<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body dir="auto"><div></div><div>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?</div><div><br>On May 7, 2017, at 11:21 AM, Kelvin Ma <<a href="mailto:kelvin13ma@gmail.com">kelvin13ma@gmail.com</a>> wrote:<br><br></div><blockquote type="cite"><div><div dir="ltr"><div><span style="font-family:monospace,monospace">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 <br><br>func f(x:Double, y:Double) -> Double <br>{<br> ....<br>}<br><br>let z:Double = f(x: point.x, y: point.y) <br><br>instead, and it seems like something the compiler ought to be responsible for.<br><br></span></div><span style="font-family:monospace,monospace">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. <br></span><div><div class="gmail_extra"><span style="font-family:monospace,monospace"><br></span><div class="gmail_quote"><span style="font-family:monospace,monospace">On Sun, May 7, 2017 at 12:43 AM, Daniel Dunbar <span dir="ltr"><<a href="mailto:daniel_dunbar@apple.com" target="_blank">daniel_dunbar@apple.com</a>></span> wrote:<br></span><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style="word-wrap:break-word"><span style="font-family:monospace,monospace"><br></span><div><span style="font-family:monospace,monospace"><span class=""><blockquote type="cite"><div>On May 6, 2017, at 10:39 PM, Brent Royal-Gordon <<a href="mailto:brent@architechies.com" target="_blank">brent@architechies.com</a>> wrote:</div><br class="m_8110348481390614979Apple-interchange-newline"><div><div style="word-wrap:break-word"><div><blockquote type="cite"><div>On May 6, 2017, at 10:34 PM, Daniel Dunbar via swift-users <<a href="mailto:swift-users@swift.org" target="_blank">swift-users@swift.org</a>> wrote:</div><br class="m_8110348481390614979Apple-interchange-newline"><div><span style="font-size:12px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;float:none;display:inline!important">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</span></div></blockquote></div><div><br></div><div>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.</div></div></div></blockquote><div><br></div></span></span><span style="font-family:monospace,monospace">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.</span></div><div><span style="font-family:monospace,monospace"><br></span></div><div><span style="font-family:monospace,monospace">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.</span></div><div><span style="font-family:monospace,monospace"><br></span></div><div><span style="font-family:monospace,monospace">HTH,</span></div><div><span style="font-family:monospace,monospace"> - Daniel</span></div><span style="font-family:monospace,monospace"><span class="HOEnZb"><font color="#888888"><div><br></div><div><blockquote type="cite"><div><div style="word-wrap:break-word"><br><div>
<span class="m_8110348481390614979Apple-style-span" style="border-collapse:separate;font-style:normal;font-variant-ligatures:normal;font-variant-caps:normal;font-variant-east-asian:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;border-spacing:0px"><div><div style="font-size:12px">-- </div><div style="font-size:12px">Brent Royal-Gordon</div><div style="font-size:12px">Architechies</div></div></span>
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