From: Luke Kenneth Casson Leighton <lkcl@lkcl.net>
Date: Fri, 7 Jun 2019 09:32:00 +0000 (+0100)
Subject: start preliminary test of load/store dependency matrices
X-Git-Tag: div_pipeline~1886
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=2b479fcb79b7989b86c8a30a5d33af9ceee33239;p=soc.git

start preliminary test of load/store dependency matrices
---

diff --git a/src/scoreboard/ldst_matrix.py b/src/scoreboard/ldst_matrix.py
index 30a946e0..e0209547 100644
--- a/src/scoreboard/ldst_matrix.py
+++ b/src/scoreboard/ldst_matrix.py
@@ -50,6 +50,7 @@ class LDSTDepMatrix(Elaboratable):
         self.ld_pend_i = Signal(n_ldst, reset_less=True)  # load pending in
         self.st_pend_i = Signal(n_ldst, reset_less=True)  # store pending in
         self.issue_i = Signal(n_ldst, reset_less=True) # Issue in
+        self.go_die_i = Signal(n_ldst, reset_less=True) # Die/Reset in
 
         self.load_hit_i = Signal(n_ldst, reset_less=True) # load hit in
         self.stwd_hit_i = Signal(n_ldst, reset_less=True) # store w/data hit in
@@ -76,6 +77,7 @@ class LDSTDepMatrix(Elaboratable):
         load_l = []
         stor_l = []
         issue_l = []
+        go_die_l = []
         lh_l = []
         sh_l = []
         for fu in range(self.n_ldst):
@@ -87,6 +89,7 @@ class LDSTDepMatrix(Elaboratable):
             load_l.append(dc.load_h_i)
             stor_l.append(dc.stor_h_i)
             issue_l.append(dc.issue_i)
+            go_die_l.append(dc.go_die_i)
 
             # load-hit and store-with-data-hit go in vertically (top)
             m.d.comb += [dc.load_hit_i.eq(self.load_hit_i),
@@ -97,6 +100,7 @@ class LDSTDepMatrix(Elaboratable):
         m.d.comb += [Cat(*load_l).eq(self.ld_pend_i),
                      Cat(*stor_l).eq(self.st_pend_i),
                      Cat(*issue_l).eq(self.issue_i),
+                     Cat(*go_die_l).eq(self.go_die_i),
                     ]
         # connect the load-hold-store / store-hold-load OR-accumulated outputs
         m.d.comb += self.ld_hold_st_o.eq(Cat(*lhs_l))
@@ -120,6 +124,7 @@ class LDSTDepMatrix(Elaboratable):
         yield self.ld_pend_i
         yield self.st_pend_i
         yield self.issue_i
+        yield self.go_die_i
         yield self.load_hit_i
         yield self.stwd_hit_i
         yield self.ld_hold_st_o
diff --git a/src/scoreboard/mem_fu_matrix.py b/src/scoreboard/mem_fu_matrix.py
index 83a6e219..dc88d358 100644
--- a/src/scoreboard/mem_fu_matrix.py
+++ b/src/scoreboard/mem_fu_matrix.py
@@ -23,8 +23,8 @@ class MemFUDepMatrix(Elaboratable):
         # Register "Global" vectors for determining RaW and WaR hazards
         self.ld_pend_i = Signal(n_reg_col, reset_less=True) # ld pending (top)
         self.st_pend_i = Signal(n_reg_col, reset_less=True) # st pending (top)
-        self.ld_rsel_o = Signal(n_reg_col, reset_less=True) # ld pending (bot)
-        self.st_rsel_o = Signal(n_reg_col, reset_less=True) # st pending (bot)
+        self.v_ld_rsel_o = Signal(n_reg_col, reset_less=True) # ld pending (bot)
+        self.v_st_rsel_o = Signal(n_reg_col, reset_less=True) # st pending (bot)
 
         self.issue_i = Signal(n_fu_row, reset_less=True)  # Issue in (top)
         self.go_ld_i = Signal(n_fu_row, reset_less=True)  # Go LOAD in (left)
@@ -139,8 +139,8 @@ class MemFUDepMatrix(Elaboratable):
         m.submodules.st_v = st_v
         m.submodules.ld_v = ld_v
 
-        m.d.comb += self.st_rsel_o.eq(st_v.g_pend_o)
-        m.d.comb += self.ld_rsel_o.eq(ld_v.g_pend_o)
+        m.d.comb += self.v_st_rsel_o.eq(st_v.g_pend_o)
+        m.d.comb += self.v_ld_rsel_o.eq(ld_v.g_pend_o)
 
         # ---
         # connect Dep issue_i/go_st_i/go_ld_i to module issue_i/go_rd/go_wr
