Merge pull request #20491 from DougGregor/runtime-conformance-descriptor-cache

 [Runtime] Cache protocol conformance descriptors, not witness tables.

Author: DougGregor

include/swift/Basic/Lazy.h

@@ -58,6 +58,9 @@ template <class T> class Lazy {
 
   T &get(void (*initCallback)(void *) = defaultInitCallback);
 
+  template<typename Arg1>
+  T &getWithInit(Arg1 &&arg1);
+
   /// Get the value, assuming it must have already been initialized by this
   /// point.
   T &unsafeGetAlreadyInitialized() { return *reinterpret_cast<T *>(&Value); }
@@ -80,6 +83,22 @@ template <typename T> inline T &Lazy<T>::get(void (*initCallback)(void*)) {
   return unsafeGetAlreadyInitialized();
 }
 
+template <typename T>
+template <typename Arg1> inline T &Lazy<T>::getWithInit(Arg1 &&arg1) {
+  struct Data {
+    void *address;
+    Arg1 &&arg1;
+
+    static void init(void *context) {
+      Data *data = static_cast<Data *>(context);
+      ::new (data->address) T(static_cast<Arg1&&>(data->arg1));
+    }
+  } data{&Value, static_cast<Arg1&&>(arg1)};
+
+  SWIFT_ONCE_F(OnceToken, &Data::init, &data);
+  return unsafeGetAlreadyInitialized();
+}
+
 } // end namespace swift
 
 #define SWIFT_LAZY_CONSTANT(INITIAL_VALUE) \

stdlib/public/runtime/Metadata.cpp

@@ -268,12 +268,39 @@ namespace {
   };
 } // end anonymous namespace
 
-using GenericMetadataCache = MetadataCache<GenericCacheEntry, false>;
-using LazyGenericMetadataCache = Lazy<GenericMetadataCache>;
+namespace {
+  class GenericMetadataCache : public MetadataCache<GenericCacheEntry, false> {
+  public:
+    uint16_t NumKeyParameters;
+    uint16_t NumWitnessTables;
+
+    GenericMetadataCache(const TargetGenericContext<InProcess> &genericContext)
+        : NumKeyParameters(0), NumWitnessTables(0) {
+      // Count up the # of key parameters and # of witness tables.
+
+      // Find key generic parameters.
+      for (const auto &gp : genericContext.getGenericParams()) {
+        if (gp.hasKeyArgument())
+          ++NumKeyParameters;
+      }
+
+      // Find witness tables.
+      for (const auto &req : genericContext.getGenericRequirements()) {
+        if (req.Flags.hasKeyArgument() &&
+            req.getKind() == GenericRequirementKind::Protocol)
+          ++NumWitnessTables;
+      }
+    }
+  };
+
+  using LazyGenericMetadataCache = Lazy<GenericMetadataCache>;
+}
 
 /// Fetch the metadata cache for a generic metadata structure.
 static GenericMetadataCache &getCache(
-    const TypeGenericContextDescriptorHeader &generics) {
+                               const TypeContextDescriptor &description) {
+  auto &generics = description.getFullGenericContextHeader();
+
   // Keep this assert even if you change the representation above.
   static_assert(sizeof(LazyGenericMetadataCache) <=
                 sizeof(GenericMetadataInstantiationCache::PrivateData),
@@ -282,7 +309,7 @@ static GenericMetadataCache &getCache(
   auto lazyCache =
     reinterpret_cast<LazyGenericMetadataCache*>(
       generics.getInstantiationCache()->PrivateData);
-  return lazyCache->get();
+  return lazyCache->getWithInit(*description.getGenericContext());
 }
 
 /// Fetch the metadata cache for a generic metadata structure,
@@ -527,9 +554,11 @@ swift::swift_getGenericMetadata(MetadataRequest request,
   auto &generics = description->getFullGenericContextHeader();
   size_t numGenericArgs = generics.Base.NumKeyArguments;
 
-  auto key = MetadataCacheKey(arguments, numGenericArgs);
-  auto result =
-    getCache(generics).getOrInsert(key, request, description, arguments);
+  auto &cache = getCache(*description);
+  assert(numGenericArgs == cache.NumKeyParameters + cache.NumWitnessTables);
+  auto key = MetadataCacheKey(cache.NumKeyParameters, cache.NumWitnessTables,
+                              arguments);
+  auto result = cache.getOrInsert(key, request, description, arguments);
 
