booth - map $mul cells to Booth multipliers

yosys> help booth

booth [selection]

This pass replaces multiplier cells with a radix-4 Booth-encoded implementation.
It operates on $mul cells whose width of operands is at least 4x4 and whose
width of result is at least 8.

-lowpower

use an alternative low-power architecture for the generated multiplier
(signed multipliers only)