From 5988c92f052a9aee6dac958f8e5c914f5ecb1ca4 Mon Sep 17 00:00:00 2001
From: Matthias Koefferlein <matthias@koefferlein.de>
Date: Fri, 13 Nov 2020 01:19:18 +0100
Subject: [PATCH] Trying to save some (potentially expensive) layout updates on
 'overwrite' cell name conflict resolution.

---
 src/db/db/dbCell.cc         |  6 +++---
 src/db/db/dbCommonReader.cc | 31 ++++++++++++++++++++++++-------
 src/db/db/dbCommonReader.h  |  5 +++++
 3 files changed, 32 insertions(+), 10 deletions(-)

diff --git a/src/db/db/dbCell.cc b/src/db/db/dbCell.cc
index 0b1522e82..4a1adf813 100644
--- a/src/db/db/dbCell.cc
+++ b/src/db/db/dbCell.cc
@@ -506,7 +506,7 @@ Cell::collect_caller_cells (std::set<cell_index_type> &callers, const std::set<c
 {
   if (levels != 0) {
     for (parent_cell_iterator cc = begin_parent_cells (); cc != end_parent_cells (); ++cc) {
-      if (cone.find (*cc) != cone.end () && callers.find (*cc) == callers.end ()) { 
+      if (cone.find (*cc) != cone.end () && callers.find (*cc) == callers.end () && mp_layout->is_valid_cell_index (*cc)) {
         callers.insert (*cc);
         mp_layout->cell (*cc).collect_caller_cells (callers, levels < 0 ? levels : levels - 1);
       }
@@ -519,7 +519,7 @@ Cell::collect_caller_cells (std::set<cell_index_type> &callers, int levels) cons
 {
   if (levels != 0) {
     for (parent_cell_iterator cc = begin_parent_cells (); cc != end_parent_cells (); ++cc) {
-      if (callers.find (*cc) == callers.end ()) { 
+      if (callers.find (*cc) == callers.end () && mp_layout->is_valid_cell_index (*cc)) {
         callers.insert (*cc);
         mp_layout->cell (*cc).collect_caller_cells (callers, levels < 0 ? levels : levels - 1);
       }
@@ -538,7 +538,7 @@ Cell::collect_called_cells (std::set<cell_index_type> &called, int levels) const
 {
   if (levels != 0) {
     for (child_cell_iterator cc = begin_child_cells (); ! cc.at_end (); ++cc) {
-      if (called.find (*cc) == called.end ()) { 
+      if (called.find (*cc) == called.end () && mp_layout->is_valid_cell_index (*cc)) {
         called.insert (*cc);
         mp_layout->cell (*cc).collect_called_cells (called, levels < 0 ? levels : levels - 1);
       }
diff --git a/src/db/db/dbCommonReader.cc b/src/db/db/dbCommonReader.cc
index 741cf1f0d..2d4afc86d 100644
--- a/src/db/db/dbCommonReader.cc
+++ b/src/db/db/dbCommonReader.cc
@@ -237,9 +237,21 @@ CommonReader::merge_cell (db::Layout &layout, db::cell_index_type target_cell_in
 
   //  copy over the instances
   for (db::Cell::const_iterator i = src_cell.begin (); ! i.at_end (); ++i) {
-    target_cell.insert (*i);
+    //  NOTE: cell indexed may be invalid because we delete subcells without update()
+    if (layout.is_valid_cell_index (i->cell_index ())) {
+      target_cell.insert (*i);
+    }
   }
 
+  merge_cell_without_instances (layout, target_cell_index, src_cell_index);
+}
+
+void
+CommonReader::merge_cell_without_instances (db::Layout &layout, db::cell_index_type target_cell_index, db::cell_index_type src_cell_index) const
+{
+  const db::Cell &src_cell = layout.cell (src_cell_index);
+  db::Cell &target_cell = layout.cell (target_cell_index);
+
   //  copy over the shapes
   for (unsigned int l = 0; l < layout.layers (); ++l) {
     if (layout.is_valid_layer (l) && ! src_cell.shapes (l).empty ()) {
@@ -338,11 +350,17 @@ CommonReader::finish (db::Layout &layout)
 
       //  we have a cell conflict
 
-      layout.force_update ();
-
       if (m_cc_resolution == OverwriteCell && ! layout.cell (ci_new).is_ghost_cell ()) {
 
-        layout.prune_subcells (ci_org);
+        if (! layout.cell (ci_org).begin ().at_end ()) {
+
+          //  NOTE: because prune_subcells needs the parents for sub cells and we are going do delete
+          //  the current cell, we cannot save the "update()" just by traversing bottom-up.
+          layout.force_update ();
+          layout.prune_subcells (ci_org);
+
+        }
+
         layout.cell (ci_org).clear_shapes ();
 
         merge_cell (layout, ci_org, ci_new);
@@ -352,9 +370,8 @@ CommonReader::finish (db::Layout &layout)
         layout.prune_subcells (ci_new);
         layout.cell (ci_new).clear_shapes ();
 
-        //  we need the instances of the cell we just cleaned
-        layout.force_update ();
-        merge_cell (layout, ci_org, ci_new);
+        //  NOTE: ignore instances -> this saves us a layout update
+        merge_cell_without_instances (layout, ci_org, ci_new);
 
       } else {
 
diff --git a/src/db/db/dbCommonReader.h b/src/db/db/dbCommonReader.h
index 2bcecfaa7..f0ed56bcf 100644
--- a/src/db/db/dbCommonReader.h
+++ b/src/db/db/dbCommonReader.h
@@ -141,6 +141,11 @@ protected:
    */
   void merge_cell (db::Layout &layout, db::cell_index_type target_cell_index, db::cell_index_type src_cell_index) const;
 
+  /**
+   * @brief Merge (and delete) the src_cell into target_cell without instances
+   */
+  void merge_cell_without_instances (db::Layout &layout, db::cell_index_type target_cell_index, db::cell_index_type src_cell_index) const;
+
 private:
   std::map<size_t, std::pair<std::string, db::cell_index_type> > m_id_map;
   std::map<std::string, std::pair<size_t, db::cell_index_type> > m_name_map;