Change AutoDiffConfig to a POD.

The contents of `AutoDiffConfig` are all uniqued, so uniquing the product
does not make sense.

Author: dan-zheng

include/swift/AST/AutoDiff.h

@@ -212,35 +212,10 @@ struct AutoDiffDerivativeFunctionKind {
 /// - Parameter indices.
 /// - Result indices.
 /// - Derivative generic signature (optional).
-// TODO(TF-893): Use `AutoDiffConfig` in `AutoDiffDerivativeFunctionIdentifier`
-// to avoid duplication.
-class AutoDiffConfig : public llvm::FoldingSetNode {
-  IndexSubset *const parameterIndices;
-  IndexSubset *const resultIndices;
+struct AutoDiffConfig {
+  IndexSubset *parameterIndices;
+  IndexSubset *resultIndices;
   GenericSignature *derivativeGenericSignature;
-
-  AutoDiffConfig(IndexSubset *parameterIndices, IndexSubset *resultIndices,
-                 GenericSignature *derivativeGenericSignature)
-      : parameterIndices(parameterIndices), resultIndices(resultIndices),
-        derivativeGenericSignature(derivativeGenericSignature) {}
-
-public:
-  IndexSubset *getParameterIndices() const { return parameterIndices; }
-  IndexSubset *getResultIndices() const { return resultIndices; }
-  GenericSignature *getDerivativeGenericSignature() const {
-    return derivativeGenericSignature;
-  }
-
-  static AutoDiffConfig *get(IndexSubset *parameterIndices,
-                             IndexSubset *resultIndices,
-                             GenericSignature *derivativeGenericSignature,
-                             ASTContext &C);
-
-  void Profile(llvm::FoldingSetNodeID &ID) {
-    ID.AddPointer(parameterIndices);
-    ID.AddPointer(resultIndices);
-    ID.AddPointer(derivativeGenericSignature);
-  }
 };
 
 /// In conjunction with the original function declaration, identifies an
@@ -253,8 +228,7 @@ class AutoDiffDerivativeFunctionIdentifier : public llvm::FoldingSetNode {
   IndexSubset *const parameterIndices;
 
   AutoDiffDerivativeFunctionIdentifier(
-      AutoDiffDerivativeFunctionKind kind,
-      IndexSubset *parameterIndices) :
+      AutoDiffDerivativeFunctionKind kind, IndexSubset *parameterIndices) :
     kind(kind), parameterIndices(parameterIndices) {}
 
 public:
@@ -276,7 +250,7 @@ class AutoDiffDerivativeFunctionIdentifier : public llvm::FoldingSetNode {
 /// The key type used for uniquing `SILDifferentiabilityWitness` in
 /// `SILModule`: original function name, parameter indices, result indices, and
 /// derivative generic signature.
-using SILDifferentiabilityWitnessKey = std::pair<StringRef, AutoDiffConfig *>;
+using SILDifferentiabilityWitnessKey = std::pair<StringRef, AutoDiffConfig>;
 
 /// Automatic differentiation utility namespace.
 namespace autodiff {
@@ -403,10 +377,44 @@ class VectorSpace {
 
 namespace llvm {
 
+using swift::AutoDiffConfig;
+using swift::AutoDiffDerivativeFunctionKind;
+using swift::GenericSignature;
+using swift::IndexSubset;
 using swift::SILAutoDiffIndices;
 
 template<typename T> struct DenseMapInfo;
 
+template<> struct DenseMapInfo<AutoDiffConfig> {
+  static AutoDiffConfig getEmptyKey() {
+    auto *ptr = llvm::DenseMapInfo<void *>::getEmptyKey();
+    return {static_cast<IndexSubset *>(ptr),
+            static_cast<IndexSubset *>(ptr),
+            static_cast<GenericSignature *>(ptr)};
+  }
+
+  static AutoDiffConfig getTombstoneKey() {
+    auto *ptr = llvm::DenseMapInfo<void *>::getTombstoneKey();
+    return {static_cast<IndexSubset *>(ptr),
+        static_cast<IndexSubset *>(ptr),
+        static_cast<GenericSignature *>(ptr)};
+  }
+
+  static unsigned getHashValue(const AutoDiffConfig &Val) {
+    unsigned combinedHash = hash_combine(
+        ~1U, DenseMapInfo<void *>::getHashValue(Val.parameterIndices),
+        DenseMapInfo<void *>::getHashValue(Val.resultIndices),
+        DenseMapInfo<void *>::getHashValue(Val.derivativeGenericSignature));
+    return combinedHash;
+  }
+
+  static bool isEqual(const AutoDiffConfig &LHS, const AutoDiffConfig &RHS) {
+    return LHS.parameterIndices == RHS.parameterIndices &&
+        LHS.resultIndices == RHS.resultIndices &&
+        LHS.derivativeGenericSignature == RHS.derivativeGenericSignature;
+  }
+};
+
 template<> struct DenseMapInfo<SILAutoDiffIndices> {
   static SILAutoDiffIndices getEmptyKey() {
     return { DenseMapInfo<unsigned>::getEmptyKey(), nullptr };

