1 files changed, 200 insertions, 0 deletions
diff --git a/passes/memory/memory_dff.cc b/passes/memory/memory_dff.cc
new file mode 100644
index 000000000..e188a7af8
--- /dev/null
+++ b/passes/memory/memory_dff.cc
@@ -0,0 +1,200 @@
+/*
+ *  yosys -- Yosys Open SYnthesis Suite
+ *
+ *  Copyright (C) 2012  Clifford Wolf <clifford@clifford.at>
+ *  
+ *  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/register.h"
+#include "kernel/log.h"
+#include <stdlib.h>
+#include <assert.h>
+#include <sstream>
+
+static void normalize_sig(RTLIL::Module *module, RTLIL::SigSpec &sig)
+{
+	for (auto &conn : module->connections)
+		sig.replace(conn.first, conn.second);
+}
+
+static bool find_sig_before_dff(RTLIL::Module *module, RTLIL::SigSpec &sig, RTLIL::SigSpec &clk, bool &clk_polarity, bool after = false)
+{
+	bool replaced_bits = false;
+	normalize_sig(module, sig);
+	sig.expand();
+
+	for (size_t i = 0; i < sig.chunks.size(); i++)
+	{
+		RTLIL::SigChunk &chunk = sig.chunks[i];
+
+		if (chunk.wire == NULL)
+			continue;
+
+		for (auto &cell_it : module->cells)
+		{
+			RTLIL::Cell *cell = cell_it.second;
+
+			if (cell->type != "$dff")
+				continue;
+
+			if (clk != RTLIL::SigSpec(RTLIL::State::Sx)) {
+				if (cell->connections["\\CLK"] != clk)
+					continue;
+				if (cell->parameters["\\CLK_POLARITY"].as_bool() != clk_polarity)
+					continue;
+			}
+
+			RTLIL::SigSpec q_norm = cell->connections[after ? "\\D" : "\\Q"];
+			normalize_sig(module, q_norm);
+
+			RTLIL::SigSpec d = q_norm.extract(chunk, &cell->connections[after ? "\\Q" : "\\D"]);
+			if (d.width != 1)
+				continue;
+
+			assert(d.chunks.size() == 1);
+			chunk = d.chunks[0];
+			clk = cell->connections["\\CLK"];
+			clk_polarity = cell->parameters["\\CLK_POLARITY"].as_bool();
+			replaced_bits = true;
+			goto replaced_this_bit;
+		}
+
+		return false;
+	replaced_this_bit:;
+	}
+
+	sig.optimize();
+	return replaced_bits;
+}
+
+static void handle_wr_cell(RTLIL::Module *module, RTLIL::Cell *cell)
+{
+	log("Checking cell `%s' in module `%s': ", cell->name.c_str(), module->name.c_str());
+
+	RTLIL::SigSpec clk = RTLIL::SigSpec(RTLIL::State::Sx);
+	bool clk_polarity = 0;
+
+	RTLIL::SigSpec sig_addr = cell->connections["\\ADDR"];
+	if (!find_sig_before_dff(module, sig_addr, clk, clk_polarity)) {
+		log("no (compatible) $dff for address input found.\n");
+		return;
+	}
+
+	RTLIL::SigSpec sig_data = cell->connections["\\DATA"];
+	if (!find_sig_before_dff(module, sig_data, clk, clk_polarity)) {
+		log("no (compatible) $dff for data input found.\n");
+		return;
+	}
+
+	RTLIL::SigSpec sig_en = cell->connections["\\EN"];
+	if (!find_sig_before_dff(module, sig_en, clk, clk_polarity)) {
+		log("no (compatible) $dff for enable input found.\n");
+		return;
+	}
+
+	cell->connections["\\CLK"] = clk;
+	cell->connections["\\ADDR"] = sig_addr;
+	cell->connections["\\DATA"] = sig_data;
+	cell->connections["\\EN"] = sig_en;
+	cell->parameters["\\CLK_ENABLE"] = RTLIL::Const(1);
+	cell->parameters["\\CLK_POLARITY"] = RTLIL::Const(clk_polarity);
+	log("merged $dff to cell.\n");
+}
+
+#if 1
+static void handle_rd_cell(RTLIL::Module*, RTLIL::Cell*)
+{
+	// merging dffs into read ports isn't neccessary for memory_map.
