[AutoDiff upstream] Add differential operators and some utilities.

include/swift/Demangling/TypeDecoder.h

@@ -181,33 +181,53 @@ enum class ImplFunctionRepresentation {
   Closure
 };
 
+enum class ImplFunctionDifferentiabilityKind {
+  NonDifferentiable,
+  Normal,
+  Linear
+};
+
 class ImplFunctionTypeFlags {
   unsigned Rep : 3;
   unsigned Pseudogeneric : 1;
   unsigned Escaping : 1;
+  unsigned DifferentiabilityKind : 2;
 
 public:
-  ImplFunctionTypeFlags() : Rep(0), Pseudogeneric(0), Escaping(0) {}
+  ImplFunctionTypeFlags()
+      : Rep(0), Pseudogeneric(0), Escaping(0), DifferentiabilityKind(0) {}
 
-  ImplFunctionTypeFlags(ImplFunctionRepresentation rep,
-                        bool pseudogeneric, bool noescape)
-      : Rep(unsigned(rep)), Pseudogeneric(pseudogeneric), Escaping(noescape) {}
+  ImplFunctionTypeFlags(ImplFunctionRepresentation rep, bool pseudogeneric,
+                        bool noescape,
+                        ImplFunctionDifferentiabilityKind diffKind)
+      : Rep(unsigned(rep)), Pseudogeneric(pseudogeneric), Escaping(noescape),
+        DifferentiabilityKind(unsigned(diffKind)) {}
 
   ImplFunctionTypeFlags
   withRepresentation(ImplFunctionRepresentation rep) const {
-    return ImplFunctionTypeFlags(rep, Pseudogeneric, Escaping);
+    return ImplFunctionTypeFlags(
+        rep, Pseudogeneric, Escaping,
+        ImplFunctionDifferentiabilityKind(DifferentiabilityKind));
   }
 
   ImplFunctionTypeFlags
   withEscaping() const {
-    return ImplFunctionTypeFlags(ImplFunctionRepresentation(Rep),
-                                 Pseudogeneric, true);
+    return ImplFunctionTypeFlags(
+        ImplFunctionRepresentation(Rep), Pseudogeneric, true,
+        ImplFunctionDifferentiabilityKind(DifferentiabilityKind));
   }
 
   ImplFunctionTypeFlags
   withPseudogeneric() const {
-    return ImplFunctionTypeFlags(ImplFunctionRepresentation(Rep),
-                                 true, Escaping);
+    return ImplFunctionTypeFlags(
+        ImplFunctionRepresentation(Rep), true, Escaping,
+        ImplFunctionDifferentiabilityKind(DifferentiabilityKind));
+  }
+
+  ImplFunctionTypeFlags
+  withDifferentiabilityKind(ImplFunctionDifferentiabilityKind diffKind) const {
+    return ImplFunctionTypeFlags(ImplFunctionRepresentation(Rep), Pseudogeneric,
+                                 Escaping, diffKind);
   }
 
   ImplFunctionRepresentation getRepresentation() const {
@@ -217,6 +237,10 @@ class ImplFunctionTypeFlags {
   bool isEscaping() const { return Escaping; }
 
   bool isPseudogeneric() const { return Pseudogeneric; }
+
+  ImplFunctionDifferentiabilityKind getDifferentiabilityKind() const {
+    return ImplFunctionDifferentiabilityKind(DifferentiabilityKind);
+  }
 };
 
 #if SWIFT_OBJC_INTEROP
@@ -582,6 +606,14 @@ class TypeDecoder {
             flags =
               flags.withRepresentation(ImplFunctionRepresentation::Block);
           }
+        } else if (child->getKind() == NodeKind::ImplDifferentiable) {
+          flags = flags.withDifferentiabilityKind(
+              ImplFunctionDifferentiabilityKind::Normal);
+        } else if (child->getKind() == NodeKind::ImplLinear) {
+          flags = flags.withDifferentiabilityKind(
+              ImplFunctionDifferentiabilityKind::Linear);
+        } else if (child->getKind() == NodeKind::ImplEscaping) {
+          flags = flags.withEscaping();
         } else if (child->getKind() == NodeKind::ImplEscaping) {
           flags = flags.withEscaping();
         } else if (child->getKind() == NodeKind::ImplParameter) {

lib/AST/ASTDemangler.cpp

@@ -500,11 +500,23 @@ Type ASTBuilder::createImplFunctionType(
     break;
   }
 
+  DifferentiabilityKind diffKind;
+  switch (flags.getDifferentiabilityKind()) {
+  case ImplFunctionDifferentiabilityKind::NonDifferentiable:
+    diffKind = DifferentiabilityKind::NonDifferentiable;
+    break;
+  case ImplFunctionDifferentiabilityKind::Normal:
+    diffKind = DifferentiabilityKind::Normal;
+    break;
+  case ImplFunctionDifferentiabilityKind::Linear:
+    diffKind = DifferentiabilityKind::Linear;
+    break;
+  }
+
   // TODO: [store-sil-clang-function-type]
-  auto einfo = SILFunctionType::ExtInfo(
-      representation, flags.isPseudogeneric(), !flags.isEscaping(),
-      DifferentiabilityKind::NonDifferentiable,
-      /*clangFunctionType*/ nullptr);
+  auto einfo = SILFunctionType::ExtInfo(representation, flags.isPseudogeneric(),
+                                        !flags.isEscaping(), diffKind,
+                                        /*clangFunctionType*/ nullptr);
 
