One more change to the extraction method to avoid extracting the

substrate more than once for the same subcell, since the substrate
extraction method scans the entire plane area;  this was making
large standard cell layouts extract very slowly, as every component
cell was causing the substrate search to be repeated.

extract/ExtSubtree.c

@@ -93,6 +93,26 @@ void extSubtreeAdjustInit();
 void extSubtreeOutputCoupling();
 void extSubtreeHardSearch();
 
+/*
+ * ----------------------------------------------------------------------------
+ *
+ * extClearUseFlags --
+ *
+ *  Callback function to clear the CU_SUB_EXTRACTED flag from each child
+ *  use of a CellDef.
+ *
+ * ----------------------------------------------------------------------------
+ */
+
+int
+extClearUseFlags(use, clientData)
+    CellUse *use;
+    ClientData clientData;
+{
+    use->cu_flags &= ~CU_SUB_EXTRACTED;
+    return 0;
+}
+
 
 /*
  * ----------------------------------------------------------------------------
@@ -292,6 +312,9 @@ done:
     /* Output connections and node adjustments */
     extOutputConns(&ha.ha_connHash, f);
     HashKill(&ha.ha_connHash);
+
+    /* Clear the CU_SUB_EXTRACTED flag from all children instances */
+    DBCellEnum(def, extClearUseFlags, (ClientData)NULL);
 }
 
 #ifdef	exactinteractions
@@ -800,6 +823,8 @@ extSubtreeFunc(scx, ha)
 	    for (y = use->cu_ylo; y <= use->cu_yhi; y++)
 		extHierSubstrate(ha, use, x, y);
     }
+    /* Mark substrate as having been extracted for this use. */
+    use->cu_flags |= CU_SUB_EXTRACTED;
 
     /* Free the cumulative node list we extracted above */
     if (ha->ha_cumFlat.et_nodes)