+	// we'd loose the information if the register is on the address or
+	// data port and wouldn't get any benefits.
+}
+#else
+static void disconnect_dff(RTLIL::Module *module, RTLIL::SigSpec sig)
+{
+	normalize_sig(module, sig);
+	sig.sort_and_unify();
+
+	std::stringstream sstr;
+	sstr << "$memory_dff_disconnected$" << (RTLIL::autoidx++);
+
+	RTLIL::Wire *wire = new RTLIL::Wire;
+	wire->name = sstr.str();
+	wire->width = sig.width;
+	module->wires[wire->name] = wire;
+
+	RTLIL::SigSpec newsig(wire);
+
+	for (auto &cell_it : module->cells) {
+		RTLIL::Cell *cell = cell_it.second;
+		if (cell->type == "$dff")
+			cell->connections["\\Q"].replace(sig, newsig);
+	}
+}
+
+static void handle_rd_cell(RTLIL::Module *module, RTLIL::Cell *cell)
+{
+	log("Checking cell `%s' in module `%s': ", cell->name.c_str(), module->name.c_str());
+
+	bool clk_polarity = 0;
+
+	RTLIL::SigSpec clk_addr = RTLIL::SigSpec(RTLIL::State::Sx);
+	RTLIL::SigSpec sig_addr = cell->connections["\\ADDR"];
+	if (find_sig_before_dff(module, sig_addr, clk_addr, clk_polarity))
+	{
+		cell->connections["\\CLK"] = clk_addr;
+		cell->connections["\\ADDR"] = sig_addr;
+		cell->parameters["\\CLK_ENABLE"] = RTLIL::Const(1);
+		cell->parameters["\\CLK_POLARITY"] = RTLIL::Const(clk_polarity);
+		log("merged address $dff to cell.\n");
+		return;
+	}
+
+	RTLIL::SigSpec clk_data = RTLIL::SigSpec(RTLIL::State::Sx);
+	RTLIL::SigSpec sig_data = cell->connections["\\DATA"];
+	if (find_sig_before_dff(module, sig_data, clk_data, clk_polarity, true))
+	{
+		disconnect_dff(module, sig_data);
+		cell->connections["\\CLK"] = clk_data;
+		cell->connections["\\DATA"] = sig_data;
+		cell->parameters["\\CLK_ENABLE"] = RTLIL::Const(1);
+		cell->parameters["\\CLK_POLARITY"] = RTLIL::Const(clk_polarity);
+		log("merged data $dff to cell.\n");
+		return;
+	}
+
+	log("no (compatible) $dff found.\n");
+}
+#endif
+
+static void handle_module(RTLIL::Module *module)
+{
+	for (auto &cell_it : module->cells) {
+		if (cell_it.second->type == "$memwr" && !cell_it.second->parameters["\\CLK_ENABLE"].as_bool())
+				handle_wr_cell(module, cell_it.second);
+		if (cell_it.second->type == "$memrd" && !cell_it.second->parameters["\\CLK_ENABLE"].as_bool())
+				handle_rd_cell(module, cell_it.second);
+	}
+}
+
+struct MemoryDffPass : public Pass {
+	MemoryDffPass() : Pass("memory_dff") { }
+	virtual void execute(std::vector<std::string> args, RTLIL::Design *design) {
+		log_header("Executing MEMORY_DFF pass (merging $dff cells to $memrd and $memwr).\n");
+		extra_args(args, 1, design);
+		for (auto &mod_it : design->modules)
+			handle_module(mod_it.second);
+	}
+} MemoryDffPass;
+