IR, Bitcode: Change bitcode reader to no longer own its memory buffer.

[pcc]

Summary

Unique ownership is just one possible ownership pattern for the memory buffer
underlying the bitcode reader. In practice, as this patch shows, ownership can
often reside at a higher level. With the upcoming change to allow multiple
modules in a single bitcode file, it will no longer be appropriate for
modules to generally have unique ownership of their memory buffer.

The C API exposes the ownership relation via the LLVMGetBitcodeModuleInContext
and LLVMGetBitcodeModuleInContext2 functions, so we still need some way for
the module to own the memory buffer. This patch does so by adding an owned
memory buffer field to Module, and using it in a few other places where it
is convenient.

[mehdi_amini]

llvm/include/llvm/IR/Module.h

164

What other legacy clients do we have? Is it only the C API? The C API can be handled differently: it can have its own wrapper struct around the Module class, and this wrapper would own the buffer.

[mehdi_amini]

LGTM, with one nit inline.

llvm/include/llvm/IR/Module.h

811

take seems reversed here, I usually see it the opposite way: when the client of the API takes ownership of something that is owned by the object.

clang/lib/CodeGen/CodeGenAction.cpp

for (auto &I : CI.getCodeGenOpts().LinkBitcodeFiles) {
       if (!BCBuf) {
         CI.getDiagnostics().Report(diag::err_cannot_open_file)
             << LinkBCFile << BCBuf.getError().message();
         LinkModules.clear();
         return nullptr;
       }
 
       ErrorOr<std::unique_ptr<llvm::Module>> ModuleOrErr =
-          getLazyBitcodeModule(std::move(*BCBuf), *VMContext);
+          getOwningLazyBitcodeModule(std::move(*BCBuf), *VMContext);
       if (std::error_code EC = ModuleOrErr.getError()) {
         CI.getDiagnostics().Report(diag::err_cannot_open_file) << LinkBCFile
                                                                << EC.message();
         LinkModules.clear();
         return nullptr;
       }
       addLinkModule(ModuleOrErr.get().release(), I.first);
     }

llvm/include/llvm/Bitcode/ReaderWriter.h

namespace llvm {
   static const unsigned BWH_VersionField = 1*4;
   static const unsigned BWH_OffsetField = 2*4;
   static const unsigned BWH_SizeField = 3*4;
   static const unsigned BWH_CPUTypeField = 4*4;
   static const unsigned BWH_HeaderSize = 5*4;
 
   /// Read the header of the specified bitcode buffer and prepare for lazy
   /// deserialization of function bodies. If ShouldLazyLoadMetadata is true,
-  /// lazily load metadata as well. If successful, this moves Buffer. On
+  /// lazily load metadata as well.
+  ErrorOr<std::unique_ptr<Module>>
+  getLazyBitcodeModule(MemoryBufferRef Buffer, LLVMContext &Context,
+                       bool ShouldLazyLoadMetadata = false);
+
+  /// Like getLazyBitcodeModule, except that the module takes ownership of
+  /// the memory buffer if successful. If successful, this moves Buffer. On
   /// error, this *does not* move Buffer.
   ErrorOr<std::unique_ptr<Module>>
-  getLazyBitcodeModule(std::unique_ptr<MemoryBuffer> &&Buffer,
+  getOwningLazyBitcodeModule(std::unique_ptr<MemoryBuffer> &&Buffer,
                              LLVMContext &Context,
                              bool ShouldLazyLoadMetadata = false);
 
   /// Read the header of the specified bitcode buffer and extract just the
   /// triple information. If successful, this returns a string. On error, this
   /// returns "".
   std::string getBitcodeTargetTriple(MemoryBufferRef Buffer,
                                      LLVMContext &Context);
 
   /// Return true if \p Buffer contains a bitcode file with ObjC code (category

llvm/include/llvm/IR/Module.h

 #include "llvm/Support/DataTypes.h"
 #include <system_error>
 
 namespace llvm {
 template <typename T> class Optional;
 class FunctionType;
 class GVMaterializer;
 class LLVMContext;
+class MemoryBuffer;
 class RandomNumberGenerator;
 class StructType;
 template <class PtrType> class SmallPtrSetImpl;
 
