1 from nmigen
.compat
.sim
import run_simulation
2 from nmigen
.cli
import verilog
, rtlil
3 from nmigen
import Module
, Signal
, Cat
, Elaboratable
4 from nmutil
.latch
import SRLatch
5 from nmigen
.lib
.coding
import Decoder
7 from shadow_fn
import ShadowFn
10 class FnUnit(Elaboratable
):
11 """ implements 11.4.8 function unit, p31
12 also implements optional shadowing 11.5.1, p55
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)
20 * dest_i / src1_i / src2_i are in *binary*, whereas
21 * g_rd_pend_i / g_wr_pend_i and rd_pend_o / wr_pend_o are UNARY vectors
22 * req_rel_i (request release) is the direct equivalent of pipeline
23 "output valid" (valid_o)
24 * recover is a local python variable (actually go_die_o)
25 * when shadow_wid = 0, recover and shadown are Consts (i.e. do nothing)
27 def __init__(self
, wid
, shadow_wid
=0):
29 self
.shadow_wid
= shadow_wid
32 self
.dest_i
= Signal(max=wid
, reset_less
=True) # Dest R# in (top)
33 self
.src1_i
= Signal(max=wid
, reset_less
=True) # oper1 R# in (top)
34 self
.src2_i
= Signal(max=wid
, reset_less
=True) # oper2 R# in (top)
35 self
.issue_i
= Signal(reset_less
=True) # Issue in (top)
37 self
.go_write_i
= Signal(reset_less
=True) # Go Write in (left)
38 self
.go_read_i
= Signal(reset_less
=True) # Go Read in (left)
39 self
.req_rel_i
= Signal(reset_less
=True) # request release (left)
41 self
.g_rd_pend_i
= Signal(wid
, reset_less
=True) # global rd (right)
42 self
.g_wr_pend_i
= Signal(wid
, reset_less
=True) # global wr (right)
45 self
.shadow_i
= Signal(shadow_wid
, reset_less
=True)
46 self
.s_fail_i
= Signal(shadow_wid
, reset_less
=True)
47 self
.s_good_i
= Signal(shadow_wid
, reset_less
=True)
48 self
.go_die_o
= Signal(reset_less
=True)
51 self
.readable_o
= Signal(reset_less
=True) # Readable out (right)
52 self
.writable_o
= Signal(reset_less
=True) # Writable out (right)
53 self
.busy_o
= Signal(reset_less
=True) # busy out (left)
55 self
.rd_pend_o
= Signal(wid
, reset_less
=True) # rd pending (right)
56 self
.wr_pend_o
= Signal(wid
, reset_less
=True) # wr pending (right)
58 def elaborate(self
, platform
):
60 m
.submodules
.rd_l
= rd_l
= SRLatch(sync
=False)
61 m
.submodules
.wr_l
= wr_l
= SRLatch(sync
=False)
62 m
.submodules
.dest_d
= dest_d
= Decoder(self
.reg_width
)
63 m
.submodules
.src1_d
= src1_d
= Decoder(self
.reg_width
)
64 m
.submodules
.src2_d
= src2_d
= Decoder(self
.reg_width
)
66 for i
in range(self
.shadow_wid
):
68 setattr(m
.submodules
, "shadow%d" % i
, sh
)
71 # shadow / recover (optional: shadow_wid > 0)
73 recover
= self
.go_die_o
74 shadown
= Signal(reset_less
=True)
81 # get list of latch signals. really must be a better way to do this
84 shi_l
.append(l
.shadow_i
)
85 fail_l
.append(l
.s_fail_i
)
86 good_l
.append(l
.s_good_i
)
87 sho_l
.append(l
.shadow_o
)
88 rec_l
.append(l
.recover_o
)
89 m
.d
.comb
+= Cat(*i_l
).eq(self
.issue_i
)
90 m
.d
.comb
+= Cat(*fail_l
).eq(self
.s_fail_i
)
91 m
.d
.comb
+= Cat(*good_l
).eq(self
.s_good_i
)
92 m
.d
.comb
+= Cat(*shi_l
).eq(self
.shadow_i
)
93 m
.d
.comb
+= shadown
.eq(~
(Cat(*sho_l
).bool()))
94 m
.d
.comb
+= recover
.eq(Cat(*rec_l
).bool())
99 # go_write latch: reset on go_write HI, set on issue
100 m
.d
.comb
+= wr_l
.s
.eq(self
.issue_i
)
101 m
.d
.comb
+= wr_l
.r
.eq(self
.go_write_i | recover
)
103 # src1 latch: reset on go_read HI, set on issue
104 m
.d
.comb
+= rd_l
.s
.eq(self
.issue_i
)
105 m
.d
.comb
+= rd_l
.r
.eq(self
.go_read_i | recover
)
107 # dest decoder: write-pending out
108 m
.d
.comb
+= dest_d
.i
.eq(self
.dest_i
)
109 m
.d
.comb
+= dest_d
.n
.eq(wr_l
.qn
) # decode is inverted
110 m
.d
.comb
+= self
.busy_o
.eq(wr_l
.q
) # busy if set
111 m
.d
.comb
+= self
.wr_pend_o
.eq(dest_d
.o
)
113 # src1/src2 decoder: read-pending out
114 m
.d
.comb
+= src1_d
.i
.eq(self
.src1_i
)
115 m
.d
.comb
+= src1_d
.n
.eq(rd_l
.qn
) # decode is inverted
116 m
.d
.comb
+= src2_d
.i
.eq(self
.src2_i
)
117 m
.d
.comb
+= src2_d
.n
.eq(rd_l
.qn
) # decode is inverted
118 m
.d
.comb
+= self
.rd_pend_o
.eq(src1_d
.o | src2_d
.o
)
120 # readable output signal
121 int_g_wr
= Signal(self
.reg_width
, reset_less
=True)
122 m
.d
.comb
+= int_g_wr
.eq(self
.g_wr_pend_i
& self
.rd_pend_o
)
123 m
.d
.comb
+= self
.readable_o
.eq(int_g_wr
.bool())
125 # writable output signal
126 int_g_rw
= Signal(self
.reg_width
, reset_less
=True)
127 g_rw
= Signal(reset_less
=True)
128 m
.d
.comb
+= int_g_rw
.eq(self
.g_rd_pend_i
& self
.wr_pend_o
)
129 m
.d
.comb
+= g_rw
.eq(~int_g_rw
.bool())
130 m
.d
.comb
+= self
.writable_o
.eq(g_rw
& rd_l
.q
& self
.req_rel_i
& shadown
)
139 yield self
.go_write_i
142 yield self
.g_rd_pend_i
143 yield self
.g_wr_pend_i
144 yield self
.readable_o
145 yield self
.writable_o
153 def int_fn_unit_sim(dut
):
154 yield dut
.dest_i
.eq(1)
155 yield dut
.issue_i
.eq(1)
157 yield dut
.issue_i
.eq(0)
159 yield dut
.src1_i
.eq(1)
160 yield dut
.issue_i
.eq(1)
164 yield dut
.issue_i
.eq(0)
166 yield dut
.go_read_i
.eq(1)
168 yield dut
.go_read_i
.eq(0)
170 yield dut
.go_write_i
.eq(1)
172 yield dut
.go_write_i
.eq(0)
175 def test_int_fn_unit():
177 vl
= rtlil
.convert(dut
, ports
=dut
.ports())
178 with
open("test_int_fn_unit.il", "w") as f
:
181 run_simulation(dut
, int_fn_unit_sim(dut
), vcd_name
='test_int_fn_unit.vcd')
183 if __name__
== '__main__':