Merge pull request #1359 from YosysHQ/xc7dsp

DSP inference for Xilinx (improved for ice40, initial support for ecp5)

12 files changed, 2498 insertions, 229 deletions

diff --git a/passes/pmgen/.gitignore b/passes/pmgen/.gitignore
index 6b319b8c3..e52f3282f 100644
--- a/passes/pmgen/.gitignore
+++ b/passes/pmgen/.gitignore
@@ -1 +1 @@
-/*_pm.h
\ No newline at end of file
+/*_pm.h
diff --git a/passes/pmgen/Makefile.inc b/passes/pmgen/Makefile.inc
index 98691d0fe..366c37943 100644
--- a/passes/pmgen/Makefile.inc
+++ b/passes/pmgen/Makefile.inc
@@ -21,6 +21,14 @@ $(eval $(call add_extra_objs,passes/pmgen/ice40_wrapcarry_pm.h))
 
 # --------------------------------------
 
+OBJS += passes/pmgen/xilinx_dsp.o
+passes/pmgen/xilinx_dsp.o: passes/pmgen/xilinx_dsp_pm.h passes/pmgen/xilinx_dsp_CREG_pm.h passes/pmgen/xilinx_dsp_cascade_pm.h
+$(eval $(call add_extra_objs,passes/pmgen/xilinx_dsp_pm.h))
+$(eval $(call add_extra_objs,passes/pmgen/xilinx_dsp_CREG_pm.h))
+$(eval $(call add_extra_objs,passes/pmgen/xilinx_dsp_cascade_pm.h))
+
+# --------------------------------------
+
 OBJS += passes/pmgen/peepopt.o
 passes/pmgen/peepopt.o: passes/pmgen/peepopt_pm.h
 $(eval $(call add_extra_objs,passes/pmgen/peepopt_pm.h))
diff --git a/passes/pmgen/ice40_dsp.cc b/passes/pmgen/ice40_dsp.cc
index 16bfe537f..f60e67158 100644
--- a/passes/pmgen/ice40_dsp.cc
+++ b/passes/pmgen/ice40_dsp.cc
@@ -29,19 +29,19 @@ void create_ice40_dsp(ice40_dsp_pm &pm)
 {
 	auto &st = pm.st_ice40_dsp;
 
-#if 0
-	log("\n");
-	log("ffA:   %s\n", log_id(st.ffA, "--"));
-	log("ffB:   %s\n", log_id(st.ffB, "--"));
-	log("mul:   %s\n", log_id(st.mul, "--"));
-	log("ffY:   %s\n", log_id(st.ffY, "--"));
-	log("addAB: %s\n", log_id(st.addAB, "--"));
-	log("muxAB: %s\n", log_id(st.muxAB, "--"));
-	log("ffS:   %s\n", log_id(st.ffS, "--"));
-#endif
-
 	log("Checking %s.%s for iCE40 DSP inference.\n", log_id(pm.module), log_id(st.mul));
 
+	log_debug("ffA:    %s %s %s\n", log_id(st.ffA, "--"), log_id(st.ffAholdmux, "--"), log_id(st.ffArstmux, "--"));
+	log_debug("ffB:    %s %s %s\n", log_id(st.ffB, "--"), log_id(st.ffBholdmux, "--"), log_id(st.ffBrstmux, "--"));
+	log_debug("ffCD:   %s %s\n", log_id(st.ffCD, "--"), log_id(st.ffCDholdmux, "--"));
+	log_debug("mul:    %s\n", log_id(st.mul, "--"));
+	log_debug("ffFJKG: %s\n", log_id(st.ffFJKG, "--"));
+	log_debug("ffH:    %s\n", log_id(st.ffH, "--"));
+	log_debug("add:    %s\n", log_id(st.add, "--"));
+	log_debug("mux:    %s\n", log_id(st.mux, "--"));
+	log_debug("ffO:    %s %s %s\n", log_id(st.ffO, "--"), log_id(st.ffOholdmux, "--"), log_id(st.ffOrstmux, "--"));
+	log_debug("\n");
+
 	if (GetSize(st.sigA) > 16) {
 		log("  input A (%s) is too large (%d > 16).\n", log_signal(st.sigA), GetSize(st.sigA));
 		return;
@@ -52,59 +52,85 @@ void create_ice40_dsp(ice40_dsp_pm &pm)
 		return;
 	}
 
-	if (GetSize(st.sigS) > 32) {
-		log("  accumulator (%s) is too large (%d > 32).\n", log_signal(st.sigS), GetSize(st.sigS));
+	if (GetSize(st.sigO) > 33) {
+		log("  adder/accumulator (%s) is too large (%d > 33).\n", log_signal(st.sigO), GetSize(st.sigO));
 		return;
 	}
 
-	if (GetSize(st.sigY) > 32) {
-		log("  output (%s) is too large (%d > 32).\n", log_signal(st.sigY), GetSize(st.sigY));
+	if (GetSize(st.sigH) > 32) {
+		log("  output (%s) is too large (%d > 32).\n", log_signal(st.sigH), GetSize(st.sigH));
 		return;
 	}
 
-	bool mul_signed = st.mul->getParam("\\A_SIGNED").as_bool();
+	Cell *cell = st.mul;
+	if (cell->type == ID($mul)) {
+		log("  replacing %s with SB_MAC16 cell.\n", log_id(st.mul->type));
 
-	log("  replacing $mul with SB_MAC16 cell.\n");
-
-	Cell *cell = pm.module->addCell(NEW_ID, "\\SB_MAC16");
-	pm.module->swap_names(cell, st.mul);
+		cell = pm.module->addCell(NEW_ID, ID(SB_MAC16));
+		pm.module->swap_names(cell, st.mul);
+	}
+	else log_assert(cell->type == ID(SB_MAC16));
 
 	// SB_MAC16 Input Interface
-
 	SigSpec A = st.sigA;
-	A.extend_u0(16, mul_signed);
+	A.extend_u0(16, st.mul->getParam(ID(A_SIGNED)).as_bool());
+	log_assert(GetSize(A) == 16);
 
 	SigSpec B = st.sigB;
-	B.extend_u0(16, mul_signed);
-
-	SigSpec CD;
-	if (st.muxA)
-		CD = st.muxA->getPort("\\B");
-	if (st.muxB)
-		CD = st.muxB->getPort("\\A");
-	CD.extend_u0(32, mul_signed);
+	B.extend_u0(16, st.mul->getParam(ID(B_SIGNED)).as_bool());
+	log_assert(GetSize(B) == 16);
 
-	cell->setPort("\\A", A);
-	cell->setPort("\\B", B);
-	cell->setPort("\\C", CD.extract(0, 16));
-	cell->setPort("\\D", CD.extract(16, 16));
+	SigSpec CD = st.sigCD;
+	if (CD.empty())
+		CD = RTLIL::Const(0, 32);
+	else
+		log_assert(GetSize(CD) == 32);
 
-	cell->setParam("\\A_REG", st.ffA ? State::S1 : State::S0);
-	cell->setParam("\\B_REG", st.ffB ? State::S1 : State::S0);
+	cell->setPort(ID::A, A);
+	cell->setPort(ID::B, B);
+	cell->setPort(ID(C), CD.extract(16, 16));
+	cell->setPort(ID(D), CD.extract(0, 16));
 
-	cell->setPort("\\AHOLD", State::S0);
-	cell->setPort("\\BHOLD", State::S0);
-	cell->setPort("\\CHOLD", State::S0);
-	cell->setPort("\\DHOLD", State::S0);
+	cell->setParam(ID(A_REG), st.ffA ? State::S1 : State::S0);
+	cell->setParam(ID(B_REG), st.ffB ? State::S1 : State::S0);
+	cell->setParam(ID(C_REG), st.ffCD ? State::S1 : State::S0);
+	cell->setParam(ID(D_REG), st.ffCD ? State::S1 : State::S0);
 
-	cell->setPort("\\IRSTTOP", State::S0);
-	cell->setPort("\\IRSTBOT", State::S0);
+	SigSpec AHOLD, BHOLD, CDHOLD;
+	if (st.ffAholdmux)
+		AHOLD = st.ffAholdpol ? st.ffAholdmux->getPort(ID(S)) : pm.module->Not(NEW_ID, st.ffAholdmux->getPort(ID(S)));
+	else
+		AHOLD = State::S0;
+	if (st.ffBholdmux)
+		BHOLD = st.ffBholdpol ? st.ffBholdmux->getPort(ID(S)) : pm.module->Not(NEW_ID, st.ffBholdmux->getPort(ID(S)));
+	else
+		BHOLD = State::S0;
+	if (st.ffCDholdmux)
+		CDHOLD = st.ffCDholdpol ? st.ffCDholdmux->getPort(ID(S)) : pm.module->Not(NEW_ID, st.ffCDholdmux->getPort(ID(S)));
+	else
+		CDHOLD = State::S0;
+	cell->setPort(ID(AHOLD), AHOLD);
+	cell->setPort(ID(BHOLD), BHOLD);
+	cell->setPort(ID(CHOLD), CDHOLD);
+	cell->setPort(ID(DHOLD), CDHOLD);
+
+	SigSpec IRSTTOP, IRSTBOT;
+	if (st.ffArstmux)
+		IRSTTOP = st.ffArstpol ? st.ffArstmux->getPort(ID(S)) : pm.module->Not(NEW_ID, st.ffArstmux->getPort(ID(S)));
+	else
+		IRSTTOP = State::S0;
+	if (st.ffBrstmux)
+		IRSTBOT = st.ffBrstpol ? st.ffBrstmux->getPort(ID(S)) : pm.module->Not(NEW_ID, st.ffBrstmux->getPort(ID(S)));
+	else
+		IRSTBOT = State::S0;
+	cell->setPort(ID(IRSTTOP), IRSTTOP);
+	cell->setPort(ID(IRSTBOT), IRSTBOT);
 
-	if (st.clock_vld)
+	if (st.clock != SigBit())
 	{
-		cell->setPort("\\CLK", st.clock);
-		cell->setPort("\\CE", State::S1);
-		cell->setParam("\\NEG_TRIGGER", st.clock_pol ? State::S0 : State::S1);
+		cell->setPort(ID(CLK), st.clock);
+		cell->setPort(ID(CE), State::S1);
+		cell->setParam(ID(NEG_TRIGGER), st.clock_pol ? State::S0 : State::S1);
 
 		log("  clock: %s (%s)", log_signal(st.clock), st.clock_pol ? "posedge" : "negedge");
 
@@ -114,91 +140,137 @@ void create_ice40_dsp(ice40_dsp_pm &pm)
 		if (st.ffB)
 			log(" ffB:%s", log_id(st.ffB));
 
-		if (st.ffY)
-			log(" ffY:%s", log_id(st.ffY));
+		if (st.ffCD)
+			log(" ffCD:%s", log_id(st.ffCD));
+
+		if (st.ffFJKG)
+			log(" ffFJKG:%s", log_id(st.ffFJKG));
+
+		if (st.ffH)
+			log(" ffH:%s", log_id(st.ffH));
 
-		if (st.ffS)
-			log(" ffS:%s", log_id(st.ffS));
+		if (st.ffO)
+			log(" ffO:%s", log_id(st.ffO));
 
 		log("\n");
 	}
 	else
 	{
-		cell->setPort("\\CLK", State::S0);
-		cell->setPort("\\CE", State::S0);
-		cell->setParam("\\NEG_TRIGGER", State::S0);
+		cell->setPort(ID(CLK), State::S0);
+		cell->setPort(ID(CE), State::S0);
+		cell->setParam(ID(NEG_TRIGGER), State::S0);
 	}
 
 	// SB_MAC16 Cascade Interface
 
-	cell->setPort("\\SIGNEXTIN", State::Sx);
-	cell->setPort("\\SIGNEXTOUT", pm.module->addWire(NEW_ID));
+	cell->setPort(ID(SIGNEXTIN), State::Sx);
+	cell->setPort(ID(SIGNEXTOUT), pm.module->addWire(NEW_ID));
 
-	cell->setPort("\\CI", State::Sx);
-	cell->setPort("\\CO", pm.module->addWire(NEW_ID));
+	cell->setPort(ID(CI), State::Sx);
 
-	cell->setPort("\\ACCUMCI", State::Sx);
-	cell->setPort("\\ACCUMCO", pm.module->addWire(NEW_ID));
+	cell->setPort(ID(ACCUMCI), State::Sx);
+	cell->setPort(ID(ACCUMCO), pm.module->addWire(NEW_ID));
 
 	// SB_MAC16 Output Interface
 
-	SigSpec O = st.ffS ? st.sigS : st.sigY;
+	SigSpec O = st.sigO;
+	int O_width = GetSize(O);
+	if (O_width == 33) {
+		log_assert(st.add);
+		// If we have a signed multiply-add, then perform sign extension
+		if (st.add->getParam(ID(A_SIGNED)).as_bool() && st.add->getParam(ID(B_SIGNED)).as_bool())
+			pm.module->connect(O[32], O[31]);
+		else
+			cell->setPort(ID(CO), O[32]);
+		O.remove(O_width-1);
+	}
+	else
+		cell->setPort(ID(CO), pm.module->addWire(NEW_ID));
+	log_assert(GetSize(O) <= 32);
 	if (GetSize(O) < 32)
 		O.append(pm.module->addWire(NEW_ID, 32-GetSize(O)));
 
-	cell->setPort("\\O", O);
-
-	if (st.addAB) {
-		log("  accumulator %s (%s)\n", log_id(st.addAB), log_id(st.addAB->type));
-		cell->setPort("\\ADDSUBTOP", st.addAB->type == "$add" ? State::S0 : State::S1);
-		cell->setPort("\\ADDSUBBOT", st.addAB->type == "$add" ? State::S0 : State::S1);
+	cell->setPort(ID(O), O);
+
+	bool accum = false;
+	if (st.add) {
+		accum = (st.ffO && st.add->getPort(st.addAB == ID::A ? ID::B : ID::A) == st.sigO);
+		if (accum)
+			log("  accumulator %s (%s)\n", log_id(st.add), log_id(st.add->type));
+		else
+			log("  adder %s (%s)\n", log_id(st.add), log_id(st.add->type));
+		cell->setPort(ID(ADDSUBTOP), st.add->type == ID($add) ? State::S0 : State::S1);
+		cell->setPort(ID(ADDSUBBOT), st.add->type == ID($add) ? State::S0 : State::S1);
 	} else {
-		cell->setPort("\\ADDSUBTOP", State::S0);
-		cell->setPort("\\ADDSUBBOT", State::S0);
+		cell->setPort(ID(ADDSUBTOP), State::S0);
+		cell->setPort(ID(ADDSUBBOT), State::S0);
 	}
 
-	cell->setPort("\\ORSTTOP", State::S0);
-	cell->setPort("\\ORSTBOT", State::S0);
+	SigSpec OHOLD;
+	if (st.ffOholdmux)
+		OHOLD = st.ffOholdpol ? st.ffOholdmux->getPort(ID(S)) : pm.module->Not(NEW_ID, st.ffOholdmux->getPort(ID(S)));
+	else
+		OHOLD = State::S0;
+	cell->setPort(ID(OHOLDTOP), OHOLD);
+	cell->setPort(ID(OHOLDBOT), OHOLD);
 
-	cell->setPort("\\OHOLDTOP", State::S0);
-	cell->setPort("\\OHOLDBOT", State::S0);
+	SigSpec ORST;
+	if (st.ffOrstmux)
+		ORST = st.ffOrstpol ? st.ffOrstmux->getPort(ID(S)) : pm.module->Not(NEW_ID, st.ffOrstmux->getPort(ID(S)));
+	else
+		ORST = State::S0;
+	cell->setPort(ID(ORSTTOP), ORST);
+	cell->setPort(ID(ORSTBOT), ORST);
 
