[AutoDiff] Add 'SILDifferentiableFunctionType'.

include/swift/AST/ASTContext.h

@@ -494,6 +494,9 @@ class ASTContext final {
   /// has been imported.  Otherwise, this returns null.
   StructDecl *getTensorDataTypeDecl() const;
 
+  /// Retrieve the type for Swift.AnyDerivative.
+  CanType getAnyDerivativeType() const;
+
   /// Retrieve the type Swift.Never.
   CanType getNeverType() const;
 

include/swift/AST/AutoDiff.h

@@ -301,7 +301,7 @@ class AutoDiffIndexSubset : public llvm::FoldingSetNode {
     SmallBitVector indicesBitVec(capacity, false);
     for (auto index : indices)
       indicesBitVec.set(index);
-    return AutoDiffIndexSubset::get(ctx, indicesBitVec);
+    return get(ctx, indicesBitVec);
   }
 
   static AutoDiffIndexSubset *getDefault(ASTContext &ctx, unsigned capacity,
@@ -557,6 +557,31 @@ class AutoDiffAssociatedFunctionIdentifier : public llvm::FoldingSetNode {
   }
 };
 
+/// The kind of ABI used to represent a differentiable function.
+enum class DifferentiabilityRepresentationKind : unsigned {
+  /// The function is linear and is represented as a bundle of the original
+  /// function and its transpose. Its differential is the function itself. Its
+  /// pullback is its transpose.
+  ///
+  /// For original function `(T...) -> U`, there are a few typing invariants:
+  /// 1. T = T.TangentVector = T.CotangentVector
+  /// 2. U = U.TangentVector = U.CotangentVector
+  ///
+  /// |----------------------|
+  /// | Original | Transpose |
+  /// |----------------------|
+  Linear = 0,
+
+  /// The function is represented as a bundle of the original function and
+  /// JVP functions at every order. JVP functions must be thin.
+  ///
+  ///                1        2    ...     n
+  /// |----------------------------------------|
+  /// | Original | JVP@1 | JVP@2 | ... | JVP@n |
+  /// |----------------------------------------|
+  Normal = 1
+};
+
 /// Automatic differentiation utility namespace.
 namespace autodiff {
 
@@ -606,8 +631,8 @@ class VectorSpace {
     Vector,
     /// A product of vector spaces as a tuple.
     Tuple,
-    /// A function type whose innermost result conforms to `AdditiveArithmetic`.
-    Function
+    /// An existential `AdditiveArithmetic` type.
+    Existential
   };
 
 private:
@@ -617,16 +642,12 @@ class VectorSpace {
     Type vectorType;
     // Tuple
     TupleType *tupleType;
-    // Function
-    AnyFunctionType *functionType;
 
     Value(Type vectorType) : vectorType(vectorType) {}
     Value(TupleType *tupleType) : tupleType(tupleType) {}
-    Value(AnyFunctionType *functionType) : functionType(functionType) {}
   } value;
 
-  VectorSpace(Kind kind, Value value)
-      : kind(kind), value(value) {}
+  VectorSpace(Kind kind, Value value) : kind(kind), value(value) {}
 
 public:
   VectorSpace() = delete;
@@ -637,12 +658,11 @@ class VectorSpace {
   static VectorSpace getTuple(TupleType *tupleTy) {
     return {Kind::Tuple, tupleTy};
   }
-  static VectorSpace getFunction(AnyFunctionType *fnTy) {
-    return {Kind::Function, fnTy};
-  }
+  static VectorSpace getExistential(ASTContext &ctx);
 
   bool isVector() const { return kind == Kind::Vector; }
   bool isTuple() const { return kind == Kind::Tuple; }
+  bool isExistential() const { return kind == Kind::Existential; }
 
   Kind getKind() const { return kind; }
   Type getVector() const {
@@ -653,10 +673,6 @@ class VectorSpace {
     assert(kind == Kind::Tuple);
     return value.tupleType;
   }
-  AnyFunctionType *getFunction() const {
-    assert(kind == Kind::Function);
-    return value.functionType;
-  }
 
