a release? Our code is stale now,
>> since we haven't been keeping up with the trunk.
>> It sounds like your code is farther ahead in producing code.
>>
>> --John
>>
>>
>> On Fri, Sep 24, 2010 at 6:06 AM, Borja Ferrer <bor...@gm...>wrote:
>>
>>> Hello everybody, I've been working lately in the AVR backend for LLVM by
>>> myself until i've found this project. I'm not completely happy with the code
>>> GCC produces so i decided to take on with this challenge. I think it would
>>> be a good idea to join our efforts in this project, instead of duplicating
>>> the work if we do it by separate.
>>>
>>> My current code has the following status:
>>>
>>> - It can build and emit AVR asm code for very basic C code.
>>> - Produce code for all arithmetic and binary operators and for different
>>> sizes wider than char (except division for larger types which will end being
>>> a lib call).
>>> - Basic support for shifts, currently only by a constant number. (We
>>> needed here customized shifts because AVR only supports shifts by 1).
>>> - Support for the multiplication instruction.
>>> - Support for input function arguments and return values of any size.
>>> - Code pass to fold two move instructions into a movw. (I dont like this
>>> as a final solution since i prefer patching the DAG before codegen but it
>>> works atm).
>>> - Very basic support for function calls (I'm currently working into
>>> this).
>>>
>>> My code looks very similar to the one in this project with some
>>> exceptions, for example the instruction formats and instruction description.
>>> I've taken a different approach on encoding instructions trying to pack
>>> instructions by format like Reg,Reg or Reg, K, etc so we end up encoding
>>> them in a compact form.
>>>
>>> I've been running some tests and the code produced looks very promising,
>>> LLVM produces more compact code than gcc without having written any single
>>> optimization yet in my code. Of course there are cases that need tuning, but
>>> I think optimizations should be left for a later stage in development until
>>> things work decently. Although i couldnt resist on this last point, i've
>>> reported some missed optimizations in the LLVM dev list, and filled them as
>>> a bug report. One great thing about LLVM is that you get pretty fast support
>>> and things get fixed much faster than for GCC where a bug report can be open
>>> for 8 years.
>>>
>>> Well let me know what you think and if we can merge our code.
>>>
>>> Thanks
>>>
>>>
>>>
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>>
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