Function _mm256_insertf128_ps 

pub fn _mm256_insertf128_ps(a: __m256, b: __m128, const IMM1: i32) -> __m256

Available on x86-64 and target feature avx only.

Copies a to result, then inserts 128 bits (composed of 4 packed single-precision (32-bit) floating-point elements) from b into result at the location specified by imm8.

Intel’s documentation