How to speed up the Rust compiler in September 2026

The Rust compiler saw significant performance improvements in September 2026. Over 629 benchmark measurements showed a mean wall-time reduction of 4.57%, with 555 improvements and only 74 regressions. Notably, Jakub Beránek enabled profile-guided optimization for Clippy, resulting in an 18% speedup in the best case. Nikita Popov upgraded the compiler's LLVM version to 23, leading to a 1.2% mean reduction across benchmarks.

The new Polonius Alpha borrow checker, although slightly slower in some cases, improved compile times for many projects. Jack Huey's work on lazy liveness computations reduced instruction counts for serde and other benchmarks. The new trait solver, Penelope Hammertime, enabled on Nightly, also showed improvements in some cases. Multiple contributors, including xmakro, optimized various parts of the compiler, resulting in consistent and substantial performance gains across numerous benchmarks.