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-rw-r--r--passes/opt/opt_expr.cc136
-rw-r--r--tests/fsm/generate.py8
-rw-r--r--tests/opt/bug1758.ys21
-rw-r--r--tests/opt/opt_expr_alu.ys3
-rw-r--r--tests/opt/opt_expr_and.ys85
-rw-r--r--tests/opt/opt_expr_consumex.ys35
-rw-r--r--tests/opt/opt_expr_or.ys85
-rw-r--r--tests/opt/opt_expr_xnor.ys131
-rw-r--r--tests/opt/opt_expr_xor.ys88
9 files changed, 562 insertions, 30 deletions
diff --git a/passes/opt/opt_expr.cc b/passes/opt/opt_expr.cc
index 0f5bff680..777a24777 100644
--- a/passes/opt/opt_expr.cc
+++ b/passes/opt/opt_expr.cc
@@ -132,7 +132,7 @@ void replace_cell(SigMap &assign_map, RTLIL::Module *module, RTLIL::Cell *cell,
did_something = true;
}
-bool group_cell_inputs(RTLIL::Module *module, RTLIL::Cell *cell, bool commutative, SigMap &sigmap)
+bool group_cell_inputs(RTLIL::Module *module, RTLIL::Cell *cell, bool commutative, SigMap &sigmap, bool keepdc)
{
IdString b_name = cell->hasPort(ID::B) ? ID::B : ID::A;
@@ -156,20 +156,36 @@ bool group_cell_inputs(RTLIL::Module *module, RTLIL::Cell *cell, bool commutativ
int group_idx = GRP_DYN;
RTLIL::SigBit bit_a = bits_a[i], bit_b = bits_b[i];
- if (cell->type == ID($or) && (bit_a == RTLIL::State::S1 || bit_b == RTLIL::State::S1))
- bit_a = bit_b = RTLIL::State::S1;
-
- if (cell->type == ID($and) && (bit_a == RTLIL::State::S0 || bit_b == RTLIL::State::S0))
- bit_a = bit_b = RTLIL::State::S0;
+ if (cell->type == ID($or)) {
+ if (bit_a == RTLIL::State::S1 || bit_b == RTLIL::State::S1)
+ bit_a = bit_b = RTLIL::State::S1;
+ }
+ else if (cell->type == ID($and)) {
+ if (bit_a == RTLIL::State::S0 || bit_b == RTLIL::State::S0)
+ bit_a = bit_b = RTLIL::State::S0;
+ }
+ else if (!keepdc) {
+ if (cell->type == ID($xor)) {
+ if (bit_a == bit_b)
+ bit_a = bit_b = RTLIL::State::S0;
+ }
+ else if (cell->type == ID($xnor)) {
+ if (bit_a == bit_b)
+ bit_a = bit_b = RTLIL::State::S1; // For consistency with gate-level which does $xnor -> $_XOR_ + $_NOT_
+ }
+ }
- if (bit_a.wire == NULL && bit_b.wire == NULL)
- group_idx = GRP_CONST_AB;
- else if (bit_a.wire == NULL)
- group_idx = GRP_CONST_A;
- else if (bit_b.wire == NULL && commutative)
- group_idx = GRP_CONST_A, std::swap(bit_a, bit_b);
- else if (bit_b.wire == NULL)
- group_idx = GRP_CONST_B;
+ bool def = (bit_a != State::Sx && bit_a != State::Sz && bit_b != State::Sx && bit_b != State::Sz);
+ if (def || !keepdc) {
+ if (bit_a.wire == NULL && bit_b.wire == NULL)
+ group_idx = GRP_CONST_AB;
+ else if (bit_a.wire == NULL)
+ group_idx = GRP_CONST_A;
+ else if (bit_b.wire == NULL && commutative)
+ group_idx = GRP_CONST_A, std::swap(bit_a, bit_b);
+ else if (bit_b.wire == NULL)
+ group_idx = GRP_CONST_B;
+ }
grouped_bits[group_idx][std::pair<RTLIL::SigBit, RTLIL::SigBit>(bit_a, bit_b)].insert(bits_y[i]);
}
@@ -186,26 +202,77 @@ bool group_cell_inputs(RTLIL::Module *module, RTLIL::Cell *cell, bool commutativ
if (grouped_bits[i].empty())
continue;
- RTLIL::Wire *new_y = module->addWire(NEW_ID, GetSize(grouped_bits[i]));
+ RTLIL::SigSpec new_y = module->addWire(NEW_ID, GetSize(grouped_bits[i]));
RTLIL::SigSpec new_a, new_b;
RTLIL::SigSig new_conn;
for (auto &it : grouped_bits[i]) {
