Long compilation time

[jens1o]

Hey folks,

from time to time I see this, when I compile a project. This is like the crate that takes the longest time to finish. :/ Is there something I can help to speed it up?

Regards

[Manishearth]

That's surprising, are you sure it's this crate that's the bottleneck and not a different one? Cargo builds things in parallel and it's hard to tell from the output what the currently building crates are. Nightly has better output for this.

I'm unable to reproduce any slowness with a quick test.

[jens1o]

Well, for example when I type in cargo install diesel_cli, I always see unicode-normalization for quite a moment and other jobs waiting for it, because, as soon as it's done, other crates start to build. I'll take an eye on this.

[Manishearth]

Oh, wait, no, was compiling the wrong thing.

Yeah this contains some giant match statements which are slow. We could perhaps use something like phf_map here but that may not improve compile times.

[jens1o]

Okay, so as there is nothing you can do here, I'll just close it?

[Manishearth]

It's worth filing an issue on the rust repo for this. There is stuff we can try here, though

[raphlinus]

One approach that might address this (and I'm considering for other reasons, mostly because I need raw data for HarfBuzz integration) is to use a script to generate perfect hash maps from the Unicode data, and check those hash maps into the repo. Using a crate like phf_map would work, but would add the compilation time and run time for phf_map to the total compile.

I am happy to measure and PR this approach if there's interest.