Encode filename unprintable chars

kernel/rtlil.h

@@ -440,6 +440,21 @@ namespace RTLIL
 		}
 	};
 
+	static inline std::string encode_filename(const std::string &filename)
+	{
+		std::stringstream val;
+		if (!std::any_of(filename.begin(), filename.end(), [](char c) { 
+			return static_cast<unsigned char>(c) < 33 || static_cast<unsigned char>(c) > 126; 
+		})) return filename;
+		for (unsigned char const c : filename) {
+			if (c < 33 || c > 126)
+				val << stringf("$%02x", c);
+			else 
+				val << c;
+		}
+		return val.str();
+	}
+
 	// see calc.cc for the implementation of this functions
 	RTLIL::Const const_not         (const RTLIL::Const &arg1, const RTLIL::Const &arg2, bool signed1, bool signed2, int result_len);
 	RTLIL::Const const_and         (const RTLIL::Const &arg1, const RTLIL::Const &arg2, bool signed1, bool signed2, int result_len);