diff --git a/src/scoreboard/test_mem_fu_matrix.py b/src/scoreboard/test_mem_fu_matrix.py
new file mode 100644
index 00000000..43cdf07f
--- /dev/null
+++ b/src/scoreboard/test_mem_fu_matrix.py
@@ -0,0 +1,652 @@
+from nmigen.compat.sim import run_simulation
+from nmigen.cli import verilog, rtlil
+from nmigen import Module, Const, Signal, Array, Cat, Elaboratable
+
+from regfile.regfile import RegFileArray, treereduce
+from scoreboard.ldst_matrix import LDSTDepMatrix
+from scoreboard.mem_fu_matrix import MemFUDepMatrix
+from scoreboard.global_pending import GlobalPending
+from scoreboard.group_picker import GroupPicker
+from scoreboard.issue_unit import IssueUnitGroup, IssueUnitArray, RegDecode
+from scoreboard.shadow import ShadowMatrix, BranchSpeculationRecord
+
+from nmutil.latch import SRLatch
+from nmutil.nmoperator import eq
+
+from random import randint, seed
+from copy import deepcopy
+from math import log
+
+
+class Memory(Elaboratable):
+    def __init__(self, regwid, addrw):
+        self.ddepth = regwid/8
+        depth = (1<<addrw) / self.ddepth
+        self.adr   = Signal(addrw)
+        self.dat_r = Signal(regwid)
+        self.dat_w = Signal(regwid)
+        self.we    = Signal()
+        self.mem   = Memory(width=regwid, depth=depth, init=range(0, depth))
+
+    def elaborate(self, platform):
+        m = Module()
+        m.submodules.rdport = rdport = self.mem.read_port()
+        m.submodules.wrport = wrport = self.mem.write_port()
+        m.d.comb += [
+            rdport.addr.eq(self.adr[self.ddepth:]), # ignore low bits
+            self.dat_r.eq(rdport.data),
+            wrport.addr.eq(self.adr),
+            wrport.data.eq(self.dat_w),
+            wrport.en.eq(self.we),
+        ]
+        return m
+
+
+class MemSim:
+    def __init__(self, regwid, addrw):
+        self.regwid = regwid
+        self.ddepth = regwid//8
+        depth = (1<<addrw) // self.ddepth
+        self.mem = list(range(0, depth))
+
+    def ld(self, addr):
+        return self.mem[addr>>self.ddepth]
+
+    def st(self, addr, data):
+        self.mem[addr>>self.ddepth] = data & ((1<<self.regwid)-1)
+
+
+class MemFunctionUnits(Elaboratable):
+
+    def __init__(self, n_int_alus):
+        self.n_int_alus = n_int_alus
+
+        self.ld_i = Signal(n_int_alus, reset_less=True) # Dest R# in
+        self.st_i = Signal(n_int_alus, reset_less=True) # oper1 R# in
+
+        self.load_hit_i = Signal(n_int_alus, reset_less=True) # Load Hit
+        self.stwd_hit_i = Signal(n_int_alus, reset_less=True) # Store Hit
+
+        self.g_int_st_pend_o = Signal(n_int_alus, reset_less=True)
+        self.g_int_ld_pend_o = Signal(n_int_alus, reset_less=True)
+
+        self.ld_rsel_o = Signal(n_int_alus, reset_less=True) # dest reg (bot)
+        self.st_rsel_o = Signal(n_int_alus, reset_less=True) # src1 reg (bot)
+
+        self.req_rel_i = Signal(n_int_alus, reset_less = True)
+        self.ld_hold_st_o = Signal(n_int_alus, reset_less=True)
+        self.st_hold_ld_o = Signal(n_int_alus, reset_less=True)
+
+        self.go_st_i = Signal(n_int_alus, reset_less=True)
+        self.go_ld_i = Signal(n_int_alus, reset_less=True)
+        self.go_die_i = Signal(n_int_alus, reset_less=True)
+        self.req_rel_o = Signal(n_int_alus, reset_less=True)
+        self.fn_issue_i = Signal(n_int_alus, reset_less=True)
+
+        # Note: FURegs ld_pend_o is also outputted from here, for use in WaWGrid
+
+    def elaborate(self, platform):
+        m = Module()
+        comb = m.d.comb
+        sync = m.d.sync
+
+        n_intfus = self.n_int_alus
+
+        # Integer FU-FU Dep Matrix
+        ldstdeps = LDSTDepMatrix(n_intfus)
