> On Jan 4, 2016, at 11:07 AM, Jordan Rose via swift-dev <swift-dev@swift.org> > wrote: > Hi, Michael. The calling convention is equivalent to the 'unowned(unsafe)' > variant of 'unowned', so I don't think it's entirely unrelated. > > I don't like "Immediate" because I don't know what it means. Admittedly I > don't work on SIL, but when is something passed "immediate" as opposed to > "guaranteed"? Is "immediate" the case where it's valid now but mutating any > external memory could make it invalid?
Yes. > What makes that "immediate”? The name is used in SILGen when you’re going to use a value “immediately”, i.e. before any code executes that could possibly invalidate the reference. For example, the base expression of a load of a stored class property can be emitted as a +0 immediate r-value, because the caller is going to immediately project the property and load. That allows us to e.g. not retain after loading from a var; it’s a minor but frequently-impactful SILGen optimization. Anyway, I agree with Jordan that that name is not particularly appropriate for a parameter convention. This really just affects documentation and code within the compiler: it’s not actually written in textual SIL because it’s the default convention. Still, I’m fine with changing the name from “unowned”. Something that suggests the temporary nature of validity, maybe — “fleeting”? :) One consideration is that this is also the convention used for trivial values, although I suppose we could split that out (to “trivial”, which would of course be the default for trivial arguments) and maybe even always require an explicit convention on non-trivial arguments. John. _______________________________________________ swift-dev mailing list swift-dev@swift.org https://lists.swift.org/mailman/listinfo/swift-dev
