Bitcode: Change the BitcodeReader to use llvm::Error internally.

[mehdi_amini]

llvm/trunk/lib/Bitcode/Reader/BitcodeReader.cpp

4362 ↗

(On Diff #77291)

Returning Error::success with a conversion to Expected seems to trigger an assertion.

[pcc]

llvm/trunk/lib/Bitcode/Reader/BitcodeReader.cpp

4362 ↗

(On Diff #77291)

It seems that what we want to do here is return "", since we didn't encounter any errors but did not find an identification.

llvm/lib/Bitcode/Reader/BitcodeReader.cpp

 #include "llvm/IR/TrackingMDRef.h"
 #include "llvm/IR/Type.h"
 #include "llvm/IR/ValueHandle.h"
 #include "llvm/Support/AtomicOrdering.h"
 #include "llvm/Support/Casting.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Compiler.h"
 #include "llvm/Support/Debug.h"
+#include "llvm/Support/Error.h"
 #include "llvm/Support/ErrorHandling.h"
-#include "llvm/Support/ErrorOr.h"
 #include "llvm/Support/ManagedStatic.h"
 #include "llvm/Support/MemoryBuffer.h"
 #include "llvm/Support/raw_ostream.h"
 #include <algorithm>
 #include <cassert>
 #include <cstddef>
 #include <cstdint>
 #include <deque>

 class BitcodeReaderBase {
 protected:
   BitcodeReaderBase(MemoryBufferRef Buffer) : Buffer(Buffer) {}
 
   MemoryBufferRef Buffer;
   BitstreamBlockInfo BlockInfo;
   BitstreamCursor Stream;
 
-  std::error_code initStream();
+  Error initStream();
   bool readBlockInfo();
-
-  virtual std::error_code error(const Twine &Message) = 0;
-  virtual ~BitcodeReaderBase() = default;
 };
 
-std::error_code BitcodeReaderBase::initStream() {
+static Error error(const Twine &Message) {
+  return make_error<StringError>(
+      Message, make_error_code(BitcodeError::CorruptedBitcode));
+}
+
+Error BitcodeReaderBase::initStream() {
   const unsigned char *BufPtr = (const unsigned char*)Buffer.getBufferStart();
   const unsigned char *BufEnd = BufPtr+Buffer.getBufferSize();
 
   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");
 
   Stream = BitstreamCursor(ArrayRef<uint8_t>(BufPtr, BufEnd));
   Stream.setBlockInfo(&BlockInfo);
 
-  return std::error_code();
+  return Error::success();
 }
 
 class BitcodeReader : public BitcodeReaderBase, public GVMaterializer {
   LLVMContext &Context;
   Module *TheModule = nullptr;
   // Next offset to start scanning for lazy parsing of function bodies.
   uint64_t NextUnreadBit = 0;
   // Last function offset found in the VST.
class BitcodeReader : public BitcodeReaderBase, public GVMaterializer {
 
   /// Functions that need to be matched with subprograms when upgrading old
   /// metadata.
   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(MemoryBufferRef Buffer, LLVMContext &Context);
 
-  std::error_code materializeForwardReferencedFunctions();
+  Error materializeForwardReferencedFunctions();
 
   std::error_code materialize(GlobalValue *GV) override;
+  Error materializeImpl(GlobalValue *GV);
   std::error_code materializeModule() override;
+  Error materializeModuleImpl();
   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);
+  Error parseBitcodeInto(Module *M, bool ShouldLazyLoadMetadata = false);
 
   /// \brief Cheap mechanism to just extract module triple
   /// \returns true if an error occurred.
-  ErrorOr<std::string> parseTriple();
+  Expected<std::string> parseTriple();
 
   /// Cheap mechanism to just extract the identification block out of bitcode.
-  ErrorOr<std::string> parseIdentificationBlock();
+  Expected<std::string> parseIdentificationBlock();
 
   /// Peak at the module content and return true if any ObjC category or class
   /// is found.
-  ErrorOr<bool> hasObjCCategory();
+  Expected<bool> hasObjCCategory();
 
   static uint64_t decodeSignRotatedValue(uint64_t V);
 
   /// Materialize any deferred Metadata block.
   std::error_code materializeMetadata() override;
+  Error materializeMetadataImpl();
 
   void setStripDebugInfo() override;
 
 private:
   /// Parse the "IDENTIFICATION_BLOCK_ID" block, populate the
   // ProducerIdentification data member, and do some basic enforcement on the
   // "epoch" encoded in the bitcode.
-  std::error_code parseBitcodeVersion();
+  Error parseBitcodeVersion();
 
   std::vector<StructType *> IdentifiedStructTypes;
   StructType *createIdentifiedStructType(LLVMContext &Context, StringRef Name);
   StructType *createIdentifiedStructType(LLVMContext &Context);
 
   Type *getTypeByID(unsigned ID);
 
   Value *getFnValueByID(unsigned ID, Type *Ty) {
Value *getValueSigned(SmallVectorImpl<uint64_t> &Record, unsigned Slot,
     if (UseRelativeIDs)
       ValNo = InstNum - ValNo;
     return getFnValueByID(ValNo, Ty);
   }
 
   /// Converts alignment exponent (i.e. power of two (or zero)) to the
   /// corresponding alignment to use. If alignment is too large, returns
   /// a corresponding error code.
-  std::error_code parseAlignmentValue(uint64_t Exponent, unsigned &Alignment);
-  std::error_code parseAttrKind(uint64_t Code, Attribute::AttrKind *Kind);
-  std::error_code parseModule(uint64_t ResumeBit,
-                              bool ShouldLazyLoadMetadata = false);
-  std::error_code parseAttributeBlock();
-  std::error_code parseAttributeGroupBlock();
-  std::error_code parseTypeTable();
-  std::error_code parseTypeTableBody();
-  std::error_code parseOperandBundleTags();
+  Error parseAlignmentValue(uint64_t Exponent, unsigned &Alignment);
+  Error parseAttrKind(uint64_t Code, Attribute::AttrKind *Kind);
+  Error parseModule(uint64_t ResumeBit, bool ShouldLazyLoadMetadata = false);
+  Error parseAttributeBlock();
+  Error parseAttributeGroupBlock();
+  Error parseTypeTable();
+  Error parseTypeTableBody();
+  Error parseOperandBundleTags();
 
-  ErrorOr<Value *> recordValue(SmallVectorImpl<uint64_t> &Record,
+  Expected<Value *> recordValue(SmallVectorImpl<uint64_t> &Record,
                                 unsigned NameIndex, Triple &TT);
-  std::error_code parseValueSymbolTable(uint64_t Offset = 0);
-  std::error_code parseConstants();
-  std::error_code rememberAndSkipFunctionBodies();
-  std::error_code rememberAndSkipFunctionBody();
+  Error parseValueSymbolTable(uint64_t Offset = 0);
+  Error parseConstants();
+  Error rememberAndSkipFunctionBodies();
+  Error rememberAndSkipFunctionBody();
   /// Save the positions of the Metadata blocks and skip parsing the blocks.
-  std::error_code rememberAndSkipMetadata();
-  std::error_code parseFunctionBody(Function *F);
-  std::error_code globalCleanup();
-  std::error_code resolveGlobalAndIndirectSymbolInits();
-  std::error_code parseMetadata(bool ModuleLevel = false);
-  std::error_code parseMetadataStrings(ArrayRef<uint64_t> Record,
-                                       StringRef Blob,
-                                       unsigned &NextMetadataNo);
-  std::error_code parseMetadataKinds();
-  std::error_code parseMetadataKindRecord(SmallVectorImpl<uint64_t> &Record);
-  std::error_code
-  parseGlobalObjectAttachment(GlobalObject &GO,
+  Error rememberAndSkipMetadata();
+  Error parseFunctionBody(Function *F);
+  Error globalCleanup();
+  Error resolveGlobalAndIndirectSymbolInits();
+  Error parseMetadata(bool ModuleLevel = false);
+  Error parseMetadataStrings(ArrayRef<uint64_t> Record, StringRef Blob,
+  Error parseMetadataKinds();
+  Error parseMetadataKindRecord(SmallVectorImpl<uint64_t> &Record);
+  Error parseGlobalObjectAttachment(GlobalObject &GO,
                                     ArrayRef<uint64_t> Record);
-  std::error_code parseMetadataAttachment(Function &F);
-  ErrorOr<std::string> parseModuleTriple();
-  ErrorOr<bool> hasObjCCategoryInModule();
-  std::error_code parseUseLists();
-  std::error_code findFunctionInStream(
+  Error parseMetadataAttachment(Function &F);
+  Expected<std::string> parseModuleTriple();
+  Expected<bool> hasObjCCategoryInModule();
+  Error parseUseLists();
+  Error findFunctionInStream(
       Function *F,
       DenseMap<Function *, uint64_t>::iterator DeferredFunctionInfoIterator);
 };
 
 /// Class to manage reading and parsing function summary index bitcode
 /// files/sections.
 class ModuleSummaryIndexBitcodeReader : public BitcodeReaderBase {
-  DiagnosticHandlerFunction DiagnosticHandler;
-
   /// Eventually points to the module index built during parsing.
   ModuleSummaryIndex *TheIndex = nullptr;
 
   /// Used to indicate whether caller only wants to check for the presence
   /// of the global value summary bitcode section. All blocks are skipped,
   /// but the SeenGlobalValSummary boolean is set.
   bool CheckGlobalValSummaryPresenceOnly = false;
 
class ModuleSummaryIndexBitcodeReader : public BitcodeReaderBase {
   /// path string table, used to correlate with combined index
   /// summary records.
   DenseMap<uint64_t, StringRef> ModuleIdMap;
 
   /// Original source file name recorded in a bitcode record.
   std::string SourceFileName;
 
 public:
-  std::error_code error(const Twine &Message);
-
   ModuleSummaryIndexBitcodeReader(
-      MemoryBufferRef Buffer, DiagnosticHandlerFunction DiagnosticHandler,
-      bool CheckGlobalValSummaryPresenceOnly = false);
+      MemoryBufferRef Buffer, bool CheckGlobalValSummaryPresenceOnly = false);
 
   /// 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);
+  Error parseSummaryIndexInto(ModuleSummaryIndex *I);
 
 private:
-  std::error_code parseModule();
-  std::error_code parseValueSymbolTable(
+  Error parseModule();
+  Error parseValueSymbolTable(
       uint64_t Offset,
       DenseMap<unsigned, GlobalValue::LinkageTypes> &ValueIdToLinkageMap);
-  std::error_code parseEntireSummary();
-  std::error_code parseModuleStringTable();
+  Error parseEntireSummary();
+  Error parseModuleStringTable();
   std::pair<GlobalValue::GUID, GlobalValue::GUID>
 
   getGUIDFromValueId(unsigned ValueId);
   std::pair<GlobalValue::GUID, CalleeInfo::HotnessType>
   readCallGraphEdge(const SmallVector<uint64_t, 64> &Record, unsigned int &I,
                     bool IsOldProfileFormat, bool HasProfile);
 };
 
