Don't stop early: Case-folding source code at memory speed

2026-08-05

Case folding is an operation in text processing that makes sure strings differing only in case are treated as equal, but achieving this quickly at scale is a challenge. GitHub's code search engine, Blackbird, efficiently implements case folding by using a branch-free loop and byte-space arithmetic, enabling it to process ASCII characters at speeds exceeding 45 GiB/s on a single core.