From e9845e534a79f8b3f4fce3b8063ea4c76ece64ea Mon Sep 17 00:00:00 2001
From: MyskYko <yoyuohlhjl@yahoo.co.jp>
Date: Tue, 17 Jun 2025 16:41:32 -0700
Subject: [PATCH] fix a bug when yosys constants are already declared

---
 src/base/abc/abcNtk.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/base/abc/abcNtk.c b/src/base/abc/abcNtk.c
index 1b823cf00..9d6c4f0ea 100644
--- a/src/base/abc/abcNtk.c
+++ b/src/base/abc/abcNtk.c
@@ -1565,19 +1565,19 @@ void Abc_NtkFixNonDrivenNets( Abc_Ntk_t * pNtk )
 
     // special case
     pNet = Abc_NtkFindNet( pNtk, "$false" );
-    if ( pNet != NULL )
+    if ( pNet != NULL && !Abc_ObjFaninNum(pNet) )
     {
         pNode = Abc_NtkCreateNodeConst0( pNtk );
         Abc_ObjAddFanin( pNet, pNode );
     }
     pNet = Abc_NtkFindNet( pNtk, "$undef" );
-    if ( pNet != NULL )
+    if ( pNet != NULL && !Abc_ObjFaninNum(pNet) )
     {
         pNode = Abc_NtkCreateNodeConst0( pNtk );
         Abc_ObjAddFanin( pNet, pNode );
     }
     pNet = Abc_NtkFindNet( pNtk, "$true" );
-    if ( pNet != NULL )
+    if ( pNet != NULL && !Abc_ObjFaninNum(pNet) )
     {
         pNode = Abc_NtkCreateNodeConst1( pNtk );
         Abc_ObjAddFanin( pNet, pNode );