 	SigSpec acc_reset = State::S0;
-	if (st.muxA)
-		acc_reset = st.muxA->getPort("\\S");
-	if (st.muxB)
-		acc_reset = pm.module->Not(NEW_ID, st.muxB->getPort("\\S"));
-
-	cell->setPort("\\OLOADTOP", acc_reset);
-	cell->setPort("\\OLOADBOT", acc_reset);
+	if (st.mux) {
+		if (st.muxAB == ID::A)
+			acc_reset = st.mux->getPort(ID(S));
+		else
+			acc_reset = pm.module->Not(NEW_ID, st.mux->getPort(ID(S)));
+	}
+	cell->setPort(ID(OLOADTOP), acc_reset);
+	cell->setPort(ID(OLOADBOT), acc_reset);
 
 	// SB_MAC16 Remaining Parameters
 
-	cell->setParam("\\C_REG", State::S0);
-	cell->setParam("\\D_REG", State::S0);
+	cell->setParam(ID(TOP_8x8_MULT_REG), st.ffFJKG ? State::S1 : State::S0);
+	cell->setParam(ID(BOT_8x8_MULT_REG), st.ffFJKG ? State::S1 : State::S0);
+	cell->setParam(ID(PIPELINE_16x16_MULT_REG1), st.ffFJKG ? State::S1 : State::S0);
+	cell->setParam(ID(PIPELINE_16x16_MULT_REG2), st.ffH ? State::S1 : State::S0);
 
-	cell->setParam("\\TOP_8x8_MULT_REG", st.ffY ? State::S1 : State::S0);
-	cell->setParam("\\BOT_8x8_MULT_REG", st.ffY ? State::S1 : State::S0);
-	cell->setParam("\\PIPELINE_16x16_MULT_REG1", st.ffY ? State::S1 : State::S0);
-	cell->setParam("\\PIPELINE_16x16_MULT_REG2", State::S0);
+	cell->setParam(ID(TOPADDSUB_LOWERINPUT), Const(2, 2));
+	cell->setParam(ID(TOPADDSUB_UPPERINPUT), accum ? State::S0 : State::S1);
+	cell->setParam(ID(TOPADDSUB_CARRYSELECT), Const(3, 2));
 
-	cell->setParam("\\TOPOUTPUT_SELECT", Const(st.ffS ? 1 : 3, 2));
-	cell->setParam("\\TOPADDSUB_LOWERINPUT", Const(2, 2));
-	cell->setParam("\\TOPADDSUB_UPPERINPUT", State::S0);
-	cell->setParam("\\TOPADDSUB_CARRYSELECT", Const(3, 2));
+	cell->setParam(ID(BOTADDSUB_LOWERINPUT), Const(2, 2));
+	cell->setParam(ID(BOTADDSUB_UPPERINPUT), accum ? State::S0 : State::S1);
+	cell->setParam(ID(BOTADDSUB_CARRYSELECT), Const(0, 2));
 
-	cell->setParam("\\BOTOUTPUT_SELECT", Const(st.ffS ? 1 : 3, 2));
-	cell->setParam("\\BOTADDSUB_LOWERINPUT", Const(2, 2));
-	cell->setParam("\\BOTADDSUB_UPPERINPUT", State::S0);
-	cell->setParam("\\BOTADDSUB_CARRYSELECT", Const(0, 2));
+	cell->setParam(ID(MODE_8x8), State::S0);
+	cell->setParam(ID(A_SIGNED), st.mul->getParam(ID(A_SIGNED)).as_bool());
+	cell->setParam(ID(B_SIGNED), st.mul->getParam(ID(B_SIGNED)).as_bool());
 
-	cell->setParam("\\MODE_8x8", State::S0);
-	cell->setParam("\\A_SIGNED", mul_signed ? State::S1 : State::S0);
-	cell->setParam("\\B_SIGNED", mul_signed ? State::S1 : State::S0);
+	if (st.ffO) {
+		if (st.o_lo)
+			cell->setParam(ID(TOPOUTPUT_SELECT), Const(st.add ? 0 : 3, 2));
+		else
+			cell->setParam(ID(TOPOUTPUT_SELECT), Const(1, 2));
 
-	pm.autoremove(st.mul);
-	pm.autoremove(st.ffY);
-	pm.autoremove(st.ffS);
+		st.ffO->connections_.at(ID(Q)).replace(O, pm.module->addWire(NEW_ID, GetSize(O)));
+		cell->setParam(ID(BOTOUTPUT_SELECT), Const(1, 2));
+	}
+	else {
+		cell->setParam(ID(TOPOUTPUT_SELECT), Const(st.add ? 0 : 3, 2));
+		cell->setParam(ID(BOTOUTPUT_SELECT), Const(st.add ? 0 : 3, 2));
+	}
+
+	if (cell != st.mul)
+		pm.autoremove(st.mul);
+	else
+		pm.blacklist(st.mul);
+	pm.autoremove(st.ffFJKG);
+	pm.autoremove(st.add);
 }
 
 struct Ice40DspPass : public Pass {
@@ -209,7 +281,17 @@ struct Ice40DspPass : public Pass {
 		log("\n");
 		log("    ice40_dsp [options] [selection]\n");
 		log("\n");
-		log("Map multipliers and multiply-accumulate blocks to iCE40 DSP resources.\n");
+		log("Map multipliers ($mul/SB_MAC16) and multiply-accumulate ($mul/SB_MAC16 + $add)\n");
+		log("cells into iCE40 DSP resources.\n");
+		log("Currently, only the 16x16 multiply mode is supported and not the 2 x 8x8 mode.\n");
+		log("\n");
+		log("Pack input registers (A, B, {C,D}; with optional hold), pipeline registers\n");
+		log("({F,J,K,G}, H), output registers (O -- full 32-bits or lower 16-bits only; with\n");
+		log("optional hold), and post-adder into into the SB_MAC16 resource.\n");
+		log("\n");
+		log("Multiply-accumulate operations using the post-adder with feedback on the {C,D}\n");
+		log("input will be folded into the DSP. In this scenario only, resetting the\n");
+		log("the accumulator to an arbitrary value can be inferred to use the {C,D} input.\n");
 		log("\n");
 	}
 	void execute(std::vector<std::string> args, RTLIL::Design *design) YS_OVERRIDE
diff --git a/passes/pmgen/ice40_dsp.pmg b/passes/pmgen/ice40_dsp.pmg
index 7003092bb..6b6d2b56f 100644
--- a/passes/pmgen/ice40_dsp.pmg
+++ b/passes/pmgen/ice40_dsp.pmg
@@ -1,163 +1,574 @@
 pattern ice40_dsp
 
 state <SigBit> clock
-state <bool> clock_pol clock_vld
-state <SigSpec> sigA sigB sigY sigS
-state <Cell*> addAB muxAB
+state <bool> clock_pol cd_signed o_lo
+state <SigSpec> sigA sigB sigCD sigH sigO
+state <Cell*> add mux
+state <IdString> addAB muxAB
+
+state <bool> ffAholdpol ffBholdpol ffCDholdpol ffOholdpol
+state <bool> ffArstpol ffBrstpol ffCDrstpol ffOrstpol
+
+state <Cell*> ffA ffAholdmux ffArstmux ffB ffBholdmux ffBrstmux ffCD ffCDholdmux
+state <Cell*> ffFJKG ffH ffO ffOholdmux ffOrstmux
+
+// subpattern
+state <SigSpec> argQ argD
+state <bool> ffholdpol ffrstpol
+state <int> ffoffset
+udata <SigSpec> dffD dffQ
+udata <SigBit> dffclock
+udata <Cell*> dff dffholdmux dffrstmux
+udata <bool> dffholdpol dffrstpol dffclock_pol
 
 match mul
-	select mul->type.in($mul)
+	select mul->type.in($mul, \SB_MAC16)
 	select GetSize(mul->getPort(\A)) + GetSize(mul->getPort(\B)) > 10
-	select GetSize(mul->getPort(\Y)) > 10
 endmatch
 
-match ffA
-	select ffA->type.in($dff)
-	// select nusers(port(ffA, \Q)) == 2
-	index <SigSpec> port(ffA, \Q) === port(mul, \A)
-	optional
-endmatch
+code sigA sigB sigH
+	auto unextend = [](const SigSpec &sig) {
+		int i;
+		for (i = GetSize(sig)-1; i > 0; i--)
+			if (sig[i] != sig[i-1])
+				break;
+		// Do not remove non-const sign bit
+		if (sig[i].wire)
+			++i;
+		return sig.extract(0, i);
+	};
+	sigA = unextend(port(mul, \A));
+	sigB = unextend(port(mul, \B));
 
-code sigA clock clock_pol clock_vld
-	sigA = port(mul, \A);
+	SigSpec O;
+	if (mul->type == $mul)
+		O = mul->getPort(\Y);
+	else if (mul->type == \SB_MAC16)
+		O = mul->getPort(\O);
+	else log_abort();
+	if (GetSize(O) <= 10)
+		reject;
 
-	if (ffA) {
-		sigA = port(ffA, \D);
+	// Only care about those bits that are used
+	int i;
+	for (i = 0; i < GetSize(O); i++) {
+		if (nusers(O[i]) <= 1)
+			break;
+		sigH.append(O[i]);
+	}
+	log_assert(nusers(O.extract_end(i)) <= 1);
+endcode
 
-		clock = port(ffA, \CLK).as_bit();
-		clock_pol = param(ffA, \CLK_POLARITY).as_bool();
-		clock_vld = true;
+code argQ ffA ffAholdmux ffArstmux ffAholdpol ffArstpol sigA clock clock_pol
+	if (mul->type != \SB_MAC16 || !param(mul, \A_REG).as_bool()) {
+		argQ = sigA;
+		subpattern(in_dffe);
+		if (dff) {
+			ffA = dff;
+			clock = dffclock;
+			clock_pol = dffclock_pol;
+			if (dffrstmux) {
+				ffArstmux = dffrstmux;
+				ffArstpol = dffrstpol;
+			}
+			if (dffholdmux) {
+				ffAholdmux = dffholdmux;
+				ffAholdpol = dffholdpol;
+			}
+			sigA = dffD;
+		}
 	}
 endcode
 
-match ffB
-	select ffB->type.in($dff)
-	// select nusers(port(ffB, \Q)) == 2
-	index <SigSpec> port(ffB, \Q) === port(mul, \B)
-	optional
-endmatch
+code argQ ffB ffBholdmux ffBrstmux ffBholdpol ffBrstpol sigB clock clock_pol
+	if (mul->type != \SB_MAC16 || !param(mul, \B_REG).as_bool()) {
+		argQ = sigB;
+		subpattern(in_dffe);
+		if (dff) {
+			ffB = dff;
+			clock = dffclock;
+			clock_pol = dffclock_pol;
+			if (dffrstmux) {
+				ffBrstmux = dffrstmux;
+				ffBrstpol = dffrstpol;
+			}
+			if (dffholdmux) {
+				ffBholdmux = dffholdmux;
+				ffBholdpol = dffholdpol;
+			}
+			sigB = dffD;
+		}
+	}
+endcode
 
-code sigB clock clock_pol clock_vld
-	sigB = port(mul, \B);
+code argD ffFJKG sigH clock clock_pol
+	if (nusers(sigH) == 2 &&
+			(mul->type != \SB_MAC16 ||
+			 (!param(mul, \TOP_8x8_MULT_REG).as_bool() && !param(mul, \BOT_8x8_MULT_REG).as_bool() && !param(mul, \PIPELINE_16x16_MULT_REG1).as_bool() && !param(mul, \PIPELINE_16x16_MULT_REG1).as_bool()))) {
+		argD = sigH;
+		subpattern(out_dffe);
+		if (dff) {
+			// F/J/K/G do not have a CE-like (hold) input
+			if (dffholdmux)
+				goto reject_ffFJKG;
 
-	if (ffB) {
-		sigB = port(ffB, \D);
-		SigBit c = port(ffB, \CLK).as_bit();
-		bool cp = param(ffB, \CLK_POLARITY).as_bool();
+			// Reset signal of F/J (IRSTTOP) and K/G (IRSTBOT)
+			//   shared with A and B
+			if ((ffArstmux != NULL) != (dffrstmux != NULL))
+				goto reject_ffFJKG;
+			if ((ffBrstmux != NULL) != (dffrstmux != NULL))
+				goto reject_ffFJKG;
+			if (ffArstmux) {
+				if (port(ffArstmux, \S) != port(dffrstmux, \S))
+					goto reject_ffFJKG;
+				if (ffArstpol != dffrstpol)
+					goto reject_ffFJKG;
+			}
+			if (ffBrstmux) {
+				if (port(ffBrstmux, \S) != port(dffrstmux, \S))
+					goto reject_ffFJKG;
+				if (ffBrstpol != dffrstpol)
+					goto reject_ffFJKG;
+			}
 
-		if (clock_vld && (c != clock || cp != clock_pol))
-			reject;
+			ffFJKG = dff;
+			clock = dffclock;
+			clock_pol = dffclock_pol;
+			sigH = dffQ;
+
+reject_ffFJKG: 		;
+		}
+	}
+endcode
+
+code argD ffH sigH sigO clock clock_pol
+	if (ffFJKG && nusers(sigH) == 2 &&
+			(mul->type != \SB_MAC16 || !param(mul, \PIPELINE_16x16_MULT_REG2).as_bool())) {
+		argD = sigH;
+		subpattern(out_dffe);
+		if (dff) {
+			// H does not have a CE-like (hold) input
+			if (dffholdmux)
+				goto reject_ffH;
+
+			// Reset signal of H (IRSTBOT) shared with B
+			if ((ffBrstmux != NULL) != (dffrstmux != NULL))
+				goto reject_ffH;
+			if (ffBrstmux) {
+				if (port(ffBrstmux, \S) != port(dffrstmux, \S))
+					goto reject_ffH;
+				if (ffBrstpol != dffrstpol)
+					goto reject_ffH;
+			}
 
-		clock = c;
-		clock_pol = cp;
-		clock_vld = true;
+			ffH = dff;
+			clock = dffclock;
+			clock_pol = dffclock_pol;
+			sigH = dffQ;
+
+reject_ffH:		;
+		}
 	}
+
+	sigO = sigH;
 endcode
 
-match ffY
-	select ffY->type.in($dff)
-	select nusers(port(ffY, \D)) == 2
-	index <SigSpec> port(ffY, \D) === port(mul, \Y)
+match add
+	if mul->type != \SB_MAC16 || (param(mul, \TOPOUTPUT_SELECT).as_int() == 3 && param(mul, \BOTOUTPUT_SELECT).as_int() == 3)
+
+	select add->type.in($add)
+	choice <IdString> AB {\A, \B}
+	select nusers(port(add, AB)) == 2
+
+	index <SigBit> port(add, AB)[0] === sigH[0]
+	filter GetSize(port(add, AB)) <= GetSize(sigH)
+	filter port(add, AB) == sigH.extract(0, GetSize(port(add, AB)))
+	filter nusers(sigH.extract_end(GetSize(port(add, AB)))) <= 1
+	set addAB AB
 	optional
 endmatch
 
-code sigY clock clock_pol clock_vld
-	sigY = port(mul, \Y);
+code sigCD sigO cd_signed
+	if (add) {
+		sigCD = port(add, addAB == \A ? \B : \A);
+		cd_signed = param(add, addAB == \A ? \B_SIGNED : \A_SIGNED).as_bool();
 
-	if (ffY) {
-		sigY = port(ffY, \Q);
-		SigBit c = port(ffY, \CLK).as_bit();
-		bool cp = param(ffY, \CLK_POLARITY).as_bool();
+		int natural_mul_width = GetSize(sigA) + GetSize(sigB);
+		int actual_mul_width = GetSize(sigH);
+		int actual_acc_width = GetSize(sigCD);
 
