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.
This name makes it clear that the function has not yet been deleted and also
contrasts with the past tense used in the API notifyAddedOrModifiedFunction to
show that said function has already added/modified the function.
The name notifyAddFunction is actively harmful since the pass manager uses this
entrypoint to notify analyses of added *OR* modified functions. It is up to the
caller analysis to distinguish in between these cases.
I am not vouching for the design, just trying to make names match the
current behavior.
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).
@effects is too low a level, and not meant for general usage outside
the standard library. Therefore it deserves to be underscored like
other such attributes.
Make this a generic analysis so that it can be used to analyze any
kind of function effect.
FunctionSideEffect becomes a trivial specialization of the analysis.
The immediate need for this is to introduce an new
AccessedStorageAnalysis, although I foresee it as a generally very
useful utility. This way, new kinds of function effects can be
computed without adding any complexity or compile time to
FunctionSideEffects. We have the flexibility of computing different
kinds of function effects at different points in the pipeline.
In the case of AccessedStorageAnalysis, it will compute both
FunctionSideEffects and FunctionAccessedStorage in the same pass by
implementing a simple wrapper on top of FunctionEffects.
This cleanup reflects my feeling that nested classes make the code
extremely unreadable unless they are very small and either private or
only used directly via its parent class. It's easier to see how these
classes compose with a flat type system.
In addition to enabling new kinds of function effects analyses, I
think this makes the implementation of side effect analysis easier to
understand by separating concerns.
There are now separate functions for function addition and deletion instead of InvalidationKind::Function.
Also, there is a new function for witness/vtable invalidations.
rdar://problem/29311657
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.
