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

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@286207 91177308-0d34-0410-b5e6-96231b3b80d8

include/clang/CodeGen/ObjectFilePCHContainerOperations.h

@@ -35,10 +35,8 @@ class ObjectFilePCHContainerWriter : public PCHContainerWriter {
 class ObjectFilePCHContainerReader : public PCHContainerReader {
   StringRef getFormat() const override { return "obj"; }
 
-  /// Initialize an llvm::BitstreamReader with the serialized
-  /// AST inside the PCH container Buffer.
-  void ExtractPCH(llvm::MemoryBufferRef Buffer,
-                  llvm::BitstreamReader &StreamFile) const override;
+  /// Returns the serialized AST inside the PCH container Buffer.
+  StringRef ExtractPCH(llvm::MemoryBufferRef Buffer) const override;
 };
 }
 

include/clang/Frontend/PCHContainerOperations.h

@@ -17,7 +17,6 @@
 
 namespace llvm {
 class raw_pwrite_stream;
-class BitstreamReader;
 }
 
 using llvm::StringRef;
@@ -63,10 +62,8 @@ public:
   /// Equivalent to the format passed to -fmodule-format=
   virtual StringRef getFormat() const = 0;
 
-  /// Initialize an llvm::BitstreamReader with the serialized AST inside
-  /// the PCH container Buffer.
-  virtual void ExtractPCH(llvm::MemoryBufferRef Buffer,
-                          llvm::BitstreamReader &StreamFile) const = 0;
+  /// Returns the serialized AST inside the PCH container Buffer.
+  virtual StringRef ExtractPCH(llvm::MemoryBufferRef Buffer) const = 0;
 };
 
 /// Implements write operations for a raw pass-through PCH container.
@@ -87,9 +84,8 @@ class RawPCHContainerWriter : public PCHContainerWriter {
 class RawPCHContainerReader : public PCHContainerReader {
   StringRef getFormat() const override { return "raw"; }
 
-  /// Initialize an llvm::BitstreamReader with Buffer.
-  void ExtractPCH(llvm::MemoryBufferRef Buffer,
-                  llvm::BitstreamReader &StreamFile) const override;
+  /// Simply returns the buffer contained in Buffer.
+  StringRef ExtractPCH(llvm::MemoryBufferRef Buffer) const override;
 };
 
 /// A registry of PCHContainerWriter and -Reader objects for different formats.

include/clang/Serialization/Module.h

@@ -173,8 +173,8 @@ public:
   /// \brief The global bit offset (or base) of this module
   uint64_t GlobalBitOffset;
 
-  /// \brief The bitstream reader from which we'll read the AST file.
-  llvm::BitstreamReader StreamFile;
+  /// \brief The serialized bitstream data for this file.
+  StringRef Data;
 
   /// \brief The main bitstream cursor for the main block.
   llvm::BitstreamCursor Stream;

include/clang/Serialization/ModuleManager.h

@@ -175,7 +175,7 @@ public:
     OutOfDate
   };
 
-  typedef ASTFileSignature(*ASTFileSignatureReader)(llvm::BitstreamReader &);
+  typedef ASTFileSignature(*ASTFileSignatureReader)(StringRef);
 
   /// \brief Attempts to create a new module and add it to the list of known
   /// modules.

lib/CodeGen/ObjectFilePCHContainerOperations.cpp

@@ -312,8 +312,9 @@ ObjectFilePCHContainerWriter::CreatePCHContainerGenerator(
       CI, MainFileName, OutputFileName, std::move(OS), Buffer);
 }
 
