From 9d0b69edaafa98c4bb67974415f354a344a5821d Mon Sep 17 00:00:00 2001
From: Clifford Wolf <clifford@clifford.at>
Date: Sun, 2 Feb 2014 22:11:08 +0100
Subject: [PATCH] Added opt_const -mux_bool

---
 passes/opt/opt.cc       | 22 ++++++++++++++++++----
 passes/opt/opt_const.cc | 32 +++++++++++++++++++++++++++++---
 2 files changed, 47 insertions(+), 7 deletions(-)

diff --git a/passes/opt/opt.cc b/passes/opt/opt.cc
index 467baf235..53c27e0f5 100644
--- a/passes/opt/opt.cc
+++ b/passes/opt/opt.cc
@@ -31,7 +31,7 @@ struct OptPass : public Pass {
 	{
 		//   |---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|
 		log("\n");
-		log("    opt [selection]\n");
+		log("    opt [-mux_undef] [-mux_bool] [selection]\n");
 		log("\n");
 		log("This pass calls all the other opt_* passes in a useful order. This performs\n");
 		log("a series of trivial optimizations and cleanups. This pass executes the other\n");
@@ -46,16 +46,30 @@ struct OptPass : public Pass {
 		log("        opt_share\n");
 		log("        opt_rmdff\n");
 		log("        opt_clean\n");
-		log("        opt_const\n");
+		log("        opt_const [-mux_undef] [-mux_bool]\n");
 		log("    while [changed design]\n");
 		log("\n");
 	}
 	virtual void execute(std::vector<std::string> args, RTLIL::Design *design)
 	{
+		std::string opt_const_args;
+
 		log_header("Executing OPT pass (performing simple optimizations).\n");
 		log_push();
 
-		extra_args(args, 1, design);
+		size_t argidx;
+		for (argidx = 1; argidx < args.size(); argidx++) {
+			if (args[argidx] == "-mux_undef") {
+				opt_const_args += " -mux_undef";
+				continue;
+			}
+			if (args[argidx] == "-mux_bool") {
+				opt_const_args += " -mux_bool";
+				continue;
+			}
+			break;
+		}
+		extra_args(args, argidx, design);
 
 		log_header("Optimizing in-memory representation of design.\n");
 		design->optimize();
@@ -69,7 +83,7 @@ struct OptPass : public Pass {
 			Pass::call(design, "opt_share");
 			Pass::call(design, "opt_rmdff");
 			Pass::call(design, "opt_clean");
-			Pass::call(design, "opt_const");
+			Pass::call(design, "opt_const" + opt_const_args);
 			if (OPT_DID_SOMETHING == false)
 				break;
 			log_header("Rerunning OPT passes. (Maybe there is more to do..)\n");
diff --git a/passes/opt/opt_const.cc b/passes/opt/opt_const.cc
index 2b2c83a51..535dd02fc 100644
--- a/passes/opt/opt_const.cc
+++ b/passes/opt/opt_const.cc
@@ -42,7 +42,7 @@ void replace_cell(RTLIL::Module *module, RTLIL::Cell *cell, std::string info, st
 	did_something = true;
 }
 
-void replace_const_cells(RTLIL::Design *design, RTLIL::Module *module, bool consume_x, bool mux_undef)
+void replace_const_cells(RTLIL::Design *design, RTLIL::Module *module, bool consume_x, bool mux_undef, bool mux_bool)
 {
 	if (!design->selected(module))
 		return;
@@ -244,6 +244,24 @@ void replace_const_cells(RTLIL::Design *design, RTLIL::Module *module, bool cons
 			}
 		}
 
+		if (mux_bool && cell->type == "$mux" && cell->connections["\\A"] == RTLIL::SigSpec(0, 1) && cell->connections["\\B"] == RTLIL::SigSpec(1, 1)) {
+			replace_cell(module, cell, "mux_bool", "\\Y", cell->connections["\\S"]);
+			goto next_cell;
+		}
+
+		if (mux_bool && cell->type == "$mux" && cell->connections["\\A"] == RTLIL::SigSpec(1, 1) && cell->connections["\\B"] == RTLIL::SigSpec(0, 1)) {
+			cell->connections["\\A"] = cell->connections["\\S"];
+			cell->connections.erase("\\B");
+			cell->connections.erase("\\S");
+			cell->parameters["\\A_WIDTH"] = cell->parameters["\\WIDTH"];
+			cell->parameters["\\Y_WIDTH"] = cell->parameters["\\WIDTH"];
+			cell->parameters["\\A_SIGNED"] = 0;
+			cell->parameters.erase("\\WIDTH");
+			cell->type = "$not";
+			did_something = true;
+			goto next_cell;
+		}
+
 		if (mux_undef && (cell->type == "$mux" || cell->type == "$pmux")) {
 			RTLIL::SigSpec new_a, new_b, new_s;
 			int width = cell->connections.at("\\A").width;
@@ -392,10 +410,14 @@ struct OptConstPass : public Pass {
 		log("    -mux_undef\n");
 		log("        remove 'undef' inputs from $mux, $pmux and $_MUX_ cells\n");
 		log("\n");
+		log("    -mux_bool\n");
+		log("        replace $mux cells with inverters or buffers when possible\n");
+		log("\n");
 	}
 	virtual void execute(std::vector<std::string> args, RTLIL::Design *design)
 	{
 		bool mux_undef = false;
+		bool mux_bool = false;
 
 		log_header("Executing OPT_CONST pass (perform const folding).\n");
 		log_push();
@@ -406,6 +428,10 @@ struct OptConstPass : public Pass {
 				mux_undef = true;
 				continue;
 			}
+			if (args[argidx] == "-mux_bool") {
+				mux_bool = true;
+				continue;
+			}
 			break;
 		}
 		extra_args(args, argidx, design);
@@ -414,9 +440,9 @@ struct OptConstPass : public Pass {
 			do {
 				do {
 					did_something = false;
-					replace_const_cells(design, mod_it.second, false, mux_undef);
+					replace_const_cells(design, mod_it.second, false, mux_undef, mux_bool);
 				} while (did_something);
-				replace_const_cells(design, mod_it.second, true, mux_undef);
+				replace_const_cells(design, mod_it.second, true, mux_undef, mux_bool);
 			} while (did_something);
 
 		log_pop();
-- 
2.30.2