equivalent tiles: added documentation

Signed-off-by: Alessandro Comodi <[email protected]>

Author: acomodi

vpr/src/base/clustered_netlist.h

@@ -126,13 +126,21 @@ class ClusteredNetlist : public Netlist<ClusterBlockId, ClusterPortId, ClusterPi
         //Returns the physical block
         t_pb* block_pb(const ClusterBlockId id) const;
 
-        //Returns the type of CLB (Logic block, RAM, DSP, etc.). Calls block_type with boolean set to true.
+        /*
+         * Returns the type of CLB (Logic block, RAM, DSP, etc.). There are two different overloaded block_type functions
+         * 1) The first one (without the boolean) is used to retrieve the actual physical type corresponding to the placed
+         *    block. This function will call the one with the boolean, setting `get_equivalent_if_set` to true.
+         * 2) The second one (with the boolean) is used to retrieve the physical or logical type relative to a block.
+         *    Depending on the value of `get_equivalent_if_set` we will get a different block_type:
+         *        - True: the function returns the physical placed tile (can be an equivalent tile) of the block;
+         *        - False: the function returns the logical tile of the block (even if it was placed in an equivalent tile).
+         */
         t_type_ptr block_type(const ClusterBlockId id) const;
-
-        //Returns the type of CLB. If get_equivalent_if_set is true, if the equivalent tile has been chosen it returns it.
         t_type_ptr block_type(const ClusterBlockId id, bool get_equivalent_if_set) const;
 
         //Returns the equivalent type index (if any) of a CLB
+        //The index is used to retrieve the equivalent type from the t_type_descriptor structure
+        //Example: type->equivalent_tiles[index]
         int block_eq_type_index(const ClusterBlockId id) const;
 
         //Returns the net of the block attached to the specific pin index
@@ -182,7 +190,8 @@ class ClusteredNetlist : public Netlist<ClusterBlockId, ClusterPortId, ClusterPi
         //  t_type_ptr  : The type of the CLB
         ClusterBlockId create_block(const char *name, t_pb* pb, t_type_ptr type);
 
-        //Add the equivalent block type for a CLB
+        //Add the equivalent block type for a CLB. This mutator adds both the equivalent type index and
+        //the equivalent type to the corresponding vector_maps
         //  blk_id      : The block placed in an equivalent tile location
         //  i_eq_type   : The index used to retrieve the equivalent tile from the t_type_ptr structure
         //  eq_type     : The equivalent type associated with this block