-void ObjectFilePCHContainerReader::ExtractPCH(
-    llvm::MemoryBufferRef Buffer, llvm::BitstreamReader &StreamFile) const {
+StringRef
+ObjectFilePCHContainerReader::ExtractPCH(llvm::MemoryBufferRef Buffer) const {
+  StringRef PCH;
   auto OFOrErr = llvm::object::ObjectFile::createObjectFile(Buffer);
   if (OFOrErr) {
     auto &OF = OFOrErr.get();
@@ -323,10 +324,8 @@ void ObjectFilePCHContainerReader::ExtractPCH(
       StringRef Name;
       Section.getName(Name);
       if ((!IsCOFF && Name == "__clangast") || (IsCOFF && Name == "clangast")) {
-        StringRef Buf;
-        Section.getContents(Buf);
-        StreamFile = llvm::BitstreamReader(Buf);
-        return;
+        Section.getContents(PCH);
+        return PCH;
       }
     }
   }
@@ -334,8 +333,9 @@ void ObjectFilePCHContainerReader::ExtractPCH(
     if (EIB.convertToErrorCode() ==
         llvm::object::object_error::invalid_file_type)
       // As a fallback, treat the buffer as a raw AST.
-      StreamFile = llvm::BitstreamReader(Buffer);
+      PCH = Buffer.getBuffer();
     else
       EIB.log(llvm::errs());
   });
+  return PCH;
 }

lib/Frontend/PCHContainerOperations.cpp

@@ -58,9 +58,9 @@ std::unique_ptr<ASTConsumer> RawPCHContainerWriter::CreatePCHContainerGenerator(
   return llvm::make_unique<RawPCHContainerGenerator>(std::move(OS), Buffer);
 }
 
-void RawPCHContainerReader::ExtractPCH(
-    llvm::MemoryBufferRef Buffer, llvm::BitstreamReader &StreamFile) const {
-  StreamFile = llvm::BitstreamReader(Buffer);
+StringRef
+RawPCHContainerReader::ExtractPCH(llvm::MemoryBufferRef Buffer) const {
+  return Buffer.getBuffer();
 }
 
 PCHContainerOperations::PCHContainerOperations() {

lib/Frontend/SerializedDiagnosticReader.cpp

@@ -24,8 +24,8 @@ std::error_code SerializedDiagnosticReader::readDiagnostics(StringRef File) {
   if (!Buffer)
     return SDError::CouldNotLoad;
 
-  llvm::BitstreamReader StreamFile(**Buffer);
-  llvm::BitstreamCursor Stream(StreamFile);
+  llvm::BitstreamCursor Stream(**Buffer);
+  Optional<llvm::BitstreamBlockInfo> BlockInfo;
 
   // Sniff for the signature.
   if (Stream.Read(8) != 'D' ||
@@ -41,10 +41,13 @@ std::error_code SerializedDiagnosticReader::readDiagnostics(StringRef File) {
 
     std::error_code EC;
     switch (Stream.ReadSubBlockID()) {
-    case llvm::bitc::BLOCKINFO_BLOCK_ID:
-      if (Stream.ReadBlockInfoBlock())
+    case llvm::bitc::BLOCKINFO_BLOCK_ID: {
+      BlockInfo = Stream.ReadBlockInfoBlock();
+      if (!BlockInfo)
         return SDError::MalformedBlockInfoBlock;
+      Stream.setBlockInfo(&*BlockInfo);
       continue;
+    }
     case BLOCK_META:
       if ((EC = readMetaBlock(Stream)))
         return EC;

lib/Serialization/ASTReader.cpp

@@ -1711,7 +1711,7 @@ void ASTReader::ReadDefinedMacros() {
     BitstreamCursor &MacroCursor = I->MacroCursor;
 
     // If there was no preprocessor block, skip this file.
-    if (!MacroCursor.getBitStreamReader())
+    if (MacroCursor.getBitcodeBytes().empty())
       continue;
 
     BitstreamCursor Cursor = MacroCursor;
@@ -3798,7 +3798,7 @@ ASTReader::ASTReadResult ASTReader::ReadAST(StringRef FileName,
   return Success;
 }
 
-static ASTFileSignature readASTFileSignature(llvm::BitstreamReader &StreamFile);
+static ASTFileSignature readASTFileSignature(StringRef PCH);
 
