See my little test program at https://godbolt.org/g/53SAMq https://godbolt.org/g/53SAMq I believe this program properly handles carry from the low to high part

See my little test program at https://godbolt.org/g/53SAMq https://godbolt.org/g/53SAMq I believe this program properly handles carry from the low to high part. The 96- and 128-bit code have the same number of instructions, but the 128-bit code has more instruction bytes due to "REX prefixes" (i.e., 32-bit register add is 3 bytes of opcode, 64-bit register add is 4)