How to improve compile time?

To improve compile time, you can leverage the concept of explicitly built modules introduced in Xcode 16. Here are some key points and steps to consider:

1. Enable Explicitly Built Modules:

   • Explicitly built modules allow the build system to control module builds, making the process more efficient and parallelized.
   • For C and Objective-C, this feature is enabled by default. For Swift, you need to opt-in by adjusting your build settings in Xcode.

2. Build Process Optimization:

   • Xcode splits the compilation of each source file into three phases: scanning, building modules, and building the original code. This separation allows for better parallelism and more efficient use of execution lanes.
   • The build system can now avoid running tasks that are not ready, waiting until the necessary modules are built, which reduces idle time and improves overall build speed.

3. Detailed Build Logs:

   • With explicitly built modules, the build logs now show separate tasks for scanning dependencies and compiling modules. This detailed breakdown helps in identifying and optimizing the time spent on each task.

4. Uniform Build Settings:

   • Reducing the number of module variants by making your build settings uniform across your project can help in sharing modules built for a given source file across different targets, further improving build efficiency.

5. Improved Diagnostics and Debugging:

   • Explicitly built modules provide better diagnostics and faster debugging since LLDB can reuse build outputs when evaluating expressions. This also includes smaller DSIM bundles and faster symbol lookups with the default use of DWARF 5 debug symbols.

For more detailed information, you can refer to the session Demystify explicitly built modules (06:50).

Relevant Sessions

• Demystify explicitly built modules
• What’s new in Xcode 16
• What’s new in Swift