attacks.py

from nmigen import Const, Elaboratable, Module, Repl, Signal
from nmigen.cli import main


class PositiveAttacks(Elaboratable):
    def __init__(self, shift, mask):
        self.gen = Signal(64)
        self.prop = Signal(64)
        self.output = Signal(64)

        self.shift = shift
        self.mask = mask

    def elaborate(self, platform):
        m = Module()

        prop = Signal(64)
        gen = Signal(64)

        m.d.comb += [
                prop.eq(self.prop & self.mask),
                gen.eq(self.gen | prop & (self.gen << self.shift)),
                # Breaks when the following two lines are uncommented
                # prop.eq(prop & (prop << self.shift)),
                # gen.eq(gen | prop & (gen << self.shift)),
                self.output.eq(gen)
        ]

        return m


if __name__ == "__main__":
    pa = PositiveAttacks(8, Repl(Const(1), 64))
    main(pa, ports=[pa.gen, pa.prop, pa.output])