Davide Italiano

[Cyndy Ishida @CyndyIshida]

Interested in how libraries impact an app’s size & performance? And what you can do to improve it? Meet mergeable libraries in this #WWDC23 session!
https://t.co/CuPCD4ob5J

[Davide Italiano @davidecci]

@ElliottZ @rui314 The new linker has different optimization levels compared to ld64. `-O0` for debug, and `-O` for release. `clang` and swift will pass the correct values down to the linker starting Xcode 15 beta 1. Other build systems/compilers will need to pass `-O0` in debug correctly.

[Patrick Balestra @BalestraPatrick]

I'm seeing similar results in our biggest project. Linking time for a typical incremental build goes from over 10s to 3s in Xcode 15 with ld-prime!

[Keith Smiley @SmileyKeith]

The new linker in Xcode 15 lives up to the hype! ~6s -> ~1.5s for our largest target.

[Ian Small @iansmall]

@davidecci When Venkatadri Seshadri and I presented on concurrent compilation in 1987 at IFIP/Distributed Processing, there was very little published. We focussed on low-hanging fruit at the front-end of the pipeline. Wonderful to see concurrency make it all the way through to the linker.

[✨ Jean Yang ✨ @jeanqasaur]

Who knew, static linking still hot 💪

[Davide Italiano @davidecci]

For folks interested in using mergeable libraries, the following documentation should help to get you started: https://t.co/EAwyrE4fcy

Join the labs to provide feedback and ask questions!

[Davide Italiano @davidecci]

If you're interested in hearing more, join the lab and watch @CyndyIshida's session, available on Wednesday.

https://t.co/aFQ50QqeKX

[Nataliya Marmelstein🇧🇬 @nataliya_bg]

Modularity of iOS codebases is still non-trivial at scale. We need more updates like this one. Sounds promising! 🤩 #WWDC23

[@[email protected] @lgerbarg]

Hope everyone enjoyed the SOTU presentation! We have an brand new linker this year, and some really cool new features like mergeable libraries. There is a session on Wednesday, and team members will be in labs throughout the week. https://t.co/S8adswHgXN #WWDC23

[Davide Italiano @davidecci]

What's even more thrilling is observing that, despite linkers and loaders having a long history, there is still ample potential for advancing the state of the art in this field.

[Davide Italiano @davidecci]

I consider myself fortunate enough to have had the opportunity to support these two projects, both of which were successfully developed by an exceptional small team of individuals.

[Davide Italiano @davidecci]

My team also worked on a new library format: mergeable libraries. Mergeable libraries combine the benefits of static and dynamic libraries, providing the best performance without sacrificing development velocity. (1/n)

[Davide Italiano @davidecci]

In development, mergeable libraries act like “regular” dylibs, for maximum development productivity. In release, the linker can use the extra metadata to merge multiple libraries together and perform the kind of optimizations that would happen in a static library build.

[Davide Italiano @davidecci]

My team also worked on a new library format: mergeable libraries. Mergeable libraries combine the benefits of static and dynamic libraries, providing the best performance without sacrificing development velocity. (1/n)

[Davide Italiano @davidecci]

Today at WWDC we introduced a new static linker. It is a ground-up rewrite that’s up to 5x faster than ld64. The new linker is written with multicore in mind, and it’s the first production ready parallel linker officially supported for iOS development. (1/n)

[Davide Italiano @davidecci]

Mergeable libraries are dynamic libraries plus metadata that allow the static linker to perform a relinking step. At the core lies the concept that the metadata hold sufficient information to reconstruct the original object files.