add doxygen comments for load_block_rr_indices()

Author: soheilshahrouz

libs/librrgraph/src/base/rr_spatial_lookup.cpp

@@ -338,7 +338,7 @@ void RRSpatialLookup::resize_nodes(int layer,
         || (x >= int(rr_node_indices_[type].dim_size(1)))
         || (y >= int(rr_node_indices_[type].dim_size(2)))
         || (size_t(side) >= rr_node_indices_[type].dim_size(3))) {
-        rr_node_indices_[type].resize({std::max(rr_node_indices_[type].dim_size(0),size_t(layer)+1),
+        rr_node_indices_[type].resize({std::max(rr_node_indices_[type].dim_size(0), size_t(layer)+1),
                                        std::max(rr_node_indices_[type].dim_size(1), size_t(x) + 1),
                                        std::max(rr_node_indices_[type].dim_size(2), size_t(y) + 1),
                                        std::max(rr_node_indices_[type].dim_size(3), size_t(side) + 1)});

vpr/src/route/rr_graph2.cpp

@@ -33,6 +33,18 @@ static void load_chan_rr_indices(const int max_chan_width,
                                  RRGraphBuilder& rr_graph_builder,
                                  int* index);
 
+/**
+ * @brief Assigns and loads rr_node indices for block-level routing resources (SOURCE, SINK, IPIN, OPIN).
+ *
+ * This function walks through the device grid and assigns unique rr_node indices to the routing resources
+ * associated with each block (tiles).
+ *
+ * For SINKs and SOURCEs, it uses side 0 by convention (since they have no geometric side). For IPINs and OPINs,
+ * it determines the correct sides based on the tile's position in the grid, following special rules for
+ * edge and corner tiles.
+ *
+ * The index counter is passed and updated as rr_nodes are added.
+ */
 static void load_block_rr_indices(RRGraphBuilder& rr_graph_builder,
                                   const DeviceGrid& grid,
                                   int* index,
@@ -1347,6 +1359,7 @@ static void load_block_rr_indices(RRGraphBuilder& rr_graph_builder,
         }
     }
 }
+
 static void add_pins_spatial_lookup(RRGraphBuilder& rr_graph_builder,
                                     t_physical_tile_type_ptr physical_type_ptr,
                                     const std::vector<int>& pin_num_vec,