self.we = Signal(we_width); """write enable"""
# debug signals, only used in formal proofs
self.dbg_addr = Signal(addr_width); """debug: address under test"""
- self.dbg_we_mask = Signal(we_width); """debug: write lane under test"""
+ lanes = range(we_width)
+ self.dbg_lane = Signal(lanes); """debug: write lane under test"""
gran = self.data_width // self.we_width
self.dbg_data = Signal(gran); """debug: data to keep in sync"""
self.dbg_wrote = Signal(); """debug: data is valid"""
# now, ensure that the value stored in memory is always in sync
# with the holding register
with m.If(self.dbg_wrote):
- for i in range(self.we_width):
- with m.If(self.dbg_we_mask[i]):
- m.d.sync += Assert(self.dbg_data ==
- stored.word_select(i, gran))
+ m.d.sync += Assert(self.dbg_data ==
+ stored.word_select(self.dbg_lane, gran))
return m
gran = len(dut.d) // len(dut.we) # granularity
# choose a single random memory location to test
a_const = AnyConst(dut.a.shape())
- # choose a single byte lane to test (one-hot encoding)
- we_mask = Signal.like(dut.we)
- # ... by first creating a random bit pattern
- we_const = AnyConst(dut.we.shape())
- # ... and zeroing all but the first non-zero bit
- m.d.comb += we_mask.eq(we_const & (-we_const))
+ # choose a single byte lane to test
+ lane = AnyConst(range(dut.we_width))
# holding data register
d_reg = Signal(gran)
# for some reason, simulated formal memory is not zeroed at reset
wrote = Signal()
# if our memory location and byte lane is being written
# ... capture the data in our holding register
- with m.If(dut.a == a_const):
- for i in range(len(dut.we)):
- with m.If(we_mask[i] & dut.we[i]):
- m.d.sync += d_reg.eq(dut.d[i*gran:i*gran+gran])
- m.d.sync += wrote.eq(1)
+ with m.If((dut.a == a_const) & dut.we.bit_select(lane, 1)):
+ m.d.sync += d_reg.eq(dut.d.word_select(lane, gran))
+ m.d.sync += wrote.eq(1)
# if our memory location is being read
# ... and the holding register has valid data
# ... then its value must match the memory output, on the given lane
with m.If((Past(dut.a) == a_const) & wrote):
- for i in range(len(dut.we)):
- with m.If(we_mask[i]):
- m.d.sync += Assert(d_reg == dut.q[i*gran:i*gran+gran])
+ m.d.sync += Assert(d_reg == dut.q.word_select(lane, gran))
# pass our state to the device under test, so it can ensure that
# its state is in sync with ours, for induction
m.d.comb += [
dut.dbg_addr.eq(a_const),
- dut.dbg_we_mask.eq(we_mask),
+ dut.dbg_lane.eq(lane),
dut.dbg_data.eq(d_reg),
dut.dbg_wrote.eq(wrote),
]
self.phase = Signal(); """even/odd cycle indicator"""
# debug signals, only used in formal proofs
self.dbg_addr = Signal(addr_width); """debug: address under test"""
- self.dbg_we_mask = Signal(we_width); """debug: write lane under test"""
+ lanes = range(we_width)
+ self.dbg_lane = Signal(lanes); """debug: write lane under test"""
gran = self.data_width // self.we_width
self.dbg_data = Signal(gran); """debug: data to keep in sync"""
self.dbg_wrote = Signal(); """debug: data is valid"""
# pass the address and write lane under test to both memories
mem1.dbg_addr.eq(self.dbg_addr),
mem2.dbg_addr.eq(self.dbg_addr),
- mem1.dbg_we_mask.eq(self.dbg_we_mask),
- mem2.dbg_we_mask.eq(self.dbg_we_mask),
+ mem1.dbg_lane.eq(self.dbg_lane),
+ mem2.dbg_lane.eq(self.dbg_lane),
# the second memory copies its state from the first memory,
# after a cycle, so it has a one cycle delay
mem1.dbg_data.eq(self.dbg_data),
return m
+ def ports(self):
+ return [
+ self.wr_addr_i,
+ self.wr_data_i,
+ self.wr_we_i,
+ self.rd_addr_i,
