On Oct 7, 2009, at 9:53 AM, Derek Chesterfield wrote:
Just an aside, but does either syntax got optimised by the compiler (GCC or LLVM). Obviously it can't in all cases, but this seems an obvious case where it could be replaced by an assignment.
Message sends can never be optimized away by the compiler because a message send can always change behavior at runtime.
Given that foo.bar is synonymous with [foo bar], neither will ever be optimized by the compiler.
With Snow Leopard, the runtime does have a vtable based dispatch optimization. The 16 most common selectors, which compose approximately 70% to 85% of all method calls in a typical application, use the vtable optimization. The set of selectors is slightly different between GC and non-GC applications (because there is no point in optimizing retain/release/autorelease in the GC case; they are short circuited much earlier than actual dispatch).
Note that the vtable based dispatch is entirely transparent to your code. The only time you'll see it is if you try to invoke one of the optimized methods on a garbage object reference and cause objc_msgSend () to crash.
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