1 files changed, 4 insertions, 3 deletions

diff --git a/gcc/expr.c b/gcc/expr.c
index 9eb1ae7..0e8e0eee 100644
--- a/gcc/expr.c
+++ b/gcc/expr.c
@@ -8061,9 +8061,10 @@ expand_expr_real_1 (tree exp, rtx target, enum machine_mode tmode,
 	if (fndecl
 	    && (attr = lookup_attribute ("warning",
 					 DECL_ATTRIBUTES (fndecl))) != NULL)
-	  warning (0, "%Kcall to %qs declared with attribute warning: %s",
-		   exp, lang_hooks.decl_printable_name (fndecl, 1),
-		   TREE_STRING_POINTER (TREE_VALUE (TREE_VALUE (attr))));
+	  warning_at (tree_nonartificial_location (exp),
+		      0, "%Kcall to %qs declared with attribute warning: %s",
+		      exp, lang_hooks.decl_printable_name (fndecl, 1),
+		      TREE_STRING_POINTER (TREE_VALUE (TREE_VALUE (attr))));
 
 	/* Check for a built-in function.  */
 	if (fndecl && DECL_BUILT_IN (fndecl))

path: root/gcc/expr.c

//===- BitcodeReader.cpp - Internal BitcodeReader implementation ----------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

#include "llvm/Bitcode/BitcodeReader.h"
#include "MetadataLoader.h"
#include "ValueList.h"
#include "llvm/ADT/APFloat.h"
#include "llvm/ADT/APInt.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/ADT/Twine.h"
#include "llvm/Bitcode/BitcodeCommon.h"
#include "llvm/Bitcode/LLVMBitCodes.h"
#include "llvm/Bitstream/BitstreamReader.h"
#include "llvm/Config/llvm-config.h"
#include "llvm/IR/Argument.h"
#include "llvm/IR/AttributeMask.h"
#include "llvm/IR/Attributes.h"
#include "llvm/IR/AutoUpgrade.h"
#include "llvm/IR/BasicBlock.h"
#include "llvm/IR/CallingConv.h"
#include "llvm/IR/Comdat.h"
#include "llvm/IR/Constant.h"
#include "llvm/IR/ConstantRangeList.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/DebugInfo.h"
#include "llvm/IR/DebugInfoMetadata.h"
#include "llvm/IR/DebugLoc.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/GVMaterializer.h"
#include "llvm/IR/GetElementPtrTypeIterator.h"
#include "llvm/IR/GlobalAlias.h"
#include "llvm/IR/GlobalIFunc.h"
#include "llvm/IR/GlobalObject.h"
#include "llvm/IR/GlobalValue.h"
#include "llvm/IR/GlobalVariable.h"
#include "llvm/IR/InlineAsm.h"
#include "llvm/IR/InstIterator.h"
#include "llvm/IR/InstrTypes.h"
#include "llvm/IR/Instruction.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/Intrinsics.h"
#include "llvm/IR/IntrinsicsAArch64.h"
#include "llvm/IR/IntrinsicsARM.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/Metadata.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/ModuleSummaryIndex.h"
#include "llvm/IR/Operator.h"
#include "llvm/IR/ProfDataUtils.h"
#include "llvm/IR/Type.h"
#include "llvm/IR/Value.h"
#include "llvm/IR/Verifier.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/MathExtras.h"
#include "llvm/Support/MemoryBuffer.h"
#include "llvm/Support/ModRef.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/TargetParser/Triple.h"
#include <algorithm>
#include <cassert>
#include <cstddef>
#include <cstdint>
#include <deque>
#include <map>
#include <memory>
#include <optional>
#include <string>
#include <system_error>
#include <tuple>
#include <utility>
#include <vector>

using namespace llvm;

static cl::opt<bool> PrintSummaryGUIDs(
    "print-summary-global-ids", cl::init(false), cl::Hidden,
    cl::desc(
        "Print the global id for each value when reading the module summary"));

static cl::opt<bool> ExpandConstantExprs(
    "expand-constant-exprs", cl::Hidden,
    cl::desc(
        "Expand constant expressions to instructions for testing purposes"));

namespace {

enum {
  SWITCH_INST_MAGIC = 0x4B5 // May 2012 => 1205 => Hex
};

} // end anonymous namespace

static Error error(const Twine &Message) {
  return make_error<StringError>(
      Message, make_error_code(BitcodeError::CorruptedBitcode));
}

static Error hasInvalidBitcodeHeader(BitstreamCursor &Stream) {
  if (!Stream.canSkipToPos(4))
    return createStringError(std::errc::illegal_byte_sequence,
                             "file too small to contain bitcode header");
  for (unsigned C : {'B', 'C'})
    if (Expected<SimpleBitstreamCursor::word_t> Res = Stream.Read(8)) {
      if (Res.get() != C)
        return createStringError(std::errc::illegal_byte_sequence,
                                 "file doesn't start with bitcode header");
    } else
      return Res.takeError();
  for (unsigned C : {0x0, 0xC, 0xE, 0xD})
    if (Expected<SimpleBitstreamCursor::word_t> Res = Stream.Read(4)) {
      if (Res.get() != C)
        return createStringError(std::errc::illegal_byte_sequence,
                                 "file doesn't start with bitcode header");
    } else
      return Res.takeError();
  return Error::success();
}

static Expected<BitstreamCursor> initStream(MemoryBufferRef Buffer) {
  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");

  BitstreamCursor Stream(ArrayRef<uint8_t>(BufPtr, BufEnd));
  if (Error Err = hasInvalidBitcodeHeader(Stream))
    return std::move(Err);

  return std::move(Stream);
}

/// 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) {
  if (Idx > Record.size())
    return true;

  Result.append(Record.begin() + Idx, Record.end());
  return false;
}

// Strip all the TBAA attachment for the module.
static void stripTBAA(Module *M) {
  for (auto &F : *M) {
    if (F.isMaterializable())
      continue;
    for (auto &I : instructions(F))
      I.setMetadata(LLVMContext::MD_tbaa, nullptr);
  }
}

/// Read the "IDENTIFICATION_BLOCK_ID" block, do some basic enforcement on the
/// "epoch" encoded in the bitcode, and return the producer name if any.
static Expected<std::string> readIdentificationBlock(BitstreamCursor &Stream) {
  if (Error Err = Stream.EnterSubBlock(bitc::IDENTIFICATION_BLOCK_ID))
    return std::move(Err);

  // Read all the records.
  SmallVector<uint64_t, 64> Record;

  std::string ProducerIdentification;

  while (true) {
    BitstreamEntry Entry;
    if (Error E = Stream.advance().moveInto(Entry))
      return std::move(E);

    switch (Entry.Kind) {
    default:
    case BitstreamEntry::Error:
      return error("Malformed block");
    case BitstreamEntry::EndBlock:
      return ProducerIdentification;
    case BitstreamEntry::Record:
      // The interesting case.
      break;
    }

    // Read a record.
    Record.clear();
    Expected<unsigned> MaybeBitCode = Stream.readRecord(Entry.ID, Record);
    if (!MaybeBitCode)
      return MaybeBitCode.takeError();
    switch (MaybeBitCode.get()) {
    default: // Default behavior: reject
      return error("Invalid value");
    case bitc::IDENTIFICATION_CODE_STRING: // IDENTIFICATION: [strchr x N]
      convertToString(Record, 0, ProducerIdentification);
      break;
    case bitc::IDENTIFICATION_CODE_EPOCH: { // EPOCH: [epoch#]
      unsigned epoch = (unsigned)Record[0];
      if (epoch != bitc::BITCODE_CURRENT_EPOCH) {
        return error(
          Twine("Incompatible epoch: Bitcode '") + Twine(epoch) +
          "' vs current: '" + Twine(bitc::BITCODE_CURRENT_EPOCH) + "'");
      }
    }
    }
  }
}

static Expected<std::string> readIdentificationCode(BitstreamCursor &Stream) {
  // We expect a number of well-defined blocks, though we don't necessarily
  // need to understand them all.
  while (true) {
    if (Stream.AtEndOfStream())
      return "";

    BitstreamEntry Entry;
    if (Error E = Stream.advance().moveInto(Entry))
      return std::move(E);

    switch (Entry.Kind) {
    case BitstreamEntry::EndBlock:
    case BitstreamEntry::Error:
      return error("Malformed block");

    case BitstreamEntry::SubBlock:
      if (Entry.ID == bitc::IDENTIFICATION_BLOCK_ID)
        return readIdentificationBlock(Stream);

      // Ignore other sub-blocks.
      if (Error Err = Stream.SkipBlock())
        return std::move(Err);
      continue;
    case BitstreamEntry::Record:
      if (Error E = Stream.skipRecord(Entry.ID).takeError())
        return std::move(E);
      continue;
    }
  }
}

static Expected<bool> hasObjCCategoryInModule(BitstreamCursor &Stream) {
  if (Error Err = Stream.EnterSubBlock(bitc::MODULE_BLOCK_ID))
    return std::move(Err);

  SmallVector<uint64_t, 64> Record;
  // Read all the records for this module.

  while (true) {
    Expected<BitstreamEntry> MaybeEntry = Stream.advanceSkippingSubblocks();
    if (!MaybeEntry)
      return MaybeEntry.takeError();
    BitstreamEntry Entry = MaybeEntry.get();

    switch (Entry.Kind) {
    case BitstreamEntry::SubBlock: // Handled for us already.
    case BitstreamEntry::Error:
      return error("Malformed block");
    case BitstreamEntry::EndBlock:
      return false;
    case BitstreamEntry::Record:
      // The interesting case.
      break;
    }

