Think of this chapter as a continuation of the previous chapter, "Bit Mangling."
This chapter deals with bit wrangling and thus the movement of bits. They can be shifted into oblivion, rotated, and watched going around and around. As Bugs Bunny would say, "Dizzing, ain't it!"
Bit wrangling actually occurs with the rotation and logical and arithmetic shifting of bits within each parallel bit range of packed bits. Just as in the scalar point of view of a similar general-purpose CPU instruction, the bits can be used for masking, base two multiplication and division, and other functionality.
It must be reiterated that you watch the alignment of your data objects in memory very closely. It takes extra overhead to adjust the memory ...