Because C++ constructors always take a `this` pointer to the object to
be initialized, we mark the SIL function return type with the `@out`
attribute.
On the IRGen side, we retrofit support for formal indirect return values as
well as thin metatypes.
Previously the code for loading indirect returns was inline in the
member function where it was performed. Here it is pulled out into a
private method.
Previously, the AsyncContextLayout did not make space for the trailing
witness fields (self metadata and self witness table) and the
AsyncNativeCCEntryPointArgumentEmission could consequently not vend
these fields. Here, the fields are added to the layout.
Previously, the indirect results were claimed from the explosion after
the arguments were claimed. That failed to match the order in which
arguments actually appear in the explosion. Here the order is reversed.
Previously, the polymorphic arguments were being discarded. Here, that
situation is improved by pulling the polymorphic arguments out of the
explosion when having the polymorphic parameters via the
NecessaryBindings instance. In order to eanble that, an overload of
NecessaryBindings::save is added which takes an explosion and asserts
that the polymorphic parameter pulled from the explosion matches with
the polymorphic parameter in the NecessaryBindings instance.
Here, the following is implemented:
- Construction of SwiftContext struct with the fields needed for calling
functions.
- Allocating and deallocating these swift context via runtime calls
before calling async functions and after returning from them.
- Storing arguments (including bindings and the self parameter but not
including protocol fields for witness methods) and returns (both
direct and indirect).
- Calling async functions.
Additional things that still need to be done:
- protocol extension methods
- protocol witness methods
- storing yields
- partial applies
In apple/llvm-project 9e7b7cbbbdb59d53136c0480f17cfe6ecef94163
(llvm/llvm-project ecd682bbf5e69e8690b7e3634258f05ae0a70448), BFloat16
was added to the clang builtins.
1) Shrink from 4 bytes to 1 byte.
2) Assert that alignments are power-of-two at run time.
3) Assert that alignments are power-of-two at compile time when possible.
4) Eliminate "isZero"/"no alignment" from the type. Use llvm::Optional.
This became necessary after recent function type changes that keep
substituted generic function types abstract even after substitution to
correctly handle automatic opaque result type substitution.
Instead of performing the opaque result type substitution as part of
substituting the generic args the underlying type will now be reified as
part of looking at the parameter/return types which happens as part of
the function convention apis.
rdar://62560867
https://forums.swift.org/t/improving-the-representation-of-polymorphic-interfaces-in-sil-with-substituted-function-types/29711
This prepares SIL to be able to more accurately preserve the calling convention of
polymorphic generic interfaces by letting the type system represent "substituted function types".
We add a couple of fields to SILFunctionType to support this:
- A substitution map, accessed by `getSubstitutions()`, which maps the generic signature
of the function to its concrete implementation. This will allow, for instance, a protocol
witness for a requirement of type `<Self: P> (Self, ...) -> ...` for a concrete conforming
type `Foo` to express its type as `<Self: P> (Self, ...) -> ... for <Foo>`, preserving the relation
to the protocol interface without relying on the pile of hacks that is the `witness_method`
protocol.
- A bool for whether the generic signature of the function is "implied" by the substitutions.
If true, the generic signature isn't really part of the calling convention of the function.
This will allow closure types to distinguish a closure being passed to a generic function, like
`<T, U> in (*T, *U) -> T for <Int, String>`, from the concrete type `(*Int, *String) -> Int`,
which will make it easier for us to differentiate the representation of those as types, for
instance by giving them different pointer authentication discriminators to harden arm64e
code.
This patch is currently NFC, it just introduces the new APIs and takes a first pass at updating
code to use them. Much more work will need to be done once we start exercising these new
fields.
This does bifurcate some existing APIs:
- SILFunctionType now has two accessors to get its generic signature.
`getSubstGenericSignature` gets the generic signature that is used to apply its
substitution map, if any. `getInvocationGenericSignature` gets the generic signature
used to invoke the function at apply sites. These differ if the generic signature is
implied.
- SILParameterInfo and SILResultInfo values carry the unsubstituted types of the parameters
and results of the function. They now have two APIs to get that type. `getInterfaceType`
returns the unsubstituted type of the generic interface, and
`getArgumentType`/`getReturnValueType` produce the substituted type that is used at
apply sites.