 /// A Module instance is used to store all the information related to an
 /// LLVM module. Modules are the top level container of all other LLVM
 /// Intermediate Representation (IR) objects. Each module directly contains a
 /// list of globals variables, a list of functions, a list of libraries (or
private:
   GlobalListType GlobalList;      ///< The Global Variables in the module
   FunctionListType FunctionList;  ///< The Functions in the module
   AliasListType AliasList;        ///< The Aliases in the module
   IFuncListType IFuncList;        ///< The IFuncs in the module
   NamedMDListType NamedMDList;    ///< The named metadata in the module
   std::string GlobalScopeAsm;     ///< Inline Asm at global scope.
   ValueSymbolTable *ValSymTab;    ///< Symbol table for values
   ComdatSymTabType ComdatSymTab;  ///< Symbol table for COMDATs
+  std::unique_ptr<MemoryBuffer>
+  OwnedMemoryBuffer;              ///< Memory buffer directly owned by this
+                                  ///< module, for legacy clients only.
   std::unique_ptr<GVMaterializer>
   Materializer;                   ///< Used to materialize GlobalValues
   std::string ModuleID;           ///< Human readable identifier for the module
   std::string SourceFileName;     ///< Original source file name for module,
                                   ///< recorded in bitcode.
   std::string TargetTriple;       ///< Platform target triple Module compiled on
                                   ///< Format: (arch)(sub)-(vendor)-(sys0-(abi)
   void *NamedMDSymTab;            ///< NamedMDNode names.
/// @}
   /// @{
 
   /// \brief Attach profile summary metadata to this module.
   void setProfileSummary(Metadata *M);
 
   /// \brief Returns profile summary metadata
   Metadata *getProfileSummary();
   /// @}
+
+  /// Take ownership of the given memory buffer.
+  void takeMemoryBuffer(std::unique_ptr<MemoryBuffer> MB);
 };
 
 /// \brief Given "llvm.used" or "llvm.compiler.used" as a global name, collect
 /// the initializer elements of that global in Set and return the global itself.
 GlobalVariable *collectUsedGlobalVariables(const Module &M,
                                            SmallPtrSetImpl<GlobalValue *> &Set,
                                            bool CompilerUsed);
 

llvm/lib/Bitcode/Reader/BitReader.cpp

LLVMContext::DiagnosticHandlerTy OldDiagnosticHandler =
       Ctx.getDiagnosticHandler();
   void *OldDiagnosticContext = Ctx.getDiagnosticContext();
 
   std::string Message;
   Ctx.setDiagnosticHandler(diagnosticHandler, &Message, true);
   std::unique_ptr<MemoryBuffer> Owner(unwrap(MemBuf));
 
   ErrorOr<std::unique_ptr<Module>> ModuleOrErr =
-      getLazyBitcodeModule(std::move(Owner), Ctx);
+      getOwningLazyBitcodeModule(std::move(Owner), Ctx);
   Owner.release();
   Ctx.setDiagnosticHandler(OldDiagnosticHandler, OldDiagnosticContext, true);
 
   if (ModuleOrErr.getError()) {
     *OutM = wrap((Module *)nullptr);
     if (OutMessage)
       *OutMessage = strdup(Message.c_str());
     return 1;
   }
 
   *OutM = wrap(ModuleOrErr.get().release());
 
   return 0;
 }
 
 LLVMBool LLVMGetBitcodeModuleInContext2(LLVMContextRef ContextRef,
                                         LLVMMemoryBufferRef MemBuf,
                                         LLVMModuleRef *OutM) {
   LLVMContext &Ctx = *unwrap(ContextRef);
   std::unique_ptr<MemoryBuffer> Owner(unwrap(MemBuf));
 
   ErrorOr<std::unique_ptr<Module>> ModuleOrErr =
-      getLazyBitcodeModule(std::move(Owner), Ctx);
+      getOwningLazyBitcodeModule(std::move(Owner), Ctx);
   Owner.release();
 
   if (ModuleOrErr.getError()) {
     *OutM = wrap((Module *)nullptr);
     return 1;
   }
 
   *OutM = wrap(ModuleOrErr.get().release());

llvm/lib/Bitcode/Reader/BitcodeReader.cpp

public:
   Metadata *upgradeTypeRefArray(Metadata *MaybeTuple);
 
 private:
   Metadata *resolveTypeRefArray(Metadata *MaybeTuple);
 };
 
 class BitcodeReaderBase {
 protected:
-  BitcodeReaderBase(MemoryBuffer *Buffer) : Buffer(Buffer) {}
+  BitcodeReaderBase(MemoryBufferRef Buffer) : Buffer(Buffer) {}
 
-  std::unique_ptr<MemoryBuffer> Buffer;
+  MemoryBufferRef Buffer;
   BitstreamBlockInfo BlockInfo;
   BitstreamCursor Stream;
 
   std::error_code initStream();
   bool readBlockInfo();
 
   virtual std::error_code error(const Twine &Message) = 0;
   virtual ~BitcodeReaderBase() = default;
 };
 
 std::error_code BitcodeReaderBase::initStream() {
-  const unsigned char *BufPtr = (const unsigned char*)Buffer->getBufferStart();
-  const unsigned char *BufEnd = BufPtr+Buffer->getBufferSize();
+  const unsigned char *BufPtr = (const unsigned char*)Buffer.getBufferStart();
+  const unsigned char *BufEnd = BufPtr+Buffer.getBufferSize();
 
-  if (Buffer->getBufferSize() & 3)
+  if (Buffer.getBufferSize() & 3)
     return error("Invalid bitcode signature");
 
