from nmigen import *
from nmigen.asserts import *

"""
Liveness Check
"""

class LivenessCheck(Elaboratable):
    def __init__(self):
        self.reset = Signal(1)
        self.rvfi_order = Signal(64)
        self.trig = Signal(1)
        self.rvfi_valid = Signal(1)
        self.rvfi_halt = Signal(1)
        self.check = Signal(1)

    def ports(self):
        input_ports = [
            self.reset,
            self.rvfi_order,
            self.trig,
            self.rvfi_valid,
            self.rvfi_halt,
            self.check
        ]
        return input_ports

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

        insn_order = AnyConst(64)
        found_next_insn = Signal(1, reset=0)

        with m.If(self.reset):
            m.d.sync += found_next_insn.eq(0)
        with m.Else():
            with m.If(self.rvfi_valid & (self.rvfi_order == insn_order + 1)):
                m.d.sync += found_next_insn.eq(1)
            with m.If(self.trig):
                m.d.comb += Assume(self.rvfi_valid)
                m.d.comb += Assume(~self.rvfi_halt)
                m.d.comb += Assume(insn_order == self.rvfi_order)
            with m.If(self.check):
                m.d.comb += Assert(found_next_insn)

        return m