+# attr => "additional attribute arguments for constructor", # optional
+# init_attr => "emit attribute initialization template", # optional
+# rd_constructor => "c source code which constructs an ir_node", # optional
+# hash_func => "name of the hash function for this operation", # optional, get the default hash function else
+# latency => "latency of this operation (can be float)" # optional
+# attr_type => "name of the attribute struct", # optional