[llvm-dev] [RFC] AAP Backend

Ed Jones via llvm-dev llvm-dev at lists.llvm.org
Thu Aug 25 01:10:14 PDT 2016

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.

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.


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
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