   return result.second;
 }
@@ -4337,11 +4366,15 @@ static Result performOnMetadataCache(const Metadata *metadata,
   auto genericArgs =
     reinterpret_cast<const void * const *>(
                                     description->getGenericArguments(metadata));
+  auto &cache = getCache(*description);
   size_t numGenericArgs = generics.Base.NumKeyArguments;
-  auto key = MetadataCacheKey(genericArgs, numGenericArgs);
+  assert(numGenericArgs == cache.NumKeyParameters + cache.NumWitnessTables);
+  (void)numGenericArgs;
+  auto key = MetadataCacheKey(cache.NumKeyParameters, cache.NumWitnessTables,
+                              genericArgs);
 
   return std::move(callbacks).forGenericMetadata(metadata, description,
-                                                 getCache(generics), key);
+                                                 cache, key);
 }
 
 bool swift::addToMetadataQueue(MetadataCompletionQueueEntry *queueEntry,

stdlib/public/runtime/MetadataCache.h

@@ -354,25 +354,85 @@ class SimpleLockingCacheEntryBase {
 /// A key value as provided to the concurrent map.
 class MetadataCacheKey {
   const void * const *Data;
-  uint32_t Length;
+  uint16_t NumKeyParameters;
+  uint16_t NumWitnessTables;
   uint32_t Hash;
 
+  /// Compare two witness tables, which may involving checking the
+  /// contents of their conformance descriptors.
+  static int compareWitnessTables(const WitnessTable *awt,
+                                  const WitnessTable *bwt) {
+    if (awt == bwt)
+      return 0;
+
+    auto *aDescription = awt->Description;
+    auto *bDescription = bwt->Description;
+    if (aDescription == bDescription)
+      return 0;
+
+    if (!aDescription->isSynthesizedNonUnique() ||
+        !bDescription->isSynthesizedNonUnique())
+      return comparePointers(aDescription, bDescription);
+
+    auto aType = aDescription->getCanonicalTypeMetadata();
+    auto bType = bDescription->getCanonicalTypeMetadata();
+    if (!aType || !bType)
+      return comparePointers(aDescription, bDescription);
+
+    if (int result = comparePointers(aType, bType))
+      return result;
+
+    return comparePointers(aDescription->getProtocol(),
+                           bDescription->getProtocol());
+  }
+
+  /// Compare the content from two keys.
+  static int compareContent(const void * const *adata,
+                            const void * const *bdata,
+                            unsigned numKeyParameters,
+                            unsigned numWitnessTables) {
+    // Compare generic arguments for key parameters.
+    for (unsigned i = 0; i != numKeyParameters; ++i) {
+      if (auto result = comparePointers(*adata++, *bdata++))
+        return result;
+    }
+
+    // Compare witness tables.
+    for (unsigned i = 0; i != numWitnessTables; ++i) {
+      if (auto result =
+              compareWitnessTables((const WitnessTable *)*adata++,
+                                   (const WitnessTable *)*bdata++))
+        return result;
+    }
+
+    return 0;
+  }
+
 public:
-  MetadataCacheKey(const void * const *data, size_t size)
-    : Data(data), Length(size), Hash(computeHash()) {}
-  MetadataCacheKey(const void * const *data, size_t size, uint32_t hash)
-    : Data(data), Length(size), Hash(hash) {}
+  MetadataCacheKey(uint16_t numKeyParams,
+                   uint16_t numWitnessTables,
+                   const void * const *data)
+      : Data(data), NumKeyParameters(numKeyParams),
+        NumWitnessTables(numWitnessTables), Hash(computeHash()) { }
+
+  MetadataCacheKey(uint16_t numKeyParams,
+                   uint16_t numWitnessTables,
+                   const void * const *data,
+                   uint32_t hash)
+    : Data(data), NumKeyParameters(numKeyParams),
+      NumWitnessTables(numWitnessTables), Hash(hash) {}
 
   bool operator==(MetadataCacheKey rhs) const {
+    // Compare the hashes.
+    if (hash() != rhs.hash()) return false;
+
     // Compare the sizes.
-    unsigned asize = size(), bsize = rhs.size();
-    if (asize != bsize) return false;
+    if (NumKeyParameters != rhs.NumKeyParameters) return false;
+    if (NumWitnessTables != rhs.NumWitnessTables) return false;
 
     // Compare the content.
-    auto abegin = begin(), bbegin = rhs.begin();
-    for (unsigned i = 0; i < asize; ++i)
-      if (abegin[i] != bbegin[i]) return false;
-    return true;
+    return compareContent(begin(), rhs.begin(), NumKeyParameters,
+                          NumWitnessTables) == 0;
   }
 
   int compare(const MetadataCacheKey &rhs) const {
@@ -381,38 +441,43 @@ class MetadataCacheKey {
       return hashComparison;
     }
 