-		if (clock_vld && (c != clock || cp != clock_pol))
+		if ((actual_acc_width > actual_mul_width) && (natural_mul_width > actual_mul_width))
+			reject;
+		// If accumulator, check adder width and signedness
+		if (sigCD == sigH && (actual_acc_width != actual_mul_width) && (param(mul, \A_SIGNED).as_bool() != param(add, \A_SIGNED).as_bool()))
 			reject;
 
-		clock = c;
-		clock_pol = cp;
-		clock_vld = true;
+		sigO = port(add, \Y);
 	}
 endcode
 
-match addA
-	select addA->type.in($add)
-	select nusers(port(addA, \A)) == 2
-	index <SigSpec> port(addA, \A) === sigY
+match mux
+	select mux->type == $mux
+	choice <IdString> AB {\A, \B}
+	select nusers(port(mux, AB)) == 2
+	index <SigSpec> port(mux, AB) === sigO
+	set muxAB AB
 	optional
 endmatch
 
-match addB
-	if !addA
-	select addB->type.in($add, $sub)
-	select nusers(port(addB, \B)) == 2
-	index <SigSpec> port(addB, \B) === sigY
-	optional
-endmatch
+code sigO
+	if (mux)
+		sigO = port(mux, \Y);
+endcode
+
+code argD ffO ffOholdmux ffOrstmux ffOholdpol ffOrstpol sigO sigCD clock clock_pol cd_signed o_lo
+	if (mul->type != \SB_MAC16 ||
+			// Ensure that register is not already used
+			((param(mul, \TOPOUTPUT_SELECT, 0).as_int() != 1 && param(mul, \BOTOUTPUT_SELECT, 0).as_int() != 1) &&
+			 // Ensure that OLOADTOP/OLOADBOT is unused or zero
+			 (port(mul, \OLOADTOP, State::S0).is_fully_zero() && port(mul, \OLOADBOT, State::S0).is_fully_zero()))) {
+
+		dff = nullptr;
+
+		// First try entire sigO
+		if (nusers(sigO) == 2) {
+			argD = sigO;
+			subpattern(out_dffe);
+		}
+
+		// Otherwise try just its least significant 16 bits
+		if (!dff && GetSize(sigO) > 16) {
+			argD = sigO.extract(0, 16);
+			if (nusers(argD) == 2) {
+				subpattern(out_dffe);
+				o_lo = dff;
+			}
+		}
+
+		if (dff) {
+			ffO = dff;
+			clock = dffclock;
+			clock_pol = dffclock_pol;
+			if (dffrstmux) {
+				ffOrstmux = dffrstmux;
+				ffOrstpol = dffrstpol;
+			}
+			if (dffholdmux) {
+				ffOholdmux = dffholdmux;
+				ffOholdpol = dffholdpol;
+			}
+
+			sigO.replace(sigO.extract(0, GetSize(dffQ)), dffQ);
+		}
 
-code addAB sigS
-	if (addA) {
-		addAB = addA;
-		sigS = port(addA, \B);
+		// Loading value into output register is not
+		//   supported unless using accumulator
+		if (mux) {
+			if (sigCD != sigO)
+				reject;
+			sigCD = port(mux, muxAB == \B ? \A : \B);
+
+			cd_signed = add && param(add, \A_SIGNED).as_bool() && param(add, \B_SIGNED).as_bool();
+		}
 	}
-	if (addB) {
-		addAB = addB;
-		sigS = port(addB, \A);
+endcode
+
+code argQ ffCD ffCDholdmux ffCDholdpol ffCDrstpol sigCD clock clock_pol
+	if (!sigCD.empty() && sigCD != sigO &&
+			(mul->type != \SB_MAC16 || (!param(mul, \C_REG).as_bool() && !param(mul, \D_REG).as_bool()))) {
+		argQ = sigCD;
+		subpattern(in_dffe);
+		if (dff) {
+			if (dffholdmux) {
+				ffCDholdmux = dffholdmux;
+				ffCDholdpol = dffholdpol;
+			}
+
+			// Reset signal of C (IRSTTOP) and D (IRSTBOT)
+			//   shared with A and B
+			if ((ffArstmux != NULL) != (dffrstmux != NULL))
+				goto reject_ffCD;
+			if ((ffBrstmux != NULL) != (dffrstmux != NULL))
+				goto reject_ffCD;
+			if (ffArstmux) {
+				if (port(ffArstmux, \S) != port(dffrstmux, \S))
+					goto reject_ffCD;
+				if (ffArstpol != dffrstpol)
+					goto reject_ffCD;
+			}
+			if (ffBrstmux) {
+				if (port(ffBrstmux, \S) != port(dffrstmux, \S))
+					goto reject_ffCD;
+				if (ffBrstpol != dffrstpol)
+					goto reject_ffCD;
+			}
+
+			ffCD = dff;
+			clock = dffclock;
+			clock_pol = dffclock_pol;
+			sigCD = dffD;
+
+reject_ffCD: 		;
+		}
 	}
-	if (addAB) {
-		int natural_mul_width = GetSize(sigA) + GetSize(sigB);
-		int actual_mul_width = GetSize(sigY);
-		int actual_acc_width = GetSize(sigS);
+endcode
 
-		if ((actual_acc_width > actual_mul_width) && (natural_mul_width > actual_mul_width))
+code sigCD
+	sigCD.extend_u0(32, cd_signed);
+endcode
+
+code
+	accept;
+endcode
+
+// #######################
+
+subpattern in_dffe
+arg argD argQ clock clock_pol
+
+code
+	dff = nullptr;
+	for (auto c : argQ.chunks()) {
+		if (!c.wire)
+			reject;
+		if (c.wire->get_bool_attribute(\keep))
 			reject;
-		if ((actual_acc_width != actual_mul_width) && (param(mul, \A_SIGNED).as_bool() != param(addAB, \A_SIGNED).as_bool()))
+		Const init = c.wire->attributes.at(\init, State::Sx);
+		if (!init.is_fully_undef() && !init.is_fully_zero())
 			reject;
 	}
 endcode
 
-match muxA
-	if addAB
-	select muxA->type.in($mux)
-	select nusers(port(muxA, \A)) == 2
-	index <SigSpec> port(muxA, \A) === port(addAB, \Y)
-	optional
+match ff
+	select ff->type.in($dff)
+	// DSP48E1 does not support clock inversion
+	select param(ff, \CLK_POLARITY).as_bool()
+
+	slice offset GetSize(port(ff, \D))
+	index <SigBit> port(ff, \Q)[offset] === argQ[0]
+
+	// Check that the rest of argQ is present
+	filter GetSize(port(ff, \Q)) >= offset + GetSize(argQ)
+	filter port(ff, \Q).extract(offset, GetSize(argQ)) == argQ
+
+	set ffoffset offset
 endmatch
 
-match muxB
-	if addAB
-	if !muxA
-	select muxB->type.in($mux)
-	select nusers(port(muxB, \B)) == 2
-	index <SigSpec> port(muxB, \B) === port(addAB, \Y)
-	optional
+code argQ argD
+{
+	if (clock != SigBit()) {
+		if (port(ff, \CLK) != clock)
+			reject;
+		if (param(ff, \CLK_POLARITY).as_bool() != clock_pol)
+			reject;
+	}
+
+	SigSpec Q = port(ff, \Q);
+	dff = ff;
+	dffclock = port(ff, \CLK);
+	dffclock_pol = param(ff, \CLK_POLARITY).as_bool();
+	dffD = argQ;
+	argD = port(ff, \D);
+	argQ = Q;
+	dffD.replace(argQ, argD);
+	// Only search for ffrstmux if dffD only
+	//   has two (ff, ffrstmux) users
+	if (nusers(dffD) > 2)
+		argD = SigSpec();
+}
+endcode
+
+match ffrstmux
+	if false /* TODO: ice40 resets are actually async */
+
+	if !argD.empty()
+	select ffrstmux->type.in($mux)
+	index <SigSpec> port(ffrstmux, \Y) === argD
+
+	choice <IdString> BA {\B, \A}
+	// DSP48E1 only supports reset to zero
+	select port(ffrstmux, BA).is_fully_zero()
+
+	define <bool> pol (BA == \B)
+	set ffrstpol pol
+	semioptional
 endmatch
 
-code muxAB
-	muxAB = addAB;
-	if (muxA)
-		muxAB = muxA;
-	if (muxB)
-		muxAB = muxB;
+code argD
+	if (ffrstmux) {
+		dffrstmux = ffrstmux;
+		dffrstpol = ffrstpol;
+		argD = port(ffrstmux, ffrstpol ? \A : \B);
+		dffD.replace(port(ffrstmux, \Y), argD);
+
+		// Only search for ffholdmux if argQ has at
+		//   least 3 users (ff, <upstream>, ffrstmux) and
+		//   dffD only has two (ff, ffrstmux)
+		if (!(nusers(argQ) >= 3 && nusers(dffD) == 2))
+			argD = SigSpec();
+	}
+	else
+		dffrstmux = nullptr;
 endcode
 
-match ffS
-	if muxAB
-	select ffS->type.in($dff)
-	select nusers(port(ffS, \D)) == 2
-	index <SigSpec> port(ffS, \D) === port(muxAB, \Y)
-	index <SigSpec> port(ffS, \Q) === sigS
+match ffholdmux
+	if !argD.empty()
+	select ffholdmux->type.in($mux)
+	index <SigSpec> port(ffholdmux, \Y) === argD
+	choice <IdString> BA {\B, \A}
+	index <SigSpec> port(ffholdmux, BA) === argQ
+	define <bool> pol (BA == \B)
+	set ffholdpol pol
+	semioptional
 endmatch
 
-code clock clock_pol clock_vld
-	if (ffS) {
-		SigBit c = port(ffS, \CLK).as_bit();
-		bool cp = param(ffS, \CLK_POLARITY).as_bool();
+code argD
+	if (ffholdmux) {
+		dffholdmux = ffholdmux;
+		dffholdpol = ffholdpol;
+		argD = port(ffholdmux, ffholdpol ? \A : \B);
+		dffD.replace(port(ffholdmux, \Y), argD);
+	}
+	else
+		dffholdmux = nullptr;
+endcode
 
-		if (clock_vld && (c != clock || cp != clock_pol))
+// #######################
+
+subpattern out_dffe
+arg argD argQ clock clock_pol
+
+code
+	dff = nullptr;
+	for (auto c : argD.chunks())
+		if (c.wire->get_bool_attribute(\keep))
 			reject;
+endcode
 
-		clock = c;
-		clock_pol = cp;
-		clock_vld = true;
+match ffholdmux
+	select ffholdmux->type.in($mux)
+	// ffholdmux output must have two users: ffholdmux and ff.D
+	select nusers(port(ffholdmux, \Y)) == 2
+
+	choice <IdString> BA {\B, \A}
+	// keep-last-value net must have at least three users: ffholdmux, ff, downstream sink(s)
+	select nusers(port(ffholdmux, BA)) >= 3
+
+	slice offset GetSize(port(ffholdmux, \Y))
+	define <IdString> AB (BA == \B ? \A : \B)
+	index <SigBit> port(ffholdmux, AB)[offset] === argD[0]
+
+	// Check that the rest of argD is present
+	filter GetSize(port(ffholdmux, AB)) >= offset + GetSize(argD)
+	filter port(ffholdmux, AB).extract(offset, GetSize(argD)) == argD
+
+	set ffoffset offset
+	define <bool> pol (BA == \B)
+	set ffholdpol pol
+
+	semioptional
+endmatch
+
+code argD argQ
+	dffholdmux = ffholdmux;
+	if (ffholdmux) {
+		SigSpec AB = port(ffholdmux, ffholdpol ? \A : \B);
+		SigSpec Y = port(ffholdmux, \Y);
+		argQ = argD;
+		argD.replace(AB, Y);
+		argQ.replace(AB, port(ffholdmux, ffholdpol ? \B : \A));
+
+		dffholdmux = ffholdmux;
+		dffholdpol = ffholdpol;
 	}
-	accept;
+endcode
+
+match ffrstmux
+	if false /* TODO: ice40 resets are actually async */
+
+	select ffrstmux->type.in($mux)
+	// ffrstmux output must have two users: ffrstmux and ff.D
+	select nusers(port(ffrstmux, \Y)) == 2
+
+	choice <IdString> BA {\B, \A}
+	// DSP48E1 only supports reset to zero
+	select port(ffrstmux, BA).is_fully_zero()
+
+	slice offset GetSize(port(ffrstmux, \Y))
+	define <IdString> AB (BA == \B ? \A : \B)
+	index <SigBit> port(ffrstmux, AB)[offset] === argD[0]
+
+	// Check that offset is consistent
+	filter !ffholdmux || ffoffset == offset
+	// Check that the rest of argD is present
+	filter GetSize(port(ffrstmux, AB)) >= offset + GetSize(argD)
+	filter port(ffrstmux, AB).extract(offset, GetSize(argD)) == argD
+
+	set ffoffset offset
+	define <bool> pol (AB == \A)
+	set ffrstpol pol
+
+	semioptional
+endmatch
+
+code argD argQ
+	dffrstmux = ffrstmux;
+	if (ffrstmux) {
+		SigSpec AB = port(ffrstmux, ffrstpol ? \A : \B);
+		SigSpec Y = port(ffrstmux, \Y);
+		argD.replace(AB, Y);
+
+		dffrstmux = ffrstmux;
+		dffrstpol = ffrstpol;
+	}
+endcode
+
+match ff
+	select ff->type.in($dff)
+	// DSP48E1 does not support clock inversion
+	select param(ff, \CLK_POLARITY).as_bool()
+
+	slice offset GetSize(port(ff, \D))
+	index <SigBit> port(ff, \D)[offset] === argD[0]
+
+	// Check that offset is consistent
+	filter (!ffholdmux && !ffrstmux) || ffoffset == offset
+	// Check that the rest of argD is present
+	filter GetSize(port(ff, \D)) >= offset + GetSize(argD)
+	filter port(ff, \D).extract(offset, GetSize(argD)) == argD
+	// Check that FF.Q is connected to CE-mux
+	filter !ffholdmux || port(ff, \Q).extract(offset, GetSize(argQ)) == argQ
+
+	set ffoffset offset
+endmatch
+
+code argQ
+	if (ff) {
+		if (clock != SigBit()) {
+			if (port(ff, \CLK) != clock)
+				reject;
+			if (param(ff, \CLK_POLARITY).as_bool() != clock_pol)
+				reject;
+		}
+		SigSpec D = port(ff, \D);
+		SigSpec Q = port(ff, \Q);
+		if (!ffholdmux) {
+			argQ = argD;
+			argQ.replace(D, Q);
+		}
+
+		for (auto c : argQ.chunks()) {
+			Const init = c.wire->attributes.at(\init, State::Sx);
+			if (!init.is_fully_undef() && !init.is_fully_zero())
+				reject;
+		}
+
+		dff = ff;
+		dffQ = argQ;
+		dffclock = port(ff, \CLK);
+		dffclock_pol = param(ff, \CLK_POLARITY).as_bool();
+	}
+	// No enable/reset mux possible without flop
+	else if (dffholdmux || dffrstmux)
+		reject;
 endcode
diff --git a/passes/pmgen/pmgen.py b/passes/pmgen/pmgen.py
index 573722d68..39a09991d 100644
--- a/passes/pmgen/pmgen.py
+++ b/passes/pmgen/pmgen.py
@@ -286,7 +286,7 @@ def process_pmgfile(f, filename):
                         block["gencode"].append(rewrite_cpp(l.rstrip()))
                     break
 
