Merges the least significant halves of two vectors.
Elemental function
The result is of the same type as ARG1.
Assume that the elements of each vector are numbered beginning with 0. The even-numbered elements of the result are taken, in order, from the elements in the least significant 8 bytes of ARG1. The odd-numbered elements of the result are taken, in order, from the elements in the least significant 8 bytes of ARG2.