Readd builtin_ff_cell_types for plugin parity.

kernel/rtlil.cc

@@ -288,6 +288,19 @@ void RTLIL::OwningIdString::collect_garbage()
 
 dict<std::string, std::string> RTLIL::constpad;
 
+const pool<IdString> &RTLIL::builtin_ff_cell_types() {
+	static const pool<IdString> res = []() {
+		pool<IdString> r;
+		for (size_t i = 0; i < StaticCellTypes::builder.count; i++) {
+			auto &cell = StaticCellTypes::builder.cells[i];
+			if (cell.features.is_ff)
+				r.insert(cell.type);
+		}
+		return r;
+	}();
+	return res;
+}
+
 #define check(condition) log_assert(condition && "malformed Const union")
 
 const Const::bitvectype& Const::get_bits() const {

kernel/rtlil.h

@@ -737,6 +737,9 @@ template <> struct IDMacroHelper<-1> {
 namespace RTLIL {
 	extern dict<std::string, std::string> constpad;
 
+	[[deprecated("use StaticCellTypes::categories.is_ff() instead")]]
+	const pool<IdString> &builtin_ff_cell_types();
+
 	static inline std::string escape_id(const std::string &str) {
 		if (str.size() > 0 && str[0] != '\\' && str[0] != '$')
 			return "\\" + str;