+ self.rd_data_o,
+ self.phase
+ ]
+
class PhasedDualPortRegfileTestCase(FHDLTestCase):
gran = dut.data_width // dut.we_width # granularity
# choose a single random memory location to test
a_const = AnyConst(dut.addr_width)
- # choose a single byte lane to test (one-hot encoding)
- we_mask = Signal(dut.we_width)
- # ... by first creating a random bit pattern
- we_const = AnyConst(dut.we_width)
- # ... and zeroing all but the first non-zero bit
- m.d.comb += we_mask.eq(we_const & (-we_const))
+ # choose a single byte lane to test
+ lane = AnyConst(range(dut.we_width))
# drive alternating phases
m.d.comb += Assume(dut.phase != Past(dut.phase))
# holding data register
# if our memory location and byte lane is being written,
# capture the data in our holding register
with m.If((dut.wr_addr_i == a_const)
+ & dut.wr_we_i.bit_select(lane, 1)
& (dut.phase == dut.write_phase)):
- for i in range(dut.we_width):
- with m.If(we_mask[i] & dut.wr_we_i[i]):
- m.d.sync += d_reg.eq(
- dut.wr_data_i[i * gran:i * gran + gran])
- m.d.sync += wrote.eq(1)
+ m.d.sync += d_reg.eq(dut.wr_data_i.word_select(lane, gran))
+ m.d.sync += wrote.eq(1)
# if our memory location is being read,
# and the holding register has valid data,
# then its value must match the memory output, on the given lane
with m.If(Past(dut.rd_addr_i) == a_const):
if transparent:
with m.If(wrote):
- for i in range(dut.we_width):
- rd_lane = dut.rd_data_o.word_select(i, gran)
- with m.If(we_mask[i]):
- m.d.sync += Assert(d_reg == rd_lane)
+ rd_lane = dut.rd_data_o.word_select(lane, gran)
+ m.d.sync += Assert(d_reg == rd_lane)
else:
# with a non-transparent read port, the read value depends
# on whether there is a simultaneous write, or not
& Past(dut.phase) == dut.write_phase):
# simultaneous write -> check against last written value
with m.If(Past(wrote)):
- for i in range(dut.we_width):
- rd_lane = dut.rd_data_o.word_select(i, gran)
- with m.If(we_mask[i]):
- m.d.sync += Assert(Past(d_reg) == rd_lane)
+ rd_lane = dut.rd_data_o.word_select(lane, gran)
+ m.d.sync += Assert(Past(d_reg) == rd_lane)
with m.Else():
# otherwise, check against current written value
with m.If(wrote):
- for i in range(dut.we_width):
- rd_lane = dut.rd_data_o.word_select(i, gran)
- with m.If(we_mask[i]):
- m.d.sync += Assert(d_reg == rd_lane)
+ rd_lane = dut.rd_data_o.word_select(lane, gran)
+ m.d.sync += Assert(d_reg == rd_lane)
# pass our state to the device under test, so it can ensure that
# its state is in sync with ours, for induction
m.d.comb += [
# address and mask under test
dut.dbg_addr.eq(a_const),
- dut.dbg_we_mask.eq(we_mask),
+ dut.dbg_lane.eq(lane),
# state of our holding register
dut.dbg_data.eq(d_reg),
dut.dbg_wrote.eq(wrote),
self.data_width = data_width
self.we_width = we_width
self.transparent = transparent
+ # interface signals
self.wr_addr_i = Signal(addr_width); """write port address"""
self.wr_data_i = Signal(data_width); """write port data"""
self.wr_we_i = Signal(we_width); """write port enable"""
self.rd_addr_i = Signal(addr_width); """read port address"""
self.rd_data_o = Signal(data_width); """read port data"""
+ # debug signals, only used in formal proofs
+ # address and write lane under test
+ self.dbg_addr = Signal(addr_width); """debug: address under test"""
+ lanes = range(we_width)
+ self.dbg_lane = Signal(lanes); """debug: write lane under test"""
+ # upstream state, to keep in sync with ours
+ gran = self.data_width // self.we_width
+ self.dbg_data = Signal(gran); """debug: data to keep in sync"""
