Make the max slope for high fanout routing a flag.

Signed-off-by: Dustin DeWeese <[email protected]>

Author: HackerFoo

vpr/src/base/SetupVPR.cpp

@@ -373,6 +373,7 @@ static void SetupRouterOpts(const t_options& Options, t_router_opts* RouterOpts)
     RouterOpts->clock_modeling = Options.clock_modeling;
     RouterOpts->two_stage_clock_routing = Options.two_stage_clock_routing;
     RouterOpts->high_fanout_threshold = Options.router_high_fanout_threshold;
+    RouterOpts->high_fanout_max_slope = Options.router_high_fanout_max_slope;
     RouterOpts->router_debug_net = Options.router_debug_net;
     RouterOpts->router_debug_sink_rr = Options.router_debug_sink_rr;
     RouterOpts->router_debug_iteration = Options.router_debug_iteration;

vpr/src/base/read_options.cpp

@@ -1984,6 +1984,13 @@ argparse::ArgumentParser create_arg_parser(std::string prog_name, t_options& arg
         .default_value("64")
         .show_in(argparse::ShowIn::HELP_ONLY);
 
+    route_timing_grp.add_argument<float>(args.router_high_fanout_max_slope, "--router_high_fanout_max_slope")
+        .help(
+            "Maximum routing predictor slope where high fanout routing is enabled.\n"
+            " -1.0 is normal progress, 0 is no progress.")
+        .default_value("-0.5")
+        .show_in(argparse::ShowIn::HELP_ONLY);
+
     route_timing_grp.add_argument<e_router_lookahead, ParseRouterLookahead>(args.router_lookahead_type, "--router_lookahead")
         .help(
             "Controls what lookahead the router uses to calculate cost of completing a connection.\n"

vpr/src/base/read_options.h

@@ -163,6 +163,7 @@ struct t_options {
     argparse::ArgValue<float> congested_routing_iteration_threshold_frac;
     argparse::ArgValue<e_route_bb_update> route_bb_update;
     argparse::ArgValue<int> router_high_fanout_threshold;
+    argparse::ArgValue<float> router_high_fanout_max_slope;
     argparse::ArgValue<int> router_debug_net;
     argparse::ArgValue<int> router_debug_sink_rr;
     argparse::ArgValue<int> router_debug_iteration;

vpr/src/base/vpr_types.h

@@ -1065,6 +1065,7 @@ struct t_router_opts {
     enum e_clock_modeling clock_modeling; ///<How clock pins and nets should be handled
     bool two_stage_clock_routing;         ///<How clock nets on dedicated networks should be routed
     int high_fanout_threshold;
+    float high_fanout_max_slope;
     int router_debug_net;
     int router_debug_sink_rr;
     int router_debug_iteration;

vpr/src/route/route_timing.cpp

@@ -78,7 +78,7 @@ static bool timing_driven_route_sink(
     unsigned itarget,
     int target_pin,
     const t_conn_cost_params cost_params,
-    int high_fanout_threshold,
+    const t_router_opts& router_opts,
     t_rt_node* rt_root,
     t_rt_node** rt_node_of_sink,
     SpatialRouteTreeLookup& spatial_rt_lookup,
@@ -1049,7 +1049,7 @@ bool timing_driven_route_net(ConnectionRouter& router,
                                       itarget,
                                       target_pin,
                                       cost_params,
-                                      router_opts.high_fanout_threshold,
+                                      router_opts,
                                       rt_root, rt_node_of_sink,
                                       spatial_route_tree_lookup,
                                       router_stats,
@@ -1189,7 +1189,7 @@ static bool timing_driven_route_sink(
     unsigned itarget,
     int target_pin,
     const t_conn_cost_params cost_params,
-    int high_fanout_threshold,
+    const t_router_opts& router_opts,
     t_rt_node* rt_root,
     t_rt_node** rt_node_of_sink,
     SpatialRouteTreeLookup& spatial_rt_lookup,
@@ -1215,15 +1215,15 @@ static bool timing_driven_route_sink(
     t_bb bounding_box = route_ctx.route_bb[net_id];
 
     bool net_is_global = cluster_ctx.clb_nlist.net_is_global(net_id);
-    bool high_fanout = is_high_fanout(cluster_ctx.clb_nlist.net_sinks(net_id).size(), high_fanout_threshold);
+    bool high_fanout = is_high_fanout(cluster_ctx.clb_nlist.net_sinks(net_id).size(), router_opts.high_fanout_threshold);
     constexpr float HIGH_FANOUT_CRITICALITY_THRESHOLD = 0.9;
     bool sink_critical = (cost_params.criticality > HIGH_FANOUT_CRITICALITY_THRESHOLD);
     bool net_is_clock = route_ctx.is_clock_net[net_id] != 0;
 
     //We normally route high fanout nets by only adding spatially close-by routing to the heap (reduces run-time).
     //However, if the current sink is 'critical' from a timing perspective, we put the entire route tree back onto
     //the heap to ensure it has more flexibility to find the best path.
-    if (high_fanout && !sink_critical && !net_is_global && !net_is_clock && !(routing_predictor.get_slope() > -0.5)) {
+    if (high_fanout && !sink_critical && !net_is_global && !net_is_clock && !(routing_predictor.get_slope() > router_opts.high_fanout_max_slope)) {
         std::tie(found_path, cheapest) = router.timing_driven_route_connection_from_route_tree_high_fanout(rt_root,
                                                                                                            sink_node,
                                                                                                            cost_params,