[swift-evolution] Pitch: Cross-module inlining and specialization
spestov at apple.com
Wed Oct 4 00:18:17 CDT 2017
> On Oct 3, 2017, at 10:17 PM, Chris Lattner <clattner at nondot.org> wrote:
>> On Oct 3, 2017, at 10:15 PM, Slava Pestov <spestov at apple.com> wrote:
>>> On Oct 3, 2017, at 10:14 PM, Chris Lattner <clattner at nondot.org> wrote:
>>> On Oct 2, 2017, at 11:11 PM, Slava Pestov <spestov at apple.com> wrote:
>>>>> In any case, even if you’re opposed to these approaches, I’d love for the “alternatives considered” section to indicate what the objection is. I am really very concerned that you’re causing a keyword/attribute explosion and conceptual complexity by adding too many small things to individual parts of the language. We would ideally have a simple and holistic solution to resilience.
>>>> I agree with that keyword/attribute explosion is a concern. We also plan on submitting a proposal to add a @fixedContents attribute for structs (currently implemented as @_fixed_layout) which enables more efficient access patterns in resilient code, for example direct access of stored properties, at the cost of preventing new stored properties from being added in a binary-compatible manner. So we would have ‘nonexhaustive’ enums, @fixedContents structs, and @inlinable functions/properties/initializers.
>>> Yes, and then we’ll need something else for classes as well (*head explodes*).
>> FWIW, I was hoping we wouldn’t need to expose any such attribute for classes (or protocols) at all, because classes are already “slow” and anything we do to make them resilient doesn’t make things much “slower”. But that could change, of course.
> But everyone knows that NSObject is fixed size, right?
Yeah, but the compiler could handle NSObject as a special case. Are there enough other special cases that it is worth documenting and exposing a fragile attribute on classes to the user?
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