   llvm::SmallVector<SILParameterInfo, 8> funcParams;
   llvm::SmallVector<SILYieldInfo, 8> funcYields;

lib/SILGen/SILGenBuiltin.cpp

@@ -1106,14 +1106,9 @@ static ManagedValue emitBuiltinAutoDiffApplyTransposeFunction(
     origFnArgVals.push_back(arg.getValue());
 
   // Get the transpose function.
-  // TODO(TF-1142): Create a linear_function_extract instead of an undef.
-  auto fnTy = origFnVal->getType().castTo<SILFunctionType>();
-  auto transposeFnType =
-      fnTy->getWithoutDifferentiability()->getAutoDiffTransposeFunctionType(
-      fnTy->getDifferentiabilityParameterIndices(), SGF.SGM.M.Types,
-      LookUpConformanceInModule(SGF.SGM.M.getSwiftModule()));
-  SILValue transposeFn =
-      SILUndef::get(SILType::getPrimitiveObjectType(transposeFnType), SGF.F);
+  SILValue transposeFn = SGF.B.createLinearFunctionExtract(
+      loc, LinearDifferentiableFunctionTypeComponent::Transpose, origFnVal);
+  auto transposeFnType = transposeFn->getType().castTo<SILFunctionType>();
   auto transposeFnUnsubstType =
       transposeFnType->getUnsubstitutedType(SGF.getModule());
   if (transposeFnType != transposeFnUnsubstType) {
@@ -1204,19 +1199,16 @@ static ManagedValue emitBuiltinLinearFunction(
   assert(args.size() == 2);
   auto origFn = args.front();
   auto origType = origFn.getType().castTo<SILFunctionType>();
-  // TODO(TF-1142): Create a linear_function instead of an undef.
-  auto linearFnTy = origType->getWithDifferentiability(
-      DifferentiabilityKind::Linear,
+  auto linearFn = SGF.B.createLinearFunction(
+      loc,
       IndexSubset::getDefault(
-          SGF.getASTContext(), origType->getNumParameters(),
-          /*includeAll*/ true));
-  SILValue linearFn = SILUndef::get(
-      SILType::getPrimitiveObjectType(linearFnTy), SGF.F);
+          SGF.getASTContext(),
+          origType->getNumParameters(),
+          /*includeAll*/ true),
+      origFn.forward(SGF), args[1].forward(SGF));
   return SGF.emitManagedRValueWithCleanup(linearFn);
 }
 
-
-
 /// Emit SIL for the named builtin: globalStringTablePointer. Unlike the default
 /// ownership convention for named builtins, which is to take (non-trivial)
 /// arguments as Owned, this builtin accepts owned as well as guaranteed

lib/SILOptimizer/Transforms/SemanticARCOpts.cpp

@@ -776,6 +776,10 @@ struct SemanticARCOptVisitor
   FORWARDING_INST(OpenExistentialBoxValue)
   FORWARDING_INST(MarkDependence)
   FORWARDING_INST(InitExistentialRef)
+  FORWARDING_INST(DifferentiableFunction)
+  FORWARDING_INST(LinearFunction)
+  FORWARDING_INST(DifferentiableFunctionExtract)
+  FORWARDING_INST(LinearFunctionExtract)
 #undef FORWARDING_INST
 
 #define FORWARDING_TERM(NAME)                                                  \

stdlib/public/Differentiation/CMakeLists.txt

@@ -12,7 +12,12 @@
 
 add_swift_target_library(swift_Differentiation ${SWIFT_STDLIB_LIBRARY_BUILD_TYPES} IS_STDLIB
   Differentiable.swift
+  DifferentialOperators.swift
+  DifferentiationUtilities.swift
 
-  SWIFT_COMPILE_FLAGS ${SWIFT_STANDARD_LIBRARY_SWIFT_FLAGS}
+  SWIFT_COMPILE_FLAGS
+    ${SWIFT_STANDARD_LIBRARY_SWIFT_FLAGS}
+    -parse-stdlib
+    -Xfrontend -enable-experimental-differentiable-programming
   LINK_FLAGS "${SWIFT_RUNTIME_SWIFT_LINK_FLAGS}"
   INSTALL_IN_COMPONENT stdlib)

stdlib/public/Differentiation/Differentiable.swift

@@ -20,6 +20,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+import Swift
+
 /// A type that mathematically represents a differentiable manifold whose
 /// tangent spaces are finite-dimensional.
 public protocol Differentiable {