+        m.submodules.ldstdeps = ldstdeps
+        # Integer FU-Reg Dep Matrix
+        memfudeps = MemFUDepMatrix(n_intfus, n_intfus)
+        m.submodules.memfudeps = memfudeps
+
+        comb += self.g_int_st_pend_o.eq(memfudeps.v_st_rsel_o)
+        comb += self.g_int_ld_pend_o.eq(memfudeps.v_ld_rsel_o)
+
+        comb += memfudeps.st_pend_i.eq(memfudeps.v_st_rsel_o)
+        comb += memfudeps.ld_pend_i.eq(memfudeps.v_ld_rsel_o)
+
+        comb += ldstdeps.st_pend_i.eq(memfudeps.st_pend_o)
+        comb += ldstdeps.ld_pend_i.eq(memfudeps.ld_pend_o)
+        self.ld_pend_o = memfudeps.ld_pend_o # also output for use in WaWGrid
+
+        comb += ldstdeps.issue_i.eq(self.fn_issue_i)
+        comb += ldstdeps.load_hit_i.eq(self.load_hit_i)
+        comb += ldstdeps.stwd_hit_i.eq(self.stwd_hit_i)
+        comb += ldstdeps.go_die_i.eq(self.go_die_i)
+        comb += self.ld_hold_st_o.eq(ldstdeps.ld_hold_st_o)
+        comb += self.st_hold_ld_o.eq(ldstdeps.st_hold_ld_o)
+
+        # Connect function issue / arrays, and dest/src1/src2
+        comb += memfudeps.ld_i.eq(self.ld_i)
+        comb += memfudeps.st_i.eq(self.st_i)
+
+        comb += memfudeps.go_st_i.eq(self.go_st_i)
+        comb += memfudeps.go_ld_i.eq(self.go_ld_i)
+        comb += memfudeps.go_die_i.eq(self.go_die_i)
+        comb += memfudeps.issue_i.eq(self.fn_issue_i)
+
+        comb += self.ld_rsel_o.eq(memfudeps.ld_rsel_o)
+        comb += self.st_rsel_o.eq(memfudeps.st_rsel_o)
+
+        return m
+
+    def __iter__(self):
+        yield self.ld_i
+        yield self.st_i
+        yield self.g_int_st_pend_o
+        yield self.g_int_ld_pend_o
+        yield self.ld_rsel_o
+        yield self.st_rsel_o
+        yield self.req_rel_i
+        yield self.ld_hold_st_o
+        yield self.st_hold_ld_o
+        yield self.load_hit_i
+        yield self.stwd_hit_i
+        yield self.go_st_i
+        yield self.go_ld_i
+        yield self.go_die_i
+        yield self.req_rel_o
+        yield self.fn_issue_i
+
+    def ports(self):
+        return list(self)
+
+
+class Scoreboard(Elaboratable):
+    def __init__(self, rwid, n_regs):
+        """ Inputs:
+
+            * :rwid:   bit width of register file(s) - both FP and INT
+            * :n_regs: depth of register file(s) - number of FP and INT regs
+        """
+        self.rwid = rwid
+        self.n_regs = n_regs
+
+        # Register Files
+        self.intregs = RegFileArray(rwid, n_regs)
+        self.fpregs = RegFileArray(rwid, n_regs)
+
+        # issue q needs to get at these
+        self.aluissue = IssueUnitGroup(4)
+        self.brissue = IssueUnitGroup(1)
+        # and these
+        self.alu_oper_i = Signal(4, reset_less=True)
+        self.alu_imm_i = Signal(rwid, reset_less=True)
+        self.br_oper_i = Signal(4, reset_less=True)
+        self.br_imm_i = Signal(rwid, reset_less=True)
+
+        # inputs
+        self.int_dest_i = Signal(max=n_regs, reset_less=True) # Dest R# in
+        self.int_src1_i = Signal(max=n_regs, reset_less=True) # oper1 R# in
+        self.int_src2_i = Signal(max=n_regs, reset_less=True) # oper2 R# in
+        self.reg_enable_i = Signal(reset_less=True) # enable reg decode
+
+        # outputs
+        self.issue_o = Signal(reset_less=True) # instruction was accepted
+        self.busy_o = Signal(reset_less=True) # at least one CU is busy
+
+        # for branch speculation experiment.  branch_direction = 0 if
+        # the branch hasn't been met yet.  1 indicates "success", 2 is "fail"
+        # branch_succ and branch_fail are requests to have the current
+        # instruction be dependent on the branch unit "shadow" capability.
