From 06386bee1bf3899d9758946743b2752400f6bbea Mon Sep 17 00:00:00 2001
From: Tim Edwards <tim@opencircuitdesign.com>
Date: Tue, 25 Oct 2022 20:14:44 -0400
Subject: [PATCH] Corrected an issue with "flatten":  If a cell has
 disconnected ports, then flattening instances of that cell can cause a port
 of the parent cell connected to the disconnected port of the child cell to
 itself become disconnected.  If the parent port is not changed to show the
 disconnected state, then pin mismatch can occur if the netlist being matched
 didn't have the same flattened subcell.  This condition is now detected and
 handled correctly.

---
 VERSION        |  2 +-
 base/flatten.c | 41 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 42 insertions(+), 1 deletion(-)

diff --git a/VERSION b/VERSION
index 476edb5..f876ffa 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-1.5.235
+1.5.236
diff --git a/base/flatten.c b/base/flatten.c
index ad6516e..1fb83ba 100644
--- a/base/flatten.c
+++ b/base/flatten.c
@@ -243,6 +243,13 @@ void flattenCell(char *name, int file)
   ThisCell->dumped = 1;		/* indicate cell has been flattened */
 }
 
+/* Structure used to keep track of nodes needing checking */
+
+struct linkednode {
+    int node;
+    struct linkednode *next;
+};
+
 /*--------------------------------------------------------------*/
 /* flattenInstancesOf --					*/
 /*								*/
@@ -265,6 +272,7 @@ int flattenInstancesOf(char *name, int fnum, char *instance)
   struct nlist *ThisCell;
   struct  nlist *ChildCell;
   struct objlist *tmp, *ob2, *ob3;
+  struct linkednode *checknodes = NULL, *newlnode, *chknode;
   int	notdone, rnodenum;
   char	tmpstr[1024];
   int	nextnode, oldmax, numflat = 0;
@@ -416,6 +424,16 @@ int flattenInstancesOf(char *name, int fnum, char *instance)
 	          }
 	          UpdateNodeNumbers(ChildStart, tmp->node, ob2->node);
 	     }
+	     else if (tmp->node == -1) {
+		 /* Opposite case:  If child port is an unconnected node, then	*/
+		 /* removing the instance may make the parent node become	*/
+		 /* unconnected.  For now, just record the node number.  At the	*/
+		 /* end we'll check if these nodes are actually disconnected.	*/
+		 newlnode = (struct linkednode *)MALLOC(sizeof(struct linkednode));
+		 newlnode->node = ob2->node;
+		 newlnode->next = checknodes;
+		 checknodes = newlnode;
+	     }
 
 	     /* in pathological cases, the lengths of the port lists may
               * change.  This is an error, but that is no reason to allow
@@ -598,6 +616,29 @@ int flattenInstancesOf(char *name, int fnum, char *instance)
       NextObj = ParentParams;
     }				/* repeat until no more instances found */
   }
+
+  /* Check nodes that may have become disconnected after child flattening */
+  while (checknodes != NULL) {
+     struct objlist *portnode = NULL;
+
+     chknode = checknodes;
+     checknodes = checknodes->next;
+
+     for (ob3 = ThisCell->cell; ob3; ob3 = ob3->next) {
+	if ((ob3->type != PORT) && (portnode == NULL))
+	   break;
+	else if ((ob3->type == PORT) && (ob3->node == chknode->node))
+	   portnode = ob3;
+	else if ((ob3->type >= FIRSTPIN) && (ob3->node == chknode->node))
+	   break;
+     }
+     if ((ob3 == NULL) && (portnode != NULL)) {
+        /* Port became disconnected when child was flattened */
+        portnode->node = -1;
+     }
+     FREE(chknode);
+  }
+
   CacheNodeNames(ThisCell);
   ThisCell->dumped = 1;		/* indicate cell has been flattened */
   return numflat;