From 6fcbc79b5c53c85dfbf37eba6ef8d8b3f7f7b1c7 Mon Sep 17 00:00:00 2001
From: Clifford Wolf <clifford@clifford.at>
Date: Wed, 6 Nov 2013 20:50:53 +0100
Subject: Improved width extension with regard to undef propagation

---
 frontends/ast/genrtlil.cc  |  69 ++++++++++++++++---
 kernel/calc.cc             | 161 +++++++++++++++++++++++++++------------------
 kernel/satgen.h            |   6 +-
 techlibs/common/stdcells.v |  22 +++----
 4 files changed, 171 insertions(+), 87 deletions(-)

diff --git a/frontends/ast/genrtlil.cc b/frontends/ast/genrtlil.cc
index b8bd2bff..d32b4434 100644
--- a/frontends/ast/genrtlil.cc
+++ b/frontends/ast/genrtlil.cc
@@ -83,6 +83,56 @@ static RTLIL::SigSpec uniop2rtlil(AstNode *that, std::string type, int result_wi
 	return sig;
 }
 
+// helper function for extending bit width (preferred over SigSpec::extend() because of correct undef propagation in ConstEval)
+static void widthExtend(AstNode *that, RTLIL::SigSpec &sig, int width, bool is_signed)
+{
+	if (width <= sig.width) {
+		sig.extend(width, is_signed);
+		return;
+	}
+
+	std::stringstream sstr;
+	sstr << "$extend" << "$" << that->filename << ":" << that->linenum << "$" << (RTLIL::autoidx++);
+
+	RTLIL::Cell *cell = new RTLIL::Cell;
+	cell->attributes["\\src"] = stringf("%s:%d", that->filename.c_str(), that->linenum);
+	cell->name = sstr.str();
+	cell->type = "$pos";
+	current_module->cells[cell->name] = cell;
+
+	RTLIL::Wire *wire = new RTLIL::Wire;
+	wire->attributes["\\src"] = stringf("%s:%d", that->filename.c_str(), that->linenum);
+	wire->name = cell->name + "_Y";
+	wire->width = width;
+	current_module->wires[wire->name] = wire;
+
+	RTLIL::SigChunk chunk;
+	chunk.wire = wire;
+	chunk.width = wire->width;
+	chunk.offset = 0;
+
+	RTLIL::SigSpec new_sig;
+	new_sig.chunks.push_back(chunk);
+	new_sig.width = chunk.width;
+
+	if (that != NULL)
+		for (auto &attr : that->attributes) {
+			if (attr.second->type != AST_CONSTANT)
+				log_error("Attribute `%s' with non-constant value at %s:%d!\n",
+						attr.first.c_str(), that->filename.c_str(), that->linenum);
+			cell->attributes[attr.first].str = attr.second->str;
+			cell->attributes[attr.first].bits = attr.second->bits;
+		}
+
+	cell->parameters["\\A_SIGNED"] = RTLIL::Const(is_signed);
+	cell->parameters["\\A_WIDTH"] = RTLIL::Const(sig.width);
+	cell->connections["\\A"] = sig;
+
+	cell->parameters["\\Y_WIDTH"] = width;
+	cell->connections["\\Y"] = new_sig;
+	sig = new_sig;
+}
+
 // helper function for creating RTLIL code for binary operations
 static RTLIL::SigSpec binop2rtlil(AstNode *that, std::string type, int result_width, const RTLIL::SigSpec &left, const RTLIL::SigSpec &right)
 {
@@ -943,7 +993,7 @@ RTLIL::SigSpec AstNode::genRTLIL(int width_hint, bool sign_hint)
 			int width = arg.width;
 			if (width_hint > 0) {
 				width = width_hint;
-				arg.extend(width, is_signed);
+				widthExtend(this, arg, width, is_signed);
 			}
 			return uniop2rtlil(this, type_name, width, arg);
 		}
@@ -972,7 +1022,7 @@ RTLIL::SigSpec AstNode::genRTLIL(int width_hint, bool sign_hint)
 	if (0) { case AST_REDUCE_XNOR: type_name = "$reduce_xnor"; }
 		{
 			RTLIL::SigSpec arg = children[0]->genRTLIL();
-			RTLIL::SigSpec sig = uniop2rtlil(this, type_name, 1, arg);
+			RTLIL::SigSpec sig = uniop2rtlil(this, type_name, std::max(width_hint, 1), arg);
 			return sig;
 		}
 
