Function core::arch::x86_64::_mm_alignr_epi8

pub unsafe fn _mm_alignr_epi8(
    a: __m128i, 
    b: __m128i, 
    const IMM8: i32
) -> __m128i

This is supported on x86-64 and target feature ssse3 only.

Concatenate 16-byte blocks in a and b into a 32-byte temporary result, shift the result right by n bytes, and returns the low 16 bytes.

Intel’s documentation