+        self.branch_succ_i = Signal(reset_less=True)
+        self.branch_fail_i = Signal(reset_less=True)
+        self.branch_direction_o = Signal(2, reset_less=True)
+
+    def elaborate(self, platform):
+        m = Module()
+        comb = m.d.comb
+        sync = m.d.sync
+
+        m.submodules.intregs = self.intregs
+        m.submodules.fpregs = self.fpregs
+
+        # register ports
+        int_dest = self.intregs.write_port("dest")
+        int_src1 = self.intregs.read_port("src1")
+        int_src2 = self.intregs.read_port("src2")
+
+        fp_dest = self.fpregs.write_port("dest")
+        fp_src1 = self.fpregs.read_port("src1")
+        fp_src2 = self.fpregs.read_port("src2")
+
+        # Int ALUs and Comp Units
+        n_int_alus = 5
+        cua = CompUnitALUs(self.rwid, 3)
+        cub = CompUnitBR(self.rwid, 3)
+        m.submodules.cu = cu = CompUnitsBase(self.rwid, [cua, cub])
+        bgt = cub.bgt # get at the branch computation unit
+        br1 = cub.br1
+
+        # Int FUs
+        m.submodules.intfus = intfus = FunctionUnits(self.n_regs, n_int_alus)
+
+        # Count of number of FUs
+        n_intfus = n_int_alus
+        n_fp_fus = 0 # for now
+
+        # Integer Priority Picker 1: Adder + Subtractor
+        intpick1 = GroupPicker(n_intfus) # picks between add, sub, mul and shf
+        m.submodules.intpick1 = intpick1
+
+        # INT/FP Issue Unit
+        regdecode = RegDecode(self.n_regs)
+        m.submodules.regdecode = regdecode
+        issueunit = IssueUnitArray([self.aluissue, self.brissue])
+        m.submodules.issueunit = issueunit
+
+        # Shadow Matrix.  currently n_intfus shadows, to be used for
+        # write-after-write hazards.  NOTE: there is one extra for branches,
+        # so the shadow width is increased by 1
+        m.submodules.shadows = shadows = ShadowMatrix(n_intfus, n_intfus, True)
+        m.submodules.bshadow = bshadow = ShadowMatrix(n_intfus, 1, False)
+
+        # record previous instruction to cast shadow on current instruction
+        prev_shadow = Signal(n_intfus)
+
+        # Branch Speculation recorder.  tracks the success/fail state as
+        # each instruction is issued, so that when the branch occurs the
+        # allow/cancel can be issued as appropriate.
+        m.submodules.specrec = bspec = BranchSpeculationRecord(n_intfus)
+
+        #---------
+        # ok start wiring things together...
