"Ускорение сборки большого проекта на Objective-C + Swift" Иван Бондарь (Avito)

Speed up build time of
big project on
Objective-C + Swift
Ivan Bondar
Lead iOS developer in Avito

Build time: 194.803s
75% of build time - Compile Swift files phase
Swift:
- *.swift files: 626
- LOC: 27264
Project structure
Objective-C:
- *.m files: 729
- LOC: 45947
- 217 imports in bridging-header

What to do
• Tune build settings
• Reduce .swift ﬁles count
• Reduce extensions count
• Optimize slow compiling functions
• Fix warnings
• Apply ccache compiler cache utility

Tune build settings
Build Active Architecture Only
Enable Objective-C Modules
Debug data format - DWARF (no dsym ﬁle)
Enable Whole module optimization

Tune build settings
Debug data format - DWARF (no dsym ﬁle)
Build time: 191.623s (194.803s before)

Tune build settings
Whole module optimization
Main target build time: 76.614 s
Not suitable for debugging
Can’t compile unit test target - segfault or weird errors with
Swift-ObjC bridging

Reduce .swift files count
Pre-build action - merge all Swift code to one FAT
Swift file
Not suitable for big projects:
- can’t compile with segmentation fault 11
- eliminates «private» modifier
- can’t use breakpoints in the original source

Reduce .swift files count
Merge different classes/protocols in big .swift files
Not suitable for VIPER in general
Decided to apply only in certain cases, e.g.
put Input and Output protocol declarations in one file

Reduce extensions count
0
10
20
30
40
100 1000 2000 3000 5000 10000
methods extensions
* by Dmitry Bespalov
https://tech.zalando.com/blog/speeding-up-xcode-builds/

Reduce extensions count
class FilterViewController: UIViewController {
}
// MARK: UITableViewDelegate
extension FilterViewController: UITableViewDelegate {
}
// MARK: UITableViewDataSource
extension FilterViewController: UITableViewDataSource {
}
class FilterViewController: UIViewController,
UITableViewDelegate,
UITableViewDataSource {
// MARK: UITableViewDelegate
// MARK: UITableViewDataSource
}
Changes in code style applied
Before: After:
Extensions count reduced by 400

Optimize slow compiling functions
Proﬁle compile time per function, ﬁlter by time > 1 ms.
xcodebuild ARCHS=arm64 ONLY_ACTIVE_ARCH=NO -workspace App.xcworkspace -scheme App
clean build OTHER_SWIFT_FLAGS="-Xfrontend -debug-time-function-bodies" | grep [1-9].
[0-9]ms | sort -nr > culprits.txt

What to fix:
• Functions with longest compile time
• Functions with big number of occurrences
2871.3ms /Users/iyubondar/Projects/avito-ios/Models/Domain/Advertisement/Advertisement/Base/AdvertisementImage.swift:2:5 init(url100x75:
String?, url140x105: String?, url240x180: String?, url432x324: String?, url640x480: String?, url1280x960: String?)
932.7ms /Users/iyubondar/Projects/avito-ios/Core/Extensions/UIKitExtensions/UICollectionView/UICollectionView+ChangeAnimations.swift:57:17
final class func changeSet<T : Hashable>(oldArray oldArray: [T], newArray: [T]) -> CollectionViewChangeSet
253.0ms /Users/iyubondar/Projects/avito-ios/Core/Extensions/UIKitExtensions/UICollectionView/UICollectionView+ChangeAnimations.swift:90:17
final class func changeSet<T>(oldArray oldArray: [T], newArray: [T], identityHashFunction: (T) -> Int, identityCheckFunction: (T, T) -> Bool,
equalityCheckFunction: (T, T) -> Bool = default) -> CollectionViewChangeSet
136.0ms /Users/iyubondar/Projects/avito-ios/Presentation/Views/Advertisement/AdvertisementView/AdvertisementPresenter.swift:9:26 @objc
public override func setModel(model: AnyObject!)
91.4ms/Users/iyubondar/Projects/avito-ios/Presentation/Views/Controls/PullToRefresh/ScrollViewRefresher.swift:251:18 private func
handleRefreshingProgressChanged(progress: RefreshingProgress)
84.0ms/Users/iyubondar/Projects/avito-ios/VIPER/SelectCategoryParameters/Validation/SelectFromToValidator.swift:52:25 private final class func
findValidRowIndex(valuesToSelect: [SelectCategoryParameterViewModel.Data], inCompareToValues compareValues:
[SelectCategoryParameterViewModel.Data]?, selectedRowIndex: Int, iterationOrder: IterationOrder) -> Int
82.5ms/Users/iyubondar/Projects/avito-ios/Presentation/Views/Profile/ProfileViewPresenter.swift:30:10 @objc func notificationsSubtitle() -> String
81.8ms<invalid loc> init?(rawValue: String)
currentDate: NSDate, calendar: NSCalendar, todayDateFormatter: NSDateFormatter, yesterdayDateFormatter: NSDateFormatter, weekdayDateFormatter:
NSDateFormatter, dayDateFormatter: NSDateFormatter, yearDayDateFormatter: NSDateFormatter, fullDateFormatter: NSDateFormatter) -> String
8659 occurrences found.

