pipeline for Amaranth

pipe.py

with FSM():
    with m.State("Begin"):
        with m.If(self.strobe):
            m.next = "Process"
    with m.State("Process"):
        # Automatically create pipe.mult, pipe.shift
        with m.Pipeline([self.mult, self.shift]) as pipe:
            with pipe.Stage():
                # manually set up pipe.xor
                # XXX:  Do we want pipe.foo or just foo in mPipeline() scope?
                pipe.xor = signed(24)
                pipe.ans = signed(24)
                m.d.sync += [
                    pipe.xor.eq(self.xor)
                    pipe.ans.eq(self.a + self.b)
                ]
            with pipe.Stage(3):
                # All pipe.* registers from prior stage are moved forward
                # into a new set of registers for this stage
                # 3 cycle delay, i.e. this stage takes 4 cycles, because the
                # multiplier is slow.
                m.d.sync += pipe.ans.eq(pipe.ans * pipe.mult)
            with pipe.Stage():
                # This pipe.xor and pipe.shift contain the values from
                # stage 1 2 clock ticks ago 
                m.d.sync += pipe.ans.eq((pipe.ans ^ pipe.xor) << pipe.shift)
            with pipe.Stage():
                # Add a 1 cycle delay
                pass
        with m.If(!self.strobe):
            m.next = "Start"
# Connect the output registers from the pipeline to this component's outputs.
# This is the same timing as the final pipeline stage containing
# the below but with m.d.sync
m.d.comb += [
    self.output_ready.eq(pipe.ready),
    self.output_ans.eq(pipe.ans)
]