    // Read a record.
    Expected<unsigned> MaybeRecord = Stream.readRecord(Entry.ID, Record);
    if (!MaybeRecord)
      return MaybeRecord.takeError();
    switch (MaybeRecord.get()) {
    default:
      break; // Default behavior, ignore unknown content.
    case bitc::MODULE_CODE_SECTIONNAME: { // SECTIONNAME: [strchr x N]
      std::string S;
      if (convertToString(Record, 0, S))
        return error("Invalid section name record");
      // Check for the i386 and other (x86_64, ARM) conventions
      if (S.find("__DATA,__objc_catlist") != std::string::npos ||
          S.find("__OBJC,__category") != std::string::npos ||
          S.find("__TEXT,__swift") != std::string::npos)
        return true;
      break;
    }
    }
    Record.clear();
  }
  llvm_unreachable("Exit infinite loop");
}

static Expected<bool> hasObjCCategory(BitstreamCursor &Stream) {
  // We expect a number of well-defined blocks, though we don't necessarily
  // need to understand them all.
  while (true) {
    BitstreamEntry Entry;
    if (Error E = Stream.advance().moveInto(Entry))
      return std::move(E);

    switch (Entry.Kind) {
    case BitstreamEntry::Error:
      return error("Malformed block");
    case BitstreamEntry::EndBlock:
      return false;

    case BitstreamEntry::SubBlock:
      if (Entry.ID == bitc::MODULE_BLOCK_ID)
        return hasObjCCategoryInModule(Stream);

      // Ignore other sub-blocks.
      if (Error Err = Stream.SkipBlock())
        return std::move(Err);
      continue;

    case BitstreamEntry::Record:
      if (Error E = Stream.skipRecord(Entry.ID).takeError())
        return std::move(E);
      continue;
    }
  }
}

static Expected<std::string> readModuleTriple(BitstreamCursor &Stream) {
  if (Error Err = Stream.EnterSubBlock(bitc::MODULE_BLOCK_ID))
    return std::move(Err);

  SmallVector<uint64_t, 64> Record;

  std::string Triple;

  // Read all the records for this module.
  while (true) {
    Expected<BitstreamEntry> MaybeEntry = Stream.advanceSkippingSubblocks();
    if (!MaybeEntry)
      return MaybeEntry.takeError();
    BitstreamEntry Entry = MaybeEntry.get();

    switch (Entry.Kind) {
    case BitstreamEntry::SubBlock: // Handled for us already.
    case BitstreamEntry::Error:
      return error("Malformed block");
    case BitstreamEntry::EndBlock:
      return Triple;
    case BitstreamEntry::Record:
      // The interesting case.
      break;
    }

    // Read a record.
    Expected<unsigned> MaybeRecord = Stream.readRecord(Entry.ID, Record);
    if (!MaybeRecord)
      return MaybeRecord.takeError();
    switch (MaybeRecord.get()) {
    default: break;  // Default behavior, ignore unknown content.
    case bitc::MODULE_CODE_TRIPLE: {  // TRIPLE: [strchr x N]
      std::string S;
      if (convertToString(Record, 0, S))
        return error("Invalid triple record");
      Triple = S;
      break;
    }
    }
    Record.clear();
  }
  llvm_unreachable("Exit infinite loop");
}

static Expected<std::string> readTriple(BitstreamCursor &Stream) {
  // We expect a number of well-defined blocks, though we don't necessarily
  // need to understand them all.
  while (true) {
    Expected<BitstreamEntry> MaybeEntry = Stream.advance();
    if (!MaybeEntry)
      return MaybeEntry.takeError();
    BitstreamEntry Entry = MaybeEntry.get();

    switch (Entry.Kind) {
    case BitstreamEntry::Error:
      return error("Malformed block");
    case BitstreamEntry::EndBlock:
      return "";

    case BitstreamEntry::SubBlock:
      if (Entry.ID == bitc::MODULE_BLOCK_ID)
        return readModuleTriple(Stream);

      // Ignore other sub-blocks.
      if (Error Err = Stream.SkipBlock())
        return std::move(Err);
      continue;

    case BitstreamEntry::Record:
      if (llvm::Expected<unsigned> Skipped = Stream.skipRecord(Entry.ID))
        continue;
      else
        return Skipped.takeError();
    }
  }
}

namespace {

class BitcodeReaderBase {
protected:
  BitcodeReaderBase(BitstreamCursor Stream, StringRef Strtab)
      : Stream(std::move(Stream)), Strtab(Strtab) {
    this->Stream.setBlockInfo(&BlockInfo);
  }

  BitstreamBlockInfo BlockInfo;
  BitstreamCursor Stream;
  StringRef Strtab;

  /// In version 2 of the bitcode we store names of global values and comdats in
  /// a string table rather than in the VST.
  bool UseStrtab = false;

  Expected<unsigned> parseVersionRecord(ArrayRef<uint64_t> Record);

  /// If this module uses a string table, pop the reference to the string table
  /// and return the referenced string and the rest of the record. Otherwise
  /// just return the record itself.
  std::pair<StringRef, ArrayRef<uint64_t>>
  readNameFromStrtab(ArrayRef<uint64_t> Record);

  Error readBlockInfo();

  // Contains an arbitrary and optional string identifying the bitcode producer
  std::string ProducerIdentification;

  Error error(const Twine &Message);
};

} // end anonymous namespace

Error BitcodeReaderBase::error(const Twine &Message) {
  std::string FullMsg = Message.str();
  if (!ProducerIdentification.empty())
    FullMsg += " (Producer: '" + ProducerIdentification + "' Reader: 'LLVM " +
               LLVM_VERSION_STRING "')";
  return ::error(FullMsg);
}

Expected<unsigned>
BitcodeReaderBase::parseVersionRecord(ArrayRef<uint64_t> Record) {
  if (Record.empty())
    return error("Invalid version record");
  unsigned ModuleVersion = Record[0];
  if (ModuleVersion > 2)
    return error("Invalid value");
  UseStrtab = ModuleVersion >= 2;
  return ModuleVersion;
}

std::pair<StringRef, ArrayRef<uint64_t>>
BitcodeReaderBase::readNameFromStrtab(ArrayRef<uint64_t> Record) {
  if (!UseStrtab)
    return {"", Record};
  // Invalid reference. Let the caller complain about the record being empty.
  if (Record[0] + Record[1] > Strtab.size())
    return {"", {}};
  return {StringRef(Strtab.data() + Record[0], Record[1]), Record.slice(2)};
}

namespace {

/// This represents a constant expression or constant aggregate using a custom
/// structure internal to the bitcode reader. Later, this structure will be
/// expanded by materializeValue() either into a constant expression/aggregate,
/// or into an instruction sequence at the point of use. This allows us to
/// upgrade bitcode using constant expressions even if this kind of constant
/// expression is no longer supported.
class BitcodeConstant final : public Value,
                              TrailingObjects<BitcodeConstant, unsigned> {
  friend TrailingObjects;

  // Value subclass ID: Pick largest possible value to avoid any clashes.
  static constexpr uint8_t SubclassID = 255;

public:
  // Opcodes used for non-expressions. This includes constant aggregates
  // (struct, array, vector) that might need expansion, as well as non-leaf
  // constants that don't need expansion (no_cfi, dso_local, blockaddress),
  // but still go through BitcodeConstant to avoid different uselist orders
  // between the two cases.
  static constexpr uint8_t ConstantStructOpcode = 255;
  static constexpr uint8_t ConstantArrayOpcode = 254;
  static constexpr uint8_t ConstantVectorOpcode = 253;
  static constexpr uint8_t NoCFIOpcode = 252;
  static constexpr uint8_t DSOLocalEquivalentOpcode = 251;
  static constexpr uint8_t BlockAddressOpcode = 250;
  static constexpr uint8_t ConstantPtrAuthOpcode = 249;
  static constexpr uint8_t FirstSpecialOpcode = ConstantPtrAuthOpcode;

  // Separate struct to make passing different number of parameters to
  // BitcodeConstant::create() more convenient.
  struct ExtraInfo {
    uint8_t Opcode;
    uint8_t Flags;
    unsigned BlockAddressBB = 0;
    Type *SrcElemTy = nullptr;
    std::optional<ConstantRange> InRange;

    ExtraInfo(uint8_t Opcode, uint8_t Flags = 0, Type *SrcElemTy = nullptr,
              std::optional<ConstantRange> InRange = std::nullopt)
        : Opcode(Opcode), Flags(Flags), SrcElemTy(SrcElemTy),
          InRange(std::move(InRange)) {}

    ExtraInfo(uint8_t Opcode, uint8_t Flags, unsigned BlockAddressBB)
        : Opcode(Opcode), Flags(Flags), BlockAddressBB(BlockAddressBB) {}
  };

  uint8_t Opcode;
  uint8_t Flags;
  unsigned NumOperands;
  unsigned BlockAddressBB;
  Type *SrcElemTy; // GEP source element type.
  std::optional<ConstantRange> InRange; // GEP inrange attribute.

private:
  BitcodeConstant(Type *Ty, const ExtraInfo &Info, ArrayRef<unsigned> OpIDs)
      : Value(Ty, SubclassID), Opcode(Info.Opcode), Flags(Info.Flags),
        NumOperands(OpIDs.size()), BlockAddressBB(Info.BlockAddressBB),
        SrcElemTy(Info.SrcElemTy), InRange(Info.InRange) {
    llvm::uninitialized_copy(OpIDs, getTrailingObjects());
  }

  BitcodeConstant &operator=(const BitcodeConstant &) = delete;

public:
  static BitcodeConstant *create(BumpPtrAllocator &A, Type *Ty,
                                 const ExtraInfo &Info,
                                 ArrayRef<unsigned> OpIDs) {
    void *Mem = A.Allocate(totalSizeToAlloc<unsigned>(OpIDs.size()),
                           alignof(BitcodeConstant));
    return new (Mem) BitcodeConstant(Ty, Info, OpIDs);
  }

  static bool classof(const Value *V) { return V->getValueID() == SubclassID; }

  ArrayRef<unsigned> getOperandIDs() const {
    return ArrayRef(getTrailingObjects(), NumOperands);
  }

  std::optional<ConstantRange> getInRange() const {
    assert(Opcode == Instruction::GetElementPtr);
    return InRange;
  }

  const char *getOpcodeName() const {
    return Instruction::getOpcodeName(Opcode);
  }
};

