external function_call_conv : llvalue -> int = "llvm_function_call_conv"
external set_function_call_conv : int -> llvalue -> unit
= "llvm_set_function_call_conv"
+external collector : llvalue -> string option = "llvm_collector"
+external set_collector : string option -> llvalue -> unit = "llvm_set_collector"
(* TODO: param attrs *)