for (auto &bit : it.second) {
new_conn.first.append(bit);
- new_conn.second.append(RTLIL::SigBit(new_y, new_a.size()));
+ new_conn.second.append(new_y[new_a.size()]);
}
new_a.append(it.first.first);
new_b.append(it.first.second);
}
if (cell->type.in(ID($and), ID($or)) && i == GRP_CONST_A) {
+ if (!keepdc) {
+ if (cell->type == ID($and))
+ new_a.replace(dict<SigBit,SigBit>{{State::Sx, State::S0}, {State::Sz, State::S0}}, &new_b);
+ else if (cell->type == ID($or))
+ new_a.replace(dict<SigBit,SigBit>{{State::Sx, State::S1}, {State::Sz, State::S1}}, &new_b);
+ else log_abort();
+ }
log_debug(" Direct Connection: %s (%s with %s)\n", log_signal(new_b), log_id(cell->type), log_signal(new_a));
module->connect(new_y, new_b);
module->connect(new_conn);
continue;
}
+ if (cell->type.in(ID($xor), ID($xnor)) && i == GRP_CONST_A) {
+ SigSpec undef_a, undef_y, undef_b;
+ SigSpec def_y, def_a, def_b;
+ for (int i = 0; i < GetSize(new_y); i++) {
+ bool undef = new_a[i] == State::Sx || new_a[i] == State::Sz;
+ if (!keepdc && (undef || new_a[i] == new_b[i])) {
+ undef_a.append(new_a[i]);
+ if (cell->type == ID($xor))
+ undef_b.append(State::S0);
+ // For consistency since simplemap does $xnor -> $_XOR_ + $_NOT_
+ else if (cell->type == ID($xnor))
+ undef_b.append(State::S1);
+ else log_abort();
+ undef_y.append(new_y[i]);
+ }
+ else if (new_a[i] == State::S0 || new_a[i] == State::S1) {
+ undef_a.append(new_a[i]);
+ if (cell->type == ID($xor))
+ undef_b.append(new_a[i] == State::S1 ? module->Not(NEW_ID, new_b[i]).as_bit() : new_b[i]);
+ else if (cell->type == ID($xnor))
+ undef_b.append(new_a[i] == State::S1 ? new_b[i] : module->Not(NEW_ID, new_b[i]).as_bit());
+ else log_abort();
+ undef_y.append(new_y[i]);
+ }
+ else {
+ def_a.append(new_a[i]);
+ def_b.append(new_b[i]);
+ def_y.append(new_y[i]);
+ }
+ }
+ if (!undef_y.empty()) {
+ log_debug(" Direct Connection: %s (%s with %s)\n", log_signal(undef_b), log_id(cell->type), log_signal(undef_a));
+ module->connect(undef_y, undef_b);
+ if (def_y.empty()) {
+ module->connect(new_conn);
+ continue;
+ }
+ }
+ new_a = std::move(def_a);
+ new_b = std::move(def_b);
+ new_y = std::move(def_y);
+ }
+
+
RTLIL::Cell *c = module->addCell(NEW_ID, cell->type);
c->setPort(ID::A, new_a);
@@ -219,7 +286,7 @@ bool group_cell_inputs(RTLIL::Module *module, RTLIL::Cell *cell, bool commutativ
}
c->setPort(ID::Y, new_y);
- c->parameters[ID::Y_WIDTH] = new_y->width;
+ c->parameters[ID::Y_WIDTH] = GetSize(new_y);
c->check();
module->connect(new_conn);
@@ -476,13 +543,13 @@ void replace_const_cells(RTLIL::Design *design, RTLIL::Module *module, bool cons
}
}
- if (detect_const_and && (found_zero || found_inv)) {
+ if (detect_const_and && (found_zero || found_inv || (found_undef && consume_x))) {
cover("opt.opt_expr.const_and");
replace_cell(assign_map, module, cell, "const_and", ID::Y, RTLIL::State::S0);
goto next_cell;
}
- if (detect_const_or && (found_one || found_inv)) {
+ if (detect_const_or && (found_one || found_inv || (found_undef && consume_x))) {
cover("opt.opt_expr.const_or");
replace_cell(assign_map, module, cell, "const_or", ID::Y, RTLIL::State::S1);
goto next_cell;