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.
  uint64_t LastFunctionBlockBit = 0;
  bool SeenValueSymbolTable = false;
  uint64_t VSTOffset = 0;

  std::vector<std::string> SectionTable;
  std::vector<std::string> GCTable;

  std::vector<Type *> TypeList;
  /// Track type IDs of contained types. Order is the same as the contained
  /// types of a Type*. This is used during upgrades of typed pointer IR in
  /// opaque pointer mode.
  DenseMap<unsigned, SmallVector<unsigned, 1>> ContainedTypeIDs;
  /// In some cases, we need to create a type ID for a type that was not
  /// explicitly encoded in the bitcode, or we don't know about at the current
  /// point. For example, a global may explicitly encode the value type ID, but
  /// not have a type ID for the pointer to value type, for which we create a
  /// virtual type ID instead. This map stores the new type ID that was created
  /// for the given pair of Type and contained type ID.
  DenseMap<std::pair<Type *, unsigned>, unsigned> VirtualTypeIDs;
  DenseMap<Function *, unsigned> FunctionTypeIDs;
  /// Allocator for BitcodeConstants. This should come before ValueList,
  /// because the ValueList might hold ValueHandles to these constants, so
  /// ValueList must be destroyed before Alloc.
  BumpPtrAllocator Alloc;
  BitcodeReaderValueList ValueList;
  std::optional<MetadataLoader> MDLoader;
  std::vector<Comdat *> ComdatList;
  DenseSet<GlobalObject *> ImplicitComdatObjects;
  SmallVector<Instruction *, 64> InstructionList;

  std::vector<std::pair<GlobalVariable *, unsigned>> GlobalInits;
  std::vector<std::pair<GlobalValue *, unsigned>> IndirectSymbolInits;

  struct FunctionOperandInfo {
    Function *F;
    unsigned PersonalityFn;
    unsigned Prefix;
    unsigned Prologue;
  };
  std::vector<FunctionOperandInfo> FunctionOperands;

  /// The set of attributes by index.  Index zero in the file is for null, and
  /// is thus not represented here.  As such all indices are off by one.
  std::vector<AttributeList> MAttributes;

  /// The set of attribute groups.
  std::map<unsigned, AttributeList> MAttributeGroups;

  /// While parsing a function body, this is a list of the basic blocks for the
  /// function.
  std::vector<BasicBlock*> FunctionBBs;

  // When reading the module header, this list is populated with functions that
  // have bodies later in the file.
  std::vector<Function*> FunctionsWithBodies;

  // When intrinsic functions are encountered which require upgrading they are
  // stored here with their replacement function.
  using UpdatedIntrinsicMap = DenseMap<Function *, Function *>;
  UpdatedIntrinsicMap UpgradedIntrinsics;

  // Several operations happen after the module header has been read, but
  // before function bodies are processed. This keeps track of whether
  // we've done this yet.
  bool SeenFirstFunctionBody = false;

  /// When function bodies are initially scanned, this map contains info about
  /// where to find deferred function body in the stream.
  DenseMap<Function*, uint64_t> DeferredFunctionInfo;

  /// When Metadata block is initially scanned when parsing the module, we may
  /// choose to defer parsing of the metadata. This vector contains info about
  /// which Metadata blocks are deferred.
  std::vector<uint64_t> DeferredMetadataInfo;

  /// These are basic blocks forward-referenced by block addresses.  They are
  /// inserted lazily into functions when they're loaded.  The basic block ID is
  /// its index into the vector.
  DenseMap<Function *, std::vector<BasicBlock *>> BasicBlockFwdRefs;
  std::deque<Function *> BasicBlockFwdRefQueue;

  /// These are Functions that contain BlockAddresses which refer a different
  /// Function. When parsing the different Function, queue Functions that refer
  /// to the different Function. Those Functions must be materialized in order
  /// to resolve their BlockAddress constants before the different Function
  /// gets moved into another Module.
  std::vector<Function *> BackwardRefFunctions;

  /// Indicates that we are using a new encoding for instruction operands where
  /// most operands in the current FUNCTION_BLOCK are encoded relative to the
  /// instruction number, for a more compact encoding.  Some instruction
  /// operands are not relative to the instruction ID: basic block numbers, and
  /// types. Once the old style function blocks have been phased out, we would
  /// not need this flag.
  bool UseRelativeIDs = false;

  /// True if all functions will be materialized, negating the need to process
  /// (e.g.) blockaddress forward references.
  bool WillMaterializeAllForwardRefs = false;

  /// Tracks whether we have seen debug intrinsics or records in this bitcode;
  /// seeing both in a single module is currently a fatal error.
  bool SeenDebugIntrinsic = false;
  bool SeenDebugRecord = false;

  bool StripDebugInfo = false;
  TBAAVerifier TBAAVerifyHelper;

  std::vector<std::string> BundleTags;
  SmallVector<SyncScope::ID, 8> SSIDs;

  std::optional<ValueTypeCallbackTy> ValueTypeCallback;

public:
  BitcodeReader(BitstreamCursor Stream, StringRef Strtab,
                StringRef ProducerIdentification, LLVMContext &Context);

  Error materializeForwardReferencedFunctions();

  Error materialize(GlobalValue *GV) override;
  Error materializeModule() override;
  std::vector<StructType *> getIdentifiedStructTypes() const override;

  /// Main interface to parsing a bitcode buffer.
  /// \returns true if an error occurred.
  Error parseBitcodeInto(Module *M, bool ShouldLazyLoadMetadata,
                         bool IsImporting, ParserCallbacks Callbacks = {});

  static uint64_t decodeSignRotatedValue(uint64_t V);

  /// Materialize any deferred Metadata block.
  Error materializeMetadata() override;

  void setStripDebugInfo() override;

private:
  std::vector<StructType *> IdentifiedStructTypes;
  StructType *createIdentifiedStructType(LLVMContext &Context, StringRef Name);
  StructType *createIdentifiedStructType(LLVMContext &Context);

  static constexpr unsigned InvalidTypeID = ~0u;

  Type *getTypeByID(unsigned ID);
  Type *getPtrElementTypeByID(unsigned ID);
  unsigned getContainedTypeID(unsigned ID, unsigned Idx = 0);
  unsigned getVirtualTypeID(Type *Ty, ArrayRef<unsigned> ContainedTypeIDs = {});

  void callValueTypeCallback(Value *F, unsigned TypeID);
  Expected<Value *> materializeValue(unsigned ValID, BasicBlock *InsertBB);
  Expected<Constant *> getValueForInitializer(unsigned ID);

  Value *getFnValueByID(unsigned ID, Type *Ty, unsigned TyID,
                        BasicBlock *ConstExprInsertBB) {
    if (Ty && Ty->isMetadataTy())
      return MetadataAsValue::get(Ty->getContext(), getFnMetadataByID(ID));
    return ValueList.getValueFwdRef(ID, Ty, TyID, ConstExprInsertBB);
  }

  Metadata *getFnMetadataByID(unsigned ID) {
    return MDLoader->getMetadataFwdRefOrLoad(ID);
  }

  BasicBlock *getBasicBlock(unsigned ID) const {
    if (ID >= FunctionBBs.size()) return nullptr; // Invalid ID
    return FunctionBBs[ID];
  }

  AttributeList getAttributes(unsigned i) const {
    if (i-1 < MAttributes.size())
      return MAttributes[i-1];
    return AttributeList();
  }

  /// Read a value/type pair out of the specified record from slot 'Slot'.
  /// Increment Slot past the number of slots used in the record. Return true on
  /// failure.
  bool getValueTypePair(const SmallVectorImpl<uint64_t> &Record, unsigned &Slot,
                        unsigned InstNum, Value *&ResVal, unsigned &TypeID,
                        BasicBlock *ConstExprInsertBB) {
    if (Slot == Record.size()) return true;
    unsigned ValNo = (unsigned)Record[Slot++];
    // Adjust the ValNo, if it was encoded relative to the InstNum.
    if (UseRelativeIDs)
      ValNo = InstNum - ValNo;
    if (ValNo < InstNum) {
      // If this is not a forward reference, just return the value we already
      // have.
      TypeID = ValueList.getTypeID(ValNo);
      ResVal = getFnValueByID(ValNo, nullptr, TypeID, ConstExprInsertBB);
      assert((!ResVal || ResVal->getType() == getTypeByID(TypeID)) &&
             "Incorrect type ID stored for value");
      return ResVal == nullptr;
    }
    if (Slot == Record.size())
      return true;

    TypeID = (unsigned)Record[Slot++];
    ResVal = getFnValueByID(ValNo, getTypeByID(TypeID), TypeID,
                            ConstExprInsertBB);
    return ResVal == nullptr;
  }

  bool getValueOrMetadata(const SmallVectorImpl<uint64_t> &Record,
                          unsigned &Slot, unsigned InstNum, Value *&ResVal,
                          BasicBlock *ConstExprInsertBB) {
    if (Slot == Record.size())
      return true;
    unsigned ValID = Record[Slot++];
    if (ValID != static_cast<unsigned>(bitc::OB_METADATA)) {
      unsigned TypeId;
      return getValueTypePair(Record, --Slot, InstNum, ResVal, TypeId,
                              ConstExprInsertBB);
    }
    if (Slot == Record.size())
      return true;
    unsigned ValNo = InstNum - (unsigned)Record[Slot++];
    ResVal = MetadataAsValue::get(Context, getFnMetadataByID(ValNo));
    return false;
  }

  /// Read a value out of the specified record from slot 'Slot'. Increment Slot
  /// past the number of slots used by the value in the record. Return true if
  /// there is an error.
  bool popValue(const SmallVectorImpl<uint64_t> &Record, unsigned &Slot,
                unsigned InstNum, Type *Ty, unsigned TyID, Value *&ResVal,
                BasicBlock *ConstExprInsertBB) {
    if (getValue(Record, Slot, InstNum, Ty, TyID, ResVal, ConstExprInsertBB))
      return true;
    // All values currently take a single record slot.
    ++Slot;
    return false;
  }

  /// Like popValue, but does not increment the Slot number.
  bool getValue(const SmallVectorImpl<uint64_t> &Record, unsigned Slot,
                unsigned InstNum, Type *Ty, unsigned TyID, Value *&ResVal,
                BasicBlock *ConstExprInsertBB) {
    ResVal = getValue(Record, Slot, InstNum, Ty, TyID, ConstExprInsertBB);
    return ResVal == nullptr;
  }

