yosys/passes/silimate/reg_rename.cc

/*
 *  yosys -- Yosys Open SYnthesis Suite
 *
 *  Copyright (C) 2012  Claire Xenia Wolf <claire@yosyshq.com>
 *                2026  Stan Lee          <stan@silimate.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/fstdata.h"
#include <regex>

USING_YOSYS_NAMESPACE
PRIVATE_NAMESPACE_BEGIN

struct RegRenamePass : public Pass {
	RegRenamePass() : Pass("reg_rename", "renames register output wires to the correct register name and creates new wires for multi-bit registers for correct VCD register annotations.") { }
	void help() override
	{
		//   |---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|
		log("\n");
		log("    reg_rename [options]\n");
		log("\n");
		log("    -vcd <filename>\n");
		log("        vcd file to extract original register width from\n");
		log("\n");
	}
	void execute(std::vector<std::string> args, RTLIL::Design *design) override
	{
		log_header(design, "Executing reg_rename pass\n");


		std::string vcd_filename;
		size_t argidx;
		for (argidx = 1; argidx < args.size(); argidx++) {
			if (args[argidx] == "-vcd" && argidx+1 < args.size()) {
				vcd_filename = args[++argidx];
				continue;
			}
			break;
		}
		extra_args(args, argidx, design);

		// Populate data structure with register widths from VCD file
		dict<std::string, int> vcd_reg_widths;
		if (!vcd_filename.empty()) {
			log("Reading VCD file: %s\n", vcd_filename.c_str());
			try {
				FstData fst(vcd_filename);
				// Iterate through all variables in the VCD file
				for (auto &var : fst.getVars()) {
					// Only process register variables
					if (var.is_reg) {
						std::string reg_name = var.name;
						// Remove bracket notation if present
						if (auto pos = reg_name.find('['); pos != std::string::npos)
							reg_name.erase(pos);
						// Add RTLIL backslash prefix if not present
						if (reg_name.empty() || reg_name[0] != '\\')
							reg_name = "\\" + reg_name;
						vcd_reg_widths[reg_name] = var.width;
						log("Found register '%s' with width %d\n", reg_name.c_str(), var.width);
					}
				}
				log("Extracted %d register widths from VCD file\n", GetSize(vcd_reg_widths));
			} catch (const std::exception &e) {
				log_error("Failed to read VCD file '%s': %s\n", vcd_filename.c_str(), e.what());
			}
		} else {
			log_error("No VCD file provided. Please provide a VCD file with the -vcd option.\n");
		}

		// Regex to match registers to output wires
		// .*_reg[NUMBER] or .*_reg, can match NUMBER and part before _reg
		std::regex reg_regex("(.*)_reg(?:\\[(\\d+)\\])?$");
		uint32_t count = 0;
		for (auto module : design->selected_modules()) {
			pool<Wire *> wiresToRemove; // pool of wires to remove from the netlist
			for (auto cell : module->selected_cells()) {

				// Only check register cell
				if (RTLIL::builtin_ff_cell_types().count(cell->type)) {

					// Rename register output wires to corresponding testbench names
					std::smatch match;
					std::string name = cell->name.c_str();
					if (std::regex_match(name, match, reg_regex)) {

						// baseName is the part before _reg
						std::string baseName = match[1].str();

						// Check if the register is a multi-bit register (look for [NUMBER] match in regex)
						bool isMultiBit = match.size() > 2 && match[2].matched;
						std::string indexStr;
						for (auto conn : cell->connections()) {
							if (conn.first == ID::Q && conn.second.is_wire()) {
								Wire *oldWire = conn.second.as_wire();

								// Skip if this wire is a module port (input/output)
								if (oldWire->port_input || oldWire->port_output) {
									log("Skipping port wire %s in register renaming for cell %s in module %s\n", 
										oldWire->name.c_str(), log_id(cell), log_id(module));
									continue;
								}

								// Different cases for multi-bit and single-bit registers
								if (isMultiBit) {

									// Index of the register
									int index = 0;
									try {
										index = std::stoi(match[2].str());
									} catch (const std::exception &e) {
										log_warning("Failed to convert index %s to integer in register %s: %s\n",
											match[2].str().c_str(), log_id(cell), e.what());
										continue;
									}

									// Get or create the multi-bit wire
									Wire *newWire = module->wire(RTLIL::escape_id(baseName));
									if (newWire == nullptr) {
										// Wire doesn't exist, create it with the original register width
										int origRegWidth = vcd_reg_widths[baseName];
										if (origRegWidth == 0) {
											log_warning("Register '%s' not found in VCD file or has width 0\n", baseName.c_str());
											continue;
										}
										log("Creating multi-bit wire %s with width %d in module %s\n",
											baseName.c_str(), origRegWidth, log_id(module));
										newWire = module->addWire(RTLIL::escape_id(baseName), origRegWidth);
									}

									// Log that the new wire is being connected to the register
									log("Connecting register wire %s[%d] to bit %d of %s in module %s\n",
										newWire->name.c_str(), index, index, log_id(cell), log_id(module));

									// Replace all uses of oldWire with newWire[index]
									auto rewriter = [&](SigSpec &sig) {
										sig.replace(SigBit(oldWire), SigSpec(newWire, index, 1));
									};
									module->rewrite_sigspecs(rewriter);

									// Mark old wire for deletion
									log("Marking old wire %s for deletion in module %s\n",
										oldWire->name.c_str(), log_id(module));
									wiresToRemove.insert(oldWire);
									count++;
								} else {
									IdString target_name = RTLIL::escape_id(baseName);
									if (oldWire->name != target_name) {
										// Check if target name already exists
										if (module->wire(target_name)) {
											log("Skipping rename: wire %s already exists in module %s\n",
												target_name.c_str(), log_id(module));
										} else {
											// Rename single-bit register to correct name from RTL
											log("Renaming register wire %s to %s for cell %s in module %s\n", 
												oldWire->name.c_str(), target_name.c_str(), log_id(cell), log_id(module));
											module->rename(oldWire, target_name);
											count++;
										}
									}
								}
							}
						}
					}
				}
			}
			module->remove(wiresToRemove);
		}

		// End
		log("Renamed %d registers in %d modules\n", count, design->selected_modules().size());
		log_flush();
	}
} RegRenamePass;

PRIVATE_NAMESPACE_END