[Runtime] Support type descriptor map in LibPrespecialized.

include/swift/Runtime/EnvironmentVariables.h

@@ -30,14 +30,24 @@ extern swift::once_t initializeToken;
 using string = const char *;
 
 // Declare backing variables.
-#define VARIABLE(name, type, defaultValue, help) extern type name ## _variable;
+#define VARIABLE(name, type, defaultValue, help)                               \
+  extern type name##_variable;                                                 \
+  extern bool name##_isSet_variable;
 #include "../../../stdlib/public/runtime/EnvironmentVariables.def"
 
-// Define getter functions.
+// Define getter functions. This creates one function with the same name as the
+// variable which returns the value set for that variable, and second function
+// ending in _isSet which returns a boolean indicating whether the variable was
+// set at all, to allow detecting when the variable was explicitly set to the
+// same value as the default.
 #define VARIABLE(name, type, defaultValue, help)                               \
   inline type name() {                                                         \
     swift::once(initializeToken, initialize, nullptr);                         \
     return name##_variable;                                                    \
+  }                                                                            \
+  inline bool name##_isSet() {                                                 \
+    swift::once(initializeToken, initialize, nullptr);                         \
+    return name##_isSet_variable;                                              \
   }
 #include "../../../stdlib/public/runtime/EnvironmentVariables.def"
 

include/swift/Runtime/LibPrespecialized.h

@@ -20,6 +20,7 @@
 #include "PrebuiltStringMap.h"
 #include "swift/ABI/Metadata.h"
 #include "swift/ABI/TargetLayout.h"
+#include "swift/Demangling/Demangler.h"
 
 #define LIB_PRESPECIALIZED_TOP_LEVEL_SYMBOL_NAME "_swift_prespecializationsData"
 
@@ -36,23 +37,44 @@ struct LibPrespecializedData {
 
   typename Runtime::StoredSize optionFlags;
 
+  TargetPointer<Runtime, const void> descriptorMap;
+
   // Existing fields are above, add new fields below this point.
 
+  // The major/minor version numbers for this version of the struct.
   static constexpr uint32_t currentMajorVersion = 1;
-  static constexpr uint32_t currentMinorVersion = 3;
+  static constexpr uint32_t currentMinorVersion = 4;
 
+  // Version numbers where various fields were introduced.
   static constexpr uint32_t minorVersionWithDisabledProcessesTable = 2;
   static constexpr uint32_t minorVersionWithPointerKeyedMetadataMap = 3;
   static constexpr uint32_t minorVersionWithOptionFlags = 3;
+  static constexpr uint32_t minorVersionWithDescriptorMap = 4;
 
   // Option flags values.
   enum : typename Runtime::StoredSize {
     // When this flag is set, the runtime should default to using the
     // pointer-keyed table. When not set, default to using the name-keyed table.
     OptionFlagDefaultToPointerKeyedMap = 1ULL << 0,
+
+    // When this flag is set, the runtime should default to using the descriptor
+    // map. When not set, default to turning off the descriptor map.
+    OptionFlagDescriptorMapDefaultOn = 1ULL << 1,
+
+    // When this flag is set, descriptorMap is not comprehensive, meaning that
+    // a negative lookup result is not a definitive failure.
+    OptionFlagDescriptorMapNotComprehensive = 1ULL << 2,
   };
 
-  // Helpers for retrieving the metadata map in-process.
+  // Helpers for safely retrieving various fields. Helpers return 0 or NULL if
+  // the version number indicates that the field is not present.
+
+  typename Runtime::StoredSize getOptionFlags() const {
+    if (minorVersion < minorVersionWithOptionFlags)
+      return 0;
+    return optionFlags;
+  }
+
   static bool stringIsNull(const char *str) { return str == nullptr; }
 
   using MetadataMap = PrebuiltStringMap<const char *, Metadata *, stringIsNull>;
@@ -73,18 +95,141 @@ struct LibPrespecializedData {
     return pointerKeyedMetadataMap;
   }
 
-  typename Runtime::StoredSize getOptionFlags() const {
-    if (minorVersion < minorVersionWithOptionFlags)
-      return 0;
-    return optionFlags;
+  using DescriptorMap =
+      PrebuiltAuxDataImplicitStringMap<TargetPointer<Runtime, const void>,
+                                       uint16_t>;
+
+  const DescriptorMap *getDescriptorMap() const {
+    if (minorVersion < minorVersionWithDescriptorMap)
+      return nullptr;
+    return reinterpret_cast<const DescriptorMap *>(descriptorMap);
   }
 };
 
