diff --git a/backends/aiger2/aiger.cc b/backends/aiger2/aiger.cc
index a230cda4f..141217fe5 100644
--- a/backends/aiger2/aiger.cc
+++ b/backends/aiger2/aiger.cc
@@ -262,7 +262,8 @@ struct Index {
 				if (cell->type.in(ID($gt), ID($ge)))
 					std::swap(aport, bport);
 				int carry = cell->type.in(ID($le), ID($ge)) ? CFALSE : CTRUE; 
-				Lit a, b;
+				Lit a = Writer::EMPTY_LIT;
+				Lit b = Writer::EMPTY_LIT;
 				// TODO: this might not be the most economic structure; revisit at a later date
 				for (int i = 0; i < width; i++) {
 					a = visit(cursor, aport[i]);
@@ -664,8 +665,6 @@ struct Index {
 struct AigerWriter : Index<AigerWriter, unsigned int, 0, 1> {
 	typedef unsigned int Lit;
 
-	const static Lit CONST_FALSE = 0;
-	const static Lit CONST_TRUE = 1;
 	const static constexpr Lit EMPTY_LIT = std::numeric_limits<Lit>::max();
 
 	static Lit negate(Lit lit) {
@@ -802,8 +801,6 @@ struct AigerWriter : Index<AigerWriter, unsigned int, 0, 1> {
 };
 
 struct XAigerAnalysis : Index<XAigerAnalysis, int, 0, 0> {
-	const static int CONST_FALSE = 0;
-	const static int CONST_TRUE = 0;
 	const static constexpr int EMPTY_LIT = -1;
 
 	XAigerAnalysis()
diff --git a/backends/edif/edif.cc b/backends/edif/edif.cc
index c664c41eb..d751a5996 100644
--- a/backends/edif/edif.cc
+++ b/backends/edif/edif.cc
@@ -338,7 +338,7 @@ struct EdifBackend : public Backend {
 				*f << stringf("\n            (property %s (integer %u))", EDIF_DEF(name), val.as_int());
 			else {
 				std::string hex_string = "";
-				for (size_t i = 0; i < val.size(); i += 4) {
+				for (auto i = 0; i < val.size(); i += 4) {
 					int digit_value = 0;
 					if (i+0 < val.size() && val.at(i+0) == RTLIL::State::S1) digit_value |= 1;
 					if (i+1 < val.size() && val.at(i+1) == RTLIL::State::S1) digit_value |= 2;
diff --git a/frontends/aiger2/xaiger.cc b/frontends/aiger2/xaiger.cc
index 04beee396..dd3ca4285 100644
--- a/frontends/aiger2/xaiger.cc
+++ b/frontends/aiger2/xaiger.cc
@@ -198,11 +198,10 @@ struct Xaiger2Frontend : public Frontend {
 
 				int ci_counter = 0;
 				for (uint32_t i = 0; i < no_boxes; i++) {
-					uint32_t box_inputs, box_outputs, box_id, box_seq;
-					box_inputs = read_be32(*f);
-					box_outputs = read_be32(*f);
-					box_id = read_be32(*f);
-					box_seq = read_be32(*f);
+					/* unused box_inputs = */ read_be32(*f);
+					YS_MAYBE_UNUSED auto box_outputs = read_be32(*f);
+					/* unused box_id = */ read_be32(*f);
+					auto box_seq = read_be32(*f);
 
 					log("box_seq=%d boxes.size=%d\n", box_seq, (int) boxes.size());
 					log_assert(box_seq < boxes.size());
@@ -337,11 +336,10 @@ struct Xaiger2Frontend : public Frontend {
 						  len, ci_num, co_num, pi_num, po_num, no_boxes);
 
 				for (uint32_t i = 0; i < no_boxes; i++) {
-					uint32_t box_inputs, box_outputs, box_id, box_seq;
-					box_inputs = read_be32(*f);
-					box_outputs = read_be32(*f);
-					box_id = read_be32(*f);
-					box_seq = read_be32(*f);
+					YS_MAYBE_UNUSED auto box_inputs = read_be32(*f);
+					/* unused box_outputs = */ read_be32(*f);
+					/* unused box_id = */ read_be32(*f);
+					auto box_seq = read_be32(*f);
 
