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 #39915 and #71515.

To expand our testing, we have enabled rustc to use rust-lld by default on nightly, in May 2024. No major issues have been reported since then.

We believe we’ve done all the internal testing that we could, on CI, crater, on our benchmarking infrastructure and on nightly, and plan to enable rust-lld to be the linker used by default on x86_64-unknown-linux-gnu for stable builds in 1.90.0.

Benefits

While this also enables the compiler to use more linker features in the future, the most immediate benefit is much improved linking times.

Here are more details from the ripgrep example mentioned above: for an incremental rebuild, linking is reduced 7x, resulting in a 40% reduction in end-to-end compilation times. For a from-scratch debug build, it is a 20% improvement.

Most binaries should see some improvements here, but it’s especially significant with e.g. bigger binaries, or for incremental rebuilds, or when involving debuginfo. These usually see bottlenecks in the linker.

Here’s a link to the complete results from our benchmarks.

Possible drawbacks

From our prior testing, we don’t really expect issues to happen in practice. It is a drop-in replacement for the vast majority of cases, but lld is not bug-for-bug compatible with GNU ld.

In any case, using rust-lld can be disabled if any problem occurs: use the -C linker-features=-lld flag to revert to using the system’s default linker.

Some crates somehow relying on these differences could need additional link args, though we also expect this to be quite rare. Let us know if you encounter problems, by opening an issue on GitHub.

Some of the big gains in performance come from parallelism, which could be undesirable in resource-constrained environments, or for heavy projects that are already reaching hardware limits.

Summary, and call for testing

rustc will use rust-lld on x86_64-unknown-linux-gnu, starting with the 1.90.0 stable release, for much improved linking times. Rust 1.90.0 will be released next month, on the 18th of September 2025.

This linker change is already available on the current beta (1.90.0-beta.6). To help everyone prepare for this landing on stable, please test your projects on beta and let us know if you encounter problems, by opening an issue on GitHub.

If that happens, you can revert to the default linker with the -C linker-features=-lld flag. Either by adding it to the usual RUSTFLAGS environment variable, or to a project’s .cargo/config.toml configuration file, like so:

[target.x86_64-unknown-linux-gnu]
rustflags = ["-Clinker-features=-lld"]