  /// Version of getValue that returns ResVal directly, or 0 if there is an
  /// error.
  Value *getValue(const SmallVectorImpl<uint64_t> &Record, unsigned Slot,
                  unsigned InstNum, Type *Ty, unsigned TyID,
                  BasicBlock *ConstExprInsertBB) {
    if (Slot == Record.size()) return nullptr;
    unsigned ValNo = (unsigned)Record[Slot];
    // Adjust the ValNo, if it was encoded relative to the InstNum.
    if (UseRelativeIDs)
      ValNo = InstNum - ValNo;
    return getFnValueByID(ValNo, Ty, TyID, ConstExprInsertBB);
  }

  /// Like getValue, but decodes signed VBRs.
  Value *getValueSigned(const SmallVectorImpl<uint64_t> &Record, unsigned Slot,
                        unsigned InstNum, Type *Ty, unsigned TyID,
                        BasicBlock *ConstExprInsertBB) {
    if (Slot == Record.size()) return nullptr;
    unsigned ValNo = (unsigned)decodeSignRotatedValue(Record[Slot]);
    // Adjust the ValNo, if it was encoded relative to the InstNum.
    if (UseRelativeIDs)
      ValNo = InstNum - ValNo;
    return getFnValueByID(ValNo, Ty, TyID, ConstExprInsertBB);
  }

  Expected<ConstantRange> readConstantRange(ArrayRef<uint64_t> Record,
                                            unsigned &OpNum,
                                            unsigned BitWidth) {
    if (Record.size() - OpNum < 2)
      return error("Too few records for range");
    if (BitWidth > 64) {
      unsigned LowerActiveWords = Record[OpNum];
      unsigned UpperActiveWords = Record[OpNum++] >> 32;
      if (Record.size() - OpNum < LowerActiveWords + UpperActiveWords)
        return error("Too few records for range");
      APInt Lower =
          readWideAPInt(ArrayRef(&Record[OpNum], LowerActiveWords), BitWidth);
      OpNum += LowerActiveWords;
      APInt Upper =
          readWideAPInt(ArrayRef(&Record[OpNum], UpperActiveWords), BitWidth);
      OpNum += UpperActiveWords;
      return ConstantRange(Lower, Upper);
    } else {
      int64_t Start = BitcodeReader::decodeSignRotatedValue(Record[OpNum++]);
      int64_t End = BitcodeReader::decodeSignRotatedValue(Record[OpNum++]);
      return ConstantRange(APInt(BitWidth, Start, true),
                           APInt(BitWidth, End, true));
    }
  }

  Expected<ConstantRange>
  readBitWidthAndConstantRange(ArrayRef<uint64_t> Record, unsigned &OpNum) {
    if (Record.size() - OpNum < 1)
      return error("Too few records for range");
    unsigned BitWidth = Record[OpNum++];
    return readConstantRange(Record, OpNum, BitWidth);
  }

  /// Upgrades old-style typeless byval/sret/inalloca attributes by adding the
  /// corresponding argument's pointee type. Also upgrades intrinsics that now
  /// require an elementtype attribute.
  Error propagateAttributeTypes(CallBase *CB, ArrayRef<unsigned> ArgsTys);

  /// 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.
  Error parseAlignmentValue(uint64_t Exponent, MaybeAlign &Alignment);
  Error parseAttrKind(uint64_t Code, Attribute::AttrKind *Kind);
  Error parseModule(uint64_t ResumeBit, bool ShouldLazyLoadMetadata = false,
                    ParserCallbacks Callbacks = {});

  Error parseComdatRecord(ArrayRef<uint64_t> Record);
  Error parseGlobalVarRecord(ArrayRef<uint64_t> Record);
  Error parseFunctionRecord(ArrayRef<uint64_t> Record);
  Error parseGlobalIndirectSymbolRecord(unsigned BitCode,
                                        ArrayRef<uint64_t> Record);

  Error parseAttributeBlock();
  Error parseAttributeGroupBlock();
  Error parseTypeTable();
  Error parseTypeTableBody();
  Error parseOperandBundleTags();
  Error parseSyncScopeNames();

  Expected<Value *> recordValue(SmallVectorImpl<uint64_t> &Record,
                                unsigned NameIndex, Triple &TT);
  void setDeferredFunctionInfo(unsigned FuncBitcodeOffsetDelta, Function *F,
                               ArrayRef<uint64_t> Record);
  Error parseValueSymbolTable(uint64_t Offset = 0);
  Error parseGlobalValueSymbolTable();
  Error parseConstants();
  Error rememberAndSkipFunctionBodies();
  Error rememberAndSkipFunctionBody();
  /// Save the positions of the Metadata blocks and skip parsing the blocks.
  Error rememberAndSkipMetadata();
  Error typeCheckLoadStoreInst(Type *ValType, Type *PtrType);
  Error parseFunctionBody(Function *F);
  Error globalCleanup();
  Error resolveGlobalAndIndirectSymbolInits();
  Error parseUseLists();
  Error findFunctionInStream(
      Function *F,
      DenseMap<Function *, uint64_t>::iterator DeferredFunctionInfoIterator);

  SyncScope::ID getDecodedSyncScopeID(unsigned Val);
};

/// Class to manage reading and parsing function summary index bitcode
/// files/sections.
class ModuleSummaryIndexBitcodeReader : public BitcodeReaderBase {
  /// The module index built during parsing.
  ModuleSummaryIndex &TheIndex;

  /// Indicates whether we have encountered a global value summary section
  /// yet during parsing.
  bool SeenGlobalValSummary = false;

  /// Indicates whether we have already parsed the VST, used for error checking.
  bool SeenValueSymbolTable = false;

  /// Set to the offset of the VST recorded in the MODULE_CODE_VSTOFFSET record.
  /// Used to enable on-demand parsing of the VST.
  uint64_t VSTOffset = 0;

  // Map to save ValueId to ValueInfo association that was recorded in the
  // ValueSymbolTable. It is used after the VST is parsed to convert
  // call graph edges read from the function summary from referencing
  // callees by their ValueId to using the ValueInfo instead, which is how
  // they are recorded in the summary index being built.
  // We save a GUID which refers to the same global as the ValueInfo, but
  // ignoring the linkage, i.e. for values other than local linkage they are
  // identical (this is the second member). ValueInfo has the real GUID.
  DenseMap<unsigned, std::pair<ValueInfo, GlobalValue::GUID>>
      ValueIdToValueInfoMap;

  /// Map populated during module path string table parsing, from the
  /// module ID to a string reference owned by the index's module
  /// 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;

  /// The string identifier given to this module by the client, normally the
  /// path to the bitcode file.
  StringRef ModulePath;

  /// Callback to ask whether a symbol is the prevailing copy when invoked
  /// during combined index building.
  std::function<bool(GlobalValue::GUID)> IsPrevailing;

  /// Saves the stack ids from the STACK_IDS record to consult when adding stack
  /// ids from the lists in the callsite and alloc entries to the index.
  std::vector<uint64_t> StackIds;

  /// Linearized radix tree of allocation contexts. See the description above
  /// the CallStackRadixTreeBuilder class in ProfileData/MemProf.h for format.
  std::vector<uint64_t> RadixArray;

public:
  ModuleSummaryIndexBitcodeReader(
      BitstreamCursor Stream, StringRef Strtab, ModuleSummaryIndex &TheIndex,
      StringRef ModulePath,
      std::function<bool(GlobalValue::GUID)> IsPrevailing = nullptr);

  Error parseModule();

private:
  void setValueGUID(uint64_t ValueID, StringRef ValueName,
                    GlobalValue::LinkageTypes Linkage,
                    StringRef SourceFileName);
  Error parseValueSymbolTable(
      uint64_t Offset,
      DenseMap<unsigned, GlobalValue::LinkageTypes> &ValueIdToLinkageMap);
  SmallVector<ValueInfo, 0> makeRefList(ArrayRef<uint64_t> Record);
  SmallVector<FunctionSummary::EdgeTy, 0>
  makeCallList(ArrayRef<uint64_t> Record, bool IsOldProfileFormat,
               bool HasProfile, bool HasRelBF);
  Error parseEntireSummary(unsigned ID);
  Error parseModuleStringTable();
  void parseTypeIdCompatibleVtableSummaryRecord(ArrayRef<uint64_t> Record);
  void parseTypeIdCompatibleVtableInfo(ArrayRef<uint64_t> Record, size_t &Slot,
                                       TypeIdCompatibleVtableInfo &TypeId);
  std::vector<FunctionSummary::ParamAccess>
  parseParamAccesses(ArrayRef<uint64_t> Record);
  SmallVector<unsigned> parseAllocInfoContext(ArrayRef<uint64_t> Record,
                                              unsigned &I);

  template <bool AllowNullValueInfo = false>
  std::pair<ValueInfo, GlobalValue::GUID>
  getValueInfoFromValueId(unsigned ValueId);

  void addThisModule();
  ModuleSummaryIndex::ModuleInfo *getThisModule();
};

} // end anonymous namespace

std::error_code llvm::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;
  }
  return std::error_code();
}

BitcodeReader::BitcodeReader(BitstreamCursor Stream, StringRef Strtab,
                             StringRef ProducerIdentification,
                             LLVMContext &Context)
    : BitcodeReaderBase(std::move(Stream), Strtab), Context(Context),
      ValueList(this->Stream.SizeInBytes(),
                [this](unsigned ValID, BasicBlock *InsertBB) {
                  return materializeValue(ValID, InsertBB);
                }) {
  this->ProducerIdentification = std::string(ProducerIdentification);
}

Error BitcodeReader::materializeForwardReferencedFunctions() {
  if (WillMaterializeAllForwardRefs)
    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 (Error Err = materialize(F))
      return Err;
  }
  assert(BasicBlockFwdRefs.empty() && "Function missing from queue");

  for (Function *F : BackwardRefFunctions)
    if (Error Err = materialize(F))
      return Err;
  BackwardRefFunctions.clear();

  // Reset state.
  WillMaterializeAllForwardRefs = false;
  return Error::success();
}

