Merge pull request #1449 from pepijndevos/gowin

Improvements for gowin support
diff --git a/backends/verilog/verilog_backend.cc b/backends/verilog/verilog_backend.cc
index 24e397b..54d0f61 100644
--- a/backends/verilog/verilog_backend.cc
+++ b/backends/verilog/verilog_backend.cc
@@ -33,11 +33,11 @@
 USING_YOSYS_NAMESPACE
 PRIVATE_NAMESPACE_BEGIN
 
-bool verbose, norename, noattr, attr2comment, noexpr, nodec, nohex, nostr, defparam, decimal, siminit;
-int auto_name_counter, auto_name_offset, auto_name_digits;
+bool verbose, norename, noattr, attr2comment, noexpr, nodec, nohex, nostr, extmem, defparam, decimal, siminit;
+int auto_name_counter, auto_name_offset, auto_name_digits, extmem_counter;
 std::map<RTLIL::IdString, int> auto_name_map;
 std::set<RTLIL::IdString> reg_wires, reg_ct;
-std::string auto_prefix;
+std::string auto_prefix, extmem_prefix;
 
 RTLIL::Module *active_module;
 dict<RTLIL::SigBit, RTLIL::State> active_initdata;
@@ -1069,14 +1069,64 @@
 		f << stringf("%s" "reg [%d:%d] %s [%d:%d];\n", indent.c_str(), width-1, 0, mem_id.c_str(), size+offset-1, offset);
 		if (use_init)
 		{
-			f << stringf("%s" "initial begin\n", indent.c_str());
-			for (int i=0; i<size; i++)
+			if (extmem)
 			{
-				f << stringf("%s" "  %s[%d] = ", indent.c_str(), mem_id.c_str(), i);
-				dump_const(f, cell->parameters["\\INIT"].extract(i*width, width));
-				f << stringf(";\n");
+				std::string extmem_filename = stringf("%s-%d.mem", extmem_prefix.c_str(), extmem_counter++);
+
+				std::string extmem_filename_esc;
+				for (auto c : extmem_filename)
+				{
+					if (c == '\n')
+						extmem_filename_esc += "\\n";
+					else if (c == '\t')
+						extmem_filename_esc += "\\t";
+					else if (c < 32)
+						extmem_filename_esc += stringf("\\%03o", c);
+					else if (c == '"')
+						extmem_filename_esc += "\\\"";
+					else if (c == '\\')
+						extmem_filename_esc += "\\\\";
+					else
+						extmem_filename_esc += c;
+				}
+				f << stringf("%s" "initial $readmemb(\"%s\", %s);\n", indent.c_str(), extmem_filename_esc.c_str(), mem_id.c_str());
+
+				std::ofstream extmem_f(extmem_filename, std::ofstream::trunc);
+				if (extmem_f.fail())
+					log_error("Can't open file `%s' for writing: %s\n", extmem_filename.c_str(), strerror(errno));
+				else
+				{
+					for (int i=0; i<size; i++)
+					{
+						RTLIL::Const element = cell->parameters["\\INIT"].extract(i*width, width);
+						for (int j=0; j<element.size(); j++)
+						{
+							switch (element[element.size()-j-1])
+							{
+								case State::S0: extmem_f << '0'; break;
+								case State::S1: extmem_f << '1'; break;
+								case State::Sx: extmem_f << 'x'; break;
+								case State::Sz: extmem_f << 'z'; break;
+								case State::Sa: extmem_f << '_'; break;
+								case State::Sm: log_error("Found marker state in final netlist.");
+							}
+						}
+						extmem_f << '\n';
+					}
+				}
+
 			}
-			f << stringf("%s" "end\n", indent.c_str());
+			else
+			{
+				f << stringf("%s" "initial begin\n", indent.c_str());
+				for (int i=0; i<size; i++)
+				{
+					f << stringf("%s" "  %s[%d] = ", indent.c_str(), mem_id.c_str(), i);
+					dump_const(f, cell->parameters["\\INIT"].extract(i*width, width));
+					f << stringf(";\n");
+				}
+				f << stringf("%s" "end\n", indent.c_str());
+			}
 		}
 
