diff --git a/frontends/ast/simplify.cc b/frontends/ast/simplify.cc
index 8555cb842aa..4bdb2f4ae0e 100644
--- a/frontends/ast/simplify.cc
+++ b/frontends/ast/simplify.cc
@@ -2830,10 +2830,10 @@ bool AstNode::simplify(bool const_fold, int stage, int width_hint, bool sign_hin
 			goto skip_dynamic_range_lvalue_expansion;
 
 		AST::AstNode *member_node = get_struct_member(children[0]);
-		int source_width = member_node ?
+		int wire_width = member_node ?
 			member_node->range_left - member_node->range_right + 1 :
 			children[0]->id2ast->range_left - children[0]->id2ast->range_right + 1;
-		int source_offset = children[0]->id2ast->range_right;
+		int wire_offset = children[0]->id2ast->range_right;
 		int result_width = 1;
 
 		AstNode *shift_expr = NULL;
@@ -2890,7 +2890,7 @@ bool AstNode::simplify(bool const_fold, int stage, int width_hint, bool sign_hin
 			else if (member_node)  // Member in packed struct/union
 			{
 				// Clamp chunk to range of member within struct/union.
-				log_assert(!source_offset && !children[0]->id2ast->range_swapped);
+				log_assert(!wire_offset && !children[0]->id2ast->range_swapped);
 
 				// When the (* nowrshmsk *) attribute is set, a CASE block is generated below
 				// to select the indexed bit slice. When a multirange array is indexed, the
@@ -2898,7 +2898,7 @@ bool AstNode::simplify(bool const_fold, int stage, int width_hint, bool sign_hin
 				// index dimension, and we can optimize the CASE block accordingly.
 				// The dimension of the original array expression is saved in the 'integer' field.
 				int dims = children[0]->integer;
-				stride = source_width;
+				stride = wire_width;
 				for (int dim = 0; dim < dims; dim++) {
 					stride /= get_struct_range_width(member_node, dim);
 				}
@@ -2924,9 +2924,9 @@ bool AstNode::simplify(bool const_fold, int stage, int width_hint, bool sign_hin
 
 			did_something = true;
 			newNode = new AstNode(AST_CASE, shift_expr);
-			for (int i = 1 - result_width; i < source_width; i++) {
+			for (int i = 1 - result_width; i < wire_width; i++) {
                                 // Out of range indexes are handled in genrtlil.cc
-				int start_bit = source_offset + i;
+				int start_bit = wire_offset + i;
 				int end_bit = start_bit + result_width - 1;
                                 // Check whether the current index can be generated by shift_expr.
 				if (start_bit < min_offset || start_bit > max_offset)
@@ -2949,14 +2949,14 @@ bool AstNode::simplify(bool const_fold, int stage, int width_hint, bool sign_hin
 		{
 			// mask and shift operations
 
-			AstNode *wire_mask = new AstNode(AST_WIRE, new AstNode(AST_RANGE, mkconst_int(source_width-1, true), mkconst_int(0, true)));
+			AstNode *wire_mask = new AstNode(AST_WIRE, new AstNode(AST_RANGE, mkconst_int(wire_width-1, true), mkconst_int(0, true)));
 			wire_mask->str = stringf("$bitselwrite$mask$%s:%d$%d", RTLIL::encode_filename(filename).c_str(), location.first_line, autoidx++);
 			wire_mask->set_attribute(ID::nosync, AstNode::mkconst_int(1, false));
 			wire_mask->is_logic = true;
 			while (wire_mask->simplify(true, 1, -1, false)) { }
 			current_ast_mod->children.push_back(wire_mask);
 
-			AstNode *wire_data = new AstNode(AST_WIRE, new AstNode(AST_RANGE, mkconst_int(source_width-1, true), mkconst_int(0, true)));
+			AstNode *wire_data = new AstNode(AST_WIRE, new AstNode(AST_RANGE, mkconst_int(wire_width-1, true), mkconst_int(0, true)));
 			wire_data->str = stringf("$bitselwrite$data$%s:%d$%d", RTLIL::encode_filename(filename).c_str(), location.first_line, autoidx++);
 			wire_data->set_attribute(ID::nosync, AstNode::mkconst_int(1, false));
 			wire_data->is_logic = true;
@@ -3012,12 +3012,12 @@ bool AstNode::simplify(bool const_fold, int stage, int width_hint, bool sign_hin
 			shamt = new AstNode(AST_TO_SIGNED, shamt);
 
 			// offset the shift amount by the lower bound of the dimension
-			int start_bit = source_offset;
+			int start_bit = wire_offset;
 			shamt = new AstNode(AST_SUB, shamt, mkconst_int(start_bit, true));
 
 			// reflect the shift amount if the dimension is swapped
 			if (children[0]->id2ast->range_swapped)
-				shamt = new AstNode(AST_SUB, mkconst_int(source_width - result_width, true), shamt);
+				shamt = new AstNode(AST_SUB, mkconst_int(wire_width - result_width, true), shamt);
 
 			// AST_SHIFT uses negative amounts for shifting left
 			shamt = new AstNode(AST_NEG, shamt);