@@ -499,6 +566,22 @@ void replace_const_cells(RTLIL::Design *design, RTLIL::Module *module, bool cons
{
SigBit sig_a = assign_map(cell->getPort(ID::A));
SigBit sig_b = assign_map(cell->getPort(ID::B));
+ if (!keepdc && (sig_a == sig_b || sig_a == State::Sx || sig_a == State::Sz || sig_b == State::Sx || sig_b == State::Sz)) {
+ if (cell->type.in(ID($xor), ID($_XOR_))) {
+ cover("opt.opt_expr.const_xor");
+ replace_cell(assign_map, module, cell, "const_xor", ID::Y, RTLIL::State::S0);
+ goto next_cell;
+ }
+ if (cell->type.in(ID($xnor), ID($_XNOR_))) {
+ cover("opt.opt_expr.const_xnor");
+ // For consistency since simplemap does $xnor -> $_XOR_ + $_NOT_
+ int width = cell->getParam(ID::Y_WIDTH).as_int();
+ replace_cell(assign_map, module, cell, "const_xnor", ID::Y, SigSpec(RTLIL::State::S1, width));
+ goto next_cell;
+ }
+ log_abort();
+ }
+
if (!sig_a.wire)
std::swap(sig_a, sig_b);
if (sig_b == State::S0 || sig_b == State::S1) {
@@ -550,7 +633,7 @@ void replace_const_cells(RTLIL::Design *design, RTLIL::Module *module, bool cons
if (do_fine)
{
if (cell->type.in(ID($not), ID($pos), ID($and), ID($or), ID($xor), ID($xnor)))
- if (group_cell_inputs(module, cell, true, assign_map))
+ if (group_cell_inputs(module, cell, true, assign_map, keepdc))
goto next_cell;
if (cell->type.in(ID($logic_not), ID($logic_and), ID($logic_or), ID($reduce_or), ID($reduce_and), ID($reduce_bool)))
@@ -904,8 +987,10 @@ skip_fine_alu:
if (input.match("01")) ACTION_DO_Y(1);
if (input.match("10")) ACTION_DO_Y(1);
if (input.match("11")) ACTION_DO_Y(0);
- if (input.match(" *")) ACTION_DO_Y(x);
- if (input.match("* ")) ACTION_DO_Y(x);
+ if (consume_x) {
+ if (input.match(" *")) ACTION_DO_Y(0);
+ if (input.match("* ")) ACTION_DO_Y(0);
+ }
}
if (cell->type == ID($_MUX_)) {
@@ -1088,7 +1173,7 @@ skip_fine_alu:
goto next_cell;
}
- if (!keepdc)
+ if (consume_x)
{
bool identity_wrt_a = false;
bool identity_wrt_b = false;
@@ -1980,11 +2065,12 @@ struct OptExprPass : public Pass {
do {
do {
did_something = false;
- replace_const_cells(design, module, false, mux_undef, mux_bool, do_fine, keepdc, clkinv);
+ replace_const_cells(design, module, false /* consume_x */, mux_undef, mux_bool, do_fine, keepdc, clkinv);
if (did_something)
design->scratchpad_set_bool("opt.did_something", true);
} while (did_something);
- replace_const_cells(design, module, true, mux_undef, mux_bool, do_fine, keepdc, clkinv);
+ if (!keepdc)
+ replace_const_cells(design, module, true /* consume_x */, mux_undef, mux_bool, do_fine, keepdc, clkinv);
if (did_something)
design->scratchpad_set_bool("opt.did_something", true);
} while (did_something);
diff --git a/tests/fsm/generate.py b/tests/fsm/generate.py
index c8eda0cd1..784e5a054 100644
--- a/tests/fsm/generate.py
+++ b/tests/fsm/generate.py
@@ -36,9 +36,11 @@ parser.add_argument('-S', '--seed', type = int, help = 'seed for PRNG')
parser.add_argument('-c', '--count', type = int, default = 50, help = 'number of test cases to generate')
args = parser.parse_args()
-if args.seed is not None:
- print("PRNG seed: %d" % args.seed)
- random.seed(args.seed)
+seed = args.seed
+if seed is None:
+ seed = random.randrange(sys.maxsize)
+print("PRNG seed: %d" % seed)
+random.seed(seed)
for idx in range(args.count):
