[llvm-dev] [RFC] AAP Backend

Mehdi Amini via llvm-dev llvm-dev at lists.llvm.org
Fri Aug 26 08:36:32 PDT 2016

Hi Ed,

> On Aug 25, 2016, at 1:10 AM, Ed Jones via llvm-dev <llvm-dev at lists.llvm.org> wrote:
> As it stands, the active customers for this target are the out-of-tree
> backends which we are working on which can't be submitted for inclusion
> into LLVM.

I don’t feel you really answered Alex's question which was “can you *quantify* the *active* customers for this target?”.
I understand that there are out-of-tree backends, but the question is about who will use/develop/maintain this backend upstream in LLVM?  And is there already an open-source community around this backend somewhere?

I think Alex’s point is that there needs to be a sufficient user base or a sufficient commitment of maintenance to warrant the burden of the backend on the community.


> The general aim of the backend though is to include features from
> architectures which are not well represented in LLVM, for example
> non-power of two register sizes, non-octet chars, or very constrained
> register sets, and to this end we hope for it to be useful to the
> community at large if they are maintaining out-of-tree targets with
> features they would like LLVM to support.
> Thanks,
> Ed
> On 23/08/16 21:28, Alex Rosenberg wrote:
>> I don't think we've ever really built up clear guidance on this, but I think there needs to be a clear determination that a given target has enough active users to make the maintenance burden worth putting into the mainline. In the past, the only exception I can think of is the Lanai backend, but in that case we have a strong commitment of multiple employees at a major corporation committed to that target's maintenance.
>> So, concretely, can you quantify the active customers for this target?
>> Alex
>> On Aug 18, 2016, at 12:34 AM, Ed Jones via llvm-dev <llvm-dev at lists.llvm.org> wrote:
>>> Hi all,
>>> We wish to submit our latest AAP implementation as an experimental
>>> backend into LLVM. We need community feedback and reviewers for patches
>>> which we will submit soon.
>>> AAP was designed in early 2015 and aims to advance compiler development
>>> for small deeply embedded Harvard architectures, which are widely used
>>> commercially. AAP is freely available as an open source softcore for use
>>> in FPGA designs.
>>> AAP has wide exposure: at ORCONF16 at CERN, at FOSDEM and at BCS and
>>> OSHUG meetings. It is also of commercial interest, because of the
>>> potential benefits of providing upstream LLVM support for features found
>>> in small embedded processors.
>>> Currently there is a complete Clang and LLVM toolchain including gdb, ld
>>> and binutils, as well as two simulator implementations. The toolchain is
>>> passing all LLVM regression tests and a decent proportion of GCC
>>> regression tests. We are also working on a GCC port to allow comparison
>>> between compilers, which should be beneficial to both projects.
>>> 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
>>> Details about the ISA, and the hardware implementation can be found on
>>> our website:
>>> http://www.embecosm.com/resources/appnotes/#EAN13
>>> http://www.embecosm.com/resources/appnotes/#EAN14
>>> We are also planning to talk about AAP at the LLVM Cauldron in Hebden
>>> Bridge. We look forward to discussing our work on AAP with those who are
>>> attending.
>>> Thank you,
>>> Ed Jones
>>> _______________________________________________
>>> LLVM Developers mailing list
>>> llvm-dev at lists.llvm.org
>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
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