Function _mm_hadd_pd

pub unsafe fn _mm_hadd_pd(a: __m128d, b: __m128d) -> __m128d

Available on (x86 or x86-64) and target feature sse3 and x86 only.

Horizontally adds adjacent pairs of double-precision (64-bit) floating-point elements in a and b, and pack the results.

Intel’s documentation