@@ -981,7 +1031,7 @@ RTLIL::SigSpec AstNode::genRTLIL(int width_hint, bool sign_hint)
 	if (0) { case AST_REDUCE_BOOL:  type_name = "$reduce_bool"; }
 		{
 			RTLIL::SigSpec arg = children[0]->genRTLIL();
-			RTLIL::SigSpec sig = arg.width > 1 ? uniop2rtlil(this, type_name, 1, arg) : arg;
+			RTLIL::SigSpec sig = arg.width > 1 ? uniop2rtlil(this, type_name, std::max(width_hint, 1), arg) : arg;
 			return sig;
 		}
 
@@ -1008,12 +1058,13 @@ RTLIL::SigSpec AstNode::genRTLIL(int width_hint, bool sign_hint)
 	if (0) { case AST_GE: type_name = "$ge"; }
 	if (0) { case AST_GT: type_name = "$gt"; }
 		{
+			int width = std::max(width_hint, 1);
 			width_hint = -1, sign_hint = true;
 			children[0]->detectSignWidthWorker(width_hint, sign_hint);
 			children[1]->detectSignWidthWorker(width_hint, sign_hint);
 			RTLIL::SigSpec left = children[0]->genRTLIL(width_hint, sign_hint);
 			RTLIL::SigSpec right = children[1]->genRTLIL(width_hint, sign_hint);
-			RTLIL::SigSpec sig = binop2rtlil(this, type_name, 1, left, right);
+			RTLIL::SigSpec sig = binop2rtlil(this, type_name, width, left, right);
 			return sig;
 		}
 
@@ -1054,14 +1105,14 @@ RTLIL::SigSpec AstNode::genRTLIL(int width_hint, bool sign_hint)
 		{
 			RTLIL::SigSpec left = children[0]->genRTLIL();
 			RTLIL::SigSpec right = children[1]->genRTLIL();
-			return binop2rtlil(this, type_name, 1, left, right);
+			return binop2rtlil(this, type_name, std::max(width_hint, 1), left, right);
 		}
 
 	// generate cells for unary operations: $logic_not
 	case AST_LOGIC_NOT:
 		{
 			RTLIL::SigSpec arg = children[0]->genRTLIL();
-			return uniop2rtlil(this, "$logic_not", 1, arg);
+			return uniop2rtlil(this, "$logic_not", std::max(width_hint, 1), arg);
 		}
 
 	// generate multiplexer for ternary operator (aka ?:-operator)
@@ -1079,8 +1130,8 @@ RTLIL::SigSpec AstNode::genRTLIL(int width_hint, bool sign_hint)
 
 			int width = std::max(val1.width, val2.width);
 			is_signed = children[1]->is_signed && children[2]->is_signed;
-			val1.extend(width, is_signed);
-			val2.extend(width, is_signed);
+			widthExtend(this, val1, width, is_signed);
+			widthExtend(this, val2, width, is_signed);
 
 			return mux2rtlil(this, cond, val1, val2);
 		}
@@ -1271,7 +1322,7 @@ RTLIL::SigSpec AstNode::genWidthRTLIL(int width, RTLIL::SigSpec *subst_from,  RT
 	genRTLIL_subst_to = backup_subst_to;
 
 	if (width >= 0)
-		sig.extend(width, is_signed);
+		widthExtend(this, sig, width, is_signed);
 
 	return sig;
 }
diff --git a/kernel/calc.cc b/kernel/calc.cc
index f2cbd6f4..6b4c50d5 100644
--- a/kernel/calc.cc
+++ b/kernel/calc.cc
@@ -17,10 +17,22 @@
  *
  */
 
