cxxrtl: add a VCD writer using debug information.

backends/cxxrtl/cxxrtl_vcd.h

@@ -0,0 +1,194 @@
+/*
+ *  yosys -- Yosys Open SYnthesis Suite
+ *
+ *  Copyright (C) 2020  whitequark <whitequark@whitequark.org>
+ *
+ *  Permission to use, copy, modify, and/or distribute this software for any
+ *  purpose with or without fee is hereby granted.
+ *
+ *  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.
+ *
+ */
+
+#ifndef CXXRTL_VCD_H
+#define CXXRTL_VCD_H
+
+#include <backends/cxxrtl/cxxrtl.h>
+
+namespace cxxrtl {
+
+class vcd_writer {
+	struct variable {
+		size_t ident;
+		size_t width;
+		chunk_t *curr;
+	};
+
+	std::vector<std::string> current_scope;
+	std::vector<variable> variables;
+	bool streaming = false;
+
+	void emit_timescale(unsigned number, const std::string &unit) {
+		assert(!streaming);
+		assert(number == 1 || number == 10 || number == 100);
+		assert(unit == "s" || unit == "ms" || unit == "us" ||
+		       unit == "ns" || unit == "ps" || unit == "fs");
+		buffer += "$timescale " + std::to_string(number) + " " + unit + " $end\n";
+	}
+
+	void emit_scope(const std::vector<std::string> &scope) {
+		assert(!streaming);
+		while (current_scope.size() > scope.size() ||
+		       (current_scope.size() > 0 &&
+			current_scope[current_scope.size() - 1] != scope[current_scope.size() - 1])) {
+			buffer += "$upscope $end\n";
+			current_scope.pop_back();
+		}
+		while (current_scope.size() < scope.size()) {
+			buffer += "$scope module " + scope[current_scope.size()] + " $end\n";
+			current_scope.push_back(scope[current_scope.size()]);
+		}
+	}
+
+	void emit_ident(size_t ident) {
+		do {
+			buffer += '!' + ident % 94; // "base94"
+			ident /= 94;
+		} while (ident != 0);
+	}
+
+	void emit_var(const variable &var, const std::string &type, const std::string &name) {
+		assert(!streaming);
+		buffer += "$var " + type + " " + std::to_string(var.width) + " ";
+		emit_ident(var.ident);
+		buffer += " " + name + " $end\n";
+	}
+
+	void emit_enddefinitions() {
+		assert(!streaming);
+		buffer += "$enddefinitions $end\n";
+		streaming = true;
+	}
+
+	void emit_time(uint64_t timestamp) {
+		assert(streaming);
+		buffer += "#" + std::to_string(timestamp) + "\n";
+	}
+
+	void emit_scalar(const variable &var) {
+		assert(streaming);
+		assert(var.width == 1);
+		buffer += (*var.curr ? '1' : '0');
+		emit_ident(var.ident);
+		buffer += '\n';
+	}
+
+	void emit_vector(const variable &var) {
+		assert(streaming);
+		buffer += 'b';
+		for (size_t bit = var.width - 1; bit != (size_t)-1; bit--) {
+			bool bit_curr = var.curr[bit / (8 * sizeof(chunk_t))] & (1 << (bit % (8 * sizeof(chunk_t))));
+			buffer += (bit_curr ? '1' : '0');
+		}
+		buffer += ' ';
+		emit_ident(var.ident);
+		buffer += '\n';
+	}
+
+	static std::vector<std::string> split_hierarchy(const std::string &hier_name) {
+		std::vector<std::string> hierarchy;
+		size_t prev = 0;
+		while (true) {
+			size_t curr = hier_name.find_first_of(' ', prev + 1);
+			if (curr > hier_name.size())
+				curr = hier_name.size();
+			if (curr > prev + 1)
+				hierarchy.push_back(hier_name.substr(prev, curr - prev));
+			if (curr == hier_name.size())
+				break;
+			prev = curr + 1;
+		}
+		return hierarchy;
+	}
+
+public:
+	std::string buffer;
+
+	void timescale(unsigned number, const std::string &unit) {
+		emit_timescale(number, unit);
+	}
+
+	void add(const std::string &hier_name, const debug_item &item) {
+		std::vector<std::string> scope = split_hierarchy(hier_name);
+		std::string name = scope.back();
+		scope.pop_back();
+
+		emit_scope(scope);
+		switch (item.type) {
+			// Not the best naming but oh well...
+			case debug_item::VALUE:
+				variables.emplace_back(variable { variables.size(), item.width, item.curr });
+				emit_var(variables.back(), "wire", name);
+				break;
+			case debug_item::WIRE:
+				variables.emplace_back(variable { variables.size(), item.width, item.curr });
+				emit_var(variables.back(), "reg", name);
+				break;
+			case debug_item::MEMORY: {
+				const size_t stride = (item.width + (sizeof(chunk_t) * 8 - 1)) / (sizeof(chunk_t) * 8);
+				for (size_t index = 0; index < item.depth; index++) {
+					chunk_t *nth_curr = &item.curr[stride * index];
+					std::string nth_name = name + '[' + std::to_string(index) + ']';
+					variables.emplace_back(variable { variables.size(), item.width, nth_curr });
+					emit_var(variables.back(), "reg", nth_name);
+				}
+				break;
+			}
+		}
+	}
+
+	template<class Filter>
+	void add(const debug_items &items, const Filter &filter) {
+		// `debug_items` is a map, so the items are already sorted in an order optimal for emitting
+		// VCD scope sections.
+		for (auto &it : items)
+			if (filter(it.first, it.second))
+				add(it.first, it.second);
+	}
+
+	void add(const debug_items &items) {
+		this->template add(items, [](const std::string &, const debug_item &) {
+			return true;
+		});
+	}
+
+	void add_without_memories(const debug_items &items) {
+		this->template add(items, [](const std::string &, const debug_item &item) {
+			return item.type == debug_item::VALUE || item.type == debug_item::WIRE;
+		});
+	}
+
+	void sample(uint64_t timestamp) {
+		if (!streaming) {
+			emit_scope({});
+			emit_enddefinitions();
+		}
+		emit_time(timestamp);
+		for (auto var : variables) {
+			if (var.width == 1)
+				emit_scalar(var);
+			else
+				emit_vector(var);
+		}
+	}
+};
+
+}
+
+#endif