path: root/hdl/core/alu.py

from amaranth import *
from amaranth.sim import Simulator, Settle, Delay
from enum import Enum, unique

from hdl.utils import cmd, DubbleBuff

@unique
class AluOpCodes(Enum):
    add = 0
    addc = 1
    sub = 2
    subc = 3
    bit_and = 4
    bit_or = 5
    bit_xor = 6
    bit_nor = 7
    lleft = 8
    lright = 9
    aright = 10
    set_bit = 11
    clear_bit = 12
    umult = 13
    smult = 14
    udiv = 15
    sdiv = 16

class ALU(Elaboratable):
    def __init__(self, **kargs):
        self.in1 = Signal(32, reset_less=True)
        self.in2 = Signal(32, reset_less=True)
        self.c_in = Signal(1)
        self.op = Signal(4, reset_less=True)

        self.tmp = Signal(33, reset_less=True)

        self.c_out = Signal(1, reset_less=True)
        self.overflow = Signal(1, reset_less=True)
        self.zero = Signal(1, reset_less=True)
        self.neg = Signal(1, reset_less=True)
        self.odd = Signal(1, reset_less=True)

        self.out = Signal(32, reset_less=True)

        self.sim = kargs["sim"] if "sim" in kargs else None

        ports_in = [self.in1, self.in2, self.op, self.c_in]
        ports_out = [self.c_in, self.out, self.c_out, self.overflow, self.zero, self.neg, self.odd]
        self.ports = {'in': ports_in, 'out': ports_out}

    def elaborate(self, platform=None):
        m = Module()

        # dummy sync for simulation only
        if self.sim == True:
            dummy = Signal()
            m.d.sync += dummy.eq(~dummy)

        with m.Switch(self.op):
            with m.Case(AluOpCodes.add.value):
                m.d.comb += self.tmp.eq(self.in1 + self.in2)

            with m.Case(AluOpCodes.addc.value):
                m.d.comb += self.tmp.eq(self.in1 + self.in2 + self.c_in)

            with m.Case(AluOpCodes.sub.value):
                m.d.comb += self.tmp.eq(self.in1 - self.in2)

            with m.Case(AluOpCodes.subc.value):
                m.d.comb += self.tmp.eq(self.in1 + (~self.in2 + self.c_in))

            with m.Case(AluOpCodes.bit_and.value):
                m.d.comb += self.tmp.eq(Cat(self.in1 & self.in2, 0))

            with m.Case(AluOpCodes.bit_or.value):
                m.d.comb += self.tmp.eq(Cat(self.in1 | self.in2, 0))

            with m.Case(AluOpCodes.bit_xor.value):
                m.d.comb += self.tmp.eq(Cat(self.in1 ^ self.in2, 0))
            
            with m.Case(AluOpCodes.bit_nor.value):
                m.d.comb += self.tmp.eq(Cat(~(self.in1 | self.in2), 0))

            with m.Case(AluOpCodes.lleft.value):
                m.d.comb += self.tmp.eq(Cat(self.in1, 0) << self.in2[0:5])

            with m.Case(AluOpCodes.lright.value):
                tmp2 = Signal(33)
                m.d.comb += tmp2.eq(Cat(0, self.in1) >> self.in2[0:5])
                m.d.comb += self.tmp.eq(Cat(tmp2[1:33], tmp2[0]))   # move shifted bit to carry bit

            with m.Case(AluOpCodes.aright.value):
                tmp2 = Signal(33)
                m.d.comb += tmp2.eq(Cat(0, self.in1).as_signed() >> self.in2[0:5])
                m.d.comb += self.tmp.eq(Cat(tmp2[1:33], tmp2[0]))   # move shifted bit to carry bit

            with m.Case(AluOpCodes.set_bit.value):
                m.d.comb += self.tmp.eq(Cat(self.in1 | (1 << self.in2[0:5]), 0))

            with m.Case(AluOpCodes.clear_bit.value):
                m.d.comb += self.tmp.eq(Cat(self.in1 & ~(1 << self.in2[0:5]), 0))

            with m.Case(AluOpCodes.umult.value):
                m.d.comb += self.tmp.eq(Cat(self.in1[0:16] * self.in2[0:16], 0))
            
            with m.Case(AluOpCodes.smult.value):
                m.d.comb += self.tmp.eq(Cat(self.in1[0:16].as_signed() * self.in2[0:16].as_signed(), 0))
            

            # bad juju, 
            # TODO: come back and check this will work
            # with m.Case(AluOpCodes.udiv.value):
            #     m.d.comb += self.tmp.eq(Cat(self.in1 // self.in2, 0))
            
            # with m.Case(AluOpCodes.sdiv.value):
            #     m.d.comb += self.tmp.eq(self.in1.as_signed() // self.in2.as_signed())   # for some reason I have not confirmed, signed div can yield a 33 bit number, acording to amaranth

            with m.Case():
                m.d.comb += self.tmp.eq(0)
        
        m.d.comb += self.c_out.eq(self.tmp[32])
        m.d.comb += self.overflow.eq(self.tmp[32] ^ self.tmp[31])
        m.d.comb += self.out.eq(self.tmp[0:32])
        m.d.comb += self.neg.eq(self.out[31])
        m.d.comb += self.zero.eq(self.out == 0)
        m.d.comb += self.odd.eq(self.out.xor())     # 1 if odd number of bits, 0 if even
        
        return m

def test_alu(filename="alu.vcd"):
    dut = ALU(sim=True)

    def proc1():
        def sub_proc(val1, val2, c_in=0):
            yield dut.in1.eq(val1)
            yield dut.in2.eq(val2)
            yield dut.c_in.eq(c_in)
            yield
            yield Settle()

