diff --git a/passes/techmap/Makefile.inc b/passes/techmap/Makefile.inc
index 7c1ec884c..4f72ea6bc 100644
--- a/passes/techmap/Makefile.inc
+++ b/passes/techmap/Makefile.inc
@@ -12,6 +12,7 @@ OBJS += passes/techmap/extract.o
 OBJS += passes/techmap/alumacc.o
 OBJS += passes/techmap/dff2dffe.o
 OBJS += passes/techmap/dffinit.o
+OBJS += passes/techmap/muxcover.o
 endif
 
 GENFILES += passes/techmap/techmap.inc
diff --git a/passes/techmap/muxcover.cc b/passes/techmap/muxcover.cc
new file mode 100644
index 000000000..b3bd09f73
--- /dev/null
+++ b/passes/techmap/muxcover.cc
@@ -0,0 +1,541 @@
+/*
+ *  yosys -- Yosys Open SYnthesis Suite
+ *
+ *  Copyright (C) 2012  Clifford Wolf <clifford@clifford.at>
+ *  
+ *  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
+
+struct MuxcoverWorker
+{
+	Module *module;
+	SigMap sigmap;
+
+	struct newmux_t
+	{
+		int cost;
+		vector<SigBit> inputs, selects;
+		newmux_t() : cost(0) {}
+	};
+
+	struct tree_t
+	{
+		SigBit root;
+		dict<SigBit, Cell*> muxes;
+		dict<SigBit, newmux_t> newmuxes;
+	};
+
+	vector<tree_t> tree_list;
+
+	bool use_mux4;
+	bool use_mux8;
+	bool use_mux16;
+	bool nodecode;
+
+	MuxcoverWorker(Module *module) : module(module), sigmap(module)
+	{
+		use_mux4 = false;
+		use_mux8 = false;
+		use_mux16 = false;
+		nodecode = false;
+	}
+
+	void treeify()
+	{
+		pool<SigBit> roots;
+		pool<SigBit> used_once;
+		dict<SigBit, Cell*> sig_to_mux;
+
+		for (auto wire : module->wires()) {
+			if (!wire->port_output)
+				continue;
+			for (auto bit : sigmap(wire))
+				roots.insert(bit);
+		}
+
+		for (auto cell : module->cells()) {
+			for (auto conn : cell->connections()) {
+				if (!cell->input(conn.first))
+					continue;
+				for (auto bit : sigmap(conn.second)) {
+					if (used_once.count(bit) || cell->type != "$_MUX_" || conn.first == "\\S")
+						roots.insert(bit);
+					used_once.insert(bit);
+				}
+			}
+			if (cell->type == "$_MUX_")
+				sig_to_mux[sigmap(cell->getPort("\\Y"))] = cell;
+		}
+
+		roots.sort();
+		for (auto rootsig : roots)
+		{
+			tree_t tree;
+			tree.root = rootsig;
+
+			pool<SigBit> wavefront;
+			wavefront.insert(rootsig);
+
+			while (!wavefront.empty()) {
+				SigBit bit = wavefront.pop();
+				if (sig_to_mux.count(bit) && (bit == rootsig || !roots.count(bit))) {
+					Cell *c = sig_to_mux.at(bit);
+					tree.muxes[bit] = c;
+					wavefront.insert(sigmap(c->getPort("\\A")));
+					wavefront.insert(sigmap(c->getPort("\\B")));
+				}
+			}
+
+			if (!tree.muxes.empty()) {
+				log("Found tree with %d MUXes at root %s.\n", GetSize(tree.muxes), log_signal(tree.root));
+				tree_list.push_back(tree);
+			}
+		}
+
+		log("Finished treeification: Found %d trees.\n", GetSize(tree_list));
+	}
+
+	bool follow_muxtree(SigBit &ret_bit, tree_t &tree, SigBit bit, const char *path)
+	{
+		if (*path) {
+			if (tree.muxes.count(bit) == 0)
+				return false;
+			char port_name[3] = {'\\', *path, 0};
+			return follow_muxtree(ret_bit, tree, sigmap(tree.muxes.at(bit)->getPort(port_name)), path+1);
+		} else {
+			ret_bit = bit;