-                assert False
+                raise RuntimeError("'%s' statement not recognised on line %d" % (a[0], linenr))
 
             if block["optional"]:
                 assert not block["semioptional"]
@@ -305,7 +305,8 @@ def process_pmgfile(f, filename):
             block["states"] = set()
 
             for s in line.split()[1:]:
-                assert s in state_types[current_pattern]
+                if s not in state_types[current_pattern]:
+                    raise RuntimeError("'%s' not in state_types" % s)
                 block["states"].add(s)
 
             codetype = "code"
@@ -327,7 +328,7 @@ def process_pmgfile(f, filename):
             blocks.append(block)
             continue
 
-        assert False
+        raise RuntimeError("'%s' command not recognised" % cmd)
 
 for fn in pmgfiles:
     with open(fn, "r") as f:
@@ -452,11 +453,19 @@ with open(outfile, "w") as f:
     print("    return sigmap(cell->getPort(portname));", file=f)
     print("  }", file=f)
     print("", file=f)
+    print("  SigSpec port(Cell *cell, IdString portname, const SigSpec& defval) {", file=f)
+    print("    return sigmap(cell->connections_.at(portname, defval));", file=f)
+    print("  }", file=f)
+    print("", file=f)
 
     print("  Const param(Cell *cell, IdString paramname) {", file=f)
     print("    return cell->getParam(paramname);", file=f)
     print("  }", file=f)
     print("", file=f)
+    print("  Const param(Cell *cell, IdString paramname, const Const& defval) {", file=f)
+    print("    return cell->parameters.at(paramname, defval);", file=f)
+    print("  }", file=f)
+    print("", file=f)
 