with open('temp/uut_%05d.v' % idx, 'w') as f:
diff --git a/tests/opt/bug1758.ys b/tests/opt/bug1758.ys
new file mode 100644
index 000000000..85dfaceb8
--- /dev/null
+++ b/tests/opt/bug1758.ys
@@ -0,0 +1,21 @@
+read_verilog -noopt <<EOT
+module gold(input i, output o);
+assign o = 1'bx | i;
+endmodule
+EOT
+copy gold coarse
+copy gold fine
+
+cd coarse
+opt_expr
+select -assert-none c:*
+
+cd fine
+opt_expr
+select -assert-none c:*
+
+cd
+miter -equiv -flatten -make_assert -make_outputs coarse fine miter
+sat -verify -prove-asserts -show-ports miter
+miter -equiv -flatten -make_assert -make_outputs -ignore_gold_x gold coarse miter2
+sat -verify -prove-asserts -show-ports -enable_undef miter2
diff --git a/tests/opt/opt_expr_alu.ys b/tests/opt/opt_expr_alu.ys
index 9121c0096..477555da9 100644
--- a/tests/opt/opt_expr_alu.ys
+++ b/tests/opt/opt_expr_alu.ys
@@ -59,9 +59,8 @@ EOT
alumacc
equiv_opt -assert opt_expr -fine
design -load postopt
-select -assert-count 1 t:$pos
select -assert-count 1 t:$not
-select -assert-none t:$pos t:$not %% t:* %D
+select -assert-none t:$not %% t:* %D
design -reset
diff --git a/tests/opt/opt_expr_and.ys b/tests/opt/opt_expr_and.ys
new file mode 100644
index 000000000..a7676a1df
--- /dev/null
+++ b/tests/opt/opt_expr_and.ys
@@ -0,0 +1,85 @@
+# Single-bit $and
+read_verilog -noopt <<EOT
+module gold(input i, output o);
+assign o = 1'bx & i;
+endmodule
+EOT
+select -assert-count 1 t:$and
+copy gold coarse
+copy gold fine
+copy gold coarse_keepdc
+copy gold fine_keepdc
+
+cd coarse
+opt_expr
+select -assert-none c:*
+
+cd fine
+simplemap
+opt_expr
+select -assert-none c:*
+
+cd
+miter -equiv -flatten -make_assert -make_outputs -ignore_gold_x gold coarse miter
+sat -verify -prove-asserts -show-ports -enable_undef miter
+miter -equiv -flatten -make_assert -make_outputs coarse fine miter2
+sat -verify -prove-asserts -show-ports -enable_undef miter2
+
+cd coarse_keepdc
+opt_expr -keepdc
+select -assert-count 1 c:*
+
+cd fine_keepdc
+simplemap
+opt_expr -keepdc
+select -assert-count 1 c:*
+
+cd
+miter -equiv -flatten -make_assert -make_outputs gold coarse_keepdc miter3
+sat -verify -prove-asserts -show-ports -enable_undef miter3
+miter -equiv -flatten -make_assert -make_outputs coarse_keepdc fine_keepdc miter4
+sat -verify -prove-asserts -show-ports -enable_undef miter4
+
+
+# Multi-bit $and
+design -reset
+read_verilog -noopt <<EOT
+module gold(input i, output [6:0] o);
+assign o = {1'bx, 1'b0, 1'b0, 1'b1, 1'bx, 1'b1, i} & {7{i}};
+endmodule
+EOT
+select -assert-count 1 t:$and
+copy gold coarse
+copy gold fine
+copy gold coarse_keepdc
+copy gold fine_keepdc
+
+cd coarse
+opt_expr -fine
+select -assert-none c:*
+
+cd fine
+simplemap
+opt_expr
+select -assert-none c:*
+
+cd
+miter -equiv -flatten -make_assert -make_outputs -ignore_gold_x gold coarse miter
+sat -verify -prove-asserts -show-ports -enable_undef miter
+miter -equiv -flatten -make_assert -make_outputs coarse fine miter2
+sat -verify -prove-asserts -show-ports -enable_undef miter2
+
+cd coarse_keepdc
+opt_expr -fine -keepdc
+select -assert-count 1 c:*
+
+cd fine_keepdc
+simplemap
+opt_expr -keepdc
+select -assert-count 2 c:*
+
+cd
