Implement a simple prefetch loop.

Signed-off-by: Keith Rothman <[email protected]>

Author: litghost

vpr/src/route/route_timing.cpp

@@ -1960,6 +1960,16 @@ void Router::timing_driven_expand_neighbours(t_heap* current,
     RREdgeId first_edge = rr_nodes_->first_edge(from_node);
     RREdgeId last_edge = rr_nodes_->last_edge(from_node);
     int num_edges = size_t(last_edge) - size_t(first_edge);
+    for (int iconn = 0; iconn < num_edges; iconn++) {
+        RREdgeId from_edge(size_t(first_edge) + iconn);
+
+        RRNodeId to_node = rr_nodes_->edge_sink_node(from_edge);
+        rr_nodes_->prefetch_node(to_node);
+
+        int switch_idx = rr_nodes_->edge_switch(from_edge);
+        __builtin_prefetch(&rr_switch_inf_[switch_idx], 0, 0);
+    }
+
     for (int iconn = 0; iconn < num_edges; iconn++) {
         RREdgeId from_edge(size_t(first_edge) + iconn);
         RRNodeId to_node = rr_nodes_->edge_sink_node(from_edge);

vpr/src/route/route_timing.h

@@ -64,11 +64,11 @@ class Router {
         }
     }
 
-    void update_cheapest(t_heap* cheapest) {
+    inline void update_cheapest(t_heap* cheapest) {
         update_cheapest(cheapest, &rr_node_route_inf_[cheapest->index]);
     }
 
-    void update_cheapest(t_heap* cheapest, t_rr_node_route_inf* route_inf) {
+    inline void update_cheapest(t_heap* cheapest, t_rr_node_route_inf* route_inf) {
         //Record final link to target
         add_to_mod_list(cheapest->index);
 

vpr/src/route/rr_graph_storage.h

@@ -216,6 +216,10 @@ class t_rr_graph_storage {
     short node_track_num(RRNodeId id) const; //Same as ptc_num() but checks that type() is consistent
     short node_class_num(RRNodeId id) const; //Same as ptc_num() but checks that type() is consistent
 
+    inline void prefetch_node(RRNodeId id) const {
+        __builtin_prefetch(&storage_[id], 0, 0);
+    }
+
     /****************
      * Edge methods *
      ****************/