Function horizontal_bin_op 

fn horizontal_bin_op<'tcx>(
    ecx: &mut MiriInterpCx<'tcx>,
    which: BinOp,
    saturating: bool,
    left: &OpTy<'tcx>,
    right: &OpTy<'tcx>,
    dest: &MPlaceTy<'tcx>,
) -> InterpResult<'tcx, ()>

Horizontally performs which operation on adjacent values of left and right SIMD vectors and stores the result in dest. “Horizontal” means that the i-th output element is calculated from the elements 2i and 2i+1 of the concatenation of left and right.

Each 128-bit chunk is treated independently (i.e., the value for the is i-th 128-bit chunk of dest is calculated with the i-th 128-bit chunks of left and right).