+#include "kernel/log.h"
 #include "kernel/rtlil.h"
 #include "libs/bigint/BigIntegerLibrary.hh"
 #include <assert.h>
 
+static void extend(RTLIL::Const &arg, int width, bool is_signed)
+{
+	RTLIL::State padding = RTLIL::State::S0;
+
+	if (arg.bits.size() > 0 && (is_signed || arg.bits.back() > RTLIL::State::S1))
+		padding = arg.bits.back();
+
+	while (int(arg.bits.size()) < width)
+		arg.bits.push_back(padding);
+}
+
 static BigInteger const2big(const RTLIL::Const &val, bool as_signed, int &undef_bit_pos)
 {
 	BigInteger result = 0, this_bit = 1;
@@ -105,8 +117,7 @@ RTLIL::Const RTLIL::const_not(const RTLIL::Const &arg1, const RTLIL::Const&, boo
 		result_len = arg1.bits.size();
 
 	RTLIL::Const arg1_ext = arg1;
-	while (int(arg1_ext.bits.size()) < result_len)
-		arg1_ext.bits.push_back(signed1 && arg1_ext.bits.size() ? arg1_ext.bits.back() : RTLIL::State::S0);
+	extend(arg1_ext, result_len, signed1);
 
 	RTLIL::Const result(RTLIL::State::Sx, result_len);
 	for (size_t i = 0; i < size_t(result_len); i++) {
@@ -127,11 +138,8 @@ static RTLIL::Const logic_wrapper(RTLIL::State(*logic_func)(RTLIL::State, RTLIL:
 	if (result_len < 0)
 		result_len = std::max(arg1.bits.size(), arg2.bits.size());
 
-	while (int(arg1.bits.size()) < result_len)
-		arg1.bits.push_back(signed1 && arg1.bits.size() ? arg1.bits.back() : RTLIL::State::S0);
-
-	while (int(arg2.bits.size()) < result_len)
-		arg2.bits.push_back(signed2 && arg2.bits.size() ? arg2.bits.back() : RTLIL::State::S0);
+	extend(arg1, result_len, signed1);
+	extend(arg2, result_len, signed2);
 
 	RTLIL::Const result(RTLIL::State::Sx, result_len);
 	for (size_t i = 0; i < size_t(result_len); i++) {
@@ -163,86 +171,90 @@ RTLIL::Const RTLIL::const_xnor(const RTLIL::Const &arg1, const RTLIL::Const &arg
 	return logic_wrapper(logic_xnor, arg1, arg2, signed1, signed2, result_len);
 }
 
-static RTLIL::Const logic_reduce_wrapper(RTLIL::State initial, RTLIL::State(*logic_func)(RTLIL::State, RTLIL::State), const RTLIL::Const &arg1)
+static RTLIL::Const logic_reduce_wrapper(RTLIL::State initial, RTLIL::State(*logic_func)(RTLIL::State, RTLIL::State), const RTLIL::Const &arg1, int result_len)
 {
 	RTLIL::State temp = initial;
 
 	for (size_t i = 0; i < arg1.bits.size(); i++)
 		temp = logic_func(temp, arg1.bits[i]);
 
-	return RTLIL::Const(temp);
+	RTLIL::Const result(temp);
+	while (int(result.bits.size()) < result_len)
+		result.bits.push_back(RTLIL::State::S0);
+	return result;
 }
 
-RTLIL::Const RTLIL::const_reduce_and(const RTLIL::Const &arg1, const RTLIL::Const&, bool, bool, int)
+RTLIL::Const RTLIL::const_reduce_and(const RTLIL::Const &arg1, const RTLIL::Const&, bool, bool, int result_len)
 {
-	return logic_reduce_wrapper(RTLIL::State::S1, logic_and, arg1);
+	return logic_reduce_wrapper(RTLIL::State::S1, logic_and, arg1, result_len);
 }
 