 					log("box_seq=%d boxes.size=%d\n", box_seq, (int) boxes.size());
 					log_assert(box_seq < boxes.size());
diff --git a/frontends/ast/ast.cc b/frontends/ast/ast.cc
index c5bf5b4ad..431f7b4f8 100644
--- a/frontends/ast/ast.cc
+++ b/frontends/ast/ast.cc
@@ -931,7 +931,7 @@ bool AstNode::bits_only_01() const
 RTLIL::Const AstNode::bitsAsUnsizedConst(int width)
 {
 	RTLIL::State extbit = bits.back();
-	while (width > int(bits.size()))
+	while (width > GetSize(bits))
 		bits.push_back(extbit);
 	return RTLIL::Const(bits);
 }
@@ -939,13 +939,13 @@ RTLIL::Const AstNode::bitsAsUnsizedConst(int width)
 RTLIL::Const AstNode::bitsAsConst(int width, bool is_signed)
 {
 	std::vector<RTLIL::State> bits = this->bits;
-	if (width >= 0 && width < int(bits.size()))
+	if (width >= 0 && width < GetSize(bits))
 		bits.resize(width);
-	if (width >= 0 && width > int(bits.size())) {
+	if (width >= 0 && width > GetSize(bits)) {
 		RTLIL::State extbit = RTLIL::State::S0;
 		if ((is_signed || is_unsized) && !bits.empty())
 			extbit = bits.back();
-		while (width > int(bits.size()))
+		while (width > GetSize(bits))
 			bits.push_back(extbit);
 	}
 	return RTLIL::Const(bits);
@@ -1029,7 +1029,7 @@ double AstNode::asReal(bool is_signed)
 			val = const_neg(val, val, false, false, val.size());
 
 		double v = 0;
-		for (size_t i = 0; i < val.size(); i++)
+		for (auto i = 0; i < val.size(); i++)
 			// IEEE Std 1800-2012 Par 6.12.2: Individual bits that are x or z in
 			// the net or the variable shall be treated as zero upon conversion.
 			if (val.at(i) == RTLIL::State::S1)
diff --git a/frontends/ast/genrtlil.cc b/frontends/ast/genrtlil.cc
index ea7da521c..d3982b92b 100644
--- a/frontends/ast/genrtlil.cc
+++ b/frontends/ast/genrtlil.cc
@@ -984,7 +984,7 @@ void AstNode::detectSignWidthWorker(int &width_hint, bool &sign_hint, bool *foun
 		// unallocated enum, ignore
 		break;
 	case AST_CONSTANT:
-		width_hint = max(width_hint, int(bits.size()));
+		width_hint = max(width_hint, GetSize(bits));
 		if (!is_signed)
 			sign_hint = false;
 		break;
diff --git a/frontends/ast/simplify.cc b/frontends/ast/simplify.cc
index 6d78369cc..b00cde28e 100644
--- a/frontends/ast/simplify.cc
+++ b/frontends/ast/simplify.cc
@@ -3493,7 +3493,7 @@ skip_dynamic_range_lvalue_expansion:;
 				delete buf;
 
 				uint32_t result = 0;
-				for (size_t i = 0; i < arg_value.size(); i++)
+				for (auto i = 0; i < arg_value.size(); i++)
 					if (arg_value.at(i) == RTLIL::State::S1)
 						result = i + 1;
 
@@ -4339,7 +4339,7 @@ replace_fcall_later:;
 					RTLIL::Const a = children[1]->bitsAsConst(width_hint, sign_hint);
 					RTLIL::Const b = children[2]->bitsAsConst(width_hint, sign_hint);
 					log_assert(a.size() == b.size());
-					for (size_t i = 0; i < a.size(); i++)
+					for (auto i = 0; i < a.size(); i++)
 						if (a[i] != b[i])
 							a.bits()[i] = RTLIL::State::Sx;
 					newNode = mkconst_bits(a.to_bits(), sign_hint);
diff --git a/kernel/calc.cc b/kernel/calc.cc
index 172b6a905..f08c97396 100644
--- a/kernel/calc.cc
+++ b/kernel/calc.cc
@@ -33,7 +33,7 @@ static void extend_u0(RTLIL::Const &arg, int width, bool is_signed)
 	if (arg.size() > 0 && is_signed)
 		padding = arg.back();
 
