Bitcode: Decouple block info block state from reader.

As proposed on llvm-dev:
http://lists.llvm.org/pipermail/llvm-dev/2016-October/106630.html

Move block info block state to a new class, BitstreamBlockInfo.
Clients may set the block info for a particular cursor with the
BitstreamCursor::setBlockInfo() method.

At this point BitstreamReader is not much more than a container for an
ArrayRef<uint8_t>, so remove it and replace all uses with direct uses
of memory buffers.

Differential Revision: https://reviews.llvm.org/D26259

llvm-svn: 286207

clang/lib/Serialization/ModuleManager.cpp

@@ -135,15 +135,14 @@ ModuleManager::addModule(StringRef FileName, ModuleKind Type,
     }
 
     // Initialize the stream.
-    PCHContainerRdr.ExtractPCH(ModuleEntry->Buffer->getMemBufferRef(),
-                               ModuleEntry->StreamFile);
+    ModuleEntry->Data = PCHContainerRdr.ExtractPCH(*ModuleEntry->Buffer);
   }
 
   if (ExpectedSignature) {
     // If we've not read the control block yet, read the signature eagerly now
     // so that we can check it.
     if (!ModuleEntry->Signature)
-      ModuleEntry->Signature = ReadSignature(ModuleEntry->StreamFile);
+      ModuleEntry->Signature = ReadSignature(ModuleEntry->Data);
 
     if (ModuleEntry->Signature != ExpectedSignature) {
       ErrorStr = ModuleEntry->Signature ? "signature mismatch"