+miter -equiv -flatten -make_assert -make_outputs gold coarse_keepdc miter3
+sat -verify -prove-asserts -show-ports -enable_undef miter3
+miter -equiv -flatten -make_assert -make_outputs coarse_keepdc fine_keepdc miter4
+sat -verify -prove-asserts -show-ports -enable_undef miter4
diff --git a/tests/opt/opt_expr_consumex.ys b/tests/opt/opt_expr_consumex.ys
new file mode 100644
index 000000000..d4af10f22
--- /dev/null
+++ b/tests/opt/opt_expr_consumex.ys
@@ -0,0 +1,35 @@
+read_verilog <<EOT
+module top(input a, b, output o);
+wire tmp;
+assign o = tmp | 1'bx;
+assign tmp = a & 1'b0;
+endmodule
+EOT
+design -save read
+select -assert-count 1 t:$and
+select -assert-count 1 t:$or
+
+
+opt_expr
+select -assert-none t:$and t:$or
+sat -verify -enable_undef -prove o 1'bx
+
+
+design -load read
+opt_expr -keepdc
+select -assert-none t:$and t:$or
+sat -verify -enable_undef -prove o 1'bx
+
+
+design -load read
+simplemap
+opt_expr -keepdc
+select -assert-none t:$_AND_ t:$_OR_
+sat -verify -enable_undef -prove o 1'bx
+
+
+design -load read
+simplemap
+opt_expr -keepdc
+select -assert-none t:$_AND_ t:$_OR_
+sat -verify -enable_undef -prove o 1'bx
diff --git a/tests/opt/opt_expr_or.ys b/tests/opt/opt_expr_or.ys
new file mode 100644
index 000000000..f86da0d46
--- /dev/null
+++ b/tests/opt/opt_expr_or.ys
@@ -0,0 +1,85 @@
+# Single-bit $or
+read_verilog -noopt <<EOT
+module gold(input i, output o);
+assign o = 1'bx | i;
+endmodule
+EOT
+select -assert-count 1 t:$or
+copy gold coarse
+copy gold fine
+copy gold coarse_keepdc
+copy gold fine_keepdc
+
+cd coarse
+opt_expr
+select -assert-none c:*
+
+cd fine
+simplemap
+opt_expr
+select -assert-none c:*
+
+cd
+miter -equiv -flatten -make_assert -make_outputs -ignore_gold_x gold coarse miter
+sat -verify -prove-asserts -show-ports -enable_undef miter
+miter -equiv -flatten -make_assert -make_outputs coarse fine miter2
+sat -verify -prove-asserts -show-ports -enable_undef miter2
+
+cd coarse_keepdc
+opt_expr -keepdc
+select -assert-count 1 c:*
+
+cd fine_keepdc
+simplemap
+opt_expr -keepdc
+select -assert-count 1 c:*
+
+cd
+miter -equiv -flatten -make_assert -make_outputs gold coarse_keepdc miter3
+sat -verify -prove-asserts -show-ports -enable_undef miter3
+miter -equiv -flatten -make_assert -make_outputs coarse_keepdc fine_keepdc miter4
+sat -verify -prove-asserts -show-ports -enable_undef miter4
+
+
+# Multi-bit $or
+design -reset
+read_verilog -noopt <<EOT
+module gold(input i, output [6:0] o);
+assign o = {1'bx, 1'b0, 1'b0, 1'b1, 1'bx, 1'b1, i} | {7{i}};
+endmodule
+EOT
+select -assert-count 1 t:$or
+copy gold coarse
+copy gold fine
+copy gold coarse_keepdc
+copy gold fine_keepdc
+
+cd coarse
+opt_expr -fine
+select -assert-none c:*
+
+cd fine
+simplemap
+opt_expr
+select -assert-none c:*
+
+cd
+miter -equiv -flatten -make_assert -make_outputs -ignore_gold_x gold coarse miter
+sat -verify -prove-asserts -show-ports -enable_undef miter
+miter -equiv -flatten -make_assert -make_outputs coarse fine miter2
+sat -verify -prove-asserts -show-ports -enable_undef miter2
+
+cd coarse_keepdc
+opt_expr -fine -keepdc
+select -assert-count 1 c:*
+
+cd fine_keepdc
+simplemap
+opt_expr -keepdc
