rtlil: use said const iterator

kernel/rtlil.h

@@ -715,7 +715,7 @@ struct RTLIL::Const
 	std::vector<RTLIL::State> to_bits() const;
 
 	std::string decode_string() const;
-	inline size_t size() const {
+	inline int size() const {
 		if (is_str())
 			return 8 * str_.size();
 		else {
@@ -783,11 +783,11 @@ struct RTLIL::Const
 			size_t idx;
 
 		public:
-			using iterator_category = std::random_access_iterator_tag;
-			using value_type = bool;
+			using iterator_category = std::input_iterator_tag;
+			using value_type = State;
 			using difference_type = std::ptrdiff_t;
-			using pointer = const bool*;
-			using reference = bool;
+			using pointer = const State*;
+			using reference = State;
 
 			const_iterator(const Const& c, size_t i) : parent(c), idx(i) {}
 
@@ -893,15 +893,8 @@ struct RTLIL::Const
 	inline unsigned int hash() const {
 		unsigned int h = mkhash_init;
 
-		if(is_str()) {
-			// Copy to avoid unpacking `this`
-			Const c = Const(*this);
-			for (auto b : c.bits())
-				h = mkhash(h, b);
-		} else {
-			for (auto b : get_bits())
-				h = mkhash(h, b);
-		}
+		for (State b : bits())
+			h = mkhash(h, b);
 		return h;
 	}
 };