+        # "now hear de word of de looord... dem bones dem bones dem dryy bones"
+        # https://www.youtube.com/watch?v=pYb8Wm6-QfA
+        #---------
+
+        #---------
+        # Issue Unit is where it starts.  set up some in/outs for this module
+        #---------
+        comb += [    regdecode.dest_i.eq(self.int_dest_i),
+                     regdecode.src1_i.eq(self.int_src1_i),
+                     regdecode.src2_i.eq(self.int_src2_i),
+                     regdecode.enable_i.eq(self.reg_enable_i),
+                     self.issue_o.eq(issueunit.issue_o)
+                    ]
+
+        # take these to outside (issue needs them)
+        comb += cua.oper_i.eq(self.alu_oper_i)
+        comb += cua.imm_i.eq(self.alu_imm_i)
+        comb += cub.oper_i.eq(self.br_oper_i)
+        comb += cub.imm_i.eq(self.br_imm_i)
+
+        # TODO: issueunit.f (FP)
+
+        # and int function issue / busy arrays, and dest/src1/src2
+        comb += intfus.dest_i.eq(regdecode.dest_o)
+        comb += intfus.src1_i.eq(regdecode.src1_o)
+        comb += intfus.src2_i.eq(regdecode.src2_o)
+
+        fn_issue_o = issueunit.fn_issue_o
+
+        comb += intfus.fn_issue_i.eq(fn_issue_o)
+        comb += issueunit.busy_i.eq(cu.busy_o)
+        comb += self.busy_o.eq(cu.busy_o.bool())
+
+        #---------
+        # merge shadow matrices outputs
+        #---------
+
+        # these are explained in ShadowMatrix docstring, and are to be
+        # connected to the FUReg and FUFU Matrices, to get them to reset
+        anydie = Signal(n_intfus, reset_less=True)
+        allshadown = Signal(n_intfus, reset_less=True)
+        shreset = Signal(n_intfus, reset_less=True)
+        comb += allshadown.eq(shadows.shadown_o & bshadow.shadown_o)
+        comb += anydie.eq(shadows.go_die_o | bshadow.go_die_o)
+        comb += shreset.eq(bspec.match_g_o | bspec.match_f_o)
+
+        #---------
+        # connect fu-fu matrix
+        #---------
+
+        # Group Picker... done manually for now.
+        go_rd_o = intpick1.go_rd_o
+        go_wr_o = intpick1.go_wr_o
+        go_rd_i = intfus.go_rd_i
+        go_wr_i = intfus.go_wr_i
+        go_die_i = intfus.go_die_i
+        # NOTE: connect to the shadowed versions so that they can "die" (reset)
+        comb += go_rd_i[0:n_intfus].eq(go_rd_o[0:n_intfus]) # rd
+        comb += go_wr_i[0:n_intfus].eq(go_wr_o[0:n_intfus]) # wr
+        comb += go_die_i[0:n_intfus].eq(anydie[0:n_intfus]) # die
+
+        # Connect Picker
+        #---------
+        comb += intpick1.rd_rel_i[0:n_intfus].eq(cu.rd_rel_o[0:n_intfus])
+        comb += intpick1.req_rel_i[0:n_intfus].eq(cu.req_rel_o[0:n_intfus])
+        int_rd_o = intfus.readable_o
+        int_wr_o = intfus.writable_o
+        comb += intpick1.readable_i[0:n_intfus].eq(int_rd_o[0:n_intfus])
+        comb += intpick1.writable_i[0:n_intfus].eq(int_wr_o[0:n_intfus])
+
+        #---------
+        # Shadow Matrix
+        #---------
+
+        comb += shadows.issue_i.eq(fn_issue_o)
+        #comb += shadows.reset_i[0:n_intfus].eq(bshadow.go_die_o[0:n_intfus])
+        comb += shadows.reset_i[0:n_intfus].eq(bshadow.go_die_o[0:n_intfus])
+        #---------
+        # NOTE; this setup is for the instruction order preservation...
+
+        # connect shadows / go_dies to Computation Units
+        comb += cu.shadown_i[0:n_intfus].eq(allshadown)
+        comb += cu.go_die_i[0:n_intfus].eq(anydie)
+
+        # ok connect first n_int_fu shadows to busy lines, to create an
+        # instruction-order linked-list-like arrangement, using a bit-matrix
+        # (instead of e.g. a ring buffer).
+        # XXX TODO
+
+        # when written, the shadow can be cancelled (and was good)
+        for i in range(n_intfus):
+            comb += shadows.s_good_i[i][0:n_intfus].eq(go_wr_o[0:n_intfus])
+
+        # *previous* instruction shadows *current* instruction, and, obviously,
+        # if the previous is completed (!busy) don't cast the shadow!