 		// create a map : "edge clk" -> expressions within that clock domain
@@ -1777,8 +1827,16 @@
 		log("        deactivates this feature and instead will write string constants\n");
 		log("        as binary numbers.\n");
 		log("\n");
+		log("    -extmem\n");
+		log("        instead of initializing memories using assignments to individual\n");
+		log("        elements, use the '$readmemh' function to read initialization data\n");
+		log("        from a file. This data is written to a file named by appending\n");
+		log("        a sequential index to the Verilog filename and replacing the extension\n");
+		log("        with '.mem', e.g. 'write_verilog -extmem foo.v' writes 'foo-1.mem',\n");
+		log("        'foo-2.mem' and so on.\n");
+		log("\n");
 		log("    -defparam\n");
-		log("        Use 'defparam' statements instead of the Verilog-2001 syntax for\n");
+		log("        use 'defparam' statements instead of the Verilog-2001 syntax for\n");
 		log("        cell parameters.\n");
 		log("\n");
 		log("    -blackboxes\n");
@@ -1812,6 +1870,7 @@
 		nodec = false;
 		nohex = false;
 		nostr = false;
+		extmem = false;
 		defparam = false;
 		decimal = false;
 		siminit = false;
@@ -1885,6 +1944,11 @@
 				nostr = true;
 				continue;
 			}
+			if (arg == "-extmem") {
+				extmem = true;
+				extmem_counter = 1;
+				continue;
+			}
 			if (arg == "-defparam") {
 				defparam = true;
 				continue;
@@ -1912,6 +1976,12 @@
 			break;
 		}
 		extra_args(f, filename, args, argidx);
+		if (extmem)
+		{
+			if (filename.empty())
+				log_cmd_error("Option -extmem must be used with a filename.\n");
+			extmem_prefix = filename.substr(0, filename.rfind('.'));
+		}
 
 		design->sort();
 
diff --git a/passes/opt/wreduce.cc b/passes/opt/wreduce.cc
index c02c355..04b882d 100644
--- a/passes/opt/wreduce.cc
+++ b/passes/opt/wreduce.cc
@@ -143,13 +143,18 @@
 
 		SigSpec sig_d = mi.sigmap(cell->getPort(ID(D)));
 		SigSpec sig_q = mi.sigmap(cell->getPort(ID(Q)));
-		Const initval;
+		bool is_adff = (cell->type == ID($adff));
+		Const initval, arst_value;
 
 		int width_before = GetSize(sig_q);
 
 		if (width_before == 0)
 			return;
 
+		if (cell->parameters.count(ID(ARST_VALUE))) {
+			arst_value = cell->parameters[ID(ARST_VALUE)];
+		}
+
 		bool zero_ext = sig_d[GetSize(sig_d)-1] == State::S0;
 		bool sign_ext = !zero_ext;
 
@@ -163,7 +168,8 @@
 
 		for (int i = GetSize(sig_q)-1; i >= 0; i--)
 		{
-			if (zero_ext && sig_d[i] == State::S0 && (initval[i] == State::S0 || initval[i] == State::Sx)) {
+			if (zero_ext && sig_d[i] == State::S0 && (initval[i] == State::S0 || initval[i] == State::Sx) &&
+					(!is_adff || i >= GetSize(arst_value) || arst_value[i] == State::S0 || arst_value[i] == State::Sx)) {
 				module->connect(sig_q[i], State::S0);
 				remove_init_bits.insert(sig_q[i]);
 				sig_d.remove(i);
@@ -171,7 +177,8 @@
 				continue;
 			}
 
-			if (sign_ext && i > 0 && sig_d[i] == sig_d[i-1] && initval[i] == initval[i-1]) {
+			if (sign_ext && i > 0 && sig_d[i] == sig_d[i-1] && initval[i] == initval[i-1] &&
+					(!is_adff || i >= GetSize(arst_value) || arst_value[i] == arst_value[i-1])) {
 				module->connect(sig_q[i], sig_q[i-1]);
 				remove_init_bits.insert(sig_q[i]);
 				sig_d.remove(i);
@@ -214,7 +221,6 @@
 
 		// Narrow ARST_VALUE parameter to new size.
 		if (cell->parameters.count(ID(ARST_VALUE))) {
-			Const arst_value = cell->getParam(ID(ARST_VALUE));
 			arst_value.bits.resize(GetSize(sig_q));
 			cell->setParam(ID(ARST_VALUE), arst_value);
 		}
diff --git a/passes/pmgen/xilinx_dsp.pmg b/passes/pmgen/xilinx_dsp.pmg
index 604aa22..0ba5290 100644
--- a/passes/pmgen/xilinx_dsp.pmg
+++ b/passes/pmgen/xilinx_dsp.pmg
@@ -98,16 +98,16 @@
 	if (param(dsp, \USE_MULT, Const("MULTIPLY")).decode_string() == "MULTIPLY") {
 		// Only care about those bits that are used
 		int i;
-		for (i = 0; i < GetSize(P); i++) {
-			if (nusers(P[i]) <= 1)
+		for (i = GetSize(P)-1; i >= 0; i--)
+			if (nusers(P[i]) > 1)
 				break;
-			sigM.append(P[i]);
-		}
+		i++;
 		log_assert(nusers(P.extract_end(i)) <= 1);
 		// This sigM could have no users if downstream sinks (e.g. $add) is
 		//   narrower than $mul result, for example
-		if (sigM.empty())
+		if (i == 0)
 			reject;
+		sigM = P.extract(0, i);
 	}
 	else
 		sigM = P;
@@ -460,6 +460,8 @@
 