-	while (int(arg.size()) < width)
+	while (GetSize(arg) < width)
 		arg.bits().push_back(padding);
 
 	arg.bits().resize(width);
@@ -45,7 +45,7 @@ static BigInteger const2big(const RTLIL::Const &val, bool as_signed, int &undef_
 
 	BigInteger::Sign sign = BigInteger::positive;
 	State inv_sign_bit = RTLIL::State::S1;
-	size_t num_bits = val.size();
+	auto num_bits = val.size();
 
 	if (as_signed && num_bits && val[num_bits-1] == RTLIL::State::S1) {
 		inv_sign_bit = RTLIL::State::S0;
@@ -53,7 +53,7 @@ static BigInteger const2big(const RTLIL::Const &val, bool as_signed, int &undef_
 		num_bits--;
 	}
 
-	for (size_t i = 0; i < num_bits; i++)
+	for (auto i = 0; i < num_bits; i++)
 		if (val[i] == RTLIL::State::S0 || val[i] == RTLIL::State::S1)
 			mag.setBit(i, val[i] == inv_sign_bit);
 		else if (undef_bit_pos < 0)
@@ -78,12 +78,12 @@ static RTLIL::Const big2const(const BigInteger &val, int result_len, int undef_b
 		if (val.getSign() < 0)
 		{
 			mag--;
-			for (int i = 0; i < result_len; i++)
+			for (auto i = 0; i < result_len; i++)
 				result.bits()[i] = mag.getBit(i) ? RTLIL::State::S0 : RTLIL::State::S1;
 		}
 		else
 		{
-			for (int i = 0; i < result_len; i++)
+			for (auto i = 0; i < result_len; i++)
 				result.bits()[i] = mag.getBit(i) ? RTLIL::State::S1 : RTLIL::State::S0;
 		}
 	}
@@ -132,14 +132,14 @@ static RTLIL::State logic_xnor(RTLIL::State a, RTLIL::State b)
 RTLIL::Const RTLIL::const_not(const RTLIL::Const &arg1, const RTLIL::Const&, bool signed1, bool, int result_len)
 {
 	if (result_len < 0)
-		result_len = arg1.size();
+		result_len = GetSize(arg1);
 
 	RTLIL::Const arg1_ext = arg1;
 	extend_u0(arg1_ext, result_len, signed1);
 
 	RTLIL::Const result(RTLIL::State::Sx, result_len);
-	for (size_t i = 0; i < size_t(result_len); i++) {
-		if (i >= arg1_ext.size())
+	for (auto i = 0; i < result_len; i++) {
+		if (i >= GetSize(arg1_ext))
 			result.bits()[i] = RTLIL::State::S0;
 		else if (arg1_ext.bits()[i] == RTLIL::State::S0)
 			result.bits()[i] = RTLIL::State::S1;
@@ -154,15 +154,15 @@ static RTLIL::Const logic_wrapper(RTLIL::State(*logic_func)(RTLIL::State, RTLIL:
 		RTLIL::Const arg1, RTLIL::Const arg2, bool signed1, bool signed2, int result_len = -1)
 {
 	if (result_len < 0)
-		result_len = max(arg1.size(), arg2.size());
+		result_len = max(GetSize(arg1), GetSize(arg2));
 
 	extend_u0(arg1, result_len, signed1);
 	extend_u0(arg2, result_len, signed2);
 
 	RTLIL::Const result(RTLIL::State::Sx, result_len);
-	for (size_t i = 0; i < size_t(result_len); i++) {
-		RTLIL::State a = i < arg1.size() ? arg1.bits()[i] : RTLIL::State::S0;
-		RTLIL::State b = i < arg2.size() ? arg2.bits()[i] : RTLIL::State::S0;
+	for (auto i = 0; i < result_len; i++) {
+		RTLIL::State a = i < GetSize(arg1) ? arg1.bits()[i] : RTLIL::State::S0;
+		RTLIL::State b = i < GetSize(arg2) ? arg2.bits()[i] : RTLIL::State::S0;
 		result.bits()[i] = logic_func(a, b);
 	}
 
