Whether any compiler "cleans this up" depends in the system's ABI; parameter calling conventions are not up to the compiler to decide (unless it can prove that

Whether any compiler "cleans this up" depends in the system's ABI; parameter calling conventions are not up to the compiler to decide (unless it can prove that a given function cannot be called from code it does not control). That said, yes, modern ABIs for modern machines usually pass single-element structures of primitive types in registers of the appropriate type. x86 (32-bit) is not modern in this sense: depending on the exact ABI used, these structures might well be passed on the stack or in an integer register.