 code
 	dff = nullptr;
+	if (GetSize(argQ) == 0)
+		reject;
 	for (const auto &c : argQ.chunks()) {
 		// Abandon matches when 'Q' is a constant
 		if (!c.wire)
diff --git a/passes/pmgen/xilinx_dsp_CREG.pmg b/passes/pmgen/xilinx_dsp_CREG.pmg
index a570430..5cd3416 100644
--- a/passes/pmgen/xilinx_dsp_CREG.pmg
+++ b/passes/pmgen/xilinx_dsp_CREG.pmg
@@ -63,12 +63,12 @@
 	if (param(dsp, \USE_MULT, Const("MULTIPLY")).decode_string() == "MULTIPLY") {
 		// Only care about those bits that are used
 		int i;
-		for (i = 0; i < GetSize(P); i++) {
-			if (nusers(P[i]) <= 1)
+		for (i = GetSize(P)-1; i >= 0; i--)
+			if (nusers(P[i]) > 1)
 				break;
-			sigP.append(P[i]);
-		}
+		i++;
 		log_assert(nusers(P.extract_end(i)) <= 1);
+		sigP = P.extract(0, i);
 	}
 	else
 		sigP = P;
diff --git a/passes/techmap/extract_fa.cc b/passes/techmap/extract_fa.cc
index 29700c3..9f3bb52 100644
--- a/passes/techmap/extract_fa.cc
+++ b/passes/techmap/extract_fa.cc
@@ -262,10 +262,14 @@
 			pool<SigBit> new_leaves = leaves;
 
 			new_leaves.erase(bit);
-			if (cell->hasPort(ID::A)) new_leaves.insert(sigmap(SigBit(cell->getPort(ID::A))));
-			if (cell->hasPort(ID::B)) new_leaves.insert(sigmap(SigBit(cell->getPort(ID::B))));
-			if (cell->hasPort(ID(C))) new_leaves.insert(sigmap(SigBit(cell->getPort(ID(C)))));
-			if (cell->hasPort(ID(D))) new_leaves.insert(sigmap(SigBit(cell->getPort(ID(D)))));
+			for (auto port : {ID::A, ID::B, ID(C), ID(D)}) {
+				if (!cell->hasPort(port))
+					continue;
+				auto bit = sigmap(SigBit(cell->getPort(port)));
+				if (!bit.wire)
+					continue;
+				new_leaves.insert(bit);
+			}
 
 			if (GetSize(new_leaves) > maxbreadth)
 				continue;
diff --git a/techlibs/xilinx/cells_sim.v b/techlibs/xilinx/cells_sim.v
index 03985b1..5faddcd 100644
--- a/techlibs/xilinx/cells_sim.v
+++ b/techlibs/xilinx/cells_sim.v
@@ -581,6 +581,515 @@
   endgenerate
 endmodule
 
