mem2reg to preserve user attributes and src

frontends/ast/simplify.cc

@@ -150,6 +150,10 @@ bool AstNode::simplify(bool const_fold, bool at_zero, bool in_lvalue, int stage,
 					reg->str = stringf("%s[%d]", node->str.c_str(), i);
 					reg->is_reg = true;
 					reg->is_signed = node->is_signed;
+					for (auto &it : node->attributes)
+						reg->attributes.emplace(it.first, it.second->clone());
+					reg->filename = node->filename;
+					reg->linenum = node->linenum;
 					children.push_back(reg);
 					while (reg->simplify(true, false, false, 1, -1, false, false)) { }
 				}