   // If we have a wrapper header, parse it and ignore the non-bc file contents.
   // The magic number is 0x0B17C0DE stored in little endian.
   if (isBitcodeWrapper(BufPtr, BufEnd))
     if (SkipBitcodeWrapperHeader(BufPtr, BufEnd, true))
       return error("Invalid bitcode wrapper header");
 
class BitcodeReader : public BitcodeReaderBase, public GVMaterializer {
   SmallDenseMap<Function *, DISubprogram *, 16> FunctionsWithSPs;
 
   std::vector<std::string> BundleTags;
 
 public:
   std::error_code error(BitcodeError E, const Twine &Message);
   std::error_code error(const Twine &Message) override;
 
-  BitcodeReader(MemoryBuffer *Buffer, LLVMContext &Context);
-  ~BitcodeReader() override { freeState(); }
+  BitcodeReader(MemoryBufferRef Buffer, LLVMContext &Context);
 
   std::error_code materializeForwardReferencedFunctions();
 
-  void freeState();
-
-  void releaseBuffer();
-
   std::error_code materialize(GlobalValue *GV) override;
   std::error_code materializeModule() override;
   std::vector<StructType *> getIdentifiedStructTypes() const override;
 
   /// \brief Main interface to parsing a bitcode buffer.
   /// \returns true if an error occurred.
   std::error_code parseBitcodeInto(Module *M,
                                    bool ShouldLazyLoadMetadata = false);
class ModuleSummaryIndexBitcodeReader : public BitcodeReaderBase {
 
   /// Original source file name recorded in a bitcode record.
   std::string SourceFileName;
 
 public:
   std::error_code error(const Twine &Message);
 
   ModuleSummaryIndexBitcodeReader(
-      MemoryBuffer *Buffer, DiagnosticHandlerFunction DiagnosticHandler,
+      MemoryBufferRef Buffer, DiagnosticHandlerFunction DiagnosticHandler,
       bool CheckGlobalValSummaryPresenceOnly = false);
-  ~ModuleSummaryIndexBitcodeReader() { freeState(); }
-
-  void freeState();
-
-  void releaseBuffer();
 
   /// Check if the parser has encountered a summary section.
   bool foundGlobalValSummary() { return SeenGlobalValSummary; }
 
   /// \brief Main interface to parsing a bitcode buffer.
   /// \returns true if an error occurred.
   std::error_code parseSummaryIndexInto(ModuleSummaryIndex *I);
 
if (!ProducerIdentification.empty()) {
     return ::error(Context, make_error_code(BitcodeError::CorruptedBitcode),
                    Message + " (Producer: '" + ProducerIdentification +
                        "' Reader: 'LLVM " + LLVM_VERSION_STRING "')");
   }
   return ::error(Context, make_error_code(BitcodeError::CorruptedBitcode),
                  Message);
 }
 
-BitcodeReader::BitcodeReader(MemoryBuffer *Buffer, LLVMContext &Context)
+BitcodeReader::BitcodeReader(MemoryBufferRef Buffer, LLVMContext &Context)
     : BitcodeReaderBase(Buffer), Context(Context), ValueList(Context),
       MetadataList(Context) {}
 
 std::error_code BitcodeReader::materializeForwardReferencedFunctions() {
   if (WillMaterializeAllForwardRefs)
     return std::error_code();
 
   // Prevent recursion.
std::error_code BitcodeReader::materializeForwardReferencedFunctions() {
   }
   assert(BasicBlockFwdRefs.empty() && "Function missing from queue");
 
   // Reset state.
   WillMaterializeAllForwardRefs = false;
   return std::error_code();
 }
 
-void BitcodeReader::freeState() {
-  Buffer = nullptr;
-  std::vector<Type*>().swap(TypeList);
-  ValueList.clear();
-  MetadataList.clear();
-  std::vector<Comdat *>().swap(ComdatList);
-
-  std::vector<AttributeSet>().swap(MAttributes);
-  std::vector<BasicBlock*>().swap(FunctionBBs);
-  std::vector<Function*>().swap(FunctionsWithBodies);
-  DeferredFunctionInfo.clear();
-  DeferredMetadataInfo.clear();
-  MDKindMap.clear();
-
-  assert(BasicBlockFwdRefs.empty() && "Unresolved blockaddress fwd references");
-  BasicBlockFwdRefQueue.clear();
-}
-
 //===----------------------------------------------------------------------===//
 //  Helper functions to implement forward reference resolution, etc.
 //===----------------------------------------------------------------------===//
 
 /// Convert a string from a record into an std::string, return true on failure.
 template <typename StrTy>
 static bool convertToString(ArrayRef<uint64_t> Record, unsigned Idx,
                             StrTy &Result) {
std::error_code BitcodeReader::findFunctionInStream(
   }
   return std::error_code();
 }
 
 //===----------------------------------------------------------------------===//
 // GVMaterializer implementation
 //===----------------------------------------------------------------------===//
 
