1 from nmigen
.compat
.sim
import run_simulation
2 from nmigen
.cli
import verilog
, rtlil
3 from nmigen
import Module
, Signal
, Elaboratable
, Array
, Cat
, Repl
4 from nmutil
.latch
import SRLatch
5 from functools
import reduce
6 from operator
import or_
9 class DependencyRow(Elaboratable
):
10 """ implements 11.4.7 mitch alsup dependence cell, p27
11 adjusted to be clock-sync'd on rising edge only.
12 mitch design (as does 6600) requires alternating rising/falling clock
14 * SET mode: issue_i HI, go_i LO, reg_i HI - register is captured
15 - FWD is DISABLED (~issue_i)
17 * QRY mode: issue_i LO, go_i LO, haz_i HI - FWD is ASSERTED
19 * GO mode : issue_i LO, go_i HI - RSEL is ASSERTED
20 haz_i HI - FWD still can be ASSERTED
22 FWD assertion (hazard protection) therefore still occurs in both
23 Query and Go Modes, for this cycle, due to the cq register
25 GO mode works for one cycle, again due to the cq register capturing
26 the latch output. Without the cq register, the SR Latch (which is
27 asynchronous) would be reset at the exact moment that GO was requested,
28 and the RSEL would be garbage.
30 def __init__(self
, n_reg
, n_src
):
37 for i
in range(n_src
):
38 j
= i
+ 1 # name numbering to match src1/src2
39 src
.append(Signal(n_reg
, name
="src%d" % j
, reset_less
=True))
40 rsel
.append(Signal(n_reg
, name
="src%d_rsel_o" % j
, reset_less
=True))
41 fwd
.append(Signal(n_reg
, name
="src%d_fwd_o" % j
, reset_less
=True))
44 self
.dest_i
= Signal(n_reg
, reset_less
=True) # Dest in (top)
45 self
.src_i
= Array(src
) # operands in (top)
46 self
.issue_i
= Signal(reset_less
=True) # Issue in (top)
48 self
.rd_pend_i
= Signal(n_reg
, reset_less
=True) # Read pend in (top)
49 self
.wr_pend_i
= Signal(n_reg
, reset_less
=True) # Write pend in (top)
50 self
.v_rd_rsel_o
= Signal(n_reg
, reset_less
=True) # Read pend out (bot)
51 self
.v_wr_rsel_o
= Signal(n_reg
, reset_less
=True) # Write pend out (bot)
53 self
.go_wr_i
= Signal(reset_less
=True) # Go Write in (left)
54 self
.go_rd_i
= Signal(reset_less
=True) # Go Read in (left)
55 self
.go_die_i
= Signal(reset_less
=True) # Go Die in (left)
57 # for Register File Select Lines (vertical)
58 self
.dest_rsel_o
= Signal(n_reg
, reset_less
=True) # dest reg sel (bot)
59 self
.src_rsel_o
= Array(rsel
) # src reg sel (bot)
60 self
.src2_rsel_o
= Signal(n_reg
, reset_less
=True) # src2 reg sel (bot)
62 # for Function Unit "forward progress" (horizontal)
63 self
.dest_fwd_o
= Signal(n_reg
, reset_less
=True) # dest FU fw (right)
64 self
.src_fwd_o
= Array(fwd
) # src FU fw (right)
66 def elaborate(self
, platform
):
68 m
.submodules
.dest_c
= dest_c
= SRLatch(sync
=False, llen
=self
.n_reg
)
70 for i
in range(self
.n_src
):
71 src_l
= SRLatch(sync
=False, llen
=self
.n_reg
)
72 setattr(m
.submodules
, "src%d_c" % (i
+1), src_l
)
75 # connect go_rd / go_wr (dest->wr, src->rd)
76 wr_die
= Signal(reset_less
=True)
77 rd_die
= Signal(reset_less
=True)
78 m
.d
.comb
+= wr_die
.eq(self
.go_wr_i | self
.go_die_i
)
79 m
.d
.comb
+= rd_die
.eq(self
.go_rd_i | self
.go_die_i
)
80 m
.d
.comb
+= dest_c
.r
.eq(Repl(wr_die
, self
.n_reg
))
81 for i
in range(self
.n_src
):
82 m
.d
.comb
+= src_c
[i
].r
.eq(Repl(rd_die
, self
.n_reg
))
84 # connect input reg bit (unary)
85 i_ext
= Repl(self
.issue_i
, self
.n_reg
)
86 m
.d
.comb
+= dest_c
.s
.eq(i_ext
& self
.dest_i
)
87 for i
in range(self
.n_src
):
88 m
.d
.comb
+= src_c
[i
].s
.eq(i_ext
& self
.src_i
[i
])
90 # connect up hazard checks: read-after-write and write-after-read
91 m
.d
.comb
+= self
.dest_fwd_o
.eq(dest_c
.q
& self
.rd_pend_i
)
92 for i
in range(self
.n_src
):
93 m
.d
.comb
+= self
.src_fwd_o
[i
].eq(src_c
[i
].q
& self
.wr_pend_i
)
95 # connect reg-sel outputs
96 rd_ext
= Repl(self
.go_rd_i
, self
.n_reg
)
97 wr_ext
= Repl(self
.go_wr_i
, self
.n_reg
)
98 m
.d
.comb
+= self
.dest_rsel_o
.eq(dest_c
.qlq
& wr_ext
)
99 for i
in range(self
.n_src
):
100 m
.d
.comb
+= self
.src_rsel_o
[i
].eq(src_c
[i
].qlq
& rd_ext
)
102 # to be accumulated to indicate if register is in use (globally)
103 # after ORing, is fed back in to rd_pend_i / wr_pend_i
105 for i
in range(self
.n_src
):
106 src_q
.append(src_c
[i
].qlq
)
107 m
.d
.comb
+= self
.v_rd_rsel_o
.eq(reduce(or_
, src_q
))
108 m
.d
.comb
+= self
.v_wr_rsel_o
.eq(dest_c
.qlq
)
114 yield from self
.src_i
121 yield self
.dest_rsel_o
122 yield from self
.src_rsel_o
123 yield self
.dest_fwd_o
124 yield from self
.src_fwd_o
131 yield dut
.dest_i
.eq(1)
132 yield dut
.issue_i
.eq(1)
134 yield dut
.issue_i
.eq(0)
136 yield dut
.src1_i
.eq(1)
137 yield dut
.issue_i
.eq(1)
141 yield dut
.issue_i
.eq(0)
143 yield dut
.go_rd_i
.eq(1)
145 yield dut
.go_rd_i
.eq(0)
147 yield dut
.go_wr_i
.eq(1)
149 yield dut
.go_wr_i
.eq(0)
153 dut
= DependencyRow(4, 2)
154 vl
= rtlil
.convert(dut
, ports
=dut
.ports())
155 with
open("test_drow.il", "w") as f
:
158 run_simulation(dut
, dcell_sim(dut
), vcd_name
='test_dcell.vcd')
160 if __name__
== '__main__':