From b470c480e97fe112810d04a6051d1029ce1e8c29 Mon Sep 17 00:00:00 2001
From: Clifford Wolf <clifford@clifford.at>
Date: Mon, 15 Sep 2014 12:22:03 +0200
Subject: [PATCH] Added the obvious optimizations to alumacc $macc generator

---
 kernel/macc.h             | 60 +++++++++++++++++++++++++++++++++++++++
 passes/techmap/alumacc.cc |  1 +
 2 files changed, 61 insertions(+)

diff --git a/kernel/macc.h b/kernel/macc.h
index 362acab29..271141112 100644
--- a/kernel/macc.h
+++ b/kernel/macc.h
@@ -34,6 +34,66 @@ struct Macc
 	std::vector<port_t> ports;
 	RTLIL::SigSpec bit_ports;
 
+	void optimize(int width)
+	{
+		std::vector<port_t> new_ports;
+		RTLIL::SigSpec new_bit_ports;
+		RTLIL::Const off(0, width);
+
+		for (auto &port : ports)
+		{
+			if (SIZE(port.in_a) == 0 && SIZE(port.in_b) == 0)
+				continue;
+
+			if (SIZE(port.in_a) == 1 && SIZE(port.in_b) == 0 && !port.is_signed && !port.do_subtract) {
+				bit_ports.append(port.in_a);
+				continue;
+			}
+
+			if (port.in_a.is_fully_const() && port.in_b.is_fully_const()) {
+				RTLIL::Const v = port.in_a.as_const();
+				if (SIZE(port.in_b))
+					v = const_mul(v, port.in_b.as_const(), port.is_signed, port.is_signed, width);
+				if (port.do_subtract)
+					off = const_sub(off, v, port.is_signed, port.is_signed, width);
+				else
+					off = const_add(off, v, port.is_signed, port.is_signed, width);
+				continue;
+			}
+
+			if (port.is_signed) {
+				while (SIZE(port.in_a) > 1 && port.in_a[SIZE(port.in_a)-1] == port.in_a[SIZE(port.in_a)-2])
+					port.in_a.remove(SIZE(port.in_a)-1);
+				while (SIZE(port.in_b) > 1 && port.in_b[SIZE(port.in_b)-1] == port.in_b[SIZE(port.in_b)-2])
+					port.in_b.remove(SIZE(port.in_b)-1);
+			} else {
+				while (SIZE(port.in_a) > 1 && port.in_a[SIZE(port.in_a)-1] == RTLIL::S0)
+					port.in_a.remove(SIZE(port.in_a)-1);
+				while (SIZE(port.in_b) > 1 && port.in_b[SIZE(port.in_b)-1] == RTLIL::S0)
+					port.in_b.remove(SIZE(port.in_b)-1);
+			}
+
+			new_ports.push_back(port);
+		}
+
+		for (auto &bit : bit_ports)
+			if (bit == RTLIL::S1)
+				off = const_add(off, RTLIL::Const(1, width), false, false, width);
+			else if (bit != RTLIL::S0)
+				new_bit_ports.append(bit);
+
+		if (off.as_bool()) {
+			port_t port;
+			port.in_a = off;
+			port.is_signed = false;
+			port.do_subtract = false;
+			new_ports.push_back(port);
+		}
+
+		new_ports.swap(ports);
+		bit_ports = new_bit_ports;
+	}
+
 	void from_cell(RTLIL::Cell *cell)
 	{
 		RTLIL::SigSpec port_a = cell->getPort("\\A");
diff --git a/passes/techmap/alumacc.cc b/passes/techmap/alumacc.cc
index 3fddcef13..c52e0e4ca 100644
--- a/passes/techmap/alumacc.cc
+++ b/passes/techmap/alumacc.cc
@@ -317,6 +317,7 @@ struct AlumaccWorker
 
 			log("  creating $macc cell for %s: %s\n", log_id(n->cell), log_id(cell));
 
+			n->macc.optimize(SIZE(n->y));
 			n->macc.to_cell(cell);
 			cell->setPort("\\Y", n->y);
 			cell->fixup_parameters();
-- 
2.30.2