+// DSP
+
+// Virtex 2, Virtex 2 Pro, Spartan 3.
+
+// Asynchronous mode.
+
+module MULT18X18 (
+    input signed [17:0] A,
+    input signed [17:0] B,
+    output signed [35:0] P
+);
+
+assign P = A * B;
+
+endmodule
+
+// Synchronous mode.
+
+module MULT18X18S (
+    input signed [17:0] A,
+    input signed [17:0] B,
+    output reg signed [35:0] P,
+    (* clkbuf_sink *)
+    input C,
+    input CE,
+    input R
+);
+
+always @(posedge C)
+	if (R)
+		P <= 0;
+	else if (CE)
+		P <= A * B;
+
+endmodule
+
+// Spartan 3E, Spartan 3A.
+
+module MULT18X18SIO (
+    input signed [17:0] A,
+    input signed [17:0] B,
+    output signed [35:0] P,
+    (* clkbuf_sink *)
+    input CLK,
+    input CEA,
+    input CEB,
+    input CEP,
+    input RSTA,
+    input RSTB,
+    input RSTP,
+    input signed [17:0] BCIN,
+    output signed [17:0] BCOUT
+);
+
+parameter integer AREG = 1;
+parameter integer BREG = 1;
+parameter B_INPUT = "DIRECT";
+parameter integer PREG = 1;
+
+// The multiplier.
+wire signed [35:0] P_MULT;
+assign P_MULT = A_MULT * B_MULT;
+
+// The cascade output.
+assign BCOUT = B_MULT;
+
+// The B input multiplexer.
+wire signed [17:0] B_MUX;
+assign B_MUX = (B_INPUT == "DIRECT") ? B : BCIN;
+
+// The registers.
+reg signed [17:0] A_REG;
+reg signed [17:0] B_REG;
+reg signed [35:0] P_REG;
+
+initial begin
+	A_REG = 0;
+	B_REG = 0;
+	P_REG = 0;
+end
+
+always @(posedge CLK) begin
+	if (RSTA)
+		A_REG <= 0;
+	else if (CEA)
+		A_REG <= A;
+
+	if (RSTB)
+		B_REG <= 0;
+	else if (CEB)
+		B_REG <= B_MUX;
+
+	if (RSTP)
+		P_REG <= 0;
+	else if (CEP)
+		P_REG <= P_MULT;
+end
+
+// The register enables.
+wire signed [17:0] A_MULT;
+wire signed [17:0] B_MULT;
+assign A_MULT = (AREG == 1) ? A_REG : A;
+assign B_MULT = (BREG == 1) ? B_REG : B_MUX;
+assign P = (PREG == 1) ? P_REG : P_MULT;
+
+endmodule
+
+// Spartan 3A DSP.
+
+module DSP48A (
+    input signed [17:0] A,
+    input signed [17:0] B,
+    input signed [47:0] C,
+    input signed [17:0] D,
+    input signed [47:0] PCIN,
+    input CARRYIN,
+    input [7:0] OPMODE,
+    output signed [47:0] P,
+    output signed [17:0] BCOUT,
+    output signed [47:0] PCOUT,
+    output CARRYOUT,
+    (* clkbuf_sink *)
+    input CLK,
+    input CEA,
+    input CEB,
+    input CEC,
+    input CED,
+    input CEM,
+    input CECARRYIN,
+    input CEOPMODE,
+    input CEP,
+    input RSTA,
+    input RSTB,
+    input RSTC,
+    input RSTD,
+    input RSTM,
+    input RSTCARRYIN,
+    input RSTOPMODE,
+    input RSTP
+);
+
+parameter integer A0REG = 0;
+parameter integer A1REG = 1;
+parameter integer B0REG = 0;
+parameter integer B1REG = 1;
+parameter integer CREG = 1;
+parameter integer DREG = 1;
+parameter integer MREG = 1;
+parameter integer CARRYINREG = 1;
+parameter integer OPMODEREG = 1;
+parameter integer PREG = 1;
+parameter CARRYINSEL = "CARRYIN";
+parameter RSTTYPE = "SYNC";
+
+// This is a strict subset of Spartan 6 -- reuse its model.
+
+DSP48A1 #(
+	.A0REG(A0REG),
+	.A1REG(A1REG),
+	.B0REG(B0REG),
+	.B1REG(B1REG),
+	.CREG(CREG),
+	.DREG(DREG),
+	.MREG(MREG),
+	.CARRYINREG(CARRYINREG),
+	.CARRYOUTREG(0),
+	.OPMODEREG(OPMODEREG),
+	.PREG(PREG),
+	.CARRYINSEL(CARRYINSEL),
+	.RSTTYPE(RSTTYPE)
+) upgrade (
+	.A(A),
+	.B(B),
+	.C(C),
+	.D(D),
+	.PCIN(PCIN),
+	.CARRYIN(CARRYIN),
+	.OPMODE(OPMODE),
+	// M unconnected
+	.P(P),
+	.BCOUT(BCOUT),
+	.PCOUT(PCOUT),
+	.CARRYOUT(CARRYOUT),
