Round the lower single-precision (32-bit) floating-point element in b up to an integer value,
store the result as a single-precision floating-point element in the lower element of result,
and copy the upper 3 packed elements from a to the upper elements of result.
Round the lower single-precision (32-bit) floating-point element in b up to an integer value, store the result as a single-precision floating-point element in the lower element of result, and copy the upper 3 packed elements from a to the upper elements of result.