-} // end anonymous namespace
-
-BitcodeDiagnosticInfo::BitcodeDiagnosticInfo(std::error_code EC,
-                                             DiagnosticSeverity Severity,
-                                             const Twine &Msg)
-    : DiagnosticInfo(DK_Bitcode, Severity), Msg(Msg), EC(EC) {}
-
-void BitcodeDiagnosticInfo::print(DiagnosticPrinter &DP) const { DP << Msg; }
-
-static std::error_code error(const DiagnosticHandlerFunction &DiagnosticHandler,
-                             std::error_code EC, const Twine &Message) {
-  BitcodeDiagnosticInfo DI(EC, DS_Error, Message);
-  DiagnosticHandler(DI);
+std::error_code errorToErrorCodeAndEmitErrors(LLVMContext &Ctx, Error Err) {
+  if (Err) {
+    std::error_code EC;
+    handleAllErrors(std::move(Err), [&](ErrorInfoBase &EIB) {
+      EC = EIB.convertToErrorCode();
+      Ctx.emitError(EIB.message());
+    });
     return EC;
   }
-
-static std::error_code error(LLVMContext &Context, std::error_code EC,
-                             const Twine &Message) {
-  return error([&](const DiagnosticInfo &DI) { Context.diagnose(DI); }, EC,
-               Message);
-}
-
-static std::error_code error(LLVMContext &Context, const Twine &Message) {
-  return error(Context, make_error_code(BitcodeError::CorruptedBitcode),
-               Message);
+  return std::error_code();
 }
 
-std::error_code BitcodeReader::error(BitcodeError E, const Twine &Message) {
-  if (!ProducerIdentification.empty()) {
-    return ::error(Context, make_error_code(E),
-                   Message + " (Producer: '" + ProducerIdentification +
-                       "' Reader: 'LLVM " + LLVM_VERSION_STRING "')");
+std::error_code
+errorToErrorCodeAndEmitErrors(const DiagnosticHandlerFunction &DiagHandler,
+                              Error Err) {
+  if (Err) {
+    std::error_code EC;
+    handleAllErrors(std::move(Err), [&](ErrorInfoBase &EIB) {
+      EC = EIB.convertToErrorCode();
+      DiagHandler(DiagnosticInfoInlineAsm(EIB.message()));
+    });
+    return EC;
   }
-  return ::error(Context, make_error_code(E), Message);
+  return std::error_code();
 }
 
-std::error_code BitcodeReader::error(const Twine &Message) {
-  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);
+template <typename T>
+ErrorOr<T> expectedToErrorOrAndEmitErrors(LLVMContext &Ctx, Expected<T> Val) {
+  if (!Val)
+    return errorToErrorCodeAndEmitErrors(Ctx, Val.takeError());
+  return std::move(*Val);
+
+template <typename T>
+static ErrorOr<T>
+expectedToErrorOrAndEmitErrors(const DiagnosticHandlerFunction &DiagHandler,
+                               Expected<T> Val) {
+  if (!Val)
+    return errorToErrorCodeAndEmitErrors(DiagHandler, Val.takeError());
+  return std::move(*Val);
 }
 
+} // end anonymous namespace
+
 BitcodeReader::BitcodeReader(MemoryBufferRef Buffer, LLVMContext &Context)
     : BitcodeReaderBase(Buffer), Context(Context), ValueList(Context),
       MetadataList(Context) {}
 
-std::error_code BitcodeReader::materializeForwardReferencedFunctions() {
+Error BitcodeReader::materializeForwardReferencedFunctions() {
   if (WillMaterializeAllForwardRefs)
-    return std::error_code();
+    return Error::success();
 
   // Prevent recursion.
   WillMaterializeAllForwardRefs = true;
 
   while (!BasicBlockFwdRefQueue.empty()) {
     Function *F = BasicBlockFwdRefQueue.front();
     BasicBlockFwdRefQueue.pop_front();
     assert(F && "Expected valid function");
     if (!BasicBlockFwdRefs.count(F))
       // Already materialized.
       continue;
 
     // Check for a function that isn't materializable to prevent an infinite
     // loop.  When parsing a blockaddress stored in a global variable, there
     // isn't a trivial way to check if a function will have a body without a
     // linear search through FunctionsWithBodies, so just check it here.
     if (!F->isMaterializable())
       return error("Never resolved function from blockaddress");
 
     // Try to materialize F.
-    if (std::error_code EC = materialize(F))
-      return EC;
+    if (Error Err = materializeImpl(F))
+      return Err;
   }
   assert(BasicBlockFwdRefs.empty() && "Function missing from queue");
 
   // Reset state.
   WillMaterializeAllForwardRefs = false;
-  return std::error_code();
+  return Error::success();
 }
 
 //===----------------------------------------------------------------------===//
 //  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>
assert((!Alignment || isPowerOf2_32(Alignment)) &&
          "Alignment must be a power of two.");
 
   if (Alignment)
     B.addAlignmentAttr(Alignment);
   addRawAttributeValue(B, ((EncodedAttrs & (0xfffffULL << 32)) >> 11) |
                           (EncodedAttrs & 0xffff));
 }
 
-std::error_code BitcodeReader::parseAttributeBlock() {
+Error BitcodeReader::parseAttributeBlock() {
   if (Stream.EnterSubBlock(bitc::PARAMATTR_BLOCK_ID))
     return error("Invalid record");
 
   if (!MAttributes.empty())
     return error("Invalid multiple blocks");
 
   SmallVector<uint64_t, 64> Record;
 
   SmallVector<AttributeSet, 8> Attrs;
 
   // Read all the records.
   while (true) {
     BitstreamEntry Entry = Stream.advanceSkippingSubblocks();
 
     switch (Entry.Kind) {
     case BitstreamEntry::SubBlock: // Handled for us already.
     case BitstreamEntry::Error:
       return error("Malformed block");
     case BitstreamEntry::EndBlock:
-      return std::error_code();
+      return Error::success();
     case BitstreamEntry::Record:
       // The interesting case.
       break;
     }
 
     // Read a record.
     Record.clear();
     switch (Stream.readRecord(Entry.ID, Record)) {
case bitc::ATTR_KIND_UW_TABLE:
     return Attribute::UWTable;
   case bitc::ATTR_KIND_WRITEONLY:
     return Attribute::WriteOnly;
   case bitc::ATTR_KIND_Z_EXT:
     return Attribute::ZExt;
   }
 }
 
-std::error_code BitcodeReader::parseAlignmentValue(uint64_t Exponent,
-                                                   unsigned &Alignment) {
+Error BitcodeReader::parseAlignmentValue(uint64_t Exponent,
   // Note: Alignment in bitcode files is incremented by 1, so that zero
   // can be used for default alignment.
   if (Exponent > Value::MaxAlignmentExponent + 1)
     return error("Invalid alignment value");
   Alignment = (1 << static_cast<unsigned>(Exponent)) >> 1;
-  return std::error_code();
+  return Error::success();
 }
 
-std::error_code BitcodeReader::parseAttrKind(uint64_t Code,
-                                             Attribute::AttrKind *Kind) {
+Error BitcodeReader::parseAttrKind(uint64_t Code, Attribute::AttrKind *Kind) {
   *Kind = getAttrFromCode(Code);
   if (*Kind == Attribute::None)
-    return error(BitcodeError::CorruptedBitcode,
-                 "Unknown attribute kind (" + Twine(Code) + ")");
-  return std::error_code();
+    return error("Unknown attribute kind (" + Twine(Code) + ")");
+  return Error::success();
 }
 
-std::error_code BitcodeReader::parseAttributeGroupBlock() {
+Error BitcodeReader::parseAttributeGroupBlock() {
   if (Stream.EnterSubBlock(bitc::PARAMATTR_GROUP_BLOCK_ID))
     return error("Invalid record");
 
   if (!MAttributeGroups.empty())
     return error("Invalid multiple blocks");
 
   SmallVector<uint64_t, 64> Record;
 
   // Read all the records.
   while (true) {
     BitstreamEntry Entry = Stream.advanceSkippingSubblocks();
 
     switch (Entry.Kind) {
     case BitstreamEntry::SubBlock: // Handled for us already.
     case BitstreamEntry::Error:
       return error("Malformed block");
     case BitstreamEntry::EndBlock:
-      return std::error_code();
+      return Error::success();
     case BitstreamEntry::Record:
       // The interesting case.
       break;
     }
 
     // Read a record.
     Record.clear();
     switch (Stream.readRecord(Entry.ID, Record)) {
     default:  // Default behavior: ignore.
       break;
     case bitc::PARAMATTR_GRP_CODE_ENTRY: { // ENTRY: [grpid, idx, a0, a1, ...]
       if (Record.size() < 3)
         return error("Invalid record");
 
       uint64_t GrpID = Record[0];
       uint64_t Idx = Record[1]; // Index of the object this attribute refers to.
 
       AttrBuilder B;
       for (unsigned i = 2, e = Record.size(); i != e; ++i) {
         if (Record[i] == 0) {        // Enum attribute
           Attribute::AttrKind Kind;
-          if (std::error_code EC = parseAttrKind(Record[++i], &Kind))
-            return EC;
+          if (Error Err = parseAttrKind(Record[++i], &Kind))
+            return Err;
 
           B.addAttribute(Kind);
         } else if (Record[i] == 1) { // Integer attribute
           Attribute::AttrKind Kind;
-          if (std::error_code EC = parseAttrKind(Record[++i], &Kind))
-            return EC;
+          if (Error Err = parseAttrKind(Record[++i], &Kind))
+            return Err;
           if (Kind == Attribute::Alignment)
             B.addAlignmentAttr(Record[++i]);
           else if (Kind == Attribute::StackAlignment)
             B.addStackAlignmentAttr(Record[++i]);
           else if (Kind == Attribute::Dereferenceable)
             B.addDereferenceableAttr(Record[++i]);
           else if (Kind == Attribute::DereferenceableOrNull)
             B.addDereferenceableOrNullAttr(Record[++i]);
case bitc::PARAMATTR_GRP_CODE_ENTRY: { // ENTRY: [grpid, idx, a0, a1, ...]
 
