diff --git a/passes/opt/opt_expr.cc b/passes/opt/opt_expr.cc
index b2dc9a448..90bda6bd3 100644
--- a/passes/opt/opt_expr.cc
+++ b/passes/opt/opt_expr.cc
@@ -641,7 +641,8 @@ void replace_const_cells(RTLIL::Design *design, RTLIL::Module *module, bool cons
 				}
 			}
 
-			if (cell->type.in("$add", "$sub")) {
+			if (cell->type.in("$add", "$sub"))
+			{
 				RTLIL::SigSpec sig_a = assign_map(cell->getPort("\\A"));
 				RTLIL::SigSpec sig_b = assign_map(cell->getPort("\\B"));
 				RTLIL::SigSpec sig_y = cell->getPort("\\Y");
@@ -665,6 +666,53 @@ void replace_const_cells(RTLIL::Design *design, RTLIL::Module *module, bool cons
 					did_something = true;
 				}
 			}
+
+			if (cell->type == "$alu")
+			{
+				RTLIL::SigSpec sig_a = assign_map(cell->getPort("\\A"));
+				RTLIL::SigSpec sig_b = assign_map(cell->getPort("\\B"));
+				RTLIL::SigBit sig_ci = assign_map(cell->getPort("\\CI"));
+				RTLIL::SigBit sig_bi = assign_map(cell->getPort("\\BI"));
+				RTLIL::SigSpec sig_x = cell->getPort("\\X");
+				RTLIL::SigSpec sig_y = cell->getPort("\\Y");
+				RTLIL::SigSpec sig_co = cell->getPort("\\CO");
+
+				if (sig_ci.wire || sig_bi.wire)
+					goto next_cell;
+
+				bool sub = (sig_ci == State::S1 && sig_bi == State::S1);
+
+				// If not a subtraction, yet there is a carry or B is inverted
+				//   then no optimisation is possible as carry will not be constant
+				if (!sub && (sig_ci != State::S0 || sig_bi != State::S0))
+					goto next_cell;
+
+				int i;
+				for (i = 0; i < GetSize(sig_y); i++) {
+					if (sig_b.at(i, State::Sx) == State::S0 && sig_a.at(i, State::Sx) != State::Sx) {
+						module->connect(sig_x[i], sub ? module->Not(NEW_ID, sig_a[i]).as_bit() : sig_a[i]);
+						module->connect(sig_y[i], sig_a[i]);
+						module->connect(sig_co[i], sub ? State::S1 : State::S0);
+					}
+					else if (!sub && sig_a.at(i, State::Sx) == State::S0 && sig_b.at(i, State::Sx) != State::Sx) {
+						module->connect(sig_x[i], sig_b[i]);
+						module->connect(sig_y[i], sig_b[i]);
+						module->connect(sig_co[i], State::S0);
+					}
+					else
+						break;
+				}
+				if (i > 0) {
+					cover("opt.opt_expr.fine.$alu");
+					cell->setPort("\\A", sig_a.extract_end(i));
+					cell->setPort("\\B", sig_b.extract_end(i));
+					cell->setPort("\\X", sig_x.extract_end(i));
+					cell->setPort("\\Y", sig_y.extract_end(i));
+					cell->setPort("\\CO", sig_co.extract_end(i));
+					cell->fixup_parameters();
+					did_something = true;
+				}
+			}
 		}
 
 		if (cell->type.in("$reduce_xor", "$reduce_xnor", "$shift", "$shiftx", "$shl", "$shr", "$sshl", "$sshr",
diff --git a/tests/various/opt_expr.ys b/tests/various/opt_expr.ys
index 0c61ac881..f0306efa1 100644
--- a/tests/various/opt_expr.ys
+++ b/tests/various/opt_expr.ys
@@ -5,144 +5,219 @@ module opt_expr_add_test(input [3:0] i, input [7:0] j, output [8:0] o);
 endmodule
 EOT
 
-hierarchy -auto-top
-proc
-design -save gold
+equiv_opt -assert opt_expr -fine
+design -load postopt
 
-opt_expr -fine
-wreduce
-
-select -assert-count 1 t:$add r:A_WIDTH=4 r:B_WIDTH=4 r:Y_WIDTH=5 %i %i %i
-
-design -stash gate
-
-design -import gold -as gold
-design -import gate -as gate
-
-miter -equiv -flatten -make_assert -make_outputs gold gate miter
-sat -verify -prove-asserts -show-ports miter
+select -assert-count 1 t:$add r:A_WIDTH=5 r:B_WIDTH=4 r:Y_WIDTH=5 %i %i %i
 
