Helium3 Helium3 - 1 year ago 50
Swift Question

Output compile durations for swift files

Is there a way to turn output the time taken to compile a swift file during an xcode build?

I would like to compile from the command line to trigger the same build xcode does but to include the time taken to compile each file.


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show full build reports per file but there is no timeframe associated with them.

Its not clear on compile times by looking and the loading state etc. as its more guestimate style.

I would like to cut down the compile time of a Swift 1.2 project, as it takes around 5 - 10 minutes after a clean or 3 -5 minutes after changing source in a heavily dependent file.

Answer Source

You can add…

-Xfrontend -debug-time-function-bodies

…to Other Swift Flags in Swift Compiler - Custom Flags section (build settings).

Build settings

Note: You have to keep same order of these flags. -Xfrontend says that the next flag should be passed to the frontend. It will not work if you reverse the order.

Then you can get compile times in your build log:

Build log

Which is useful when you do want to optimize compile time and also it's good to attach this kind of build log when reporting an issue to Apple Swift guys about slow compile time.

Credit goes to Joe Pamer Errant compiler hacker. Currently an engineering manager at Apple (Swift, Clang), formerly at Microsoft (TypeScript, F#, JavaScript, .NET). He tweeted it as a response to Rob Rix question about profiling Swift compilation. It made me curious, so, I disassembled compiler, checked text section for more flags and found other hidden options. Don't use them in production code, just play with them.

Build time of the whole project. Run following command in terminal…

defaults write com.apple.dt.Xcode ShowBuildOperationDuration YES

…restart Xcode, clean & build and…

Build time