       MAttributeGroups[GrpID] = AttributeSet::get(Context, Idx, B);
       break;
     }
     }
   }
 }
 
-std::error_code BitcodeReader::parseTypeTable() {
+Error BitcodeReader::parseTypeTable() {
   if (Stream.EnterSubBlock(bitc::TYPE_BLOCK_ID_NEW))
     return error("Invalid record");
 
   return parseTypeTableBody();
 }
 
-std::error_code BitcodeReader::parseTypeTableBody() {
+Error BitcodeReader::parseTypeTableBody() {
   if (!TypeList.empty())
     return error("Invalid multiple blocks");
 
   SmallVector<uint64_t, 64> Record;
   unsigned NumRecords = 0;
 
   SmallString<64> TypeName;
 
   // Read all the records for this type table.
   while (true) {
     BitstreamEntry Entry = Stream.advanceSkippingSubblocks();
 
     switch (Entry.Kind) {
     case BitstreamEntry::SubBlock: // Handled for us already.
     case BitstreamEntry::Error:
       return error("Malformed block");
     case BitstreamEntry::EndBlock:
       if (NumRecords != TypeList.size())
         return error("Malformed block");
-      return std::error_code();
+      return Error::success();
     case BitstreamEntry::Record:
       // The interesting case.
       break;
     }
 
     // Read a record.
     Record.clear();
     Type *ResultTy = nullptr;
while (true) {
     if (TypeList[NumRecords])
       return error(
           "Invalid TYPE table: Only named structs can be forward referenced");
     assert(ResultTy && "Didn't read a type?");
     TypeList[NumRecords++] = ResultTy;
   }
 }
 
-std::error_code BitcodeReader::parseOperandBundleTags() {
+Error BitcodeReader::parseOperandBundleTags() {
   if (Stream.EnterSubBlock(bitc::OPERAND_BUNDLE_TAGS_BLOCK_ID))
     return error("Invalid record");
 
   if (!BundleTags.empty())
     return error("Invalid multiple blocks");
 
   SmallVector<uint64_t, 64> Record;
 
   while (true) {
     BitstreamEntry Entry = Stream.advanceSkippingSubblocks();
 
     switch (Entry.Kind) {
     case BitstreamEntry::SubBlock: // Handled for us already.
     case BitstreamEntry::Error:
       return error("Malformed block");
     case BitstreamEntry::EndBlock:
-      return std::error_code();
+      return Error::success();
     case BitstreamEntry::Record:
       // The interesting case.
       break;
     }
 
     // Tags are implicitly mapped to integers by their order.
 
     if (Stream.readRecord(Entry.ID, Record) != bitc::OPERAND_BUNDLE_TAG)
       return error("Invalid record");
 
     // OPERAND_BUNDLE_TAG: [strchr x N]
     BundleTags.emplace_back();
     if (convertToString(Record, 0, BundleTags.back()))
       return error("Invalid record");
     Record.clear();
   }
 }
 
 /// Associate a value with its name from the given index in the provided record.
-ErrorOr<Value *> BitcodeReader::recordValue(SmallVectorImpl<uint64_t> &Record,
+Expected<Value *> BitcodeReader::recordValue(SmallVectorImpl<uint64_t> &Record,
                                              unsigned NameIndex, Triple &TT) {
   SmallString<128> ValueName;
   if (convertToString(Record, NameIndex, ValueName))
     return error("Invalid record");
   unsigned ValueID = Record[0];
   if (ValueID >= ValueList.size() || !ValueList[ValueID])
     return error("Invalid record");
   Value *V = ValueList[ValueID];
 
#else
   // warning.
   Stream.advance();
 #endif
   return CurrentBit;
 }
 
 /// Parse the value symbol table at either the current parsing location or
 /// at the given bit offset if provided.
-std::error_code BitcodeReader::parseValueSymbolTable(uint64_t Offset) {
+Error BitcodeReader::parseValueSymbolTable(uint64_t Offset) {
   uint64_t CurrentBit;
   // Pass in the Offset to distinguish between calling for the module-level
   // VST (where we want to jump to the VST offset) and the function-level
   // VST (where we don't).
   if (Offset > 0)
     CurrentBit = jumpToValueSymbolTable(Offset, Stream);
 
   // Compute the delta between the bitcode indices in the VST (the word offset
while (true) {
 
     switch (Entry.Kind) {
     case BitstreamEntry::SubBlock: // Handled for us already.
     case BitstreamEntry::Error:
       return error("Malformed block");
     case BitstreamEntry::EndBlock:
       if (Offset > 0)
         Stream.JumpToBit(CurrentBit);
-      return std::error_code();
+      return Error::success();
     case BitstreamEntry::Record:
       // The interesting case.
       break;
     }
 
     // Read a record.
     Record.clear();
     switch (Stream.readRecord(Entry.ID, Record)) {
     default:  // Default behavior: unknown type.
       break;
     case bitc::VST_CODE_ENTRY: {  // VST_CODE_ENTRY: [valueid, namechar x N]
-      ErrorOr<Value *> ValOrErr = recordValue(Record, 1, TT);
-      if (std::error_code EC = ValOrErr.getError())
-        return EC;
+      Expected<Value *> ValOrErr = recordValue(Record, 1, TT);
+      if (Error Err = ValOrErr.takeError())
+        return Err;
       ValOrErr.get();
       break;
     }
     case bitc::VST_CODE_FNENTRY: {
       // VST_CODE_FNENTRY: [valueid, offset, namechar x N]
-      ErrorOr<Value *> ValOrErr = recordValue(Record, 2, TT);
-      if (std::error_code EC = ValOrErr.getError())
-        return EC;
+      Expected<Value *> ValOrErr = recordValue(Record, 2, TT);
+      if (Error Err = ValOrErr.takeError())
+        return Err;
       Value *V = ValOrErr.get();
 
       auto *GO = dyn_cast<GlobalObject>(V);
       if (!GO) {
         // If this is an alias, need to get the actual Function object
         // it aliases, in order to set up the DeferredFunctionInfo entry below.
         auto *GA = dyn_cast<GlobalAlias>(V);
         if (GA)
case bitc::VST_CODE_BBENTRY: {
       ValueName.clear();
       break;
     }
     }
   }
 }
 
 /// Parse a single METADATA_KIND record, inserting result in MDKindMap.
-std::error_code
-BitcodeReader::parseMetadataKindRecord(SmallVectorImpl<uint64_t> &Record) {
+Error BitcodeReader::parseMetadataKindRecord(
+    SmallVectorImpl<uint64_t> &Record) {
   if (Record.size() < 2)
     return error("Invalid record");
 
   unsigned Kind = Record[0];
   SmallString<8> Name(Record.begin() + 1, Record.end());
 
   unsigned NewKind = TheModule->getMDKindID(Name.str());
   if (!MDKindMap.insert(std::make_pair(Kind, NewKind)).second)
     return error("Conflicting METADATA_KIND records");
-  return std::error_code();
+  return Error::success();
 }
 
 static int64_t unrotateSign(uint64_t U) { return U & 1 ? ~(U >> 1) : U >> 1; }
 
-std::error_code BitcodeReader::parseMetadataStrings(ArrayRef<uint64_t> Record,
-                                                    StringRef Blob,
-                                                    unsigned &NextMetadataNo) {
+Error BitcodeReader::parseMetadataStrings(ArrayRef<uint64_t> Record,
   // All the MDStrings in the block are emitted together in a single
   // record.  The strings are concatenated and stored in a blob along with
   // their sizes.
   if (Record.size() != 2)
     return error("Invalid record: metadata strings layout");
 
   unsigned NumStrings = Record[0];
   unsigned StringsOffset = Record[1];
do {
     if (Strings.size() < Size)
       return error("Invalid record: metadata strings truncated chars");
 
     MetadataList.assignValue(MDString::get(Context, Strings.slice(0, Size)),
                              NextMetadataNo++);
     Strings = Strings.drop_front(Size);
   } while (--NumStrings);
 
-  return std::error_code();
+  return Error::success();
 }
 
 namespace {
 
 class PlaceholderQueue {
   // Placeholders would thrash around when moved, so store in a std::deque
   // instead of some sort of vector.
   std::deque<DistinctMDOperandPlaceholder> PHs;
while (!PHs.empty()) {
     PHs.front().replaceUseWith(
         MetadataList.getMetadataFwdRef(PHs.front().getID()));
     PHs.pop_front();
   }
 }
 
 /// Parse a METADATA_BLOCK. If ModuleLevel is true then we are parsing
 /// module level metadata.
-std::error_code BitcodeReader::parseMetadata(bool ModuleLevel) {
+Error BitcodeReader::parseMetadata(bool ModuleLevel) {
   assert((ModuleLevel || DeferredMetadataInfo.empty()) &&
          "Must read all module-level metadata before function-level");
 
   IsMetadataMaterialized = true;
   unsigned NextMetadataNo = MetadataList.size();
 
   if (!ModuleLevel && MetadataList.hasFwdRefs())
     return error("Invalid metadata: fwd refs into function blocks");
case BitstreamEntry::EndBlock:
       for (auto CU_SP : CUSubprograms)
         if (auto *SPs = dyn_cast_or_null<MDTuple>(CU_SP.second))
           for (auto &Op : SPs->operands())
             if (auto *SP = dyn_cast_or_null<MDNode>(Op))
               SP->replaceOperandWith(7, CU_SP.first);
 
       MetadataList.tryToResolveCycles();
       Placeholders.flush(MetadataList);
-      return std::error_code();
+      return Error::success();
     case BitstreamEntry::Record:
       // The interesting case.
       break;
     }
 
     // Read a record.
     Record.clear();
     StringRef Blob;
case bitc::METADATA_STRING_OLD: {
       // Test for upgrading !llvm.loop.
       HasSeenOldLoopTags |= mayBeOldLoopAttachmentTag(String);
 
       Metadata *MD = MDString::get(Context, String);
       MetadataList.assignValue(MD, NextMetadataNo++);
       break;
     }
     case bitc::METADATA_STRINGS:
-      if (std::error_code EC =
-              parseMetadataStrings(Record, Blob, NextMetadataNo))
-        return EC;
+      if (Error Err = parseMetadataStrings(Record, Blob, NextMetadataNo))
+        return Err;
       break;
     case bitc::METADATA_GLOBAL_DECL_ATTACHMENT: {
       if (Record.size() % 2 == 0)
         return error("Invalid record");
       unsigned ValueID = Record[0];
       if (ValueID >= ValueList.size())
         return error("Invalid record");
       if (auto *GO = dyn_cast<GlobalObject>(ValueList[ValueID]))
-        parseGlobalObjectAttachment(*GO, ArrayRef<uint64_t>(Record).slice(1));
+        if (Error Err = parseGlobalObjectAttachment(
+                *GO, ArrayRef<uint64_t>(Record).slice(1)))
+          return Err;
       break;
     }
     case bitc::METADATA_KIND: {
       // Support older bitcode files that had METADATA_KIND records in a
       // block with METADATA_BLOCK_ID.
-      if (std::error_code EC = parseMetadataKindRecord(Record))
-        return EC;
+      if (Error Err = parseMetadataKindRecord(Record))
+        return Err;
       break;
     }
     }
   }
 
 #undef GET_OR_DISTINCT
 }
 
 /// Parse the metadata kinds out of the METADATA_KIND_BLOCK.
-std::error_code BitcodeReader::parseMetadataKinds() {
+Error BitcodeReader::parseMetadataKinds() {
   if (Stream.EnterSubBlock(bitc::METADATA_KIND_BLOCK_ID))
     return error("Invalid record");
 
   SmallVector<uint64_t, 64> Record;
 
   // Read all the records.
   while (true) {
     BitstreamEntry Entry = Stream.advanceSkippingSubblocks();
 
     switch (Entry.Kind) {
     case BitstreamEntry::SubBlock: // Handled for us already.
     case BitstreamEntry::Error:
       return error("Malformed block");
     case BitstreamEntry::EndBlock:
-      return std::error_code();
+      return Error::success();
     case BitstreamEntry::Record:
       // The interesting case.
       break;
     }
 
     // Read a record.
     Record.clear();
     unsigned Code = Stream.readRecord(Entry.ID, Record);
     switch (Code) {
     default: // Default behavior: ignore.
       break;
     case bitc::METADATA_KIND: {
-      if (std::error_code EC = parseMetadataKindRecord(Record))
-        return EC;
+      if (Error Err = parseMetadataKindRecord(Record))
+        return Err;
       break;
     }
     }
   }
 }
 
