initialization in-place on demand. Initialize parent metadata
references correctly on struct and enum metadata.
Also includes several minor improvements related to relative
pointers that I was using before deciding to simply switch the
parent reference to an absolute reference to get better access
patterns.
We annotate the most popular runtime functions in terms of how often they are invoked from Swift code:
- Many variants of retain/release functions are annotated to use the new calling convention.
But those variants of retain/release functions that may result in calls of objc_retain or objc_release
are not migrated to the new calling convention, because it results in significant performance degradations
when objects of Obj-C derived classes are used.
- Some popular non-reference counting functions like swift_getGenericMetadata or swift_dynamicCast are annotated as well.
The list of these functions is pretty much the same as the the set of functions defined in InstrumentsSupport.h
These are basically the functions that can be intercepted by different tools/profilers/etc.
This new x-macro should be used to define a runtime function that has an internal implementation
inside the runtime library and a global symbol referring to this internal implementation.
An example of such a runtime function is "swift_retain", which has a global symbol "_swift_retain"
referring to its internal implementation "_swift_retain_".
