Performance annotations

[tbkka (Tim Kientzle)]

@Jon_Shier

As an aside, can we please get an overall performance manifesto that outlines the current issues, why these are suddenly a priority, and the areas that will be focused on, rather than just separate proposals for each possible solution? The community is missing a huge amount of context here.

Joe has put together a road map that pulls together a number of related ideas and how they fit together:

A roadmap for improving Swift performance predictability: ARC improvements and ownership control

Swift's high-level semantics try to relieve programmers from thinking about memory management in typical application code. In situations where predictable performance and runtime behavior are needed, though, the variability of ARC and Swift's optimizer have proven difficult for performance-oriented programmers to work with. The Swift Performance team at Apple are working on a series of language changes and features that will make the ARC model easier to understand, while also expanding the bread…