 /// Decode a signed value stored with the sign bit in the LSB for dense VBR
 /// encoding.
 uint64_t BitcodeReader::decodeSignRotatedValue(uint64_t V) {
   if ((V & 1) == 0)
     return V >> 1;
   if (V != 1)
     return -(V >> 1);
   // There is no such thing as -0 with integers.  "-0" really means MININT.
   return 1ULL << 63;
 }
 
 /// Resolve all of the initializers for global values and aliases that we can.
-std::error_code BitcodeReader::resolveGlobalAndIndirectSymbolInits() {
+Error BitcodeReader::resolveGlobalAndIndirectSymbolInits() {
   std::vector<std::pair<GlobalVariable*, unsigned> > GlobalInitWorklist;
   std::vector<std::pair<GlobalIndirectSymbol*, unsigned> >
       IndirectSymbolInitWorklist;
   std::vector<std::pair<Function*, unsigned> > FunctionPrefixWorklist;
   std::vector<std::pair<Function*, unsigned> > FunctionPrologueWorklist;
   std::vector<std::pair<Function*, unsigned> > FunctionPersonalityFnWorklist;
 
   GlobalInitWorklist.swap(GlobalInits);
if (ValID >= ValueList.size()) {
       if (Constant *C = dyn_cast_or_null<Constant>(ValueList[ValID]))
         FunctionPersonalityFnWorklist.back().first->setPersonalityFn(C);
       else
         return error("Expected a constant");
     }
     FunctionPersonalityFnWorklist.pop_back();
   }
 
-  return std::error_code();
+  return Error::success();
 }
 
 static APInt readWideAPInt(ArrayRef<uint64_t> Vals, unsigned TypeBits) {
   SmallVector<uint64_t, 8> Words(Vals.size());
   transform(Vals, Words.begin(),
                  BitcodeReader::decodeSignRotatedValue);
 
   return APInt(TypeBits, Words);
 }
 
-std::error_code BitcodeReader::parseConstants() {
+Error BitcodeReader::parseConstants() {
   if (Stream.EnterSubBlock(bitc::CONSTANTS_BLOCK_ID))
     return error("Invalid record");
 
   SmallVector<uint64_t, 64> Record;
 
   // Read all the records for this value table.
   Type *CurTy = Type::getInt32Ty(Context);
   unsigned NextCstNo = ValueList.size();
 
   while (true) {
     BitstreamEntry Entry = Stream.advanceSkippingSubblocks();
 
     switch (Entry.Kind) {
     case BitstreamEntry::SubBlock: // Handled for us already.
     case BitstreamEntry::Error:
       return error("Malformed block");
     case BitstreamEntry::EndBlock:
       if (NextCstNo != ValueList.size())
         return error("Invalid constant reference");
 
       // Once all the constants have been read, go through and resolve forward
       // references.
       ValueList.resolveConstantForwardRefs();
-      return std::error_code();
+      return Error::success();
     case BitstreamEntry::Record:
       // The interesting case.
       break;
     }
 
     // Read a record.
     Record.clear();
     Type *VoidType = Type::getVoidTy(Context);
while (true) {
     }
     }
 
     ValueList.assignValue(V, NextCstNo);
     ++NextCstNo;
   }
 }
 
-std::error_code BitcodeReader::parseUseLists() {
+Error BitcodeReader::parseUseLists() {
   if (Stream.EnterSubBlock(bitc::USELIST_BLOCK_ID))
     return error("Invalid record");
 
   // Read all the records.
   SmallVector<uint64_t, 64> Record;
 
   while (true) {
     BitstreamEntry Entry = Stream.advanceSkippingSubblocks();
 
     switch (Entry.Kind) {
     case BitstreamEntry::SubBlock: // Handled for us already.
     case BitstreamEntry::Error:
       return error("Malformed block");
     case BitstreamEntry::EndBlock:
-      return std::error_code();
+      return Error::success();
     case BitstreamEntry::Record:
       // The interesting case.
       break;
     }
 
     // Read a use list record.
     Record.clear();
     bool IsBB = false;
case bitc::USELIST_CODE_DEFAULT: {
       break;
     }
     }
   }
 }
 
 /// When we see the block for metadata, remember where it is and then skip it.
 /// This lets us lazily deserialize the metadata.
-std::error_code BitcodeReader::rememberAndSkipMetadata() {
+Error BitcodeReader::rememberAndSkipMetadata() {
   // Save the current stream state.
   uint64_t CurBit = Stream.GetCurrentBitNo();
   DeferredMetadataInfo.push_back(CurBit);
 
   // Skip over the block for now.
   if (Stream.SkipBlock())
     return error("Invalid record");
-  return std::error_code();
+  return Error::success();
 }
 
 std::error_code BitcodeReader::materializeMetadata() {
+  return errorToErrorCodeAndEmitErrors(Context, materializeMetadataImpl());
+}
+
+Error BitcodeReader::materializeMetadataImpl() {
   for (uint64_t BitPos : DeferredMetadataInfo) {
     // Move the bit stream to the saved position.
     Stream.JumpToBit(BitPos);
-    if (std::error_code EC = parseMetadata(true))
-      return EC;
+    if (Error Err = parseMetadata(true))
+      return Err;
   }
   DeferredMetadataInfo.clear();
-  return std::error_code();
+  return Error::success();
 }
 
 void BitcodeReader::setStripDebugInfo() { StripDebugInfo = true; }
 
 /// When we see the block for a function body, remember where it is and then
 /// skip it.  This lets us lazily deserialize the functions.
-std::error_code BitcodeReader::rememberAndSkipFunctionBody() {
+Error BitcodeReader::rememberAndSkipFunctionBody() {
   // Get the function we are talking about.
   if (FunctionsWithBodies.empty())
     return error("Insufficient function protos");
 
   Function *Fn = FunctionsWithBodies.back();
   FunctionsWithBodies.pop_back();
 
   // Save the current stream state.
   uint64_t CurBit = Stream.GetCurrentBitNo();
   assert(
       (DeferredFunctionInfo[Fn] == 0 || DeferredFunctionInfo[Fn] == CurBit) &&
       "Mismatch between VST and scanned function offsets");
   DeferredFunctionInfo[Fn] = CurBit;
 
   // Skip over the function block for now.
   if (Stream.SkipBlock())
     return error("Invalid record");
-  return std::error_code();
+  return Error::success();
 }
 
-std::error_code BitcodeReader::globalCleanup() {
+Error BitcodeReader::globalCleanup() {
   // Patch the initializers for globals and aliases up.
-  resolveGlobalAndIndirectSymbolInits();
+  if (Error Err = resolveGlobalAndIndirectSymbolInits())
+    return Err;
   if (!GlobalInits.empty() || !IndirectSymbolInits.empty())
     return error("Malformed global initializer set");
 
   // Look for intrinsic functions which need to be upgraded at some point
   for (Function &F : *TheModule) {
     Function *NewFn;
     if (UpgradeIntrinsicFunction(&F, NewFn))
       UpgradedIntrinsics[&F] = NewFn;
     else if (auto Remangled = Intrinsic::remangleIntrinsicFunction(&F))
       // Some types could be renamed during loading if several modules are
       // loaded in the same LLVMContext (LTO scenario). In this case we should
       // remangle intrinsics names as well.
       RemangledIntrinsics[&F] = Remangled.getValue();
   }
 
   // Look for global variables which need to be renamed.
   for (GlobalVariable &GV : TheModule->globals())
     UpgradeGlobalVariable(&GV);
 
   // Force deallocation of memory for these vectors to favor the client that
   // want lazy deserialization.
   std::vector<std::pair<GlobalVariable*, unsigned> >().swap(GlobalInits);
   std::vector<std::pair<GlobalIndirectSymbol*, unsigned> >().swap(
       IndirectSymbolInits);
-  return std::error_code();
+  return Error::success();
 }
 
 /// Support for lazy parsing of function bodies. This is required if we
 /// either have an old bitcode file without a VST forward declaration record,
 /// or if we have an anonymous function being materialized, since anonymous
 /// functions do not have a name and are therefore not in the VST.
-std::error_code BitcodeReader::rememberAndSkipFunctionBodies() {
+Error BitcodeReader::rememberAndSkipFunctionBodies() {
   Stream.JumpToBit(NextUnreadBit);
 
   if (Stream.AtEndOfStream())
     return error("Could not find function in stream");
 
   if (!SeenFirstFunctionBody)
     return error("Trying to materialize functions before seeing function blocks");
 
   // An old bitcode file with the symbol table at the end would have
   // finished the parse greedily.
   assert(SeenValueSymbolTable);
 
   SmallVector<uint64_t, 64> Record;
 
   while (true) {
     BitstreamEntry Entry = Stream.advance();
     switch (Entry.Kind) {
     default:
       return error("Expect SubBlock");
     case BitstreamEntry::SubBlock:
       switch (Entry.ID) {
       default:
         return error("Expect function block");
       case bitc::FUNCTION_BLOCK_ID:
-        if (std::error_code EC = rememberAndSkipFunctionBody())
-          return EC;
+        if (Error Err = rememberAndSkipFunctionBody())
+          return Err;
         NextUnreadBit = Stream.GetCurrentBitNo();
-        return std::error_code();
+        return Error::success();
       }
     }
   }
 }
 
-std::error_code BitcodeReader::parseBitcodeVersion() {
+Error BitcodeReader::parseBitcodeVersion() {
   if (Stream.EnterSubBlock(bitc::IDENTIFICATION_BLOCK_ID))
     return error("Invalid record");
 
   // Read all the records.
   SmallVector<uint64_t, 64> Record;
 
   while (true) {
     BitstreamEntry Entry = Stream.advance();
 
     switch (Entry.Kind) {
     default:
     case BitstreamEntry::Error:
       return error("Malformed block");
     case BitstreamEntry::EndBlock:
-      return std::error_code();
+      return Error::success();
     case BitstreamEntry::Record:
       // The interesting case.
       break;
     }
 
     // Read a record.
     Record.clear();
     unsigned BitCode = Stream.readRecord(Entry.ID, Record);

 bool BitcodeReaderBase::readBlockInfo() {
   Optional<BitstreamBlockInfo> NewBlockInfo = Stream.ReadBlockInfoBlock();
   if (!NewBlockInfo)
     return true;
   BlockInfo = std::move(*NewBlockInfo);
   return false;
 }
 
-std::error_code BitcodeReader::parseModule(uint64_t ResumeBit,
-                                           bool ShouldLazyLoadMetadata) {
+Error BitcodeReader::parseModule(uint64_t ResumeBit,
   if (ResumeBit)
     Stream.JumpToBit(ResumeBit);
   else if (Stream.EnterSubBlock(bitc::MODULE_BLOCK_ID))
     return error("Invalid record");
 
