i’m also curious as to whether this would be faster as a member function on the
struct itself, since member functions get `self` as a pointer, right?
> On May 7, 2017, at 11:21 AM, Kelvin Ma <kelvin1...@gmail.com> wrote:
>
> So if I am passing the large struct to a large function, or a function that
> lives in a different module (as my project is currently split into 8 or 9
> modules — is that too many?), am I better off passing the members
> individually instead of passing the entire struct? It seems kind of tedious
> to have to write
>
> func f(x:Double, y:Double) -> Double
> {
> ....
> }
>
> let z:Double = f(x: point.x, y: point.y)
>
> instead, and it seems like something the compiler ought to be responsible for.
>
> Also about boxing the struct, isn’t that the worst of both worlds? You get
> the overhead of pass-by-value, the overhead of reference counting, the heap
> allocation, and the heap access. Plus it’s a lot of work to manually
> implement copy on write, and the copy is decided at runtime, even when it is
> known that an object will or won’t be mutated at compile time.
>
>> On Sun, May 7, 2017 at 12:43 AM, Daniel Dunbar <daniel_dun...@apple.com>
>> wrote:
>>
>>>> On May 6, 2017, at 10:39 PM, Brent Royal-Gordon <br...@architechies.com>
>>>> wrote:
>>>>
>>>> On May 6, 2017, at 10:34 PM, Daniel Dunbar via swift-users
>>>> <swift-users@swift.org> wrote:
>>>>
>>>> To answer Kelvin's question, yes, the optimizer will be able to see
>>>> through that code _assuming_ it can see the definition in a way it can
>>>> optimize
>>>
>>>
>>> Kelvin, you should definitely take Daniel's word over mine on whether
>>> there's an optimization for this. I believe the rest of my explanation is
>>> correct.
>>
>> Actually I think yours was more accurate... while it is is true the desired
>> optimization will often take effect (given the conditions I describe),
>> your's was correct that this isn't happening because the function signature
>> is taking _fewer_ arguments. Rather, the optimizations works because the
>> compiler will tend to inline that small function and then see it can discard
>> the unnecessary data.
>>
>> Whether or not this makes it worth boxing your struct to avoid large copies
>> probably depends on how much you need to pass the struct through call sites
>> which would in fact need to copy the full struct, versus inlining down to
>> something smaller.
>>
>> HTH,
>> - Daniel
>>
>>>
>>> --
>>> Brent Royal-Gordon
>>> Architechies
>>>
>>
>
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