+        comb += prev_shadow.eq(~fn_issue_o & cu.busy_o)
+        for i in range(n_intfus):
+            comb += shadows.shadow_i[i][0:n_intfus].eq(prev_shadow)
+
+        #---------
+        # ... and this is for branch speculation.  it uses the extra bit
+        # tacked onto the ShadowMatrix (hence shadow_wid=n_intfus+1)
+        # only needs to set shadow_i, s_fail_i and s_good_i
+
+        # issue captures shadow_i (if enabled)
+        comb += bshadow.reset_i[0:n_intfus].eq(shreset[0:n_intfus])
+
+        bactive = Signal(reset_less=True)
+        comb += bactive.eq((bspec.active_i | br1.issue_i) & ~br1.go_wr_i)
+
+        # instruction being issued (fn_issue_o) has a shadow cast by the branch
+        with m.If(bactive & (self.branch_succ_i | self.branch_fail_i)):
+            comb += bshadow.issue_i.eq(fn_issue_o)
+            for i in range(n_intfus):
+                with m.If(fn_issue_o & (Const(1<<i))):
+                    comb += bshadow.shadow_i[i][0].eq(1)
+
+        # finally, we need an indicator to the test infrastructure as to
+        # whether the branch succeeded or failed, plus, link up to the
+        # "recorder" of whether the instruction was under shadow or not
+
+        with m.If(br1.issue_i):
+            sync += bspec.active_i.eq(1)
+        with m.If(self.branch_succ_i):
+            comb += bspec.good_i.eq(fn_issue_o & 0x1f)
+        with m.If(self.branch_fail_i):
+            comb += bspec.fail_i.eq(fn_issue_o & 0x1f)
+
+        # branch is active (TODO: a better signal: this is over-using the
+        # go_write signal - actually the branch should not be "writing")
+        with m.If(br1.go_wr_i):
+            sync += self.branch_direction_o.eq(br1.data_o+Const(1, 2))
+            sync += bspec.active_i.eq(0)
+            comb += bspec.br_i.eq(1)
+            # branch occurs if data == 1, failed if data == 0
+            comb += bspec.br_ok_i.eq(br1.data_o == 1)
+            for i in range(n_intfus):
+                # *expected* direction of the branch matched against *actual*
+                comb += bshadow.s_good_i[i][0].eq(bspec.match_g_o[i])
+                # ... or it didn't
+                comb += bshadow.s_fail_i[i][0].eq(bspec.match_f_o[i])
+
+        #---------
+        # Connect Register File(s)
+        #---------
+        comb += int_dest.wen.eq(intfus.dest_rsel_o)
+        comb += int_src1.ren.eq(intfus.src1_rsel_o)
+        comb += int_src2.ren.eq(intfus.src2_rsel_o)
+
+        # connect ALUs to regfule
+        comb += int_dest.data_i.eq(cu.data_o)
+        comb += cu.src1_i.eq(int_src1.data_o)
+        comb += cu.src2_i.eq(int_src2.data_o)
+
+        # connect ALU Computation Units
+        comb += cu.go_rd_i[0:n_intfus].eq(go_rd_o[0:n_intfus])
+        comb += cu.go_wr_i[0:n_intfus].eq(go_wr_o[0:n_intfus])
+        comb += cu.issue_i[0:n_intfus].eq(fn_issue_o[0:n_intfus])
+
+        return m
+
+    def __iter__(self):
+        yield from self.intregs
+        yield from self.fpregs
+        yield self.int_dest_i
+        yield self.int_src1_i
+        yield self.int_src2_i
+        yield self.issue_o
+        yield self.branch_succ_i
+        yield self.branch_fail_i
+        yield self.branch_direction_o
+
+    def ports(self):
+        return list(self)
+
+
+
+
+def int_instr(dut, op, imm, src1, src2, dest, branch_success, branch_fail):
+    yield from disable_issue(dut)
+    yield dut.int_dest_i.eq(dest)
+    yield dut.int_src1_i.eq(src1)
+    yield dut.int_src2_i.eq(src2)
