2 files changed, 16 insertions, 3 deletions
diff --git a/kernel/rtlil.cc b/kernel/rtlil.cc
index a09f4a0d1..a5fbfeda4 100644
--- a/kernel/rtlil.cc
+++ b/kernel/rtlil.cc
@@ -1595,9 +1595,10 @@ void RTLIL::Module::remove(RTLIL::Cell *cell)
 	while (!cell->connections_.empty())
 		cell->unsetPort(cell->connections_.begin()->first);
 
-	log_assert(cells_.count(cell->name) != 0);
+	auto it = cells_.find(cell->name);
+	log_assert(it != cells_.end());
 	log_assert(refcount_cells_ == 0);
-	cells_.erase(cell->name);
+	cells_.erase(it);
 	delete cell;
 }
 
@@ -3437,7 +3438,7 @@ void RTLIL::SigSpec::extend_u0(int width, bool is_signed)
 
 	if (width_ < width) {
 		RTLIL::SigBit padding = width_ > 0 ? (*this)[width_ - 1] : RTLIL::State::Sx;
-		if (!is_signed)
+		if (padding != RTLIL::State::Sx && !is_signed)
 			padding = RTLIL::State::S0;
 		while (width_ < width)
 			append(padding);
diff --git a/kernel/rtlil.h b/kernel/rtlil.h
index 8509670ff..f4fcf5dcf 100644
--- a/kernel/rtlil.h
+++ b/kernel/rtlil.h
@@ -276,6 +276,18 @@ namespace RTLIL
 				return std::string(c_str() + pos, len);
 		}
 
+		bool begins_with(const char* prefix) const {
+			size_t len = strlen(prefix);
+			if (size() < len) return false;
+			return substr(0, len) == prefix;
+		}
+
+		bool ends_with(const char* suffix) const {
+			size_t len = strlen(suffix);
+			if (size() < len) return false;
+			return substr(size()-len) == suffix;
+		}
+
 		size_t size() const {
 			return str().size();
 		}