   Type getType() const;
   CanType getCanonicalType() const;

include/swift/AST/DiagnosticsParse.def

@@ -1393,6 +1393,25 @@ ERROR(convention_attribute_witness_method_expected_colon,none,
 ERROR(convention_attribute_witness_method_expected_protocol,none,
       "expected protocol name in 'witness_method' 'convention' attribute", ())
 
+// sil_differentiable
+ERROR(sil_differentiable_attribute_expected_lparen,none,
+      "expected '(' after 'sil_differentiable'", ())
+ERROR(sil_differentiable_attribute_expected_max_order,none,
+      "expected a max differentiation order in 'sil_differentiable(...)'", ())
+ERROR(sil_differentiable_attribute_expected_rparen,none,
+      "expected ')' after the representation kind or order for "
+      "'sil_differentiable'", ())
+ERROR(sil_differentiable_attribute_expected_lbrace,none,
+      "expected '{' in a 'sil_differentiable' type", ())
+ERROR(sil_differentiable_attribute_expected_differential,none,
+      "expected 'differential:'", ())
+ERROR(sil_differentiable_attribute_expected_pullback,none,
+      "expected 'pullback:' ", ())
+ERROR(sil_differentiable_attribute_expected_transpose,none,
+      "expected 'transpose:' ", ())
+ERROR(sil_differentiable_attribute_expected_rbrace,none,
+      "expected '}' to end a 'sil_differentiable' type", ())
+
 // objc
 ERROR(attr_objc_missing_colon,none,
       "missing ':' after selector piece in @objc attribute", ())

include/swift/AST/DiagnosticsSema.def

@@ -3793,6 +3793,24 @@ ERROR(sil_metatype_multiple_reprs,none,
       "metatypes in SIL can only be one of @thin, @thick, or @objc_metatype",
       ())
 
+// SWIFT_ENABLE_TENSORFLOW
+// @sil_differentiable types
+ERROR(sil_differentiable_attr_not_applicable,none,
+      "'sil_differentiable' is not applicable to this type", ())
+ERROR(sil_differentiable_required_original_function_field,none,
+      "an original function type field is required in a 'sil_differentiable'",
+      ())
+ERROR(sil_differentiable_required_field,none,
+      "a '%0' function type field is required in a 'sil_differentiable'",
+      (StringRef))
+ERROR(sil_differentiable_fields_must_be_function_type,none,
+      "fields in a 'sil_differentiable' type must be function types", ())
+ERROR(sil_differentiable_invalid_field,none,
+      "invalid field for the specified '@sil_differentiable' representation "
+      "kind", ())
+ERROR(sil_differentiable_field_cannot_be_generic,none,
+      "'sil_differentiable' field type cannot be generic", ())
+
 //------------------------------------------------------------------------------
 // MARK: @objc and @nonobjc
 //------------------------------------------------------------------------------

include/swift/AST/KnownStdlibTypes.def

@@ -84,4 +84,7 @@ KNOWN_STDLIB_TYPE_DECL(KeyedEncodingContainer, NominalTypeDecl, 1)
 KNOWN_STDLIB_TYPE_DECL(KeyedDecodingContainer, NominalTypeDecl, 1)
 KNOWN_STDLIB_TYPE_DECL(RangeReplaceableCollection, ProtocolDecl, 1)
 
+// SWIFT_ENABLE_TENSORFLOW
+KNOWN_STDLIB_TYPE_DECL(AnyDerivative, StructDecl, 0)
+
 #undef KNOWN_STDLIB_TYPE_DECL

include/swift/AST/TypeMatcher.h

@@ -239,6 +239,8 @@ class TypeMatcher {
     TRIVIAL_CASE(SILFunctionType)
     TRIVIAL_CASE(SILBlockStorageType)
     TRIVIAL_CASE(SILBoxType)
+    // SWIFT_ENABLE_TENSORFLOW
+    TRIVIAL_CASE(SILDifferentiableFunctionType)
     TRIVIAL_CASE(ProtocolCompositionType)
 