        # test addition
        yield dut.op.eq(AluOpCodes.add.value)
        yield from sub_proc(27, 13)
        out = yield dut.out
        assert 27 + 13 == (out), f'ERROR: {out} != {27 + 13}'

        # test addition with carry
        yield dut.op.eq(AluOpCodes.addc.value)
        yield from sub_proc(11, 43, 1)
        out = yield dut.out.as_signed()
        assert 11 + 43 + 1 == out, f'ERROR: {out} != {11 + 43 + 1}'

        # test subtraction
        yield dut.op.eq(AluOpCodes.sub.value)
        yield from sub_proc(25, 13)
        out = yield dut.out
        assert 25 - 13 == out, f'ERROR: {out} != {25 - 13}'
        
        # test subtraction with carry
        yield dut.op.eq(AluOpCodes.subc.value)
        yield from sub_proc(25, -13, 0)
        out = yield dut.out.as_signed()
        assert 25 + 13 -1 +0 == out, f'ERROR: {out} != {25 + 13 -1 +0}'

        # test subtraction with carry
        yield dut.op.eq(AluOpCodes.subc.value)
        yield from sub_proc(25, -13, 1)
        out = yield dut.out.as_signed()
        assert 25 + 13 -1 +1 == out, f'ERROR: {out} != {25 + 13 -1 +1}'

        # test binary and
        yield dut.op.eq(AluOpCodes.bit_and.value)
        yield from sub_proc(0b10101011, 0b01010101)
        out = yield dut.out
        assert 0b00000001 == out, f'ERROR: {out} != {0b00000001}'

        # test binary or
        yield dut.op.eq(AluOpCodes.bit_or.value)
        yield from sub_proc(0b10101011, 0b01000101)
        out = yield dut.out
        assert 0b11101111 == out, f'ERROR: {out} != {0b11101111}'

        # test binary nor
        yield dut.op.eq(AluOpCodes.bit_nor.value)
        yield from sub_proc(0b10001011, 0b01000101)
        out = yield dut.out
        assert 0b11111111111111111111111100110000 == out, f'ERROR: {bin(out)} != {bin(0b11111111111111111111111100110000)}'

        # test binary xor
        yield dut.op.eq(AluOpCodes.bit_xor.value)
        yield from sub_proc(0b10001011, 0b01000101)
        out = yield dut.out
        assert 0b11001110 == out, f'ERROR: {out} != {0b11001110}'

        # test logical shift left
        yield dut.op.eq(AluOpCodes.lleft.value)
        yield from sub_proc(0b10001011, 25) # shift left by 5
        out = yield dut.out
        assert 0b00010110000000000000000000000000 == out, f'ERROR: {bin(out)} != {bin(0b00010110000000000000000000000000)}'
        out = yield dut.c_out
        assert 1 == out, f'ERROR: {out} != {1}'

        # test logical shift right
        yield dut.op.eq(AluOpCodes.lright.value)
        yield from sub_proc(0b10001011, 4) # shift right by 5
        out = yield dut.out
        assert 0b1000 == out, f'ERROR: {bin(out)} != {bin(0b1000)}'
        out = yield dut.c_out
        assert 1 == out, f'ERROR: {out} != {1}'

        # test aligned shift right
        yield dut.op.eq(AluOpCodes.aright.value)
        yield from sub_proc(0x80001234, 4) # shift right by 4
        out = yield dut.out
        assert 0xF8000123 == out, f'ERROR: {out} != {0xF8000123}'
        out = yield dut.c_out
        assert 0 == out, f'ERROR: {out} != {0}'

        # test unsigned overflow
        yield dut.op.eq(AluOpCodes.add.value)
        yield from sub_proc(0xFFFFFFFF, 1) # add 1 to 0xFFFFFFFF
        out = yield dut.overflow
        assert out == 1, f'ERROR: {out} != {1}'
        out = yield dut.c_out
        assert out == 1, f'ERROR: {out} != {1}'

        # test unsigned underflow
        yield dut.op.eq(AluOpCodes.add.value)
        yield from sub_proc(0, -1) # subtract 1 from 0
        out = yield dut.overflow
        assert out == 1, f'ERROR: {out} != {1}'
        out = yield dut.c_out
        assert out == 0, f'ERROR: {out} != {0}'

        # test zero
        yield dut.op.eq(AluOpCodes.add.value)
        yield from sub_proc(0, 0) # add 0 to 0
        out = yield dut.zero
        assert out == 1, f'ERROR: {out} != {1}'

        # test zero
        yield dut.op.eq(AluOpCodes.add.value)
        yield from sub_proc(0, 1) # add 0 to 0
        out = yield dut.zero
        assert out == 0, f'ERROR: {out} != {0}'

        # test odd
        yield dut.op.eq(AluOpCodes.add.value)
        yield from sub_proc(0, 0xAAAAAAAA) # add 0 to 0
        out = yield dut.odd
        assert out == 0, f'ERROR: {out} != {0}'

        # test odd
        yield dut.op.eq(AluOpCodes.add.value)
        yield from sub_proc(0, 0xAAAAAAAB) # add 0 to 0
        out = yield dut.odd
        assert out == 1, f'ERROR: {out} != {1}'
        

    sim = Simulator(dut)
    sim.add_clock(1e-6)
    sim.add_sync_process(proc1)
    
    with sim.write_vcd(filename):
        sim.run()


if __name__ == '__main__':
    hdl = DubbleBuff(ALU())
    cmd(hdl, test_alu)