cellmatch: New pass for picking out standard cells automatically

passes/techmap/Makefile.inc

@@ -48,6 +48,7 @@ OBJS += passes/techmap/dfflegalize.o
 OBJS += passes/techmap/dffunmap.o
 OBJS += passes/techmap/flowmap.o
 OBJS += passes/techmap/extractinv.o
+OBJS += passes/techmap/cellmatch.o
 endif
 
 ifeq ($(DISABLE_SPAWN),0)

passes/techmap/cellmatch.cc

@@ -0,0 +1,312 @@
+#include "kernel/celltypes.h"
+#include "kernel/register.h"
+#include "kernel/rtlil.h"
+#include "kernel/sigtools.h"
+#include "kernel/consteval.h"
+#include "kernel/utils.h"
+
+#include <algorithm>
+
+USING_YOSYS_NAMESPACE
+YOSYS_NAMESPACE_BEGIN
+
+// return module's inputs in canonical order
+SigSpec module_inputs(Module *m)
+{
+	SigSpec ret;
+	for (auto port : m->ports) {
+		Wire *w = m->wire(port);
+		if (!w->port_input)
+			continue;
+		if (w->width != 1)
+			log_error("Unsupported wide port (%s) of non-unit width found in module %s.\n",
+					  log_id(w), log_id(m));
+		ret.append(w);
+	}
+	return ret;
+}
+
+// return module's outputs in canonical order
+SigSpec module_outputs(Module *m)
+{
+	SigSpec ret;
+	for (auto port : m->ports) {
+		Wire *w = m->wire(port);
+		if (!w->port_output)
+			continue;
+		if (w->width != 1)
+			log_error("Unsupported wide port (%s) of non-unit width found in module %s.\n",
+					  log_id(w), log_id(m));
+		ret.append(w);
+	}
+	return ret;
+}
+
+// Permute the inputs of a single-output k-LUT according to varmap
+uint64_t permute_lut(uint64_t lut, const std::vector<int> &varmap)
+{
+	int k = varmap.size();
+	uint64_t ret = 0;
+	// Index j iterates over all bits in lut.
+	// When (j & 1 << n) is true,
+	//  (lut & 1 << j) represents an output value where input var n is set.
+	// We use this fact to permute the LUT such that
+	// every variable n is remapped to varmap[n].
+	for (int j = 0; j < 1 << k; j++) {
+		int m = 0;
+		for (int l = 0; l < k; l++)
+		if (j & 1 << l)
+			m |= 1 << varmap[l];
+		if (lut & 1 << m)
+			ret |= 1 << j;
+	}
+	return ret;
+}
+
+// Find the LUT with the minimum integer representation
+// such that it is a permutation of the given lut.
+// The resulting LUT becomes the "fingerprint" of the "permutation class".
+// This function checks all possible input permutations.
+uint64_t p_class(int k, uint64_t lut)
+{
+	std::vector<int> map;
+	for (int j = 0; j < k; j++)
+		map.push_back(j);
+
+	uint64_t repr = ~(uint64_t) 0;
+	std::vector<int> repr_vars;
+	while (true) {
+		uint64_t perm = permute_lut(lut, map);
+		if (perm <= repr) {
+			repr = perm;
+			repr_vars = map;
+		}
+		if (!std::next_permutation(map.begin(), map.end()))
+			break;
+	}
+	return repr;
+}
+
+// Represent module m as N single-output k-LUTs
+// where k is the number of module inputs,
+//   and N is the number of module outputs.
+bool derive_module_luts(Module *m, std::vector<uint64_t> &luts)
+{
+	CellTypes ff_types;
+	ff_types.setup_stdcells_mem();
+	for (auto cell : m->cells()) {
+		if (ff_types.cell_known(cell->type)) {
+			log("Ignoring module '%s' which isn't purely combinational.\n", log_id(m));
+			return false;
+		}
+	}
+
+	SigSpec inputs = module_inputs(m);
+	SigSpec outputs = module_outputs(m);
+	int ninputs = inputs.size(), noutputs = outputs.size();
+
+	if (ninputs > 6) {
+		log_warning("Skipping module %s with more than 6 inputs bits.\n", log_id(m));
+		return false;
+	}
+
+	luts.clear();
+	luts.resize(noutputs);
+
+	ConstEval ceval(m);
+	for (int i = 0; i < 1 << ninputs; i++) {
+		ceval.clear();
+		for (int j = 0; j < ninputs; j++)
+			ceval.set(inputs[j], (i & (1 << j)) ? State::S1 : State::S0);
+		for (int j = 0; j < noutputs; j++) {
+			SigSpec bit = outputs[j];
+
+			if (!ceval.eval(bit)) {
+				log("Failed to evaluate output '%s' in module '%s'.\n",
+					log_signal(outputs[j]), log_id(m));
+				return false;
+			}
+
+			log_assert(ceval.eval(bit));
+
+			if (bit[0] == State::S1)
+				luts[j] |= 1 << i;
+		}
+	}
+
+	return true;
+}
+
+struct CellmatchPass : Pass {
+	CellmatchPass() : Pass("cellmatch", "match cells to their targets in cell library") {}
+	void help() override
+	{
+		//   |---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|
+		log("\n");
+		log("    cellmatch -lib <design> [module selection]\n");
+		log("\n");
+		log("This pass identifies functionally equivalent counterparts between each of the\n");
+		log("selected modules and a module from the secondary design <design>. For every such\n");
+		log("correspondence found, a techmap rule is generated for mapping instances of the\n");
+		log("former to instances of the latter. This techmap rule is saved in yet another\n");
+		log("design called '$cellmatch', which is created if non-existent.\n");
+		log("\n");
+		log("This pass restricts itself to combinational modules. Modules are functionally\n");