+	// CARRYOUTF unconnected
+	.CLK(CLK),
+	.CEA(CEA),
+	.CEB(CEB),
+	.CEC(CEC),
+	.CED(CED),
+	.CEM(CEM),
+	.CECARRYIN(CECARRYIN),
+	.CEOPMODE(CEOPMODE),
+	.CEP(CEP),
+	.RSTA(RSTA),
+	.RSTB(RSTB),
+	.RSTC(RSTC),
+	.RSTD(RSTD),
+	.RSTM(RSTM),
+	.RSTCARRYIN(RSTCARRYIN),
+	.RSTOPMODE(RSTOPMODE),
+	.RSTP(RSTP)
+);
+
+endmodule
+
+// Spartan 6.
+
+module DSP48A1 (
+    input signed [17:0] A,
+    input signed [17:0] B,
+    input signed [47:0] C,
+    input signed [17:0] D,
+    input signed [47:0] PCIN,
+    input CARRYIN,
+    input [7:0] OPMODE,
+    output signed [35:0] M,
+    output signed [47:0] P,
+    output signed [17:0] BCOUT,
+    output signed [47:0] PCOUT,
+    output CARRYOUT,
+    output CARRYOUTF,
+    (* clkbuf_sink *)
+    input CLK,
+    input CEA,
+    input CEB,
+    input CEC,
+    input CED,
+    input CEM,
+    input CECARRYIN,
+    input CEOPMODE,
+    input CEP,
+    input RSTA,
+    input RSTB,
+    input RSTC,
+    input RSTD,
+    input RSTM,
+    input RSTCARRYIN,
+    input RSTOPMODE,
+    input RSTP
+);
+
+parameter integer A0REG = 0;
+parameter integer A1REG = 1;
+parameter integer B0REG = 0;
+parameter integer B1REG = 1;
+parameter integer CREG = 1;
+parameter integer DREG = 1;
+parameter integer MREG = 1;
+parameter integer CARRYINREG = 1;
+parameter integer CARRYOUTREG = 1;
+parameter integer OPMODEREG = 1;
+parameter integer PREG = 1;
+parameter CARRYINSEL = "OPMODE5";
+parameter RSTTYPE = "SYNC";
+
+wire signed [35:0] M_MULT;
+wire signed [47:0] P_IN;
+wire signed [17:0] A0_OUT;
+wire signed [17:0] B0_OUT;
+wire signed [17:0] A1_OUT;
+wire signed [17:0] B1_OUT;
+wire signed [17:0] B1_IN;
+wire signed [47:0] C_OUT;
+wire signed [17:0] D_OUT;
+wire signed [7:0] OPMODE_OUT;
+wire CARRYIN_OUT;
+wire CARRYOUT_IN;
+wire CARRYIN_IN;
+reg signed [47:0] XMUX;
+reg signed [47:0] ZMUX;
+
+// The registers.
+reg signed [17:0] A0_REG;
+reg signed [17:0] A1_REG;
+reg signed [17:0] B0_REG;
+reg signed [17:0] B1_REG;
+reg signed [47:0] C_REG;
+reg signed [17:0] D_REG;
+reg signed [35:0] M_REG;
+reg signed [47:0] P_REG;
+reg [7:0] OPMODE_REG;
+reg CARRYIN_REG;
+reg CARRYOUT_REG;
+
+initial begin
+	A0_REG = 0;
+	A1_REG = 0;
+	B0_REG = 0;
+	B1_REG = 0;
+	C_REG = 0;
+	D_REG = 0;
+	M_REG = 0;
+	P_REG = 0;
+	OPMODE_REG = 0;
+	CARRYIN_REG = 0;
+	CARRYOUT_REG = 0;
+end
+
+generate
+
+if (RSTTYPE == "SYNC") begin
+	always @(posedge CLK) begin
+		if (RSTA) begin
+			A0_REG <= 0;
+			A1_REG <= 0;
+		end else if (CEA) begin
+			A0_REG <= A;
+			A1_REG <= A0_OUT;
+		end
+	end
+
+	always @(posedge CLK) begin
+		if (RSTB) begin
+			B0_REG <= 0;
+			B1_REG <= 0;
+		end else if (CEB) begin
+			B0_REG <= B;
+			B1_REG <= B1_IN;
+		end
+	end
+
+	always @(posedge CLK) begin
+		if (RSTC) begin
+			C_REG <= 0;
+		end else if (CEC) begin
+			C_REG <= C;
+		end
+	end
+
+	always @(posedge CLK) begin
+		if (RSTD) begin
+			D_REG <= 0;
+		end else if (CED) begin
+			D_REG <= D;
+		end
+	end
+
+	always @(posedge CLK) begin
+		if (RSTM) begin
+			M_REG <= 0;
+		end else if (CEM) begin
+			M_REG <= M_MULT;
+		end
+	end
+
+	always @(posedge CLK) begin
+		if (RSTP) begin
+			P_REG <= 0;
+		end else if (CEP) begin
+			P_REG <= P_IN;
+		end
+	end
+
+	always @(posedge CLK) begin
+		if (RSTOPMODE) begin
+			OPMODE_REG <= 0;
+		end else if (CEOPMODE) begin
+			OPMODE_REG <= OPMODE;
+		end
+	end
+
+	always @(posedge CLK) begin