@@ -193,11 +193,11 @@ static RTLIL::Const logic_reduce_wrapper(RTLIL::State initial, RTLIL::State(*log
 {
 	RTLIL::State temp = initial;
 
-	for (size_t i = 0; i < arg1.size(); i++)
+	for (auto i = 0; i < arg1.size(); i++)
 		temp = logic_func(temp, arg1[i]);
 
 	RTLIL::Const result(temp);
-	while (int(result.size()) < result_len)
+	while (GetSize(result) < result_len)
 		result.bits().push_back(RTLIL::State::S0);
 	return result;
 }
@@ -240,7 +240,7 @@ RTLIL::Const RTLIL::const_logic_not(const RTLIL::Const &arg1, const RTLIL::Const
 	BigInteger a = const2big(arg1, signed1, undef_bit_pos_a);
 	RTLIL::Const result(a.isZero() ? undef_bit_pos_a >= 0 ? RTLIL::State::Sx : RTLIL::State::S1 : RTLIL::State::S0);
 
-	while (int(result.size()) < result_len)
+	while (GetSize(result) < result_len)
 		result.bits().push_back(RTLIL::State::S0);
 	return result;
 }
@@ -255,7 +255,7 @@ RTLIL::Const RTLIL::const_logic_and(const RTLIL::Const &arg1, const RTLIL::Const
 	RTLIL::State bit_b = b.isZero() ? undef_bit_pos_b >= 0 ? RTLIL::State::Sx : RTLIL::State::S0 : RTLIL::State::S1;
 	RTLIL::Const result(logic_and(bit_a, bit_b));
 
-	while (int(result.size()) < result_len)
+	while (GetSize(result) < result_len)
 		result.bits().push_back(RTLIL::State::S0);
 	return result;
 }
@@ -270,7 +270,7 @@ RTLIL::Const RTLIL::const_logic_or(const RTLIL::Const &arg1, const RTLIL::Const
 	RTLIL::State bit_b = b.isZero() ? undef_bit_pos_b >= 0 ? RTLIL::State::Sx : RTLIL::State::S0 : RTLIL::State::S1;
 	RTLIL::Const result(logic_or(bit_a, bit_b));
 
-	while (int(result.size()) < result_len)
+	while (GetSize(result) < result_len)
 		result.bits().push_back(RTLIL::State::S0);
 	return result;
 }
@@ -286,7 +286,7 @@ static RTLIL::Const const_shift_worker(const RTLIL::Const &arg1, const RTLIL::Co
 	BigInteger offset = const2big(arg2, signed2, undef_bit_pos) * direction;
 
 	if (result_len < 0)
-		result_len = arg1.size();
+		result_len = GetSize(arg1);
 
 	RTLIL::Const result(RTLIL::State::Sx, result_len);
 	if (undef_bit_pos >= 0)
@@ -296,7 +296,7 @@ static RTLIL::Const const_shift_worker(const RTLIL::Const &arg1, const RTLIL::Co
 		BigInteger pos = BigInteger(i) + offset;
 		if (pos < 0)
 			result.bits()[i] = vacant_bits;
-		else if (pos >= BigInteger(int(arg1.size())))
+		else if (pos >= BigInteger(GetSize(arg1)))
 			result.bits()[i] = sign_ext ? arg1.back() : vacant_bits;
 		else
 			result.bits()[i] = arg1[pos.toInt()];
@@ -347,7 +347,7 @@ RTLIL::Const RTLIL::const_lt(const RTLIL::Const &arg1, const RTLIL::Const &arg2,
 	bool y = const2big(arg1, signed1, undef_bit_pos) < const2big(arg2, signed2, undef_bit_pos);
 	RTLIL::Const result(undef_bit_pos >= 0 ? RTLIL::State::Sx : y ? RTLIL::State::S1 : RTLIL::State::S0);
 
-	while (int(result.size()) < result_len)
+	while (GetSize(result) < result_len)
 		result.bits().push_back(RTLIL::State::S0);
 	return result;
 }
@@ -358,7 +358,7 @@ RTLIL::Const RTLIL::const_le(const RTLIL::Const &arg1, const RTLIL::Const &arg2,
 	bool y = const2big(arg1, signed1, undef_bit_pos) <= const2big(arg2, signed2, undef_bit_pos);
 	RTLIL::Const result(undef_bit_pos >= 0 ? RTLIL::State::Sx : y ? RTLIL::State::S1 : RTLIL::State::S0);
 
