How to speed up the Rust compiler in September 2026

In one line

My last post on the Rust compiler’s performance was two months ago and a lot has happened since then.

Opening excerpt

The mean wall-time reduction was 4.57%, which is a remarkable improvement in just two months. Of the 629 benchmark measurements, 555 of them improved and only 74 regressed. A number of benchmarks saw double-digit percentage reductions. The technical term for this result is “a sea of green”.

In my last post I mentioned how Noah Lev got some enormous speed wins on rustdoc. He recently wrote a post explaining in some detail exactly how he did this. It’s an interesting and satisfying read.

#159642 : In this PR Jakub Beránek enabled PGO for Clippy, giving wall-time improvements across most Clippy benchmarks, in the best case by 18%!

#158734 : In this PR Nikita Popov upgraded the LLVM version used by the compiler to LLVM 23. As often happens when we upgrade LLVM, we saw some nice speedups. The mean wall-time reduction across all benchmarks was 1.2%, which might not sound like much but is really impressive for a single PR. Great work from the LLVM folks!

(Excerpted from the original; full article via the source link below.)

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