     bool visitLValueType(CanLValueType firstLValue, Type secondType,

include/swift/AST/TypeNodes.def

@@ -148,6 +148,8 @@ ARTIFICIAL_TYPE(SILFunction, Type)
 ARTIFICIAL_TYPE(SILBlockStorage, Type)
 ARTIFICIAL_TYPE(SILBox, Type)
 ARTIFICIAL_TYPE(SILToken, Type)
+// SWIFT_ENABLE_TENSORFLOW
+ARTIFICIAL_TYPE(SILDifferentiableFunction, Type)
 TYPE(ProtocolComposition, Type)
 TYPE(LValue, Type)
 TYPE(InOut, Type)

include/swift/AST/TypeRepr.h

@@ -1150,6 +1150,8 @@ inline bool TypeRepr::isSimple() const {
   case TypeReprKind::InOut:
   case TypeReprKind::Composition:
   case TypeReprKind::OpaqueReturn:
+  // SWIFT_ENABLE_TENSORFLOW
+  case TypeReprKind::SILDifferentiableFunction:
     return false;
   case TypeReprKind::SimpleIdent:
   case TypeReprKind::GenericIdent:
@@ -1170,6 +1172,61 @@ inline bool TypeRepr::isSimple() const {
   llvm_unreachable("bad TypeRepr kind");
 }
 
+// SWIFT_ENABLE_TENSORFLOW
+class SILDifferentiableFunctionTypeRepr final : public TypeRepr {
+  GenericParamList *GenericParams;
+  DifferentiabilityRepresentationKind reprKind;
+  int maxOrder;
+  GenericEnvironment *GenericEnv = nullptr;
+  TypeRepr *Original;
+  TypeRepr *Differential;
+  TypeRepr *Pullback;
+  TypeRepr *Transpose;
+  SourceRange Braces;
+
+public:
+  SILDifferentiableFunctionTypeRepr(
+      GenericParamList *genericParams,
+      DifferentiabilityRepresentationKind reprKind, int maxOrder,
+      TypeRepr *original, TypeRepr *differential, TypeRepr *pullback,
+      TypeRepr *transpose, SourceRange braces)
+      : TypeRepr(TypeReprKind::SILDifferentiableFunction),
+        GenericParams(genericParams), reprKind(reprKind), maxOrder(maxOrder),
+        Original(original), Differential(differential), Pullback(pullback),
+        Transpose(transpose), Braces(braces) {}
+
+  GenericParamList *getGenericParams() const { return GenericParams; };
+  GenericEnvironment *getGenericEnvironment() const { return GenericEnv; };
+  void setGenericEnvironment(GenericEnvironment *env) {
+    assert(GenericEnv == nullptr);
+    GenericEnv = env;
+  }
+  DifferentiabilityRepresentationKind getRepresentationKind() const {
+    return reprKind;
+  }
+  int getMaxOrder() const { return maxOrder; }
+  TypeRepr *getOriginal() const { return Original; }
+  TypeRepr *getDifferential() const { return Differential; }
+  TypeRepr *getPullback() const { return Pullback; }
+  TypeRepr *getTranspose() const { return Transpose; }
+
+  SourceRange getBraces() const { return Braces; }
+
+  static bool classof(const TypeRepr *T) {
+    return T->getKind() == TypeReprKind::SILDifferentiableFunction;
+  }
+
+  static bool classof(const SILDifferentiableFunctionTypeRepr *T) {
+    return true;
+  }
+
+private:
+  SourceLoc getStartLocImpl() const { return Braces.Start; }
+  SourceLoc getEndLocImpl() const { return Braces.End; }
+  void printImpl(ASTPrinter &Printer, const PrintOptions &Opts) const;
+  friend class TypeRepr;
+};
+
 } // end namespace swift
 
 namespace llvm {

include/swift/AST/TypeReprNodes.def

@@ -60,6 +60,8 @@ ABSTRACT_TYPEREPR(Specifier, TypeRepr)
   TYPEREPR(Owned, SpecifierTypeRepr)
 TYPEREPR(Fixed, TypeRepr)
 TYPEREPR(SILBox, TypeRepr)
+// SWIFT_ENABLE_TENSORFLOW
+TYPEREPR(SILDifferentiableFunction, TypeRepr)
 LAST_TYPEREPR(SILBox)
 
 #undef ABSTRACT_TYPEREPR