-RTLIL::Const RTLIL::const_reduce_or(const RTLIL::Const &arg1, const RTLIL::Const&, bool, bool, int)
+RTLIL::Const RTLIL::const_reduce_or(const RTLIL::Const &arg1, const RTLIL::Const&, bool, bool, int result_len)
 {
-	return logic_reduce_wrapper(RTLIL::State::S0, logic_or, arg1);
+	return logic_reduce_wrapper(RTLIL::State::S0, logic_or, arg1, result_len);
 }
 
-RTLIL::Const RTLIL::const_reduce_xor(const RTLIL::Const &arg1, const RTLIL::Const&, bool, bool, int)
+RTLIL::Const RTLIL::const_reduce_xor(const RTLIL::Const &arg1, const RTLIL::Const&, bool, bool, int result_len)
 {
-	return logic_reduce_wrapper(RTLIL::State::S0, logic_xor, arg1);
+	return logic_reduce_wrapper(RTLIL::State::S0, logic_xor, arg1, result_len);
 }
 
-RTLIL::Const RTLIL::const_reduce_xnor(const RTLIL::Const &arg1, const RTLIL::Const&, bool, bool, int)
+RTLIL::Const RTLIL::const_reduce_xnor(const RTLIL::Const &arg1, const RTLIL::Const&, bool, bool, int result_len)
 {
-	RTLIL::Const not_y = logic_reduce_wrapper(RTLIL::State::S0, logic_xor, arg1);
-	if (not_y.bits.front() == RTLIL::State::S0) return RTLIL::State::S1;
-	if (not_y.bits.front() == RTLIL::State::S1) return RTLIL::State::S0;
-	return RTLIL::State::Sx;
+	RTLIL::Const buffer = logic_reduce_wrapper(RTLIL::State::S0, logic_xor, arg1, result_len);
+	if (!buffer.bits.empty()) {
+		if (buffer.bits.front() == RTLIL::State::S0)
+			buffer.bits.front() = RTLIL::State::S1;
+		else if (buffer.bits.front() == RTLIL::State::S1)
+			buffer.bits.front() = RTLIL::State::S0;
+	}
+	return buffer;
 }
 
-RTLIL::Const RTLIL::const_reduce_bool(const RTLIL::Const &arg1, const RTLIL::Const&, bool, bool, int)
+RTLIL::Const RTLIL::const_reduce_bool(const RTLIL::Const &arg1, const RTLIL::Const&, bool, bool, int result_len)
 {
-	return logic_reduce_wrapper(RTLIL::State::S0, logic_or, arg1);
+	return logic_reduce_wrapper(RTLIL::State::S0, logic_or, arg1, result_len);
 }
 
-RTLIL::Const RTLIL::const_logic_not(const RTLIL::Const &arg1, const RTLIL::Const&, bool signed1, bool, int)
+RTLIL::Const RTLIL::const_logic_not(const RTLIL::Const &arg1, const RTLIL::Const&, bool signed1, bool, int result_len)
 {
 	int undef_bit_pos_a = -1;
 	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);
 
-	if (a.isZero()) {
-		if (undef_bit_pos_a >= 0)
-			return RTLIL::Const(RTLIL::State::Sx);
-		return RTLIL::Const(RTLIL::State::S1);
-	}
-
-	return RTLIL::Const(RTLIL::State::S0);
+	while (int(result.bits.size()) < result_len)
+		result.bits.push_back(RTLIL::State::S0);
+	return result;
 }
 
-RTLIL::Const RTLIL::const_logic_and(const RTLIL::Const &arg1, const RTLIL::Const &arg2, bool signed1, bool signed2, int)
+RTLIL::Const RTLIL::const_logic_and(const RTLIL::Const &arg1, const RTLIL::Const &arg2, bool signed1, bool signed2, int result_len)
 {
 	int undef_bit_pos_a = -1, undef_bit_pos_b = -1;
 	BigInteger a = const2big(arg1, signed1, undef_bit_pos_a);
 	BigInteger b = const2big(arg2, signed2, undef_bit_pos_b);
 
