Avoid copying ManyToMany table results (#5923)

Regardless of any copy elision on the returned pair value, the
duration and distance results are always copied.

Fix this by passing rvalue references to std::make_pair.

Author: mjjbell

CHANGELOG.md

@@ -4,6 +4,8 @@
       - ADDED: Added support for multiple via-way restrictions. [#5907](https://github.com/Project-OSRM/osrm-backend/pull/5907)
       - ADDED: Add node bindings support for Node 12, 14, and publish binaries [#5918](https://github.com/Project-OSRM/osrm-backend/pull/5918)
       - REMOVED: we no longer publish Node 8 binary modules (they are still buildable from source) [#5918](https://github.com/Project-OSRM/osrm-backend/pull/5918)
+    - Routing:
+      - FIXED: Avoid copying ManyToMany table results [#5923](https://github.com/Project-OSRM/osrm-backend/pull/5923)
     - Misc:
       - CHANGED: Unify `.osrm.turn_penalites_index` dump processing same with `.osrm.turn_weight_penalties` and `.osrm.turn_duration_penalties` [#5868](https://github.com/Project-OSRM/osrm-backend/pull/5868)
     - Profile:

src/engine/routing_algorithms/many_to_many_ch.cpp

@@ -248,7 +248,7 @@ manyToManySearch(SearchEngineData<ch::Algorithm> &engine_working_data,
         }
     }
 
-    return std::make_pair(durations_table, distances_table);
+    return std::make_pair(std::move(durations_table), std::move(distances_table));
 }
 
 } // namespace routing_algorithms

src/engine/routing_algorithms/many_to_many_mld.cpp

@@ -219,8 +219,8 @@ oneToManySearch(SearchEngineData<Algorithm> &engine_working_data,
                 const std::vector<std::size_t> &phantom_indices,
                 const bool calculate_distance)
 {
-    std::vector<EdgeWeight> weights(phantom_indices.size(), INVALID_EDGE_WEIGHT);
-    std::vector<EdgeDuration> durations(phantom_indices.size(), MAXIMAL_EDGE_DURATION);
+    std::vector<EdgeWeight> weights_table(phantom_indices.size(), INVALID_EDGE_WEIGHT);
+    std::vector<EdgeDuration> durations_table(phantom_indices.size(), MAXIMAL_EDGE_DURATION);
     std::vector<EdgeDistance> distances_table(calculate_distance ? phantom_indices.size() : 0,
                                               MAXIMAL_EDGE_DISTANCE);
     std::vector<NodeID> middle_nodes_table(phantom_indices.size(), SPECIAL_NODEID);
@@ -298,10 +298,10 @@ oneToManySearch(SearchEngineData<Algorithm> &engine_working_data,
                         distances_table.empty() ? nulldistance : distances_table[index];
 
                     if (std::tie(path_weight, path_duration, path_distance) <
-                        std::tie(weights[index], durations[index], current_distance))
+                        std::tie(weights_table[index], durations_table[index], current_distance))
                     {
-                        weights[index] = path_weight;
-                        durations[index] = path_duration;
+                        weights_table[index] = path_weight;
+                        durations_table[index] = path_duration;
                         current_distance = path_distance;
                         middle_nodes_table[index] = node;
                     }
@@ -392,7 +392,7 @@ oneToManySearch(SearchEngineData<Algorithm> &engine_working_data,
             facade, heapNode, query_heap, phantom_nodes, phantom_index, phantom_indices);
     }
 
-    return std::make_pair(durations, distances_table);
+    return std::make_pair(std::move(durations_table), std::move(distances_table));
 }
 
 //
@@ -601,7 +601,7 @@ manyToManySearch(SearchEngineData<Algorithm> &engine_working_data,
         }
     }
 
-    return std::make_pair(durations_table, distances_table);
+    return std::make_pair(std::move(durations_table), std::move(distances_table));
 }
 
 } // namespace mld