   SmallVector<uint64_t, 64> Record;
   std::vector<std::string> SectionTable;
   std::vector<std::string> GCTable;
case BitstreamEntry::SubBlock:
         if (Stream.SkipBlock())
           return error("Invalid record");
         break;
       case bitc::BLOCKINFO_BLOCK_ID:
         if (readBlockInfo())
           return error("Malformed block");
         break;
       case bitc::PARAMATTR_BLOCK_ID:
-        if (std::error_code EC = parseAttributeBlock())
-          return EC;
+        if (Error Err = parseAttributeBlock())
+          return Err;
         break;
       case bitc::PARAMATTR_GROUP_BLOCK_ID:
-        if (std::error_code EC = parseAttributeGroupBlock())
-          return EC;
+        if (Error Err = parseAttributeGroupBlock())
+          return Err;
         break;
       case bitc::TYPE_BLOCK_ID_NEW:
-        if (std::error_code EC = parseTypeTable())
-          return EC;
+        if (Error Err = parseTypeTable())
+          return Err;
         break;
       case bitc::VALUE_SYMTAB_BLOCK_ID:
         if (!SeenValueSymbolTable) {
           // Either this is an old form VST without function index and an
           // associated VST forward declaration record (which would have caused
           // the VST to be jumped to and parsed before it was encountered
           // normally in the stream), or there were no function blocks to
           // trigger an earlier parsing of the VST.
           assert(VSTOffset == 0 || FunctionsWithBodies.empty());
-          if (std::error_code EC = parseValueSymbolTable())
-            return EC;
+          if (Error Err = parseValueSymbolTable())
+            return Err;
           SeenValueSymbolTable = true;
         } else {
           // We must have had a VST forward declaration record, which caused
           // the parser to jump to and parse the VST earlier.
           assert(VSTOffset > 0);
           if (Stream.SkipBlock())
             return error("Invalid record");
         }
         break;
       case bitc::CONSTANTS_BLOCK_ID:
-        if (std::error_code EC = parseConstants())
-          return EC;
-        if (std::error_code EC = resolveGlobalAndIndirectSymbolInits())
-          return EC;
+        if (Error Err = parseConstants())
+          return Err;
+        if (Error Err = resolveGlobalAndIndirectSymbolInits())
+          return Err;
         break;
       case bitc::METADATA_BLOCK_ID:
         if (ShouldLazyLoadMetadata && !IsMetadataMaterialized) {
-          if (std::error_code EC = rememberAndSkipMetadata())
-            return EC;
+          if (Error Err = rememberAndSkipMetadata())
+            return Err;
           break;
         }
         assert(DeferredMetadataInfo.empty() && "Unexpected deferred metadata");
-        if (std::error_code EC = parseMetadata(true))
-          return EC;
+        if (Error Err = parseMetadata(true))
+          return Err;
         break;
       case bitc::METADATA_KIND_BLOCK_ID:
-        if (std::error_code EC = parseMetadataKinds())
-          return EC;
+        if (Error Err = parseMetadataKinds())
+          return Err;
         break;
       case bitc::FUNCTION_BLOCK_ID:
         // If this is the first function body we've seen, reverse the
         // FunctionsWithBodies list.
         if (!SeenFirstFunctionBody) {
           std::reverse(FunctionsWithBodies.begin(), FunctionsWithBodies.end());
-          if (std::error_code EC = globalCleanup())
-            return EC;
+          if (Error Err = globalCleanup())
+            return Err;
           SeenFirstFunctionBody = true;
         }
 
         if (VSTOffset > 0) {
           // If we have a VST forward declaration record, make sure we
           // parse the VST now if we haven't already. It is needed to
           // set up the DeferredFunctionInfo vector for lazy reading.
           if (!SeenValueSymbolTable) {
-            if (std::error_code EC =
-                    BitcodeReader::parseValueSymbolTable(VSTOffset))
-              return EC;
+            if (Error Err = BitcodeReader::parseValueSymbolTable(VSTOffset))
+              return Err;
             SeenValueSymbolTable = true;
             // Fall through so that we record the NextUnreadBit below.
             // This is necessary in case we have an anonymous function that
             // is later materialized. Since it will not have a VST entry we
             // need to fall back to the lazy parse to find its offset.
           } else {
             // If we have a VST forward declaration record, but have already
             // parsed the VST (just above, when the first function body was
             // encountered here), then we are resuming the parse after
             // materializing functions. The ResumeBit points to the
             // start of the last function block recorded in the
             // DeferredFunctionInfo map. Skip it.
             if (Stream.SkipBlock())
               return error("Invalid record");
             continue;
           }
         }
 
         // Support older bitcode files that did not have the function
         // index in the VST, nor a VST forward declaration record, as
         // well as anonymous functions that do not have VST entries.
         // Build the DeferredFunctionInfo vector on the fly.
-        if (std::error_code EC = rememberAndSkipFunctionBody())
-          return EC;
+        if (Error Err = rememberAndSkipFunctionBody())
+          return Err;
 
         // Suspend parsing when we reach the function bodies. Subsequent
         // materialization calls will resume it when necessary. If the bitcode
         // file is old, the symbol table will be at the end instead and will not
         // have been seen yet. In this case, just finish the parse now.
         if (SeenValueSymbolTable) {
           NextUnreadBit = Stream.GetCurrentBitNo();
           // After the VST has been parsed, we need to make sure intrinsic name
           // are auto-upgraded.
           return globalCleanup();
         }
         break;
       case bitc::USELIST_BLOCK_ID:
-        if (std::error_code EC = parseUseLists())
-          return EC;
+        if (Error Err = parseUseLists())
+          return Err;
         break;
       case bitc::OPERAND_BUNDLE_TAGS_BLOCK_ID:
-        if (std::error_code EC = parseOperandBundleTags())
-          return EC;
+        if (Error Err = parseOperandBundleTags())
+          return Err;
         break;
       }
       continue;
 
     case BitstreamEntry::Record:
       // The interesting case.
       break;
     }
case bitc::MODULE_CODE_GLOBALVAR: {
           return error("Invalid type for value");
         AddressSpace = cast<PointerType>(Ty)->getAddressSpace();
         Ty = cast<PointerType>(Ty)->getElementType();
       }
 
       uint64_t RawLinkage = Record[3];
       GlobalValue::LinkageTypes Linkage = getDecodedLinkage(RawLinkage);
       unsigned Alignment;
-      if (std::error_code EC = parseAlignmentValue(Record[4], Alignment))
-        return EC;
+      if (Error Err = parseAlignmentValue(Record[4], Alignment))
+        return Err;
       std::string Section;
       if (Record[5]) {
         if (Record[5]-1 >= SectionTable.size())
           return error("Invalid ID");
         Section = SectionTable[Record[5]-1];
       }
       GlobalValue::VisibilityTypes Visibility = GlobalValue::DefaultVisibility;
       // Local linkage must have default visibility.
case bitc::MODULE_CODE_FUNCTION: {
 
       Func->setCallingConv(CC);
       bool isProto = Record[2];
       uint64_t RawLinkage = Record[3];
       Func->setLinkage(getDecodedLinkage(RawLinkage));
       Func->setAttributes(getAttributes(Record[4]));
 
       unsigned Alignment;
-      if (std::error_code EC = parseAlignmentValue(Record[5], Alignment))
-        return EC;
+      if (Error Err = parseAlignmentValue(Record[5], Alignment))
+        return Err;
       Func->setAlignment(Alignment);
       if (Record[6]) {
         if (Record[6]-1 >= SectionTable.size())
           return error("Invalid ID");
         Func->setSection(SectionTable[Record[6]-1]);
       }
       // Local linkage must have default visibility.
       if (!Func->hasLocalLinkage())
if (!Stream.canSkipToPos(4) ||
       Stream.Read(4) != 0x0 ||
       Stream.Read(4) != 0xC ||
       Stream.Read(4) != 0xE ||
       Stream.Read(4) != 0xD)
     return false;
   return true;
 }
 
-std::error_code BitcodeReader::parseBitcodeInto(Module *M,
-                                                bool ShouldLazyLoadMetadata) {
+Error BitcodeReader::parseBitcodeInto(Module *M, bool ShouldLazyLoadMetadata) {
   TheModule = M;
 
-  if (std::error_code EC = initStream())
-    return EC;
+  if (Error Err = initStream())
+    return Err;
 
   // Sniff for the signature.
   if (!hasValidBitcodeHeader(Stream))
     return error("Invalid bitcode signature");
 
   // We expect a number of well-defined blocks, though we don't necessarily
   // need to understand them all.
   while (true) {
     if (Stream.AtEndOfStream()) {
       // We didn't really read a proper Module.
       return error("Malformed IR file");
     }
 
     BitstreamEntry Entry =
       Stream.advance(BitstreamCursor::AF_DontAutoprocessAbbrevs);
 
     if (Entry.Kind != BitstreamEntry::SubBlock)
       return error("Malformed block");
 
     if (Entry.ID == bitc::IDENTIFICATION_BLOCK_ID) {
-      parseBitcodeVersion();
+      if (Error Err = parseBitcodeVersion())
+        return Err;
       continue;
     }
 
     if (Entry.ID == bitc::MODULE_BLOCK_ID)
       return parseModule(0, ShouldLazyLoadMetadata);
 
     if (Stream.SkipBlock())
       return error("Invalid record");
   }
 }
 
-ErrorOr<std::string> BitcodeReader::parseModuleTriple() {
+Expected<std::string> BitcodeReader::parseModuleTriple() {
   if (Stream.EnterSubBlock(bitc::MODULE_BLOCK_ID))
     return error("Invalid record");
 
   SmallVector<uint64_t, 64> Record;
 
   std::string Triple;
 
   // Read all the records for this module.
case bitc::MODULE_CODE_TRIPLE: {  // TRIPLE: [strchr x N]
       break;
     }
     }
     Record.clear();
   }
   llvm_unreachable("Exit infinite loop");
 }
 
-ErrorOr<std::string> BitcodeReader::parseTriple() {
-  if (std::error_code EC = initStream())
-    return EC;
+Expected<std::string> BitcodeReader::parseTriple() {
+  if (Error Err = initStream())
+    return std::move(Err);
 
   // Sniff for the signature.
   if (!hasValidBitcodeHeader(Stream))
     return error("Invalid bitcode signature");
 
   // We expect a number of well-defined blocks, though we don't necessarily
   // need to understand them all.
   while (true) {
     BitstreamEntry Entry = Stream.advance();
 
     switch (Entry.Kind) {
     case BitstreamEntry::Error:
       return error("Malformed block");
     case BitstreamEntry::EndBlock:
-      return std::error_code();
+      return Error::success();
 
     case BitstreamEntry::SubBlock:
       if (Entry.ID == bitc::MODULE_BLOCK_ID)
         return parseModuleTriple();
 
       // Ignore other sub-blocks.
       if (Stream.SkipBlock())
         return error("Malformed block");
       continue;
 
     case BitstreamEntry::Record:
       Stream.skipRecord(Entry.ID);
       continue;
     }
   }
 }
 
-ErrorOr<std::string> BitcodeReader::parseIdentificationBlock() {
-  if (std::error_code EC = initStream())
-    return EC;
+Expected<std::string> BitcodeReader::parseIdentificationBlock() {
+  if (Error Err = initStream())
+    return std::move(Err);
 
   // Sniff for the signature.
   if (!hasValidBitcodeHeader(Stream))
     return error("Invalid bitcode signature");
 
