We don't have a great way to ensure that the current-global-actor hook
will get installed by the concurrency library with WebAssembly, so
temporarily work around the issue by relying on the fact that we also
aren't doing actual concurrency with WebAssembly.
Replace the pair of global actor type/conformance we are passing around with
a general "conformance execution context" that could grow new functionality
over time. Add three external symbols to the runtime:
* swift_conformsToProtocolWithExecutionContext: a conforms-to-protocol check
that also captures the execution context that should be checked before
using the conformance for anything. The only execution context right now
is for an isolated conformance.
* swift_isInConformanceExecutionContext: checks whether the function is
being executed in the given execution context, i.e., running on the
executor for the given global actor.
* swift_ConformanceExecutionContextSize: the size of the conformance
execution context. Client code outside of the Swift runtime can allocate
a pointer-aligned region of memory of this size to use with the runtime
functions above.
In the prior implementation of runtime resolution of isolated conformances,
the runtime had to look in both the protocol conformance descriptor and
in all conditional conformance requirements (recursively) to find any
isolated conformances. If it found one, it had to demangle the global
actor type to metadata. Since swift_conformsToProtocol is a hot path through
the runtime, we can't afford this non-constant-time work in the common
case.
Instead, cache the resolved global actor and witness table as part of the
conformance cache, so that we have access to this information every time
we look up a witness table for a conformance. Propagate this up through
various callers (e.g., generic requirement checking) to the point where
we either stash it in the cache or check it at runtime. This gets us down
to a very quick check (basically, NULL-or-not) for nonisolated conformances,
and just one check for isolated conformances.
Following the approach taken with the concurrency-specific type
descriptors, register a hook function for the "is current global actor"
check used for isolated conformances.
When establishing whether a given conformance is isolated, look through
the witness tables used to satisfy conditional requirements as well. This
is because an otherwise-nonisolated conditional conformance can become
isolated if one of its associated conformance requirements is satisfied
by an isolated conformance.
While here, make sure this code works with variadic generics, too.
Extend the metadata representation of protocol conformance descriptors
to include information about the global actor to which the conformance is
isolated (when there is one), as well as the conformance of that type to
the GlobalActor protocol. Emit this metadata whenever a conformance is
isolated.
When performing a conforms-to-protocol check at runtime, check whether
the conformance that was found is isolated. If so, extract the serial
executor for the global actor and check whether we are running on that
executor. If not, the conformance fails.
`Builtin.FixedArray<let N: Int, T: ~Copyable & ~Escapable>` has the layout of `N` elements of type `T` laid out
sequentially in memory (with the tail padding of every element occupied by the array). This provides a primitive
on which the standard library `Vector` type can be built.
The way that we include COMPATIBILITY_OVERRIDE_INCLUDE_PATH freaks out the
syntax highlighting of editors like emacs. It causes the whole file to be
highlighted like it is part of the include string.
To work around this, this patch creates a separate file called
CompatibilityOverrideIncludePath.h that just includes
COMPATIBILITY_OVERRIDE_INCLUDE_PATH. So its syntax highlighting is borked, but
at least in the actual files that contain real code, the syntax highlighting is
restored.
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
Track the key argument index separately from the generic parameter index when performing the invertible protocol checking in _checkGenericRequirements. This keeps the indexing correct when a non-key argument is followed by a key argument.
rdar://128774651
Emit metadata for runtime checks of conformances of associated types to
invertible protocols, e.g., `T.Assoc: Copyable`. This allows us to
correctly handle, e.g., dynamic casting involving conditional
conformances that have such constraints.
The model we use here is to emit an invertible-protocol constraint
that leaves only the specific bit clear in the invertible protocol
set.
Form a set of suppressed protocols for a function type based on
the extended flags (where future compilers can start recording
suppressible protocols) and the existing "noescape" bit. Compare
that against the "ignored" suppressible protocol requirements, as we
do for other types.
This involves a behavior change if any client has managed to evade the
static checking for noescape function types, but it's unlikely that
existing code has done so (and it was unsafe anyway).
Add more runtime support for checking suppressible protocol requirements:
* Parameter packs now check all of the arguments appropriately
* Most structural types now implement checking (these are hard to test).
Introduce metadata and runtime support for describing conformances to
"suppressible" protocols such as `Copyable`. The metadata changes occur
in several different places:
* Context descriptors gain a flag bit to indicate when the type itself has
suppressed one or more suppressible protocols (e.g., it is `~Copyable`).
When the bit is set, the context will have a trailing
`SuppressibleProtocolSet`, a 16-bit bitfield that records one bit for
each suppressed protocol. Types with no suppressed conformances will
leave the bit unset (so the metadata is unchanged), and older runtimes
don't look at the bit, so they will ignore the extra data.
