src/scoreboard/shadow.py

   1 from nmigen.compat.sim import run_simulation
   2 from nmigen.cli import verilog, rtlil
   3 from nmigen import Module, Signal, Cat, Array, Const, Elaboratable
   4 from nmigen.lib.coding import Decoder
   5
   6 from nmutil.latch import SRLatch, latchregister
   7
   8 from scoreboard.shadow_fn import ShadowFn
   9
  10
  11 class Shadow(Elaboratable):
  12     """ implements shadowing 11.5.1, p55
  13
  14         shadowing can be used for branches as well as exceptions (interrupts),
  15         load/store hold (exceptions again), and vector-element predication
  16         (once the predicate is known, which it may not be at instruction issue)
  17
  18         Inputs
  19         * :shadow_wid:  number of shadow/fail/good/go_die sets
  20
  21         notes:
  22         * when shadow_wid = 0, recover and shadown are Consts (i.e. do nothing)
  23     """
  24     def __init__(self, shadow_wid=0):
  25         self.shadow_wid = shadow_wid
  26
  27         if shadow_wid:
  28             self.issue_i = Signal(reset_less=True)
  29             self.shadow_i = Signal(shadow_wid, reset_less=True)
  30             self.s_fail_i = Signal(shadow_wid, reset_less=True)
  31             self.s_good_i = Signal(shadow_wid, reset_less=True)
  32             self.go_die_o = Signal(reset_less=True)
  33             self.shadown_o = Signal(reset_less=True)
  34         else:
  35             self.shadown_o = Const(1)
  36             self.go_die_o = Const(0)
  37
  38     def elaborate(self, platform):
  39         m = Module()
  40         s_latches = []
  41         for i in range(self.shadow_wid):
  42             sh = ShadowFn()
  43             setattr(m.submodules, "shadow%d" % i, sh)
  44             s_latches.append(sh)
  45
  46         # shadow / recover (optional: shadow_wid > 0)
  47         if self.shadow_wid:
  48             i_l = []
  49             fail_l = []
  50             good_l = []
  51             shi_l = []
  52             sho_l = []
  53             rec_l = []
  54             # get list of latch signals. really must be a better way to do this
  55             for l in s_latches:
  56                 i_l.append(l.issue_i)
  57                 shi_l.append(l.shadow_i)
  58                 fail_l.append(l.s_fail_i)
  59                 good_l.append(l.s_good_i)
  60                 sho_l.append(l.shadow_o)
  61                 rec_l.append(l.recover_o)
  62             m.d.comb += Cat(*i_l).eq(self.issue_i)
  63             m.d.comb += Cat(*fail_l).eq(self.s_fail_i)
  64             m.d.comb += Cat(*good_l).eq(self.s_good_i)
  65             m.d.comb += Cat(*shi_l).eq(self.shadow_i)
  66             m.d.comb += self.shadown_o.eq(~(Cat(*sho_l).bool()))
  67             m.d.comb += self.go_die_o.eq(Cat(*rec_l).bool())
  68
  69         return m
  70
  71     def __iter__(self):
  72         if self.shadow_wid:
  73             yield self.issue_i
  74             yield self.shadow_i
  75             yield self.s_fail_i
  76             yield self.s_good_i
  77         yield self.go_die_o
  78         yield self.shadown_o
  79
  80     def ports(self):
  81         return list(self)
  82
  83
  84 class ShadowMatrix(Elaboratable):
  85     """ Matrix of Shadow Functions.  One per FU.
  86
  87         Inputs
  88         * :n_fus:       register file width
  89         * :shadow_wid:  number of shadow/fail/good/go_die sets
  90
  91         Notes:
  92
  93         * Shadow enable/fail/good are all connected to all Shadow Functions
  94           (incoming at the top)
  95
  96         * Output is an array of "shadow active" (schroedinger wires: neither
  97           alive nor dead) and an array of "go die" signals, one per FU.
  98
  99         * the shadown must be connected to the Computation Unit's
 100           write release request, preventing it (ANDing) from firing
 101           (and thus preventing Writable.  this by the way being the
 102            whole point of having the Shadow Matrix...)
 103
 104         * go_die_o must be connected to *both* the Computation Unit's
 105           src-operand and result-operand latch resets, causing both
 106           of them to reset.
 107
 108         * go_die_o also needs to be wired into the Dependency and Function
 109           Unit Matrices by way of over-enabling (ORing) into Go_Read and
 110           Go_Write, resetting every cell that is required to "die"
 111     """
 112     def __init__(self, n_fus, shadow_wid=0):
 113         self.n_fus = n_fus
 114         self.shadow_wid = shadow_wid
 115
 116         # inputs
 117         self.issue_i = Signal(n_fus, reset_less=True)
 118         self.shadow_i = Signal(shadow_wid, reset_less=True)
 119         self.s_fail_i = Signal(shadow_wid, reset_less=True)
 120         self.s_good_i = Signal(shadow_wid, reset_less=True)
 121
 122         # outputs
 123         self.go_die_o = Signal(n_fus, reset_less=True)
 124         self.shadown_o = Signal(n_fus, reset_less=True)
 125
 126     def elaborate(self, platform):
 127         m = Module()
 128         shadows = []
 129         for i in range(self.n_fus):
 130             sh = Shadow(self.shadow_wid)
 131             setattr(m.submodules, "sh%d" % i, sh)
 132             shadows.append(sh)
 133
 134         # connect shadow/fail/good to all shadows
 135         for l in shadows:
 136             m.d.comb += l.s_fail_i.eq(self.s_fail_i)
 137             m.d.comb += l.s_good_i.eq(self.s_good_i)
 138             m.d.comb += l.shadow_i.eq(self.shadow_i)
 139
 140         # connect all shadow outputs and issue input
 141         issue_l = []
 142         sho_l = []
 143         rec_l = []
 144         for l in shadows:
 145             issue_l.append(l.issue_i)
 146             sho_l.append(l.shadown_o)
 147             rec_l.append(l.go_die_o)
 148         m.d.comb += Cat(*issue_l).eq(self.issue_i)
 149         m.d.comb += self.shadown_o.eq(Cat(*sho_l))
 150         m.d.comb += self.go_die_o.eq(Cat(*rec_l))
 151
 152         return m
 153
 154     def __iter__(self):
 155         yield self.issue_i
 156         yield self.shadow_i
 157         yield self.s_fail_i
 158         yield self.s_good_i
 159         yield self.go_die_o
 160         yield self.shadown_o
 161
 162     def ports(self):
 163         return list(self)
 164
 165
 166 def shadow_sim(dut):
 167     yield dut.dest_i.eq(1)
 168     yield dut.issue_i.eq(1)
 169     yield
 170     yield dut.issue_i.eq(0)
 171     yield
 172     yield dut.src1_i.eq(1)
 173     yield dut.issue_i.eq(1)
 174     yield
 175     yield
 176     yield
 177     yield dut.issue_i.eq(0)
 178     yield
 179     yield dut.go_rd_i.eq(1)
 180     yield
 181     yield dut.go_rd_i.eq(0)
 182     yield
 183     yield dut.go_wr_i.eq(1)
 184     yield
 185     yield dut.go_wr_i.eq(0)
 186     yield
 187
 188 def test_shadow():
 189     dut = ShadowMatrix(4, 2)
 190     vl = rtlil.convert(dut, ports=dut.ports())
 191     with open("test_shadow.il", "w") as f:
 192         f.write(vl)
 193
 194     run_simulation(dut, shadow_sim(dut), vcd_name='test_shadow.vcd')
 195
 196 if __name__ == '__main__':
 197     test_shadow()