[Serialization] Filter Objective-C methods by mangled name rather than type ID.

Module files store all of the Objective-C method entrypoints in a
central table indexed by selector, then filter the results based on
the specific class being requested. Rather than storing the class as
a TypeID---which requires a bunch of deserialization---store its
mangled name. This allows us to deserialize less, and causes circular
deserialization in rdar://problem/31615640.

lib/Serialization/ModuleFile.cpp

@@ -543,7 +543,7 @@ class ModuleFile::ObjCMethodTableInfo {
 public:
   using internal_key_type = std::string;
   using external_key_type = ObjCSelector;
-  using data_type = SmallVector<std::tuple<TypeID, bool, DeclID>, 8>;
+  using data_type = SmallVector<std::tuple<std::string, bool, DeclID>, 8>;
   using hash_value_type = uint32_t;
   using offset_type = unsigned;
 
@@ -562,7 +562,7 @@ public:
 
   static std::pair<unsigned, unsigned> ReadKeyDataLength(const uint8_t *&data) {
     unsigned keyLength = endian::readNext<uint16_t, little, unaligned>(data);
-    unsigned dataLength = endian::readNext<uint16_t, little, unaligned>(data);
+    unsigned dataLength = endian::readNext<uint32_t, little, unaligned>(data);
     return { keyLength, dataLength };
   }
 
@@ -573,14 +573,16 @@ public:
   static data_type ReadData(internal_key_type key, const uint8_t *data,
                             unsigned length) {
     const constexpr auto recordSize = sizeof(uint32_t) + 1 + sizeof(uint32_t);
-    assert(length % recordSize == 0 && "invalid length");
     data_type result;
     while (length > 0) {
-      TypeID typeID = endian::readNext<uint32_t, little, unaligned>(data);
+      unsigned ownerLen = endian::readNext<uint32_t, little, unaligned>(data);
       bool isInstanceMethod = *data++ != 0;
       DeclID methodID = endian::readNext<uint32_t, little, unaligned>(data);
-      result.push_back(std::make_tuple(typeID, isInstanceMethod, methodID));
-      length -= recordSize;
+      std::string ownerName((const char *)data, ownerLen);
+      result.push_back(
+        std::make_tuple(std::move(ownerName), isInstanceMethod, methodID));
+      data += ownerLen;
+      length -= (recordSize + ownerLen);
     }
 
     return result;
@@ -1565,6 +1567,7 @@ void ModuleFile::loadObjCMethods(
     return;
   }
 
+  std::string ownerName = Mangle::ASTMangler().mangleNominalType(classDecl);
   auto results = *known;
   for (const auto &result : results) {
     // If the method is the wrong kind (instance vs. class), skip it.
@@ -1572,8 +1575,7 @@ void ModuleFile::loadObjCMethods(
       continue;
 
     // If the method isn't defined in the requested class, skip it.
-    Type type = getType(std::get<0>(result));
-    if (type->getClassOrBoundGenericClass() != classDecl)
+    if (std::get<0>(result) != ownerName)
       continue;
 
     // Deserialize the method and add it to the list.