[swift-dev] IRGen's swift_rt_* functions

[Michael Gottesman]

> On Apr 25, 2017, at 11:24 AM, Roman Levenstein via swift-dev <swift-dev at swift.org> wrote:
> 
> 
>> On Apr 25, 2017, at 11:18 AM, Jordan Rose <jordan_rose at apple.com> wrote:
>> 
>> I believe these are interposition points for things like dtrace, and also useful for Roman's experiments with nonatomic retain counting. Roman, do you know?
> 
> I had a chat with Slava yesterday and explained it to him. 
> 
> But basically, these are for the special calling convention to be used for invocation of often used runtime entry points (e.g. reference counting functions like swift_retain). This calling convention is not enabled by default yet. But the idea is that it provides more callee-saved registers thus giving the caller more registers that can be used without spilling them around the calls of such a runtime entry. And wrappers are required because otherwise dyld (the dynamic linker) in certain situations clobbers some of these callee-saved registers.

Can we document this in ./docs somewhere?

> 
> -Roman
> 
>> 
>> (JoeG would know too but he's on vacation.)
>> 
>> Jordan
>> 
>> 
>>> On Apr 24, 2017, at 17:15, Slava Pestov via swift-dev <swift-dev at swift.org> wrote:
>>> 
>>> Hi all,
>>> 
>>> Now that we’re using swiftcc, does IRGen still need to emit the swift_rt_* wrappers around runtime calls? They look like no-ops at this point since the runtime entry points themselves should be swiftcc with the callee save variant?
>>> 
>>> Slava
>>> _______________________________________________
>>> swift-dev mailing list
>>> swift-dev at swift.org
>>> https://lists.swift.org/mailman/listinfo/swift-dev
>> 
> 
> _______________________________________________
> swift-dev mailing list
> swift-dev at swift.org
> https://lists.swift.org/mailman/listinfo/swift-dev