Specifically, we get an additional table like thing called sil_moveonlydeinit. It looks as follows:
sil_moveonlydeinit TYPE {
@FUNC_NAME
}
It always has a single entry.
It's not needed anymore with delayed instruction deletion.
It was used for two purposes:
1. For analysis, which cache instructions, to avoid dangling instruction pointers
2. For passes, which maintain worklists of instructions, to remove a deleted instructions from the worklist. This is now done by checking SILInstruction::isDeleted().
Previously SILModule contained two different pathways for the deserializer to
send notifications that it had created functions:
1. A list of function pointers that were called when a function's body was
deserialized. This was added recently so that access enforcement elimination is
run on newly deserialized SIL code if we have already eliminated access
enforcement from the module.
2. SILModule::SerializationCallback. This is an implementation of the full
callback interface and is used by the SILModule to update linkage and other
sorts of book keeping.
To fix the pass manager notification infrastructure, I need to be able to send
notifications to a SILPassManager when deserializing. I also need to be able to
eliminate these callbacks when a SILPassManager is destroyed. These requirements
are incompatible with the current two implementations since: (2) is an
implementation detail of SILModule and (1) only notifies on function bodies
being deserialized instead of the creation of new declarations (what the caller
analysis wants).
Rather than adding a third group of callbacks, this commit refactors the
infrastructure in such a way that all of these use cases can use one
implementation. This is done by:
1. Lifting the interface of SerializedSILLoader::Callback into a base
notification protocol for deserialization called
DeserializationNotificationHandlerBase and its base no-op implementation into an
implementation of the aforementioned protocol:
DeserializationNotificationHandler.
2. Changing SILModule::SerializationCallback to implement
DeserializationNotificationHandler.
3. Creating a class called FunctionBodyDeserializationNotificationHandler that
takes in a function pointer and uses that to just override the
didDeserializeFunctionBody. This eliminates the need for the specific function
body deserialization list.
4. Replacing the state associated with the two other pathways with a single
DeserializationNotificationHandlerSet class that contains a set of
DeserializationNotificationHandler and chains notifications to them. This set
implements DeserializationNotificationHandlerBase so we know that its
implementation will always be in sync with DeserializationNotificationHandler.
rdar://42301529
introduce a common superclass, SILNode.
This is in preparation for allowing instructions to have multiple
results. It is also a somewhat more elegant representation for
instructions that have zero results. Instructions that are known
to have exactly one result inherit from a class, SingleValueInstruction,
that subclasses both ValueBase and SILInstruction. Some care must be
taken when working with SILNode pointers and testing for equality;
please see the comment on SILNode for more information.
A number of SIL passes needed to be updated in order to handle this
new distinction between SIL values and SIL instructions.
Note that the SIL parser is now stricter about not trying to assign
a result value from an instruction (like 'return' or 'strong_retain')
that does not produce any.
This commit adds a hook that allows passes, analysis or data structures that can
be registered as receivers of delete notifications to decide if they want to
receive notifications All of the analysis and the currently executing passes are
automatically registered to receive notifications and this hook is useful in
reducing the runtime overhead. With this change the only analysis that accepts
notifications is alias analysis.
This commit adds the basic support for delete notification handlers. The SIL
Module is notified every time an instruction is deleted. The module will forward
notification messages to users who ask to be notified. The motivation for this
work is described in the upcoming commit to OptimizerDesign.md.