   // We expect a number of well-defined blocks, though we don't necessarily
   // need to understand them all.
   while (true) {
     BitstreamEntry Entry = Stream.advance();
     switch (Entry.Kind) {
     case BitstreamEntry::Error:
       return error("Malformed block");
     case BitstreamEntry::EndBlock:
-      return std::error_code();
+      return Error::success();
 
     case BitstreamEntry::SubBlock:
       if (Entry.ID == bitc::IDENTIFICATION_BLOCK_ID) {
-        if (std::error_code EC = parseBitcodeVersion())
-          return EC;
+        if (Error Err = parseBitcodeVersion())
+          return std::move(Err);
         return ProducerIdentification;
       }
       // Ignore other sub-blocks.
       if (Stream.SkipBlock())
         return error("Malformed block");
       continue;
     case BitstreamEntry::Record:
       Stream.skipRecord(Entry.ID);
       continue;
     }
   }
 }
 
-std::error_code BitcodeReader::parseGlobalObjectAttachment(
-    GlobalObject &GO, ArrayRef<uint64_t> Record) {
+Error BitcodeReader::parseGlobalObjectAttachment(GlobalObject &GO,
+                                                 ArrayRef<uint64_t> Record) {
   assert(Record.size() % 2 == 0);
   for (unsigned I = 0, E = Record.size(); I != E; I += 2) {
     auto K = MDKindMap.find(Record[I]);
     if (K == MDKindMap.end())
       return error("Invalid ID");
     MDNode *MD = MetadataList.getMDNodeFwdRefOrNull(Record[I + 1]);
     if (!MD)
       return error("Invalid metadata attachment");
     GO.addMetadata(K->second, *MD);
   }
-  return std::error_code();
+  return Error::success();
 }
 
-ErrorOr<bool> BitcodeReader::hasObjCCategory() {
-  if (std::error_code EC = initStream())
-    return EC;
+Expected<bool> BitcodeReader::hasObjCCategory() {
+  if (Error Err = initStream())
+    return std::move(Err);
 
   // Sniff for the signature.
   if (!hasValidBitcodeHeader(Stream))
     return error("Invalid bitcode signature");
 
   // We expect a number of well-defined blocks, though we don't necessarily
   // need to understand them all.
   while (true) {
     BitstreamEntry Entry = Stream.advance();
 
     switch (Entry.Kind) {
     case BitstreamEntry::Error:
       return error("Malformed block");
     case BitstreamEntry::EndBlock:
-      return std::error_code();
+      return Error::success();
 
     case BitstreamEntry::SubBlock:
       if (Entry.ID == bitc::MODULE_BLOCK_ID)
         return hasObjCCategoryInModule();
 
       // Ignore other sub-blocks.
       if (Stream.SkipBlock())
         return error("Malformed block");
       continue;
 
     case BitstreamEntry::Record:
       Stream.skipRecord(Entry.ID);
       continue;
     }
   }
 }
 
-ErrorOr<bool> BitcodeReader::hasObjCCategoryInModule() {
+Expected<bool> BitcodeReader::hasObjCCategoryInModule() {
   if (Stream.EnterSubBlock(bitc::MODULE_BLOCK_ID))
     return error("Invalid record");
 
   SmallVector<uint64_t, 64> Record;
   // Read all the records for this module.
 
   while (true) {
     BitstreamEntry Entry = Stream.advanceSkippingSubblocks();
while (true) {
     }
     }
     Record.clear();
   }
   llvm_unreachable("Exit infinite loop");
 }
 
 /// Parse metadata attachments.
-std::error_code BitcodeReader::parseMetadataAttachment(Function &F) {
+Error BitcodeReader::parseMetadataAttachment(Function &F) {
   if (Stream.EnterSubBlock(bitc::METADATA_ATTACHMENT_ID))
     return error("Invalid record");
 
   SmallVector<uint64_t, 64> Record;
 
   while (true) {
     BitstreamEntry Entry = Stream.advanceSkippingSubblocks();
 
     switch (Entry.Kind) {
     case BitstreamEntry::SubBlock: // Handled for us already.
     case BitstreamEntry::Error:
       return error("Malformed block");
     case BitstreamEntry::EndBlock:
-      return std::error_code();
+      return Error::success();
     case BitstreamEntry::Record:
       // The interesting case.
       break;
     }
 
     // Read a metadata attachment record.
     Record.clear();
     switch (Stream.readRecord(Entry.ID, Record)) {
     default:  // Default behavior: ignore.
       break;
     case bitc::METADATA_ATTACHMENT: {
       unsigned RecordLength = Record.size();
       if (Record.empty())
         return error("Invalid record");
       if (RecordLength % 2 == 0) {
         // A function attachment.
-        if (std::error_code EC = parseGlobalObjectAttachment(F, Record))
-          return EC;
+        if (Error Err = parseGlobalObjectAttachment(F, Record))
+          return Err;
         continue;
       }
 
       // An instruction attachment.
       Instruction *Inst = InstructionList[Record[0]];
       for (unsigned i = 1; i != RecordLength; i = i+2) {
         unsigned Kind = Record[i];
         DenseMap<unsigned, unsigned>::iterator I =
case bitc::METADATA_ATTACHMENT: {
         Inst->setMetadata(I->second, MD);
       }
       break;
     }
     }
   }
 }
 
-static std::error_code typeCheckLoadStoreInst(Type *ValType, Type *PtrType) {
-  LLVMContext &Context = PtrType->getContext();
+static Error typeCheckLoadStoreInst(Type *ValType, Type *PtrType) {
   if (!isa<PointerType>(PtrType))
-    return error(Context, "Load/Store operand is not a pointer type");
+    return error("Load/Store operand is not a pointer type");
   Type *ElemType = cast<PointerType>(PtrType)->getElementType();
 
   if (ValType && ValType != ElemType)
-    return error(Context, "Explicit load/store type does not match pointee "
-                          "type of pointer operand");
+    return error("Explicit load/store type does not match pointee "
   if (!PointerType::isLoadableOrStorableType(ElemType))
-    return error(Context, "Cannot load/store from pointer");
-  return std::error_code();
+    return error("Cannot load/store from pointer");
+  return Error::success();
 }
 
 /// Lazily parse the specified function body block.
-std::error_code BitcodeReader::parseFunctionBody(Function *F) {
+Error BitcodeReader::parseFunctionBody(Function *F) {
   if (Stream.EnterSubBlock(bitc::FUNCTION_BLOCK_ID))
     return error("Invalid record");
 
   // Unexpected unresolved metadata when parsing function.
   if (MetadataList.hasFwdRefs())
     return error("Invalid function metadata: incoming forward references");
 
   InstructionList.clear();
while (true) {
 
     case BitstreamEntry::SubBlock:
       switch (Entry.ID) {
       default:  // Skip unknown content.
         if (Stream.SkipBlock())
           return error("Invalid record");
         break;
       case bitc::CONSTANTS_BLOCK_ID:
-        if (std::error_code EC = parseConstants())
-          return EC;
+        if (Error Err = parseConstants())
+          return Err;
         NextValueNo = ValueList.size();
         break;
       case bitc::VALUE_SYMTAB_BLOCK_ID:
-        if (std::error_code EC = parseValueSymbolTable())
-          return EC;
+        if (Error Err = parseValueSymbolTable())
+          return Err;
         break;
       case bitc::METADATA_ATTACHMENT_ID:
-        if (std::error_code EC = parseMetadataAttachment(*F))
-          return EC;
+        if (Error Err = parseMetadataAttachment(*F))
+          return Err;
         break;
       case bitc::METADATA_BLOCK_ID:
-        if (std::error_code EC = parseMetadata())
-          return EC;
+        if (Error Err = parseMetadata())
+          return Err;
         break;
       case bitc::USELIST_BLOCK_ID:
-        if (std::error_code EC = parseUseLists())
-          return EC;
+        if (Error Err = parseUseLists())
+          return Err;
         break;
       }
       continue;
 
     case BitstreamEntry::Record:
       // The interesting case.
       break;
     }
case bitc::FUNC_CODE_INST_ALLOCA: { // ALLOCA: [instty, opty, op, align]
         auto *PTy = dyn_cast_or_null<PointerType>(Ty);
         if (!PTy)
           return error("Old-style alloca with a non-pointer type");
         Ty = PTy->getElementType();
       }
       Type *OpTy = getTypeByID(Record[1]);
       Value *Size = getFnValueByID(Record[2], OpTy);
       unsigned Align;
-      if (std::error_code EC =
-              parseAlignmentValue(AlignRecord & ~FlagMask, Align)) {
-        return EC;
+      if (Error Err = parseAlignmentValue(AlignRecord & ~FlagMask, Align)) {
+        return Err;
       }
       if (!Ty || !Size)
         return error("Invalid record");
       AllocaInst *AI = new AllocaInst(Ty, Size, Align);
       AI->setUsedWithInAlloca(InAlloca);
       AI->setSwiftError(SwiftError);
       I = AI;
       InstructionList.push_back(I);
       break;
     }
     case bitc::FUNC_CODE_INST_LOAD: { // LOAD: [opty, op, align, vol]
       unsigned OpNum = 0;
       Value *Op;
       if (getValueTypePair(Record, OpNum, NextValueNo, Op) ||
           (OpNum + 2 != Record.size() && OpNum + 3 != Record.size()))
         return error("Invalid record");
 
       Type *Ty = nullptr;
       if (OpNum + 3 == Record.size())
         Ty = getTypeByID(Record[OpNum++]);
-      if (std::error_code EC = typeCheckLoadStoreInst(Ty, Op->getType()))
-        return EC;
+      if (Error Err = typeCheckLoadStoreInst(Ty, Op->getType()))
+        return Err;
       if (!Ty)
         Ty = cast<PointerType>(Op->getType())->getElementType();
 
       unsigned Align;
-      if (std::error_code EC = parseAlignmentValue(Record[OpNum], Align))
-        return EC;
+      if (Error Err = parseAlignmentValue(Record[OpNum], Align))
+        return Err;
       I = new LoadInst(Ty, Op, "", Record[OpNum + 1], Align);
 
       InstructionList.push_back(I);
       break;
     }
     case bitc::FUNC_CODE_INST_LOADATOMIC: {
        // LOADATOMIC: [opty, op, align, vol, ordering, synchscope]
       unsigned OpNum = 0;
       Value *Op;
       if (getValueTypePair(Record, OpNum, NextValueNo, Op) ||
           (OpNum + 4 != Record.size() && OpNum + 5 != Record.size()))
         return error("Invalid record");
 
       Type *Ty = nullptr;
       if (OpNum + 5 == Record.size())
         Ty = getTypeByID(Record[OpNum++]);
-      if (std::error_code EC = typeCheckLoadStoreInst(Ty, Op->getType()))
-        return EC;
+      if (Error Err = typeCheckLoadStoreInst(Ty, Op->getType()))
+        return Err;
       if (!Ty)
         Ty = cast<PointerType>(Op->getType())->getElementType();
 
       AtomicOrdering Ordering = getDecodedOrdering(Record[OpNum + 2]);
       if (Ordering == AtomicOrdering::NotAtomic ||
           Ordering == AtomicOrdering::Release ||
           Ordering == AtomicOrdering::AcquireRelease)
         return error("Invalid record");
       if (Ordering != AtomicOrdering::NotAtomic && Record[OpNum] == 0)
         return error("Invalid record");
       SynchronizationScope SynchScope = getDecodedSynchScope(Record[OpNum + 3]);
 
       unsigned Align;
-      if (std::error_code EC = parseAlignmentValue(Record[OpNum], Align))
-        return EC;
+      if (Error Err = parseAlignmentValue(Record[OpNum], Align))
+        return Err;
       I = new LoadInst(Op, "", Record[OpNum+1], Align, Ordering, SynchScope);
 
