Unfurl comments for clangformat

common/timing.cc

@@ -60,14 +60,11 @@ struct Timing
     {
         const auto clk_period = delay_t(1.0e12 / ctx->target_freq);
 
-        // First, compute the topographical order of nets to walk through
+        // First, compute the topographical order of nets to walk through the circuit, assuming it is a _acyclic_ graph
-        //   the circuit, assuming it is a _acyclic_ graph
+        // TODO(eddieh): Handle the case where it is cyclic, e.g. combinatorial loops
-        //   TODO(eddieh): Handle the case where it is cyclic, e.g. combinatorial
-        // loops
         std::vector<NetInfo *> topographical_order;
         std::unordered_map<const NetInfo *, TimingData> net_data;
-        // In lieu of deleting edges from the graph, simply count
+        // In lieu of deleting edges from the graph, simply count the number of fanins to each output port
-        //   the number of fanins to each output port
         std::unordered_map<const PortInfo *, unsigned> port_fanin;
 
         std::vector<IdString> input_ports;
@@ -87,8 +84,7 @@ struct Timing
             for (auto o : output_ports) {
                 IdString clockPort;
                 TimingPortClass portClass = ctx->getPortTimingClass(cell.second.get(), o->name, clockPort);
-                // If output port is influenced by a clock (e.g. FF output)
+                // If output port is influenced by a clock (e.g. FF output) then add it to the ordering as a timing start-point
-                //   then add it to the ordering as a timing start-point
                 if (portClass == TMG_REGISTER_OUTPUT) {
                     DelayInfo clkToQ;
                     ctx->getCellDelay(cell.second.get(), clockPort, o->name, clkToQ);
@@ -100,9 +96,7 @@ struct Timing
                         topographical_order.emplace_back(o->net);
                         net_data.emplace(o->net, TimingData{});
                     }
-                    // Otherwise, for all driven input ports on this cell,
+                    // Otherwise, for all driven input ports on this cell, if a timing arc exists between the input and the current output port, increment fanin counter
-                    //   if a timing arc exists between the input and
-                    //   the current output port, increment fanin counter
                     for (auto i : input_ports) {
                         DelayInfo comb_delay;
                         bool is_path = ctx->getCellDelay(cell.second.get(), i, o->name, comb_delay);
@@ -127,9 +121,7 @@ struct Timing
 
         std::deque<NetInfo *> queue(topographical_order.begin(), topographical_order.end());
 
-        // Now walk the design, from the start points identified previously,
+        // Now walk the design, from the start points identified previously, building up a topographical order
-        // building
-        //   up a topographical order
         while (!queue.empty()) {
             const auto net = queue.front();
             queue.pop_front();
@@ -153,8 +145,7 @@ struct Timing
                     bool is_path = ctx->getCellDelay(usr.cell, usr.port, port.first, comb_delay);
                     if (!is_path)
                         continue;
-                    // Decrement the fanin count, and only add to topographical
+                    // Decrement the fanin count, and only add to topographical order if all its fanins have already been visited
-                    //   order if all its fanins have already been visited
                     auto it = port_fanin.find(&port.second);
                     NPNR_ASSERT(it != port_fanin.end());
                     if (--it->second == 0) {
@@ -166,12 +157,10 @@ struct Timing
             }
         }
 
-        // Sanity check to ensure that all ports where fanins were recorded
+        // Sanity check to ensure that all ports where fanins were recorded were indeed visited
-        //   were indeed visited
         NPNR_ASSERT(port_fanin.empty());
 
-        // Go forwards topographically to find the maximum arrival time
+        // Go forwards topographically to find the maximum arrival time and max path length for each net
-        //   and max path length for each net
         for (auto net : topographical_order) {
             auto &nd = net_data.at(net);
             const auto net_arrival = nd.max_arrival;
@@ -197,9 +186,7 @@ struct Timing
                         auto &data = net_data[port.second.net];
                         auto &arrival = data.max_arrival;
                         arrival = std::max(arrival, usr_arrival + comb_delay.maxDelay());
-                        if (!budget_override) { // Do not increment path length if
+                        if (!budget_override) { // Do not increment path length if budget overriden since it doesn't require a share of the slack
-                                                // budget overriden
-                            //   since it doesn't require a share of the slack
                             auto &path_length = data.max_path_length;
                             path_length = std::max(path_length, net_length_plus_one);
                         }
@@ -210,8 +197,7 @@ struct Timing
 
         const NetInfo *crit_net = nullptr;
 
-        // Now go backwards topographically to determine the minimum path slack,
+        // Now go backwards topographically to determine the minimum path slack, and to distribute all path slack evenly between all nets on the path
-        //   and to distribute all path slack evenly between all nets on the path
         for (auto net : boost::adaptors::reverse(topographical_order)) {
             auto &nd = net_data.at(net);
             const delay_t net_length_plus_one = nd.max_path_length + 1;
@@ -348,9 +334,7 @@ void assign_budget(Context *ctx, bool quiet)
         }
     }
 
-    // For slack redistribution, if user has not specified a frequency
+    // For slack redistribution, if user has not specified a frequency dynamically adjust the target frequency to be the currently achieved maximum
-    //   dynamically adjust the target frequency to be the currently
-    //   achieved maximum
     if (ctx->auto_freq && ctx->slack_redist_iter > 0) {
         delay_t default_slack = delay_t(1.0e12 / ctx->target_freq);
         ctx->target_freq = 1e12 / (default_slack - timing.min_slack);