dpl: add API to get adjacent cells cluster

src/dpl/include/dpl/Opendp.h

@@ -163,6 +163,12 @@ class Opendp
   void addDecapMaster(dbMaster* decap_master, double decap_cap);
   void insertDecapCells(double target, IRDropByPoint& psm_ir_drops);
 
+  // Get the instance adjacent to the left or right of a given instance
+  dbInst* getAdjacentInstance(dbInst* inst, bool left) const;
+
+  // Find a cluster of instances that are touching each other
+  std::vector<dbInst*> getAdjacentInstancesCluster(dbInst* inst) const;
+
  private:
   using bgPoint
       = boost::geometry::model::d2::point_xy<int,

src/dpl/src/Opendp.cpp

@@ -377,6 +377,54 @@ void Opendp::groupInitPixels2()
   }
 }
 
+dbInst* Opendp::getAdjacentInstance(dbInst* inst, bool left) const
+{
+  const Rect core = grid_->getCore();
+  const Rect inst_rect = inst->getBBox()->getBox();
+  DbuX x_dbu = left ? DbuX{inst_rect.xMin() - 1} : DbuX{inst_rect.xMax() + 1};
+  x_dbu -= core.xMin();
+  GridX x = grid_->gridX(x_dbu);
+
+  GridY y = grid_->gridSnapDownY(DbuY{inst_rect.yMin() - core.yMin()});
+
+  Pixel* pixel = grid_->gridPixel(x, y);
+
+  dbInst* adjacent_inst = nullptr;
+
+  // do not return macros, endcaps and tapcells
+  if (pixel != nullptr && pixel->cell && pixel->cell->db_inst_->isCore()) {
+    adjacent_inst = pixel->cell->db_inst_;
+  }
+
+  return adjacent_inst;
+}
+
+std::vector<dbInst*> Opendp::getAdjacentInstancesCluster(dbInst* inst) const
+{
+  const bool left = true;
+  const bool right = false;
+  std::vector<dbInst*> adj_inst_cluster;
+
+  dbInst* left_inst = getAdjacentInstance(inst, left);
+  while (left_inst != nullptr) {
+    adj_inst_cluster.push_back(left_inst);
+    // the right instance can be ignored, since it was added in the line above
+    left_inst = getAdjacentInstance(left_inst, left);
+  }
+
+  std::reverse(adj_inst_cluster.begin(), adj_inst_cluster.end());
+  adj_inst_cluster.push_back(inst);
+
+  dbInst* right_inst = getAdjacentInstance(inst, right);
+  while (right_inst != nullptr) {
+    adj_inst_cluster.push_back(right_inst);
+    // the left instance can be ignored, since it was added in the line above
+    right_inst = getAdjacentInstance(right_inst, right);
+  }
+
+  return adj_inst_cluster;
+}
+
 /* static */
 bool Opendp::isInside(const Rect& cell, const Rect& box)
 {