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 show a mean wall-time reduction of 4.57%, a remarkable improvement in just two months. Of the 629 benchmark measurements, 555 improved and only 74 regressed, creating what is technically called "a sea of green".
Jakub Beránek enabled PGO for Clippy in PR #159642, giving wall-time improvements across most Clippy benchmarks, in the best case by 18%. Nikita Popov upgraded the LLVM version to LLVM 23 in PR #158734, achieving a mean wall-time reduction of 1.2% across all benchmarks.
The new borrow checker, Polonius Alpha, was enabled on Nightly. It is more precise but slower in a minority of cases, including the popular serde crate. Jack Huey made liveness computations lazy in PR #161938, reducing instruction counts for serde by 3-5%, and adjusted a data structure in PR #163027 for sub-1% reductions.
The new trait solver, Penelope Hammertime, was also enabled on Nightly. Jana Dönszelmann wrote a detailed post about performance improvements. New contributor xmakro optimized impl handling in PR #157281, giving a mean cycle count reduction of 1.58% across all benchmarks, and avoided allocations in a hot obligations processing path in PR #160473, reducing instruction counts by up to 2%.
Source: Hacker News · Summarized by HeadlinesBriefing