Add flag to restart place-and-route on failed target frequency

* Add --restart-on-failed-target-frequency flag and logic to restart the
  place-and-route process if the target frequency is not achieved.

* This flag is intended to be used with the --randomize-seed option to
  generate a new random seed for every run. This can significantly
  improve the chances of achieving a higher clock frequency compared to
  using the default seed.

* Move print_net_source out of log_crit_paths() to remove the 'static'
  keyword, which could otherwise cause a segmentation fault if the
  context is changed.

common/kernel/command.cc

@@ -345,7 +345,9 @@ po::options_description CommandHandler::getGeneralOptions()
  general.add_options()("top", po::value<std::string>(), "name of top module");
  general.add_options()("seed", po::value<uint64_t>(), "seed value for random number generator");
  general.add_options()("randomize-seed,r", "randomize seed value for random number generator");
-
+ general.add_options()("restart-on-failed-target-frequency",
+ "restart place and route if target frequency is not achieved (use together with "
+ "--randomize-seed option)");
  general.add_options()(
  "placer", po::value<std::string>(),
  std::string("placer algorithm to use; available: " + boost::algorithm::join(Arch::availablePlacers, ", ") +
@@ -673,6 +675,17 @@ int CommandHandler::executeMain(std::unique_ptr<Context> ctx)
  ctx->debug = true;
  if (!ctx->place() && !ctx->force)
  log_error("Placing design failed.\n");
+ if (vm.count("restart-on-failed-target-frequency")) {
+ if (!ctx->target_frequency_achieved) {
+ log_break();
+ log_info("Target frequency not achieved, restarting...\n");
+ log_break();
+#ifndef NO_PYTHON
+ deinit_python();
+#endif
+ return 2;
+ }
+ }
  ctx->debug = saved_debug;
  ctx->check();
  if (vm.count("placed-svg"))
@@ -686,6 +699,17 @@ int CommandHandler::executeMain(std::unique_ptr<Context> ctx)
  ctx->debug = true;
  if (!ctx->route() && !ctx->force)
  log_error("Routing design failed.\n");
+ if (vm.count("restart-on-failed-target-frequency")) {
+ if (!ctx->target_frequency_achieved) {
+ log_break();
+ log_info("Target frequency not achieved, restarting...\n");
+ log_break();
+#ifndef NO_PYTHON
+ deinit_python();
+#endif
+ return 2;
+ }
+ }
  ctx->debug = saved_debug;
  run_script_hook("post-route");
  if (vm.count("routed-svg"))
@@ -753,10 +777,15 @@ int CommandHandler::exec()
  return 0;
 
  dict<std::string, Property> values;
+restart:
  std::unique_ptr<Context> ctx = createContext(values);
  setupContext(ctx.get());
  setupArchContext(ctx.get());
  int rc = executeMain(std::move(ctx));
+ if (rc == 2) {
+ ctx.reset();
+ goto restart;
+ }
  printFooter();
  log_break();
  log_info("Program finished normally.\n");

common/kernel/context.h

@@ -38,6 +38,8 @@ struct Context : Arch, DeterministicRNG
  bool disable_critical_path_source_print = false;
  // True when detailed per-net timing is to be stored / reported
  bool detailed_timing_report = false;
+ // Default to true, will update when timing analysis is run
+ bool target_frequency_achieved = true;
 
  ArchArgs arch_args;
 

common/kernel/timing.cc

@@ -1339,6 +1339,16 @@ void timing_analysis(Context *ctx, bool print_slack_histogram, bool print_fmax,
 
  if (update_results)
  ctx->timing_result = result;
+
+ ctx->target_frequency_achieved = true;
+ for (auto &clock : result.clock_paths) {
+ float fmax = result.clock_fmax[clock.first].achieved;
+ float target = result.clock_fmax[clock.first].constraint;
+ bool passed = target < fmax;
+ if (!passed) {
+ ctx->target_frequency_achieved = false;
+ }
+ }
 }
 
 NEXTPNR_NAMESPACE_END

common/kernel/timing_log.cc

@@ -38,35 +38,36 @@ static std::string clock_event_name(const Context *ctx, const ClockEvent &e, int
  return value;
 };
 
-static void log_crit_paths(const Context *ctx, TimingResult &result)
+static void print_net_source(const Context *ctx, const NetInfo *net)
 {
- static auto print_net_source = [ctx](const NetInfo *net) {
- // Check if this net is annotated with a source list
- auto sources = net->attrs.find(ctx->id("src"));
- if (sources == net->attrs.end()) {
- // No sources for this net, can't print anything
- return;
- }
+ // Check if this net is annotated with a source list
+ auto sources = net->attrs.find(ctx->id("src"));
+ if (sources == net->attrs.end()) {
+ // No sources for this net, can't print anything
+ return;
+ }
 
- // Sources are separated by pipe characters.
- // There is no guaranteed ordering on sources, so we just print all
- auto sourcelist = sources->second.as_string();
- std::vector<std::string> source_entries;
- size_t current = 0, prev = 0;
- while ((current = sourcelist.find("|", prev)) != std::string::npos) {
- source_entries.emplace_back(sourcelist.substr(prev, current - prev));
- prev = current + 1;
- }
- // Ensure we emplace the final entry
+ // Sources are separated by pipe characters.
+ // There is no guaranteed ordering on sources, so we just print all
+ auto sourcelist = sources->second.as_string();
+ std::vector<std::string> source_entries;
+ size_t current = 0, prev = 0;
+ while ((current = sourcelist.find("|", prev)) != std::string::npos) {
  source_entries.emplace_back(sourcelist.substr(prev, current - prev));
+ prev = current + 1;
+ }
+ // Ensure we emplace the final entry
+ source_entries.emplace_back(sourcelist.substr(prev, current - prev));
 
-  // Iterate and print our source list at the correct indentation level
-  log_info(" Defined in:\n");
-  for (auto entry : source_entries) {
-  log_info(" %s\n", entry.c_str());
-  }
- };
+ // Iterate and print our source list at the correct indentation level
+ log_info(" Defined in:\n");
+ for (auto entry : source_entries) {
+ log_info(" %s\n", entry.c_str());
+ }
+}
 
+static void log_crit_paths(const Context *ctx, TimingResult &result)
+{
  // A helper function for reporting one critical path
  auto print_path_report = [ctx](const CriticalPath &path) {
  delay_t total(0), logic_total(0), route_total(0);
@@ -137,7 +138,7 @@ static void log_crit_paths(const Context *ctx, TimingResult &result)
  }
 
  if (!ctx->disable_critical_path_source_print) {
- print_net_source(net);
+ print_net_source(ctx, net);
  }
  }
  }