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
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.
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.
The generality of the `AvailabilityContext` name made it seem like it
encapsulates more than it does. Really it just augments `VersionRange` with
additional set algebra operations that are useful for availability
computations. The `AvailabilityContext` name should be reserved for something
pulls together more than just a single version.
It is a way to indicate to the compiler that the line can't be reached.
On some configurations, it does happen to trap, as desired. Use a
function that always traps, since that's the intent.
The option to print #ifs defaulted to "on", but was disabled in most of
the actual compiler inputs that mattered, and the results weren't ever
actually used. Remove the option so we never print #ifs.
Some requirement machine work
Rename requirement to Value
Rename more things to Value
Fix integer checking for requirement
some docs and parser changes
Minor fixes
An `AvailabilityContext` represents an abstract version range in which
something is available. In the future, these version ranges may not necessarily
always correspond to operating system version ranges.
NFC.
In order for availability checks in iOS apps to be evaluated correctly when
running on macOS, the application binary must call a copy of
`_stdlib_isOSVersionAtLeast_AEIC()` that was emitted into the app, instead of
calling the `_stdlib_isOSVersionAtLeast()` function provided by the standard
library. This is because the call to the underlying compiler-rt function
`__isPlatformVersionAtLeast()` must be given the correct platform identifier
argument; if the call is not emitted into the client, then the macOS platform
identifier is used and the iOS version number will be mistakenly interpreted as
a macOS version number at runtime.
The `_stdlib_isOSVersionAtLeast()` function in the standard library is marked
`@_transparent` on iOS so that its call to `_stdlib_isOSVersionAtLeast_AEIC()`
is always inlined into the client. This works for the code generated by normal
`if #available` checks, but for the `@backDeployed` function thunks, the calls
to `_stdlib_isOSVersionAtLeast()` were not being inlined and that was causing
calls to `@backDeployed` functions to crash in iOS apps running on macOS since
their availability checks were being misevaluated.
The SIL optimizer has a heuristic which inhibits mandatory inlining in
functions that are classified as thunks, in order to save code size. This
heuristic needs to be relaxed in `@backDeployed` thunks, so that mandatory
inlining of `_stdlib_isOSVersionAtLeast()` can behave as expected. The change
should be safe since the only `@_transparent` function a `@backDeployed` thunk
is ever expected to call is `_stdlib_isOSVersionAtLeast()`.
Resolves rdar://134793410.
Also, move this rule from the computation of lowered captures in SIL,
to the computation of AST captures in Sema. This allows us to
correctly handle the case where an async function nests inside a
sync function. It also removes a special case that was added recently
to cope with a generic `self` type.
Fixes rdar://129366819.
When computing the available region, a forward walk is done from the
non-lifetime-ending boundary of the live region. That boundary consists
of (1) the target blocks of boundary edges, (2) dead defs, and (3) last
users which are non-consuming. This forward walk is done at the block
level, so neither the specific dead def (for (2)) nor specific last
non-consuming user (for (3)) is required to perform the walk; indeed
currently these are computed and then immediately used only to obtain
the blocks in which they appear and then discarded. Avoid computing the
specific dead defs and specific last non-consuming users by switching to
a lower-fidelity liveness boundary computation via
`PrunedLivenessBlockBoundary`.
To enable those clients which care only about _blocks_ whose
instructions or dead-defs make up the liveness boundary to avoid
iterating instruction lists, enhance boundary computation with a second
type (`PrunedLivenessBlockBoundary`) and migrate some methods from
liveness onto the boundary types to enable dispatching on the boundary
type to do only the amount of analysis that's necessary.
Instead of adding a "flag" (`m` in `...Tgm5`) make it more generic to allow to drop any unused argument.
Add all dropped arguments with a `t<n-1>` (where `<n-1>` is empty for n === 0). For example `...Ttt2g5`.