-void BitcodeReader::releaseBuffer() { Buffer.release(); }
-
 std::error_code BitcodeReader::materialize(GlobalValue *GV) {
   Function *F = dyn_cast<Function>(GV);
   // If it's not a function or is already material, ignore the request.
   if (!F || !F->isMaterializable())
     return std::error_code();
 
   DenseMap<Function*, uint64_t>::iterator DFII = DeferredFunctionInfo.find(F);
   assert(DFII != DeferredFunctionInfo.end() && "Deferred function not found!");

 }
 
 std::error_code ModuleSummaryIndexBitcodeReader::error(const Twine &Message) {
   return ::error(DiagnosticHandler,
                  make_error_code(BitcodeError::CorruptedBitcode), Message);
 }
 
 ModuleSummaryIndexBitcodeReader::ModuleSummaryIndexBitcodeReader(
-    MemoryBuffer *Buffer, DiagnosticHandlerFunction DiagnosticHandler,
+    MemoryBufferRef Buffer, DiagnosticHandlerFunction DiagnosticHandler,
     bool CheckGlobalValSummaryPresenceOnly)
     : BitcodeReaderBase(Buffer),
       DiagnosticHandler(std::move(DiagnosticHandler)),
       CheckGlobalValSummaryPresenceOnly(CheckGlobalValSummaryPresenceOnly) {}
 
-void ModuleSummaryIndexBitcodeReader::freeState() { Buffer = nullptr; }
-
-void ModuleSummaryIndexBitcodeReader::releaseBuffer() { Buffer.release(); }
-
 std::pair<GlobalValue::GUID, GlobalValue::GUID>
 ModuleSummaryIndexBitcodeReader::getGUIDFromValueId(unsigned ValueId) {
   auto VGI = ValueIdToCallGraphGUIDMap.find(ValueId);
   assert(VGI != ValueIdToCallGraphGUIDMap.end());
   return VGI->second;
 }
 
 // Specialized value symbol table parser used when reading module index
case BitstreamEntry::Record: {
         /// MODULE_CODE_HASH: [5*i32]
         case bitc::MODULE_CODE_HASH: {
           if (Record.size() != 5)
             return error("Invalid hash length " + Twine(Record.size()).str());
           if (!TheIndex)
             break;
           if (TheIndex->modulePaths().empty())
             // We always seed the index with the module.
-            TheIndex->addModulePath(Buffer->getBufferIdentifier(), 0);
+            TheIndex->addModulePath(Buffer.getBufferIdentifier(), 0);
           if (TheIndex->modulePaths().size() != 1)
             return error("Don't expect multiple modules defined?");
           auto &Hash = TheIndex->modulePaths().begin()->second.second;
           int Pos = 0;
           for (auto &Val : Record) {
             assert(!(Val >> 32) && "Unexpected high bits set");
             Hash[Pos++] = Val;
           }
case bitc::FS_PERMODULE_PROFILE: {
       std::unique_ptr<FunctionSummary> FS =
           llvm::make_unique<FunctionSummary>(Flags, InstCount);
       // The module path string ref set in the summary must be owned by the
       // index's module string table. Since we don't have a module path
       // string table section in the per-module index, we create a single
       // module path string table entry with an empty (0) ID to take
       // ownership.
       FS->setModulePath(
-          TheIndex->addModulePath(Buffer->getBufferIdentifier(), 0)->first());
+          TheIndex->addModulePath(Buffer.getBufferIdentifier(), 0)->first());
       static int RefListStartIndex = 4;
       int CallGraphEdgeStartIndex = RefListStartIndex + NumRefs;
       assert(Record.size() >= RefListStartIndex + NumRefs &&
              "Record size inconsistent with number of references");
       for (unsigned I = 4, E = CallGraphEdgeStartIndex; I != E; ++I) {
         unsigned RefValueId = Record[I];
         GlobalValue::GUID RefGUID = getGUIDFromValueId(RefValueId).first;
         FS->addRefEdge(RefGUID);
case bitc::FS_ALIAS: {
       auto Flags = getDecodedGVSummaryFlags(RawFlags, Version);
       std::unique_ptr<AliasSummary> AS = llvm::make_unique<AliasSummary>(Flags);
       // The module path string ref set in the summary must be owned by the
       // index's module string table. Since we don't have a module path
       // string table section in the per-module index, we create a single
       // module path string table entry with an empty (0) ID to take
       // ownership.
       AS->setModulePath(
-          TheIndex->addModulePath(Buffer->getBufferIdentifier(), 0)->first());
+          TheIndex->addModulePath(Buffer.getBufferIdentifier(), 0)->first());
 
