From bcd802718256efbacaf0a73f99347af40b61e464 Mon Sep 17 00:00:00 2001
From: Eddie Hung <eddie@fpgeh.com>
Date: Fri, 19 Jul 2019 13:11:48 -0700
Subject: [PATCH] Also optimise MSB of $sub

---
 passes/opt/wreduce.cc | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/passes/opt/wreduce.cc b/passes/opt/wreduce.cc
index e8c2cb726..dff1c5370 100644
--- a/passes/opt/wreduce.cc
+++ b/passes/opt/wreduce.cc
@@ -342,9 +342,9 @@ struct WreduceWorker
 			}
 		}
 
-		if (cell->type.in("$pos", "$add", "$mul", "$and", "$or", "$xor"))
+		if (cell->type.in("$pos", "$add", "$mul", "$and", "$or", "$xor", "$sub"))
 		{
-			bool is_signed = cell->getParam("\\A_SIGNED").as_bool();
+			bool is_signed = cell->getParam("\\A_SIGNED").as_bool() || cell->type == "$sub";
 
 			int a_size = 0, b_size = 0;
 			if (cell->hasPort("\\A")) a_size = GetSize(cell->getPort("\\A"));
@@ -352,7 +352,7 @@ struct WreduceWorker
 
 			int max_y_size = max(a_size, b_size);
 
-			if (cell->type == "$add")
+			if (cell->type.in("$add", "$sub"))
 				max_y_size++;
 
 			if (cell->type == "$mul")
-- 
2.30.2