+			return true;
+		}
+	}
+
+	int find_best_cover(tree_t &tree, SigBit bit)
+	{
+		if (tree.newmuxes.count(bit)) {
+			return tree.newmuxes.at(bit).cost;
+		}
+
+		SigBit A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P;
+		SigBit S1, S2, S3, S4, S5, S6, S7, S8;
+		SigBit T1, T2, T3, T4;
+		SigBit U1, U2;
+		SigBit V1;
+
+		newmux_t best_mux;
+		bool ok = true;
+
+		// 2-Input MUX
+
+		ok = ok && follow_muxtree(A, tree, bit, "A");
+		ok = ok && follow_muxtree(B, tree, bit, "B");
+
+		ok = ok && follow_muxtree(S1, tree, bit, "S");
+
+		if (ok)
+		{
+			newmux_t mux;
+
+			mux.inputs.push_back(A);
+			mux.inputs.push_back(B);
+			mux.selects.push_back(S1);
+
+			mux.cost += 10;
+			mux.cost += find_best_cover(tree, A);
+			mux.cost += find_best_cover(tree, B);
+
+			best_mux = mux;
+		}
+
+		// 4-Input MUX
+
+		if (use_mux4)
+		{
+			ok = ok && follow_muxtree(A, tree, bit, "AA");
+			ok = ok && follow_muxtree(B, tree, bit, "AB");
+			ok = ok && follow_muxtree(C, tree, bit, "BA");
+			ok = ok && follow_muxtree(D, tree, bit, "BB");
+
+			ok = ok && follow_muxtree(S1, tree, bit, "AS");
+			ok = ok && follow_muxtree(S2, tree, bit, "BS");
+
+			if (nodecode)
+				ok = ok && S1 == S2;
+
+			ok = ok && follow_muxtree(T1, tree, bit, "S");
+
+			if (ok)
+			{
+				newmux_t mux;
+
+				mux.inputs.push_back(A);
+				mux.inputs.push_back(B);
+				mux.inputs.push_back(C);
+				mux.inputs.push_back(D);
+
+				mux.selects.push_back(S1);
+				mux.selects.push_back(T1);
+
+				mux.cost += 10;
+				mux.cost += find_best_cover(tree, A);
+				mux.cost += find_best_cover(tree, B);
+				mux.cost += find_best_cover(tree, C);
+				mux.cost += find_best_cover(tree, D);
+
+				if (best_mux.cost > mux.cost)
+					best_mux = mux;
+			}
+		}
+
+		// 8-Input MUX
+
+		if (use_mux8)
+		{
+			ok = ok && follow_muxtree(A, tree, bit, "AAA");
+			ok = ok && follow_muxtree(B, tree, bit, "AAB");
+			ok = ok && follow_muxtree(C, tree, bit, "ABA");
+			ok = ok && follow_muxtree(D, tree, bit, "ABB");
+			ok = ok && follow_muxtree(E, tree, bit, "BAA");
+			ok = ok && follow_muxtree(F, tree, bit, "BAB");
+			ok = ok && follow_muxtree(G, tree, bit, "BBA");
+			ok = ok && follow_muxtree(H, tree, bit, "BBB");
+
+			ok = ok && follow_muxtree(S1, tree, bit, "AAS");
+			ok = ok && follow_muxtree(S2, tree, bit, "ABS");
+			ok = ok && follow_muxtree(S3, tree, bit, "BAS");
+			ok = ok && follow_muxtree(S4, tree, bit, "BBS");
+
+			if (nodecode)
+				ok = ok && S1 == S2 && S2 == S3 && S3 == S4;
+
+			ok = ok && follow_muxtree(T1, tree, bit, "AS");
+			ok = ok && follow_muxtree(T2, tree, bit, "BS");
+
+			if (nodecode)
+				ok = ok && T1 == T2;
+
+			ok = ok && follow_muxtree(U1, tree, bit, "S");
+
+			if (ok)
+			{
+				newmux_t mux;
+
+				mux.inputs.push_back(A);
+				mux.inputs.push_back(B);
+				mux.inputs.push_back(C);
+				mux.inputs.push_back(D);
+				mux.inputs.push_back(E);
+				mux.inputs.push_back(F);
+				mux.inputs.push_back(G);
+				mux.inputs.push_back(H);
+
+				mux.selects.push_back(S1);
+				mux.selects.push_back(T1);
