-# Proof of correctness for partitioned equal signal combiner
+# Proof of correctness for Condition Register pipeline
# Copyright (C) 2020 Michael Nolan <mtnolan2640@gmail.com>
"""
Links:
recwidth += width
comb += p.eq(AnyConst(width))
- pspec = ALUPipeSpec(id_wid=2, op_wid=recwidth)
+ pspec = ALUPipeSpec(id_wid=2)
m.submodules.dut = dut = CRMainStage(pspec)
+ full_cr_in = Signal(32)
+ cr_a_in = Signal(4)
+
+ cr_o = Signal(32)
+
a = dut.i.a
- cr = dut.i.cr
- cr_o = dut.o.cr
- o = dut.o.o
+ b = dut.i.b
+ cr = full_cr_in
+ full_cr_out = dut.o.full_cr.data
+ o = dut.o.o.data
# setup random inputs
comb += [a.eq(AnyConst(64)),
- cr.eq(AnyConst(64))]
+ b.eq(AnyConst(64)),
+ cr_a_in.eq(AnyConst(4)),
+ full_cr_in.eq(AnyConst(32))]
+
+ a_fields = dut.fields.FormA
+ xl_fields = dut.fields.FormXL
+ xfx_fields = dut.fields.FormXFX
+
+ # I'd like to be able to prove this module using the proof
+ # written before I made the change to use 4 bit cr inputs for
+ # OP_MCRF and OP_CROP. So I'm going to set up the machinery to
+ # let me do that here
+
+ cr_input_arr = Array([full_cr_in[(7-i)*4:(7-i)*4+4] for i in range(8)])
+ cr_output_arr = Array([cr_o[(7-i)*4:(7-i)*4+4] for i in range(8)])
+
+ with m.Switch(rec.insn_type):
+ # CR_ISEL takes cr_a
+ with m.Case(InternalOp.OP_ISEL):
+ # grab the MSBs of the cr bit selector
+ bc = Signal(3, reset_less=True)
+ comb += bc.eq(a_fields.BC[2:5])
+
+ # Use the MSBs to select which CR register to feed
+ # into cr_a
+ comb += dut.i.cr_a.eq(cr_input_arr[bc])
+
+ # For OP_CROP, we need to input the corresponding CR
+ # registers for BA, BB, and BT
+ with m.Case(InternalOp.OP_CROP):
+ # grab the MSBs of the 3 bit selectors
+ bt = Signal(3, reset_less=True)
+ ba = Signal(3, reset_less=True)
+ bb = Signal(3, reset_less=True)
+ comb += bt.eq(xl_fields.BT[2:5])
+ comb += ba.eq(xl_fields.BA[2:5])
+ comb += bb.eq(xl_fields.BB[2:5])
+
+ # Grab the cr register containing the bit from BA, BB,
+ # and BT, and feed it to the cr inputs
+ comb += dut.i.cr_a.eq(cr_input_arr[ba])
+ comb += dut.i.cr_b.eq(cr_input_arr[bb])
+ comb += dut.i.cr_c.eq(cr_input_arr[bt])
+
+ # Insert the output into the output CR register so the
+ # proof below can use it
+ for i in range(8):
+ with m.If(i != bt):
+ comb += cr_output_arr[i].eq(cr_input_arr[i])
+ with m.Else():
+ comb += cr_output_arr[i].eq(dut.o.cr_o.data)
+
+ with m.Case(InternalOp.OP_MCRF):
+ # This does a similar thing to OP_CROP above, with
+ # less inputs. The CR selection fields are already 3
+ # bits so there's no need to grab only the MSBs
+ bf = Signal(xl_fields.BF[0:-1].shape())
+ bfa = Signal(xl_fields.BFA[0:-1].shape())
+ comb += bf.eq(xl_fields.BF[0:-1])
+ comb += bfa.eq(xl_fields.BFA[0:-1])
+
+ # set cr_a to the CR selected by BFA
+ comb += dut.i.cr_a.eq(cr_input_arr[bfa])
+ for i in range(8):
+ # Similar to above, insert the result cr back into
+ # the full cr register so the proof below can use
+ # it
+ with m.If(i != bf):
+ comb += cr_output_arr[i].eq(cr_input_arr[i])
+ with m.Else():
+ comb += cr_output_arr[i].eq(dut.o.cr_o.data)
+
+ # For the other two, they take the full CR as input, and
+ # output a full CR. This handles that
+ with m.Default():
+ comb += dut.i.full_cr.eq(full_cr_in)
+ comb += cr_o.eq(full_cr_out)
comb += dut.i.ctx.op.eq(rec)
+ # test signals for output conditions. these must only be enabled for
+ # specific instructions, indicating that they generated the output.
+ # this is critically important because the "ok" signals are used by
+ # MultiCompUnit to request a write to the regfile.
+ o_ok = Signal()
+ cr_o_ok = Signal()
+ full_cr_o_ok = Signal()
+
# Assert that op gets copied from the input to output
for rec_sig in rec.ports():
name = rec_sig.name
cr_arr = Array([cr[31-i] for i in range(32)])
cr_o_arr = Array([cr_o[31-i] for i in range(32)])
- xl_fields = dut.fields.FormXL
- xfx_fields = dut.fields.FormXFX
FXM = xfx_fields.FXM[0:-1]
with m.Switch(rec.insn_type):
with m.Case(InternalOp.OP_MTCRF):
for i in range(8):
with m.If(FXM[i]):
comb += Assert(cr_o[4*i:4*i+4] == a[4*i:4*i+4])
+ comb += full_cr_o_ok.eq(1)
+
with m.Case(InternalOp.OP_MFCR):
with m.If(rec.insn[20]): # mfocrf
for i in range(8):
comb += Assert(o[4*i:4*i+4] == 0)
with m.Else(): # mfcrf
comb += Assert(o == cr)
+ comb += o_ok.eq(1)
+
+ with m.Case(InternalOp.OP_MCRF):
+ BF = xl_fields.BF[0:-1]
+ BFA = xl_fields.BFA[0:-1]
+ for i in range(4):
+ comb += Assert(cr_o_arr[BF*4+i] == cr_arr[BFA*4+i])
+ for i in range(8):
+ with m.If(BF != 7-i):
+ comb += Assert(cr_o[i*4:i*4+4] == cr[i*4:i*4+4])
+ comb += cr_o_ok.eq(1)
+
with m.Case(InternalOp.OP_CROP):
bt = Signal(xl_fields.BT[0:-1].shape(), reset_less=True)
ba = Signal(xl_fields.BA[0:-1].shape(), reset_less=True)
with m.If(lut == 0b0110):
comb += Assert(bit_o == bit_a ^ bit_b)
+ comb += cr_o_ok.eq(1)
+
+ with m.Case(InternalOp.OP_ISEL):
+ # Extract the bit selector of the CR
+ bc = Signal(a_fields.BC[0:-1].shape(), reset_less=True)
+ comb += bc.eq(a_fields.BC[0:-1])
+
+ # Extract the bit from CR
+ cr_bit = Signal(reset_less=True)
+ comb += cr_bit.eq(cr_arr[bc])
+
+ # select a or b as output
+ comb += Assert(o == Mux(cr_bit, a, b))
+ comb += o_ok.eq(1)
+
+ # check that data ok was only enabled when op actioned
+ comb += Assert(dut.o.o.ok == o_ok)
+ comb += Assert(dut.o.cr_o.ok == cr_o_ok)
+ comb += Assert(dut.o.full_cr.ok == full_cr_o_ok)
+
return m
projects / soc.git / blobdiff