+void free_load_expression(struct ir_load_expression *load_expression)
+{
+ struct ir_load_expression_op *exp_op;
+
+ if (!load_expression)
+ return;
+ exp_op = load_expression->child;
+ for (;;) {
+ struct ir_load_expression_op *prev_exp_op;
+
+ if (!exp_op)
+ break;
+ switch (exp_op->type) {
+ case IR_LOAD_EXPRESSION_GET_CONTEXT_ROOT:
+ case IR_LOAD_EXPRESSION_GET_APP_CONTEXT_ROOT:
+ case IR_LOAD_EXPRESSION_GET_PAYLOAD_ROOT:
+ case IR_LOAD_EXPRESSION_GET_INDEX:
+ case IR_LOAD_EXPRESSION_LOAD_FIELD:
+ break;
+ case IR_LOAD_EXPRESSION_GET_SYMBOL:
+ free(exp_op->u.symbol);
+ break;
+ }
+ prev_exp_op = exp_op;
+ exp_op = exp_op->next;
+ free(prev_exp_op);
+ }
+ free(load_expression);
+}
+
+/*
+ * Returns the first node of the chain, after initializing the next
+ * pointers.
+ */
+static
+struct filter_node *load_expression_get_forward_chain(struct filter_node *node)
+{
+ struct filter_node *prev_node;
+
+ for (;;) {
+ assert(node->type == NODE_EXPRESSION);
+ prev_node = node;
+ node = node->u.expression.prev;
+ if (!node) {
+ break;
+ }
+ node->u.expression.next = prev_node;
+ }
+ return prev_node;
+}
+
+static
+struct ir_load_expression *create_load_expression(struct filter_node *node)
+{
+ struct ir_load_expression *load_exp;
+ struct ir_load_expression_op *load_exp_op, *prev_op;
+ char *str;
+
+ /* Get forward chain. */
+ node = load_expression_get_forward_chain(node);
+ if (!node)
+ return NULL;
+ load_exp = calloc(sizeof(struct ir_load_expression), 1);
+ if (!load_exp)
+ return NULL;
+
+ /* Root */
+ load_exp_op = calloc(sizeof(struct ir_load_expression_op), 1);
+ if (!load_exp_op)
+ goto error;
+ load_exp->child = load_exp_op;
+ str = node->u.expression.u.string;
+ if (!strcmp(str, "$ctx")) {
+ load_exp_op->type = IR_LOAD_EXPRESSION_GET_CONTEXT_ROOT;
+ node = node->u.expression.next;
+ if (!node) {
+ fprintf(stderr, "[error] Expecting identifier after \'%s\'\n", str);
+ goto error;
+ }
+ str = node->u.expression.u.string;
+ } else if (!strcmp(str, "$app")) {
+ load_exp_op->type = IR_LOAD_EXPRESSION_GET_APP_CONTEXT_ROOT;
+ node = node->u.expression.next;
+ if (!node) {
+ fprintf(stderr, "[error] Expecting identifier after \'%s\'\n", str);
+ goto error;
+ }
+ str = node->u.expression.u.string;
+ } else if (str[0] == '$') {
+ fprintf(stderr, "[error] Unexpected identifier \'%s\'\n", str);
+ goto error;
+ } else {
+ load_exp_op->type = IR_LOAD_EXPRESSION_GET_PAYLOAD_ROOT;
+ }
+
+ for (;;) {
+ struct filter_node *bracket_node;
+
+ prev_op = load_exp_op;
+ load_exp_op = calloc(sizeof(struct ir_load_expression_op), 1);
+ if (!load_exp_op)
+ goto error;
+ prev_op->next = load_exp_op;
+ load_exp_op->type = IR_LOAD_EXPRESSION_GET_SYMBOL;
+ load_exp_op->u.symbol = strdup(str);
+ if (!load_exp_op->u.symbol)
+ goto error;
+
+ /* Explore brackets from current node. */
+ for (bracket_node = node->u.expression.next_bracket;
+ bracket_node != NULL;
+ bracket_node = bracket_node->u.expression.next_bracket) {
+ prev_op = load_exp_op;
+ load_exp_op = calloc(sizeof(struct ir_load_expression_op), 1);
+ if (!load_exp_op)
+ goto error;
+ prev_op->next = load_exp_op;
+ load_exp_op->type = IR_LOAD_EXPRESSION_GET_INDEX;
+ load_exp_op->u.index = bracket_node->u.expression.u.constant;
+ }
+ /* Go to next chain element. */
+ node = node->u.expression.next;
+ if (!node)
+ break;
+ str = node->u.expression.u.string;
+ }
+ /* Add final load field */
+ prev_op = load_exp_op;
+ load_exp_op = calloc(sizeof(struct ir_load_expression_op), 1);
+ if (!load_exp_op)
+ goto error;
+ prev_op->next = load_exp_op;
+ load_exp_op->type = IR_LOAD_EXPRESSION_LOAD_FIELD;
+ return load_exp;
+
+error:
+ free_load_expression(load_exp);
+ return NULL;
+}
+
+static
+struct ir_op *make_op_load_expression(struct filter_node *node,
+ enum ir_side side)