-	if (a.isZero() || b.isZero()) {
-		if (undef_bit_pos_a >= 0 && undef_bit_pos_b >= 0)
-			return RTLIL::Const(RTLIL::State::Sx);
-		return RTLIL::Const(RTLIL::State::S0);
-	}
+	RTLIL::State bit_a = a.isZero() ? undef_bit_pos_a >= 0 ? RTLIL::State::Sx : RTLIL::State::S0 : RTLIL::State::S1;
+	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));
 
-	return RTLIL::Const(RTLIL::State::S1);
+	while (int(result.bits.size()) < result_len)
+		result.bits.push_back(RTLIL::State::S0);
+	return result;
 }
 
-RTLIL::Const RTLIL::const_logic_or(const RTLIL::Const &arg1, const RTLIL::Const &arg2, bool signed1, bool signed2, int)
+RTLIL::Const RTLIL::const_logic_or(const RTLIL::Const &arg1, const RTLIL::Const &arg2, bool signed1, bool signed2, int result_len)
 {
 	int undef_bit_pos_a = -1, undef_bit_pos_b = -1;
 	BigInteger a = const2big(arg1, signed1, undef_bit_pos_a);
 	BigInteger b = const2big(arg2, signed2, undef_bit_pos_b);
 
-	if (a.isZero() && b.isZero()) {
-		if (undef_bit_pos_a >= 0 || undef_bit_pos_b >= 0)
-			return RTLIL::Const(RTLIL::State::Sx);
-		return RTLIL::Const(RTLIL::State::S0);
-	}
+	RTLIL::State bit_a = a.isZero() ? undef_bit_pos_a >= 0 ? RTLIL::State::Sx : RTLIL::State::S0 : RTLIL::State::S1;
+	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));
 
-	return RTLIL::Const(RTLIL::State::S1);
+	while (int(result.bits.size()) < result_len)
+		result.bits.push_back(RTLIL::State::S0);
+	return result;
 }
 
 static RTLIL::Const const_shift(const RTLIL::Const &arg1, const RTLIL::Const &arg2, bool sign_ext, int direction, int result_len)
@@ -273,16 +285,14 @@ static RTLIL::Const const_shift(const RTLIL::Const &arg1, const RTLIL::Const &ar
 RTLIL::Const RTLIL::const_shl(const RTLIL::Const &arg1, const RTLIL::Const &arg2, bool signed1, bool, int result_len)
 {
 	RTLIL::Const arg1_ext = arg1;
-	while (int(arg1_ext.bits.size()) < result_len)
-		arg1_ext.bits.push_back(signed1 && arg1_ext.bits.size() ? arg1_ext.bits.back() : RTLIL::State::S0);
+	extend(arg1_ext, result_len, signed1);
 	return const_shift(arg1_ext, arg2, false, -1, result_len);
 }
 
 RTLIL::Const RTLIL::const_shr(const RTLIL::Const &arg1, const RTLIL::Const &arg2, bool signed1, bool, int result_len)
 {
 	RTLIL::Const arg1_ext = arg1;
-	while (int(arg1_ext.bits.size()) < result_len)
-		arg1_ext.bits.push_back(signed1 && arg1_ext.bits.size() ? arg1_ext.bits.back() : RTLIL::State::S0);
+	extend(arg1_ext, result_len, signed1);
 	return const_shift(arg1_ext, arg2, false, +1, result_len);
 }
 
@@ -300,46 +310,70 @@ RTLIL::Const RTLIL::const_sshr(const RTLIL::Const &arg1, const RTLIL::Const &arg
 	return const_shift(arg1, arg2, true, +1, result_len);
 }
 
-RTLIL::Const RTLIL::const_lt(const RTLIL::Const &arg1, const RTLIL::Const &arg2, bool signed1, bool signed2, int)
+RTLIL::Const RTLIL::const_lt(const RTLIL::Const &arg1, const RTLIL::Const &arg2, bool signed1, bool signed2, int result_len)
 {
 	int undef_bit_pos = -1;
 	bool y = const2big(arg1, signed1, undef_bit_pos) < const2big(arg2, signed2, undef_bit_pos);
-	return RTLIL::Const(undef_bit_pos >= 0 ? RTLIL::State::Sx : y ? RTLIL::State::S1 : RTLIL::State::S0);
+	RTLIL::Const result(undef_bit_pos >= 0 ? RTLIL::State::Sx : y ? RTLIL::State::S1 : RTLIL::State::S0);
+
+	while (int(result.bits.size()) < result_len)
+		result.bits.push_back(RTLIL::State::S0);
+	return result;
 }
 
