Rust: Faster linking times with 1.90.0 stable on Linux using the LLD linker

[NewsBot]

A new Rust blog post/announcement has been posted!

TL;DR: rustc will start using the LLD linker by default on the x86_64-unknown-linux-gnu target starting with the next stable release (1.90.0, scheduled for 2025-09-18), which should significantly reduce linking times. Test it out on beta now, and please report any encountered issues.

Some context

Linking time is often a big part of compilation time. When rustc needs to build a binary or a shared library, it will usually call the default linker installed on the system to do that (this can be changed on the command-line or by the target for which the code is compiled).

The linkers do an important job, with concerns about stability, backwards-compatibility and so on. For these and other reasons, on the most popular operating systems they usually are older programs, designed when computers only had a single core. So, they usually tend to be slow on a modern machine. For example, when building ripgrep 13 in debug mode on Linux, roughly half of the time is actually spent in the linker.

There are different linkers, however, and the usual advice to improve linking times is to use one of these newer and faster linkers, like LLVM's lld or Rui Ueyama's mold.

Some of Rust's wasm and aarch64 targets already use lld by default. When using rustup, rustc ships with a version of lld for this purpose. When CI builds LLVM to use in the compiler, it also builds the linker and packages it. It's referred to as rust-lld to avoid colliding with any lld already installed on the user's machine.

Since improvements to linking times are substantial, it would be a good default to use in the most popular targets. This has been discussed for a long time, for example in issues https://blog.rust-lang.org/2025/09/01/rust-lld-on-1.90.0-stable/