//===----------------------------------------------------------------------===//
//  Helper functions to implement forward reference resolution, etc.
//===----------------------------------------------------------------------===//

static bool hasImplicitComdat(size_t Val) {
  switch (Val) {
  default:
    return false;
  case 1:  // Old WeakAnyLinkage
  case 4:  // Old LinkOnceAnyLinkage
  case 10: // Old WeakODRLinkage
  case 11: // Old LinkOnceODRLinkage
    return true;
  }
}

static GlobalValue::LinkageTypes getDecodedLinkage(unsigned Val) {
  switch (Val) {
  default: // Map unknown/new linkages to external
  case 0:
    return GlobalValue::ExternalLinkage;
  case 2:
    return GlobalValue::AppendingLinkage;
  case 3:
    return GlobalValue::InternalLinkage;
  case 5:
    return GlobalValue::ExternalLinkage; // Obsolete DLLImportLinkage
  case 6:
    return GlobalValue::ExternalLinkage; // Obsolete DLLExportLinkage
  case 7:
    return GlobalValue::ExternalWeakLinkage;
  case 8:
    return GlobalValue::CommonLinkage;
  case 9:
    return GlobalValue::PrivateLinkage;
  case 12:
    return GlobalValue::AvailableExternallyLinkage;
  case 13:
    return GlobalValue::PrivateLinkage; // Obsolete LinkerPrivateLinkage
  case 14:
    return GlobalValue::PrivateLinkage; // Obsolete LinkerPrivateWeakLinkage
  case 15:
    return GlobalValue::ExternalLinkage; // Obsolete LinkOnceODRAutoHideLinkage
  case 1: // Old value with implicit comdat.
  case 16:
    return GlobalValue::WeakAnyLinkage;
  case 10: // Old value with implicit comdat.
  case 17:
    return GlobalValue::WeakODRLinkage;
  case 4: // Old value with implicit comdat.
  case 18:
    return GlobalValue::LinkOnceAnyLinkage;
  case 11: // Old value with implicit comdat.
  case 19:
    return GlobalValue::LinkOnceODRLinkage;
  }
}

static FunctionSummary::FFlags getDecodedFFlags(uint64_t RawFlags) {
  FunctionSummary::FFlags Flags;
  Flags.ReadNone = RawFlags & 0x1;
  Flags.ReadOnly = (RawFlags >> 1) & 0x1;
  Flags.NoRecurse = (RawFlags >> 2) & 0x1;
  Flags.ReturnDoesNotAlias = (RawFlags >> 3) & 0x1;
  Flags.NoInline = (RawFlags >> 4) & 0x1;
  Flags.AlwaysInline = (RawFlags >> 5) & 0x1;
  Flags.NoUnwind = (RawFlags >> 6) & 0x1;
  Flags.MayThrow = (RawFlags >> 7) & 0x1;
  Flags.HasUnknownCall = (RawFlags >> 8) & 0x1;
  Flags.MustBeUnreachable = (RawFlags >> 9) & 0x1;
  return Flags;
}

// Decode the flags for GlobalValue in the summary. The bits for each attribute:
//
// linkage: [0,4), notEligibleToImport: 4, live: 5, local: 6, canAutoHide: 7,
// visibility: [8, 10).
static GlobalValueSummary::GVFlags getDecodedGVSummaryFlags(uint64_t RawFlags,
                                                            uint64_t Version) {
  // Summary were not emitted before LLVM 3.9, we don't need to upgrade Linkage
  // like getDecodedLinkage() above. Any future change to the linkage enum and
  // to getDecodedLinkage() will need to be taken into account here as above.
  auto Linkage = GlobalValue::LinkageTypes(RawFlags & 0xF); // 4 bits
  auto Visibility = GlobalValue::VisibilityTypes((RawFlags >> 8) & 3); // 2 bits
  auto IK = GlobalValueSummary::ImportKind((RawFlags >> 10) & 1);      // 1 bit
  RawFlags = RawFlags >> 4;
  bool NotEligibleToImport = (RawFlags & 0x1) || Version < 3;
  // The Live flag wasn't introduced until version 3. For dead stripping
  // to work correctly on earlier versions, we must conservatively treat all
  // values as live.
  bool Live = (RawFlags & 0x2) || Version < 3;
  bool Local = (RawFlags & 0x4);
  bool AutoHide = (RawFlags & 0x8);

  return GlobalValueSummary::GVFlags(Linkage, Visibility, NotEligibleToImport,
                                     Live, Local, AutoHide, IK);
}

// Decode the flags for GlobalVariable in the summary
static GlobalVarSummary::GVarFlags getDecodedGVarFlags(uint64_t RawFlags) {
  return GlobalVarSummary::GVarFlags(
      (RawFlags & 0x1) ? true : false, (RawFlags & 0x2) ? true : false,
      (RawFlags & 0x4) ? true : false,
      (GlobalObject::VCallVisibility)(RawFlags >> 3));
}

static std::pair<CalleeInfo::HotnessType, bool>
getDecodedHotnessCallEdgeInfo(uint64_t RawFlags) {
  CalleeInfo::HotnessType Hotness =
      static_cast<CalleeInfo::HotnessType>(RawFlags & 0x7); // 3 bits
  bool HasTailCall = (RawFlags & 0x8);                      // 1 bit
  return {Hotness, HasTailCall};
}

static void getDecodedRelBFCallEdgeInfo(uint64_t RawFlags, uint64_t &RelBF,
                                        bool &HasTailCall) {
  static constexpr uint64_t RelBlockFreqMask =
      (1 << CalleeInfo::RelBlockFreqBits) - 1;
  RelBF = RawFlags & RelBlockFreqMask; // RelBlockFreqBits bits
  HasTailCall = (RawFlags & (1 << CalleeInfo::RelBlockFreqBits)); // 1 bit
}

static GlobalValue::VisibilityTypes getDecodedVisibility(unsigned Val) {
  switch (Val) {
  default: // Map unknown visibilities to default.
  case 0: return GlobalValue::DefaultVisibility;
  case 1: return GlobalValue::HiddenVisibility;
  case 2: return GlobalValue::ProtectedVisibility;
  }
}

static GlobalValue::DLLStorageClassTypes
getDecodedDLLStorageClass(unsigned Val) {
  switch (Val) {
  default: // Map unknown values to default.
  case 0: return GlobalValue::DefaultStorageClass;
  case 1: return GlobalValue::DLLImportStorageClass;
  case 2: return GlobalValue::DLLExportStorageClass;
  }
}

static bool getDecodedDSOLocal(unsigned Val) {
  switch(Val) {
  default: // Map unknown values to preemptable.
  case 0:  return false;
  case 1:  return true;
  }
}

static std::optional<CodeModel::Model> getDecodedCodeModel(unsigned Val) {
  switch (Val) {
  case 1:
    return CodeModel::Tiny;
  case 2:
    return CodeModel::Small;
  case 3:
    return CodeModel::Kernel;
  case 4:
    return CodeModel::Medium;
  case 5:
    return CodeModel::Large;
  }

  return {};
}

static GlobalVariable::ThreadLocalMode getDecodedThreadLocalMode(unsigned Val) {
  switch (Val) {
    case 0: return GlobalVariable::NotThreadLocal;
    default: // Map unknown non-zero value to general dynamic.
    case 1: return GlobalVariable::GeneralDynamicTLSModel;
    case 2: return GlobalVariable::LocalDynamicTLSModel;
    case 3: return GlobalVariable::InitialExecTLSModel;
    case 4: return GlobalVariable::LocalExecTLSModel;
  }
}

static GlobalVariable::UnnamedAddr getDecodedUnnamedAddrType(unsigned Val) {
  switch (Val) {
    default: // Map unknown to UnnamedAddr::None.
    case 0: return GlobalVariable::UnnamedAddr::None;
    case 1: return GlobalVariable::UnnamedAddr::Global;
    case 2: return GlobalVariable::UnnamedAddr::Local;
  }
}

static int getDecodedCastOpcode(unsigned Val) {
  switch (Val) {
  default: return -1;
  case bitc::CAST_TRUNC   : return Instruction::Trunc;
  case bitc::CAST_ZEXT    : return Instruction::ZExt;
  case bitc::CAST_SEXT    : return Instruction::SExt;
  case bitc::CAST_FPTOUI  : return Instruction::FPToUI;
  case bitc::CAST_FPTOSI  : return Instruction::FPToSI;
  case bitc::CAST_UITOFP  : return Instruction::UIToFP;
  case bitc::CAST_SITOFP  : return Instruction::SIToFP;
  case bitc::CAST_FPTRUNC : return Instruction::FPTrunc;
  case bitc::CAST_FPEXT   : return Instruction::FPExt;
  case bitc::CAST_PTRTOINT: return Instruction::PtrToInt;
  case bitc::CAST_INTTOPTR: return Instruction::IntToPtr;
  case bitc::CAST_BITCAST : return Instruction::BitCast;
  case bitc::CAST_ADDRSPACECAST: return Instruction::AddrSpaceCast;
  }
}

static int getDecodedUnaryOpcode(unsigned Val, Type *Ty) {
  bool IsFP = Ty->isFPOrFPVectorTy();
  // UnOps are only valid for int/fp or vector of int/fp types
  if (!IsFP && !Ty->isIntOrIntVectorTy())
    return -1;

  switch (Val) {
  default:
    return -1;
  case bitc::UNOP_FNEG:
    return IsFP ? Instruction::FNeg : -1;
  }
}

static int getDecodedBinaryOpcode(unsigned Val, Type *Ty) {
  bool IsFP = Ty->isFPOrFPVectorTy();
  // BinOps are only valid for int/fp or vector of int/fp types
  if (!IsFP && !Ty->isIntOrIntVectorTy())
    return -1;

