One patent is https://patents.google.com/patent/US6721866B2 which is for LDDQU and probably would not matter for an emulator. I wonder about https://patents.google.com/patent/US7155601B2/en which is a patent on PSHUFLW/PSHUFHW. I wonder if a CPU instruction in which the only difference is that it operates on different registers is patentable.