Enhancing 'blend-mode' 0 (buddy tools) such that it will not generate instance duplicates

src/buddies/src/bd/bdReaderOptions.cc

@@ -197,10 +197,13 @@ GenericReaderOptions::add_options (tl::CommandLineOptions &cmd)
                     "--" + m_long_prefix + "blend-mode=mode", &m_cell_conflict_resolution, "Specifies how cell conflicts are resolved when using file concatenation",
                     "When concatenating files with '+', the reader will handle cells with identical names according to this mode:\n"
                     "\n"
-                    "* 0: joins everything (unsafe)\n"
+                    "* 0: joins everything (usually unsafe)\n"
                     "* 1: overwrite\n"
                     "* 2: skip new cell\n"
-                    "* 3: rename cell (safe, default)"
+                    "* 3: rename cell (safe, default)\n"
+                    "\n"
+                    "Mode 0 is a safe solution for the 'same hierarchy, different layers' case. Mode 3 is a safe solution for "
+                    "joining multiple files into one and combining the hierarchy tree of all files as distinct separate trees.\n"
                    )
       ;
   }

src/db/db/dbCommonReader.cc

@@ -245,10 +245,16 @@ CommonReaderBase::merge_cell (db::Layout &layout, db::cell_index_type target_cel
   db::Cell &target_cell = layout.cell (target_cell_index);
   target_cell.set_ghost_cell (src_cell.is_ghost_cell () && target_cell.is_ghost_cell ());
 
+  //  avoid generating duplicates
+  std::set<db::Instance, db::InstanceCompareFunction> current;
+  for (db::Cell::const_iterator i = target_cell.begin (); ! i.at_end (); ++i) {
+    current.insert (*i);
+  }
+
   //  copy over the instances
   for (db::Cell::const_iterator i = src_cell.begin (); ! i.at_end (); ++i) {
     //  NOTE: cell indexed may be invalid because we delete subcells without update()
-    if (layout.is_valid_cell_index (i->cell_index ())) {
+    if (layout.is_valid_cell_index (i->cell_index ()) && current.find (*i) == current.end ()) {
       target_cell.insert (*i);
     }
   }

src/db/db/dbInstances.h

@@ -1977,7 +1977,20 @@ OverlappingInstanceIteratorTraits::instance_from_stable_iter (const Iter &iter)
   //  box tree iterators deliver pointers, not iterators. Use instance_from_pointer to do this conversion.
   return mp_insts->instance_from_pointer (&*iter);
 }
- 
+
+/**
+ *  @brief A compare function for db::Instance that uses "less" for value compare
+ *
+ *  In contrast, "operator<" will compare the instance reference, not value.
+ */
+struct InstanceCompareFunction
+{
+  bool operator() (const db::Instance &a, const db::Instance &b) const
+  {
+    return a.less (b);
+  }
+};
+
 }
 
 #endif