Use lazy only when it's necessary
1204 occurrences found
Compile time: 1.0 … 11.8 ms
private lazy var footerLabel: UILabel = {
let footerLabel = UILabel()
footerLabel.textColor = SpecColors.mainText
footerLabel.font = SpecFonts.regular(14)
footerLabel.autoresizingMask = .FlexibleWidth
footerLabel.lineBreakMode = .ByWordWrapping
footerLabel.numberOfLines = 0
footerLabel.textAlignment = .Center
footerLabel.shadowColor = UIColor.whiteColor()
footerLabel.shadowOffset = CGSize(width: 0, height: -1)
return footerLabel
}()

Avoid long expressions
Compile time: 2871.3ms
self.thumbnailUrl = url240x180 ?? url140x105 ?? url100x75 ?? nil
self.fullImageUrl = url640x480 ?? url432x324 ?? url1280x960 ?? url240x180 ??
url140x105 ?? url100x75 ?? nil
self.thumbnailUrl = url240x180 ?? url140x105 ?? url100x75
self.fullImageUrl = url640x480 ?? url432x324 ?? url1280x960 ?? url240x180 ??
url140x105 ?? url100x75
Compile time: 916 ms

Avoid long expressions
var fullImageUrl: String? {
if let url640x480 = url640x480 {
return url640x480
}
return url432x324
}
…
return url100x75
}
return nil
}
Compile time: <1 ms

Use map() and ﬂatMap() with care
1177 occurrences found
Compile time: 2.5 … 21.8 ms
private lazy var tabControllers: [UIViewController] = {
var controllers = [UIViewController?](count: Tab.tabsCount, repeatedValue: nil)
controllers[Tab.Search.rawValue] = self.categoriesNavigationController()
controllers[Tab.Favorites.rawValue] = self.favoritesNavigationController()
controllers[Tab.Publish.rawValue] = self.publishNavigationController()
controllers[Tab.Messenger.rawValue] = self.channelsRootViewController()
controllers[Tab.Profile.rawValue] = self.profileNavigationController()
return controllers.flatMap { $0 }
}()

Use map() and ﬂatMap() with care
Original example: http://irace.me/swift-proﬁling
return [CustomType()] + array.map(CustomType.init) + [CustomType()]
Compile time: 3158.2 ms and many occurrences

Give «type hints» to the compiler when necessary
* example by IMPATHIC
http://blog.impathic.com/post/99647568844/debugging-slow-swift-compile-times
func hangCompiler() { ["A": [ ["B": [ 1, 2, 3, 4, 5 ]], ["C": [ ]], ["D": [ ["A":
[ 1 ]] ]] ]] }
Build time: 54.249 s
func hangCompiler() { ["A": [ ["B": [ 1, 2, 3, 4, 5 ]] as [String: [Int]], ["C": [ ]]
as [String: [Int]], ["D": [ ["A": [ 1 ]] as [String: [Int]] ]] ]] }
Build time: 1.293 s

No great effect in our case
Before:
• 8659 functions > 1ms
• max time 2871.3мс
• median time 1.8ms
After:
• 2227 functions > 1ms
• max time 124.3мс
• median time 3.4ms

Fix warnings
Swift Compiler Warnings: 64 total
Warning type Count
Build time
after fix
Parameters of ... have different optionality 3 92.5s
User-defined 2 92.5s
Cannot find protocol definition 3 90.481s
Overriding instance method parameter with implicitly unwraped optional
type 27 warnings
27 90.195s
Deprecation 18 93.487s
<Some code> will never been executed 1 93.654s
Immutable value ... was never used 1 93.152s
Pointer is missing nullability specifier 9 80.667s

Fix warnings
But, with 1 warning <Some code> will never been executed, build
time is 84.919s
Fix all Swift Compiler Warnings to speed up build time!

Apply ccache compiler cache utility
ccache limitations:
- no support for Clang modules
- no support for precompiled headers
- no Swift support
ccache applied to project

What was done
Before: 194.803 s After: 68.403 s
There is no silver bullet :(
• Tune build settings - 3s
• Reduce .swift ﬁles count - 0s
• Reduce extensions count - 97s
• Optimize slow compiling functions - 2s
• Fix warnings - 12s
• Apply ccache compiler cache utility -12s

Injection for Xcode plugin:
+ dynamically inserts new Swift / Objective-C code into a
running app
+ support «tunable parameters»
Source: https://github.com/johnno1962/injectionforxcode

Injection for Xcode plugin:
Source: https://github.com/johnno1962/injectionforxcode
Swift limitations. It’s not possible to:
- Make changes to Structs.
- Change functions or classes that are marked as ﬁnal.
- Change global functions or variables that are not
constrained into a class.

Split app into frameworks with no cyclic dependencies between
classes of different frameworks *
Plans
* idea and image: http://bits.citrusbyte.com/improving-swift-compile-time/

Further legacy code refactoring, remove Swift -
Objective C dependencies.
Plans

Links
• http://bits.citrusbyte.com/improving-swift-compile-time/
• http://stackoverflow.com/questions/25537614/why-is-swift-compile-time-so-slow
General:
• http://blog.impathic.com/post/99647568844/debugging-slow-swift-compile-times
• http://irace.me/swift-profiling
Debug slow compile time:
• https://tech.zalando.com/blog/speeding-up-xcode-builds/
• https://gist.github.com/lucholaf/e37f4d26e406250a156a
Speed up builds:
• https://developer.apple.com/videos/play/wwdc2015/409/
• http://useyourloaf.com/blog/swift-whole-module-optimization/
• http://useyourloaf.com/blog/modules-and-precompiled-headers/
• https://labs.spotify.com/2013/11/04/shaving-off-time-from-the-ios-edit-build-test-cycle/
• http://tomj.io/2015/08/29/speed-up-your-swift-test-builds-by-70-percent.html
• https://pewpewthespells.com/blog/managing_xcode.html#dep-imp
Build settings:
• https://pspdfkit.com/blog/2015/ccache-for-fun-and-profit/
• https://ccache.samba.org/manual.html#_configuration
ccache utility:

"Ускорение сборки большого проекта на Objective-C + Swift" Иван Бондарь (Avito)

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