On May 8, 2010, at 8:28 AM, James Bucanek <subscri...@gloaming.com>
wrote:
I'd like to point out that this is one of those counterintuitive
cases where more code is less.
The code
self = [super init];
if (self!=nil)
...
produces fewer machine instructions than
if ([super init]!=nil)
...
Weird, huh?
It might produce less code, it might not. If you're operating at the
ObjC level of abstraction and worrying about the codegen of self=
[super init], your priorities are out of order.
The compiler can save the instructions needed to preserve |self|
before calling [super init] and restoring it afterwards. Anyway,
I've disassembled this on several architectures and the code
produced by the preferred pattern is shorter, and therefor more
efficient, than trying to take a shortcut.
Since you'd better be assigning self anyway, self doesn't need to be
preserved past the call to [super init].
--Kyle Sluder
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