Move the lower 2 single-precision (32-bit) floating-point elements from b to the upper 2 elements of result, and copy the lower 2 elements from a to the lower 2 elements of result
See Implementation
Move the lower 2 single-precision (32-bit) floating-point elements from b to the upper 2 elements of result, and copy the lower 2 elements from a to the lower 2 elements of result