Biggest category of libraries that need inline assembly with compiler portability are compression/decompression codecs (like the linked article) -- think of ima

Biggest category of libraries that need inline assembly with compiler portability are compression/decompression codecs (like the linked article) -- think of images (PNG, JPEG), audio (MP3, Opus, FLAC), video (MPEG4, H.264, AV1). Also important is cryptography, where inline assembly provides more deterministic performance than compiler-generated instructions. Compiler intrinsics can get you pretty far, but sometimes dropping down to assembly is the only solution. In those times, inline assembly can be more ergonomic than separate .s source files.