I believe that these were in SILInstruction for historic reasons. This is a
separate API on top of SILInstruction so it makes sense to pull it out into its
own header.
Generally in the SIL/SILOptimizer libraries we have been putting kinds in the
swift namespace, not a nested scope in a type in swift (see ValueKind as an
example of this).
For example, strong_release may call a destructor. This information will be used e.g. by the escape analysis.
As destructors are potential calles now, FunctionOrder analysis will make sure that they will be scheduled for optimizations before their callers.
(Headers first)
It has been generally agreed that we need to do this reorg, and now
seems like the perfect time. Some major pass reorganization is in the
works.
This does not have to be the final word on the matter. The consensus
among those working on the code is that it's much better than what we
had and a better starting point for future bike shedding.
Note that the previous organization was designed to allow separate
analysis and optimization libraries. It turns out this is an
artificial distinction and not an important goal.
