Function _mm256_insertf128_pd

pub unsafe fn _mm256_insertf128_pd<const IMM1: i32>(
    a: __m256d,
    b: __m128d,
) -> __m256d

Available on x86 only.

Copies a to result, then inserts 128 bits (composed of 2 packed double-precision (64-bit) floating-point elements) from b into result at the location specified by imm8.

Intel’s documentation