How to speed up the Rust compiler in September 2026
This technical update details recent performance improvements in the Rust programming language compiler, including optimizations to the borrow checker and LLVM upgrades. The report highlights significant reductions in compile times achieved through various pull requests.
Why it matters
Performance improvements in core programming tools directly impact developer productivity and the efficiency of software ecosystems.
My last post on the Rust compiler’s performance was two months ago and a lot has happened since then.
The measurements for the period 2026-07-29 to 2026-09-28 can be seen here .
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%!
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