[llvm-dev] Parallel IR [PIR] --- BoF preparation discussion

[Renato Golin via llvm-dev]

On 14 October 2016 at 10:38, Johannes Doerfert via llvm-dev
<llvm-dev at lists.llvm.org> wrote:
> To structure the mailing list discussion we propose to:
>   - Inform a broader audience on the (currently) proposed approaches
>     targeted specifically at LLVM (including but not necessarily limited
>     to the work by Intel, Dounia Khaldi et al, Tao Schardl et al and our
>     own work)
>   - Collect/summarize arguments for and against a "more intrusive"
>     parallel representation in LLVM.
>   - Collect/summarize requirements including abstract design goals but
>     also concrete examples that should (not) be supported.
>
> => We will use the summaries to prepare a short presentation for the BoF
>    (~10min) which allows us to use the majority of time for a qualified
>    discussion on the topic.

Hi Johannes,

I think this is a great idea! With a deadline to meet (~2 weeks), and
a particular focus (feed the BoF discussion), I think we can keep
ourselves on track.

I particularly welcome a more intrusive change to IR (away from
metadata) to hold parallelism ideas, since we're past the point where
SIMD / multi-core was considered only an optimisation, and the
compiler IR has to evolve to match.

But I'm also worried that we'll end up lost in the multitude of ways
we can extend the IR. A step by step pragmatic approach is fundamental
to keep it sane and robust, and I think your starting point conveys
that well.

We need to make sure we cover simpler cases first, without losing
sight of the more complicated cases as an evolution of whatever plan
we come up with. But also, we need to be backward compatible, so that
the optimisation passes don't start depending solely on the new IR
constructs to work.

cheers,
--renato