+		if (RSTCARRYIN) begin
+			CARRYIN_REG <= 0;
+			CARRYOUT_REG <= 0;
+		end else if (CECARRYIN) begin
+			CARRYIN_REG <= CARRYIN_IN;
+			CARRYOUT_REG <= CARRYOUT_IN;
+		end
+	end
+end else begin
+	always @(posedge CLK, posedge RSTA) begin
+		if (RSTA) begin
+			A0_REG <= 0;
+			A1_REG <= 0;
+		end else if (CEA) begin
+			A0_REG <= A;
+			A1_REG <= A0_OUT;
+		end
+	end
+
+	always @(posedge CLK, posedge RSTB) begin
+		if (RSTB) begin
+			B0_REG <= 0;
+			B1_REG <= 0;
+		end else if (CEB) begin
+			B0_REG <= B;
+			B1_REG <= B1_IN;
+		end
+	end
+
+	always @(posedge CLK, posedge RSTC) begin
+		if (RSTC) begin
+			C_REG <= 0;
+		end else if (CEC) begin
+			C_REG <= C;
+		end
+	end
+
+	always @(posedge CLK, posedge RSTD) begin
+		if (RSTD) begin
+			D_REG <= 0;
+		end else if (CED) begin
+			D_REG <= D;
+		end
+	end
+
+	always @(posedge CLK, posedge RSTM) begin
+		if (RSTM) begin
+			M_REG <= 0;
+		end else if (CEM) begin
+			M_REG <= M_MULT;
+		end
+	end
+
+	always @(posedge CLK, posedge RSTP) begin
+		if (RSTP) begin
+			P_REG <= 0;
+		end else if (CEP) begin
+			P_REG <= P_IN;
+		end
+	end
+
+	always @(posedge CLK, posedge RSTOPMODE) begin
+		if (RSTOPMODE) begin
+			OPMODE_REG <= 0;
+		end else if (CEOPMODE) begin
+			OPMODE_REG <= OPMODE;
+		end
+	end
+
+	always @(posedge CLK, posedge RSTCARRYIN) begin
+		if (RSTCARRYIN) begin
+			CARRYIN_REG <= 0;
+			CARRYOUT_REG <= 0;
+		end else if (CECARRYIN) begin
+			CARRYIN_REG <= CARRYIN_IN;
+			CARRYOUT_REG <= CARRYOUT_IN;
+		end
+	end
+end
+
+endgenerate
+
+// The register enables.
+assign A0_OUT = (A0REG == 1) ? A0_REG : A;
+assign A1_OUT = (A1REG == 1) ? A1_REG : A0_OUT;
+assign B0_OUT = (B0REG == 1) ? B0_REG : B;
+assign B1_OUT = (B1REG == 1) ? B1_REG : B1_IN;
+assign C_OUT = (CREG == 1) ? C_REG : C;
+assign D_OUT = (DREG == 1) ? D_REG : D;
+assign M = (MREG == 1) ? M_REG : M_MULT;
+assign P = (PREG == 1) ? P_REG : P_IN;
+assign OPMODE_OUT = (OPMODEREG == 1) ? OPMODE_REG : OPMODE;
+assign CARRYIN_OUT = (CARRYINREG == 1) ? CARRYIN_REG : CARRYIN_IN;
+assign CARRYOUT = (CARRYOUTREG == 1) ? CARRYOUT_REG : CARRYOUT_IN;
+assign CARRYOUTF = CARRYOUT;
+
+// The pre-adder.
+wire signed [17:0] PREADDER;
+assign B1_IN = OPMODE_OUT[4] ? PREADDER : B0_OUT;
+assign PREADDER = OPMODE_OUT[6] ? D_OUT - B0_OUT : D_OUT + B0_OUT;
+
+// The multiplier.
+assign M_MULT = A1_OUT * B1_OUT;
+
+// The carry in selection.
+assign CARRYIN_IN = (CARRYINSEL == "OPMODE5") ? OPMODE_OUT[5] : CARRYIN;
+
+// The post-adder inputs.
+always @* begin
+	case (OPMODE_OUT[1:0])
+		2'b00: XMUX <= 0;
+		2'b01: XMUX <= M;
+		2'b10: XMUX <= P;
+		2'b11: XMUX <= {D_OUT[11:0], B1_OUT, A1_OUT};
+		default: XMUX <= 48'hxxxxxxxxxxxx;
+	endcase
+end
+
+always @* begin
+	case (OPMODE_OUT[3:2])
+		2'b00: ZMUX <= 0;
+		2'b01: ZMUX <= PCIN;
+		2'b10: ZMUX <= P;
+		2'b11: ZMUX <= C_OUT;
+		default: ZMUX <= 48'hxxxxxxxxxxxx;
+	endcase
+end
+
+// The post-adder.
+wire signed [48:0] X_EXT;
+wire signed [48:0] Z_EXT;
+assign X_EXT = XMUX;
+assign Z_EXT = ZMUX;
+assign {CARRYOUT_IN, P_IN} = OPMODE_OUT[7] ? (Z_EXT - (X_EXT + CARRYIN_OUT)) : (Z_EXT + X_EXT + CARRYIN_OUT);
+
+// Cascade outputs.
+assign BCOUT = B1_OUT;
+assign PCOUT = P;
+
+endmodule
+
+// TODO: DSP48 (Virtex 4).
+
+// TODO: DSP48E (Virtex 5).
+
+// Virtex 6, Series 7.
+
 module DSP48E1 (
     output [29:0] ACOUT,
     output [17:0] BCOUT,
@@ -1043,3 +1552,5 @@
     endgenerate
 
