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, Repl
   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             # inputs
  29             self.issue_i = Signal(reset_less=True)
  30             self.shadow_i = Signal(shadow_wid, reset_less=True)
  31             self.s_fail_i = Signal(shadow_wid, reset_less=True)
  32             self.s_good_i = Signal(shadow_wid, reset_less=True)
  33             # outputs
  34             self.go_die_o = Signal(reset_less=True)
  35             self.shadown_o = Signal(reset_less=True)
  36         else:
  37             # outputs when no shadowing needed
  38             self.shadown_o = Const(1)
  39             self.go_die_o = Const(0)
  40
  41     def elaborate(self, platform):
  42         m = Module()
  43         s_latches = []
  44         for i in range(self.shadow_wid):
  45             sh = ShadowFn()
  46             setattr(m.submodules, "shadow%d" % i, sh)
  47             s_latches.append(sh)
  48
  49         # shadow / recover (optional: shadow_wid > 0)
  50         if self.shadow_wid:
  51             i_l = []
  52             fail_l = []
  53             good_l = []
  54             shi_l = []
  55             sho_l = []
  56             rec_l = []
  57             # get list of latch signals. really must be a better way to do this
  58             for l in s_latches:
  59                 i_l.append(l.issue_i)
  60                 shi_l.append(l.shadow_i)
  61                 fail_l.append(l.s_fail_i)
  62                 good_l.append(l.s_good_i)
  63                 sho_l.append(l.shadow_o)
  64                 rec_l.append(l.recover_o)
  65             m.d.comb += Cat(*i_l).eq(Repl(self.issue_i, self.shadow_wid))
  66             m.d.comb += Cat(*fail_l).eq(self.s_fail_i)
  67             m.d.comb += Cat(*good_l).eq(self.s_good_i)
  68             m.d.comb += Cat(*shi_l).eq(self.shadow_i)
  69             m.d.comb += self.shadown_o.eq(~(Cat(*sho_l).bool()))
  70             m.d.comb += self.go_die_o.eq(Cat(*rec_l).bool())
  71
  72         return m
  73
  74     def __iter__(self):
  75         if self.shadow_wid:
  76             yield self.issue_i
  77             yield self.shadow_i
  78             yield self.s_fail_i
  79             yield self.s_good_i
  80         yield self.go_die_o
  81         yield self.shadown_o
  82
  83     def ports(self):
  84         return list(self)
  85
  86
  87 class ShadowMatrix(Elaboratable):
  88     """ Matrix of Shadow Functions.  One per FU.
  89
  90         Inputs
  91         * :n_fus:       register file width
  92         * :shadow_wid:  number of shadow/fail/good/go_die sets
  93
  94         Notes:
  95
  96         * Shadow enable/fail/good are all connected to all Shadow Functions
  97           (incoming at the top)
  98
  99         * Output is an array of "shadow active" (schroedinger wires: neither
 100           alive nor dead) and an array of "go die" signals, one per FU.
 101
 102         * the shadown must be connected to the Computation Unit's
 103           write release request, preventing it (ANDing) from firing
 104           (and thus preventing Writable.  this by the way being the
 105            whole point of having the Shadow Matrix...)
 106
 107         * go_die_o must be connected to *both* the Computation Unit's
 108           src-operand and result-operand latch resets, causing both
 109           of them to reset.
 110
 111         * go_die_o also needs to be wired into the Dependency and Function
 112           Unit Matrices by way of over-enabling (ORing) into Go_Read and
 113           Go_Write, resetting every cell that is required to "die"
 114     """
 115     def __init__(self, n_fus, shadow_wid=0):
 116         self.n_fus = n_fus
 117         self.shadow_wid = shadow_wid
 118
 119         # inputs
 120         self.issue_i = Signal(n_fus, reset_less=True)
 121         self.shadow_i = Array(Signal(shadow_wid, name="sh_i", reset_less=True) \
 122                             for f in range(n_fus))
 123         self.s_fail_i = Signal(shadow_wid, reset_less=True)
 124         self.s_good_i = Signal(shadow_wid, reset_less=True)
 125
 126         # outputs
 127         self.go_die_o = Signal(n_fus, reset_less=True)
 128         self.shadown_o = Signal(n_fus, reset_less=True)
 129
 130     def elaborate(self, platform):
 131         m = Module()
 132         shadows = []
 133         for i in range(self.n_fus):
 134             sh = Shadow(self.shadow_wid)
 135             setattr(m.submodules, "sh%d" % i, sh)
 136             shadows.append(sh)
 137             # connect shadow/fail/good to all shadows
 138             m.d.comb += sh.s_fail_i.eq(self.s_fail_i)
 139             m.d.comb += sh.s_good_i.eq(self.s_good_i)
 140             # this one is the matrix (shadow enables)
 141             m.d.comb += sh.shadow_i.eq(self.shadow_i[i])
 142
 143         # connect all shadow outputs and issue input
 144         issue_l = []
 145         sho_l = []
 146         rec_l = []
 147         for l in shadows:
 148             issue_l.append(l.issue_i)
 149             sho_l.append(l.shadown_o)
 150             rec_l.append(l.go_die_o)
 151         m.d.comb += Cat(*issue_l).eq(self.issue_i)
 152         m.d.comb += self.shadown_o.eq(Cat(*sho_l))
 153         m.d.comb += self.go_die_o.eq(Cat(*rec_l))
 154
 155         return m
 156
 157     def __iter__(self):
 158         yield self.issue_i
 159         yield from self.shadow_i
 160         yield self.s_fail_i
 161         yield self.s_good_i
 162         yield self.go_die_o
 163         yield self.shadown_o
 164
 165     def ports(self):
 166         return list(self)
 167
 168
 169 class WaWGrid(Elaboratable):
 170     """ An NxM grid-selector which raises a 2D bit selected by N and M
 171     """
 172
 173     def __init__(self, n_fus, shadow_wid):
 174         self.n_fus = n_fus
 175         self.shadow_wid = shadow_wid
 176
 177         self.shadow_i = Signal(shadow_wid, reset_less=True)
 178         self.fu_i = Signal(n_fus, reset_less=True)
 179
 180         self.waw_o = Array(Signal(shadow_wid, name="waw_o", reset_less=True) \
 181                             for f in range(n_fus))
 182
 183     def elaborate(self, platform):
 184         m = Module()
 185         for i in range(self.n_fus):
 186             v = Repl(self.fu_i[i], self.shadow_wid)
 187             m.d.comb += self.waw_o[i].eq(v & self.shadow_i)
 188         return m
 189
 190
 191 def shadow_sim(dut):
 192     yield dut.dest_i.eq(1)
 193     yield dut.issue_i.eq(1)
 194     yield
 195     yield dut.issue_i.eq(0)
 196     yield
 197     yield dut.src1_i.eq(1)
 198     yield dut.issue_i.eq(1)
 199     yield
 200     yield
 201     yield
 202     yield dut.issue_i.eq(0)
 203     yield
 204     yield dut.go_rd_i.eq(1)
 205     yield
 206     yield dut.go_rd_i.eq(0)
 207     yield
 208     yield dut.go_wr_i.eq(1)
 209     yield
 210     yield dut.go_wr_i.eq(0)
 211     yield
 212
 213 def test_shadow():
 214     dut = ShadowMatrix(4, 2)
 215     vl = rtlil.convert(dut, ports=dut.ports())
 216     with open("test_shadow.il", "w") as f:
 217         f.write(vl)
 218
 219     run_simulation(dut, shadow_sim(dut), vcd_name='test_shadow.vcd')
 220
 221 if __name__ == '__main__':
 222     test_shadow()