From c3e779a65f285afa123b990f3a717a7ae8e028f5 Mon Sep 17 00:00:00 2001
From: Clifford Wolf <clifford@clifford.at>
Date: Fri, 3 Oct 2014 10:12:28 +0200
Subject: Added $_BUF_ cell type

---
 kernel/celltypes.h         |  3 +++
 kernel/rtlil.cc            |  1 +
 passes/abc/abc.cc          | 10 +++++++---
 passes/opt/opt_clean.cc    |  4 ++--
 techlibs/common/simcells.v |  6 ++++++
 5 files changed, 19 insertions(+), 5 deletions(-)

diff --git a/kernel/celltypes.h b/kernel/celltypes.h
index 85c21ef3..2774073d 100644
--- a/kernel/celltypes.h
+++ b/kernel/celltypes.h
@@ -130,6 +130,7 @@ struct CellTypes
 
 	void setup_stdcells()
 	{
+		setup_type("$_BUF_", {"\\A"}, {"\\Y"}, true);
 		setup_type("$_NOT_", {"\\A"}, {"\\Y"}, true);
 		setup_type("$_AND_", {"\\A", "\\B"}, {"\\Y"}, true);
 		setup_type("$_NAND_", {"\\A", "\\B"}, {"\\Y"}, true);
@@ -261,6 +262,8 @@ struct CellTypes
 		HANDLE_CELL_TYPE(neg)
 #undef HANDLE_CELL_TYPE
 
+		if (type == "$_BUF_")
+			return arg1;
 		if (type == "$_NOT_")
 			return eval_not(arg1);
 		if (type == "$_AND_")
diff --git a/kernel/rtlil.cc b/kernel/rtlil.cc
index 00be796f..89132ea2 100644
--- a/kernel/rtlil.cc
+++ b/kernel/rtlil.cc
@@ -870,6 +870,7 @@ namespace {
 				return;
 			}
 
+			if (cell->type == "$_BUF_")  { check_gate("AY"); return; }
 			if (cell->type == "$_NOT_")  { check_gate("AY"); return; }
 			if (cell->type == "$_AND_")  { check_gate("ABY"); return; }
 			if (cell->type == "$_NAND_") { check_gate("ABY"); return; }
diff --git a/passes/abc/abc.cc b/passes/abc/abc.cc
index 1a7de066..3e105411 100644
--- a/passes/abc/abc.cc
+++ b/passes/abc/abc.cc
@@ -59,6 +59,7 @@ PRIVATE_NAMESPACE_BEGIN
 enum class gate_type_t {
 	G_NONE,
 	G_FF,
+	G_BUF,
 	G_NOT,
 	G_AND,
 	G_NAND,
@@ -160,7 +161,7 @@ static void extract_cell(RTLIL::Cell *cell, bool keepff)
 		return;
 	}
 
-	if (cell->type == "$_NOT_")
+	if (cell->type.in("$_BUF_", "$_NOT_"))
 	{
 		RTLIL::SigSpec sig_a = cell->getPort("\\A");
 		RTLIL::SigSpec sig_y = cell->getPort("\\Y");
@@ -168,7 +169,7 @@ static void extract_cell(RTLIL::Cell *cell, bool keepff)
 		assign_map.apply(sig_a);
 		assign_map.apply(sig_y);
 
-		map_signal(sig_y, G(NOT), map_signal(sig_a));
+		map_signal(sig_y, cell->type == "$_BUF_" ? G(BUF) : G(NOT), map_signal(sig_a));
 
 		module->remove(cell);
 		return;
@@ -645,7 +646,10 @@ static void abc_module(RTLIL::Design *design, RTLIL::Module *current_module, std
 
 	int count_gates = 0;
 	for (auto &si : signal_list) {
-		if (si.type == G(NOT)) {
+		if (si.type == G(BUF)) {
+			fprintf(f, ".names n%d n%d\n", si.in1, si.id);
+			fprintf(f, "1 1\n");
+		} else if (si.type == G(NOT)) {
 			fprintf(f, ".names n%d n%d\n", si.in1, si.id);
 			fprintf(f, "0 1\n");
 		} else if (si.type == G(AND)) {
diff --git a/passes/opt/opt_clean.cc b/passes/opt/opt_clean.cc
index 15bbf54e..004a2078 100644
--- a/passes/opt/opt_clean.cc
+++ b/passes/opt/opt_clean.cc
@@ -295,8 +295,8 @@ void rmunused_module(RTLIL::Module *module, bool purge_mode, bool verbose)
 
 	std::vector<RTLIL::Cell*> delcells;
 	for (auto cell : module->cells())
-		if (cell->type == "$pos") {
-			bool is_signed = cell->getParam("\\A_SIGNED").as_bool();
+		if (cell->type.in("$pos", "$_BUF_")) {
+			bool is_signed = cell->type == "$pos" && cell->getParam("\\A_SIGNED").as_bool();
 			RTLIL::SigSpec a = cell->getPort("\\A");
 			RTLIL::SigSpec y = cell->getPort("\\Y");
 			a.extend_u0(SIZE(y), is_signed);
diff --git a/techlibs/common/simcells.v b/techlibs/common/simcells.v
index a2a37735..88566411 100644
--- a/techlibs/common/simcells.v
+++ b/techlibs/common/simcells.v
@@ -25,6 +25,12 @@
  *
  */
 
+module  \$_BUF_ (A, Y);
+input A;
+output Y;
+assign Y = A;
+endmodule
+
 module  \$_NOT_ (A, Y);
 input A;
 output Y;
-- 
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