-RTLIL::Const RTLIL::const_le(const RTLIL::Const &arg1, const RTLIL::Const &arg2, bool signed1, bool signed2, int)
+RTLIL::Const RTLIL::const_le(const RTLIL::Const &arg1, const RTLIL::Const &arg2, bool signed1, bool signed2, int result_len)
 {
 	int undef_bit_pos = -1;
 	bool y = const2big(arg1, signed1, undef_bit_pos) <= const2big(arg2, signed2, undef_bit_pos);
-	return RTLIL::Const(undef_bit_pos >= 0 ? RTLIL::State::Sx : y ? RTLIL::State::S1 : RTLIL::State::S0);
+	RTLIL::Const result(undef_bit_pos >= 0 ? RTLIL::State::Sx : y ? RTLIL::State::S1 : RTLIL::State::S0);
+
+	while (int(result.bits.size()) < result_len)
+		result.bits.push_back(RTLIL::State::S0);
+	return result;
 }
 
-RTLIL::Const RTLIL::const_eq(const RTLIL::Const &arg1, const RTLIL::Const &arg2, bool signed1, bool signed2, int)
+RTLIL::Const RTLIL::const_eq(const RTLIL::Const &arg1, const RTLIL::Const &arg2, bool signed1, bool signed2, int result_len)
 {
 	int undef_bit_pos = -1;
 	bool y = const2big(arg1, signed1, undef_bit_pos) == const2big(arg2, signed2, undef_bit_pos);
-	return RTLIL::Const(undef_bit_pos >= 0 ? RTLIL::State::Sx : y ? RTLIL::State::S1 : RTLIL::State::S0);
+	RTLIL::Const result(undef_bit_pos >= 0 ? RTLIL::State::Sx : y ? RTLIL::State::S1 : RTLIL::State::S0);
+
+	while (int(result.bits.size()) < result_len)
+		result.bits.push_back(RTLIL::State::S0);
+	return result;
 }
 
-RTLIL::Const RTLIL::const_ne(const RTLIL::Const &arg1, const RTLIL::Const &arg2, bool signed1, bool signed2, int)
+RTLIL::Const RTLIL::const_ne(const RTLIL::Const &arg1, const RTLIL::Const &arg2, bool signed1, bool signed2, int result_len)
 {
 	int undef_bit_pos = -1;
 	bool y = const2big(arg1, signed1, undef_bit_pos) != const2big(arg2, signed2, undef_bit_pos);
-	return RTLIL::Const(undef_bit_pos >= 0 ? RTLIL::State::Sx : y ? RTLIL::State::S1 : RTLIL::State::S0);
+	RTLIL::Const result(undef_bit_pos >= 0 ? RTLIL::State::Sx : y ? RTLIL::State::S1 : RTLIL::State::S0);
+
+	while (int(result.bits.size()) < result_len)
+		result.bits.push_back(RTLIL::State::S0);
+	return result;
 }
 
-RTLIL::Const RTLIL::const_ge(const RTLIL::Const &arg1, const RTLIL::Const &arg2, bool signed1, bool signed2, int)
+RTLIL::Const RTLIL::const_ge(const RTLIL::Const &arg1, const RTLIL::Const &arg2, bool signed1, bool signed2, int result_len)
 {
 	int undef_bit_pos = -1;
 	bool y = const2big(arg1, signed1, undef_bit_pos) >= const2big(arg2, signed2, undef_bit_pos);
-	return RTLIL::Const(undef_bit_pos >= 0 ? RTLIL::State::Sx : y ? RTLIL::State::S1 : RTLIL::State::S0);
+	RTLIL::Const result(undef_bit_pos >= 0 ? RTLIL::State::Sx : y ? RTLIL::State::S1 : RTLIL::State::S0);
+
+	while (int(result.bits.size()) < result_len)
+		result.bits.push_back(RTLIL::State::S0);
+	return result;
 }
 
