From 73c5be9308f73a6363a926cab771cea5d6f0ad0b Mon Sep 17 00:00:00 2001
From: Alessandro Comodi <acomodi@antmicro.com>
Date: Fri, 13 Nov 2020 13:15:59 +0100
Subject: [PATCH] rr_graph_util: add get fan-in lists function

Signed-off-by: Alessandro Comodi <acomodi@antmicro.com>
---
 vpr/src/route/rr_graph_util.cpp | 17 +++++++++++++++++
 vpr/src/route/rr_graph_util.h   |  6 ++++++
 2 files changed, 23 insertions(+)

diff --git a/vpr/src/route/rr_graph_util.cpp b/vpr/src/route/rr_graph_util.cpp
index 9c7f5ef1488..c8b425182c3 100644
--- a/vpr/src/route/rr_graph_util.cpp
+++ b/vpr/src/route/rr_graph_util.cpp
@@ -177,3 +177,20 @@ void reorder_rr_graph_nodes(const t_router_opts& router_opts) {
                                std::get<2>(edge));
     });
 }
+
+vtr::vector<RRNodeId, std::vector<RREdgeId>> get_fan_in_list() {
+    auto& rr_nodes = g_vpr_ctx.device().rr_nodes;
+
+    vtr::vector<RRNodeId, std::vector<RREdgeId>> node_fan_in_list;
+
+    node_fan_in_list.resize(rr_nodes.size(), std::vector<RREdgeId>(0));
+    node_fan_in_list.shrink_to_fit();
+
+    //Walk the graph and increment fanin on all dwnstream nodes
+    rr_nodes.for_each_edge(
+        [&](RREdgeId edge, __attribute__((unused)) RRNodeId src, RRNodeId sink) {
+            node_fan_in_list[sink].push_back(edge);
+        });
+
+    return node_fan_in_list;
+}
diff --git a/vpr/src/route/rr_graph_util.h b/vpr/src/route/rr_graph_util.h
index e890db2f053..514f396f0d2 100644
--- a/vpr/src/route/rr_graph_util.h
+++ b/vpr/src/route/rr_graph_util.h
@@ -1,10 +1,16 @@
 #ifndef RR_GRAPH_UTIL_H
 #define RR_GRAPH_UTIL_H
 
+#include "vpr_types.h"
+
 int seg_index_of_cblock(t_rr_type from_rr_type, int to_node);
 
 int seg_index_of_sblock(int from_node, int to_node);
 
 void reorder_rr_graph_nodes(const t_router_opts& router_opts);
 
+// This function generates and returns a vector indexed by RRNodeId
+// containing a list of fan-in edges for each node.
+vtr::vector<RRNodeId, std::vector<RREdgeId>> get_fan_in_list();
+
 #endif