diff --git a/passes/opt/opt_dff.cc b/passes/opt/opt_dff.cc
index 4ed4b0cb6..210c4828f 100644
--- a/passes/opt/opt_dff.cc
+++ b/passes/opt/opt_dff.cc
@@ -170,9 +170,62 @@ struct OptDffWorker
 		return ret;
 	}
 
-	void simplify_patterns(patterns_t&)
+	void simplify_patterns(patterns_t& patterns)
 	{
-		// TBD
+		auto new_patterns = patterns;
+		auto find_comp = [](const auto& left, const auto& right) -> std::optional<RTLIL::SigBit> {
+			std::optional<RTLIL::SigBit> ret;
+			for (const auto &pt: left)
+				if (right.count(pt.first) == 0)
+					return {};
+				else if (right.at(pt.first) == pt.second)
+					continue;
+				else
+					if (ret)
+						return {};
+					else
+						ret = pt.first;
+			return ret;
+		};
+
+		// remove complimentary patterns
+		bool optimized;
+		do {
+			optimized = false;
+			for (auto i = patterns.begin(); i != patterns.end(); i++) {
+				for (auto j = std::next(i, 1); j != patterns.end(); j++) {
+					const auto& left = (GetSize(*j) <= GetSize(*i)) ? *j : *i;
+					auto right = (GetSize(*i) < GetSize(*j)) ? *j : *i;
+
+					const auto complimentary_var = find_comp(left, right);
+
+					if (complimentary_var) {
+						new_patterns.erase(right);
+						right.erase(complimentary_var.value());
+						new_patterns.insert(right);
+						optimized = true;
+					}
+				}
+			}
+			patterns = new_patterns;
+		} while(optimized);
+
+		// remove redundant patterns
+		for (auto i = patterns.begin(); i != patterns.end(); ++i) {
+			for (auto j = std::next(i, 1); j != patterns.end(); ++j) {
+				const auto& left = (GetSize(*j) <= GetSize(*i)) ? *j : *i;
+				const auto& right = (GetSize(*i) < GetSize(*j)) ? *j : *i;
+
+		            	bool redundant = true;
+
+				for (const auto& pt : left)
+					if (right.count(pt.first) == 0 || right.at(pt.first) != pt.second)
+						redundant = false;
+				if (redundant)
+					new_patterns.erase(right);
+			}
+		}
+		patterns = std::move(new_patterns);
 	}
 
 	ctrl_t make_patterns_logic(const patterns_t &patterns, const ctrls_t &ctrls, bool make_gates)
diff --git a/tests/arch/quicklogic/pp3/fsm.ys b/tests/arch/quicklogic/pp3/fsm.ys
index 418db8025..9679628e9 100644
--- a/tests/arch/quicklogic/pp3/fsm.ys
+++ b/tests/arch/quicklogic/pp3/fsm.ys
@@ -11,8 +11,8 @@ sat -verify -prove-asserts -show-public -set-at 1 in_reset 1 -seq 20 -prove-skip
 design -load postopt # load the post-opt design (otherwise equiv_opt loads the pre-opt design)
 cd fsm # Constrain all select calls below inside the top module
 
-select -assert-count 1 t:LUT2
-select -assert-count 9 t:LUT3
+select -assert-count 2 t:LUT2
+select -assert-count 4 t:LUT3
 select -assert-count 4 t:dffepc
 select -assert-count 1 t:logic_0
 select -assert-count 1 t:logic_1
@@ -20,4 +20,4 @@ select -assert-count 3 t:inpad
 select -assert-count 2 t:outpad
 select -assert-count 1 t:ckpad
 
-select -assert-none t:LUT2 t:LUT3 t:dffepc t:logic_0 t:logic_1 t:inpad t:outpad t:ckpad %% t:* %D
+select -assert-none t:LUT2 t:LUT3 t:LUT4 t:dffepc t:logic_0 t:logic_1 t:inpad t:outpad t:ckpad %% t:* %D