     print("  int nusers(const SigSpec &sig) {", file=f)
     print("    pool<Cell*> users;", file=f)
diff --git a/passes/pmgen/xilinx_dsp.cc b/passes/pmgen/xilinx_dsp.cc
new file mode 100644
index 000000000..11c7e5ea8
--- /dev/null
+++ b/passes/pmgen/xilinx_dsp.cc
@@ -0,0 +1,637 @@
+/*
+ *  yosys -- Yosys Open SYnthesis Suite
+ *
+ *  Copyright (C) 2012  Clifford Wolf <clifford@clifford.at>
+ *                2019  Eddie Hung    <eddie@fpgeh.com>
+ *
+ *  Permission to use, copy, modify, and/or distribute this software for any
+ *  purpose with or without fee is hereby granted, provided that the above
+ *  copyright notice and this permission notice appear in all copies.
+ *
+ *  THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ *  WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ *  MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ *  ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ *  WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ *  ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ *  OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ *
+ */
+
+#include "kernel/yosys.h"
+#include "kernel/sigtools.h"
+
+USING_YOSYS_NAMESPACE
+PRIVATE_NAMESPACE_BEGIN
+
+#include "passes/pmgen/xilinx_dsp_pm.h"
+#include "passes/pmgen/xilinx_dsp_CREG_pm.h"
+#include "passes/pmgen/xilinx_dsp_cascade_pm.h"
+
+static Cell* addDsp(Module *module) {
+	Cell *cell = module->addCell(NEW_ID, ID(DSP48E1));
+	cell->setParam(ID(ACASCREG), 0);
+	cell->setParam(ID(ADREG), 0);
+	cell->setParam(ID(A_INPUT), Const("DIRECT"));
+	cell->setParam(ID(ALUMODEREG), 0);
+	cell->setParam(ID(AREG), 0);
+	cell->setParam(ID(BCASCREG), 0);
+	cell->setParam(ID(B_INPUT), Const("DIRECT"));
+	cell->setParam(ID(BREG), 0);
+	cell->setParam(ID(CARRYINREG), 0);
+	cell->setParam(ID(CARRYINSELREG), 0);
+	cell->setParam(ID(CREG), 0);
+	cell->setParam(ID(DREG), 0);
+	cell->setParam(ID(INMODEREG), 0);
+	cell->setParam(ID(MREG), 0);
+	cell->setParam(ID(OPMODEREG), 0);
+	cell->setParam(ID(PREG), 0);
+	cell->setParam(ID(USE_MULT), Const("NONE"));
+	cell->setParam(ID(USE_SIMD), Const("ONE48"));
+	cell->setParam(ID(USE_DPORT), Const("FALSE"));
+
+	cell->setPort(ID(D), Const(0, 25));
+	cell->setPort(ID(INMODE), Const(0, 5));
+	cell->setPort(ID(ALUMODE), Const(0, 4));
+	cell->setPort(ID(OPMODE), Const(0, 7));
+	cell->setPort(ID(CARRYINSEL), Const(0, 3));
+	cell->setPort(ID(ACIN), Const(0, 30));
+	cell->setPort(ID(BCIN), Const(0, 18));
+	cell->setPort(ID(PCIN), Const(0, 48));
+	cell->setPort(ID(CARRYIN), Const(0, 1));
+	return cell;
+}
+
+void xilinx_simd_pack(Module *module, const std::vector<Cell*> &selected_cells)
+{
+	std::deque<Cell*> simd12_add, simd12_sub;
+	std::deque<Cell*> simd24_add, simd24_sub;
+
+	for (auto cell : selected_cells) {
+		if (!cell->type.in(ID($add), ID($sub)))
+			continue;
+		SigSpec Y = cell->getPort(ID(Y));
+		if (!Y.is_chunk())
+			continue;
+		if (!Y.as_chunk().wire->get_strpool_attribute(ID(use_dsp)).count("simd"))
+			continue;
+		if (GetSize(Y) > 25)
+			continue;
+		SigSpec A = cell->getPort(ID(A));
+		SigSpec B = cell->getPort(ID(B));
+		if (GetSize(Y) <= 13) {
+			if (GetSize(A) > 12)
+				continue;
+			if (GetSize(B) > 12)
+				continue;
+			if (cell->type == ID($add))
+				simd12_add.push_back(cell);
+			else if (cell->type == ID($sub))
+				simd12_sub.push_back(cell);
+		}
+		else if (GetSize(Y) <= 25) {
+			if (GetSize(A) > 24)
+				continue;
+			if (GetSize(B) > 24)
+				continue;
+			if (cell->type == ID($add))
+				simd24_add.push_back(cell);
+			else if (cell->type == ID($sub))
+				simd24_sub.push_back(cell);
+		}
+		else
+			log_abort();
+	}
+
+	auto f12 = [module](SigSpec &AB, SigSpec &C, SigSpec &P, SigSpec &CARRYOUT, Cell *lane) {
+		SigSpec A = lane->getPort(ID(A));
+		SigSpec B = lane->getPort(ID(B));
+		SigSpec Y = lane->getPort(ID(Y));
+		A.extend_u0(12, lane->getParam(ID(A_SIGNED)).as_bool());
+		B.extend_u0(12, lane->getParam(ID(B_SIGNED)).as_bool());
+		AB.append(A);
+		C.append(B);
+		if (GetSize(Y) < 13)
+			Y.append(module->addWire(NEW_ID, 13-GetSize(Y)));
+		else
+			log_assert(GetSize(Y) == 13);
+		P.append(Y.extract(0, 12));
+		CARRYOUT.append(Y[12]);
+	};
+	auto g12 = [&f12,module](std::deque<Cell*> &simd12) {
+		while (simd12.size() > 1) {
+			SigSpec AB, C, P, CARRYOUT;
+
+			Cell *lane1 = simd12.front();
+			simd12.pop_front();
+			Cell *lane2 = simd12.front();
+			simd12.pop_front();
+			Cell *lane3 = nullptr;
+			Cell *lane4 = nullptr;
+
+			if (!simd12.empty()) {
+				lane3 = simd12.front();
+				simd12.pop_front();
+				if (!simd12.empty()) {
+					lane4 = simd12.front();
+					simd12.pop_front();
+				}
+			}
+
+			log("Analysing %s.%s for Xilinx DSP SIMD12 packing.\n", log_id(module), log_id(lane1));
+
+			Cell *cell = addDsp(module);
+			cell->setParam(ID(USE_SIMD), Const("FOUR12"));
+			// X = A:B
+			// Y = 0
+			// Z = C
+			cell->setPort(ID(OPMODE), Const::from_string("0110011"));
+
+			log_assert(lane1);
+			log_assert(lane2);
+			f12(AB, C, P, CARRYOUT, lane1);
+			f12(AB, C, P, CARRYOUT, lane2);
+			if (lane3) {
+				f12(AB, C, P, CARRYOUT, lane3);
+				if (lane4)
+					f12(AB, C, P, CARRYOUT, lane4);
+				else {
+					AB.append(Const(0, 12));
+					C.append(Const(0, 12));
+					P.append(module->addWire(NEW_ID, 12));
+					CARRYOUT.append(module->addWire(NEW_ID, 1));
+				}
+			}
+			else {
+				AB.append(Const(0, 24));
+				C.append(Const(0, 24));
+				P.append(module->addWire(NEW_ID, 24));
+				CARRYOUT.append(module->addWire(NEW_ID, 2));
+			}
+			log_assert(GetSize(AB) == 48);
+			log_assert(GetSize(C) == 48);
+			log_assert(GetSize(P) == 48);
+			log_assert(GetSize(CARRYOUT) == 4);
+			cell->setPort(ID(A), AB.extract(18, 30));
+			cell->setPort(ID(B), AB.extract(0, 18));
+			cell->setPort(ID(C), C);
+			cell->setPort(ID(P), P);
+			cell->setPort(ID(CARRYOUT), CARRYOUT);
+			if (lane1->type == ID($sub))
+				cell->setPort(ID(ALUMODE), Const::from_string("0011"));
+
+			module->remove(lane1);
+			module->remove(lane2);
+			if (lane3) module->remove(lane3);
+			if (lane4) module->remove(lane4);
+
+			module->design->select(module, cell);
+		}
+	};
+	g12(simd12_add);
+	g12(simd12_sub);
+
+	auto f24 = [module](SigSpec &AB, SigSpec &C, SigSpec &P, SigSpec &CARRYOUT, Cell *lane) {
+		SigSpec A = lane->getPort(ID(A));
+		SigSpec B = lane->getPort(ID(B));
+		SigSpec Y = lane->getPort(ID(Y));
+		A.extend_u0(24, lane->getParam(ID(A_SIGNED)).as_bool());
+		B.extend_u0(24, lane->getParam(ID(B_SIGNED)).as_bool());
+		C.append(A);
+		AB.append(B);
+		if (GetSize(Y) < 25)
+			Y.append(module->addWire(NEW_ID, 25-GetSize(Y)));
+		else
+			log_assert(GetSize(Y) == 25);
+		P.append(Y.extract(0, 24));
+		CARRYOUT.append(module->addWire(NEW_ID)); // TWO24 uses every other bit
+		CARRYOUT.append(Y[24]);
+	};
+	auto g24 = [&f24,module](std::deque<Cell*> &simd24) {
+		while (simd24.size() > 1) {
+			SigSpec AB;
+			SigSpec C;
+			SigSpec P;
+			SigSpec CARRYOUT;
+
+			Cell *lane1 = simd24.front();
+			simd24.pop_front();
+			Cell *lane2 = simd24.front();
+			simd24.pop_front();
+
+			log("Analysing %s.%s for Xilinx DSP SIMD24 packing.\n", log_id(module), log_id(lane1));
+
+			Cell *cell = addDsp(module);
+			cell->setParam(ID(USE_SIMD), Const("TWO24"));
+			// X = A:B
+			// Y = 0
+			// Z = C
+			cell->setPort(ID(OPMODE), Const::from_string("0110011"));
+
+			log_assert(lane1);
+			log_assert(lane2);
+			f24(AB, C, P, CARRYOUT, lane1);
+			f24(AB, C, P, CARRYOUT, lane2);
+			log_assert(GetSize(AB) == 48);
+			log_assert(GetSize(C) == 48);
+			log_assert(GetSize(P) == 48);
+			log_assert(GetSize(CARRYOUT) == 4);
+			cell->setPort(ID(A), AB.extract(18, 30));
+			cell->setPort(ID(B), AB.extract(0, 18));
+			cell->setPort(ID(C), C);
+			cell->setPort(ID(P), P);
+			cell->setPort(ID(CARRYOUT), CARRYOUT);
+			if (lane1->type == ID($sub))
+				cell->setPort(ID(ALUMODE), Const::from_string("0011"));
+
+			module->remove(lane1);
+			module->remove(lane2);
+
+			module->design->select(module, cell);
+		}
+	};
+	g24(simd24_add);
+	g24(simd24_sub);
+}
+
+void xilinx_dsp_pack(xilinx_dsp_pm &pm)
+{
+	auto &st = pm.st_xilinx_dsp_pack;
+
+	log("Analysing %s.%s for Xilinx DSP packing.\n", log_id(pm.module), log_id(st.dsp));
+
+	log_debug("preAdd:     %s\n", log_id(st.preAdd, "--"));
+	log_debug("ffAD:       %s %s %s\n", log_id(st.ffAD, "--"), log_id(st.ffADcemux, "--"), log_id(st.ffADrstmux, "--"));
+	log_debug("ffA2:       %s %s %s\n", log_id(st.ffA2, "--"), log_id(st.ffA2cemux, "--"), log_id(st.ffA2rstmux, "--"));
+	log_debug("ffA1:       %s %s %s\n", log_id(st.ffA1, "--"), log_id(st.ffA1cemux, "--"), log_id(st.ffA1rstmux, "--"));
+	log_debug("ffB2:       %s %s %s\n", log_id(st.ffB2, "--"), log_id(st.ffB2cemux, "--"), log_id(st.ffB2rstmux, "--"));
+	log_debug("ffB1:       %s %s %s\n", log_id(st.ffB1, "--"), log_id(st.ffB1cemux, "--"), log_id(st.ffB1rstmux, "--"));
+	log_debug("ffD:        %s %s %s\n", log_id(st.ffD, "--"), log_id(st.ffDcemux, "--"), log_id(st.ffDrstmux, "--"));
+	log_debug("dsp:        %s\n", log_id(st.dsp, "--"));
+	log_debug("ffM:        %s %s %s\n", log_id(st.ffM, "--"), log_id(st.ffMcemux, "--"), log_id(st.ffMrstmux, "--"));
+	log_debug("postAdd:    %s\n", log_id(st.postAdd, "--"));
+	log_debug("postAddMux: %s\n", log_id(st.postAddMux, "--"));
+	log_debug("ffP:        %s %s %s\n", log_id(st.ffP, "--"), log_id(st.ffPcemux, "--"), log_id(st.ffPrstmux, "--"));
+	log_debug("overflow:   %s\n", log_id(st.overflow, "--"));
+
+	Cell *cell = st.dsp;
+
+	if (st.preAdd) {
+		log("  preadder %s (%s)\n", log_id(st.preAdd), log_id(st.preAdd->type));
+		bool A_SIGNED = st.preAdd->getParam(ID(A_SIGNED)).as_bool();
+		bool D_SIGNED = st.preAdd->getParam(ID(B_SIGNED)).as_bool();
+		if (st.sigA == st.preAdd->getPort(ID(B)))
+			std::swap(A_SIGNED, D_SIGNED);
+		st.sigA.extend_u0(30, A_SIGNED);
+		st.sigD.extend_u0(25, D_SIGNED);
+		cell->setPort(ID(A), st.sigA);
+		cell->setPort(ID(D), st.sigD);
+		cell->setPort(ID(INMODE), Const::from_string("00100"));
+
+		if (st.ffAD) {
+			if (st.ffADcemux) {
+				SigSpec S = st.ffADcemux->getPort(ID(S));
+				cell->setPort(ID(CEAD), st.ffADcepol ? S : pm.module->Not(NEW_ID, S));
+			}
+			else
+				cell->setPort(ID(CEAD), State::S1);
+			cell->setParam(ID(ADREG), 1);
+		}
+
+		cell->setParam(ID(USE_DPORT), Const("TRUE"));
+
+		pm.autoremove(st.preAdd);
+	}
+	if (st.postAdd) {
+		log("  postadder %s (%s)\n", log_id(st.postAdd), log_id(st.postAdd->type));
+
+		SigSpec &opmode = cell->connections_.at(ID(OPMODE));
+		if (st.postAddMux) {
+			log_assert(st.ffP);
+			opmode[4] = st.postAddMux->getPort(ID(S));
+			pm.autoremove(st.postAddMux);
+		}
+		else if (st.ffP && st.sigC == st.sigP)
+			opmode[4] = State::S0;
+		else
+			opmode[4] = State::S1;
+		opmode[6] = State::S0;
+		opmode[5] = State::S1;
+
+		if (opmode[4] != State::S0) {
+			if (st.postAddMuxAB == ID(A))
+				st.sigC.extend_u0(48, st.postAdd->getParam(ID(B_SIGNED)).as_bool());
+			else
+				st.sigC.extend_u0(48, st.postAdd->getParam(ID(A_SIGNED)).as_bool());
+			cell->setPort(ID(C), st.sigC);
+		}
+
+		pm.autoremove(st.postAdd);
+	}
+	if (st.overflow) {
+		log("  overflow %s (%s)\n", log_id(st.overflow), log_id(st.overflow->type));
+		cell->setParam(ID(USE_PATTERN_DETECT), Const("PATDET"));
+		cell->setParam(ID(SEL_PATTERN), Const("PATTERN"));
+		cell->setParam(ID(SEL_MASK), Const("MASK"));
+
+		if (st.overflow->type == ID($ge)) {
+			Const B = st.overflow->getPort(ID(B)).as_const();
+			log_assert(std::count(B.bits.begin(), B.bits.end(), State::S1) == 1);
+			// Since B is an exact power of 2, subtract 1
+			//   by inverting all bits up until hitting
+			//   that one hi bit
+			for (auto &b : B.bits)
+				if (b == State::S0) b = State::S1;
+				else if (b == State::S1) {
+					b = State::S0;
+					break;
+				}
+			B.extu(48);
+
+			cell->setParam(ID(MASK), B);
+			cell->setParam(ID(PATTERN), Const(0, 48));
+			cell->setPort(ID(OVERFLOW), st.overflow->getPort(ID(Y)));
+		}
+		else log_abort();
+
+		pm.autoremove(st.overflow);
+	}
+
+	if (st.clock != SigBit())
+	{
+		cell->setPort(ID(CLK), st.clock);
+
+		auto f = [&pm,cell](SigSpec &A, Cell* ff, Cell* cemux, bool cepol, IdString ceport, Cell* rstmux, bool rstpol, IdString rstport) {
+			SigSpec D = ff->getPort(ID(D));
+			SigSpec Q = pm.sigmap(ff->getPort(ID(Q)));
+			if (!A.empty())
+				A.replace(Q, D);
+			if (rstmux) {
+				SigSpec Y = rstmux->getPort(ID(Y));
+				SigSpec AB = rstmux->getPort(rstpol ? ID(A) : ID(B));
+				if (!A.empty())
+					A.replace(Y, AB);
+				if (rstport != IdString()) {
+					SigSpec S = rstmux->getPort(ID(S));
+					cell->setPort(rstport, rstpol ? S : pm.module->Not(NEW_ID, S));
+				}
+			}
+			else if (rstport != IdString())
+				cell->setPort(rstport, State::S0);
+			if (cemux) {
+				SigSpec Y = cemux->getPort(ID(Y));
+				SigSpec BA = cemux->getPort(cepol ? ID(B) : ID(A));
+				SigSpec S = cemux->getPort(ID(S));
+				if (!A.empty())
+					A.replace(Y, BA);
+				cell->setPort(ceport, cepol ? S : pm.module->Not(NEW_ID, S));
+			}
+			else
+				cell->setPort(ceport, State::S1);
+
+			for (auto c : Q.chunks()) {
+				auto it = c.wire->attributes.find(ID(init));
+				if (it == c.wire->attributes.end())
+					continue;
+				for (int i = c.offset; i < c.offset+c.width; i++) {
+					log_assert(it->second[i] == State::S0 || it->second[i] == State::Sx);
+					it->second[i] = State::Sx;
+				}
+			}
+		};
+
+		if (st.ffA2) {
+			SigSpec A = cell->getPort(ID(A));
+			f(A, st.ffA2, st.ffA2cemux, st.ffA2cepol, ID(CEA2), st.ffA2rstmux, st.ffArstpol, ID(RSTA));
+			if (st.ffA1) {
+				f(A, st.ffA1, st.ffA1cemux, st.ffA1cepol, ID(CEA1), st.ffA1rstmux, st.ffArstpol, IdString());
+				cell->setParam(ID(AREG), 2);
+				cell->setParam(ID(ACASCREG), 2);
+			}
+			else {
+				cell->setParam(ID(AREG), 1);
+				cell->setParam(ID(ACASCREG), 1);
+			}
+			pm.add_siguser(A, cell);
+			cell->setPort(ID(A), A);
+		}
+		if (st.ffB2) {
+			SigSpec B = cell->getPort(ID(B));
+			f(B, st.ffB2, st.ffB2cemux, st.ffB2cepol, ID(CEB2), st.ffB2rstmux, st.ffBrstpol, ID(RSTB));
+			if (st.ffB1) {
+				f(B, st.ffB1, st.ffB1cemux, st.ffB1cepol, ID(CEB1), st.ffB1rstmux, st.ffBrstpol, IdString());
+				cell->setParam(ID(BREG), 2);
+				cell->setParam(ID(BCASCREG), 2);
+			}
+			else {
+				cell->setParam(ID(BREG), 1);
+				cell->setParam(ID(BCASCREG), 1);
+			}
+			pm.add_siguser(B, cell);
+			cell->setPort(ID(B), B);
+		}
+		if (st.ffD) {
+			SigSpec D = cell->getPort(ID(D));
+			f(D, st.ffD, st.ffDcemux, st.ffDcepol, ID(CED), st.ffDrstmux, st.ffDrstpol, ID(RSTD));
+			pm.add_siguser(D, cell);
+			cell->setPort(ID(D), D);
+			cell->setParam(ID(DREG), 1);
+		}
+		if (st.ffM) {
+			SigSpec M; // unused
+			f(M, st.ffM, st.ffMcemux, st.ffMcepol, ID(CEM), st.ffMrstmux, st.ffMrstpol, ID(RSTM));
+			st.ffM->connections_.at(ID(Q)).replace(st.sigM, pm.module->addWire(NEW_ID, GetSize(st.sigM)));
+			cell->setParam(ID(MREG), State::S1);
+		}
+		if (st.ffP) {
+			SigSpec P; // unused
+			f(P, st.ffP, st.ffPcemux, st.ffPcepol, ID(CEP), st.ffPrstmux, st.ffPrstpol, ID(RSTP));
+			st.ffP->connections_.at(ID(Q)).replace(st.sigP, pm.module->addWire(NEW_ID, GetSize(st.sigP)));
+			cell->setParam(ID(PREG), State::S1);
+		}
+
+		log("  clock: %s (%s)", log_signal(st.clock), "posedge");
+
+		if (st.ffA2) {
+			log(" ffA2:%s", log_id(st.ffA2));
+			if (st.ffA1)
+				log(" ffA1:%s", log_id(st.ffA1));
+		}
+
+		if (st.ffAD)
+			log(" ffAD:%s", log_id(st.ffAD));
+
+		if (st.ffB2) {
+			log(" ffB2:%s", log_id(st.ffB2));
+			if (st.ffB1)
+				log(" ffB1:%s", log_id(st.ffB1));
+		}
+
+		if (st.ffD)
+			log(" ffD:%s", log_id(st.ffD));
+
+		if (st.ffM)
+			log(" ffM:%s", log_id(st.ffM));
+
+		if (st.ffP)
+			log(" ffP:%s", log_id(st.ffP));
+	}
+	log("\n");
+
+	SigSpec P = st.sigP;
+	if (GetSize(P) < 48)
+		P.append(pm.module->addWire(NEW_ID, 48-GetSize(P)));
+	cell->setPort(ID(P), P);
+
+	pm.blacklist(cell);
+}
+
+void xilinx_dsp_packC(xilinx_dsp_CREG_pm &pm)
+{
+	auto &st = pm.st_xilinx_dsp_packC;
+
+	log_debug("Analysing %s.%s for Xilinx DSP packing (CREG).\n", log_id(pm.module), log_id(st.dsp));
+	log_debug("ffC:        %s %s %s\n", log_id(st.ffC, "--"), log_id(st.ffCcemux, "--"), log_id(st.ffCrstmux, "--"));
+
+	Cell *cell = st.dsp;
+
+	if (st.clock != SigBit())
+	{
+		cell->setPort(ID(CLK), st.clock);
+
+		auto f = [&pm,cell](SigSpec &A, Cell* ff, Cell* cemux, bool cepol, IdString ceport, Cell* rstmux, bool rstpol, IdString rstport) {
+			SigSpec D = ff->getPort(ID(D));
+			SigSpec Q = pm.sigmap(ff->getPort(ID(Q)));
+			if (!A.empty())
+				A.replace(Q, D);
+			if (rstmux) {
+				SigSpec Y = rstmux->getPort(ID(Y));
+				SigSpec AB = rstmux->getPort(rstpol ? ID(A) : ID(B));
+				if (!A.empty())
+					A.replace(Y, AB);
+				if (rstport != IdString()) {
+					SigSpec S = rstmux->getPort(ID(S));
+					cell->setPort(rstport, rstpol ? S : pm.module->Not(NEW_ID, S));
+				}
+			}
+			else if (rstport != IdString())
+				cell->setPort(rstport, State::S0);
+			if (cemux) {
+				SigSpec Y = cemux->getPort(ID(Y));
+				SigSpec BA = cemux->getPort(cepol ? ID(B) : ID(A));
+				SigSpec S = cemux->getPort(ID(S));
+				if (!A.empty())
+					A.replace(Y, BA);
+				cell->setPort(ceport, cepol ? S : pm.module->Not(NEW_ID, S));
+			}
+			else
+				cell->setPort(ceport, State::S1);
+
+			for (auto c : Q.chunks()) {
+				auto it = c.wire->attributes.find(ID(init));
+				if (it == c.wire->attributes.end())
+					continue;
+				for (int i = c.offset; i < c.offset+c.width; i++) {
+					log_assert(it->second[i] == State::S0 || it->second[i] == State::Sx);
+					it->second[i] = State::Sx;
+				}
+			}
+		};
+
+		if (st.ffC) {
+			SigSpec C = cell->getPort(ID(C));
+			f(C, st.ffC, st.ffCcemux, st.ffCcepol, ID(CEC), st.ffCrstmux, st.ffCrstpol, ID(RSTC));
+			pm.add_siguser(C, cell);
+			cell->setPort(ID(C), C);
+			cell->setParam(ID(CREG), 1);
+		}
+
+		log("  clock: %s (%s)", log_signal(st.clock), "posedge");
+
+		if (st.ffC)
+			log(" ffC:%s", log_id(st.ffC));
+		log("\n");
+	}
+
+	pm.blacklist(cell);
+}
+
+struct XilinxDspPass : public Pass {
+	XilinxDspPass() : Pass("xilinx_dsp", "Xilinx: pack resources into DSPs") { }
+	void help() YS_OVERRIDE
+	{
+		//   |---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|
+		log("\n");
+		log("    xilinx_dsp [options] [selection]\n");
+		log("\n");
+		log("Pack input registers (A2, A1, B2, B1, C, D, AD; with optional enable/reset),\n");
+		log("pipeline registers (M; with optional enable/reset), output registers (P; with\n");
+		log("optional enable/reset), pre-adder and/or post-adder into Xilinx DSP resources.\n");
+		log("\n");
+		log("Multiply-accumulate operations using the post-adder with feedback on the 'C'\n");
+		log("input will be folded into the DSP. In this scenario only, the 'C' input can be\n");
+		log("used to override the current accumulation result with a new value, which will\n");
+		log("be added to the multiplier result to form the next accumulation result.\n");
+		log("\n");
+		log("Use of the dedicated 'PCOUT' -> 'PCIN' cascade path is detected for 'P' -> 'C'\n");
+		log("connections (optionally, where 'P' is right-shifted by 17-bits and used as an\n");
+		log("input to the post-adder -- a pattern common for summing partial products to\n");
+		log("implement wide multipliers). Limited support also exists for similar cascading\n");
+		log("for A and B using '[AB]COUT' -> '[AB]CIN'. Currently, cascade chains are limited\n");
+		log("to a maximum length of 20 cells, corresponding to the smallest Xilinx 7 Series\n");
+		log("device.\n");
+		log("\n");
+		log("\n");
+		log("Experimental feature: addition/subtractions less than 12 or 24 bits with the\n");
+		log("'(* use_dsp=\"simd\" *)' attribute attached to the output wire or attached to\n");
+		log("the add/subtract operator will cause those operations to be implemented using\n");
+		log("the 'SIMD' feature of DSPs.\n");
+		log("\n");
+		log("Experimental feature: the presence of a `$ge' cell attached to the registered\n");
+		log("P output implementing the operation \"(P >= <power-of-2>)\" will be transformed\n");
+		log("into using the DSP48E1's pattern detector feature for overflow detection.\n");
+		log("\n");
+	}
+	void execute(std::vector<std::string> args, RTLIL::Design *design) YS_OVERRIDE
+	{
+		log_header(design, "Executing XILINX_DSP pass (pack resources into DSPs).\n");
+
+		size_t argidx;
+		for (argidx = 1; argidx < args.size(); argidx++)
+		{
+			// if (args[argidx] == "-singleton") {
+			// 	singleton_mode = true;
+			// 	continue;
+			// }
+			break;
+		}
+		extra_args(args, argidx, design);
+
+		for (auto module : design->selected_modules()) {
+			xilinx_simd_pack(module, module->selected_cells());
+
+			{
+				xilinx_dsp_pm pm(module, module->selected_cells());
+				pm.run_xilinx_dsp_pack(xilinx_dsp_pack);
+			}
+			// Separating out CREG packing is necessary since there
+			//   is no guarantee that the cell ordering corresponds
+			//   to the "expected" case (i.e. the order in which
+			//   they appear in the source) thus the possiblity
+			//   existed that a register got packed as CREG into a
+			//   downstream DSP that should have otherwise been a
+			//   PREG of an upstream DSP that had not been pattern
+			//   matched yet
+			{
+				xilinx_dsp_CREG_pm pm(module, module->selected_cells());
+				pm.run_xilinx_dsp_packC(xilinx_dsp_packC);
+			}
+			{
+				xilinx_dsp_cascade_pm pm(module, module->selected_cells());
+				pm.run_xilinx_dsp_cascade();
+			}
+		}
+	}
+} XilinxDspPass;
+
+PRIVATE_NAMESPACE_END
diff --git a/passes/pmgen/xilinx_dsp.pmg b/passes/pmgen/xilinx_dsp.pmg
new file mode 100644
index 000000000..3d0b1f2c3
--- /dev/null
+++ b/passes/pmgen/xilinx_dsp.pmg
@@ -0,0 +1,587 @@
+pattern xilinx_dsp_pack
+
+state <SigBit> clock
+state <SigSpec> sigA sigB sigC sigD sigM sigP
+state <IdString> postAddAB postAddMuxAB
+state <bool> ffA1cepol ffA2cepol ffADcepol ffB1cepol ffB2cepol ffDcepol ffMcepol ffPcepol
+state <bool> ffArstpol ffADrstpol ffBrstpol ffDrstpol ffMrstpol ffPrstpol
+
+state <Cell*> ffAD ffADcemux ffADrstmux ffA1 ffA1cemux ffA1rstmux ffA2 ffA2cemux ffA2rstmux
+state <Cell*> ffB1 ffB1cemux ffB1rstmux ffB2 ffB2cemux ffB2rstmux
+state <Cell*> ffD ffDcemux ffDrstmux ffM ffMcemux ffMrstmux ffP ffPcemux ffPrstmux
+
+// subpattern
+state <SigSpec> argQ argD
+state <bool> ffcepol ffrstpol
+state <int> ffoffset
+udata <SigSpec> dffD dffQ
+udata <SigBit> dffclock
+udata <Cell*> dff dffcemux dffrstmux
+udata <bool> dffcepol dffrstpol
+
+match dsp
+	select dsp->type.in(\DSP48E1)
+endmatch
+
+code sigA sigB sigC sigD sigM clock
+	auto unextend = [](const SigSpec &sig) {
+		int i;
+		for (i = GetSize(sig)-1; i > 0; i--)
+			if (sig[i] != sig[i-1])
+				break;
+		// Do not remove non-const sign bit
+		if (sig[i].wire)
+			++i;
+		return sig.extract(0, i);
+	};
+	sigA = unextend(port(dsp, \A));
+	sigB = unextend(port(dsp, \B));
+
+	sigC = port(dsp, \C, SigSpec());
+	sigD = port(dsp, \D, SigSpec());
+
+	SigSpec P = port(dsp, \P);
+	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)
+				break;
+			sigM.append(P[i]);
+		}
+		log_assert(nusers(P.extract_end(i)) <= 1);
+	}
+	else
+		sigM = P;
+	// This sigM could have no users if downstream $add
+	//   is narrower than $mul result, for example
+	if (sigM.empty())
+		reject;
+
+	clock = port(dsp, \CLK, SigBit());
+endcode
+
+code argQ ffAD ffADcemux ffADrstmux ffADcepol ffADrstpol sigA clock
+	if (param(dsp, \ADREG).as_int() == 0) {
+		argQ = sigA;
+		subpattern(in_dffe);
+		if (dff) {
+			ffAD = dff;
+			clock = dffclock;
+			if (dffrstmux) {
+				ffADrstmux = dffrstmux;
+				ffADrstpol = dffrstpol;
+			}
+			if (dffcemux) {
+				ffADcemux = dffcemux;
+				ffADcepol = dffcepol;
+			}
+			sigA = dffD;
+		}
+	}
+endcode
+
+match preAdd
+	if sigD.empty() || sigD.is_fully_zero()
+	// Ensure that preAdder not already used
+	if param(dsp, \USE_DPORT, Const("FALSE")).decode_string() == "FALSE"
+	if port(dsp, \INMODE, Const(0, 5)).is_fully_zero()
+
+	select preAdd->type.in($add)
+	// Output has to be 25 bits or less
+	select GetSize(port(preAdd, \Y)) <= 25
+	select nusers(port(preAdd, \Y)) == 2
+	choice <IdString> AB {\A, \B}
+	// A port has to be 30 bits or less
+	select GetSize(port(preAdd, AB)) <= 30
+	define <IdString> BA (AB == \A ? \B : \A)
+	// D port has to be 25 bits or less
+	select GetSize(port(preAdd, BA)) <= 25
+	index <SigSpec> port(preAdd, \Y) === sigA
+
+	optional
+endmatch
+
+code sigA sigD
+	if (preAdd) {
+		sigA = port(preAdd, \A);
+		sigD = port(preAdd, \B);
+		if (GetSize(sigA) < GetSize(sigD))
+			std::swap(sigA, sigD);
+	}
+endcode
+
+code argQ ffAD ffADcemux ffADrstmux ffADcepol ffADrstpol sigA clock ffA2 ffA2cemux ffA2rstmux ffA2cepol ffArstpol ffA1 ffA1cemux ffA1rstmux ffA1cepol
+	// Only search for ffA2 if there was a pre-adder
+	//   (otherwise ffA2 would have been matched as ffAD)
+	if (preAdd) {
+		if (param(dsp, \AREG).as_int() == 0) {
+			argQ = sigA;
+			subpattern(in_dffe);
+			if (dff) {
+				ffA2 = dff;
+				clock = dffclock;
+				if (dffrstmux) {
+					ffA2rstmux = dffrstmux;
+					ffArstpol = dffrstpol;
+				}
+				if (dffcemux) {
+					ffA2cepol = dffcepol;
+					ffA2cemux = dffcemux;
+				}
+				sigA = dffD;
+			}
+		}
+	}
+	// And if there wasn't a pre-adder,
+	//   move AD register to A
+	else if (ffAD) {
+		log_assert(!ffA2 && !ffA2cemux && !ffA2rstmux);
+		std::swap(ffA2, ffAD);
+		std::swap(ffA2cemux, ffADcemux);
+		std::swap(ffA2rstmux, ffADrstmux);
+		ffA2cepol = ffADcepol;
+		ffArstpol = ffADrstpol;
+	}
+
+	// Now attempt to match A1
+	if (ffA2) {
+		argQ = sigA;
+		subpattern(in_dffe);
+		if (dff) {
+			if ((ffA2rstmux != nullptr) ^ (dffrstmux != nullptr))
+				goto ffA1_end;
+			if (dffrstmux) {
+				if (ffArstpol != dffrstpol)
+					goto ffA1_end;
+				if (port(ffA2rstmux, \S) != port(dffrstmux, \S))
+					goto ffA1_end;
+				ffA1rstmux = dffrstmux;
+			}
+
+			ffA1 = dff;
+			clock = dffclock;
+
+			if (dffcemux) {
+				ffA1cemux = dffcemux;
+				ffA1cepol = dffcepol;
+			}
+			sigA = dffD;
+
+ffA1_end:		;
+		}
+	}
+endcode
+
+code argQ ffB2 ffB2cemux ffB2rstmux ffB2cepol ffBrstpol sigB clock ffB1 ffB1cemux ffB1rstmux ffB1cepol
+	if (param(dsp, \BREG).as_int() == 0) {
+		argQ = sigB;
+		subpattern(in_dffe);
+		if (dff) {
+			ffB2 = dff;
+			clock = dffclock;
+			if (dffrstmux) {
+				ffB2rstmux = dffrstmux;
+				ffBrstpol = dffrstpol;
+			}
+			if (dffcemux) {
+				ffB2cemux = dffcemux;
+				ffB2cepol = dffcepol;
+			}
+			sigB = dffD;
+
+			// Now attempt to match B1
+			if (ffB2) {
+				argQ = sigB;
+				subpattern(in_dffe);
+				if (dff) {
+					if ((ffB2rstmux != nullptr) ^ (dffrstmux != nullptr))
+						goto ffB1_end;
+					if (dffrstmux) {
+						if (ffBrstpol != dffrstpol)
+							goto ffB1_end;
+						if (port(ffB2rstmux, \S) != port(dffrstmux, \S))
+							goto ffB1_end;
+						ffB1rstmux = dffrstmux;
+					}
+
+					ffB1 = dff;
+					clock = dffclock;
+
+					if (dffcemux) {
+						ffB1cemux = dffcemux;
+						ffB1cepol = dffcepol;
+					}
+					sigB = dffD;
+
+ffB1_end:				;
+				}
+			}
+
+		}
+	}
+endcode
+
+code argQ ffD ffDcemux ffDrstmux ffDcepol ffDrstpol sigD clock
+	if (param(dsp, \DREG).as_int() == 0) {
+		argQ = sigD;
+		subpattern(in_dffe);
+		if (dff) {
+			ffD = dff;
+			clock = dffclock;
+			if (dffrstmux) {
+				ffDrstmux = dffrstmux;
+				ffDrstpol = dffrstpol;
+			}
+			if (dffcemux) {
+				ffDcemux = dffcemux;
+				ffDcepol = dffcepol;
+			}
+			sigD = dffD;
+		}
+	}
+endcode
+
+code argD ffM ffMcemux ffMrstmux ffMcepol ffMrstpol sigM sigP clock
+	if (param(dsp, \MREG).as_int() == 0 && nusers(sigM) == 2) {
+		argD = sigM;
+		subpattern(out_dffe);
+		if (dff) {
+			ffM = dff;
+			clock = dffclock;
+			if (dffrstmux) {
+				ffMrstmux = dffrstmux;
+				ffMrstpol = dffrstpol;
+			}
+			if (dffcemux) {
+				ffMcemux = dffcemux;
+				ffMcepol = dffcepol;
+			}
+			sigM = dffQ;
+		}
+	}
+	sigP = sigM;
+endcode
+
+match postAdd
+	// Ensure that Z mux is not already used
+	if port(dsp, \OPMODE, SigSpec()).extract(4,3).is_fully_zero()
+
+	select postAdd->type.in($add)
+	select GetSize(port(postAdd, \Y)) <= 48
+	choice <IdString> AB {\A, \B}
+	select nusers(port(postAdd, AB)) <= 3
+	filter ffMcemux || nusers(port(postAdd, AB)) == 2
+	filter !ffMcemux || nusers(port(postAdd, AB)) == 3
+
+	index <SigBit> port(postAdd, AB)[0] === sigP[0]
+	filter GetSize(port(postAdd, AB)) >= GetSize(sigP)
+	filter port(postAdd, AB).extract(0, GetSize(sigP)) == sigP
+	filter port(postAdd, AB).extract_end(GetSize(sigP)) == SigSpec(sigP[GetSize(sigP)-1], GetSize(port(postAdd, AB))-GetSize(sigP))
+	set postAddAB AB
+	optional
+endmatch
+
+code sigC sigP
+	if (postAdd) {
+		sigC = port(postAdd, postAddAB == \A ? \B : \A);
+		sigP = port(postAdd, \Y);
+	}
+endcode
+
+code argD ffP ffPcemux ffPrstmux ffPcepol ffPrstpol sigP clock
+	if (param(dsp, \PREG).as_int() == 0) {
+		int users = 2;
+		// If ffMcemux and no postAdd new-value net must have three users: ffMcemux, ffM and ffPcemux
+		if (ffMcemux && !postAdd) users++;
+		if (nusers(sigP) == users) {
+			argD = sigP;
+			subpattern(out_dffe);
+			if (dff) {
+				ffP = dff;
+				clock = dffclock;
+				if (dffrstmux) {
+					ffPrstmux = dffrstmux;
+					ffPrstpol = dffrstpol;
+				}
+				if (dffcemux) {
+					ffPcemux = dffcemux;
+					ffPcepol = dffcepol;
+				}
+				sigP = dffQ;
+			}
+		}
+	}
+endcode
+
+match postAddMux
+	if postAdd
+	if ffP
+	select postAddMux->type.in($mux)
+	select nusers(port(postAddMux, \Y)) == 2
+	choice <IdString> AB {\A, \B}
+	index <SigSpec> port(postAddMux, AB) === sigP
+	index <SigSpec> port(postAddMux, \Y) === sigC
+	set postAddMuxAB AB
+	optional
+endmatch
+
+code sigC
+	if (postAddMux)
+		sigC = port(postAddMux, postAddMuxAB == \A ? \B : \A);
+endcode
+
+match overflow
+	if ffP
+	if param(dsp, \USE_PATTERN_DETECT, Const("NO_PATDET")).decode_string() == "NO_PATDET"
+	select overflow->type.in($ge)
+	select GetSize(port(overflow, \Y)) <= 48
+	select port(overflow, \B).is_fully_const()
+	define <Const> B port(overflow, \B).as_const()
+	select std::count(B.bits.begin(), B.bits.end(), State::S1) == 1
+	index <SigSpec> port(overflow, \A) === sigP
+	optional
+endmatch
+
+code
+	accept;
+endcode
+
+// #######################
+
+subpattern in_dffe
+arg argD argQ clock
+
+code
+	dff = nullptr;
+	for (auto c : argQ.chunks()) {
+		if (!c.wire)
+			reject;
+		if (c.wire->get_bool_attribute(\keep))
+			reject;
+		Const init = c.wire->attributes.at(\init, State::Sx);
+		if (!init.is_fully_undef() && !init.is_fully_zero())
+			reject;
+	}
+endcode
+
+match ff
+	select ff->type.in($dff)
+	// DSP48E1 does not support clock inversion
+	select param(ff, \CLK_POLARITY).as_bool()
+
+	slice offset GetSize(port(ff, \D))
+	index <SigBit> port(ff, \Q)[offset] === argQ[0]
+
+	// Check that the rest of argQ is present
+	filter GetSize(port(ff, \Q)) >= offset + GetSize(argQ)
+	filter port(ff, \Q).extract(offset, GetSize(argQ)) == argQ
+
+	set ffoffset offset
+endmatch
+
+code argQ argD
+{
+	if (clock != SigBit() && port(ff, \CLK) != clock)
+		reject;
+
+	SigSpec Q = port(ff, \Q);
+	dff = ff;
+	dffclock = port(ff, \CLK);
+	dffD = argQ;
+	argD = port(ff, \D);
+	argQ = Q;
+	dffD.replace(argQ, argD);
+	// Only search for ffrstmux if dffD only
+	//   has two (ff, ffrstmux) users
+	if (nusers(dffD) > 2)
+		argD = SigSpec();
+}
+endcode
+
+match ffrstmux
+	if !argD.empty()
+	select ffrstmux->type.in($mux)
+	index <SigSpec> port(ffrstmux, \Y) === argD
+
+	choice <IdString> BA {\B, \A}
+	// DSP48E1 only supports reset to zero
+	select port(ffrstmux, BA).is_fully_zero()
+
+	define <bool> pol (BA == \B)
+	set ffrstpol pol
+	semioptional
+endmatch
+
+code argD
+	if (ffrstmux) {
+		dffrstmux = ffrstmux;
+		dffrstpol = ffrstpol;
+		argD = port(ffrstmux, ffrstpol ? \A : \B);
+		dffD.replace(port(ffrstmux, \Y), argD);
+
+		// Only search for ffcemux if argQ has at
+		//   least 3 users (ff, <upstream>, ffrstmux) and
+		//   dffD only has two (ff, ffrstmux)
+		if (!(nusers(argQ) >= 3 && nusers(dffD) == 2))
+			argD = SigSpec();
+	}
+	else
+		dffrstmux = nullptr;
+endcode
+
+match ffcemux
+	if !argD.empty()
+	select ffcemux->type.in($mux)
+	index <SigSpec> port(ffcemux, \Y) === argD
+	choice <IdString> AB {\A, \B}
+	index <SigSpec> port(ffcemux, AB) === argQ
+	define <bool> pol (AB == \A)
+	set ffcepol pol
+	semioptional
+endmatch
+
+code argD
+	if (ffcemux) {
+		dffcemux = ffcemux;
+		dffcepol = ffcepol;
+		argD = port(ffcemux, ffcepol ? \B : \A);
+		dffD.replace(port(ffcemux, \Y), argD);
+	}
+	else
+		dffcemux = nullptr;
+endcode
+
+// #######################
+
+subpattern out_dffe
+arg argD argQ clock
+
+code
+	dff = nullptr;
+	for (auto c : argD.chunks())
+		if (c.wire->get_bool_attribute(\keep))
+			reject;
+endcode
+
+match ffcemux
+	select ffcemux->type.in($mux)
+	// ffcemux output must have two users: ffcemux and ff.D
+	select nusers(port(ffcemux, \Y)) == 2
+
+	choice <IdString> AB {\A, \B}
+	// keep-last-value net must have at least three users: ffcemux, ff, downstream sink(s)
+	select nusers(port(ffcemux, AB)) >= 3
+
+	slice offset GetSize(port(ffcemux, \Y))
+	define <IdString> BA (AB == \A ? \B : \A)
+	index <SigBit> port(ffcemux, BA)[offset] === argD[0]
+
+	// Check that the rest of argD is present
+	filter GetSize(port(ffcemux, BA)) >= offset + GetSize(argD)
+	filter port(ffcemux, BA).extract(offset, GetSize(argD)) == argD
+
+	set ffoffset offset
+	define <bool> pol (AB == \A)
+	set ffcepol pol
+
+	semioptional
+endmatch
+
+code argD argQ
+	dffcemux = ffcemux;
+	if (ffcemux) {
+		SigSpec BA = port(ffcemux, ffcepol ? \B : \A);
+		SigSpec Y = port(ffcemux, \Y);
+		argQ = argD;
+		argD.replace(BA, Y);
+		argQ.replace(BA, port(ffcemux, ffcepol ? \A : \B));
+
+		dffcemux = ffcemux;
+		dffcepol = ffcepol;
+	}
+endcode
+
+match ffrstmux
+	select ffrstmux->type.in($mux)
+	// ffrstmux output must have two users: ffrstmux and ff.D
+	select nusers(port(ffrstmux, \Y)) == 2
+
+	choice <IdString> BA {\B, \A}
+	// DSP48E1 only supports reset to zero
+	select port(ffrstmux, BA).is_fully_zero()
+
+	slice offset GetSize(port(ffrstmux, \Y))
+	define <IdString> AB (BA == \B ? \A : \B)
+	index <SigBit> port(ffrstmux, AB)[offset] === argD[0]
+
+	// Check that offset is consistent
+	filter !ffcemux || ffoffset == offset
+	// Check that the rest of argD is present
+	filter GetSize(port(ffrstmux, AB)) >= offset + GetSize(argD)
+	filter port(ffrstmux, AB).extract(offset, GetSize(argD)) == argD
+
+	set ffoffset offset
+	define <bool> pol (AB == \A)
+	set ffrstpol pol
+
+	semioptional
+endmatch
+
+code argD argQ
+	dffrstmux = ffrstmux;
+	if (ffrstmux) {
+		SigSpec AB = port(ffrstmux, ffrstpol ? \A : \B);
+		SigSpec Y = port(ffrstmux, \Y);
+		argD.replace(AB, Y);
+
+		dffrstmux = ffrstmux;
+		dffrstpol = ffrstpol;
+	}
+endcode
+
+match ff
+	select ff->type.in($dff)
+	// DSP48E1 does not support clock inversion
+	select param(ff, \CLK_POLARITY).as_bool()
+
+	slice offset GetSize(port(ff, \D))
+	index <SigBit> port(ff, \D)[offset] === argD[0]
+
+	// Check that offset is consistent
+	filter (!ffcemux && !ffrstmux) || ffoffset == offset
+	// Check that the rest of argD is present
+	filter GetSize(port(ff, \D)) >= offset + GetSize(argD)
+	filter port(ff, \D).extract(offset, GetSize(argD)) == argD
+	// Check that FF.Q is connected to CE-mux
+	filter !ffcemux || port(ff, \Q).extract(offset, GetSize(argQ)) == argQ
+
+	set ffoffset offset
+endmatch
+
+code argQ
+	if (ff) {
+		if (clock != SigBit() && port(ff, \CLK) != clock)
+			reject;
+
+		SigSpec D = port(ff, \D);
+		SigSpec Q = port(ff, \Q);
+		if (!ffcemux) {
+			argQ = argD;
+			argQ.replace(D, Q);
+		}
+
+		for (auto c : argQ.chunks()) {
+			Const init = c.wire->attributes.at(\init, State::Sx);
+			if (!init.is_fully_undef() && !init.is_fully_zero())
+				reject;
+		}
+
+		dff = ff;
+		dffQ = argQ;
+		dffclock = port(ff, \CLK);
+	}
+	// No enable/reset mux possible without flop
+	else if (dffcemux || dffrstmux)
+		reject;
+endcode
diff --git a/passes/pmgen/xilinx_dsp_CREG.pmg b/passes/pmgen/xilinx_dsp_CREG.pmg
new file mode 100644
index 000000000..a31dc80bf
--- /dev/null
+++ b/passes/pmgen/xilinx_dsp_CREG.pmg
@@ -0,0 +1,181 @@
+pattern xilinx_dsp_packC
+
+udata <std::function<SigSpec(const SigSpec&)>> unextend
+state <SigBit> clock
+state <SigSpec> sigC sigP
+state <bool> ffCcepol ffCrstpol
+state <Cell*> ffC ffCcemux ffCrstmux
+
+// subpattern
+state <SigSpec> argQ argD
+state <bool> ffcepol ffrstpol
+state <int> ffoffset
+udata <SigSpec> dffD dffQ
+udata <SigBit> dffclock
+udata <Cell*> dff dffcemux dffrstmux
+udata <bool> dffcepol dffrstpol
+
+match dsp
+	select dsp->type.in(\DSP48E1)
+	select param(dsp, \CREG, 1).as_int() == 0
+	select nusers(port(dsp, \C, SigSpec())) > 1
+endmatch
+
+code argQ ffC ffCcemux ffCrstmux ffCcepol ffCrstpol sigC sigP clock
+	unextend = [](const SigSpec &sig) {
+		int i;
+		for (i = GetSize(sig)-1; i > 0; i--)
+			if (sig[i] != sig[i-1])
+				break;
+		// Do not remove non-const sign bit
+		if (sig[i].wire)
+			++i;
+		return sig.extract(0, i);
+	};
+	sigC = unextend(port(dsp, \C, SigSpec()));
+
+	SigSpec P = port(dsp, \P);
+	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)
+				break;
+			sigP.append(P[i]);
+		}
+		log_assert(nusers(P.extract_end(i)) <= 1);
+	}
+	else
+		sigP = P;
+
+	if (sigC == sigP)
+		reject;
+
+	clock = port(dsp, \CLK, SigBit());
+
+	argQ = sigC;
+	subpattern(in_dffe);
+	if (dff) {
+		ffC = dff;
+		clock = dffclock;
+		if (dffrstmux) {
+			ffCrstmux = dffrstmux;
+			ffCrstpol = dffrstpol;
+		}
+		if (dffcemux) {
+			ffCcemux = dffcemux;
+			ffCcepol = dffcepol;
+		}
+		sigC = dffD;
+	}
+endcode
+
+code
+	if (ffC)
+		accept;
+endcode
+
+// #######################
+
+subpattern in_dffe
+arg argD argQ clock
+
+code
+	dff = nullptr;
+	for (auto c : argQ.chunks()) {
+		if (!c.wire)
+			reject;
+		if (c.wire->get_bool_attribute(\keep))
+			reject;
+		Const init = c.wire->attributes.at(\init, State::Sx);
+		if (!init.is_fully_undef() && !init.is_fully_zero())
+			reject;
+	}
+endcode
+
+match ff
+	select ff->type.in($dff)
+	// DSP48E1 does not support clock inversion
+	select param(ff, \CLK_POLARITY).as_bool()
+
+	slice offset GetSize(port(ff, \D))
+	index <SigBit> port(ff, \Q)[offset] === argQ[0]
+
+	// Check that the rest of argQ is present
+	filter GetSize(port(ff, \Q)) >= offset + GetSize(argQ)
+	filter port(ff, \Q).extract(offset, GetSize(argQ)) == argQ
+
+	set ffoffset offset
+endmatch
+
+code argQ argD
+{
+	if (clock != SigBit() && port(ff, \CLK) != clock)
+		reject;
+
+	SigSpec Q = port(ff, \Q);
+	dff = ff;
+	dffclock = port(ff, \CLK);
+	dffD = argQ;
+	argD = port(ff, \D);
+	argQ = Q;
+	dffD.replace(argQ, argD);
+	// Only search for ffrstmux if dffD only
+	//   has two (ff, ffrstmux) users
+	if (nusers(dffD) > 2)
+		argD = SigSpec();
+}
+endcode
+
+match ffrstmux
+	if !argD.empty()
+	select ffrstmux->type.in($mux)
+	index <SigSpec> port(ffrstmux, \Y) === argD
+
+	choice <IdString> BA {\B, \A}
+	// DSP48E1 only supports reset to zero
+	select port(ffrstmux, BA).is_fully_zero()
+
+	define <bool> pol (BA == \B)
+	set ffrstpol pol
+	semioptional
+endmatch
+
+code argD
+	if (ffrstmux) {
+		dffrstmux = ffrstmux;
+		dffrstpol = ffrstpol;
+		argD = port(ffrstmux, ffrstpol ? \A : \B);
+		dffD.replace(port(ffrstmux, \Y), argD);
+
+		// Only search for ffcemux if argQ has at
+		//   least 3 users (ff, <upstream>, ffrstmux) and
+		//   dffD only has two (ff, ffrstmux)
+		if (!(nusers(argQ) >= 3 && nusers(dffD) == 2))
+			argD = SigSpec();
+	}
+	else
+		dffrstmux = nullptr;
+endcode
+
+match ffcemux
+	if !argD.empty()
+	select ffcemux->type.in($mux)
+	index <SigSpec> port(ffcemux, \Y) === argD
+	choice <IdString> AB {\A, \B}
+	index <SigSpec> port(ffcemux, AB) === argQ
+	define <bool> pol (AB == \A)
+	set ffcepol pol
+	semioptional
+endmatch
+
+code argD
+	if (ffcemux) {
+		dffcemux = ffcemux;
+		dffcepol = ffcepol;
+		argD = port(ffcemux, ffcepol ? \B : \A);
+		dffD.replace(port(ffcemux, \Y), argD);
+	}
+	else
+		dffcemux = nullptr;
+endcode
diff --git a/passes/pmgen/xilinx_dsp_cascade.pmg b/passes/pmgen/xilinx_dsp_cascade.pmg
new file mode 100644
index 000000000..6f4ac5849
--- /dev/null
+++ b/passes/pmgen/xilinx_dsp_cascade.pmg
@@ -0,0 +1,336 @@
+pattern xilinx_dsp_cascade
+
+udata <std::function<SigSpec(const SigSpec&)>> unextend
+udata <vector<std::tuple<Cell*,int,int,int>>> chain longest_chain
+state <Cell*> next
+state <SigSpec> clock
+state <int> AREG BREG
+
+// subpattern
+state <SigSpec> argQ argD
+state <bool> ffcepol ffrstpol
+state <int> ffoffset
+udata <SigSpec> dffD dffQ
+udata <SigBit> dffclock
+udata <Cell*> dff dffcemux dffrstmux
+udata <bool> dffcepol dffrstpol
+
+code
+#define MAX_DSP_CASCADE 20
+endcode
+
+match first
+	select first->type.in(\DSP48E1)
+	select port(first, \OPMODE, Const(0, 7)).extract(4,3) == Const::from_string("000")
+	select nusers(port(first, \PCOUT, SigSpec())) <= 1
+endmatch
+
+code
+	longest_chain.clear();
+	chain.emplace_back(first, -1, -1, -1);
+	subpattern(tail);
+finally
+	chain.pop_back();
+	log_assert(chain.empty());
+	if (GetSize(longest_chain) > 1) {
+		Cell *dsp = std::get<0>(longest_chain.front());
+
+		Cell *dsp_pcin;
+		int P, AREG, BREG;
+		for (int i = 1; i < GetSize(longest_chain); i++) {
+			std::tie(dsp_pcin,P,AREG,BREG) = longest_chain[i];
+
+			if (i % MAX_DSP_CASCADE > 0) {
+				if (P >= 0) {
+					Wire *cascade = module->addWire(NEW_ID, 48);
+					dsp_pcin->setPort(ID(C), Const(0, 48));
+					dsp_pcin->setPort(ID(PCIN), cascade);
+					dsp->setPort(ID(PCOUT), cascade);
+					add_siguser(cascade, dsp_pcin);
+					add_siguser(cascade, dsp);
+
+					SigSpec opmode = port(dsp_pcin, \OPMODE, Const(0, 7));
+					if (P == 17)
+						opmode[6] = State::S1;
+					else if (P == 0)
+						opmode[6] = State::S0;
+					else log_abort();
+
+					opmode[5] = State::S0;
+					opmode[4] = State::S1;
+					dsp_pcin->setPort(\OPMODE, opmode);
+
+					log_debug("PCOUT -> PCIN cascade for %s -> %s\n", log_id(dsp), log_id(dsp_pcin));
+				}
+				if (AREG >= 0) {
+					Wire *cascade = module->addWire(NEW_ID, 30);
+					dsp_pcin->setPort(ID(A), Const(0, 30));
+					dsp_pcin->setPort(ID(ACIN), cascade);
+					dsp->setPort(ID(ACOUT), cascade);
+					add_siguser(cascade, dsp_pcin);
+					add_siguser(cascade, dsp);
+
+					dsp->setParam(ID(ACASCREG), AREG);
+					dsp_pcin->setParam(ID(A_INPUT), Const("CASCADE"));
+
+					log_debug("ACOUT -> ACIN cascade for %s -> %s\n", log_id(dsp), log_id(dsp_pcin));
+				}
+				if (BREG >= 0) {
+					Wire *cascade = module->addWire(NEW_ID, 18);
+					dsp_pcin->setPort(ID(B), Const(0, 18));
+					dsp_pcin->setPort(ID(BCIN), cascade);
+					dsp->setPort(ID(BCOUT), cascade);
+					add_siguser(cascade, dsp_pcin);
+					add_siguser(cascade, dsp);
+
+					dsp->setParam(ID(BCASCREG), BREG);
+					dsp_pcin->setParam(ID(B_INPUT), Const("CASCADE"));
+
+					log_debug("BCOUT -> BCIN cascade for %s -> %s\n", log_id(dsp), log_id(dsp_pcin));
+				}
+			}
+			else {
+				log_debug("  Blocking %s -> %s cascade (exceeds max: %d)\n", log_id(dsp), log_id(dsp_pcin), MAX_DSP_CASCADE);
+			}
+
+			dsp = dsp_pcin;
+		}
+
+		accept;
+	}
+endcode
+
+// ------------------------------------------------------------------
+
+subpattern tail
+arg first
+arg next
+
+match nextP
+	select nextP->type.in(\DSP48E1)
+	select !param(nextP, \CREG, State::S1).as_bool()
+	select port(nextP, \OPMODE, Const(0, 7)).extract(4,3) == Const::from_string("011")
+	select nusers(port(nextP, \C, SigSpec())) > 1
+	select nusers(port(nextP, \PCIN, SigSpec())) == 0
+	index <SigBit> port(nextP, \C)[0] === port(std::get<0>(chain.back()), \P)[0]
+	semioptional
+endmatch
+
+match nextP_shift17
+	if !nextP
+	select nextP_shift17->type.in(\DSP48E1)
+	select !param(nextP_shift17, \CREG, State::S1).as_bool()
+	select port(nextP_shift17, \OPMODE, Const(0, 7)).extract(4,3) == Const::from_string("011")
+	select nusers(port(nextP_shift17, \C, SigSpec())) > 1
+	select nusers(port(nextP_shift17, \PCIN, SigSpec())) == 0
+	index <SigBit> port(nextP_shift17, \C)[0] === port(std::get<0>(chain.back()), \P)[17]
+	semioptional
+endmatch
+
+code next
+	next = nextP;
+	if (!nextP)
+		next = nextP_shift17;
+	if (next) {
+		unextend = [](const SigSpec &sig) {
+			int i;
+			for (i = GetSize(sig)-1; i > 0; i--)
+				if (sig[i] != sig[i-1])
+					break;
+			// Do not remove non-const sign bit
+			if (sig[i].wire)
+				++i;
+			return sig.extract(0, i);
+		};
+	}
+endcode
+
+code argQ clock AREG
+	AREG = -1;
+	if (next) {
+		Cell *prev = std::get<0>(chain.back());
+		if (param(prev, \AREG, 2).as_int() > 0 &&
+				param(next, \AREG, 2).as_int() > 0 &&
+				param(next, \A_INPUT, Const("DIRECT")).decode_string() == "DIRECT" &&
+				port(next, \ACIN, SigSpec()).is_fully_zero() &&
+				nusers(port(prev, \ACOUT, SigSpec())) <= 1) {
+			argQ = unextend(port(next, \A));
+			clock = port(prev, \CLK);
+			subpattern(in_dffe);
+			if (dff) {
+				if (!dffrstmux && port(prev, \RSTA, State::S0) != State::S0)
+					goto reject_AREG;
+				if (dffrstmux && port(dffrstmux, \S) != port(prev, \RSTA, State::S0))
+					goto reject_AREG;
+				if (!dffcemux && port(prev, \CEA2, State::S0) != State::S0)
+					goto reject_AREG;
+				if (dffcemux && port(dffcemux, \S) != port(prev, \CEA2, State::S0))
+					goto reject_AREG;
+				if (dffD == unextend(port(prev, \A)))
+					AREG = 1;
+reject_AREG:			;
+			}
+		}
+	}
+endcode
+
+code argQ clock BREG
+	BREG = -1;
+	if (next) {
+		Cell *prev = std::get<0>(chain.back());
+		if (param(prev, \BREG, 2).as_int() > 0 &&
+				param(next, \BREG, 2).as_int() > 0 &&
+				param(next, \B_INPUT, Const("DIRECT")).decode_string() == "DIRECT" &&
+				port(next, \BCIN, SigSpec()).is_fully_zero() &&
+				nusers(port(prev, \BCOUT, SigSpec())) <= 1) {
+			argQ = unextend(port(next, \B));
+			clock = port(prev, \CLK);
+			subpattern(in_dffe);
+			if (dff) {
+				if (!dffrstmux && port(prev, \RSTB, State::S0) != State::S0)
+					goto reject_BREG;
+				if (dffrstmux && port(dffrstmux, \S) != port(prev, \RSTB, State::S0))
+					goto reject_BREG;
+				if (!dffcemux && port(prev, \CEB2, State::S0) != State::S0)
+					goto reject_BREG;
+				if (dffcemux && port(dffcemux, \S) != port(prev, \CEB2, State::S0))
+					goto reject_BREG;
+				if (dffD == unextend(port(prev, \B)))
+					BREG = 1;
+reject_BREG:			;
+			}
+		}
+	}
+endcode
+
+code
+	if (next) {
+		chain.emplace_back(next, nextP_shift17 ? 17 : nextP ? 0 : -1, AREG, BREG);
+
+		SigSpec sigC = unextend(port(next, \C));
+
+		// TODO: Cannot use 'reject' since semioptional
+		if (nextP_shift17) {
+			if (GetSize(sigC)+17 <= GetSize(port(std::get<0>(chain.back()), \P)) &&
+					port(std::get<0>(chain.back()), \P).extract(17, GetSize(sigC)) != sigC)
+				subpattern(tail);
+		}
+		else {
+			if (GetSize(sigC) <= GetSize(port(std::get<0>(chain.back()), \P)) &&
+					port(std::get<0>(chain.back()), \P).extract(0, GetSize(sigC)) != sigC)
+				subpattern(tail);
+
+		}
+	} else {
+		if (GetSize(chain) > GetSize(longest_chain))
+			longest_chain = chain;
+	}
+finally
+	if (next)
+		chain.pop_back();
+endcode
+
+// #######################
+
+subpattern in_dffe
+arg argD argQ clock
+
+code
+	dff = nullptr;
+	for (auto c : argQ.chunks()) {
+		if (!c.wire)
+			reject;
+		if (c.wire->get_bool_attribute(\keep))
+			reject;
+		Const init = c.wire->attributes.at(\init, State::Sx);
+		if (!init.is_fully_undef() && !init.is_fully_zero())
+			reject;
+	}
+endcode
+
+match ff
+	select ff->type.in($dff)
+	// DSP48E1 does not support clock inversion
+	select param(ff, \CLK_POLARITY).as_bool()
+
+	slice offset GetSize(port(ff, \D))
+	index <SigBit> port(ff, \Q)[offset] === argQ[0]
+
+	// Check that the rest of argQ is present
+	filter GetSize(port(ff, \Q)) >= offset + GetSize(argQ)
+	filter port(ff, \Q).extract(offset, GetSize(argQ)) == argQ
+
+	set ffoffset offset
+endmatch
+
+code argQ argD
+{
+	if (clock != SigBit() && port(ff, \CLK) != clock)
+		reject;
+
+	SigSpec Q = port(ff, \Q);
+	dff = ff;
+	dffclock = port(ff, \CLK);
+	dffD = argQ;
+	argD = port(ff, \D);
+	argQ = Q;
+	dffD.replace(argQ, argD);
+	// Only search for ffrstmux if dffD only
+	//   has two (ff, ffrstmux) users
+	if (nusers(dffD) > 2)
+		argD = SigSpec();
+}
+endcode
+
+match ffrstmux
+	if !argD.empty()
+	select ffrstmux->type.in($mux)
+	index <SigSpec> port(ffrstmux, \Y) === argD
+
+	choice <IdString> BA {\B, \A}
+	// DSP48E1 only supports reset to zero
+	select port(ffrstmux, BA).is_fully_zero()
+
+	define <bool> pol (BA == \B)
+	set ffrstpol pol
+	semioptional
+endmatch
+
+code argD
+	if (ffrstmux) {
+		dffrstmux = ffrstmux;
+		dffrstpol = ffrstpol;
+		argD = port(ffrstmux, ffrstpol ? \A : \B);
+		dffD.replace(port(ffrstmux, \Y), argD);
+
+		// Only search for ffcemux if argQ has at
+		//   least 3 users (ff, <upstream>, ffrstmux) and
+		//   dffD only has two (ff, ffrstmux)
+		if (!(nusers(argQ) >= 3 && nusers(dffD) == 2))
+			argD = SigSpec();
+	}
+	else
+		dffrstmux = nullptr;
+endcode
+
+match ffcemux
+	if !argD.empty()
+	select ffcemux->type.in($mux)
+	index <SigSpec> port(ffcemux, \Y) === argD
+	choice <IdString> AB {\A, \B}
+	index <SigSpec> port(ffcemux, AB) === argQ
+	define <bool> pol (AB == \A)
+	set ffcepol pol
+	semioptional
+endmatch
+
+code argD
+	if (ffcemux) {
+		dffcemux = ffcemux;
+		dffcepol = ffcepol;
+		argD = port(ffcemux, ffcepol ? \B : \A);
+		dffD.replace(port(ffcemux, \Y), argD);
+	}
+	else
+		dffcemux = nullptr;
+endcode
diff --git a/passes/pmgen/xilinx_srl.pmg b/passes/pmgen/xilinx_srl.pmg
index b18119b87..535b3dfdc 100644
--- a/passes/pmgen/xilinx_srl.pmg
+++ b/passes/pmgen/xilinx_srl.pmg
@@ -13,9 +13,9 @@ endcode
 match first
 	select first->type.in($_DFF_N_, $_DFF_P_, $_DFFE_NN_, $_DFFE_NP_, $_DFFE_PN_, $_DFFE_PP_, \FDRE, \FDRE_1)
 	select !first->has_keep_attr()
-	select !first->type.in(\FDRE) || !first->parameters.at(\IS_R_INVERTED, State::S0).as_bool()
-	select !first->type.in(\FDRE) || !first->parameters.at(\IS_D_INVERTED, State::S0).as_bool()
-	select !first->type.in(\FDRE, \FDRE_1) || first->connections_.at(\R, State::S0).is_fully_zero()
+	select !first->type.in(\FDRE) || !param(first, \IS_R_INVERTED, State::S0).as_bool()
+	select !first->type.in(\FDRE) || !param(first, \IS_D_INVERTED, State::S0).as_bool()
+	select !first->type.in(\FDRE, \FDRE_1) || port(first, \R, State::S0).is_fully_zero()
 	filter !non_first_cells.count(first)
 generate
 	SigSpec C = module->addWire(NEW_ID);
@@ -84,9 +84,9 @@ arg en_port
 match first
 	select first->type.in($_DFF_N_, $_DFF_P_, $_DFFE_NN_, $_DFFE_NP_, $_DFFE_PN_, $_DFFE_PP_, \FDRE, \FDRE_1)
 	select !first->has_keep_attr()
-	select !first->type.in(\FDRE) || !first->parameters.at(\IS_R_INVERTED, State::S0).as_bool()
-	select !first->type.in(\FDRE) || !first->parameters.at(\IS_D_INVERTED, State::S0).as_bool()
-	select !first->type.in(\FDRE, \FDRE_1) || first->connections_.at(\R, State::S0).is_fully_zero()
+	select !first->type.in(\FDRE) || !param(first, \IS_R_INVERTED, State::S0).as_bool()
+	select !first->type.in(\FDRE) || !param(first, \IS_D_INVERTED, State::S0).as_bool()
+	select !first->type.in(\FDRE, \FDRE_1) || port(first, \R, State::S0).is_fully_zero()
 endmatch
 