 endmodule
+
+// TODO: DSP48E2 (Ultrascale).
diff --git a/techlibs/xilinx/cells_xtra.py b/techlibs/xilinx/cells_xtra.py
index ef7ce85..f401ebe 100644
--- a/techlibs/xilinx/cells_xtra.py
+++ b/techlibs/xilinx/cells_xtra.py
@@ -204,11 +204,11 @@
     Cell('URAM288_BASE', port_attrs={'CLK': ['clkbuf_sink']}),
 
     # Multipliers and DSP.
-    Cell('MULT18X18'), # Spartan 3
-    Cell('MULT18X18S', port_attrs={'C': ['clkbuf_sink']}), # Spartan 3
-    Cell('MULT18X18SIO', port_attrs={'CLK': ['clkbuf_sink']}), # Spartan 3E
-    Cell('DSP48A', port_attrs={'CLK': ['clkbuf_sink']}), # Spartan 3A DSP
-    Cell('DSP48A1', port_attrs={'CLK': ['clkbuf_sink']}), # Spartan 6
+    # Cell('MULT18X18'), # Virtex 2, Spartan 3
+    # Cell('MULT18X18S', port_attrs={'C': ['clkbuf_sink']}), # Spartan 3
+    # Cell('MULT18X18SIO', port_attrs={'CLK': ['clkbuf_sink']}), # Spartan 3E
+    # Cell('DSP48A', port_attrs={'CLK': ['clkbuf_sink']}), # Spartan 3A DSP
+    # Cell('DSP48A1', port_attrs={'CLK': ['clkbuf_sink']}), # Spartan 6
     Cell('DSP48', port_attrs={'CLK': ['clkbuf_sink']}), # Virtex 4
     Cell('DSP48E', port_attrs={'CLK': ['clkbuf_sink']}), # Virtex 5
     #Cell('DSP48E1', port_attrs={'CLK': ['clkbuf_sink']}), # Virtex 6 / Series 7
diff --git a/techlibs/xilinx/cells_xtra.v b/techlibs/xilinx/cells_xtra.v
index 72a3b6c..ce0949f 100644
--- a/techlibs/xilinx/cells_xtra.v
+++ b/techlibs/xilinx/cells_xtra.v
@@ -6218,133 +6218,6 @@
     input SLEEP;
 endmodule
 
