diff --git a/frontends/ast/simplify.cc b/frontends/ast/simplify.cc
index 675882713d4..b08cd13b739 100644
--- a/frontends/ast/simplify.cc
+++ b/frontends/ast/simplify.cc
@@ -2333,28 +2333,22 @@ bool AstNode::simplify(bool const_fold, int stage, int width_hint, bool sign_hin
                     member_node->range_left - member_node->range_right + 1 :
                     id2ast->range_left - id2ast->range_right + 1;
 		int source_offset = id2ast->range_right;
-		int result_width = 1;
 
-		AstNode *shift_expr = NULL;
 		AstNode *range = children[0];
+		int result_width;
+		if (!try_determine_range_width(range, result_width))
+			input_error("Unsupported expression on dynamic range select on signal `%s'!\n", str.c_str());
+		AstNode *shift_expr = result_width == 1 ? range->children[0]->clone() : range->children[1]->clone();
 
-		if (range->children.size() == 1) {
-			shift_expr = range->children[0]->clone();
-		} else {
-			shift_expr = range->children[1]->clone();
-			if (!try_determine_range_width(range, result_width))
-				input_error("Unsupported expression on dynamic range select on signal `%s'!\n", str.c_str());
-		}
-
-		int shift_expr_width_hint = -1;
-		bool shift_expr_sign_hint = true;
+		int shift_expr_width_hint;
+		bool shift_expr_sign_hint;
 		shift_expr->detectSignWidth(shift_expr_width_hint, shift_expr_sign_hint);
 
 		bool use_case_method = false;
 
 		if (id2ast->attributes.count(ID::nordshift)) {
 			AstNode *node = id2ast->attributes.at(ID::nordshift);
-			while (node->simplify(true, false, stage, -1, false, false)) { }
+			while (node->simplify(true, stage, -1, false)) { }
 			if (node->type != AST_CONSTANT)
 				input_error("Non-constant value for `nordshift' attribute on `%s'!\n", id2ast->str.c_str());
 			if (node->asAttrConst().as_bool())
@@ -2367,7 +2361,7 @@ bool AstNode::simplify(bool const_fold, int stage, int width_hint, bool sign_hin
 			int stride = 1;
 			int div_stride = 1;
 
-			// Extract (index)*(width) from non_opt_range pattern (@selfsz@((index)*(width)))+(0)).
+			// Extract (index)*(width) from non_opt_range pattern ((@selfsz@((index)*(width)))+(0)).
 			AstNode *lsb_expr =
 				shift_expr->type == AST_ADD && shift_expr->children[0]->type == AST_SELFSZ &&
 				shift_expr->children[1]->type == AST_CONSTANT && shift_expr->children[1]->integer == 0 ?
@@ -2417,9 +2411,9 @@ bool AstNode::simplify(bool const_fold, int stage, int width_hint, bool sign_hin
 			AstNode *wire = new AstNode(AST_WIRE, new AstNode(AST_RANGE, node_int(result_width - 1), node_int(0)));
 			wire->str = stringf("$bitsel$%s$%s:%d$%d", str.c_str(), RTLIL::encode_filename(filename).c_str(), location.first_line, autoidx++);
 			if (current_block)
-				wire->attributes[ID::nosync] = AstNode::mkconst_int(1, false);
+				wire->set_attribute(ID::nosync, AstNode::mkconst_int(1, false));
 			wire->is_logic = true;
-			while (wire->simplify(true, false, 1, -1, false, false)) { }
+			while (wire->simplify(true, 1, -1, false)) { }
 			current_ast_mod->children.push_back(wire);
 
 			AstNode *lvalue = new AstNode(AST_IDENTIFIER);
@@ -2436,7 +2430,7 @@ bool AstNode::simplify(bool const_fold, int stage, int width_hint, bool sign_hin
 				AstNode *rvalue = clone();
 				rvalue->delete_children();
 				if (member_node)
-					rvalue->attributes[ID::wiretype] = member_node->clone();
+					rvalue->set_attribute(ID::wiretype, member_node->clone());
 				rvalue->children.push_back(new AstNode(AST_RANGE,
 						node_int(end_bit), node_int(start_bit)));
 				cond->children.push_back(new AstNode(AST_BLOCK, new AstNode(AST_ASSIGN_EQ, lvalue->clone(), rvalue)));
@@ -2461,7 +2455,7 @@ bool AstNode::simplify(bool const_fold, int stage, int width_hint, bool sign_hin
 			AstNode *rvalue = clone();
 			rvalue->delete_children();
 			if (member_node)
-				rvalue->attributes[ID::wiretype] = member_node->clone();
+				rvalue->set_attribute(ID::wiretype, member_node->clone());
 
 			if (!shift_expr_sign_hint && (source_offset || id2ast->range_swapped)) {
 				// convert to signed while preserving the sign and value
@@ -2470,6 +2464,7 @@ bool AstNode::simplify(bool const_fold, int stage, int width_hint, bool sign_hin
 								     node_int(shift_expr_width_hint + 1),
 								     shift_expr));
 			}
+
 			if (source_offset) {
 				// offset the shift amount by the lower bound of the dimension
 				shift_expr = new AstNode(AST_SUB, shift_expr, node_int(source_offset));