From: Jacob Lifshay Date: Wed, 15 May 2024 04:04:49 +0000 (-0700) Subject: add HDL implementation of decode_reducing_polynomial X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=caaf4a5d66d519cd3bfe2eb42d65a94aed61a676;p=nmigen-gf.git add HDL implementation of decode_reducing_polynomial --- diff --git a/src/nmigen_gf/hdl/decode_reducing_polynomial.py b/src/nmigen_gf/hdl/decode_reducing_polynomial.py new file mode 100644 index 0000000..f50dee8 --- /dev/null +++ b/src/nmigen_gf/hdl/decode_reducing_polynomial.py @@ -0,0 +1,51 @@ +# SPDX-License-Identifier: LGPL-3-or-later +# Copyright 2024 Jacob Lifshay programmerjake@gmail.com + +# Funded by NLnet Assure Programme 2021-02-052, https://nlnet.nl/assure part +# of Horizon 2020 EU Programme 957073. + +""" GF(2^n) + +https://bugs.libre-soc.org/show_bug.cgi?id=785 +""" + +from nmigen.hdl.ast import Signal +from nmigen.hdl.ir import Elaboratable +from nmigen.hdl.dsl import Module + + +class DecodeReducingPolynomial(Elaboratable): + """Decode the reducing polynomial from the REDPOLY SPR + + Properties: + XLEN: int + REDPOLY: Signal of width XLEN + input from the REDPOLY SPR + reducing_polynomial: Signal of width XLEN + 1 + decoded reducing polynomial output + """ + + def __init__(self, XLEN): + # type: (int) -> None + self.XLEN = XLEN + self.REDPOLY = Signal(XLEN) + self.reducing_polynomial = Signal(XLEN + 1) + + def elaborate(self, platform): + m = Module() + v = self.REDPOLY + with m.If((v == 0) | (v == 0b10)): # GF(2) + # degree = 1, poly = x + m.d.comb += self.reducing_polynomial.eq(0b10) + with m.Elif(v[0] == 0): + # all reducing polynomials of degree > 1 must have the LSB set, + # because they must be irreducible polynomials (meaning they + # can't be factored), if the LSB was clear, then they would + # have `x` as a factor. Therefore, we can reuse the LSB clear + # to instead mean the polynomial has degree XLEN. + m.d.comb += self.reducing_polynomial.eq(v) + m.d.comb += self.reducing_polynomial[self.XLEN].eq(1) + m.d.comb += self.reducing_polynomial[0].eq(1) # LSB must be set + with m.Else(): + m.d.comb += self.reducing_polynomial.eq(v) + return m diff --git a/src/nmigen_gf/hdl/test/test_decode_reducing_polynomial.py b/src/nmigen_gf/hdl/test/test_decode_reducing_polynomial.py new file mode 100644 index 0000000..47f4ce2 --- /dev/null +++ b/src/nmigen_gf/hdl/test/test_decode_reducing_polynomial.py @@ -0,0 +1,68 @@ +# SPDX-License-Identifier: LGPL-3-or-later +# Copyright 2024 Jacob Lifshay programmerjake@gmail.com + +# Funded by NLnet Assure Programme 2021-02-052, https://nlnet.nl/assure part +# of Horizon 2020 EU Programme 957073. + +""" GF(2^n) + +https://bugs.libre-soc.org/show_bug.cgi?id=785 +""" + +import unittest +from nmigen.hdl.ast import Const, unsigned +from nmutil.formaltest import FHDLTestCase +from nmigen_gf.reference.decode_reducing_polynomial import \ + decode_reducing_polynomial +from nmigen_gf.hdl.decode_reducing_polynomial import DecodeReducingPolynomial +from nmigen.sim import Delay +from nmutil.sim_util import do_sim, hash_256 +from nmigen_gf.reference.state import ST + + +class TestDecodeReducingPolynomial(FHDLTestCase): + def tst(self, XLEN): + # type: (int) -> None + dut = DecodeReducingPolynomial(XLEN) + self.assertEqual(dut.XLEN, XLEN) + self.assertEqual(dut.REDPOLY.width, XLEN) + self.assertEqual(dut.reducing_polynomial.width, XLEN + 1) + + def case(REDPOLY): + ST.reinit(XLEN=XLEN, GFBREDPOLY=REDPOLY) + expected = decode_reducing_polynomial() + with self.subTest(XLEN=XLEN, + REDPOLY=hex(REDPOLY), + expected=hex(expected)): + yield dut.REDPOLY.eq(REDPOLY) + yield Delay(1e-6) + reducing_polynomial = yield dut.reducing_polynomial + with self.subTest(output=hex(reducing_polynomial)): + self.assertEqual(expected, reducing_polynomial) + + def process(): + for i in range(100): + v = hash_256("dec_rpoly XLEN %i %i REDPOLY" % (XLEN, i)) + shift = hash_256("dec_rpoly XLEN %i %i shift" % (XLEN, i)) + v >>= shift % XLEN + REDPOLY = Const.normalize(v, unsigned(XLEN)) + yield from case(REDPOLY) + with do_sim(self, dut, [dut.REDPOLY, dut.reducing_polynomial]) as sim: + sim.add_process(process) + sim.run() + + def test_8(self): + self.tst(8) + + def test_16(self): + self.tst(16) + + def test_32(self): + self.tst(32) + + def test_64(self): + self.tst(64) + + +if __name__ == "__main__": + unittest.main()