The Lede
Developers working with the Zig language have a new ally in their quest for speed: the compiler's incremental compilation feature. By recompiling only changed parts of a project, Zig's incremental compilation significantly reduces rebuild times, making it a game-changer for software engineers. This feature is the result of a long-term effort by the Zig core team to improve the compiler's performance.
Background & Context
The Zig language has been gaining popularity in recent years due to its performance, reliability, and ease of use. However, one of the major pain points for developers has been the time it takes to rebuild projects. To address this issue, the Zig core team has been working on improving the compiler's performance. The result is the incremental compilation feature, which recompiles only changed parts of a project, reducing rebuild times significantly.
Deep Dive
Zig's incremental compilation feature works by leveraging cached ZIR (Zig Intermediate Representation) and dependency graphs. The ZIR cache stores the content-addressed ZIR on disk, while the Decl dependency graph keeps track of what each analyzed declaration depends on. The Sema pass re-runs only invalidated declarations, reusing the InternPool for stable identities. The Codegen pass re-emits per-decl artifacts, which are then stitched together by the linker. The linker also supports per-decl Atom updates, making it possible to directly patch the resulting bytes into the output binary.
Expert Angle
According to a member of the Zig core team, 'the results of `AstGen` are cached globally, making it possible to reuse the results of previously compiled files.' This is a significant improvement over traditional compilation methods, where the entire project is recompiled every time. 'The impact of this feature will be significant for developers, enabling faster iteration and reduced development time,' says the team member. 'This is a major step forward for the Zig language, and we're excited to see how it will be used in the future.'
What Comes Next
The incremental compilation feature is currently available in the Zig compiler and can be enabled with `zig build --watch -fincremental`. In the future, the feature will be extended to support more use cases, such as exposing detailed semantic information to ZLS or similar projects. The impact of this feature will be significant for developers, enabling faster iteration and reduced development time. As the Zig language continues to gain popularity, it's likely that we'll see more innovative features like this in the future.