[CodeView] Reduce memory usage in TypeSerializer.

We were using a BumpPtrAllocator to allocate stable storage for
a record, then trying to insert that into a hash table.  If a
collision occurred, the bytes were never inserted and the
allocation was unnecessary.  At the cost of an extra hash
computation, check first if it exists, and only if it does do
we allocate and insert.

llvm-svn: 303407

llvm/include/llvm/DebugInfo/CodeView/TypeSerializer.h

@@ -70,6 +70,8 @@ class TypeSerializer : public TypeVisitorCallbacks {
   MutableArrayRef<uint8_t> getCurrentRecordData();
   Error writeRecordPrefix(TypeLeafKind Kind);
   TypeIndex insertRecordBytesPrivate(MutableArrayRef<uint8_t> Record);
+  TypeIndex insertRecordBytesWithCopy(CVType &Record,
+                                      MutableArrayRef<uint8_t> Data);
 
   Expected<MutableArrayRef<uint8_t>>
   addPadding(MutableArrayRef<uint8_t> Record);

llvm/lib/DebugInfo/CodeView/TypeSerializer.cpp

@@ -66,6 +66,31 @@ TypeSerializer::insertRecordBytesPrivate(MutableArrayRef<uint8_t> Record) {
   return Result.first->getValue();
 }
 
+TypeIndex
+TypeSerializer::insertRecordBytesWithCopy(CVType &Record,
+                                          MutableArrayRef<uint8_t> Data) {
+  assert(Data.size() % 4 == 0 && "Record is not aligned to 4 bytes!");
+
+  StringRef S(reinterpret_cast<const char *>(Data.data()), Data.size());
+
+  // Do a two state lookup / insert so that we don't have to allocate unless
+  // we're going
+  // to do an insert.  This is a big memory savings.
+  auto Iter = HashedRecords.find(S);
+  if (Iter != HashedRecords.end())
+    return Iter->second;
+
+  LastTypeIndex = calcNextTypeIndex();
+  uint8_t *Copy = RecordStorage.Allocate<uint8_t>(Data.size());
+  ::memcpy(Copy, Data.data(), Data.size());
+  Data = MutableArrayRef<uint8_t>(Copy, Data.size());
+  S = StringRef(reinterpret_cast<const char *>(Data.data()), Data.size());
+  HashedRecords.insert(std::make_pair(S, LastTypeIndex));
+  SeenRecords.push_back(Data);
+  Record.RecordData = Data;
+  return LastTypeIndex;
+}
+
 Expected<MutableArrayRef<uint8_t>>
 TypeSerializer::addPadding(MutableArrayRef<uint8_t> Record) {
   uint32_t Align = Record.size() % 4;
@@ -137,11 +162,9 @@ Expected<TypeIndex> TypeSerializer::visitTypeEndGetIndex(CVType &Record) {
       reinterpret_cast<RecordPrefix *>(ThisRecordData.data());
   Prefix->RecordLen = ThisRecordData.size() - sizeof(uint16_t);
 
-  uint8_t *Copy = RecordStorage.Allocate<uint8_t>(ThisRecordData.size());
-  ::memcpy(Copy, ThisRecordData.data(), ThisRecordData.size());
-  ThisRecordData = MutableArrayRef<uint8_t>(Copy, ThisRecordData.size());
-  Record = CVType(*TypeKind, ThisRecordData);
-  TypeIndex InsertedTypeIndex = insertRecordBytesPrivate(ThisRecordData);
+  Record.Type = *TypeKind;
+  TypeIndex InsertedTypeIndex =
+      insertRecordBytesWithCopy(Record, ThisRecordData);
 
   // Write out each additional segment in reverse order, and update each
   // record's continuation index to point to the previous one.