[panic]

Do you have experience writing Swift or Obj-C programs? My experience is that Obj-C has predictable performance which is often "good enough", whereas Swift is either too slow (without optimizations) or takes a very long time to compile (with optimizations enabled).

As a concrete example, I took a Swift program I had lying around (8 files, 2854 lines total), compiled it without optimizations, and stress-tested it a bit. Here's what the "bottom-up" profile looks like: https://i.imgur.com/ohlKQgx.png -- tons of time wasted in Swift runtime overhead. Compiling with optimizations removes most of the overhead, but a clean build of this (relatively small) program took almost 5 minutes with optimizations enabled.

[i2om3r]

Did you compare it to a roughly equivalent Objective-C program? The top four entries in your profile data show retain, release and objc_msgSend. You will have those in Objective-C too. Maybe to a different degree? That's also why I am asking whether you have similar Objective-C code to test. Or maybe it's just that unoptimized Swift code is slower and optimized code is faster?

Compile times are a related but different matter. There are -warn-long-function-bodies and recently -warn-long-expression-type-checking which are really helpful and can give you an idea where most of the compile time is spent. In my experience, the type checker can spend a lot of time in mildly complex expressions involving overload resolution, which can be really annoying but there are often ways around it. With those culprits being eliminated, I have never encountered 5 minute build times for projects of this size or bigger, and I like to imagine that I write fairly generic code.

[panic]

Thanks, I didn't know about those flags! I suspect there was a pathological expression somewhere, since most of that time was spent in a single file.