+select -assert-count 2 c:*
+
+cd
+miter -equiv -flatten -make_assert -make_outputs gold coarse_keepdc miter3
+sat -verify -prove-asserts -show-ports -enable_undef miter3
+miter -equiv -flatten -make_assert -make_outputs coarse_keepdc fine_keepdc miter4
+sat -verify -prove-asserts -show-ports -enable_undef miter4
diff --git a/tests/opt/opt_expr_xnor.ys b/tests/opt/opt_expr_xnor.ys
new file mode 100644
index 000000000..f8ef0d352
--- /dev/null
+++ b/tests/opt/opt_expr_xnor.ys
@@ -0,0 +1,131 @@
+# Single-bit $xnor
+read_verilog -noopt <<EOT
+module gold(input i, output o);
+assign o = 1'bx ~^ i;
+endmodule
+EOT
+select -assert-count 1 t:$xnor
+copy gold coarse
+copy gold fine
+copy gold coarse_keepdc
+copy gold fine_keepdc
+
+cd coarse
+opt_expr
+select -assert-none t:$xnor
+
+cd fine
+simplemap
+opt_expr
+select -assert-none c:t$_XNOR_
+
+cd
+miter -equiv -flatten -make_assert -make_outputs -ignore_gold_x gold coarse miter
+sat -verify -prove-asserts -show-ports -enable_undef miter
+miter -equiv -flatten -make_assert -make_outputs coarse fine miter2
+sat -verify -prove-asserts -show-ports -enable_undef miter2
+
+cd coarse_keepdc
+opt_expr -keepdc
+select -assert-count 1 c:*
+
+cd fine_keepdc
+simplemap
+opt_expr -keepdc
+select -assert-count 1 t:$_XOR_
+
+cd
+miter -equiv -flatten -make_assert -make_outputs gold coarse_keepdc miter3
+sat -verify -prove-asserts -show-ports -enable_undef miter3
+miter -equiv -flatten -make_assert -make_outputs coarse_keepdc fine_keepdc miter4
+sat -verify -prove-asserts -show-ports -enable_undef miter4
+
+
+# Multi-bit $xnor
+design -reset
+read_verilog -noopt <<EOT
+module gold(input i, output [6:0] o);
+assign o = {1'bx, 1'b0, 1'b0, 1'b1, 1'bx, 1'b1, i} ~^ {7{i}};
+endmodule
+EOT
+select -assert-count 1 t:$xnor
+copy gold coarse
+copy gold fine
+copy gold coarse_keepdc
+copy gold fine_keepdc
+
+cd coarse
+opt_expr -fine
+select -assert-none t:$xnor
+
+cd fine
+simplemap
+opt_expr
+select -assert-none t:$_XNOR_
+
+cd
+miter -equiv -flatten -make_assert -make_outputs -ignore_gold_x gold coarse miter
+sat -verify -prove-asserts -show-ports -enable_undef miter
+miter -equiv -flatten -make_assert -make_outputs coarse fine miter2
+sat -verify -prove-asserts -show-ports -enable_undef miter2
+
+cd coarse_keepdc
+opt_expr -keepdc -fine
+select -assert-count 1 t:$xnor
+
+cd fine_keepdc
+simplemap
+opt_expr -keepdc
+select -assert-count 0 c:$_XOR_
+
+cd
+miter -equiv -flatten -make_assert -make_outputs gold coarse_keepdc miter3
+sat -verify -prove-asserts -show-ports -enable_undef miter3
+miter -equiv -flatten -make_assert -make_outputs coarse_keepdc fine_keepdc miter4
+sat -verify -prove-asserts -show-ports -enable_undef miter4
+
+
+# Single-bit $xnor extension
+design -reset
+read_verilog -noopt <<EOT
+module gold(input i, output [1:0] o, p, q);
+assign o = i ~^ i;
+assign p = 1'b0 ~^ i;
+assign q = 1'b1 ~^ i;
+endmodule
+EOT
+select -assert-count 3 t:$xnor
+copy gold coarse
+copy gold fine
+copy gold coarse_keepdc
+copy gold fine_keepdc
+
+cd coarse
+opt_expr -fine
+select -assert-none t:$xnor
+
+cd fine
+simplemap
+opt_expr
+select -assert-none t:$_XNOR_
+
+cd
+miter -equiv -flatten -make_assert -make_outputs -ignore_gold_x gold coarse miter