 code clk_port en_port
@@ -111,10 +111,10 @@ match next
 	index <SigBit> port(next, \Q) === port(first, \D)
 	filter port(next, clk_port) == port(first, clk_port)
 	filter en_port == IdString() || port(next, en_port) == port(first, en_port)
-	filter !first->type.in(\FDRE) || next->parameters.at(\IS_C_INVERTED, State::S0).as_bool() == first->parameters.at(\IS_C_INVERTED, State::S0).as_bool()
-	filter !first->type.in(\FDRE) || next->parameters.at(\IS_D_INVERTED, State::S0).as_bool() == first->parameters.at(\IS_D_INVERTED, State::S0).as_bool()
-	filter !first->type.in(\FDRE) || next->parameters.at(\IS_R_INVERTED, State::S0).as_bool() == first->parameters.at(\IS_R_INVERTED, State::S0).as_bool()
-	filter !first->type.in(\FDRE, \FDRE_1) || next->connections_.at(\R, State::S0).is_fully_zero()
+	filter !first->type.in(\FDRE) || param(next, \IS_C_INVERTED, State::S0).as_bool() == param(first, \IS_C_INVERTED, State::S0).as_bool()
+	filter !first->type.in(\FDRE) || param(next, \IS_D_INVERTED, State::S0).as_bool() == param(first, \IS_D_INVERTED, State::S0).as_bool()
+	filter !first->type.in(\FDRE) || param(next, \IS_R_INVERTED, State::S0).as_bool() == param(first, \IS_R_INVERTED, State::S0).as_bool()
+	filter !first->type.in(\FDRE, \FDRE_1) || port(next, \R, State::S0).is_fully_zero()
 endmatch
 