       GlobalValue::GUID AliaseeGUID = getGUIDFromValueId(AliaseeID).first;
       auto *AliaseeSummary = TheIndex->getGlobalValueSummary(AliaseeGUID);
       if (!AliaseeSummary)
         return error("Alias expects aliasee summary to be parsed");
       AS->setAliasee(AliaseeSummary);
 
       auto GUID = getGUIDFromValueId(ValueID);
       AS->setOriginalName(GUID.second);
       TheIndex->addGlobalValueSummary(GUID.first, std::move(AS));
       break;
     }
     // FS_PERMODULE_GLOBALVAR_INIT_REFS: [valueid, flags, n x valueid]
     case bitc::FS_PERMODULE_GLOBALVAR_INIT_REFS: {
       unsigned ValueID = Record[0];
       uint64_t RawFlags = Record[1];
       auto Flags = getDecodedGVSummaryFlags(RawFlags, Version);
       std::unique_ptr<GlobalVarSummary> FS =
           llvm::make_unique<GlobalVarSummary>(Flags);
       FS->setModulePath(
-          TheIndex->addModulePath(Buffer->getBufferIdentifier(), 0)->first());
+          TheIndex->addModulePath(Buffer.getBufferIdentifier(), 0)->first());
       for (unsigned I = 2, E = Record.size(); I != E; ++I) {
         unsigned RefValueId = Record[I];
         GlobalValue::GUID RefGUID = getGUIDFromValueId(RefValueId).first;
         FS->addRefEdge(RefGUID);
       }
       auto GUID = getGUIDFromValueId(ValueID);
       FS->setOriginalName(GUID.second);
       TheIndex->addGlobalValueSummary(GUID.first, std::move(FS));

 const std::error_category &llvm::BitcodeErrorCategory() {
   return *ErrorCategory;
 }
 
 //===----------------------------------------------------------------------===//
 // External interface
 //===----------------------------------------------------------------------===//
 
+/// \brief Get a lazy one-at-time loading module from bitcode.
+///
+/// This isn't always used in a lazy context.  In particular, it's also used by
+/// \a parseBitcodeFile().  If this is truly lazy, then we need to eagerly pull
+/// in forward-referenced functions from block address references.
+///
+/// \param[in] MaterializeAll Set to \c true if we should materialize
+/// everything.
 static ErrorOr<std::unique_ptr<Module>>
-getBitcodeModuleImpl(StringRef Name, BitcodeReader *R, LLVMContext &Context,
-                     bool MaterializeAll, bool ShouldLazyLoadMetadata) {
-  std::unique_ptr<Module> M = llvm::make_unique<Module>(Name, Context);
-  M->setMaterializer(R);
+getLazyBitcodeModuleImpl(MemoryBufferRef Buffer, LLVMContext &Context,
+                         bool MaterializeAll,
+                         bool ShouldLazyLoadMetadata = false) {
+  BitcodeReader *R = new BitcodeReader(Buffer, Context);
 
-  auto cleanupOnError = [&](std::error_code EC) {
-    R->releaseBuffer(); // Never take ownership on error.
-    return EC;
-  };
+  std::unique_ptr<Module> M =
+      llvm::make_unique<Module>(Buffer.getBufferIdentifier(), Context);
+  M->setMaterializer(R);
 
   // Delay parsing Metadata if ShouldLazyLoadMetadata is true.
   if (std::error_code EC = R->parseBitcodeInto(M.get(), ShouldLazyLoadMetadata))
-    return cleanupOnError(EC);
+    return EC;
 
   if (MaterializeAll) {
     // Read in the entire module, and destroy the BitcodeReader.
     if (std::error_code EC = M->materializeAll())
-      return cleanupOnError(EC);
+      return EC;
   } else {
     // Resolve forward references from blockaddresses.
     if (std::error_code EC = R->materializeForwardReferencedFunctions())
-      return cleanupOnError(EC);
+      return EC;
   }
   return std::move(M);
 }
 
-/// \brief Get a lazy one-at-time loading module from bitcode.
-///
-/// This isn't always used in a lazy context.  In particular, it's also used by
-/// \a parseBitcodeFile().  If this is truly lazy, then we need to eagerly pull
-/// in forward-referenced functions from block address references.
-///
-/// \param[in] MaterializeAll Set to \c true if we should materialize
-/// everything.
-static ErrorOr<std::unique_ptr<Module>>
-getLazyBitcodeModuleImpl(std::unique_ptr<MemoryBuffer> &&Buffer,
-                         LLVMContext &Context, bool MaterializeAll,
-                         bool ShouldLazyLoadMetadata = false) {
-  BitcodeReader *R = new BitcodeReader(Buffer.get(), Context);
-
-  ErrorOr<std::unique_ptr<Module>> Ret =
-      getBitcodeModuleImpl(Buffer->getBufferIdentifier(), R, Context,
-                           MaterializeAll, ShouldLazyLoadMetadata);
-  if (!Ret)
-    return Ret;
-
-  Buffer.release(); // The BitcodeReader owns it now.
-  return Ret;
-}
-
 ErrorOr<std::unique_ptr<Module>>
-llvm::getLazyBitcodeModule(std::unique_ptr<MemoryBuffer> &&Buffer,
+llvm::getLazyBitcodeModule(MemoryBufferRef Buffer,
                            LLVMContext &Context, bool ShouldLazyLoadMetadata) {
-  return getLazyBitcodeModuleImpl(std::move(Buffer), Context, false,
+  return getLazyBitcodeModuleImpl(Buffer, Context, false,
                                   ShouldLazyLoadMetadata);
 }
 