-RTLIL::Const RTLIL::const_gt(const RTLIL::Const &arg1, const RTLIL::Const &arg2, bool signed1, bool signed2, int)
+RTLIL::Const RTLIL::const_gt(const RTLIL::Const &arg1, const RTLIL::Const &arg2, bool signed1, bool signed2, int result_len)
 {
 	int undef_bit_pos = -1;
 	bool y = const2big(arg1, signed1, undef_bit_pos) > const2big(arg2, signed2, undef_bit_pos);
-	return RTLIL::Const(undef_bit_pos >= 0 ? RTLIL::State::Sx : y ? RTLIL::State::S1 : RTLIL::State::S0);
+	RTLIL::Const result(undef_bit_pos >= 0 ? RTLIL::State::Sx : y ? RTLIL::State::S1 : RTLIL::State::S0);
+
+	while (int(result.bits.size()) < result_len)
+		result.bits.push_back(RTLIL::State::S0);
+	return result;
 }
 
 RTLIL::Const RTLIL::const_add(const RTLIL::Const &arg1, const RTLIL::Const &arg2, bool signed1, bool signed2, int result_len)
@@ -416,16 +450,15 @@ RTLIL::Const RTLIL::const_pow(const RTLIL::Const &arg1, const RTLIL::Const &arg2
 RTLIL::Const RTLIL::const_pos(const RTLIL::Const &arg1, const RTLIL::Const&, bool signed1, bool, int result_len)
 {
 	RTLIL::Const arg1_ext = arg1;
-	while (int(arg1_ext.bits.size()) < result_len)
-		arg1_ext.bits.push_back(signed1 && arg1_ext.bits.size() ? arg1_ext.bits.back() : RTLIL::State::S0);
+	extend(arg1_ext, result_len, signed1);
+
 	return arg1_ext;
 }
 
 RTLIL::Const RTLIL::const_neg(const RTLIL::Const &arg1, const RTLIL::Const&, bool signed1, bool, int result_len)
 {
 	RTLIL::Const arg1_ext = arg1;
-	while (int(arg1_ext.bits.size()) < result_len)
-		arg1_ext.bits.push_back(signed1 && arg1_ext.bits.size() ? arg1_ext.bits.back() : RTLIL::State::S0);
+	extend(arg1_ext, result_len, signed1);
 
 	RTLIL::Const zero(RTLIL::State::S0, 1);
 	return RTLIL::const_sub(zero, arg1_ext, false, signed1, result_len);
diff --git a/kernel/satgen.h b/kernel/satgen.h
index 27063776..6bd63360 100644
--- a/kernel/satgen.h
+++ b/kernel/satgen.h
@@ -187,7 +187,7 @@ struct SatGen
 			if (cell->type == "$logic_not")
 				ez->SET(ez->NOT(ez->expression(ez->OpOr, a)), y.at(0));
 			for (size_t i = 1; i < y.size(); i++)
-				ez->SET(0, y.at(0));
+				ez->SET(ez->FALSE, y.at(i));
 			return true;
 		}
 
@@ -200,7 +200,7 @@ struct SatGen
 			else
 				ez->SET(ez->expression(ez->OpOr, a, b), y.at(0));
 			for (size_t i = 1; i < y.size(); i++)
-				ez->SET(0, y.at(0));
+				ez->SET(ez->FALSE, y.at(i));
 			return true;
 		}
 
