- shift circuits are used in most arithmetic operations
- in usual shifters, the shift delay is proportional to the size of the shift
- a barrel shifter (バレル・シフタ) can shift by any number of bits in constant time

* Crossbar Barrel Shifter*

- the bits are rotated by the shift count
- the delay is constant
- for an
*N*bit shifter, the number of gates required is proportional to*N*^{2}

*Logarithmic Barrel Shifter*

- a logarithmic barrel shifter is shown in Figure 5.1
- the delay is proportional to the log of the shift count
- the number of gates required is proportional to

time / complexity tradeoff