-    // Compare the sizes.
-    if (auto sizeComparison = compareIntegers(size(), rhs.size())) {
-      return sizeComparison;
+    // Compare the # of key parameters.
+    if (auto keyParamsComparison =
+            compareIntegers(NumKeyParameters, rhs.NumKeyParameters)) {
+      return keyParamsComparison;
     }
 
-    // Compare the content.
-    auto lbegin = begin(), rbegin = rhs.begin();
-    for (unsigned i = 0, e = size(); i != e; ++i) {
-      if (auto ptrComparison = comparePointers(lbegin[i], rbegin[i]))
-        return ptrComparison;
+    // Compare the # of witness tables.
+    if (auto witnessTablesComparison =
+            compareIntegers(NumWitnessTables, rhs.NumWitnessTables)) {
+      return witnessTablesComparison;
     }
 
-    // Equal.
-    return 0;
+    // Compare the content.
+    return compareContent(begin(), rhs.begin(), NumKeyParameters,
+                          NumWitnessTables);
   }
 
+  uint16_t numKeyParameters() const { return NumKeyParameters; }
+  uint16_t numWitnessTables() const { return NumWitnessTables; }
+
   uint32_t hash() const {
     return Hash;
   }
 
   const void * const *begin() const { return Data; }
-  const void * const *end() const { return Data + Length; }
-  unsigned size() const { return Length; }
+  const void * const *end() const { return Data + size(); }
+  unsigned size() const { return NumKeyParameters + NumWitnessTables; }
 
 private:
   uint32_t computeHash() const {
-    size_t H = 0x56ba80d1 * Length;
-    for (unsigned i = 0; i < Length; i++) {
+    size_t H = 0x56ba80d1 * NumKeyParameters;
+    for (unsigned index = 0; index != NumKeyParameters; ++index) {
       H = (H >> 10) | (H << ((sizeof(size_t) * 8) - 10));
-      H ^= (reinterpret_cast<size_t>(Data[i])
-            ^ (reinterpret_cast<size_t>(Data[i]) >> 19));
+      H ^= (reinterpret_cast<size_t>(Data[index])
+            ^ (reinterpret_cast<size_t>(Data[index]) >> 19));
     }
+
     H *= 0x27d4eb2d;
 
     // Rotate right by 10 and then truncate to 32 bits.
@@ -1270,7 +1335,7 @@ class VariadicMetadataCacheEntryBase :
   using OverloadToken = typename TrailingObjects::template OverloadToken<T>;
 
   size_t numTrailingObjects(OverloadToken<const void *>) const {
-    return KeyLength;
+    return NumKeyParameters + NumWitnessTables;
   }
 
   template <class... Args>
@@ -1284,7 +1349,8 @@ class VariadicMetadataCacheEntryBase :
   // These are arranged to fit into the tail-padding of the superclass.
 
   /// These are set during construction and never changed.
-  const uint16_t KeyLength;
+  const uint16_t NumKeyParameters;
+  const uint16_t NumWitnessTables;
   const uint32_t Hash;
 
   /// Valid if TrackingInfo.getState() >= PrivateMetadataState::Abstract.
@@ -1300,14 +1366,17 @@ class VariadicMetadataCacheEntryBase :
 
 public:
   VariadicMetadataCacheEntryBase(const MetadataCacheKey &key)
-      : KeyLength(key.size()), Hash(key.hash()) {
+      : NumKeyParameters(key.numKeyParameters()),
+        NumWitnessTables(key.numWitnessTables()),
+        Hash(key.hash()) {
     memcpy(this->template getTrailingObjects<const void *>(),
            key.begin(), key.size() * sizeof(const void *));
   }
 
   MetadataCacheKey getKey() const {
-    return MetadataCacheKey(this->template getTrailingObjects<const void*>(),
-                            KeyLength, Hash);
+    return MetadataCacheKey(NumKeyParameters, NumWitnessTables,
+                            this->template getTrailingObjects<const void*>(),
+                            Hash);
   }
 
   intptr_t getKeyIntValueForDump() const {

stdlib/public/runtime/Private.h

@@ -507,6 +507,12 @@ class TypeInfo {
                              const Metadata *type,
                              const ProtocolConformanceDescriptor *conformance);
 
+  /// Determine whether the given type conforms to the given Swift protocol,
+  /// returning the appropriate protocol conformance descriptor when it does.
+  const ProtocolConformanceDescriptor *
+  _conformsToSwiftProtocol(const Metadata * const type,
+                           const ProtocolDescriptor *protocol);
+
   /// Retrieve an associated type witness from the given witness table.
   ///
   /// \param wtable The witness table.