-	while (int(result.size()) < result_len)
+	while (GetSize(result) < result_len)
 		result.bits().push_back(RTLIL::State::S0);
 	return result;
 }
@@ -369,12 +369,12 @@ RTLIL::Const RTLIL::const_eq(const RTLIL::Const &arg1, const RTLIL::Const &arg2,
 	RTLIL::Const arg2_ext = arg2;
 	RTLIL::Const result(RTLIL::State::S0, result_len);
 
-	int width = max(arg1_ext.size(), arg2_ext.size());
+	int width = max(GetSize(arg1_ext), GetSize(arg2_ext));
 	extend_u0(arg1_ext, width, signed1 && signed2);
 	extend_u0(arg2_ext, width, signed1 && signed2);
 
 	RTLIL::State matched_status = RTLIL::State::S1;
-	for (size_t i = 0; i < arg1_ext.size(); i++) {
+	for (auto i = 0; i < arg1_ext.size(); i++) {
 		if (arg1_ext.at(i) == RTLIL::State::S0 && arg2_ext.at(i) == RTLIL::State::S1)
 			return result;
 		if (arg1_ext.at(i) == RTLIL::State::S1 && arg2_ext.at(i) == RTLIL::State::S0)
@@ -403,11 +403,11 @@ RTLIL::Const RTLIL::const_eqx(const RTLIL::Const &arg1, const RTLIL::Const &arg2
 	RTLIL::Const arg2_ext = arg2;
 	RTLIL::Const result(RTLIL::State::S0, result_len);
 
-	int width = max(arg1_ext.size(), arg2_ext.size());
+	int width = max(GetSize(arg1_ext), GetSize(arg2_ext));
 	extend_u0(arg1_ext, width, signed1 && signed2);
 	extend_u0(arg2_ext, width, signed1 && signed2);
 
-	for (size_t i = 0; i < arg1_ext.size(); i++) {
+	for (auto i = 0; i < arg1_ext.size(); i++) {
 		if (arg1_ext.at(i) != arg2_ext.at(i))
 			return result;
 	}
@@ -432,7 +432,7 @@ RTLIL::Const RTLIL::const_ge(const RTLIL::Const &arg1, const RTLIL::Const &arg2,
 	bool y = const2big(arg1, signed1, undef_bit_pos) >= const2big(arg2, signed2, undef_bit_pos);
 	RTLIL::Const result(undef_bit_pos >= 0 ? RTLIL::State::Sx : y ? RTLIL::State::S1 : RTLIL::State::S0);
 
-	while (int(result.size()) < result_len)
+	while (GetSize(result) < result_len)
 		result.bits().push_back(RTLIL::State::S0);
 	return result;
 }
@@ -443,7 +443,7 @@ RTLIL::Const RTLIL::const_gt(const RTLIL::Const &arg1, const RTLIL::Const &arg2,
 	bool y = const2big(arg1, signed1, undef_bit_pos) > const2big(arg2, signed2, undef_bit_pos);
 	RTLIL::Const result(undef_bit_pos >= 0 ? RTLIL::State::Sx : y ? RTLIL::State::S1 : RTLIL::State::S0);
 
-	while (int(result.size()) < result_len)
+	while (GetSize(result) < result_len)
 		result.bits().push_back(RTLIL::State::S0);
 	return result;
 }
@@ -452,21 +452,21 @@ RTLIL::Const RTLIL::const_add(const RTLIL::Const &arg1, const RTLIL::Const &arg2
 {
 	int undef_bit_pos = -1;
 	BigInteger y = const2big(arg1, signed1, undef_bit_pos) + const2big(arg2, signed2, undef_bit_pos);
-	return big2const(y, result_len >= 0 ? result_len : max(arg1.size(), arg2.size()), undef_bit_pos);
+	return big2const(y, result_len >= 0 ? result_len : max(GetSize(arg1), GetSize(arg2)), undef_bit_pos);
 }
 
