performance - Does LLVM convert Objective-C methods to inline functions?

Question

1. Does LLVM automatically convert Objective-C methods to inline functions when possible?

   (I.e., is it just as performant to create an Objective-C method for a block of code that you could otherwise paste inline?)

2. If LLVM doesn't perform this optimization, why not? If it does, (a) are there certain build settings I must set for this to happen? (b) How can I tell if an Objective-C method will be inlined?

Answer 1

No, because its impossible to know in the context of the Obj-C runtime if those kind of optimizations can be performed. The thing to remember is that Obj-C methods are invoked by a message send, these messages can come from more than just the [myObject doSomething] syntax.

Consider [obj performSelector:NSSelectorFromString(@"hello")] the fact that this can happen means that it would be impossible to ever inline any method.

There is also a chain of events that happens when a message is received by a class, these events can reroute, or even change the message that is being sent. This happens transparently underneath the message send.