+ErrorOr<std::unique_ptr<Module>>
+llvm::getOwningLazyBitcodeModule(std::unique_ptr<MemoryBuffer> &&Buffer,
+                                 LLVMContext &Context,
+                                 bool ShouldLazyLoadMetadata) {
+  auto MOrErr = getLazyBitcodeModule(*Buffer, Context, ShouldLazyLoadMetadata);
+  if (MOrErr)
+    (*MOrErr)->takeMemoryBuffer(std::move(Buffer));
+  return MOrErr;
+}
+
 ErrorOr<std::unique_ptr<Module>> llvm::parseBitcodeFile(MemoryBufferRef Buffer,
                                                         LLVMContext &Context) {
-  std::unique_ptr<MemoryBuffer> Buf = MemoryBuffer::getMemBuffer(Buffer, false);
-  return getLazyBitcodeModuleImpl(std::move(Buf), Context, true);
+  return getLazyBitcodeModuleImpl(Buffer, Context, true);
   // TODO: Restore the use-lists to the in-memory state when the bitcode was
   // written.  We must defer until the Module has been fully materialized.
 }
 
 std::string llvm::getBitcodeTargetTriple(MemoryBufferRef Buffer,
                                          LLVMContext &Context) {
-  std::unique_ptr<MemoryBuffer> Buf = MemoryBuffer::getMemBuffer(Buffer, false);
-  auto R = llvm::make_unique<BitcodeReader>(Buf.release(), Context);
-  ErrorOr<std::string> Triple = R->parseTriple();
+  BitcodeReader R(Buffer, Context);
+  ErrorOr<std::string> Triple = R.parseTriple();
   if (Triple.getError())
     return "";
   return Triple.get();
 }
 
 bool llvm::isBitcodeContainingObjCCategory(MemoryBufferRef Buffer,
                                            LLVMContext &Context) {
-  std::unique_ptr<MemoryBuffer> Buf = MemoryBuffer::getMemBuffer(Buffer, false);
-  auto R = llvm::make_unique<BitcodeReader>(Buf.release(), Context);
-  ErrorOr<bool> hasObjCCategory = R->hasObjCCategory();
+  BitcodeReader R(Buffer, Context);
+  ErrorOr<bool> hasObjCCategory = R.hasObjCCategory();
   if (hasObjCCategory.getError())
     return false;
   return hasObjCCategory.get();
 }
 
 std::string llvm::getBitcodeProducerString(MemoryBufferRef Buffer,
                                            LLVMContext &Context) {
-  std::unique_ptr<MemoryBuffer> Buf = MemoryBuffer::getMemBuffer(Buffer, false);
-  BitcodeReader R(Buf.release(), Context);
+  BitcodeReader R(Buffer, Context);
   ErrorOr<std::string> ProducerString = R.parseIdentificationBlock();
   if (ProducerString.getError())
     return "";
   return ProducerString.get();
 }
 
 // Parse the specified bitcode buffer, returning the function info index.
 ErrorOr<std::unique_ptr<ModuleSummaryIndex>> llvm::getModuleSummaryIndex(
     MemoryBufferRef Buffer,
     const DiagnosticHandlerFunction &DiagnosticHandler) {
-  std::unique_ptr<MemoryBuffer> Buf = MemoryBuffer::getMemBuffer(Buffer, false);
-  ModuleSummaryIndexBitcodeReader R(Buf.get(), DiagnosticHandler);
+  ModuleSummaryIndexBitcodeReader R(Buffer, DiagnosticHandler);
 
   auto Index = llvm::make_unique<ModuleSummaryIndex>();
 
-  auto cleanupOnError = [&](std::error_code EC) {
-    R.releaseBuffer(); // Never take ownership on error.
-    return EC;
-  };
-
   if (std::error_code EC = R.parseSummaryIndexInto(Index.get()))
-    return cleanupOnError(EC);
+    return EC;
 
-  Buf.release(); // The ModuleSummaryIndexBitcodeReader owns it now.
   return std::move(Index);
 }
 
 // Check if the given bitcode buffer contains a global value summary block.
 bool llvm::hasGlobalValueSummary(
     MemoryBufferRef Buffer,
     const DiagnosticHandlerFunction &DiagnosticHandler) {
-  std::unique_ptr<MemoryBuffer> Buf = MemoryBuffer::getMemBuffer(Buffer, false);
-  ModuleSummaryIndexBitcodeReader R(Buf.get(), DiagnosticHandler, true);
+  ModuleSummaryIndexBitcodeReader R(Buffer, DiagnosticHandler, true);
 