+    if (op & (0x3<<2)) != 0: # branch
+        yield dut.brissue.insn_i.eq(1)
+        yield dut.br_oper_i.eq(Const(op & 0x3, 2))
+        yield dut.br_imm_i.eq(imm)
+        dut_issue = dut.brissue
+    else:
+        yield dut.aluissue.insn_i.eq(1)
+        yield dut.alu_oper_i.eq(Const(op & 0x3, 2))
+        yield dut.alu_imm_i.eq(imm)
+        dut_issue = dut.aluissue
+    yield dut.reg_enable_i.eq(1)
+
+    # these indicate that the instruction is to be made shadow-dependent on
+    # (either) branch success or branch fail
+    yield dut.branch_fail_i.eq(branch_fail)
+    yield dut.branch_succ_i.eq(branch_success)
+
+    yield
+    yield from wait_for_issue(dut, dut_issue)
+
+
+def print_reg(dut, rnums):
+    rs = []
+    for rnum in rnums:
+        reg = yield dut.intregs.regs[rnum].reg
+        rs.append("%x" % reg)
+    rnums = map(str, rnums)
+    print ("reg %s: %s" % (','.join(rnums), ','.join(rs)))
+
+
+def create_random_ops(dut, n_ops, shadowing=False, max_opnums=3):
+    insts = []
+    for i in range(n_ops):
+        src1 = randint(1, dut.n_regs-1)
+        src2 = randint(1, dut.n_regs-1)
+        imm = randint(1, (1<<dut.rwid)-1)
+        dest = randint(1, dut.n_regs-1)
+        op = randint(0, max_opnums)
+        opi = 0 if randint(0, 2) else 1 # set true if random is nonzero
+
+        if shadowing:
+            insts.append((src1, src2, dest, op, opi, imm, (0, 0)))
+        else:
+            insts.append((src1, src2, dest, op, opi, imm))
+    return insts
+
+
+
+def scoreboard_sim(dut, alusim):
+
+    seed(0)
+
+    for i in range(50):
+
+        # set random values in the registers
+        for i in range(1, dut.n_regs):
+            val = randint(0, (1<<alusim.rwidth)-1)
+            #val = 31+i*3
+            #val = i
+            yield dut.intregs.regs[i].reg.eq(val)
+            alusim.setval(i, val)
+
+        # create some instructions (some random, some regression tests)
+        instrs = []
+        if True:
+            instrs = create_random_ops(dut, 15, True, 4)
+
+        if False:
+            instrs.append( (1, 2, 2, 1, 1, 20, (0, 0)) )
+
+        if False:
+            instrs.append( (7, 3, 2, 4, (0, 0)) )
+            instrs.append( (7, 6, 6, 2, (0, 0)) )
+            instrs.append( (1, 7, 2, 2, (0, 0)) )
+
+        if False:
+            instrs.append((2, 3, 3, 0, 0, 0, (0, 0)))
+            instrs.append((5, 3, 3, 1, 0, 0, (0, 0)))
+            instrs.append((3, 5, 5, 2, 0, 0, (0, 0)))
+            instrs.append((5, 3, 3, 3, 0, 0, (0, 0)))
+            instrs.append((3, 5, 5, 0, 0, 0, (0, 0)))
+
+        if False:
+            instrs.append( (3, 3, 4, 0, 0, 13979, (0, 0)))
+            instrs.append( (6, 4, 1, 2, 0, 40976, (0, 0)))
+            instrs.append( (1, 4, 7, 4, 1, 23652, (0, 0)))
+
+        if False:
+            instrs.append((5, 6, 2, 1))
+            instrs.append((2, 2, 4, 0))
+            #instrs.append((2, 2, 3, 1))
+
+        if False:
+            instrs.append((2, 1, 2, 3))
+
+        if False:
+            instrs.append((2, 6, 2, 1))
+            instrs.append((2, 1, 2, 0))
+
+        if False:
+            instrs.append((1, 2, 7, 2))
+            instrs.append((7, 1, 5, 0))
+            instrs.append((4, 4, 1, 1))
+
+        if False:
+            instrs.append((5, 6, 2, 2))
+            instrs.append((1, 1, 4, 1))
+            instrs.append((6, 5, 3, 0))
+
+        if False:
+            # Write-after-Write Hazard
+            instrs.append( (3, 6, 7, 2) )