* Generic context descriptors gain a flag bit to indicate when the type
has conditional conformances to suppressible protocols. When set,
there will be trailing metadata containing another
`SuppressibleProtocolSet` (a subset of the one in the main context
descriptor) indicating which suppressible protocols have conditional
conformances, followed by the actual lists of generic requirements
for each of the conditional conformances. Again, if there are no
conditional conformances to suppressible protocols, the bit won't be
set. Old runtimes ignore the bit and any trailing metadata.
* Generic requirements get a new "kind", which provides an ignored
protocol set (another `SuppressibleProtocolSet`) stating which
suppressible protocols should *not* be checked for the subject type
of the generic requirement. For example, this encodes a requirement
like `T: ~Copyable`. These generic requirements can occur anywhere
that there is a generic requirement list, e.g., conditional
conformances and extended existentials. Older runtimes handle unknown
generic requirement kinds by stating that the requirement isn't
satisfied.
Extend the runtime to perform checking of the suppressible
conformances on generic arguments as part of checking generic
requirements. This checking follows the defaults of the language, which
is that every generic argument must conform to each of the suppressible
protocols unless there is an explicit generic requirement that states
which suppressible protocols to ignore. Thus, a generic parameter list
`<T, Y where T: ~Escapable>` will check that `T` is `Copyable` but
not that it is `Escapable`, and check that `U` is both `Copyable` and
`Escapable`. To implement this, we collect the ignored protocol sets
from these suppressed requirements while processing the generic
requirements, then check all of the generic arguments against any
conformances not suppressed.
Answering the actual question "does `X` conform to `Copyable`?" (for
any suppressible protocol) looks at the context descriptor metadata to
answer the question, e.g.,
1. If there is no "suppressed protocol set", then the type conforms.
This covers types that haven't suppressed any conformances, including
all types that predate noncopyable generics.
2. If the suppressed protocol set doesn't contain `Copyable`, then the
type conforms.
3. If the type is generic and has a conditional conformance to
`Copyable`, evaluate the generic requirements for that conditional
conformance to answer whether it conforms.
The procedure above handles the bits of a `SuppressibleProtocolSet`
opaquely, with no mapping down to specific protocols. Therefore, the
same implementation will work even with future suppressible protocols,
including back deployment.
The end result of this is that we can dynamically evaluate conditional
conformances to protocols that depend on conformances to suppressible
protocols.
Implements rdar://123466649.
Ensure that context descriptor pointers are signed in the runtime by putting the ptrauth_struct attribute on the types.
We use the new __builtin_ptrauth_struct_key/disc to conditionally apply ptrauth_struct to TrailingObjects based on the signing of the base type, so that pointers to TrailingObjects get signed when used with a context descriptor pointer.
We add new runtime entrypoints that take signed pointers where appropriate, and have the compiler emit calls to the new entrypoints when targeting a sufficiently new OS.
rdar://111480914
Section scans (for metadata, protocols, etc.) can be costly. This change adds tracing calls to those scans so we can more easily see how much time is spent in these scans and where they're initiated.
This adds an os_signpost implementation controlled by SWIFT_STDLIB_TRACING, and a default empty implementation for when that's disabled.
rdar://110266743
Fix a potential false positive if we check a class for a protocol conformance and its superclasses aren't yet instantiated.
This was partially fixed before, but we were incorrectly saying that all superclasses had been instantiated if they had been instatiated by the LAST check in conformsToProtocol. That left us open for a possible false positive in an earlier check to go unnoticed.
This change fixes it by checking for uninstantiated superclasses after each iteration over superclasses, not just the last one.
This change also makes the concurrentTypeByName test much more robust. The original test caught this bug only rarely, but the new one catches it it reliably. We now look up 1000 types per test run. Testing locally, we typically hit the race after less than 100 types.
rdar://82364236
We were skipping shared cache queries if the ObjC metadata or descriptor were outside the shared cache, but we need to skip only if they're both outside the shared cache. We also need to check foreign types even if the descriptor is outside the shared cache.
rdar://93931813
The shared cache tables can only point to things within the shared cache, so if the protocol, ObjC class, or type descriptor are outside the shared cache, we know that the lookup will fail and we can skip it.
rdar://90427793
Apply a blanket pass of including `new` for the placement new allocation
and namespacing the call to the global placement new allocator. This
should repair the Android ARMv7 builds.
Leftover code was overwriting the result from the `on_disk` calls. Don't do that.
While we're in there, change the name of the `DYLD_CONFORMANCES_LOG` macro to `DYLD_CONFORMANCES_LOG` and fix up the wording to be more general.
rdar://89154273
