bring back bitfield sel skipping in irmemory.c

ir/ana/irmemory.c

@@ -432,6 +432,20 @@ ir_storage_class_class_t classify_pointer(const ir_node *irn,
 	return res;
 }
 
+static const ir_node *skip_bitfield_sels(const ir_node *adr)
+{
+	while (is_Sel(adr)) {
+		ir_entity *entity = get_Sel_entity(adr);
+		if (is_compound_type(get_entity_owner(entity)) &&
+			get_entity_bitfield_size(entity) > 0) {
+			adr = get_Sel_ptr(adr);
+		} else {
+			break;
+		}
+	}
+	return adr;
+}
+
 /**
  * Determine the alias relation between two addresses.
  *
@@ -548,6 +562,17 @@ static ir_alias_relation _get_alias_relation(
 			return ir_sure_alias;
 	}
 
+	 /*
+	  * Bitfields can be constructed as Sels from its base address.
+	  * As they have different entities, the disambiguator would find that they
+	  * are alias free. While this is true for its values, it is false for the
+	  * addresses (strictly speaking, the Sel's are NOT the addresses of the
+	  * bitfields).
+	  * So, skip those bitfield selecting Sel's.
+	  */
+	adr1 = skip_bitfield_sels(adr1);
+	adr2 = skip_bitfield_sels(adr2);
+
 	/* skip Sels */
 	const ir_node *base1 = adr1;
 	const ir_node *base2 = adr2;