Speed up Xcode Swift build times

Question

As my project has grown over the past year, so have its build times. Over the last few months it's gone from 4 minutes to around 7 (time includes GitHub pull, unit tests, etc).

I have investigated with -Xfrontend -debug-time-function-bodies to find lines that are slow to compile, and changed that code.

I believe it's now a question of project size; 182 Swift files, ≈31K lines. 23 storyboards, 52 XIBs. This is a regular UIKit app with a handful of Cocoapods dependencies.

The bulk of the build time is spent in the "Compiling Swift source files" phase.

The build machine time I care less about than the edit-build-debug cycle, which has also been slowing.

What can be done to improve build times?

Answer 1

Here's an article about benchmarking/speeding up compilation time - swift-profiling.

In case it goes dead here is the tldr:

xcodebuild -workspace App.xcworkspace -scheme App clean build OTHER_SWIFT_FLAGS="-Xfrontend -debug-time-function-bodies" | grep .[0-9]ms | grep -v ^0.[0-9]ms | sort -nr > culprits.txt

You can just run that or add the following flags to your build under the other-swift-flags in build settings:

-Xfrontend -warn-long-function-bodies=100

This will show you which lines are slowing down your compile time.