+ self.dbg_wrote = Signal(); """debug: data is valid"""
+ self.dbg_wrote_phase = Signal(); """debug: the phase data was written"""
+ self.dbg_phase = Signal(); """debug: current phase"""
- def elaborate(self, _):
+ def elaborate(self, platform):
m = Module()
# depth and granularity
depth = 1 << self.addr_width
lvt_mem = Memory(width=self.we_width, depth=depth)
lvt_wr = lvt_mem.write_port(granularity=1)
lvt_rd = lvt_mem.read_port(transparent=self.transparent)
+ if not self.transparent:
+ # for some reason, formal proofs don't recognize the default
+ # reset value for this signal
+ m.d.comb += lvt_rd.en.eq(1)
m.submodules.lvt_wr = lvt_wr
m.submodules.lvt_rd = lvt_rd
# generate and wire the phases for the phased memories
lvt_rd.data[i],
mem1.rd_data_o.word_select(i, gran),
mem0.rd_data_o.word_select(i, gran)))
- # TODO create debug port and pass state downstream
- m.d.comb += [
- mem0.dbg_wrote.eq(0),
- mem1.dbg_wrote.eq(0),
- ]
+
+ if platform == "formal":
+ # pass upstream state to the memories, so they can ensure that
+ # their state are in sync with upstream, for induction
+ m.d.comb += [
+ # address and write lane under test
+ mem0.dbg_addr.eq(self.dbg_addr),
+ mem1.dbg_addr.eq(self.dbg_addr),
+ mem0.dbg_lane.eq(self.dbg_lane),
+ mem1.dbg_lane.eq(self.dbg_lane),
+ # upstream state
+ mem0.dbg_data.eq(self.dbg_data),
+ mem1.dbg_data.eq(self.dbg_data),
+ # the memory, on which the write ends up, depends on which
+ # phase it was written
+ mem0.dbg_wrote.eq(self.dbg_wrote & ~self.dbg_wrote_phase),
+ mem1.dbg_wrote.eq(self.dbg_wrote & self.dbg_wrote_phase),
+ ]
+ # sync phase to upstream
+ m.d.comb += Assert(self.dbg_phase == phase)
+ # this debug port for the LVT is an asynchronous read port,
+ # allowing direct access to a given memory location
+ # by the formal engine
+ m.submodules.dbgport = dbgport = lvt_mem.read_port(domain='comb')
+ # first, get the value stored in our memory location,
+ stored = Signal(self.we_width)
+ m.d.comb += dbgport.addr.eq(self.dbg_addr)
+ m.d.comb += stored.eq(dbgport.data)
+ # now, ensure that the value stored in memory is always in sync
+ # with the expected value (which memory the value was written to)
+ with m.If(self.dbg_wrote):
+ m.d.comb += Assert(stored.bit_select(self.dbg_lane, 1)
+ == self.dbg_wrote_phase)
return m
+ def ports(self):
+ return [
+ self.wr_addr_i,
+ self.wr_data_i,
+ self.wr_we_i,
+ self.rd_addr_i,
+ self.rd_data_o
+ ]
+
class DualPortRegfileTestCase(FHDLTestCase):
with self.subTest("transparent reads"):
self.do_test_dual_port_regfile(True)
- def test_dual_port_regfile_proof(self):
+ def do_test_dual_port_regfile_proof(self, transparent=True):
"""
Formal proof of the 1W/1R regfile
"""
m = Module()
# 128 x 32-bit, 8-bit granularity
- dut = DualPortRegfile(7, 32, 4, True)
+ dut = DualPortRegfile(7, 32, 4, transparent)
m.submodules.dut = dut
gran = dut.data_width // dut.we_width # granularity
# choose a single random memory location to test
a_const = AnyConst(dut.addr_width)
- # choose a single byte lane to test (one-hot encoding)
- we_mask = Signal(dut.we_width)
- # ... by first creating a random bit pattern
- we_const = AnyConst(dut.we_width)
- # ... and zeroing all but the first non-zero bit
- m.d.comb += we_mask.eq(we_const & (-we_const))
+ # choose a single byte lane to test
+ lane = AnyConst(range(dut.we_width))
# holding data register
d_reg = Signal(gran)
+ # keep track of the phase, so we can remember which memory
+ # we wrote to
+ phase = Signal()
+ m.d.sync += phase.eq(~phase)
