CLMUL instruction set

One use of these instructions is to improve the speed of applications doing block cipher encryption in Galois/Counter Mode, which depends on finite field GF(2^k) multiplication. Another application is the fast calculation of CRC values, including those used to implement the LZ77 sliding window DEFLATE algorithm in zlib and pngcrush.

ARMv8 also has a version of CLMUL. SPARC calls their version XMULX, for "XOR multiplication".

New instructions

The instruction computes the 128-bit carry-less product of two 64-bit values. The destination is a 128-bit XMM register. The source may be another XMM register or memory. An immediate operand specifies which halves of the 128-bit operands are multiplied. Mnemonics specifying specific values of the immediate operand are also defined:

A EVEX vectorized version (VPCLMULQDQ) is seen in AVX-512.