 ##########
 
+# alumacc version of above
+design -reset
+read_verilog <<EOT
+module opt_expr_add_test(input [3:0] i, input [7:0] j, output [8:0] o);
+    assign o = (i << 4) + j;
+endmodule
+EOT
+
+alumacc
+equiv_opt -assert opt_expr -fine
+design -load postopt
+
+select -assert-count 1 t:$alu r:A_WIDTH=4 r:B_WIDTH=5 r:Y_WIDTH=5 %i %i %i
+
+##########
+
+design -reset
 read_verilog <<EOT
 module opt_expr_add_signed_test(input signed [3:0] i, input signed [7:0] j, output signed [8:0] o);
     assign o = (i << 4) + j;
 endmodule
 EOT
 
-hierarchy -auto-top
-proc
-design -save gold
+equiv_opt -assert opt_expr -fine
+design -load postopt
 
-opt_expr -fine
-wreduce
-
-select -assert-count 1 t:$add r:A_WIDTH=4 r:B_WIDTH=4 r:Y_WIDTH=5 %i %i %i
-
-design -stash gate
-
-design -import gold -as gold
-design -import gate -as gate
-
-miter -equiv -flatten -make_assert -make_outputs gold gate miter
-sat -verify -prove-asserts -show-ports miter
+select -assert-count 1 t:$add r:A_WIDTH=5 r:B_WIDTH=4 r:Y_WIDTH=5 %i %i %i
 
 ##########
 
+# alumacc version of above
+design -reset
+read_verilog <<EOT
+module opt_expr_add_signed_test(input signed [3:0] i, input signed [7:0] j, output signed [8:0] o);
+    assign o = (i << 4) + j;
+endmodule
+EOT
+
+alumacc
+equiv_opt -assert opt_expr -fine
+design -load postopt
+
+select -assert-count 1 t:$alu r:A_WIDTH=4 r:B_WIDTH=5 r:Y_WIDTH=5 %i %i %i
+
+##########
+
+design -reset
 read_verilog <<EOT
 module opt_expr_sub_test1(input [3:0] i, input [7:0] j, output [8:0] o);
     assign o = j - (i << 4);
 endmodule
 EOT
 
-hierarchy -auto-top
-proc
-design -save gold
+equiv_opt -assert opt_expr -fine
+design -load postopt
 
-opt_expr -fine
-wreduce
-
-select -assert-count 1 t:$sub r:A_WIDTH=4 r:B_WIDTH=4 r:Y_WIDTH=5 %i %i %i
-
-design -stash gate
-
-design -import gold -as gold
-design -import gate -as gate
-
-miter -equiv -flatten -make_assert -make_outputs gold gate miter
-sat -verify -prove-asserts -show-ports miter
+select -assert-count 1 t:$sub r:A_WIDTH=4 r:B_WIDTH=5 r:Y_WIDTH=5 %i %i %i
 
 ##########
 
+# alumacc version of above
+design -reset
+read_verilog <<EOT
+module opt_expr_sub_test1(input [3:0] i, input [7:0] j, output [8:0] o);
+    assign o = j - (i << 4);
+endmodule
+EOT
+
+alumacc
+equiv_opt -assert opt_expr -fine
+design -load postopt
+
+dump
+select -assert-count 1 t:$alu r:A_WIDTH=4 r:B_WIDTH=5 r:Y_WIDTH=5 %i %i %i
+
+##########
+
+design -reset
 read_verilog <<EOT
 module opt_expr_sub_signed_test1(input signed [3:0] i, input signed [7:0] j, output signed [8:0] o);
     assign o = j - (i << 4);
 endmodule
 EOT
 
-hierarchy -auto-top
-proc
-design -save gold
+equiv_opt -assert opt_expr -fine
+design -load postopt
 
-opt_expr -fine
-wreduce
-
-select -assert-count 1 t:$sub r:A_WIDTH=4 r:B_WIDTH=4 r:Y_WIDTH=5 %i %i %i
-
-design -stash gate
-
-design -import gold -as gold
-design -import gate -as gate
-
-miter -equiv -flatten -make_assert -make_outputs gold gate miter
-sat -verify -prove-asserts -show-ports miter
+select -assert-count 1 t:$sub r:A_WIDTH=4 r:B_WIDTH=5 r:Y_WIDTH=5 %i %i %i
 
 ##########
 
+# alumacc version of above
+design -reset
+read_verilog <<EOT
+module opt_expr_sub_signed_test1(input signed [3:0] i, input signed [7:0] j, output signed [8:0] o);
+    assign o = j - (i << 4);
+endmodule
+EOT
+
+alumacc
+equiv_opt -assert opt_expr -fine
+design -load postopt
+
+select -assert-count 1 t:$alu r:A_WIDTH=4 r:B_WIDTH=5 r:Y_WIDTH=5 %i %i %i
+
+##########
+
+design -reset
 read_verilog <<EOT
 module opt_expr_sub_test2(input [3:0] i, input [7:0] j, output [8:0] o);
     assign o = (i << 4) - j;
 endmodule
 EOT
 