+				mux.selects.push_back(U1);
+
+				mux.cost += 10;
+				mux.cost += find_best_cover(tree, A);
+				mux.cost += find_best_cover(tree, B);
+				mux.cost += find_best_cover(tree, C);
+				mux.cost += find_best_cover(tree, D);
+				mux.cost += find_best_cover(tree, E);
+				mux.cost += find_best_cover(tree, F);
+				mux.cost += find_best_cover(tree, G);
+				mux.cost += find_best_cover(tree, H);
+
+				if (best_mux.cost > mux.cost)
+					best_mux = mux;
+			}
+		}
+
+		// 16-Input MUX
+
+		if (use_mux16)
+		{
+			ok = ok && follow_muxtree(A, tree, bit, "AAAA");
+			ok = ok && follow_muxtree(B, tree, bit, "AAAB");
+			ok = ok && follow_muxtree(C, tree, bit, "AABA");
+			ok = ok && follow_muxtree(D, tree, bit, "AABB");
+			ok = ok && follow_muxtree(E, tree, bit, "ABAA");
+			ok = ok && follow_muxtree(F, tree, bit, "ABAB");
+			ok = ok && follow_muxtree(G, tree, bit, "ABBA");
+			ok = ok && follow_muxtree(H, tree, bit, "ABBB");
+			ok = ok && follow_muxtree(I, tree, bit, "BAAA");
+			ok = ok && follow_muxtree(J, tree, bit, "BAAB");
+			ok = ok && follow_muxtree(K, tree, bit, "BABA");
+			ok = ok && follow_muxtree(L, tree, bit, "BABB");
+			ok = ok && follow_muxtree(M, tree, bit, "BBAA");
+			ok = ok && follow_muxtree(N, tree, bit, "BBAB");
+			ok = ok && follow_muxtree(O, tree, bit, "BBBA");
+			ok = ok && follow_muxtree(P, tree, bit, "BBBB");
+
+			ok = ok && follow_muxtree(S1, tree, bit, "AAAS");
+			ok = ok && follow_muxtree(S2, tree, bit, "AABS");
+			ok = ok && follow_muxtree(S3, tree, bit, "ABAS");
+			ok = ok && follow_muxtree(S4, tree, bit, "ABBS");
+			ok = ok && follow_muxtree(S5, tree, bit, "BAAS");
+			ok = ok && follow_muxtree(S6, tree, bit, "BABS");
+			ok = ok && follow_muxtree(S7, tree, bit, "BBAS");
+			ok = ok && follow_muxtree(S8, tree, bit, "BBBS");
+
+			if (nodecode)
+				ok = ok && S1 == S2 && S2 == S3 && S3 == S4 && S4 == S5 && S5 == S6 && S6 == S7 && S7 == S8;
+
+			ok = ok && follow_muxtree(T1, tree, bit, "AAS");
+			ok = ok && follow_muxtree(T2, tree, bit, "ABS");
+			ok = ok && follow_muxtree(T3, tree, bit, "BAS");
+			ok = ok && follow_muxtree(T4, tree, bit, "BBS");
+
+			if (nodecode)
+				ok = ok && T1 == T2 && T2 == T3 && T3 == T4;
+
+			ok = ok && follow_muxtree(U1, tree, bit, "AS");
+			ok = ok && follow_muxtree(U2, tree, bit, "BS");
+
+			if (nodecode)
+				ok = ok && U1 == U2;
+
+			ok = ok && follow_muxtree(V1, tree, bit, "S");
+
+			if (ok)
+			{
+				newmux_t mux;
+
+				mux.inputs.push_back(A);
+				mux.inputs.push_back(B);
+				mux.inputs.push_back(C);
+				mux.inputs.push_back(D);
+				mux.inputs.push_back(E);
+				mux.inputs.push_back(F);
+				mux.inputs.push_back(G);
+				mux.inputs.push_back(H);
+				mux.inputs.push_back(I);
+				mux.inputs.push_back(J);
+				mux.inputs.push_back(K);
+				mux.inputs.push_back(L);
+				mux.inputs.push_back(M);
+				mux.inputs.push_back(N);
+				mux.inputs.push_back(O);
+				mux.inputs.push_back(P);
+
+				mux.selects.push_back(S1);
+				mux.selects.push_back(T1);
+				mux.selects.push_back(U1);
+				mux.selects.push_back(V1);