  switch (Val) {
  default:
    return -1;
  case bitc::BINOP_ADD:
    return IsFP ? Instruction::FAdd : Instruction::Add;
  case bitc::BINOP_SUB:
    return IsFP ? Instruction::FSub : Instruction::Sub;
  case bitc::BINOP_MUL:
    return IsFP ? Instruction::FMul : Instruction::Mul;
  case bitc::BINOP_UDIV:
    return IsFP ? -1 : Instruction::UDiv;
  case bitc::BINOP_SDIV:
    return IsFP ? Instruction::FDiv : Instruction::SDiv;
  case bitc::BINOP_UREM:
    return IsFP ? -1 : Instruction::URem;
  case bitc::BINOP_SREM:
    return IsFP ? Instruction::FRem : Instruction::SRem;
  case bitc::BINOP_SHL:
    return IsFP ? -1 : Instruction::Shl;
  case bitc::BINOP_LSHR:
    return IsFP ? -1 : Instruction::LShr;
  case bitc::BINOP_ASHR:
    return IsFP ? -1 : Instruction::AShr;
  case bitc::BINOP_AND:
    return IsFP ? -1 : Instruction::And;
  case bitc::BINOP_OR:
    return IsFP ? -1 : Instruction::Or;
  case bitc::BINOP_XOR:
    return IsFP ? -1 : Instruction::Xor;
  }
}

static AtomicRMWInst::BinOp getDecodedRMWOperation(unsigned Val) {
  switch (Val) {
  default: return AtomicRMWInst::BAD_BINOP;
  case bitc::RMW_XCHG: return AtomicRMWInst::Xchg;
  case bitc::RMW_ADD: return AtomicRMWInst::Add;
  case bitc::RMW_SUB: return AtomicRMWInst::Sub;
  case bitc::RMW_AND: return AtomicRMWInst::And;
  case bitc::RMW_NAND: return AtomicRMWInst::Nand;
  case bitc::RMW_OR: return AtomicRMWInst::Or;
  case bitc::RMW_XOR: return AtomicRMWInst::Xor;
  case bitc::RMW_MAX: return AtomicRMWInst::Max;
  case bitc::RMW_MIN: return AtomicRMWInst::Min;
  case bitc::RMW_UMAX: return AtomicRMWInst::UMax;
  case bitc::RMW_UMIN: return AtomicRMWInst::UMin;
  case bitc::RMW_FADD: return AtomicRMWInst::FAdd;
  case bitc::RMW_FSUB: return AtomicRMWInst::FSub;
  case bitc::RMW_FMAX: return AtomicRMWInst::FMax;
  case bitc::RMW_FMIN: return AtomicRMWInst::FMin;
  case bitc::RMW_FMAXIMUM:
    return AtomicRMWInst::FMaximum;
  case bitc::RMW_FMINIMUM:
    return AtomicRMWInst::FMinimum;
  case bitc::RMW_UINC_WRAP:
    return AtomicRMWInst::UIncWrap;
  case bitc::RMW_UDEC_WRAP:
    return AtomicRMWInst::UDecWrap;
  case bitc::RMW_USUB_COND:
    return AtomicRMWInst::USubCond;
  case bitc::RMW_USUB_SAT:
    return AtomicRMWInst::USubSat;
  }
}

static AtomicOrdering getDecodedOrdering(unsigned Val) {
  switch (Val) {
  case bitc::ORDERING_NOTATOMIC: return AtomicOrdering::NotAtomic;
  case bitc::ORDERING_UNORDERED: return AtomicOrdering::Unordered;
  case bitc::ORDERING_MONOTONIC: return AtomicOrdering::Monotonic;
  case bitc::ORDERING_ACQUIRE: return AtomicOrdering::Acquire;
  case bitc::ORDERING_RELEASE: return AtomicOrdering::Release;
  case bitc::ORDERING_ACQREL: return AtomicOrdering::AcquireRelease;
  default: // Map unknown orderings to sequentially-consistent.
  case bitc::ORDERING_SEQCST: return AtomicOrdering::SequentiallyConsistent;
  }
}

static Comdat::SelectionKind getDecodedComdatSelectionKind(unsigned Val) {
  switch (Val) {
  default: // Map unknown selection kinds to any.
  case bitc::COMDAT_SELECTION_KIND_ANY:
    return Comdat::Any;
  case bitc::COMDAT_SELECTION_KIND_EXACT_MATCH:
    return Comdat::ExactMatch;
  case bitc::COMDAT_SELECTION_KIND_LARGEST:
    return Comdat::Largest;
  case bitc::COMDAT_SELECTION_KIND_NO_DUPLICATES:
    return Comdat::NoDeduplicate;
  case bitc::COMDAT_SELECTION_KIND_SAME_SIZE:
    return Comdat::SameSize;
  }
}

static FastMathFlags getDecodedFastMathFlags(unsigned Val) {
  FastMathFlags FMF;
  if (0 != (Val & bitc::UnsafeAlgebra))
    FMF.setFast();
  if (0 != (Val & bitc::AllowReassoc))
    FMF.setAllowReassoc();
  if (0 != (Val & bitc::NoNaNs))
    FMF.setNoNaNs();
  if (0 != (Val & bitc::NoInfs))
    FMF.setNoInfs();
  if (0 != (Val & bitc::NoSignedZeros))
    FMF.setNoSignedZeros();
  if (0 != (Val & bitc::AllowReciprocal))
    FMF.setAllowReciprocal();
  if (0 != (Val & bitc::AllowContract))
    FMF.setAllowContract(true);
  if (0 != (Val & bitc::ApproxFunc))
    FMF.setApproxFunc();
  return FMF;
}

static void upgradeDLLImportExportLinkage(GlobalValue *GV, unsigned Val) {
  // A GlobalValue with local linkage cannot have a DLL storage class.
  if (GV->hasLocalLinkage())
    return;
  switch (Val) {
  case 5: GV->setDLLStorageClass(GlobalValue::DLLImportStorageClass); break;
  case 6: GV->setDLLStorageClass(GlobalValue::DLLExportStorageClass); break;
  }
}

Type *BitcodeReader::getTypeByID(unsigned ID) {
  // The type table size is always specified correctly.
  if (ID >= TypeList.size())
    return nullptr;

  if (Type *Ty = TypeList[ID])
    return Ty;

  // If we have a forward reference, the only possible case is when it is to a
  // named struct.  Just create a placeholder for now.
  return TypeList[ID] = createIdentifiedStructType(Context);
}

unsigned BitcodeReader::getContainedTypeID(unsigned ID, unsigned Idx) {
  auto It = ContainedTypeIDs.find(ID);
  if (It == ContainedTypeIDs.end())
    return InvalidTypeID;

  if (Idx >= It->second.size())
    return InvalidTypeID;

  return It->second[Idx];
}

Type *BitcodeReader::getPtrElementTypeByID(unsigned ID) {
  if (ID >= TypeList.size())
    return nullptr;

  Type *Ty = TypeList[ID];
  if (!Ty->isPointerTy())
    return nullptr;

  return getTypeByID(getContainedTypeID(ID, 0));
}

unsigned BitcodeReader::getVirtualTypeID(Type *Ty,
                                         ArrayRef<unsigned> ChildTypeIDs) {
  unsigned ChildTypeID = ChildTypeIDs.empty() ? InvalidTypeID : ChildTypeIDs[0];
  auto CacheKey = std::make_pair(Ty, ChildTypeID);
  auto It = VirtualTypeIDs.find(CacheKey);
  if (It != VirtualTypeIDs.end()) {
    // The cmpxchg return value is the only place we need more than one
    // contained type ID, however the second one will always be the same (i1),
    // so we don't need to include it in the cache key. This asserts that the
    // contained types are indeed as expected and there are no collisions.
    assert((ChildTypeIDs.empty() ||
            ContainedTypeIDs[It->second] == ChildTypeIDs) &&
           "Incorrect cached contained type IDs");
    return It->second;
  }

  unsigned TypeID = TypeList.size();
  TypeList.push_back(Ty);
  if (!ChildTypeIDs.empty())
    append_range(ContainedTypeIDs[TypeID], ChildTypeIDs);
  VirtualTypeIDs.insert({CacheKey, TypeID});
  return TypeID;
}

static GEPNoWrapFlags toGEPNoWrapFlags(uint64_t Flags) {
  GEPNoWrapFlags NW;
  if (Flags & (1 << bitc::GEP_INBOUNDS))
    NW |= GEPNoWrapFlags::inBounds();
  if (Flags & (1 << bitc::GEP_NUSW))
    NW |= GEPNoWrapFlags::noUnsignedSignedWrap();
  if (Flags & (1 << bitc::GEP_NUW))
    NW |= GEPNoWrapFlags::noUnsignedWrap();
  return NW;
}

static bool isConstExprSupported(const BitcodeConstant *BC) {
  uint8_t Opcode = BC->Opcode;

  // These are not real constant expressions, always consider them supported.
  if (Opcode >= BitcodeConstant::FirstSpecialOpcode)
    return true;

  // If -expand-constant-exprs is set, we want to consider all expressions
  // as unsupported.
  if (ExpandConstantExprs)
    return false;

  if (Instruction::isBinaryOp(Opcode))
    return ConstantExpr::isSupportedBinOp(Opcode);

  if (Instruction::isCast(Opcode))
    return ConstantExpr::isSupportedCastOp(Opcode);

  if (Opcode == Instruction::GetElementPtr)
    return ConstantExpr::isSupportedGetElementPtr(BC->SrcElemTy);

  switch (Opcode) {
  case Instruction::FNeg:
  case Instruction::Select:
  case Instruction::ICmp:
  case Instruction::FCmp:
    return false;
  default:
    return true;
  }
}

Expected<Value *> BitcodeReader::materializeValue(unsigned StartValID,
                                                  BasicBlock *InsertBB) {
  // Quickly handle the case where there is no BitcodeConstant to resolve.
  if (StartValID < ValueList.size() && ValueList[StartValID] &&
      !isa<BitcodeConstant>(ValueList[StartValID]))
    return ValueList[StartValID];

  SmallDenseMap<unsigned, Value *> MaterializedValues;
  SmallVector<unsigned> Worklist;
  Worklist.push_back(StartValID);
  while (!Worklist.empty()) {
    unsigned ValID = Worklist.back();
    if (MaterializedValues.count(ValID)) {
      // Duplicate expression that was already handled.
      Worklist.pop_back();
      continue;
    }

    if (ValID >= ValueList.size() || !ValueList[ValID])
      return error("Invalid value ID");