-hierarchy -auto-top
-proc
-design -save gold
+equiv_opt -assert opt_expr -fine
+design -load postopt
 
-opt_expr -fine
-wreduce
-
-select -assert-count 1 t:$sub r:A_WIDTH=8 r:B_WIDTH=8 r:Y_WIDTH=9 %i %i %i
-
-design -stash gate
-
-design -import gold -as gold
-design -import gate -as gate
-
-miter -equiv -flatten -make_assert -make_outputs gold gate miter
-sat -verify -prove-asserts -show-ports miter
+select -assert-count 1 t:$sub r:A_WIDTH=9 r:B_WIDTH=8 r:Y_WIDTH=9 %i %i %i
 
 ##########
 
+# alumacc version of above
+design -reset
+read_verilog <<EOT
+module opt_expr_sub_test2(input [3:0] i, input [7:0] j, output [8:0] o);
+    assign o = (i << 4) - j;
+endmodule
+EOT
+
+alumacc
+opt_expr -fine
+equiv_opt -assert opt_expr -fine
+design -load postopt
+
+select -assert-count 1 t:$alu r:A_WIDTH=9 r:B_WIDTH=8 r:Y_WIDTH=9 %i %i %i
+
+##########
+
+design -reset
 read_verilog <<EOT
 module opt_expr_sub_test4(input [3:0] i, output [8:0] o);
     assign o = 5'b00010 - i;
 endmodule
 EOT
 
-hierarchy -auto-top
-proc
-design -save gold
-
-opt_expr -fine
 wreduce
+equiv_opt -assert opt_expr -fine
+design -load postopt
 
 select -assert-count 1 t:$sub r:A_WIDTH=2 r:B_WIDTH=4 r:Y_WIDTH=5 %i %i %i
 
-design -stash gate
+##########
 
-design -import gold -as gold
-design -import gate -as gate
+# alumacc version of above
+design -reset
+read_verilog <<EOT
+module opt_expr_sub_test4(input [3:0] i, output [8:0] o);
+    assign o = 5'b00010 - i;
+endmodule
+EOT
 
-miter -equiv -flatten -make_assert -make_outputs gold gate miter
-sat -verify -prove-asserts -show-ports miter
+wreduce
+alumacc
+equiv_opt -assert opt_expr -fine
+design -load postopt
+
+select -assert-count 1 t:$alu r:A_WIDTH=2 r:B_WIDTH=4 r:Y_WIDTH=5 %i %i %i
+
+###########
+
+design -reset
+read_verilog -icells <<EOT
+module opt_expr_alu_test_ci0_bi0(input [7:0] a, input [3:0] b, output [8:0] x, y, co);
+    \$alu #(.A_SIGNED(0), .B_SIGNED(0), .A_WIDTH(8), .B_WIDTH(8), .Y_WIDTH(9)) alu (.A(a), .B({b, 4'b0000}), .CI(1'b0), .BI(1'b0), .X(x), .Y(y), .CO(co));
+endmodule
+EOT
+check
+
+equiv_opt -assert opt_expr -fine
+design -load postopt
+select -assert-count 1 t:$alu r:A_WIDTH=4 r:B_WIDTH=4 r:Y_WIDTH=5 %i %i %i
+
+###########
+
+design -reset
+read_verilog -icells <<EOT
+module opt_expr_alu_test_ci1_bi1(input [7:0] a, input [3:0] b, output [8:0] x, y, co);
+    \$alu #(.A_SIGNED(0), .B_SIGNED(0), .A_WIDTH(8), .B_WIDTH(8), .Y_WIDTH(9)) alu (.A(a), .B({b, 4'b0000}), .CI(1'b1), .BI(1'b1), .X(x), .Y(y), .CO(co));
+endmodule
+EOT
+check
+
+equiv_opt opt_expr -fine
+design -load postopt
+select -assert-count 1 t:$alu r:A_WIDTH=4 r:B_WIDTH=4 r:Y_WIDTH=5 %i %i %i
+
+###########
+
+design -reset
+read_verilog -icells <<EOT
+module opt_expr_alu_test_ci0_bi1(input [7:0] a, input [3:0] b, output [8:0] x, y, co);
+    \$alu #(.A_SIGNED(0), .B_SIGNED(0), .A_WIDTH(8), .B_WIDTH(8), .Y_WIDTH(9)) alu (.A(a), .B({b, 4'b0000}), .CI(1'b0), .BI(1'b1), .X(x), .Y(y), .CO(co));
+endmodule
+EOT
+check
+
+equiv_opt opt_expr -fine
+design -load postopt
+select -assert-count 1 t:$alu r:A_WIDTH=8 r:B_WIDTH=8 r:Y_WIDTH=9 %i %i %i