+
+				mux.cost += 10;
+				mux.cost += find_best_cover(tree, A);
+				mux.cost += find_best_cover(tree, B);
+				mux.cost += find_best_cover(tree, C);
+				mux.cost += find_best_cover(tree, D);
+				mux.cost += find_best_cover(tree, E);
+				mux.cost += find_best_cover(tree, F);
+				mux.cost += find_best_cover(tree, G);
+				mux.cost += find_best_cover(tree, H);
+				mux.cost += find_best_cover(tree, I);
+				mux.cost += find_best_cover(tree, J);
+				mux.cost += find_best_cover(tree, K);
+				mux.cost += find_best_cover(tree, L);
+				mux.cost += find_best_cover(tree, M);
+				mux.cost += find_best_cover(tree, N);
+				mux.cost += find_best_cover(tree, O);
+				mux.cost += find_best_cover(tree, P);
+
+				if (best_mux.cost > mux.cost)
+					best_mux = mux;
+			}
+		}
+
+		tree.newmuxes[bit] = best_mux;
+		return best_mux.cost;
+	}
+
+	void implement_best_cover(tree_t &tree, SigBit bit, int count_muxes_by_type[4])
+	{
+		newmux_t mux = tree.newmuxes.at(bit);
+
+		for (auto inbit : mux.inputs)
+			implement_best_cover(tree, inbit, count_muxes_by_type);
+
+		if (GetSize(mux.inputs) == 0)
+			return;
+
+		if (GetSize(mux.inputs) == 2) {
+			count_muxes_by_type[0]++;
+			Cell *cell = module->addCell(NEW_ID, "$_MUX_");
+			cell->setPort("\\A", mux.inputs[0]);
+			cell->setPort("\\B", mux.inputs[1]);
+			cell->setPort("\\S", mux.selects[0]);
+			cell->setPort("\\Y", bit);
+			return;
+		}
+
+		if (GetSize(mux.inputs) == 4) {
+			count_muxes_by_type[1]++;
+			Cell *cell = module->addCell(NEW_ID, "$_MUX4_");
+			cell->setPort("\\A", mux.inputs[0]);
+			cell->setPort("\\B", mux.inputs[1]);
+			cell->setPort("\\C", mux.inputs[2]);
+			cell->setPort("\\D", mux.inputs[3]);
+			cell->setPort("\\S", mux.selects[0]);
+			cell->setPort("\\T", mux.selects[1]);
+			cell->setPort("\\Y", bit);
+			return;
+		}
+
+		if (GetSize(mux.inputs) == 8) {
+			count_muxes_by_type[2]++;
+			Cell *cell = module->addCell(NEW_ID, "$_MUX8_");
+			cell->setPort("\\A", mux.inputs[0]);
+			cell->setPort("\\B", mux.inputs[1]);
+			cell->setPort("\\C", mux.inputs[2]);
+			cell->setPort("\\D", mux.inputs[3]);
+			cell->setPort("\\E", mux.inputs[4]);
+			cell->setPort("\\F", mux.inputs[5]);
+			cell->setPort("\\G", mux.inputs[6]);
+			cell->setPort("\\H", mux.inputs[7]);
+			cell->setPort("\\S", mux.selects[0]);
+			cell->setPort("\\T", mux.selects[1]);
+			cell->setPort("\\U", mux.selects[2]);
+			cell->setPort("\\Y", bit);
+			return;
+		}
+
+		if (GetSize(mux.inputs) == 16) {
+			count_muxes_by_type[3]++;
+			Cell *cell = module->addCell(NEW_ID, "$_MUX16_");
+			cell->setPort("\\A", mux.inputs[0]);
+			cell->setPort("\\B", mux.inputs[1]);
+			cell->setPort("\\C", mux.inputs[2]);
+			cell->setPort("\\D", mux.inputs[3]);
+			cell->setPort("\\E", mux.inputs[4]);
+			cell->setPort("\\F", mux.inputs[5]);
+			cell->setPort("\\G", mux.inputs[6]);
+			cell->setPort("\\H", mux.inputs[7]);
+			cell->setPort("\\I", mux.inputs[8]);
+			cell->setPort("\\J", mux.inputs[9]);
+			cell->setPort("\\K", mux.inputs[10]);