 /// \brief Whether \p Stream starts with the AST/PCH file magic number 'CPCH'.
 static bool startsWithASTFileMagic(BitstreamCursor &Stream) {
@@ -3885,8 +3885,7 @@ ASTReader::ReadASTCore(StringRef FileName,
 
   ModuleFile &F = *M;
   BitstreamCursor &Stream = F.Stream;
-  PCHContainerRdr.ExtractPCH(F.Buffer->getMemBufferRef(), F.StreamFile);
-  Stream.init(&F.StreamFile);
+  Stream = BitstreamCursor(PCHContainerRdr.ExtractPCH(*F.Buffer));
   F.SizeInBits = F.Buffer->getBufferSize() * 8;
   
   // Sniff for the signature.
@@ -4175,10 +4174,10 @@ void ASTReader::finalizeForWriting() {
   // Nothing to do for now.
 }
 
-/// \brief Reads and return the signature record from \p StreamFile's control
-/// block, or else returns 0.
-static ASTFileSignature readASTFileSignature(llvm::BitstreamReader &StreamFile){
-  BitstreamCursor Stream(StreamFile);
+/// \brief Reads and return the signature record from \p PCH's control block, or
+/// else returns 0.
+static ASTFileSignature readASTFileSignature(StringRef PCH) {
+  BitstreamCursor Stream(PCH);
   if (!startsWithASTFileMagic(Stream))
     return 0;
 
@@ -4216,9 +4215,7 @@ std::string ASTReader::getOriginalSourceFile(
   }
 
   // Initialize the stream
-  llvm::BitstreamReader StreamFile;
-  PCHContainerRdr.ExtractPCH((*Buffer)->getMemBufferRef(), StreamFile);
-  BitstreamCursor Stream(StreamFile);
+  BitstreamCursor Stream(PCHContainerRdr.ExtractPCH(**Buffer));
 
   // Sniff for the signature.
   if (!startsWithASTFileMagic(Stream)) {
@@ -4318,9 +4315,7 @@ bool ASTReader::readASTFileControlBlock(
   }
 
   // Initialize the stream
-  llvm::BitstreamReader StreamFile;
-  PCHContainerRdr.ExtractPCH((*Buffer)->getMemBufferRef(), StreamFile);
-  BitstreamCursor Stream(StreamFile);
+  BitstreamCursor Stream(PCHContainerRdr.ExtractPCH(**Buffer));
 
   // Sniff for the signature.
   if (!startsWithASTFileMagic(Stream))

lib/Serialization/GlobalModuleIndex.cpp

@@ -245,11 +245,8 @@ GlobalModuleIndex::readIndex(StringRef Path) {
     return std::make_pair(nullptr, EC_NotFound);
   std::unique_ptr<llvm::MemoryBuffer> Buffer = std::move(BufferOrErr.get());
 
-  /// \brief The bitstream reader from which we'll read the AST file.
-  llvm::BitstreamReader Reader(*Buffer);
-
   /// \brief The main bitstream cursor for the main block.
-  llvm::BitstreamCursor Cursor(Reader);
+  llvm::BitstreamCursor Cursor(*Buffer);
 
   // Sniff for the signature.
   if (Cursor.Read(8) != 'B' ||
@@ -503,9 +500,7 @@ bool GlobalModuleIndexBuilder::loadModuleFile(const FileEntry *File) {
   }
 
   // Initialize the input stream
-  llvm::BitstreamReader InStreamFile;
-  PCHContainerRdr.ExtractPCH((*Buffer)->getMemBufferRef(), InStreamFile);
-  llvm::BitstreamCursor InStream(InStreamFile);
+  llvm::BitstreamCursor InStream(PCHContainerRdr.ExtractPCH(**Buffer));
 
   // Sniff for the signature.
   if (InStream.Read(8) != 'C' ||

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"