From d07828b40958c6c2a1d09cf13c9a307c75b855b4 Mon Sep 17 00:00:00 2001
From: =?utf8?q?Marcelina=20Ko=C5=9Bcielnicka?= <mwk@0x04.net>
Date: Tue, 7 Jun 2022 04:26:25 +0200
Subject: [PATCH] opt_ffinv: Harden against simple ff/inv loop.

---
 passes/opt/opt_ffinv.cc | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/passes/opt/opt_ffinv.cc b/passes/opt/opt_ffinv.cc
index fd76dd2be..fe5b59fa5 100644
--- a/passes/opt/opt_ffinv.cc
+++ b/passes/opt/opt_ffinv.cc
@@ -72,6 +72,8 @@ struct OptFfInvWorker
 		for (auto &port: q_ports) {
 			if (port.cell == ff.cell && port.port == ID::Q)
 				continue;
+			if (port.cell == d_inv)
+				return false;
 			if (port.port != ID::A)
 				return false;
 			if (!port.cell->type.in(ID($not), ID($_NOT_), ID($lut)))
@@ -148,6 +150,8 @@ struct OptFfInvWorker
 		for (auto &port: q_ports) {
 			if (port.cell == ff.cell && port.port == ID::Q)
 				continue;
+			if (port.cell == d_lut)
+				return false;
 			if (port.port != ID::A)
 				return false;
 			if (port.cell->type.in(ID($not), ID($_NOT_))) {
-- 
2.30.2