timing: Add --ignore-loops option

Signed-off-by: David Shah <dave@ds0.me>

2 files changed, 7 insertions, 1 deletions

diff --git a/common/command.cc b/common/command.cc
index 6ba3442f..8f18f54d 100644
--- a/common/command.cc
+++ b/common/command.cc
@@ -124,6 +124,8 @@ po::options_description CommandHandler::getGeneralOptions()
     general.add_options()("cstrweight", po::value<float>(), "placer weighting for relative constraint satisfaction");
     general.add_options()("pack-only", "pack design only without placement or routing");
 
+    general.add_options()("ignore-loops", "ignore combinational loops in timing analysis");
+
     general.add_options()("version,V", "show version");
     general.add_options()("test", "check architecture database integrity");
     general.add_options()("freq", po::value<double>(), "set target frequency for design in MHz");
@@ -172,6 +174,10 @@ void CommandHandler::setupContext(Context *ctx)
         }
     }
 
+    if (vm.count("ignore-loops")) {
+        settings->set("timing/ignoreLoops", true);
+    }
+
     if (vm.count("cstrweight")) {
         settings->set("placer1/constraintWeight", vm["cstrweight"].as<float>());
     }
diff --git a/common/timing.cc b/common/timing.cc
index f3cb4306..13f0e07b 100644
--- a/common/timing.cc
+++ b/common/timing.cc
@@ -225,7 +225,7 @@ struct Timing
         }
 
         // Sanity check to ensure that all ports where fanins were recorded were indeed visited
-        if (!port_fanin.empty()) {
+        if (!port_fanin.empty() && !bool_or_default(ctx->settings, ctx->id("timing/ignoreLoops"), false)) {
             for (auto fanin : port_fanin) {
                 NetInfo *net = fanin.first->net;
                 if (net != nullptr) {