+/**
+ * Walker function, sets all phi list heads fields of visited Blocks
+ * to NULL.
+ * Use in conjunction with firm_collect_block_phis().
+ */
+void firm_clear_block_phis(ir_node *node, void *env);
+
+/**
+ * Walker function, links all visited Phi nodes into its block links.
+ * Use in conjunction with firm_clear_block_phis().
+ */
+void firm_collect_block_phis(ir_node *node, void *env);
+