yosys/passes/silimate/annotate_ff_width.cc

/*
 *  yosys -- Yosys Open SYnthesis Suite
 *
 *  Copyright (C) 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"
USING_YOSYS_NAMESPACE
PRIVATE_NAMESPACE_BEGIN

static std::string ff_base_name(const std::string &name)
{
	if (!name.empty() && name.back() == ']') {
		size_t open = name.rfind('[');
		if (open != std::string::npos && open + 1 < name.size() - 1) {
			std::string inner = name.substr(open + 1, name.size() - open - 2);
			if (inner.find_first_not_of("0123456789") == std::string::npos)
				return name.substr(0, open);
		}
	}
	return name;
}

struct AnnotateFfWidthPass : public Pass {
	AnnotateFfWidthPass() : Pass("annotate_ff_width", "annotate every flip-flop with its bit-width") { }
	void help() override
	{
		//   |---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|
		log("\n");
		log("    annotate_ff_width [selection]\n");
		log("\n");
		log("Annotate every flip-flop with its width.");
		log("\n");
	}
	void execute(std::vector<std::string> args, RTLIL::Design *design) override
	{
		log_header(design, "Executing ANNOTATE_FF_WIDTH pass.\n");
		size_t argidx;
		for (argidx = 1; argidx < args.size(); argidx++)
			break;
		extra_args(args, argidx, design);

		// Loop through all flip-flops in a module and annotate with their width
		int annotated = 0;
		for (auto module : design->selected_modules()) {
			// First, count the number of flip-flops of the same base name.
			dict<std::string, int> name_counts;
			std::vector<std::pair<RTLIL::Cell *, std::string>> ff_cells;
			for (auto cell : module->selected_cells()) {
				if (!RTLIL::builtin_ff_cell_types().count(cell->type))
					continue;
				std::string base = ff_base_name(cell->name.str());
				name_counts[base]++;
				ff_cells.push_back({cell, base});
			}
			// Then, annotate each flip-flop with the count for its base name.
			for (auto &it : ff_cells) {
				int width = name_counts[it.second];
				it.first->set_string_attribute(ID(ff_width), std::to_string(width));
				annotated++;
			}
		}
		log("Annotated %d flip-flops.\n", annotated);
	}
} AnnotateFfWidthPass;
PRIVATE_NAMESPACE_END