-module MULT18X18 (...);
-    output [35:0] P;
-    input [17:0] A;
-    input [17:0] B;
-endmodule
-
-module MULT18X18S (...);
-    output [35:0] P;
-    input [17:0] A;
-    input [17:0] B;
-    (* clkbuf_sink *)
-    input C;
-    input CE;
-    input R;
-endmodule
-
-module MULT18X18SIO (...);
-    parameter integer AREG = 1;
-    parameter integer BREG = 1;
-    parameter B_INPUT = "DIRECT";
-    parameter integer PREG = 1;
-    output [17:0] BCOUT;
-    output [35:0] P;
-    input [17:0] A;
-    input [17:0] B;
-    input [17:0] BCIN;
-    input CEA;
-    input CEB;
-    input CEP;
-    (* clkbuf_sink *)
-    input CLK;
-    input RSTA;
-    input RSTB;
-    input RSTP;
-endmodule
-
-module DSP48A (...);
-    parameter integer A0REG = 0;
-    parameter integer A1REG = 1;
-    parameter integer B0REG = 0;
-    parameter integer B1REG = 1;
-    parameter integer CARRYINREG = 1;
-    parameter CARRYINSEL = "CARRYIN";
-    parameter integer CREG = 1;
-    parameter integer DREG = 1;
-    parameter integer MREG = 1;
-    parameter integer OPMODEREG = 1;
-    parameter integer PREG = 1;
-    parameter RSTTYPE = "SYNC";
-    output [17:0] BCOUT;
-    output CARRYOUT;
-    output [47:0] P;
-    output [47:0] PCOUT;
-    input [17:0] A;
-    input [17:0] B;
-    input [47:0] C;
-    input CARRYIN;
-    input CEA;
-    input CEB;
-    input CEC;
-    input CECARRYIN;
-    input CED;
-    input CEM;
-    input CEOPMODE;
-    input CEP;
-    (* clkbuf_sink *)
-    input CLK;
-    input [17:0] D;
-    input [7:0] OPMODE;
-    input [47:0] PCIN;
-    input RSTA;
-    input RSTB;
-    input RSTC;
-    input RSTCARRYIN;
-    input RSTD;
-    input RSTM;
-    input RSTOPMODE;
-    input RSTP;
-endmodule
-
-module DSP48A1 (...);
-    parameter integer A0REG = 0;
-    parameter integer A1REG = 1;
-    parameter integer B0REG = 0;
-    parameter integer B1REG = 1;
-    parameter integer CARRYINREG = 1;
-    parameter integer CARRYOUTREG = 1;
-    parameter CARRYINSEL = "OPMODE5";
-    parameter integer CREG = 1;
-    parameter integer DREG = 1;
-    parameter integer MREG = 1;
-    parameter integer OPMODEREG = 1;
-    parameter integer PREG = 1;
-    parameter RSTTYPE = "SYNC";
-    output [17:0] BCOUT;
-    output CARRYOUT;
-    output CARRYOUTF;
-    output [35:0] M;
-    output [47:0] P;
-    output [47:0] PCOUT;
-    input [17:0] A;
-    input [17:0] B;
-    input [47:0] C;
-    input CARRYIN;
-    input CEA;
-    input CEB;
-    input CEC;
-    input CECARRYIN;
-    input CED;
-    input CEM;
-    input CEOPMODE;
-    input CEP;
-    (* clkbuf_sink *)
-    input CLK;
-    input [17:0] D;
-    input [7:0] OPMODE;
-    input [47:0] PCIN;
-    input RSTA;
-    input RSTB;
-    input RSTC;
-    input RSTCARRYIN;
-    input RSTD;
-    input RSTM;
-    input RSTOPMODE;
-    input RSTP;
-endmodule
-
 module DSP48 (...);
     parameter integer AREG = 1;
     parameter integer BREG = 1;
diff --git a/tests/various/bug1462.ys b/tests/various/bug1462.ys
new file mode 100644
index 0000000..15cab51
--- /dev/null
+++ b/tests/various/bug1462.ys
@@ -0,0 +1,11 @@
+read_verilog << EOF
+module top(...);
+input wire [31:0] A;
+output wire [31:0] P;
+
+assign P = A * 32'h12300000;
+
+endmodule
+EOF
+
+synth_xilinx
diff --git a/tests/various/bug1480.ys b/tests/various/bug1480.ys
new file mode 100644
index 0000000..84faea0
--- /dev/null
+++ b/tests/various/bug1480.ys
@@ -0,0 +1,18 @@
+read_verilog << EOF
+module top(...);
+
+input signed [17:0] A;
+input signed [17:0] B;
+output X;
+output Y;
+
+wire [35:0] P;
+assign P = A * B;
+
+assign X = P[0];
+assign Y = P[35];
+
+endmodule
+EOF
+
+synth_xilinx
diff --git a/tests/various/bug1496.ys b/tests/various/bug1496.ys
new file mode 100644
index 0000000..d050161
--- /dev/null
+++ b/tests/various/bug1496.ys
@@ -0,0 +1,13 @@
+read_ilang << EOF
+module \top
+  wire input 1 \A
+  wire output 2 \Y
+  cell $_AND_ \sub
+    connect \A \A
+    connect \B 1'0
+    connect \Y \Y
+  end
+end
+EOF
+
+extract_fa