From c1aa0bde877407d06946a03947e8b96d6bcfdb34 Mon Sep 17 00:00:00 2001
From: Miodrag Milanovic <mmicko@gmail.com>
Date: Mon, 16 Sep 2024 12:35:16 +0200
Subject: [PATCH] Check if output exists

---
 himbaechel/uarch/ng-ultra/pack.cc | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/himbaechel/uarch/ng-ultra/pack.cc b/himbaechel/uarch/ng-ultra/pack.cc
index aa51b47c..cd76e050 100644
--- a/himbaechel/uarch/ng-ultra/pack.cc
+++ b/himbaechel/uarch/ng-ultra/pack.cc
@@ -433,7 +433,8 @@ void NgUltraPacker::pack_dff_chains(void)
         std::vector<CellInfo*> chain;
         CellInfo* start_dff = &ci;
         while(1) {
-            NetInfo *o = dff->getPort(id_O);            
+            NetInfo *o = dff->getPort(id_O);
+            if (!o) break;
             if (o->users.entries() != 1) break;
             dff = (*o->users.begin()).cell;
             if (dff->type == id_NX_DFF && (*o->users.begin()).port == id_I) {