+sat -verify -prove-asserts -show-ports -enable_undef miter
+miter -equiv -flatten -make_assert -make_outputs coarse fine miter2
+sat -verify -prove-asserts -show-ports -enable_undef miter2
+
+cd coarse_keepdc
+opt_expr -keepdc -fine
+select -assert-count 1 t:$xnor
+
+cd fine_keepdc
+simplemap
+opt_expr -keepdc
+select -assert-count 0 c:$_XNOR_
+
+cd
+miter -equiv -flatten -make_assert -make_outputs gold coarse_keepdc miter3
+sat -verify -prove-asserts -show-ports -enable_undef miter3
+miter -equiv -flatten -make_assert -make_outputs coarse_keepdc fine_keepdc miter4
+sat -verify -prove-asserts -show-ports -enable_undef miter4
diff --git a/tests/opt/opt_expr_xor.ys b/tests/opt/opt_expr_xor.ys
index 21439fd53..a879f3ec9 100644
--- a/tests/opt/opt_expr_xor.ys
+++ b/tests/opt/opt_expr_xor.ys
@@ -50,3 +50,91 @@ assign z = a~^1'b1;
endmodule
EOT
equiv_opt opt_expr
+
+
+# Single-bit $xor
+design -reset
+read_verilog -noopt <<EOT
+module gold(input i, output o);
+assign o = 1'bx ^ i;
+endmodule
+EOT
+select -assert-count 1 t:$xor
+copy gold coarse
+copy gold fine
+copy gold coarse_keepdc
+copy gold fine_keepdc
+
+cd coarse
+opt_expr
+select -assert-none c:*
+
+cd fine
+simplemap
+opt_expr
+select -assert-none c:*
+
+cd
+miter -equiv -flatten -make_assert -make_outputs -ignore_gold_x gold coarse miter
+sat -verify -prove-asserts -show-ports -enable_undef miter
+miter -equiv -flatten -make_assert -make_outputs coarse fine miter2
+sat -verify -prove-asserts -show-ports -enable_undef miter2
+
+cd coarse_keepdc
+opt_expr -keepdc
+select -assert-count 1 c:*
+
+cd fine_keepdc
+simplemap
+opt_expr -keepdc
+select -assert-count 1 c:*
+
+cd
+miter -equiv -flatten -make_assert -make_outputs gold coarse_keepdc miter3
+sat -verify -prove-asserts -show-ports -enable_undef miter3
+miter -equiv -flatten -make_assert -make_outputs coarse_keepdc fine_keepdc miter4
+sat -verify -prove-asserts -show-ports -enable_undef miter4
+
+
+# Multi-bit $xor
+design -reset
+read_verilog -noopt <<EOT
+module gold(input i, output [6:0] o);
+assign o = {1'bx, 1'b0, 1'b0, 1'b1, 1'bx, 1'b1, i} ^ {7{i}};
+endmodule
+EOT
+select -assert-count 1 t:$xor
+copy gold coarse
+copy gold fine
+copy gold coarse_keepdc
+copy gold fine_keepdc
+
+cd coarse
+opt_expr -fine
+select -assert-count 0 t:$xor
+
+cd fine
+simplemap
+opt_expr
+select -assert-none t:$_XOR_
+
+cd
+miter -equiv -flatten -make_assert -make_outputs -ignore_gold_x gold coarse miter
+sat -verify -prove-asserts -show-ports -enable_undef miter
+miter -equiv -flatten -make_assert -make_outputs coarse fine miter2
+sat -verify -prove-asserts -show-ports -enable_undef miter2
+
+cd coarse_keepdc
+opt_expr -keepdc -fine
+select -assert-count 1 t:$xor
+
+cd fine_keepdc
+simplemap
+opt_expr -keepdc
+select -assert-count 3 t:$_XOR_
+
+cd
+miter -equiv -flatten -make_assert -make_outputs gold coarse_keepdc miter3
+sat -verify -prove-asserts -show-ports -enable_undef miter3
+miter -equiv -flatten -make_assert -make_outputs coarse_keepdc fine_keepdc miter4
+sat -verify -prove-asserts -show-ports -enable_undef miter4
generated by cgit v1.2.3 (git 2.25.1) at 2025-01-28 04:14:38 +0000