1 files changed, 131 insertions, 5 deletions

diff --git a/passes/techmap/shregmap.cc b/passes/techmap/shregmap.cc
index f20863ba0..d5221d46f 100644
--- a/passes/techmap/shregmap.cc
+++ b/passes/techmap/shregmap.cc
@@ -26,7 +26,9 @@ PRIVATE_NAMESPACE_BEGIN
 struct ShregmapTech
 {
 	virtual ~ShregmapTech() { }
-	virtual bool analyze(vector<int> &taps) = 0;
+	virtual void init(const Module * /*module*/, const SigMap &/*sigmap*/) {}
+	virtual void non_chain_user(const SigBit &/*bit*/, const Cell* /*cell*/, IdString /*port*/) {}
+	virtual bool analyze(vector<int> &taps, const vector<SigBit> &qbits) = 0;
 	virtual bool fixup(Cell *cell, dict<int, SigBit> &taps) = 0;
 };
 
@@ -54,7 +56,7 @@ struct ShregmapOptions
 
 struct ShregmapTechGreenpak4 : ShregmapTech
 {
-	bool analyze(vector<int> &taps)
+	bool analyze(vector<int> &taps, const vector<SigBit> &/*qbits*/)
 	{
 		if (GetSize(taps) > 2 && taps[0] == 0 && taps[2] < 17) {
 			taps.clear();
@@ -91,6 +93,117 @@ struct ShregmapTechGreenpak4 : ShregmapTech
 	}
 };
 
+struct ShregmapTechXilinx7 : ShregmapTech
+{
+	dict<SigBit, std::pair<Cell*,int>> sigbit_to_shiftx_offset;
+	const ShregmapOptions &opts;
+
+	ShregmapTechXilinx7(const ShregmapOptions &opts) : opts(opts) {}
+
+	virtual void init(const Module* module, const SigMap &sigmap) override
+	{
+		for (const auto &i : module->cells_) {
+			auto cell = i.second;
+			if (cell->type != "$shiftx") continue;
+			if (cell->getParam("\\Y_WIDTH") != 1) continue;
+			int j = 0;
+			for (auto bit : sigmap(cell->getPort("\\A")))
+				sigbit_to_shiftx_offset[bit] = std::make_pair(cell, j++);
+			log_assert(j == cell->getParam("\\A_WIDTH").as_int());
+		}
+	}
+
+	virtual void non_chain_user(const SigBit &bit, const Cell *cell, IdString port) override
+	{
+		auto it = sigbit_to_shiftx_offset.find(bit);
+		if (it == sigbit_to_shiftx_offset.end())
+			return;
+		if (cell && cell->type == "$shiftx" && port == "\\A")
+			return;
+		sigbit_to_shiftx_offset.erase(it);
+	}
+
+	virtual bool analyze(vector<int> &taps, const vector<SigBit> &qbits) override
+	{
+		if (GetSize(taps) == 1)
+			return taps[0] >= opts.minlen-1;
+
+		if (taps.back() < opts.minlen-1)
+			return false;
+
+		Cell *shiftx = nullptr;
+		for (int i = 0; i < GetSize(taps); ++i) {
+			// Check taps are sequential
+			if (i != taps[i])
+				return false;
+			// Check taps are not connected to a shift register,
+			// or sequential to the same shift register
+			auto it = sigbit_to_shiftx_offset.find(qbits[i]);
+			if (i == 0) {
+				if (it == sigbit_to_shiftx_offset.end()) {
+					return false;
+				}
+				else {
+					shiftx = it->second.first;
+					int offset = it->second.second;
+					if (offset != i)
+						return false;
+				}
+			}
+			else {
+				if (it == sigbit_to_shiftx_offset.end()) {
+					return false;
+				}
+				else {
+					if (shiftx != it->second.first)
+						return false;
+					int offset = it->second.second;
+					if (offset != i)
+						return false;
+				}
+			}
+		}
+		log_assert(shiftx);
+
+		// Only map if $shiftx exclusively covers the shift register
+		if (GetSize(taps) != shiftx->getParam("\\A_WIDTH").as_int())
+			return false;
+
+		return true;
+	}
+
+	virtual bool fixup(Cell *cell, dict<int, SigBit> &taps) override
+	{
+		const auto &tap = *taps.begin();
+		auto bit = tap.second;
+
+		auto it = sigbit_to_shiftx_offset.find(bit);
+		// If fixed-length, no fixup necessary
+		if (it == sigbit_to_shiftx_offset.end())
+			return true;
+
+		auto newcell = cell->module->addCell(NEW_ID, "$__XILINX_SHREG_");
+		newcell->setParam("\\DEPTH", cell->getParam("\\DEPTH"));
+		newcell->setParam("\\INIT", cell->getParam("\\INIT"));
+		newcell->setParam("\\CLKPOL", cell->getParam("\\CLKPOL"));
+		newcell->setParam("\\ENPOL", cell->getParam("\\ENPOL"));
+
+		newcell->setPort("\\C", cell->getPort("\\C"));
+		newcell->setPort("\\D", cell->getPort("\\D"));
+		newcell->setPort("\\E", cell->getPort("\\E"));
+
+		Cell* shiftx = it->second.first;
+
+		newcell->setPort("\\L", shiftx->getPort("\\B"));
+		newcell->setPort("\\Q", shiftx->getPort("\\Y"));
+
+		cell->module->remove(shiftx);
+
+		return false;
+	}
+};
+
+
 struct ShregmapWorker
 {
 	Module *module;
@@ -113,8 +226,10 @@ struct ShregmapWorker
 		for (auto wire : module->wires())
 		{
 			if (wire->port_output || wire->get_bool_attribute("\\keep")) {
-				for (auto bit : sigmap(wire))
+				for (auto bit : sigmap(wire)) {
 					sigbit_with_non_chain_users.insert(bit);
+					if (opts.tech) opts.tech->non_chain_user(bit, nullptr, {});
+				}
 			}
 
 			if (wire->attributes.count("\\init")) {
@@ -152,8 +267,10 @@ struct ShregmapWorker
 
 			for (auto conn : cell->connections())
 				if (cell->input(conn.first))
-					for (auto bit : sigmap(conn.second))
+					for (auto bit : sigmap(conn.second)) {
 						sigbit_with_non_chain_users.insert(bit);
+						if (opts.tech) opts.tech->non_chain_user(bit, cell, conn.first);
+					}
 		}
 	}
 
@@ -258,7 +375,7 @@ struct ShregmapWorker
 					if (taps.empty() || taps.back() < depth-1)
 						taps.push_back(depth-1);
 
-					if (opts.tech->analyze(taps))
+					if (opts.tech->analyze(taps, qbits))
 						break;
 
 					taps.pop_back();
@@ -377,6 +494,9 @@ struct ShregmapWorker
 	ShregmapWorker(Module *module, const ShregmapOptions &opts) :
 			module(module), sigmap(module), opts(opts), dff_count(0), shreg_count(0)
 	{
+		if (opts.tech)
+			opts.tech->init(module, sigmap);
+
 		make_sigbit_chain_next_prev();
 		find_chain_start_cells();
 
@@ -501,6 +621,12 @@ struct ShregmapPass : public Pass {
 					clkpol = "pos";
 					opts.zinit = true;
 					opts.tech = new ShregmapTechGreenpak4;
+				}
+				else if (tech == "xilinx") {
+					opts.init = true;
+					opts.params = true;
+					enpol = "any_or_none";
+					opts.tech = new ShregmapTechXilinx7(opts);
 				} else {
 					argidx--;
 					break;