From c851f51656a80edd47eabc7fafbe69d56dea9fae Mon Sep 17 00:00:00 2001
From: Clifford Wolf <clifford@clifford.at>
Date: Fri, 18 Sep 2015 21:55:48 +0200
Subject: [PATCH] Added lut2mux pass

---
 passes/techmap/Makefile.inc |  1 +
 passes/techmap/lut2mux.cc   | 93 +++++++++++++++++++++++++++++++++++++
 2 files changed, 94 insertions(+)
 create mode 100644 passes/techmap/lut2mux.cc

diff --git a/passes/techmap/Makefile.inc b/passes/techmap/Makefile.inc
index af4816a72..373203ed9 100644
--- a/passes/techmap/Makefile.inc
+++ b/passes/techmap/Makefile.inc
@@ -20,6 +20,7 @@ OBJS += passes/techmap/pmuxtree.o
 OBJS += passes/techmap/muxcover.o
 OBJS += passes/techmap/aigmap.o
 OBJS += passes/techmap/tribuf.o
+OBJS += passes/techmap/lut2mux.o
 endif
 
 GENFILES += passes/techmap/techmap.inc
diff --git a/passes/techmap/lut2mux.cc b/passes/techmap/lut2mux.cc
new file mode 100644
index 000000000..fe55e499a
--- /dev/null
+++ b/passes/techmap/lut2mux.cc
@@ -0,0 +1,93 @@
+/*
+ *  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/yosys.h"
+#include "kernel/sigtools.h"
+
+USING_YOSYS_NAMESPACE
+PRIVATE_NAMESPACE_BEGIN
+
+int lut2mux(Cell *cell)
+{
+	SigSpec sig_a = cell->getPort("\\A");
+	SigSpec sig_y = cell->getPort("\\Y");
+	Const lut = cell->getParam("\\LUT");
+	int count = 1;
+
+	if (GetSize(sig_a) == 1)
+	{
+		cell->module->addMuxGate(NEW_ID, lut[0], lut[1], sig_a, sig_y);
+	}
+	else
+	{
+		SigSpec sig_a_hi = sig_a[GetSize(sig_a)-1];
+		SigSpec sig_a_lo = sig_a.extract(0, GetSize(sig_a)-1);
+		SigSpec sig_y1 = cell->module->addWire(NEW_ID);
+		SigSpec sig_y2 = cell->module->addWire(NEW_ID);
+
+		Const lut1 = lut.extract(0, GetSize(lut)/2);
+		Const lut2 = lut.extract(GetSize(lut)/2, GetSize(lut)/2);
+
+		count += lut2mux(cell->module->addLut(NEW_ID, sig_a_lo, sig_y1, lut1));
+		count += lut2mux(cell->module->addLut(NEW_ID, sig_a_lo, sig_y2, lut2));
+
+		cell->module->addMuxGate(NEW_ID, sig_y1, sig_y2, sig_a_hi, sig_y);
+	}
+
+	cell->module->remove(cell);
+	return count;
+}
+
+struct Lut2muxPass : public Pass {
+	Lut2muxPass() : Pass("lut2mux", "convert $lut to $_MUX_") { }
+	virtual void help()
+	{
+		//   |---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|
+		log("\n");
+		log("    lut2mux [options] [selection]\n");
+		log("\n");
+		log("This pass converts $lut cells to $_MUX_ gates.\n");
+		log("\n");
+	}
+	virtual void execute(std::vector<std::string> args, RTLIL::Design *design)
+	{
+		log_header("Executing LUT2MUX pass (mapping to constant drivers).\n");
+
+		size_t argidx;
+		for (argidx = 1; argidx < args.size(); argidx++)
+		{
+			// if (args[argidx] == "-v") {
+			// 	continue;
+			// }
+			break;
+		}
+		extra_args(args, argidx, design);
+
+		for (auto module : design->selected_modules())
+		for (auto cell : module->selected_cells()) {
+			if (cell->type == "$lut") {
+				IdString cell_name = cell->name;
+				int count = lut2mux(cell);
+				log("Converted %s.%s to %d MUX cells.\n", log_id(module), log_id(cell_name), count);
+			}
+		}
+	}
+} Lut2muxPass;
+
+PRIVATE_NAMESPACE_END