On modern enough x86 CPUs (Intel Broadwell, AMD Ryzen) you could also use ADX [1] which may be faster nowadays in situations where radix 2^51 representation tra

On modern enough x86 CPUs (Intel Broadwell, AMD Ryzen) you could also use ADX [1] which may be faster nowadays in situations where radix 2^51 representation traditionally had an edge (e.g. Curve25519). [1] https://en.wikipedia.org/wiki/Intel_ADX https://en.wikipedia.org/wiki/Intel_ADX