Performance issues on large projects with Objective-C code

[ilyakuteev]

Hi all. Currently I am working on a big Swift/Objc project. When using old swift driver (Via -disallow-use-new-driver option) the performance is great, but when I switch to new-swift-driver compilation is stuck on every large swift module. Time taken by swift-driver to analyze dependencies can be longer than actual time to compile the whole module. The largest module has about 700 sources and contains 182 imports (Counted by -emit-imported-modules), half of them are Objc modules.

After some research I figured out that disabling emitting dependsExternal section to swiftdeps file slightly increaces driver speed. Maybe it will help somehow.

I am looking for a patch or some architecture solution (For example isolating all Objc modules with @_implementationOnly imports) and will be happy with any help.

[ilyakuteev]

Similar topic: https://forums.swift.org/t/swift-incremental-build-external-dependencies/37271