+		log("equivalent as long as their truth tables are identical upto a permutation of\n");
+		log("inputs and outputs. The supported number of inputs is limited to 6.\n");
+		log("\n");
+	}
+	void execute(std::vector<std::string> args, RTLIL::Design *d) override
+	{
+		log_header(d, "Executing CELLMATCH pass. (match cells)\n");
+
+		size_t argidx;
+		bool lut_attrs = false;
+		Design *lib = NULL;
+		for (argidx = 1; argidx < args.size(); argidx++) {
+			if (args[argidx] == "-lut_attrs") {
+				// an undocumented debugging option
+				lut_attrs = true;
+			} else if (args[argidx] == "-lib" && argidx + 1 < args.size()) {
+				if (!saved_designs.count(args[++argidx]))
+					log_cmd_error("No design '%s' found!\n", args[argidx].c_str());
+				lib = saved_designs.at(args[argidx]);
+			} else {
+				break;
+			}
+		}
+		extra_args(args, argidx, d);
+
+		if (!lib && !lut_attrs)
+			log_cmd_error("Missing required -lib option.\n");
+
+		struct Target {
+			Module *module;
+			std::vector<uint64_t> luts;
+		};
+
+		dict<pool<uint64_t>, std::vector<Target>> targets;
+
+		if (lib)
+		for (auto m : lib->modules()) {
+			pool<uint64_t> p_classes;
+
+			// produce a fingerprint in p_classes
+			int ninputs = module_inputs(m).size();
+			std::vector<uint64_t> luts;
+			if (!derive_module_luts(m, luts))
+				continue;
+			for (auto lut : luts)
+				p_classes.insert(p_class(ninputs, lut));
+
+			log_debug("Registered %s\n", log_id(m));
+
+			// save as a viable target
+			targets[p_classes].push_back(Target{m, luts});
+		}
+
+		auto r = saved_designs.emplace("$cellmatch", nullptr);
+		if (r.second)
+			r.first->second = new Design;
+		Design *map_design = r.first->second;
+
+		for (auto m : d->selected_whole_modules_warn()) {
+			std::vector<uint64_t> luts;
+			if (!derive_module_luts(m, luts))
+				continue;
+
+			SigSpec inputs = module_inputs(m);
+			SigSpec outputs = module_outputs(m);
+
+			if (lut_attrs) {
+				int no = 0;
+				for (auto bit : outputs) {
+					log_assert(bit.is_wire());
+					bit.wire->attributes[ID(p_class)] = p_class(inputs.size(), luts[no]);
+					bit.wire->attributes[ID(lut)] = luts[no++];
+				}
+			}
+
+			// fingerprint
+			pool<uint64_t> p_classes;
+			for (auto lut : luts)
+				p_classes.insert(p_class(inputs.size(), lut));
+
+			for (auto target : targets[p_classes]) {
+				log_debug("Candidate %s for matching to %s\n", log_id(target.module), log_id(m));
+
+				SigSpec target_inputs = module_inputs(target.module);
+				SigSpec target_outputs = module_outputs(target.module);
+
+				if (target_inputs.size() != inputs.size())
+					continue;
+
+				if (target_outputs.size() != outputs.size())
+					continue;
+
+				std::vector<int> input_map;
+				for (int i = 0; i < inputs.size(); i++)
+					input_map.push_back(i);
+
+				bool found_match = false;
+				// For each input_map
+				while (!found_match) {
+					std::vector<int> output_map;
+					for (int i = 0; i < outputs.size(); i++)
+						output_map.push_back(i);
+
+					// For each output_map
+					while (!found_match) {
+						int out_no = 0;
+						bool match = true;
+						for (auto lut : luts) {
+							if (permute_lut(target.luts[output_map[out_no++]], input_map) != lut) {
+								match = false;
+								break;
+							}
+						}
+
+						if (match) {
+							log("Module %s matches %s\n", log_id(m), log_id(target.module));
+							// Add target.module to map_design ("$cellmatch")
+							// as a techmap rule to match m and replace it with target.module
+							Module *map = map_design->addModule(stringf("\\_60_%s_%s", log_id(m), log_id(target.module)));
+							Cell *cell = map->addCell(ID::_TECHMAP_REPLACE_, target.module->name);
+
+							map->attributes[ID(techmap_celltype)] = m->name.str();
+
+							for (int i = 0; i < outputs.size(); i++) {
+								log_assert(outputs[i].is_wire());
+								Wire *w = map->addWire(outputs[i].wire->name, 1);
+								w->port_id = outputs[i].wire->port_id;
+								w->port_output = true;
+								log_assert(target_outputs[output_map[i]].is_wire());
+								cell->setPort(target_outputs[output_map[i]].wire->name, w);
+							}
+
+							for (int i = 0; i < inputs.size(); i++) {
+								log_assert(inputs[i].is_wire());
+								Wire *w = map->addWire(inputs[i].wire->name, 1);
+								w->port_id = inputs[i].wire->port_id;
+								w->port_input = true;
+								log_assert(target_inputs[input_map[i]].is_wire());
+								cell->setPort(target_inputs[input_map[i]].wire->name, w);
+							}
+
+							map->fixup_ports();
+							found_match = true;
+						}
+
+						if (!std::next_permutation(output_map.begin(), output_map.end()))
+							break;
+					}
+
+					if (!std::next_permutation(input_map.begin(), input_map.end()))
+						break;
+				}
+			}
+		}
+	}
+} CellmatchPass;
+
+YOSYS_NAMESPACE_END