 RTLIL::Const RTLIL::const_sub(const RTLIL::Const &arg1, const RTLIL::Const &arg2, bool signed1, bool signed2, int result_len)
 {
 	int undef_bit_pos = -1;
 	BigInteger y = const2big(arg1, signed1, undef_bit_pos) - const2big(arg2, signed2, undef_bit_pos);
-	return big2const(y, result_len >= 0 ? result_len : max(arg1.size(), arg2.size()), undef_bit_pos);
+	return big2const(y, result_len >= 0 ? result_len : max(GetSize(arg1), GetSize(arg2)), undef_bit_pos);
 }
 
 RTLIL::Const RTLIL::const_mul(const RTLIL::Const &arg1, const RTLIL::Const &arg2, bool signed1, bool signed2, int result_len)
 {
 	int undef_bit_pos = -1;
 	BigInteger y = const2big(arg1, signed1, undef_bit_pos) * const2big(arg2, signed2, undef_bit_pos);
-	return big2const(y, result_len >= 0 ? result_len : max(arg1.size(), arg2.size()), min(undef_bit_pos, 0));
+	return big2const(y, result_len >= 0 ? result_len : max(GetSize(arg1), GetSize(arg2)), min(undef_bit_pos, 0));
 }
 
 // truncating division
@@ -480,7 +480,7 @@ RTLIL::Const RTLIL::const_div(const RTLIL::Const &arg1, const RTLIL::Const &arg2
 	bool result_neg = (a.getSign() == BigInteger::negative) != (b.getSign() == BigInteger::negative);
 	a = a.getSign() == BigInteger::negative ? -a : a;
 	b = b.getSign() == BigInteger::negative ? -b : b;
-	return big2const(result_neg ? -(a / b) : (a / b), result_len >= 0 ? result_len : max(arg1.size(), arg2.size()), min(undef_bit_pos, 0));
+	return big2const(result_neg ? -(a / b) : (a / b), result_len >= 0 ? result_len : max(GetSize(arg1), GetSize(arg2)), min(undef_bit_pos, 0));
 }
 
 // truncating modulo
@@ -494,7 +494,7 @@ RTLIL::Const RTLIL::const_mod(const RTLIL::Const &arg1, const RTLIL::Const &arg2
 	bool result_neg = a.getSign() == BigInteger::negative;
 	a = a.getSign() == BigInteger::negative ? -a : a;
 	b = b.getSign() == BigInteger::negative ? -b : b;
-	return big2const(result_neg ? -(a % b) : (a % b), result_len >= 0 ? result_len : max(arg1.size(), arg2.size()), min(undef_bit_pos, 0));
+	return big2const(result_neg ? -(a % b) : (a % b), result_len >= 0 ? result_len : max(GetSize(arg1), GetSize(arg2)), min(undef_bit_pos, 0));
 }
 
 RTLIL::Const RTLIL::const_divfloor(const RTLIL::Const &arg1, const RTLIL::Const &arg2, bool signed1, bool signed2, int result_len)
@@ -516,7 +516,7 @@ RTLIL::Const RTLIL::const_divfloor(const RTLIL::Const &arg1, const RTLIL::Const
 		// bigint division with negative numbers is wonky, make sure we only negate at the very end
 		result = -((a + b - 1) / b);
 	}
-	return big2const(result, result_len >= 0 ? result_len : max(arg1.size(), arg2.size()), min(undef_bit_pos, 0));
+	return big2const(result, result_len >= 0 ? result_len : max(GetSize(arg1), GetSize(arg2)), min(undef_bit_pos, 0));
 }
 
 RTLIL::Const RTLIL::const_modfloor(const RTLIL::Const &arg1, const RTLIL::Const &arg2, bool signed1, bool signed2, int result_len)
@@ -539,7 +539,7 @@ RTLIL::Const RTLIL::const_modfloor(const RTLIL::Const &arg1, const RTLIL::Const
 	} else {
 		modulo = b_sign == BigInteger::negative ? truncated - b : truncated + b;
 	}
-	return big2const(modulo, result_len >= 0 ? result_len : max(arg1.size(), arg2.size()), min(undef_bit_pos, 0));
+	return big2const(modulo, result_len >= 0 ? result_len : max(GetSize(arg1), GetSize(arg2)), min(undef_bit_pos, 0));
 }
 
