VarPattern is today used to implement both 'let' and 'var' pattern bindings, so
today is already misleading. The reason why the name Var was chosen was done b/c
it is meant to represent a pattern that performs 'variable binding'. Given that
I am going to add a new 'inout' pattern binding to this, it makes sense to
give it now a better fitting name before I make things more confusing.
SILType and SILDeclRef do not actually need anything from SIL/*.h. Also,
a few dependencies can be pushed out of the headers into cpp files to
speed up incremental rebuilds.
`DifferentiableFunctionInst` now stores result indices.
`SILAutoDiffIndices` now stores result indices instead of a source index.
`@differentiable` SIL function types may now have multiple differentiability
result indices and `@noDerivative` resutls.
`@differentiable` AST function types do not have `@noDerivative` results (yet),
so this functionality is not exposed to users.
Resolves TF-689 and TF-1256.
Infrastructural support for TF-983: supporting differentiation of `apply`
instructions with multiple active semantic results.
Mangle `@noDerivative` parameters to fix type reconstruction errors.
Resolves SR-12650. The new mangling is non-breaking.
When differentiation supports multiple result indices and `@noDerivative`
results are added, we can reuse some of this mangling support.
TBD was missing several opaque type descriptor symbols. The root causes
are: (1) the AST API called by TBD doesn't return opaque type decl if
the decl is from a serialized AST; and (2) the access level of opaque
type decl isn't serialized so TBD considers them as internal.
This change fixes both.
rdar://61833970
Make sure we mangle opaque types using the same settings as the
debugger mangling (with OptimizeProtocolNames = false) to ensure
that we can reconstruct those names again.
When mangling sugared types for DWARF debug info, we would
occassionally mix generic parameter types from different
generic environments. Since the mangling for a generic
parameter type only recorded the depth and the index, even
for distinct sugared forms, the remangler would produce a
more 'compact' mangling, by folding together generic parameters
that have the same depth/index, but distinct sugarings in the
AST.
Prevent this from happening by desugaring DWARF types the
correct amount, substituting away generic parameters while
preserving everything else.
Also, re-enable the round-trip verification with the remangler.
Fixes <rdar://problem/59496022>, <https://bugs.swift.org/browse/SR-12204>.
Add mangling scheme for `@differentiable` and `@differentiable(linear)` function
types. Mangling support is important for debug information, among other things.
Update docs and add tests.
Resolves TF-948.
Generate SIL differentiability witnesses from `@differentiable` and
`@derivative` declaration attributes.
Add SILGen utilities for:
- Emiting differentiability witnesses.
- Creating derivative function thunks, which are used as entries in
differentiability witnesses.
When users register a custom derivative function, it is necessary to create a
thunk with the expected derivative type computed from the original function's
type. This is important for consistent typing and consistent differentiability
witness entry mangling.
See `SILGenModule::getOrCreateCustomDerivativeThunk` documentation for details.
Resolves TF-1138.
We want to be able to use mangled names to refer to protocol conformances in addition to type
metadata. Provide an ASTMangler method that can render an arbitrary abstract or concrete
`ProtocolConformanceRef`, factoring it out of the code used to emit conditional conformance arguments
in `appendProtocolConformance`.
The design implemented in this patch is that we lower the types of accessors with pattern substitutions when lowering them against a different accessor, which happens with class overrides and protocol witnesses, and that we introduce pattern substitutions when substituting into a non-patterned coroutine type. This seems to achieve consistent abstraction without introduce a ton of new complexity.
An earlier version of this patch tried to define witness thunks (conservatively, just for accessors) by simply applying the requirement substitutions directly to the requirement. Conceptually that should work, but I ran into a lot of trouble with things that assumed that pattern substitutions didn't conceal significant substitution work. for example, resolving a dependent member in a component type could find a new use of an opaque archetype when the code assumed that such types had already been substituted away. So while I think that is definiteely a promising direction, I had to back that out in order to make the number of changes manageable for a single PR.
As part of this, I had to fix a number of little bugs here and there, some of which I just introduced. One of these bugfixes is a place where the substitution code was trying to improperly abstract function types when substituting them in for a type parameter, and it's been in the code for a really long time, and I'm really not sure how it's never blown up before.
I'm increasingly of the opinion that invocation substitutions are not actually necessary, but that --- after we've solved the substitution issues above --- we may want the ability to build multiple levels of pattern substitution so that we can guarantee that e.g. witness thunks always have the exact component structure of the requirement before a certain level of substitution, thus allowing the witness substitutions to be easily extracted.
In order to allow this, I've had to rework the syntax of substituted function types; what was previously spelled `<T> in () -> T for <X>` is now spelled `@substituted <T> () -> T for <X>`. I think this is a nice improvement for readability, but it did require me to churn a lot of test cases.