# for some reason, simulated formal memory is not zeroed at reset
# ... so, remember whether we wrote it, at least once.
wrote = Signal()
+ # ... and on which phase it was written
+ wrote_phase = Signal()
# if our memory location and byte lane is being written,
# capture the data in our holding register
- with m.If((dut.wr_addr_i == a_const)):
- for i in range(dut.we_width):
- with m.If(we_mask[i] & dut.wr_we_i[i]):
- m.d.sync += d_reg.eq(
- dut.wr_data_i[i * gran:i * gran + gran])
- m.d.sync += wrote.eq(1)
+ with m.If((dut.wr_addr_i == a_const)
+ & dut.wr_we_i.bit_select(lane, 1)):
+ m.d.sync += d_reg.eq(dut.wr_data_i.word_select(lane, gran))
+ m.d.sync += wrote.eq(1)
+ m.d.sync += wrote_phase.eq(phase)
# if our memory location is being read,
# and the holding register has valid data,
# then its value must match the memory output, on the given lane
with m.If(Past(dut.rd_addr_i) == a_const):
- with m.If(wrote):
- for i in range(dut.we_width):
- rd_lane = dut.rd_data_o.word_select(i, gran)
- with m.If(we_mask[i]):
+ if transparent:
+ with m.If(wrote):
+ rd_lane = dut.rd_data_o.word_select(lane, gran)
+ m.d.sync += Assert(d_reg == rd_lane)
+ else:
+ # with a non-transparent read port, the read value depends
+ # on whether there is a simultaneous write, or not
+ with m.If(Past(dut.wr_addr_i) == a_const):
+ # simultaneous write -> check against last written value
+ with m.If(wrote & Past(wrote)):
+ rd_lane = dut.rd_data_o.word_select(lane, gran)
+ m.d.sync += Assert(Past(d_reg) == rd_lane)
+ with m.Else():
+ # otherwise, check against current written value
+ with m.If(wrote):
+ rd_lane = dut.rd_data_o.word_select(lane, gran)
m.d.sync += Assert(d_reg == rd_lane)
- self.assertFormal(m, mode="bmc", depth=10)
+ m.d.comb += [
+ dut.dbg_addr.eq(a_const),
+ dut.dbg_lane.eq(lane),
+ dut.dbg_data.eq(d_reg),
+ dut.dbg_wrote.eq(wrote),
+ dut.dbg_wrote_phase.eq(wrote_phase),
+ dut.dbg_phase.eq(phase),
+ ]
+
+ self.assertFormal(m, mode="prove", depth=3)
+
+ def test_dual_port_regfile_proof(self):
+ """
+ Formal check of 1W/1R regfile (transparent and not)
+ """
+ with self.subTest("transparent reads"):
+ self.do_test_dual_port_regfile_proof(True)
+ with self.subTest("non-transparent reads"):
+ self.do_test_dual_port_regfile_proof(False)
if __name__ == "__main__":