LLVM Developer Meeting 2016


I had the pleasure of attending the LLVM Developer Meeting this year in Barcelona. Too much happened to describe it all, so I’ll just give you the highlights.

There were many great talks on a range of topics, including tools that were ready for primetime, practical techniques and blue sky research. Some of my favourites were:

There was an Intel talk on optimising for code size on x86. This was a classic juicy details talk, showing how different instruction encodings could save precious bytes. Every technique was clearly described along with measurements of space savings.

Tobias Grosser (the lead developer of Polly) and Johannes Doerfert gave a fantastic tutorial on Polly. ‘Polyhedral loop modelling’ is an intimidating term when you first encounter it, but their explanation was clear and effective. They also showed how to derive simple loop optimisations like loop interchange in this system and the more sophisticated optimisations they’ve developed on top.

Linkers are a greatly overlooked part of the compiler toolchain, so I enjoyed Rui Ueyama’s talk on LLD. This was very topical, as LLD has had a ton of work of late and ELF support was recently rewritten. Rui also did a deep-dive on linking algorithms and their semantics/performance tradeoffs.

Kristof Beryls discussed the challenges of accurate performance measurements. When writing compiler optimisations, obtaining reliable performance metrics is crucial. Kristof demonstrated how benchmark numbers can be outrageously misleading, and gave suggestions of how to fix them.

If you missed any of the talks, they were recorded. They should be uploaded to the LLVM YouTube account (uploads are announced on the llvm-devmeeting mailing list).

In addition to the talks, there were plenty of opportunities to mingle with people from different parts of the LLVM ecosystem. I met academics, compiler engineers from companies large and small, and even had dinner with the PS4 compiler team!

It was well worth attending, and I’d recommend it to anyone who is interested in compiler development. I hope to see you there next year!

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