Distinguishing the substitutions has two chief advantages over the existing representation. First, the semantics seem quite a bit clearer at use points; the `implicit` bit was very subtle and not always obvious how to use. More importantly, it allows the expression of generic function types that must satisfy a particular generic abstraction pattern, which was otherwise impossible to express.
As an example of the latter, consider the following protocol conformance:
```
protocol P { func foo() }
struct A<T> : P { func foo() {} }
```
The lowered signature of `P.foo` is `<Self: P> (@in_guaranteed Self) -> ()`. Without this change, the lowered signature of `A.foo`'s witness would be `<T> (@in_guaranteed A<T>) -> ()`, which does not preserve information about the conformance substitution in any useful way. With this change, the lowered signature of this witness could be `<T> @substituted <Self: P> (@in_guaranteed Self) -> () for <A<T>>`, which nicely preserves the exact substitutions which relate the witness to the requirement.
When we adopt this, it will both obviate the need for the special witness-table conformance field in SILFunctionType and make it far simpler for the SILOptimizer to devirtualize witness methods. This patch does not actually take that step, however; it merely makes it possible to do so.
As another piece of unfinished business, while `SILFunctionType::substGenericArgs()` conceptually ought to simply set the given substitutions as the invocation substitutions, that would disturb a number of places that expect that method to produce an unsubstituted type. This patch only set invocation arguments when the generic type is a substituted type, which we currently never produce in type-lowering.
My plan is to start by producing substituted function types for accessors. Accessors are an important case because the coroutine continuation function is essentially an implicit component of the function type which the current substitution rules simply erase the intended abstraction of. They're also used in narrower ways that should exercise less of the optimizer.
In order for the runtime demangler to be able to find ObjC classes and protocols, it needs to
have the runtime name of the declaration be in the mangled name. Only do this for runtime manglings,
to minimize the potential ABI impact for symbol names that already have the source-level names of
ObjC entities baked in. Fixes SR-12169 | rdar://59306590.
SIL differentiability witnesses are a new top-level SIL construct mapping
"original" SIL functions to derivative SIL functions.
SIL differentiability witnesses have the following components:
- "Original" `SILFunction`.
- SIL linkage.
- Differentiability parameter indices (`IndexSubset`).
- Differentiability result indices (`IndexSubset`).
- Derivative `GenericSignature` representing differentiability generic
requirements (optional).
- JVP derivative `SILFunction` (optional).
- VJP derivative `SILFunction` (optional).
- "Is serialized?" bit.
This patch adds the `SILDifferentiabilityWitness` data structure, with
documentation, parsing, and printing.
Resolves TF-911.
Todos:
- TF-1136: upstream `SILDifferentiabilityWitness` serialization.
- TF-1137: upstream `SILDifferentiabilityWitness` verification.
- TF-1138: upstream `SILDifferentiabilityWitness` SILGen from
`@differentiable` and `@derivative` attributes.
- TF-20: robust mangling for `SILDifferentiabilityWitness` names.
Motivation: `GenericSignatureImpl::getCanonicalSignature` crashes for
`GenericSignature` with underlying `nullptr`. This led to verbose workarounds
when computing `CanGenericSignature` from `GenericSignature`.
Solution: `GenericSignature::getCanonicalSignature` is a wrapper around
`GenericSignatureImpl::getCanonicalSignature` that returns the canonical
signature, or `nullptr` if the underlying pointer is `nullptr`.
Rewrite all verbose workarounds using `GenericSignature::getCanonicalSignature`.
Enabling DWARFMangling indicates the mangled name will be used by either
debugger or IDE. We could and should avoid using the original module name so
demangling will keep working.
When an original module name is specified via @_originalDefinedIn attribute, we need to
use the original module name for all related runtime symbol names instead of the current
module names.
rdar://55268186
It was hard-coding IsStatic to false rather than passing it through from the
VarDecl, giving the same USR for the two getters in the below:
class FixtureClass95 {
private static var someVar: String!
private var someVar: String!
}
Resolves rdar://problem/44531531
USRs generated for the index store and sourcekit requests for invalid decls are
best-effort – we don't need to guarantee they can be de- or re-mangled.
ProtocolConformanceRef already has an invalid state. Drop all of the
uses of Optional<ProtocolConformanceRef> and just use
ProtocolConformanceRef::forInvalid() to represent it. Mechanically
translate all of the callers and callsites to use this new
representation.
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.
Switch most callers to explicit indices. The exceptions lie in things that needs to manipulate the parsed output directly including the Parser and components of the ASTScope. These are included as friend class exceptions.