+			cell->setPort("\\L", mux.inputs[11]);
+			cell->setPort("\\M", mux.inputs[12]);
+			cell->setPort("\\N", mux.inputs[13]);
+			cell->setPort("\\O", mux.inputs[14]);
+			cell->setPort("\\P", mux.inputs[15]);
+			cell->setPort("\\S", mux.selects[0]);
+			cell->setPort("\\T", mux.selects[1]);
+			cell->setPort("\\U", mux.selects[2]);
+			cell->setPort("\\V", mux.selects[3]);
+			cell->setPort("\\Y", bit);
+			return;
+		}
+
+		log_abort();
+	}
+
+	void treecover(tree_t &tree)
+	{
+		int count_muxes_by_type[4] = {0, 0, 0, 0};
+		find_best_cover(tree, tree.root);
+		implement_best_cover(tree, tree.root, count_muxes_by_type);
+		log("Replaced tree at %s: %d MUX2, %d MUX4, %d MUX8, %d MUX16\n", log_signal(tree.root), 
+				count_muxes_by_type[0], count_muxes_by_type[1], count_muxes_by_type[2], count_muxes_by_type[3]);
+		for (auto &it : tree.muxes)
+			module->remove(it.second);
+	}
+
+	void run()
+	{
+		log("Covering MUX trees in module %s..\n", log_id(module));
+
+		treeify();
+
+		for (auto &tree : tree_list)
+			treecover(tree);
+	}
+};
+
+struct MuxcoverPass : public Pass {
+	MuxcoverPass() : Pass("muxcover", "cover trees of MUX cells with wider MUXes") { }
+	virtual void help()
+	{
+		//   |---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|
+		log("\n");
+		log("    muxcover [options] [selection]\n");
+		log("\n");
+		log("Cover trees of $_MUX_ cells with $_MUX{4,8,16}_ cells\n");
+		log("\n");
+		log("    -mux4, -mux8, -mux16\n");
+		log("        Use the specified types of MUXes. If none of those options are used,\n");
+		log("        the effect is the same as if all of them where used.\n");
+		log("\n");
+		// log("    -nodecode\n");
+		// log("        Do not insert decoder logic. This reduces the number of possible\n");
+		// log("        substitutions, but guarantees that the resulting circuit is not\n");
+		// log("        less efficient than the original circuit.\n");
+		// log("\n");
+	}
+	virtual void execute(std::vector<std::string> args, RTLIL::Design *design)
+	{
+		log_header("Executing MUXCOVER pass (mapping to wider MUXes).\n");
+
+		bool use_mux4 = false;
+		bool use_mux8 = false;
+		bool use_mux16 = false;
+		bool nodecode = true;
+
+		size_t argidx;
+		for (argidx = 1; argidx < args.size(); argidx++)
+		{
+			if (args[argidx] == "-mux4") {
+				use_mux4 = true;
+				continue;
+			}
+			if (args[argidx] == "-mux8") {
+				use_mux8 = true;
+				continue;
+			}
+			if (args[argidx] == "-mux16") {
+				use_mux16 = true;
+				continue;
+			}
+			if (args[argidx] == "-nodecode") {
+				nodecode = true;
+				continue;
+			}
+			break;
+		}
+		extra_args(args, argidx, design);
+
+		if (!use_mux4 && !use_mux8 && !use_mux16) {
+			use_mux4 = true;
+			use_mux8 = true;
+			use_mux16 = true;
+		}
+
+		for (auto module : design->selected_modules())
+		{
+			MuxcoverWorker worker(module);
+			worker.use_mux4 = use_mux4;
+			worker.use_mux8 = use_mux8;
+			worker.use_mux16 = use_mux16;
+			worker.nodecode = nodecode;
+			worker.run();
+		}
+	}
+} MuxcoverPass;
+ 
+PRIVATE_NAMESPACE_END