[llvm-dev] [RFC] AAP Backend

[Ed Jones via llvm-dev]

I have now submitted the first 3 patches to add the AAP backend. These
add the target triple, ELF defines and the skeleton of a backend

https://reviews.llvm.org/D23664
https://reviews.llvm.org/D23665
https://reviews.llvm.org/D23667

Thank you,
Ed Jones

On 18/08/16 13:31, Ed Jones wrote:
> Hi Renato,
> 
> Currently I am building a set of patches which will add AAP piece-wise.
> I'm following the approach that AVR (and now RISC-V), and the patches I
> plan on adding are as follows:
> 
> * Target triple
> * ELF definition
> * Basic skeleton with the required build system changes (targetinfo +
> target machine)
> * Instruction + Register tablegen
> * MC layer support
> * AsmParser
> * InstPrinter
> * Disassembler
> * Bulk of the implementation for lowering, isel and similar
> 
> At the moment there are only two changes to generic code, one is to
> override the size of pointers when printing assembly (for AAP we use
> larger pointer as the upper bits are used for flags), the other is to
> track live outs of a function (We have some registers which are callee
> saved, but also used for return values). I'm going to extract these
> changes into separate patches and submit them along with the above.
> 
> We're not planning on submitting the simulator yet, we have been keeping
> it outside of our main Target directory so that we don't write anything
> that unintentionally relies on the simulator or lets parts of it leak
> into any patches we submit. We may submit it separately at a later
> point, as part of the AAP target directory.
> 
> I imagine either I or my colleague Simon Cook would be the code owner
> (or both if that's possible). The community is Embecosm, and those who
> may wish to use AAP as a basis for their work.
> 
> I will have a few basic patches submitted by the end of the day.
> 
> Thank you,
> Ed Jones
> 
> 
> On 18/08/16 12:22, Renato Golin wrote:
>> On 18 August 2016 at 08:34, Ed Jones via llvm-dev
>> <llvm-dev at lists.llvm.org> wrote:
>>> We believe the code base is sufficiently mature that it is appropriate
>>> for inclusion. Currently, the full source for AAP can be found on Github:
>>> https://github.com/embecosm
>>
>> Hi Ed,
>>
>> I had a look at the GitHub project and it wasn't clear what is needed
>> to move the AAP target in-tree.
>>
>> First, it seems you're merging our tree into yours, which means the
>> merge commit [1,2] show the differences between old and new LLVM
>> stuff, not yours vs. upstream. This makes it hard to predict the
>> affected changes.
>>
>> Also, you seem to have a standard-looking lib/Target/AAP [3], which is
>> a good step forward, but you also have added the simulator [4] in
>> there, which is not the right place. This should probably be a
>> different project altogether.
>>
>> So, from our recent check-list for new targets, I'm assuming a few things:
>>
>> Code owner: You?
>> Community: Embecosm + its users
>> License: AFAICS, check.
>> Docs / Impl: check
>>
>> The thing that isn't clear right now is "compatible code and policies".
>>
>> I don't see why we shouldn't take the AAP target, unless it poses a
>> big enough change to IR, the middle end, etc. So, I recommend two
>> steps:
>>
>> 1. A quick summary of the target independent changes you had to do to
>> make your back-end work. Changes to IR semantics, additional Clang
>> checks, base classes overwritten, etc.
>>
>> 2. Propose some patches on Phabricator, showing those differences.
>> These patches don't need to be the whole thing, for now, but basic
>> support ("hello world" style) should be working and tested.
>>
>> We can continue from there.
>>
>> cheers,
>> --renato
>>
>>
>> [1] https://github.com/embecosm/aap-llvm/commit/1d767ab10d0de413c341fe69ca228b97e7e1d255
>> [2] https://github.com/embecosm/aap-clang/commit/d1c2e5081a6222f2b4ab8d175fbd68a5e803c6d9
>> [3] https://github.com/embecosm/aap-llvm/tree/aap-master/lib/Target/AAP
>> [4] https://github.com/embecosm/aap-llvm/tree/aap-master/lib/Target/AAPSimulator
>>