From c5d4b435bdb692b8ca0e4eb1dd84f9b4418f3031 Mon Sep 17 00:00:00 2001
From: "Emil J. Tywoniak" <emil@tywoniak.eu>
Date: Tue, 17 Mar 2026 17:29:23 +0100
Subject: [PATCH] check: stitch info about $connect ports together for driver
 analysis

---
 passes/cmds/check.cc | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/passes/cmds/check.cc b/passes/cmds/check.cc
index 5b89b00b2..d1aedeedd 100644
--- a/passes/cmds/check.cc
+++ b/passes/cmds/check.cc
@@ -267,6 +267,27 @@ struct CheckPass : public Pass {
 				cell_allowed:;
 				}
 
+				if (cell->type == ID($connect)) {
+					// Inefficient, but rare case in sane design
+					auto sig_a = cell->getPort(ID::A);
+					auto sig_b = cell->getPort(ID::B);
+					for (int i = 0; i < sig_a.size(); i++) {
+						int count_a = wire_drivers_count[sig_a[i]];
+						int count_b = wire_drivers_count[sig_b[i]];
+						wire_drivers_count[sig_a[i]] += count_b;
+						wire_drivers_count[sig_b[i]] += count_a;
+						auto& drivers_a = wire_drivers[sig_a[i]];
+						auto& drivers_b = wire_drivers[sig_b[i]];
+						vector<string> drivers;
+						drivers.reserve(std::max(drivers_a.size(), drivers_b.size()));
+						for (auto driver : drivers_a)
+							drivers.push_back(driver);
+						for (auto driver : drivers_b)
+							drivers.push_back(driver);
+						drivers_a = drivers;
+						drivers_b = drivers;
+					}
+				}
 				for (auto &conn : cell->connections()) {
 					bool input = cell->input(conn.first);
 					bool output = cell->output(conn.first);