 RTLIL::Const RTLIL::const_pow(const RTLIL::Const &arg1, const RTLIL::Const &arg2, bool signed1, bool signed2, int result_len)
@@ -590,7 +590,7 @@ RTLIL::Const RTLIL::const_pow(const RTLIL::Const &arg1, const RTLIL::Const &arg2
 			y *= -1;
 	}
 
-	return big2const(y, result_len >= 0 ? result_len : max(arg1.size(), arg2.size()), min(undef_bit_pos, 0));
+	return big2const(y, result_len >= 0 ? result_len : max(GetSize(arg1), GetSize(arg2)), min(undef_bit_pos, 0));
 }
 
 RTLIL::Const RTLIL::const_pos(const RTLIL::Const &arg1, const RTLIL::Const&, bool signed1, bool, int result_len)
@@ -626,7 +626,7 @@ RTLIL::Const RTLIL::const_mux(const RTLIL::Const &arg1, const RTLIL::Const &arg2
 		return arg2;
 
 	RTLIL::Const ret = arg1;
-	for (int i = 0; i < ret.size(); i++)
+	for (auto i = 0; i < ret.size(); i++)
 		if (ret[i] != arg2[i])
 			ret.bits()[i] = State::Sx;
 	return ret;
@@ -640,7 +640,7 @@ RTLIL::Const RTLIL::const_pmux(const RTLIL::Const &arg1, const RTLIL::Const &arg
 	if (!arg3.is_onehot())
 		return RTLIL::Const(State::Sx, arg1.size());
 
-	for (int i = 0; i < arg3.size(); i++)
+	for (auto i = 0; i < arg3.size(); i++)
 		if (arg3[i] == State::S1)
 			return RTLIL::Const(std::vector<RTLIL::State>(arg2.begin() + i*arg1.size(), arg2.begin() + (i+1)*arg1.size()));
 
@@ -702,7 +702,7 @@ RTLIL::Const RTLIL::const_bweqx(const RTLIL::Const &arg1, const RTLIL::Const &ar
 {
 	log_assert(arg2.size() == arg1.size());
 	RTLIL::Const result(RTLIL::State::S0, arg1.size());
-	for (int i = 0; i < arg1.size(); i++)
+	for (auto i = 0; i < arg1.size(); i++)
 		result.bits()[i] = arg1[i] == arg2[i] ? State::S1 : State::S0;
 
 	return result;
@@ -713,7 +713,7 @@ RTLIL::Const RTLIL::const_bwmux(const RTLIL::Const &arg1, const RTLIL::Const &ar
 	log_assert(arg2.size() == arg1.size());
 	log_assert(arg3.size() == arg1.size());
 	RTLIL::Const result(RTLIL::State::Sx, arg1.size());
-	for (int i = 0; i < arg1.size(); i++) {
+	for (auto i = 0; i < arg1.size(); i++) {
 		if (arg3[i] != State::Sx || arg1[i] == arg2[i])
 			result.bits()[i] = arg3[i] == State::S1 ? arg2[i] : arg1[i];
 	}
diff --git a/kernel/rtlil.cc b/kernel/rtlil.cc
index e9b648b04..087d3ff92 100644
--- a/kernel/rtlil.cc
+++ b/kernel/rtlil.cc
@@ -380,7 +380,7 @@ int RTLIL::Const::as_int(bool is_signed) const
 	return ret;
 }
 
-size_t RTLIL::Const::get_min_size(bool is_signed) const
+int RTLIL::Const::get_min_size(bool is_signed) const
 {
 	if (empty()) return 0;
 
@@ -391,7 +391,7 @@ size_t RTLIL::Const::get_min_size(bool is_signed) const
 	else
 		leading_bit = RTLIL::State::S0;
 
