pub unsafe fn _mm_clmulepi64_si128(
    a: __m128i,
    b: __m128i,
    const IMM8: i32
) -> __m128i
This is supported on x86-64 and target feature pclmulqdq only.
Expand description

Performs a carry-less multiplication of two 64-bit polynomials over the finite field GF(2^k).

The immediate byte is used for determining which halves of a and b should be used. Immediate bits other than 0 and 4 are ignored.

Intel’s documentation