       InstructionList.push_back(I);
       break;
     }
     case bitc::FUNC_CODE_INST_STORE:
     case bitc::FUNC_CODE_INST_STORE_OLD: { // STORE2:[ptrty, ptr, val, align, vol]
       unsigned OpNum = 0;
       Value *Val, *Ptr;
       if (getValueTypePair(Record, OpNum, NextValueNo, Ptr) ||
           (BitCode == bitc::FUNC_CODE_INST_STORE
                ? getValueTypePair(Record, OpNum, NextValueNo, Val)
                : popValue(Record, OpNum, NextValueNo,
                           cast<PointerType>(Ptr->getType())->getElementType(),
                           Val)) ||
           OpNum + 2 != Record.size())
         return error("Invalid record");
 
-      if (std::error_code EC =
-              typeCheckLoadStoreInst(Val->getType(), Ptr->getType()))
-        return EC;
+      if (Error Err = typeCheckLoadStoreInst(Val->getType(), Ptr->getType()))
+        return Err;
       unsigned Align;
-      if (std::error_code EC = parseAlignmentValue(Record[OpNum], Align))
-        return EC;
+      if (Error Err = parseAlignmentValue(Record[OpNum], Align))
+        return Err;
       I = new StoreInst(Val, Ptr, Record[OpNum+1], Align);
       InstructionList.push_back(I);
       break;
     }
     case bitc::FUNC_CODE_INST_STOREATOMIC:
     case bitc::FUNC_CODE_INST_STOREATOMIC_OLD: {
       // STOREATOMIC: [ptrty, ptr, val, align, vol, ordering, synchscope]
       unsigned OpNum = 0;
       Value *Val, *Ptr;
       if (getValueTypePair(Record, OpNum, NextValueNo, Ptr) ||
           !isa<PointerType>(Ptr->getType()) ||
           (BitCode == bitc::FUNC_CODE_INST_STOREATOMIC
                ? getValueTypePair(Record, OpNum, NextValueNo, Val)
                : popValue(Record, OpNum, NextValueNo,
                           cast<PointerType>(Ptr->getType())->getElementType(),
                           Val)) ||
           OpNum + 4 != Record.size())
         return error("Invalid record");
 
-      if (std::error_code EC =
-              typeCheckLoadStoreInst(Val->getType(), Ptr->getType()))
-        return EC;
+      if (Error Err = typeCheckLoadStoreInst(Val->getType(), Ptr->getType()))
+        return Err;
       AtomicOrdering Ordering = getDecodedOrdering(Record[OpNum + 2]);
       if (Ordering == AtomicOrdering::NotAtomic ||
           Ordering == AtomicOrdering::Acquire ||
           Ordering == AtomicOrdering::AcquireRelease)
         return error("Invalid record");
       SynchronizationScope SynchScope = getDecodedSynchScope(Record[OpNum + 3]);
       if (Ordering != AtomicOrdering::NotAtomic && Record[OpNum] == 0)
         return error("Invalid record");
 
       unsigned Align;
-      if (std::error_code EC = parseAlignmentValue(Record[OpNum], Align))
-        return EC;
+      if (Error Err = parseAlignmentValue(Record[OpNum], Align))
+        return Err;
       I = new StoreInst(Val, Ptr, Record[OpNum+1], Align, Ordering, SynchScope);
       InstructionList.push_back(I);
       break;
     }
     case bitc::FUNC_CODE_INST_CMPXCHG_OLD:
     case bitc::FUNC_CODE_INST_CMPXCHG: {
       // CMPXCHG:[ptrty, ptr, cmp, new, vol, successordering, synchscope,
       //          failureordering?, isweak?]
case bitc::FUNC_CODE_INST_CMPXCHG: {
           Record.size() < OpNum + 3 || Record.size() > OpNum + 5)
         return error("Invalid record");
       AtomicOrdering SuccessOrdering = getDecodedOrdering(Record[OpNum + 1]);
       if (SuccessOrdering == AtomicOrdering::NotAtomic ||
           SuccessOrdering == AtomicOrdering::Unordered)
         return error("Invalid record");
       SynchronizationScope SynchScope = getDecodedSynchScope(Record[OpNum + 2]);
 
-      if (std::error_code EC =
-              typeCheckLoadStoreInst(Cmp->getType(), Ptr->getType()))
-        return EC;
+      if (Error Err = typeCheckLoadStoreInst(Cmp->getType(), Ptr->getType()))
+        return Err;
       AtomicOrdering FailureOrdering;
       if (Record.size() < 7)
         FailureOrdering =
             AtomicCmpXchgInst::getStrongestFailureOrdering(SuccessOrdering);
       else
         FailureOrdering = getDecodedOrdering(Record[OpNum + 3]);
 
       I = new AtomicCmpXchgInst(Ptr, Cmp, New, SuccessOrdering, FailureOrdering,
OutOfRecordLoop:
   // Unexpected unresolved metadata about to be dropped.
   if (MetadataList.hasFwdRefs())
     return error("Invalid function metadata: outgoing forward refs");
 
   // Trim the value list down to the size it was before we parsed this function.
   ValueList.shrinkTo(ModuleValueListSize);
   MetadataList.shrinkTo(ModuleMetadataListSize);
   std::vector<BasicBlock*>().swap(FunctionBBs);
-  return std::error_code();
+  return Error::success();
 }
 
 /// Find the function body in the bitcode stream
-std::error_code BitcodeReader::findFunctionInStream(
+Error BitcodeReader::findFunctionInStream(
     Function *F,
     DenseMap<Function *, uint64_t>::iterator DeferredFunctionInfoIterator) {
   while (DeferredFunctionInfoIterator->second == 0) {
     // This is the fallback handling for the old format bitcode that
     // didn't contain the function index in the VST, or when we have
     // an anonymous function which would not have a VST entry.
     // Assert that we have one of those two cases.
     assert(VSTOffset == 0 || !F->hasName());
     // Parse the next body in the stream and set its position in the
     // DeferredFunctionInfo map.
-    if (std::error_code EC = rememberAndSkipFunctionBodies())
-      return EC;
+    if (Error Err = rememberAndSkipFunctionBodies())
+      return Err;
   }
-  return std::error_code();
+  return Error::success();
 }
 
 //===----------------------------------------------------------------------===//
 // GVMaterializer implementation
 //===----------------------------------------------------------------------===//
 
 std::error_code BitcodeReader::materialize(GlobalValue *GV) {
+  return errorToErrorCodeAndEmitErrors(Context, materializeImpl(GV));
+}
+
+Error BitcodeReader::materializeImpl(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();
+    return Error::success();
 
   DenseMap<Function*, uint64_t>::iterator DFII = DeferredFunctionInfo.find(F);
   assert(DFII != DeferredFunctionInfo.end() && "Deferred function not found!");
   // If its position is recorded as 0, its body is somewhere in the stream
   // but we haven't seen it yet.
   if (DFII->second == 0)
-    if (std::error_code EC = findFunctionInStream(F, DFII))
-      return EC;
+    if (Error Err = findFunctionInStream(F, DFII))
+      return Err;
 
   // Materialize metadata before parsing any function bodies.
-  if (std::error_code EC = materializeMetadata())
-    return EC;
+  if (Error Err = materializeMetadataImpl())
+    return Err;
 
   // Move the bit stream to the saved position of the deferred function body.
   Stream.JumpToBit(DFII->second);
 
-  if (std::error_code EC = parseFunctionBody(F))
-    return EC;
+  if (Error Err = parseFunctionBody(F))
+    return Err;
   F->setIsMaterializable(false);
 
   if (StripDebugInfo)
     stripDebugInfo(*F);
 
   // Upgrade any old intrinsic calls in the function.
   for (auto &I : UpgradedIntrinsics) {
     for (auto UI = I.first->materialized_user_begin(), UE = I.first->user_end();
if (DISubprogram *SP = FunctionsWithSPs.lookup(F))
     F->setSubprogram(SP);
 
   // Bring in any functions that this function forward-referenced via
   // blockaddresses.
   return materializeForwardReferencedFunctions();
 }
 
 std::error_code BitcodeReader::materializeModule() {
-  if (std::error_code EC = materializeMetadata())
-    return EC;
+  return errorToErrorCodeAndEmitErrors(Context, materializeModuleImpl());
+}
+
+Error BitcodeReader::materializeModuleImpl() {
+  if (Error Err = materializeMetadataImpl())
+    return Err;
 
   // Promise to materialize all forward references.
   WillMaterializeAllForwardRefs = true;
 
   // Iterate over the module, deserializing any functions that are still on
   // disk.
   for (Function &F : *TheModule) {
-    if (std::error_code EC = materialize(&F))
-      return EC;
+    if (Error Err = materializeImpl(&F))
+      return Err;
   }
   // At this point, if there are any function bodies, parse the rest of
   // the bits in the module past the last function block we have recorded
   // through either lazy scanning or the VST.
   if (LastFunctionBlockBit || NextUnreadBit)
-    parseModule(LastFunctionBlockBit > NextUnreadBit ? LastFunctionBlockBit
-                                                     : NextUnreadBit);
+    if (Error Err = parseModule(LastFunctionBlockBit > NextUnreadBit
+                                    ? LastFunctionBlockBit
+                                    : NextUnreadBit))
+      return Err;
 
   // Check that all block address forward references got resolved (as we
   // promised above).
   if (!BasicBlockFwdRefs.empty())
     return error("Never resolved function from blockaddress");
 
   // Upgrade any intrinsic calls that slipped through (should not happen!) and
   // delete the old functions to clean up. We can't do this unless the entire
for (auto &I : RemangledIntrinsics) {
     I.first->replaceAllUsesWith(I.second);
     I.first->eraseFromParent();
   }
   RemangledIntrinsics.clear();
 
   UpgradeDebugInfo(*TheModule);
 
   UpgradeModuleFlags(*TheModule);
-  return std::error_code();
+  return Error::success();
 }
 
 std::vector<StructType *> BitcodeReader::getIdentifiedStructTypes() const {
   return IdentifiedStructTypes;
 }
 
-std::error_code ModuleSummaryIndexBitcodeReader::error(const Twine &Message) {
-  return ::error(DiagnosticHandler,
-                 make_error_code(BitcodeError::CorruptedBitcode), Message);
-}
-
 ModuleSummaryIndexBitcodeReader::ModuleSummaryIndexBitcodeReader(
-    MemoryBufferRef Buffer, DiagnosticHandlerFunction DiagnosticHandler,
-    bool CheckGlobalValSummaryPresenceOnly)
+    MemoryBufferRef Buffer, bool CheckGlobalValSummaryPresenceOnly)
     : BitcodeReaderBase(Buffer),
-      DiagnosticHandler(std::move(DiagnosticHandler)),
       CheckGlobalValSummaryPresenceOnly(CheckGlobalValSummaryPresenceOnly) {}
 
