[llvm-dev] Your help needed: List of LLVM Open Projects 2017

Thu Jan 19 22:21:57 PST 2017

On Wed, Jan 18, 2017 at 9:34 PM, Sean Silva <chisophugis at gmail.com> wrote:

>
>
> On Mon, Jan 16, 2017 at 11:02 PM, Rui Ueyama <ruiu at google.com> wrote:
>
>> On Mon, Jan 16, 2017 at 12:31 PM, Sean Silva <chisophugis at gmail.com>
>> wrote:
>>
>>> Do we have any open projects on LLD?
>>>
>>> I know we usually try to avoid any big "projects" and mainly add/fix
>>> things in response to user needs, but just wondering if somebody has any
>>> ideas.
>>>
>>> Some really generic/simple stuff I can think of:
>>> 1. trying out LLD on a large program corpus and
>>> reporting/reducing/fixing bugs (e.g. contributing to the FreeBSD effort or
>>> trying to build a bunch of packages from a linux distro like Debian or
>>> Gentoo)
>>>
>>
>> I like that idea. FreeBSD is using a very old version of ld.bfd, so on
>> Linux systems we may be able to find programs that use recent linker
>> features which LLD does not support. This may sound like an ambitious goal,
>> but I want make Linux distributions to use LLD as default linker, so it
>> needs to be able to link entire Linux distributions.
>>
>
> That's indeed ambitious, as even Gold has not managed to become the
> default on any prominent Linux distro I'm aware of. IIRC gold doesn't link
> all of Gentoo (there was a blog post / article but I can't find it). One
> intermediate goal we can strive for is to reach parity with Clang, which
> currently builds about 95% of the packages: http://clang.debian.net/
>

It is ambitious, but I think we have one advantage over gold, which is that
LLD is a part of the LLVM project. When LLD is mature enough, we should
probably start thinking of making Clang prefer LLD over other system
default linkers if LLD is installed to a system (we had this discussion
before.) In that sense we may be able to piggy-back on Clang to make it
default. Of course there is a risk in doing that, so LLD needs to become a
tool that "just work" before doing that, though.

>
>>
>> 2. performance analysis and optimization of LLD
>>> 3. getting LLD to link a bootable Linux kernel and/or GRUB
>>>
>>
>> I don't know how hard/easy it is to link Linux kernel with LLD, but that
>> should be doable if we spend enough effort on that. That should be a good
>> project.
>>
>> As to porting LLD to other architectures, you can use emulators like
>> bochs, can't you? You don't even need any emulator for x86 32-bit.
>>
>
> These open projects are largely targeted at new contributors, so ideally
> we would provide some instructions on how to set up a test system, what to
> do on it, etc. The less effort they have to spend yak-shaving setting
> things up, the sooner they will be doing useful work on LLD (or even,
> contributing to LLD at all, if they can't figure out how to set things up).
> We already have community members with workflows for doing this kind of
> testing, it's just a matter of writing it down so it is easy to follow.
> Ideally it's just "download this emulator and grab this image for
> <architecture>, then boot it and try building/linking/running some
> programs"; also, any relevant cross-compile setup would make things easier
> too.
>
> Similarly for the Linux kernel; all the setup for getting qemu and stuff
> working is annoying and I remember it took Davide, Michael, and quite a bit
> of time yak-shaving to find a nice workflow that we could iterate on for
> FreeBSD. Honestly the Linux/GRUB project is a bit of a stretch: I think
> this "open projects" page is mainly aimed at a student/intern-level
> audience, and to attack that project a student/intern-level contributor
> would have to be truly extraordinary (though I guess we may want to attract
> those types too ;-) ). Filling in architecture support in userland is a
> much more tractable for a larger audience.
>
> -- Sean Silva
>
>
>>
>> 4. write an input verifier such that LLD can survive intensive fuzzing
>>> with no crashes / fatal errors [1] when the verifier says the input is
>>> okay. This will allow us to measure what the overhead of doing this
>>> actually is.
>>>
>>>
>>> [1] As of the latest LLD discussion (in the thread "[llvm-dev] LLD
>>> status update and performance chart") it sounds like people are okay with
>>> LLD treating fatal errors the same way that LLVM uses assertions; for
>>> inputs from the C++ API, we can document to not pass corrupted object
>>> files. For inputs read from files, there is still community interest in at
>>> least having the option to run a "verifier" to validate the inputs. I think
>>> the best way to approach the verifier is to essentially follow the approach
>>> suggested by Peter (in the context of "hardening") in
>>> https://llvm.org/bugs/show_bug.cgi?id=30540#c5 i.e. getting to the
>>> point where LLD can survive intensive fuzzing.
>>>
>>> -- Sean Silva
>>>
>>> On Mon, Jan 16, 2017 at 5:18 AM, Vassil Vassilev via llvm-dev <
>>> llvm-dev at lists.llvm.org> wrote:
>>>
>>>> Hi folks,
>>>>
>>>>   Happy new year!
>>>>
>>>>   Last LLVM Developers' Meeting I had a BoF: 'Raising Next Generation
>>>> LLVM Developers'. It was suggested that we should update our open projects
>>>> page and possibly restructure it a little bit.
>>>>
>>>>   I volunteered to do this work and I need your help.
>>>>
>>>>
>>>>   Chandler and I started working on a google doc [1]. We pinged few
>>>> code owners asking them to list of work items we should get done in 2017
>>>> but we do not have the manpower. Now we would like to ask for your input,
>>>> too.
>>>>
>>>>   I believe an up to date list can serve as a good entry point for
>>>> students, interns and new contributors.
>>>>
>>>>   Feel free to propose a new item or comment under an existing one. I
>>>> expect to start gradually updating the page beginning of Feb.
>>>>
>>>> -- Vassil
>>>>
>>>> [1] https://docs.google.com/document/d/1YLK_xINSg1Ei0w8w39uAMR1n
>>>> 0dlf6wrzfypiX0YDQBc/edit?usp=sharing
>>>> _______________________________________________
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>>>>
>>>
>>>
>>
>
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