Function core::arch::x86_64::_mm256_insertf128_pd

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

Available on (x86 or x86-64) and target feature avx 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