    Value *V = ValueList[ValID];
    auto *BC = dyn_cast<BitcodeConstant>(V);
    if (!BC) {
      MaterializedValues.insert({ValID, V});
      Worklist.pop_back();
      continue;
    }

    // Iterate in reverse, so values will get popped from the worklist in
    // expected order.
    SmallVector<Value *> Ops;
    for (unsigned OpID : reverse(BC->getOperandIDs())) {
      auto It = MaterializedValues.find(OpID);
      if (It != MaterializedValues.end())
        Ops.push_back(It->second);
      else
        Worklist.push_back(OpID);
    }

    // Some expressions have not been resolved yet, handle them first and then
    // revisit this one.
    if (Ops.size() != BC->getOperandIDs().size())
      continue;
    std::reverse(Ops.begin(), Ops.end());

    SmallVector<Constant *> ConstOps;
    for (Value *Op : Ops)
      if (auto *C = dyn_cast<Constant>(Op))
        ConstOps.push_back(C);

    // Materialize as constant expression if possible.
    if (isConstExprSupported(BC) && ConstOps.size() == Ops.size()) {
      Constant *C;
      if (Instruction::isCast(BC->Opcode)) {
        C = UpgradeBitCastExpr(BC->Opcode, ConstOps[0], BC->getType());
        if (!C)
          C = ConstantExpr::getCast(BC->Opcode, ConstOps[0], BC->getType());
      } else if (Instruction::isBinaryOp(BC->Opcode)) {
        C = ConstantExpr::get(BC->Opcode, ConstOps[0], ConstOps[1], BC->Flags);
      } else {
        switch (BC->Opcode) {
        case BitcodeConstant::ConstantPtrAuthOpcode: {
          auto *Key = dyn_cast<ConstantInt>(ConstOps[1]);
          if (!Key)
            return error("ptrauth key operand must be ConstantInt");

          auto *Disc = dyn_cast<ConstantInt>(ConstOps[2]);
          if (!Disc)
            return error("ptrauth disc operand must be ConstantInt");

          C = ConstantPtrAuth::get(ConstOps[0], Key, Disc, ConstOps[3]);
          break;
        }
        case BitcodeConstant::NoCFIOpcode: {
          auto *GV = dyn_cast<GlobalValue>(ConstOps[0]);
          if (!GV)
            return error("no_cfi operand must be GlobalValue");
          C = NoCFIValue::get(GV);
          break;
        }
        case BitcodeConstant::DSOLocalEquivalentOpcode: {
          auto *GV = dyn_cast<GlobalValue>(ConstOps[0]);
          if (!GV)
            return error("dso_local operand must be GlobalValue");
          C = DSOLocalEquivalent::get(GV);
          break;
        }
        case BitcodeConstant::BlockAddressOpcode: {
          Function *Fn = dyn_cast<Function>(ConstOps[0]);
          if (!Fn)
            return error("blockaddress operand must be a function");

          // If the function is already parsed we can insert the block address
          // right away.
          BasicBlock *BB;
          unsigned BBID = BC->BlockAddressBB;
          if (!BBID)
            // Invalid reference to entry block.
            return error("Invalid ID");
          if (!Fn->empty()) {
            Function::iterator BBI = Fn->begin(), BBE = Fn->end();
            for (size_t I = 0, E = BBID; I != E; ++I) {
              if (BBI == BBE)
                return error("Invalid ID");
              ++BBI;
            }
            BB = &*BBI;
          } else {
            // Otherwise insert a placeholder and remember it so it can be
            // inserted when the function is parsed.
            auto &FwdBBs = BasicBlockFwdRefs[Fn];
            if (FwdBBs.empty())
              BasicBlockFwdRefQueue.push_back(Fn);
            if (FwdBBs.size() < BBID + 1)
              FwdBBs.resize(BBID + 1);
            if (!FwdBBs[BBID])
              FwdBBs[BBID] = BasicBlock::Create(Context);
            BB = FwdBBs[BBID];
          }
          C = BlockAddress::get(Fn->getType(), BB);
          break;
        }
        case BitcodeConstant::ConstantStructOpcode: {
          auto *ST = cast<StructType>(BC->getType());
          if (ST->getNumElements() != ConstOps.size())
            return error("Invalid number of elements in struct initializer");

          for (const auto [Ty, Op] : zip(ST->elements(), ConstOps))
            if (Op->getType() != Ty)
              return error("Incorrect type in struct initializer");

          C = ConstantStruct::get(ST, ConstOps);
          break;
        }
        case BitcodeConstant::ConstantArrayOpcode: {
          auto *AT = cast<ArrayType>(BC->getType());
          if (AT->getNumElements() != ConstOps.size())
            return error("Invalid number of elements in array initializer");

          for (Constant *Op : ConstOps)
            if (Op->getType() != AT->getElementType())
              return error("Incorrect type in array initializer");

          C = ConstantArray::get(AT, ConstOps);
          break;
        }
        case BitcodeConstant::ConstantVectorOpcode: {
          auto *VT = cast<FixedVectorType>(BC->getType());
          if (VT->getNumElements() != ConstOps.size())
            return error("Invalid number of elements in vector initializer");

          for (Constant *Op : ConstOps)
            if (Op->getType() != VT->getElementType())
              return error("Incorrect type in vector initializer");

          C = ConstantVector::get(ConstOps);
          break;
        }
        case Instruction::GetElementPtr:
          C = ConstantExpr::getGetElementPtr(
              BC->SrcElemTy, ConstOps[0], ArrayRef(ConstOps).drop_front(),
              toGEPNoWrapFlags(BC->Flags), BC->getInRange());
          break;
        case Instruction::ExtractElement:
          C = ConstantExpr::getExtractElement(ConstOps[0], ConstOps[1]);
          break;
        case Instruction::InsertElement:
          C = ConstantExpr::getInsertElement(ConstOps[0], ConstOps[1],
                                             ConstOps[2]);
          break;
        case Instruction::ShuffleVector: {
          SmallVector<int, 16> Mask;
          ShuffleVectorInst::getShuffleMask(ConstOps[2], Mask);
          C = ConstantExpr::getShuffleVector(ConstOps[0], ConstOps[1], Mask);
          break;
        }
        default:
          llvm_unreachable("Unhandled bitcode constant");
        }
      }

      // Cache resolved constant.
      ValueList.replaceValueWithoutRAUW(ValID, C);
      MaterializedValues.insert({ValID, C});
      Worklist.pop_back();
      continue;
    }

    if (!InsertBB)
      return error(Twine("Value referenced by initializer is an unsupported "
                         "constant expression of type ") +
                   BC->getOpcodeName());

    // Materialize as instructions if necessary.
    Instruction *I;
    if (Instruction::isCast(BC->Opcode)) {
      I = CastInst::Create((Instruction::CastOps)BC->Opcode, Ops[0],
                           BC->getType(), "constexpr", InsertBB);
    } else if (Instruction::isUnaryOp(BC->Opcode)) {
      I = UnaryOperator::Create((Instruction::UnaryOps)BC->Opcode, Ops[0],
                                "constexpr", InsertBB);
    } else if (Instruction::isBinaryOp(BC->Opcode)) {
      I = BinaryOperator::Create((Instruction::BinaryOps)BC->Opcode, Ops[0],
                                 Ops[1], "constexpr", InsertBB);
      if (isa<OverflowingBinaryOperator>(I)) {
        if (BC->Flags & OverflowingBinaryOperator::NoSignedWrap)
          I->setHasNoSignedWrap();
        if (BC->Flags & OverflowingBinaryOperator::NoUnsignedWrap)
          I->setHasNoUnsignedWrap();
      }
      if (isa<PossiblyExactOperator>(I) &&
          (BC->Flags & PossiblyExactOperator::IsExact))
        I->setIsExact();
    } else {
      switch (BC->Opcode) {
      case BitcodeConstant::ConstantVectorOpcode: {
        Type *IdxTy = Type::getInt32Ty(BC->getContext());
        Value *V = PoisonValue::get(BC->getType());
        for (auto Pair : enumerate(Ops)) {
          Value *Idx = ConstantInt::get(IdxTy, Pair.index());
          V = InsertElementInst::Create(V, Pair.value(), Idx, "constexpr.ins",
                                        InsertBB);
        }
        I = cast<Instruction>(V);
        break;
      }
      case BitcodeConstant::ConstantStructOpcode:
      case BitcodeConstant::ConstantArrayOpcode: {
        Value *V = PoisonValue::get(BC->getType());
        for (auto Pair : enumerate(Ops))
          V = InsertValueInst::Create(V, Pair.value(), Pair.index(),
                                      "constexpr.ins", InsertBB);
        I = cast<Instruction>(V);
        break;
      }
      case Instruction::ICmp:
      case Instruction::FCmp:
        I = CmpInst::Create((Instruction::OtherOps)BC->Opcode,
                            (CmpInst::Predicate)BC->Flags, Ops[0], Ops[1],
                            "constexpr", InsertBB);
        break;
      case Instruction::GetElementPtr:
        I = GetElementPtrInst::Create(BC->SrcElemTy, Ops[0],
                                      ArrayRef(Ops).drop_front(), "constexpr",
                                      InsertBB);
        cast<GetElementPtrInst>(I)->setNoWrapFlags(toGEPNoWrapFlags(BC->Flags));
        break;
      case Instruction::Select:
        I = SelectInst::Create(Ops[0], Ops[1], Ops[2], "constexpr", InsertBB);
        break;
      case Instruction::ExtractElement:
        I = ExtractElementInst::Create(Ops[0], Ops[1], "constexpr", InsertBB);
        break;
      case Instruction::InsertElement:
        I = InsertElementInst::Create(Ops[0], Ops[1], Ops[2], "constexpr",
                                      InsertBB);
        break;
      case Instruction::ShuffleVector:
        I = new ShuffleVectorInst(Ops[0], Ops[1], Ops[2], "constexpr",
                                  InsertBB);
        break;
      default:
        llvm_unreachable("Unhandled bitcode constant");
      }
    }