 code
@@ -138,10 +138,10 @@ match next
 	index <SigBit> port(next, \Q) === port(chain.back(), \D)
 	filter port(next, clk_port) == port(first, clk_port)
 	filter en_port == IdString() || port(next, en_port) == port(first, en_port)
-	filter !first->type.in(\FDRE) || next->parameters.at(\IS_C_INVERTED, State::S0).as_bool() == first->parameters.at(\IS_C_INVERTED, State::S0).as_bool()
-	filter !first->type.in(\FDRE) || next->parameters.at(\IS_D_INVERTED, State::S0).as_bool() == first->parameters.at(\IS_D_INVERTED, State::S0).as_bool()
-	filter !first->type.in(\FDRE) || next->parameters.at(\IS_R_INVERTED, State::S0).as_bool() == first->parameters.at(\IS_R_INVERTED, State::S0).as_bool()
-	filter !first->type.in(\FDRE, \FDRE_1) || next->connections_.at(\R, State::S0).is_fully_zero()
+	filter !first->type.in(\FDRE) || param(next, \IS_C_INVERTED, State::S0).as_bool() == param(first, \IS_C_INVERTED, State::S0).as_bool()
+	filter !first->type.in(\FDRE) || param(next, \IS_D_INVERTED, State::S0).as_bool() == param(first, \IS_D_INVERTED, State::S0).as_bool()
+	filter !first->type.in(\FDRE) || param(next, \IS_R_INVERTED, State::S0).as_bool() == param(first, \IS_R_INVERTED, State::S0).as_bool()
+	filter !first->type.in(\FDRE, \FDRE_1) || port(next, \R, State::S0).is_fully_zero()
 generate
 	Cell *cell = module->addCell(NEW_ID, chain.back()->type);
 	cell->setPort(\C, chain.back()->getPort(\C));
@@ -149,7 +149,7 @@ generate
 	cell->setPort(\Q, chain.back()->getPort(\D));
 	if (cell->type == \FDRE) {
 		if (rng(2) == 0)
-			cell->setPort(\R, chain.back()->connections_.at(\R, State::S0));
+			cell->setPort(\R, port(chain.back(), \R, State::S0));
 		cell->setPort(\CE, chain.back()->getPort(\CE));
 	}
 	else if (cell->type.begins_with("$_DFFE_"))
diff --git a/passes/techmap/abc9.cc b/passes/techmap/abc9.cc
index 7eac08d17..aa473e67d 100644
--- a/passes/techmap/abc9.cc
+++ b/passes/techmap/abc9.cc
@@ -606,7 +606,6 @@ void abc9_module(RTLIL::Design *design, RTLIL::Module *current_module, std::stri
 				existing_cell = module->cell(c->name);
 				log_assert(existing_cell);
 				cell = module->addCell(remap_name(c->name), c->type);
-				module->swap_names(cell, existing_cell);
 			}
 
