Rust: Faster compilation with the parallel front-end in nightly

[NewsBot]

A new Rust blog post/announcement has been posted!

The Rust compiler's front-end can now use parallel execution to significantly reduce compile times. To try it, run the nightly compiler with the -Z threads=8 option. This feature is currently experimental, and we aim to ship it in the stable compiler in 2024.

Keep reading to learn why a parallel front-end is needed and how it works, or just skip ahead to the How to use it section.

Compile times and parallelism

Rust compile times are a perennial concern. The Compiler Performance Working Group has continually improved compiler performance for several years. For example, in the first 10 months of 2023, there were mean reductions in compile time of https://blog.rust-lang.org/2023/11/09/parallel-rustc.html