@@ -223,7 +223,7 @@ struct SatGen
 			if (cell->type == "$gt")
 				ez->SET(is_signed ? ez->vec_gt_signed(a, b) : ez->vec_gt_unsigned(a, b), y.at(0));
 			for (size_t i = 1; i < y.size(); i++)
-				ez->SET(0, y.at(0));
+				ez->SET(ez->FALSE, y.at(i));
 			return true;
 		}
 
diff --git a/techlibs/common/stdcells.v b/techlibs/common/stdcells.v
index 4bd1d39a..d89b39b8 100644
--- a/techlibs/common/stdcells.v
+++ b/techlibs/common/stdcells.v
@@ -245,7 +245,7 @@ parameter A_WIDTH = 1;
 parameter Y_WIDTH = 1;
 
 input [A_WIDTH-1:0] A;
-output Y;
+output [Y_WIDTH-1:0] Y;
 
 wire [A_WIDTH-1:0] buffer;
 
@@ -274,7 +274,7 @@ parameter A_WIDTH = 1;
 parameter Y_WIDTH = 1;
 
 input [A_WIDTH-1:0] A;
-output Y;
+output [Y_WIDTH-1:0] Y;
 
 wire [A_WIDTH-1:0] buffer;
 
@@ -303,7 +303,7 @@ parameter A_WIDTH = 1;
 parameter Y_WIDTH = 1;
 
 input [A_WIDTH-1:0] A;
-output Y;
+output [Y_WIDTH-1:0] Y;
 
 wire [A_WIDTH-1:0] buffer;
 
@@ -333,7 +333,7 @@ parameter A_WIDTH = 1;
 parameter Y_WIDTH = 1;
 
 input [A_WIDTH-1:0] A;
-output Y;
+output [Y_WIDTH-1:0] Y;
 
 wire [A_WIDTH-1:0] buffer;
 
@@ -365,7 +365,7 @@ parameter A_WIDTH = 1;
 parameter Y_WIDTH = 1;
 
 input [A_WIDTH-1:0] A;
-output Y;
+output [Y_WIDTH-1:0] Y;
 
 wire [A_WIDTH-1:0] buffer;
 
@@ -699,7 +699,7 @@ parameter WIDTH = A_WIDTH > B_WIDTH ? A_WIDTH : B_WIDTH;
 
 input [A_WIDTH-1:0] A;
 input [B_WIDTH-1:0] B;
-output Y;
+output [Y_WIDTH-1:0] Y;
 
 wire carry, carry_sign;
 wire [WIDTH-1:0] A_buf, B_buf, Y_buf;
@@ -748,7 +748,7 @@ parameter WIDTH = A_WIDTH > B_WIDTH ? A_WIDTH : B_WIDTH;
 
 input [A_WIDTH-1:0] A;
 input [B_WIDTH-1:0] B;
-output Y;
+output [Y_WIDTH-1:0] Y;
 
 wire carry, carry_sign;
 wire [WIDTH-1:0] A_buf, B_buf, Y_buf;
@@ -797,7 +797,7 @@ parameter WIDTH = A_WIDTH > B_WIDTH ? A_WIDTH : B_WIDTH;
 
 input [A_WIDTH-1:0] A;
 input [B_WIDTH-1:0] B;
-output Y;
+output [Y_WIDTH-1:0] Y;
 
 wire carry, carry_sign;
 wire [WIDTH-1:0] A_buf, B_buf;
@@ -822,7 +822,7 @@ parameter WIDTH = A_WIDTH > B_WIDTH ? A_WIDTH : B_WIDTH;
 
 input [A_WIDTH-1:0] A;
 input [B_WIDTH-1:0] B;
-output Y;
+output [Y_WIDTH-1:0] Y;
 
 wire carry, carry_sign;
 wire [WIDTH-1:0] A_buf, B_buf;
@@ -845,7 +845,7 @@ parameter Y_WIDTH = 1;
 
 input [A_WIDTH-1:0] A;
 input [B_WIDTH-1:0] B;
-output Y;
+output [Y_WIDTH-1:0] Y;
 
 \$le #(
 	.A_SIGNED(B_SIGNED),
@@ -872,7 +872,7 @@ parameter Y_WIDTH = 1;
 
 input [A_WIDTH-1:0] A;
 input [B_WIDTH-1:0] B;
-output Y;
+output [Y_WIDTH-1:0] Y;
 
 \$lt #(
 	.A_SIGNED(B_SIGNED),
-- 
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