rentzsch
part of me still wants to write [NSMutableArray array] instead of [NSMutableArray new] since maayybbeee this code will be MRC one day again
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@rentzsch grep for callerAcceptsFastAutorelease here: http://opensource.apple.com/source/objc4/objc4-532.2/runtime/NSObject.mm …
David Smith
turns out +[NSMutableArray array] and +[NSMutableArray new] should be near-equivalent in speed http://rentzsch.tumblr.com/post/75082194868/arcs-fast-autorelease … thanks @Catfish_Man
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@rentzsch@Catfish_Man That doesn’t explain the +[NSData date]/gettimeofday() special case, though. -
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@Catfish_Man@rentzsch There was something about calling gettimeofday() that messed up the normal tail call optimization? -
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@Catfish_Man@rentzsch Anything in particular that would cause the same problem with other POSIX API calls? -
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@Catfish_Man@mjtsai@rentzsch Write a test that runs otool to disassemble and verifies those functions do not end with `ret` or `bx lr`. -
@Catfish_Man@mjtsai@rentzsch Another idea: rdar://15951129 ER: Analyzer check for code that defeats ARC's autoreleased-return optimization - Show more
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@rentzsch@Catfish_Man shouldn't the last 2 autoreleaseReturnValue be retainAutoreleasedReturnValue in comment? -
@an0@Catfish_Man huh, I think you’re right.
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@rentzsch@catfish_man perf tidbit: I tried changing objc_retainAutoreleasedReturnValue to jump past the retain instead of setting a bit -
@rentzsch@catfish_man bah, I mean changed objc_autoreleaseReturnValue to jump past the call to objc_retainAutoreleasedReturnValue
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@rentzsch@catfish_man …but it was slower! My best theory was that it made branch prediction really unhappy. - View other replies
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@kongtomorrow@rentzsch I remember that! That’s still one of my favorite perf anecdotes :)
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@rentzsch@Catfish_Man this is just amazing!
Michael Tsai
Greg Parker
an0
Ken Ferry
Bartosz Ciechanowski
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