include/swift/SIL/SILDifferentiabilityWitness.h

@@ -47,9 +47,12 @@ class SILDifferentiabilityWitness
   SILLinkage linkage;
   /// The original function.
   SILFunction *originalFunction;
-  /// The autodiff configuration: parameter indices, result indices, and
-  /// derivative generic signature (optional).
-  AutoDiffConfig *autoDiffConfig;
+  /// The parameter indices.
+  IndexSubset *parameterIndices;
+  /// The result indices.
+  IndexSubset *resultIndices;
+  /// The derivative generic signature (optional).
+  GenericSignature *derivativeGenericSignature;
   /// The JVP (Jacobian-vector products) derivative function.
   SILFunction *jvp;
   /// The VJP (vector-Jacobian products) derivative function.
@@ -71,9 +74,9 @@ class SILDifferentiabilityWitness
                               SILFunction *jvp, SILFunction *vjp,
                               bool isSerialized)
     : module(module), linkage(linkage), originalFunction(originalFunction),
-      autoDiffConfig(getAutoDiffConfig(
-          module, parameterIndices, resultIndices, derivativeGenSig)),
-      jvp(jvp), vjp(vjp), serialized(isSerialized) {}
+      parameterIndices(parameterIndices), resultIndices(resultIndices),
+      derivativeGenericSignature(derivativeGenSig), jvp(jvp), vjp(vjp),
+      serialized(isSerialized) {}
 
 public:
   static SILDifferentiabilityWitness *create(
@@ -87,13 +90,13 @@ class SILDifferentiabilityWitness
   SILLinkage getLinkage() const { return linkage; }
   SILFunction *getOriginalFunction() const { return originalFunction; }
   IndexSubset *getParameterIndices() const {
-    return autoDiffConfig->getParameterIndices();
+    return parameterIndices;
   }
   IndexSubset *getResultIndices() const {
-    return autoDiffConfig->getResultIndices();
+    return resultIndices;
   }
   GenericSignature *getDerivativeGenericSignature() const {
-    return autoDiffConfig->getDerivativeGenericSignature();
+    return derivativeGenericSignature;
   }
   SILFunction *getJVP() const { return jvp; }
   SILFunction *getVJP() const { return vjp; }

lib/AST/ASTContext.cpp

@@ -449,9 +449,6 @@ FOR_KNOWN_FOUNDATION_TYPES(CACHE_FOUNDATION_DECL)
   /// For uniquifying `IndexSubset` allocations.
   llvm::FoldingSet<IndexSubset> IndexSubsets;
 
-  /// For uniquifying `AutoDiffConfig` allocations.
-  llvm::FoldingSet<AutoDiffConfig> AutoDiffConfigs;
-
   /// For uniquifying `AutoDiffDerivativeFunctionIdentifier` allocations.
   llvm::FoldingSet<AutoDiffDerivativeFunctionIdentifier>
       AutoDiffDerivativeFunctionIdentifiers;
@@ -4832,27 +4829,6 @@ IndexSubset::get(ASTContext &ctx, const SmallBitVector &indices) {
   return newNode;
 }
 
-AutoDiffConfig *AutoDiffConfig::get(
-    IndexSubset *parameterIndices, IndexSubset *resultIndices,
-    GenericSignature *derivativeGenericSignature, ASTContext &C) {
-  assert(parameterIndices);
-  assert(resultIndices);
-  auto &foldingSet = C.getImpl().AutoDiffConfigs;
-  llvm::FoldingSetNodeID id;
-  id.AddPointer(parameterIndices);
-  id.AddPointer(resultIndices);
-  id.AddPointer(derivativeGenericSignature);
-  void *insertPos;
-  auto *existing = foldingSet.FindNodeOrInsertPos(id, insertPos);
-  if (existing)
-    return existing;
-  void *buf = C.Allocate(sizeof(AutoDiffConfig), alignof(AutoDiffConfig));
-  auto *newNode = new (buf) AutoDiffConfig(
-      parameterIndices, resultIndices, derivativeGenericSignature);
-  foldingSet.InsertNode(newNode, insertPos);
-  return newNode;
-}
-
 AutoDiffDerivativeFunctionIdentifier *
 AutoDiffDerivativeFunctionIdentifier::get(
     AutoDiffDerivativeFunctionKind kind, IndexSubset *parameterIndices,

lib/AST/ASTMangler.cpp

@@ -432,10 +432,9 @@ std::string ASTMangler::mangleSILDifferentiabilityWitnessKey(
   beginManglingWithoutPrefix();
 
   auto originalName = key.first;
-  auto *autoDiffConfig = key.second;
-  auto *parameterIndices = autoDiffConfig->getParameterIndices();
-  auto *resultIndices = autoDiffConfig->getResultIndices();
-  auto *derivativeGenericSignature = autoDiffConfig->getDerivativeGenericSignature();
+  auto *parameterIndices = key.second.parameterIndices;
+  auto *resultIndices = key.second.resultIndices;
+  auto *derivativeGenericSignature = key.second.derivativeGenericSignature;
 
   Buffer << "AD__" << originalName << '_';
   Buffer << "P" << parameterIndices->getString();

lib/SIL/SILDifferentiabilityWitness.cpp

@@ -35,13 +35,8 @@ SILDifferentiabilityWitness *SILDifferentiabilityWitness::create(
   return diffWitness;
 }
 
-AutoDiffConfig *SILDifferentiabilityWitness::getAutoDiffConfig(
-    SILModule &module, IndexSubset *parameterIndices,
-    IndexSubset *resultIndices, GenericSignature *derivativeGenSig) {
-  return AutoDiffConfig::get(parameterIndices, resultIndices, derivativeGenSig,
-                             module.getASTContext());
-}
-
 SILDifferentiabilityWitnessKey SILDifferentiabilityWitness::getKey() const {
-  return std::make_pair(originalFunction->getName(), autoDiffConfig);
+  AutoDiffConfig config{parameterIndices, resultIndices,
+                        derivativeGenericSignature};
+  return std::make_pair(originalFunction->getName(), config);
 }