-	size_t idx = size();
+	auto idx = size();
 	while (idx > 0 && (*this)[idx -1] == leading_bit) {
 		idx--;
 	}
@@ -406,22 +406,22 @@ size_t RTLIL::Const::get_min_size(bool is_signed) const
 
 void RTLIL::Const::compress(bool is_signed)
 {
-	size_t idx = get_min_size(is_signed);
+	auto idx = get_min_size(is_signed);
 	bits().erase(bits().begin() + idx, bits().end());
 }
 
 std::optional<int> RTLIL::Const::as_int_compress(bool is_signed) const
 {
-	size_t size = get_min_size(is_signed);
+	auto size = get_min_size(is_signed);
 	if(size == 0 || size > 32)
 		return std::nullopt;
 
 	int32_t ret = 0;
-	for (size_t i = 0; i < size && i < 32; i++)
+	for (auto i = 0; i < size && i < 32; i++)
 		if ((*this)[i] == State::S1)
 			ret |= 1 << i;
 	if (is_signed && (*this)[size-1] == State::S1)
-		for (size_t i = size; i < 32; i++)
+		for (auto i = size; i < 32; i++)
 			ret |= 1 << i;
 	return ret;
 }
diff --git a/kernel/rtlil.h b/kernel/rtlil.h
index f0ddb3927..6d3558621 100644
--- a/kernel/rtlil.h
+++ b/kernel/rtlil.h
@@ -780,7 +780,7 @@ public:
 	RTLIL::Const extract(int offset, int len = 1, RTLIL::State padding = RTLIL::State::S0) const;
 
 	// find the MSB without redundant leading bits
-	size_t get_min_size(bool is_signed) const;
+	int get_min_size(bool is_signed) const;
 
 	// compress representation to the minimum required bits
 	void compress(bool is_signed = false);
diff --git a/passes/fsm/fsm_map.cc b/passes/fsm/fsm_map.cc
index 02ce7f496..711a81db2 100644
--- a/passes/fsm/fsm_map.cc
+++ b/passes/fsm/fsm_map.cc
@@ -54,7 +54,7 @@ static void implement_pattern_cache(RTLIL::Module *module, std::map<RTLIL::Const
 		RTLIL::Const pattern = it.first;
 		RTLIL::SigSpec eq_sig_a, eq_sig_b, or_sig;
 
-		for (size_t j = 0; j < pattern.size(); j++)
+		for (auto j = 0; j < pattern.size(); j++)
 			if (pattern[j] == RTLIL::State::S0 || pattern[j] == RTLIL::State::S1) {
 				eq_sig_a.append(ctrl_in.extract(j, 1));
 				eq_sig_b.append(RTLIL::SigSpec(pattern[j]));
@@ -198,7 +198,7 @@ static void map_fsm(RTLIL::Cell *fsm_cell, RTLIL::Module *module)
 		RTLIL::Const state = fsm_data.state_table[i];
 		RTLIL::SigSpec sig_a, sig_b;
 
-		for (size_t j = 0; j < state.size(); j++)
+		for (auto j = 0; j < state.size(); j++)
 			if (state[j] == RTLIL::State::S0 || state[j] == RTLIL::State::S1) {
 				sig_a.append(RTLIL::SigSpec(state_wire, j));
 				sig_b.append(RTLIL::SigSpec(state[j]));
@@ -261,7 +261,7 @@ static void map_fsm(RTLIL::Cell *fsm_cell, RTLIL::Module *module)
 			for (size_t i = 0; i < fsm_data.state_table.size(); i++) {
 				RTLIL::Const state = fsm_data.state_table[i];
 				int bit_idx = -1;
-				for (size_t j = 0; j < state.size(); j++)
+				for (auto j = 0; j < state.size(); j++)
 					if (state[j] == RTLIL::State::S1)
 						bit_idx = j;
 				if (bit_idx >= 0)
diff --git a/techlibs/quicklogic/ql_dsp_simd.cc b/techlibs/quicklogic/ql_dsp_simd.cc
index 47b343dad..b42823d8b 100644
--- a/techlibs/quicklogic/ql_dsp_simd.cc
+++ b/techlibs/quicklogic/ql_dsp_simd.cc
@@ -60,7 +60,7 @@ struct QlDspSimdPass : public Pass {
 
 	// ..........................................
 
-	const size_t m_ModeBitsSize = 80;
+	const int m_ModeBitsSize = 80;
 
 	// DSP parameters
 	const std::vector<std::string> m_DspParams = {"COEFF_3", "COEFF_2", "COEFF_1", "COEFF_0"};