 			if (markgroups) cell->attributes[ID(abcgroup)] = map_autoidx;
@@ -642,8 +641,22 @@ void abc9_module(RTLIL::Design *design, RTLIL::Module *current_module, std::stri
 			}
 		}
 
-		for (auto cell : boxes)
-			module->remove(cell);
+		for (auto existing_cell : boxes) {
+			Cell *cell = module->cell(remap_name(existing_cell->name));
+			if (cell) {
+				for (auto &conn : existing_cell->connections()) {
+					if (!conn.second.is_wire())
+						continue;
+					Wire *wire = conn.second.as_wire();
+					if (!wire->get_bool_attribute(ID(abc_padding)))
+						continue;
+					cell->unsetPort(conn.first);
+					log_debug("Dropping padded port connection for %s (%s) .%s (%s )\n", log_id(cell), cell->type.c_str(), log_id(conn.first), log_signal(conn.second));
+				}
+				module->swap_names(cell, existing_cell);
+			}
+			module->remove(existing_cell);
+		}
 
 		// Copy connections (and rename) from mapped_mod to module
 		for (auto conn : mapped_mod->connections()) {
diff --git a/passes/tests/test_autotb.cc b/passes/tests/test_autotb.cc
index a5ac3130f..2b6a86c25 100644
--- a/passes/tests/test_autotb.cc
+++ b/passes/tests/test_autotb.cc
@@ -351,6 +351,11 @@ struct TestAutotbBackend : public Backend {
 		log("    -n <int>\n");
 		log("        number of iterations the test bench should run (default = 1000)\n");
 		log("\n");
+		log("    -seed <int>\n");
+		log("        seed used for pseudo-random number generation (default = 0).\n");
+		log("        a value of 0 will cause an arbitrary seed to be chosen, based on\n");
+		log("        the current system time.\n");
+		log("\n");
 	}
 	void execute(std::ostream *&f, std::string filename, std::vector<std::string> args, RTLIL::Design *design) YS_OVERRIDE
 	{