+enum class LibPrespecializedLookupResult {
+  // We found something.
+  Found,
+
+  // We didn't find anything, and we know it's not in the shared cache.
+  DefinitiveNotFound,
+
+  // We didn't find anything, but we couldn't rule out the shared cache. Caller
+  // must do a full search.
+  NonDefinitiveNotFound,
+};
+
 const LibPrespecializedData<InProcess> *getLibPrespecializedData();
+
 Metadata *getLibPrespecializedMetadata(const TypeContextDescriptor *description,
                                        const void *const *arguments);
 void libPrespecializedImageLoaded();
 
+std::pair<LibPrespecializedLookupResult, const TypeContextDescriptor *>
+getLibPrespecializedTypeDescriptor(Demangle::NodePointer node);
+
+/// Given the demangling referring to a particular descriptor, build the
+/// canonical simplified version of the demangling that's used for the keys in
+/// the descriptorMap. We copy across Extension and Module nodes. Type nodes are
+/// all normalized to be OtherNominalType to allow for the runtime allowing
+/// type kind mismatches on imported C types in certain cases. Other nodes are
+/// skipped.
+///
+/// The runtime always searches through duplicates in the table, and uses its
+/// own matching on all candidates, so the simplified demangling is allowed to
+/// be simplified to the point of having different descriptors sometimes produce
+/// the same demangling.
+static inline Demangle::NodePointer
+buildSimplifiedDescriptorDemangling(Demangle::NodePointer node,
+                                    Demangle::Demangler &dem) {
+  // The node that will be returned to the caller.
+  Demangle::NodePointer result = nullptr;
+
+  // The bottommost node in the result that we've generated. Additional nodes
+  // are added as children to this one.
+  Demangle::NodePointer resultBottom = nullptr;
+
+  // The current node that we're iterating over in the input node tree.
+  Demangle::NodePointer current = node;
+
+  using Kind = Demangle::Node::Kind;
+
+  // Helper to add a new node to the result. This sets `result` to the node if
+  // it hasn't already been set (indicating this is the topmost node), and adds
+  // the node as a child to `resultBottom` otherwise. `resultBottom` is updated
+  // to point to the new node.
+  auto addNode = [&](Demangle::NodePointer newNode) {
+    if (!result) {
+      result = newNode;
+    } else {
+      if (resultBottom->getKind() == Kind::Extension) {
+        resultBottom->addChild(newNode, dem);
+      } else {
+        // Shift the Identifier down, insert before it.
+        resultBottom->addChild(resultBottom->getFirstChild(), dem);
+        resultBottom->replaceChild(0, newNode);
+      }
+    }
+    resultBottom = newNode;
+  };
+
+  // Walk down the input node tree.
+  while (current) {
+    switch (current->getKind()) {
+    case Kind::Extension: {
+      // Extensions are copied across. The new extension node has the module
+      // from the original, and the second child will be added as we traverse
+      // the next node in the tree.
+      auto copy = dem.createNode(Kind::Extension);
+      auto module = current->getChild(0);
+      if (module == nullptr || module->getKind() != Kind::Module)
+        return nullptr;
+      copy->addChild(module, dem);
+      addNode(copy);
+      current = current->getChild(1);
+      break;
+    }
+    case Kind::Module: {
+      // Module contents are always in the form we want, so we can incorporate
+      // this node verbatim and terminate the walk.
+      addNode(current);
+      current = nullptr;
+      break;
+    }
+    case Kind::Protocol: {
+      // Bring Protocol nodes across verbatim, there's no fuzzy matching.
+      addNode(current);
+      current = nullptr;
+      break;
+    }
+    case Kind::OpaqueType:
+    case Kind::Class:
+    case Kind::Structure:
+    case Kind::Enum:
+    case Kind::TypeAlias:
+    case Kind::OtherNominalType: {
+      // Type nodes are copied across with the kind always set to
+      // OtherNominalType.
+      auto copy = dem.createNode(Kind::OtherNominalType);
+      auto identifier = current->getChild(1);
+      if (identifier == nullptr || identifier->getKind() != Kind::Identifier)
+        return nullptr;
+      copy->addChild(identifier, dem);
+      addNode(copy);
+      current = current->getChild(0);
+      break;
+    }
+
+    default:
+      // If we don't know about this node, continue the walk with its first
+      // child.
+      current = current->getFirstChild();
+      break;
+    }
+  }
+
+  return result;
+}
+
 } // namespace swift
 
 // Validate the prespecialized metadata map by building each entry dynamically