    MaterializedValues.insert({ValID, I});
    Worklist.pop_back();
  }

  return MaterializedValues[StartValID];
}

Expected<Constant *> BitcodeReader::getValueForInitializer(unsigned ID) {
  Expected<Value *> MaybeV = materializeValue(ID, /* InsertBB */ nullptr);
  if (!MaybeV)
    return MaybeV.takeError();

  // Result must be Constant if InsertBB is nullptr.
  return cast<Constant>(MaybeV.get());
}

StructType *BitcodeReader::createIdentifiedStructType(LLVMContext &Context,
                                                      StringRef Name) {
  auto *Ret = StructType::create(Context, Name);
  IdentifiedStructTypes.push_back(Ret);
  return Ret;
}

StructType *BitcodeReader::createIdentifiedStructType(LLVMContext &Context) {
  auto *Ret = StructType::create(Context);
  IdentifiedStructTypes.push_back(Ret);
  return Ret;
}

//===----------------------------------------------------------------------===//
//  Functions for parsing blocks from the bitcode file
//===----------------------------------------------------------------------===//

static uint64_t getRawAttributeMask(Attribute::AttrKind Val) {
  switch (Val) {
  case Attribute::EndAttrKinds:
  case Attribute::EmptyKey:
  case Attribute::TombstoneKey:
    llvm_unreachable("Synthetic enumerators which should never get here");

  case Attribute::None:            return 0;
  case Attribute::ZExt:            return 1 << 0;
  case Attribute::SExt:            return 1 << 1;
  case Attribute::NoReturn:        return 1 << 2;
  case Attribute::InReg:           return 1 << 3;
  case Attribute::StructRet:       return 1 << 4;
  case Attribute::NoUnwind:        return 1 << 5;
  case Attribute::NoAlias:         return 1 << 6;
  case Attribute::ByVal:           return 1 << 7;
  case Attribute::Nest:            return 1 << 8;
  case Attribute::ReadNone:        return 1 << 9;
  case Attribute::ReadOnly:        return 1 << 10;
  case Attribute::NoInline:        return 1 << 11;
  case Attribute::AlwaysInline:    return 1 << 12;
  case Attribute::OptimizeForSize: return 1 << 13;
  case Attribute::StackProtect:    return 1 << 14;
  case Attribute::StackProtectReq: return 1 << 15;
  case Attribute::Alignment:       return 31 << 16;
  // 1ULL << 21 is NoCapture, which is upgraded separately.
  case Attribute::NoRedZone:       return 1 << 22;
  case Attribute::NoImplicitFloat: return 1 << 23;
  case Attribute::Naked:           return 1 << 24;
  case Attribute::InlineHint:      return 1 << 25;
  case Attribute::StackAlignment:  return 7 << 26;
  case Attribute::ReturnsTwice:    return 1 << 29;
  case Attribute::UWTable:         return 1 << 30;
  case Attribute::NonLazyBind:     return 1U << 31;
  case Attribute::SanitizeAddress: return 1ULL << 32;
  case Attribute::MinSize:         return 1ULL << 33;
  case Attribute::NoDuplicate:     return 1ULL << 34;
  case Attribute::StackProtectStrong: return 1ULL << 35;
  case Attribute::SanitizeThread:  return 1ULL << 36;
  case Attribute::SanitizeMemory:  return 1ULL << 37;
  case Attribute::NoBuiltin:       return 1ULL << 38;
  case Attribute::Returned:        return 1ULL << 39;
  case Attribute::Cold:            return 1ULL << 40;
  case Attribute::Builtin:         return 1ULL << 41;
  case Attribute::OptimizeNone:    return 1ULL << 42;
  case Attribute::InAlloca:        return 1ULL << 43;
  case Attribute::NonNull:         return 1ULL << 44;
  case Attribute::JumpTable:       return 1ULL << 45;
  case Attribute::Convergent:      return 1ULL << 46;
  case Attribute::SafeStack:       return 1ULL << 47;
  case Attribute::NoRecurse:       return 1ULL << 48;
  // 1ULL << 49 is InaccessibleMemOnly, which is upgraded separately.
  // 1ULL << 50 is InaccessibleMemOrArgMemOnly, which is upgraded separately.
  case Attribute::SwiftSelf:       return 1ULL << 51;
  case Attribute::SwiftError:      return 1ULL << 52;
  case Attribute::WriteOnly:       return 1ULL << 53;
  case Attribute::Speculatable:    return 1ULL << 54;
  case Attribute::StrictFP:        return 1ULL << 55;
  case Attribute::SanitizeHWAddress: return 1ULL << 56;
  case Attribute::NoCfCheck:       return 1ULL << 57;
  case Attribute::OptForFuzzing:   return 1ULL << 58;
  case Attribute::ShadowCallStack: return 1ULL << 59;
  case Attribute::SpeculativeLoadHardening:
    return 1ULL << 60;
  case Attribute::ImmArg:
    return 1ULL << 61;
  case Attribute::WillReturn:
    return 1ULL << 62;
  case Attribute::NoFree:
    return 1ULL << 63;
  default:
    // Other attributes are not supported in the raw format,
    // as we ran out of space.
    return 0;
  }
  llvm_unreachable("Unsupported attribute type");
}

static void addRawAttributeValue(AttrBuilder &B, uint64_t Val) {
  if (!Val) return;

  for (Attribute::AttrKind I = Attribute::None; I != Attribute::EndAttrKinds;
       I = Attribute::AttrKind(I + 1)) {
    if (uint64_t A = (Val & getRawAttributeMask(I))) {
      if (I == Attribute::Alignment)
        B.addAlignmentAttr(1ULL << ((A >> 16) - 1));
      else if (I == Attribute::StackAlignment)
        B.addStackAlignmentAttr(1ULL << ((A >> 26)-1));
      else if (Attribute::isTypeAttrKind(I))
        B.addTypeAttr(I, nullptr); // Type will be auto-upgraded.
      else
        B.addAttribute(I);
    }
  }
}

/// This fills an AttrBuilder object with the LLVM attributes that have
/// been decoded from the given integer.
static void decodeLLVMAttributesForBitcode(AttrBuilder &B,
                                           uint64_t EncodedAttrs,
                                           uint64_t AttrIdx) {
  // The alignment is stored as a 16-bit raw value from bits 31--16.  We shift
  // the bits above 31 down by 11 bits.
  unsigned Alignment = (EncodedAttrs & (0xffffULL << 16)) >> 16;
  assert((!Alignment || isPowerOf2_32(Alignment)) &&
         "Alignment must be a power of two.");

  if (Alignment)
    B.addAlignmentAttr(Alignment);

  uint64_t Attrs = ((EncodedAttrs & (0xfffffULL << 32)) >> 11) |
                   (EncodedAttrs & 0xffff);

  if (AttrIdx == AttributeList::FunctionIndex) {
    // Upgrade old memory attributes.
    MemoryEffects ME = MemoryEffects::unknown();
    if (Attrs & (1ULL << 9)) {
      // ReadNone
      Attrs &= ~(1ULL << 9);
      ME &= MemoryEffects::none();
    }
    if (Attrs & (1ULL << 10)) {
      // ReadOnly
      Attrs &= ~(1ULL << 10);
      ME &= MemoryEffects::readOnly();
    }
    if (Attrs & (1ULL << 49)) {
      // InaccessibleMemOnly
      Attrs &= ~(1ULL << 49);
      ME &= MemoryEffects::inaccessibleMemOnly();
    }
    if (Attrs & (1ULL << 50)) {
      // InaccessibleMemOrArgMemOnly
      Attrs &= ~(1ULL << 50);
      ME &= MemoryEffects::inaccessibleOrArgMemOnly();
    }
    if (Attrs & (1ULL << 53)) {
      // WriteOnly
      Attrs &= ~(1ULL << 53);
      ME &= MemoryEffects::writeOnly();
    }
    if (ME != MemoryEffects::unknown())
      B.addMemoryAttr(ME);
  }

  // Upgrade nocapture to captures(none).
  if (Attrs & (1ULL << 21)) {
    Attrs &= ~(1ULL << 21);
    B.addCapturesAttr(CaptureInfo::none());
  }

  addRawAttributeValue(B, Attrs);
}

Error BitcodeReader::parseAttributeBlock() {
  if (Error Err = Stream.EnterSubBlock(bitc::PARAMATTR_BLOCK_ID))
    return Err;

  if (!MAttributes.empty())
    return error("Invalid multiple blocks");

  SmallVector<uint64_t, 64> Record;

  SmallVector<AttributeList, 8> Attrs;

  // Read all the records.
  while (true) {
    Expected<BitstreamEntry> MaybeEntry = Stream.advanceSkippingSubblocks();
    if (!MaybeEntry)
      return MaybeEntry.takeError();
    BitstreamEntry Entry = MaybeEntry.get();

    switch (Entry.Kind) {
    case BitstreamEntry::SubBlock: // Handled for us already.
    case BitstreamEntry::Error:
      return error("Malformed block");
    case BitstreamEntry::EndBlock:
      return Error::success();
    case BitstreamEntry::Record:
      // The interesting case.
      break;
    }

    // Read a record.
    Record.clear();
    Expected<unsigned> MaybeRecord = Stream.readRecord(Entry.ID, Record);
    if (!MaybeRecord)
      return MaybeRecord.takeError();
    switch (MaybeRecord.get()) {
    default:  // Default behavior: ignore.
      break;
    case bitc::PARAMATTR_CODE_ENTRY_OLD: // ENTRY: [paramidx0, attr0, ...]
      // Deprecated, but still needed to read old bitcode files.
      if (Record.size() & 1)
        return error("Invalid parameter attribute record");

      for (unsigned i = 0, e = Record.size(); i != e; i += 2) {
        AttrBuilder B(Context);
        decodeLLVMAttributesForBitcode(B, Record[i+1], Record[i]);
        Attrs.push_back(AttributeList::get(Context, Record[i], B));
      }

      MAttributes.push_back(AttributeList::get(Context, Attrs));
      Attrs.clear();
      break;
    case bitc::PARAMATTR_CODE_ENTRY: // ENTRY: [attrgrp0, attrgrp1, ...]
      for (uint64_t Val : Record)
        Attrs.push_back(MAttributeGroups[Val]);

      MAttributes.push_back(AttributeList::get(Context, