Motivated by need for protocol-based dynamic dispatch, which hasn't been possible in Embedded Swift due to a full ban on existentials. This lifts that restriction but only for class-bound existentials: Class-bound existentials are already (even in desktop Swift) much more lightweight than full existentials, as they don't need type metadata, their containers are typically 2 words only (reference + wtable pointer), don't incur copies (only retains+releases).
Included in this PR:
[x] Non-generic class-bound existentials, executable tests for those.
[x] Extension methods on protocols and using those from a class-bound existential.
[x] RuntimeEffects now differentiate between Existential and ExistentialClassBound.
[x] PerformanceDiagnostics don't flag ExistentialClassBound in Embedded Swift.
[x] WTables are generated in IRGen when needed.
Left for follow-up PRs:
[ ] Generic classes support
In this mode all C++ types are imported as unsafe by default. Users
explicitly marking types are escapable or not escapable can make them
imported as safe. In the future, we also want to import unannotated
functions as unsafe and add more logic to infer types that are actually
safe, like agregates of escapable types.
The reason why is that we want to distinguish inbetween SILFunction's that are
marked as unspecified by SILGen and those that are parsed from textual SIL that
do not have any specified isolation. This will make it easier to write nice
FileCheck tests against SILGen output on what is the inferred isolation for
various items.
NFCI.
ModuleDecl kept track of all of the source files in the module so that it
could find the source file containing a given location, which relied on
a sorted array all of these source files. SourceManager has its own
similar data structure for a similar query mapping the locations to
buffer IDs.
Replace ModuleDecl's dats structure with a use of the SourceManager's version
with the mapping from buffer IDs to source files.
The lifetimebound annotations are now imported as lifetime dependencies.
This works for basic cases but there are still some parts missing:
* Support lifeitmebound annotations on constructors
* A way to represent immortal/static lifetimes on the C++ side
`OpaqueReturnTypeParent` node now references the parent with a mangled parent name, rather than a parent pointer. This makes trees obtained from different demanglers (or calls to `Demangler::demangleSymbol`) for the same symbol equal.
Now that every source file has a buffer ID, introduce the reverse mapping
so clients can find the source file(s) in their module that reference
that buffer ID.
`swift::Decl` and its inheritors should be treated as foreign reference types in Swift, meaning pointers to them (`Decl*`) should be mapped to Swift classes. This can be done by applying `SWIFT_UNSAFE_REFERENCE` attribute to the `swift::Decl` types. However, at the moment these functions don't seem to be used from Swift, so this change just removes the `SWIFT_IMPORT_UNSAFE` attributes.
`SWIFT_IMPORT_UNSAFE` is an escape hatch that can be used to make the Swift compiler ignore its usual safety heuristics for C++ types.
`SILDebugLocation` is better described as a self-contained Swift type.
Similar to 35263ef9.
The "buffer ID" in a SourceFile, which is used to find the source file's
contents in the SourceManager, has always been optional. However, the
effectively every SourceFile actually does have a buffer ID, and the
vast majority of accesses to this information dereference the optional
without checking.
Update the handful of call sites that provided `nullopt` as the buffer
ID to provide a proper buffer instead. These were mostly unit tests
and testing programs, with a few places that passed a never-empty
optional through to the SourceFile constructor.
Then, remove optionality from the representation and accessors. It is
now the case that every SourceFile has a buffer ID, simplying a bunch
of code.