+            instrs.append( (4, 4, 7, 1) )
+
+        if False:
+            # self-read/write-after-write followed by Read-after-Write
+            instrs.append((1, 1, 1, 1))
+            instrs.append((1, 5, 3, 0))
+
+        if False:
+            # Read-after-Write followed by self-read-after-write
+            instrs.append((5, 6, 1, 2))
+            instrs.append((1, 1, 1, 1))
+
+        if False:
+            # self-read-write sandwich
+            instrs.append((5, 6, 1, 2))
+            instrs.append((1, 1, 1, 1))
+            instrs.append((1, 5, 3, 0))
+
+        if False:
+            # very weird failure
+            instrs.append( (5, 2, 5, 2) )
+            instrs.append( (2, 6, 3, 0) )
+            instrs.append( (4, 2, 2, 1) )
+
+        if False:
+            v1 = 4
+            yield dut.intregs.regs[5].reg.eq(v1)
+            alusim.setval(5, v1)
+            yield dut.intregs.regs[3].reg.eq(5)
+            alusim.setval(3, 5)
+            instrs.append((5, 3, 3, 4, (0, 0)))
+            instrs.append((4, 2, 1, 2, (0, 1)))
+
+        if False:
+            v1 = 6
+            yield dut.intregs.regs[5].reg.eq(v1)
+            alusim.setval(5, v1)
+            yield dut.intregs.regs[3].reg.eq(5)
+            alusim.setval(3, 5)
+            instrs.append((5, 3, 3, 4, (0, 0)))
+            instrs.append((4, 2, 1, 2, (1, 0)))
+
+        if False:
+            instrs.append( (4, 3, 5, 1, 0, (0, 0)) )
+            instrs.append( (5, 2, 3, 1, 0, (0, 0)) )
+            instrs.append( (7, 1, 5, 2, 0, (0, 0)) )
+            instrs.append( (5, 6, 6, 4, 0, (0, 0)) )
+            instrs.append( (7, 5, 2, 2, 0, (1, 0)) )
+            instrs.append( (1, 7, 5, 0, 0, (0, 1)) )
+            instrs.append( (1, 6, 1, 2, 0, (1, 0)) )
+            instrs.append( (1, 6, 7, 3, 0, (0, 0)) )
+            instrs.append( (6, 7, 7, 0, 0, (0, 0)) )
+
+        # issue instruction(s), wait for issue to be free before proceeding
+        for i, instr in enumerate(instrs):
+            src1, src2, dest, op, opi, imm, (br_ok, br_fail) = instr
+
+            print ("instr %d: (%d, %d, %d, %d, %d, %d)" % \
+                    (i, src1, src2, dest, op, opi, imm))
+            alusim.op(op, opi, imm, src1, src2, dest)
+            yield from instr_q(dut, op, opi, imm, src1, src2, dest,
+                               br_ok, br_fail)
+
+        # wait for all instructions to stop before checking
+        while True:
+            iqlen = yield dut.qlen_o
+            if iqlen == 0:
+                break
+            yield
+        yield
+        yield
+        yield
+        yield
+        yield from wait_for_busy_clear(dut)
+
+        # check status
+        yield from alusim.check(dut)
+        yield from alusim.dump(dut)
+
+
+def test_scoreboard():
+    dut = IssueToScoreboard(2, 1, 1, 16, 8, 8)
+    alusim = RegSim(16, 8)
+    memsim = MemSim(16, 16)
+    vl = rtlil.convert(dut, ports=dut.ports())
+    with open("test_scoreboard6600.il", "w") as f:
+        f.write(vl)
+
+    run_simulation(dut, scoreboard_sim(dut, alusim),
+                        vcd_name='test_scoreboard6600.vcd')
+
+    #run_simulation(dut, scoreboard_branch_sim(dut, alusim),
+    #                    vcd_name='test_scoreboard6600.vcd')
+
+
+def test_mem_fus():
+    dut = MemFunctionUnits(4)
+    vl = rtlil.convert(dut, ports=dut.ports())
+    with open("test_mem_fus.il", "w") as f:
+        f.write(vl)
+
+
+if __name__ == '__main__':
+    test_mem_fus()