These are all the C versions I can find: https://benchmarksgame-team.pages.debian.net/benchmarksgame/program/revcomp-gcc-2.html https://benchmarksgame-team.pag

These are all the C versions I can find: https://benchmarksgame-team.pages.debian.net/benchmarksgame/program/revcomp-gcc-2.html https://benchmarksgame-team.pages.debian.net/benchmarksgame/... https://benchmarksgame-team.pages.debian.net/benchmarksgame/program/revcomp-gcc-4.html https://benchmarksgame-team.pages.debian.net/benchmarksgame/... https://benchmarksgame-team.pages.debian.net/benchmarksgame/program/revcomp-gcc-5.html https://benchmarksgame-team.pages.debian.net/benchmarksgame/... https://benchmarksgame-team.pages.debian.net/benchmarksgame/program/revcomp-gcc-6.html https://benchmarksgame-team.pages.debian.net/benchmarksgame/... None of them have SSE intrinsics or are quite as long as the Rust version. I find it doubtful that SSE intrinsics wouldn't help the C version, if they are indeed helping the Rust version. This seems fairly easy to check as the Rust version has a non-SSE fallback code path - I'd do it myself but am not able to at the moment.