On Mon, Apr 3, 2017 at 12:53 PM Ben Rimmington <[email protected]> wrote:
> <https://github.com/apple/swift/pull/8325> (Merged 10 days ago) > That's a relief! I thought I was losing my mind that such an obvious optimization had been left on the floor, especially when I also thought I remembered it working before. > > > On 3 Apr 2017, at 20:32, Charlie Monroe wrote: > > > >> On Apr 3, 2017, at 9:25 PM, Ben Rimmington wrote: > >> > >>> On 3 Apr 2017, at 17:55, Tony Allevato wrote: > >>> > >>> I just checked with -O and without and was surprised to find that `let > x = "abc" + "def" + "ghi"` wasn't collapsed into a single string literal > "abcdefghi" in the generated assembly code. Maybe it's more difficult than > it is in some other languages because of operator overloads and different > kinds of text literals (strings, extended grapheme clusters, Unicode > scalars)? > >> > >> Is this a regression since Swift 2.0 added the optimization? > > > > I'd say it's a regression since 3.0 since I remember testing the > optimizer even being able to put together this during compile time: > > > > struct URLString { > > let urlString: String > > > > init(host: String, path: String, query: String) { > > self.urlString = "http://"; + host + path + "?" + query > > } > > } > > > > URLString(host: "apple.com", path: "/mac", query: "target=imac") > > > > This produced a single string literal - I confirmed this using MachOView > on the final binary... > > > >> * Concatenation of Swift string literals, including across > multiple lines, is > >> now a guaranteed compile-time optimization, even at `-Onone`. > **(19125926)** > >> > >> < > https://github.com/apple/swift/blame/97db3931f2c5a21ea87ad6e71cdecbec325bff91/CHANGELOG.md#L1329-L1330 > > >
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