OK, another commenter linked to crc32 in the Go standard library: https://github.com/golang/go/tree/master/src/hash/crc32 https://github.com/golang/go/tree/mas

OK, another commenter linked to crc32 in the Go standard library: https://github.com/golang/go/tree/master/src/hash/crc32 https://github.com/golang/go/tree/master/src/hash/crc32 That has different .s files for different architectures, and a .go file with the platform-independent version, so the assembly clearly isn't platform-independent. It seems a strange decision to disguise e.g. arm64 assembly behind an x86-like syntax, so I'm going to go with "quirk of the implementation."