 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
 // blocks where we don't actually create global values. The parsed information
 // is saved in the bitcode reader for use when later parsing summaries.
-std::error_code ModuleSummaryIndexBitcodeReader::parseValueSymbolTable(
+Error ModuleSummaryIndexBitcodeReader::parseValueSymbolTable(
     uint64_t Offset,
     DenseMap<unsigned, GlobalValue::LinkageTypes> &ValueIdToLinkageMap) {
   assert(Offset > 0 && "Expected non-zero VST offset");
   uint64_t CurrentBit = jumpToValueSymbolTable(Offset, Stream);
 
   if (Stream.EnterSubBlock(bitc::VALUE_SYMTAB_BLOCK_ID))
     return error("Invalid record");
 
   SmallVector<uint64_t, 64> Record;
 
   // Read all the records for this value table.
   SmallString<128> ValueName;
 
   while (true) {
     BitstreamEntry Entry = Stream.advanceSkippingSubblocks();
 
     switch (Entry.Kind) {
     case BitstreamEntry::SubBlock: // Handled for us already.
     case BitstreamEntry::Error:
       return error("Malformed block");
     case BitstreamEntry::EndBlock:
       // Done parsing VST, jump back to wherever we came from.
       Stream.JumpToBit(CurrentBit);
-      return std::error_code();
+      return Error::success();
     case BitstreamEntry::Record:
       // The interesting case.
       break;
     }
 
     // Read a record.
     Record.clear();
     switch (Stream.readRecord(Entry.ID, Record)) {
while (true) {
     }
     }
   }
 }
 
 // Parse just the blocks needed for building the index out of the module.
 // At the end of this routine the module Index is populated with a map
 // from global value id to GlobalValueSummary objects.
-std::error_code ModuleSummaryIndexBitcodeReader::parseModule() {
+Error ModuleSummaryIndexBitcodeReader::parseModule() {
   if (Stream.EnterSubBlock(bitc::MODULE_BLOCK_ID))
     return error("Invalid record");
 
   SmallVector<uint64_t, 64> Record;
   DenseMap<unsigned, GlobalValue::LinkageTypes> ValueIdToLinkageMap;
   unsigned ValueId = 0;
 
   // Read the index for this module.
   while (true) {
     BitstreamEntry Entry = Stream.advance();
 
     switch (Entry.Kind) {
     case BitstreamEntry::Error:
       return error("Malformed block");
     case BitstreamEntry::EndBlock:
-      return std::error_code();
+      return Error::success();
 
     case BitstreamEntry::SubBlock:
       if (CheckGlobalValSummaryPresenceOnly) {
         if (Entry.ID == bitc::GLOBALVAL_SUMMARY_BLOCK_ID) {
           SeenGlobalValSummary = true;
           // No need to parse the rest since we found the summary.
-          return std::error_code();
+          return Error::success();
         }
         if (Stream.SkipBlock())
           return error("Invalid record");
         continue;
       }
       switch (Entry.ID) {
       default: // Skip unknown content.
         if (Stream.SkipBlock())
case BitstreamEntry::SubBlock:
       case bitc::GLOBALVAL_SUMMARY_BLOCK_ID:
         assert(!SeenValueSymbolTable &&
                "Already read VST when parsing summary block?");
         // We might not have a VST if there were no values in the
         // summary. An empty summary block generated when we are
         // performing ThinLTO compiles so we don't later invoke
         // the regular LTO process on them.
         if (VSTOffset > 0) {
-          if (std::error_code EC =
-                  parseValueSymbolTable(VSTOffset, ValueIdToLinkageMap))
-            return EC;
+          if (Error Err = parseValueSymbolTable(VSTOffset, ValueIdToLinkageMap))
+            return Err;
           SeenValueSymbolTable = true;
         }
         SeenGlobalValSummary = true;
-        if (std::error_code EC = parseEntireSummary())
-          return EC;
+        if (Error Err = parseEntireSummary())
+          return Err;
         break;
       case bitc::MODULE_STRTAB_BLOCK_ID:
-        if (std::error_code EC = parseModuleStringTable())
-          return EC;
+        if (Error Err = parseModuleStringTable())
+          return Err;
         break;
       }
       continue;
 
     case BitstreamEntry::Record: {
         Record.clear();
         auto BitCode = Stream.readRecord(Entry.ID, Record);
         switch (BitCode) {
case BitstreamEntry::Record: {
       }
       continue;
     }
   }
 }
 
 // Eagerly parse the entire summary block. This populates the GlobalValueSummary
 // objects in the index.
-std::error_code ModuleSummaryIndexBitcodeReader::parseEntireSummary() {
+Error ModuleSummaryIndexBitcodeReader::parseEntireSummary() {
   if (Stream.EnterSubBlock(bitc::GLOBALVAL_SUMMARY_BLOCK_ID))
     return error("Invalid record");
   SmallVector<uint64_t, 64> Record;
 
   // Parse version
   {
     BitstreamEntry Entry = Stream.advanceSkippingSubblocks();
     if (Entry.Kind != BitstreamEntry::Record)
case BitstreamEntry::EndBlock:
       // but not all have associated summaries (e.g. it doesn't know how to
       // distinguish between VST_CODE_ENTRY for function declarations vs global
       // variables with initializers that end up with a summary). Remove those
       // entries now so that we don't need to rely on the combined index merger
       // to clean them up (especially since that may not run for the first
       // module's index if we merge into that).
       if (!Combined)
         TheIndex->removeEmptySummaryEntries();
-      return std::error_code();
+      return Error::success();
     case BitstreamEntry::Record:
       // The interesting case.
       break;
     }
 
     // Read a record. The record format depends on whether this
     // is a per-module index or a combined index file. In the per-module
     // case the records contain the associated value's ID for correlation
if (HasProfile)
       I += 1; // Skip old profilecount field
   } else if (HasProfile)
     Hotness = static_cast<CalleeInfo::HotnessType>(Record[++I]);
   return {CalleeGUID, Hotness};
 }
 
 // Parse the  module string table block into the Index.
 // This populates the ModulePathStringTable map in the index.
-std::error_code ModuleSummaryIndexBitcodeReader::parseModuleStringTable() {
+Error ModuleSummaryIndexBitcodeReader::parseModuleStringTable() {
   if (Stream.EnterSubBlock(bitc::MODULE_STRTAB_BLOCK_ID))
     return error("Invalid record");
 
   SmallVector<uint64_t, 64> Record;
 
   SmallString<128> ModulePath;
   ModulePathStringTableTy::iterator LastSeenModulePath;
 
   while (true) {
     BitstreamEntry Entry = Stream.advanceSkippingSubblocks();
 
     switch (Entry.Kind) {
     case BitstreamEntry::SubBlock: // Handled for us already.
     case BitstreamEntry::Error:
       return error("Malformed block");
     case BitstreamEntry::EndBlock:
-      return std::error_code();
+      return Error::success();
     case BitstreamEntry::Record:
       // The interesting case.
       break;
     }
 
     Record.clear();
     switch (Stream.readRecord(Entry.ID, Record)) {
     default: // Default behavior: ignore.
case bitc::MST_CODE_HASH: {
       break;
     }
     }
   }
   llvm_unreachable("Exit infinite loop");
 }
 
 // Parse the function info index from the bitcode streamer into the given index.
-std::error_code
+Error
 ModuleSummaryIndexBitcodeReader::parseSummaryIndexInto(ModuleSummaryIndex *I) {
   TheIndex = I;
 
-  if (std::error_code EC = initStream())
-    return EC;
+  if (Error Err = initStream())
+    return Err;
 
   // Sniff for the signature.
   if (!hasValidBitcodeHeader(Stream))
     return error("Invalid bitcode signature");
 
   // We expect a number of well-defined blocks, though we don't necessarily
   // need to understand them all.
   while (true) {
getLazyBitcodeModuleImpl(MemoryBufferRef Buffer, LLVMContext &Context,
                          bool ShouldLazyLoadMetadata = false) {
   BitcodeReader *R = new BitcodeReader(Buffer, Context);
 
   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 EC;
+  if (Error Err = R->parseBitcodeInto(M.get(), ShouldLazyLoadMetadata))
+    return errorToErrorCodeAndEmitErrors(Context, std::move(Err));
 
   if (MaterializeAll) {
     // Read in the entire module, and destroy the BitcodeReader.
     if (std::error_code EC = M->materializeAll())
       return EC;
   } else {
     // Resolve forward references from blockaddresses.
-    if (std::error_code EC = R->materializeForwardReferencedFunctions())
-      return EC;
+    if (Error Err = R->materializeForwardReferencedFunctions())
+      return errorToErrorCodeAndEmitErrors(Context, std::move(Err));
   }
   return std::move(M);
 }
 
 ErrorOr<std::unique_ptr<Module>>
 llvm::getLazyBitcodeModule(MemoryBufferRef Buffer,
                            LLVMContext &Context, bool ShouldLazyLoadMetadata) {
   return getLazyBitcodeModuleImpl(Buffer, Context, false,
ErrorOr<std::unique_ptr<Module>> llvm::parseBitcodeFile(MemoryBufferRef Buffer,
   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) {
   BitcodeReader R(Buffer, Context);
-  ErrorOr<std::string> Triple = R.parseTriple();
+  ErrorOr<std::string> Triple =
+      expectedToErrorOrAndEmitErrors(Context, R.parseTriple());
   if (Triple.getError())
     return "";
   return Triple.get();
 }
 
 bool llvm::isBitcodeContainingObjCCategory(MemoryBufferRef Buffer,
                                            LLVMContext &Context) {
   BitcodeReader R(Buffer, Context);
-  ErrorOr<bool> hasObjCCategory = R.hasObjCCategory();
+  ErrorOr<bool> hasObjCCategory =
+      expectedToErrorOrAndEmitErrors(Context, R.hasObjCCategory());
   if (hasObjCCategory.getError())
     return false;
   return hasObjCCategory.get();
 }
 
 std::string llvm::getBitcodeProducerString(MemoryBufferRef Buffer,
                                            LLVMContext &Context) {
   BitcodeReader R(Buffer, Context);
-  ErrorOr<std::string> ProducerString = R.parseIdentificationBlock();
+  ErrorOr<std::string> ProducerString =
+      expectedToErrorOrAndEmitErrors(Context, 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) {
-  ModuleSummaryIndexBitcodeReader R(Buffer, DiagnosticHandler);
+  ModuleSummaryIndexBitcodeReader R(Buffer);
 
   auto Index = llvm::make_unique<ModuleSummaryIndex>();
 
-  if (std::error_code EC = R.parseSummaryIndexInto(Index.get()))
+  if (std::error_code EC = errorToErrorCodeAndEmitErrors(
+          DiagnosticHandler, R.parseSummaryIndexInto(Index.get())))
     return EC;
 
   return std::move(Index);
 }
 
 // Check if the given bitcode buffer contains a global value summary block.
 bool llvm::hasGlobalValueSummary(
     MemoryBufferRef Buffer,
     const DiagnosticHandlerFunction &DiagnosticHandler) {
-  ModuleSummaryIndexBitcodeReader R(Buffer, DiagnosticHandler, true);
+  ModuleSummaryIndexBitcodeReader R(Buffer, true);
 
-  if (R.parseSummaryIndexInto(nullptr))
+  if (errorToErrorCodeAndEmitErrors(DiagnosticHandler,
+                                    R.parseSummaryIndexInto(nullptr)))
     return false;
 
   return R.foundGlobalValSummary();
 }