-  auto cleanupOnError = [&](std::error_code EC) {
-    R.releaseBuffer(); // Never take ownership on error.
+  if (R.parseSummaryIndexInto(nullptr))
     return false;
-  };
-
-  if (std::error_code EC = R.parseSummaryIndexInto(nullptr))
-    return cleanupOnError(EC);
 
-  Buf.release(); // The ModuleSummaryIndexBitcodeReader owns it now.
   return R.foundGlobalValSummary();
 }

llvm/lib/IR/Module.cpp

 #include "llvm/IR/Constants.h"
 #include "llvm/IR/DerivedTypes.h"
 #include "llvm/IR/DebugInfoMetadata.h"
 #include "llvm/IR/GVMaterializer.h"
 #include "llvm/IR/InstrTypes.h"
 #include "llvm/IR/LLVMContext.h"
 #include "llvm/IR/TypeFinder.h"
 #include "llvm/Support/Dwarf.h"
+#include "llvm/Support/MemoryBuffer.h"
 #include "llvm/Support/Path.h"
 #include "llvm/Support/RandomNumberGenerator.h"
 #include <algorithm>
 #include <cstdarg>
 #include <cstdlib>
 
 using namespace llvm;
 

 void Module::setProfileSummary(Metadata *M) {
   addModuleFlag(ModFlagBehavior::Error, "ProfileSummary", M);
 }
 
 Metadata *Module::getProfileSummary() {
   return getModuleFlag("ProfileSummary");
 }
 
+void Module::takeMemoryBuffer(std::unique_ptr<MemoryBuffer> MB) {
+  OwnedMemoryBuffer = std::move(MB);
+}
+
 GlobalVariable *llvm::collectUsedGlobalVariables(
     const Module &M, SmallPtrSetImpl<GlobalValue *> &Set, bool CompilerUsed) {
   const char *Name = CompilerUsed ? "llvm.compiler.used" : "llvm.used";
   GlobalVariable *GV = M.getGlobalVariable(Name);
   if (!GV || !GV->hasInitializer())
     return GV;
 
   const ConstantArray *Init = cast<ConstantArray>(GV->getInitializer());
   for (Value *Op : Init->operands()) {
     GlobalValue *G = cast<GlobalValue>(Op->stripPointerCastsNoFollowAliases());
     Set.insert(G);
   }
   return GV;
 }

llvm/lib/IRReader/IRReader.cpp

 static const char *const TimeIRParsingGroupName = "LLVM IR Parsing";
 static const char *const TimeIRParsingName = "Parse IR";
 
 static std::unique_ptr<Module>
 getLazyIRModule(std::unique_ptr<MemoryBuffer> Buffer, SMDiagnostic &Err,
                 LLVMContext &Context, bool ShouldLazyLoadMetadata) {
   if (isBitcode((const unsigned char *)Buffer->getBufferStart(),
                 (const unsigned char *)Buffer->getBufferEnd())) {
-    ErrorOr<std::unique_ptr<Module>> ModuleOrErr = getLazyBitcodeModule(
+    ErrorOr<std::unique_ptr<Module>> ModuleOrErr = getOwningLazyBitcodeModule(
         std::move(Buffer), Context, ShouldLazyLoadMetadata);
     if (std::error_code EC = ModuleOrErr.getError()) {
       Err = SMDiagnostic(Buffer->getBufferIdentifier(), SourceMgr::DK_Error,
                          EC.message());
       return nullptr;
     }
     return std::move(ModuleOrErr.get());
   }

llvm/lib/LTO/LTO.cpp

 
 // Simple helper to load a module from bitcode
 std::unique_ptr<Module>
 llvm::loadModuleFromBuffer(const MemoryBufferRef &Buffer, LLVMContext &Context,
                            bool Lazy) {
   SMDiagnostic Err;
   ErrorOr<std::unique_ptr<Module>> ModuleOrErr(nullptr);
   if (Lazy) {
-    ModuleOrErr =
-        getLazyBitcodeModule(MemoryBuffer::getMemBuffer(Buffer, false), Context,
+    ModuleOrErr = getLazyBitcodeModule(Buffer, Context,
                                        /* ShouldLazyLoadMetadata */ Lazy);
   } else {
     ModuleOrErr = parseBitcodeFile(Buffer, Context);
   }
   if (std::error_code EC = ModuleOrErr.getError()) {
     Err = SMDiagnostic(Buffer.getBufferIdentifier(), SourceMgr::DK_Error,
                        EC.message());
     Err.print("ThinLTO", errs());
     report_fatal_error("Can't load module, abort.");

llvm/lib/LTO/LTOBackend.cpp

Error lto::thinBackend(Config &Conf, unsigned Task, AddStreamFn AddStream,
 
   if (Conf.PostInternalizeModuleHook &&
       !Conf.PostInternalizeModuleHook(Task, Mod))
     return Error();
 
   auto ModuleLoader = [&](StringRef Identifier) {
     assert(Mod.getContext().isODRUniquingDebugTypes() &&
            "ODR Type uniquing should be enabled on the context");
-    return std::move(getLazyBitcodeModule(MemoryBuffer::getMemBuffer(
-                                              ModuleMap[Identifier], false),
+    return std::move(getLazyBitcodeModule(ModuleMap[Identifier],
                                           Mod.getContext(),
                                           /*ShouldLazyLoadMetadata=*/true)
                          .get());
   };
 
   FunctionImporter Importer(CombinedIndex, ModuleLoader);
   Importer.importFunctions(Mod, ImportList);
 

llvm/lib/LTO/LTOModule.cpp

if (!ShouldBeLazy) {
     // Parse the full file.
     ErrorOr<std::unique_ptr<Module>> M = parseBitcodeFile(*MBOrErr, Context);
     if (std::error_code EC = M.getError())
       return EC;
     return std::move(*M);
   }
 
   // Parse lazily.
-  std::unique_ptr<MemoryBuffer> LightweightBuf =
-      MemoryBuffer::getMemBuffer(*MBOrErr, false);
-  ErrorOr<std::unique_ptr<Module>> M = getLazyBitcodeModule(
-      std::move(LightweightBuf), Context, true /*ShouldLazyLoadMetadata*/);
+  ErrorOr<std::unique_ptr<Module>> M =
+      getLazyBitcodeModule(*MBOrErr, Context, true /*ShouldLazyLoadMetadata*/);
   if (std::error_code EC = M.getError())
     return EC;
   return std::move(*M);
 }
 
 ErrorOr<std::unique_ptr<LTOModule>>
 LTOModule::makeLTOModule(MemoryBufferRef Buffer, const TargetOptions &options,
                          LLVMContext &Context, bool ShouldBeLazy) {

llvm/lib/Object/IRObjectFile.cpp

 
 ErrorOr<std::unique_ptr<IRObjectFile>>
 llvm::object::IRObjectFile::create(MemoryBufferRef Object,
                                    LLVMContext &Context) {
   ErrorOr<MemoryBufferRef> BCOrErr = findBitcodeInMemBuffer(Object);
   if (!BCOrErr)
     return BCOrErr.getError();
 
-  std::unique_ptr<MemoryBuffer> Buff =
-      MemoryBuffer::getMemBuffer(BCOrErr.get(), false);
-
   ErrorOr<std::unique_ptr<Module>> MOrErr =
-      getLazyBitcodeModule(std::move(Buff), Context,
+      getLazyBitcodeModule(*BCOrErr, Context,
                            /*ShouldLazyLoadMetadata*/ true);
   if (std::error_code EC = MOrErr.getError())
     return EC;
 
   std::unique_ptr<Module> &M = MOrErr.get();
   return llvm::make_unique<IRObjectFile>(BCOrErr.get(), std::move(M));
 }

llvm/tools/llvm-dis/llvm-dis.cpp

 }
 
 static Expected<std::unique_ptr<Module>> openInputFile(LLVMContext &Context) {
   ErrorOr<std::unique_ptr<MemoryBuffer>> MBOrErr =
       MemoryBuffer::getFileOrSTDIN(InputFilename);
   if (!MBOrErr)
     return errorCodeToError(MBOrErr.getError());
   ErrorOr<std::unique_ptr<Module>> MOrErr =
-      getLazyBitcodeModule(std::move(*MBOrErr), Context,
+      getOwningLazyBitcodeModule(std::move(*MBOrErr), Context,
                                  /*ShouldLazyLoadMetadata=*/true);
   if (!MOrErr)
     return errorCodeToError(MOrErr.getError());
   if (MaterializeMetadata)
     (*MOrErr)->materializeMetadata();
   else
     (*MOrErr)->materializeAll();
   return std::move(*MOrErr);
 }

llvm/unittests/Bitcode/BitReaderTest.cpp

static void writeModuleToBuffer(std::unique_ptr<Module> Mod,
   raw_svector_ostream OS(Buffer);
   WriteBitcodeToFile(Mod.get(), OS);
 }
 
 static std::unique_ptr<Module> getLazyModuleFromAssembly(LLVMContext &Context,
                                                          SmallString<1024> &Mem,
                                                          const char *Assembly) {
   writeModuleToBuffer(parseAssembly(Context, Assembly), Mem);
-  std::unique_ptr<MemoryBuffer> Buffer =
-      MemoryBuffer::getMemBuffer(Mem.str(), "test", false);
   ErrorOr<std::unique_ptr<Module>> ModuleOrErr =
-      getLazyBitcodeModule(std::move(Buffer), Context);
+      getLazyBitcodeModule(MemoryBufferRef(Mem.str(), "test"), Context);
   return std::move(ModuleOrErr.get());
 }
 
 // Tests that lazy evaluation can parse functions out of order.
 TEST(BitReaderTest, MaterializeFunctionsOutOfOrder) {
   SmallString<1024> Mem;
   LLVMContext Context;
   std::unique_ptr<Module> M = getLazyModuleFromAssembly(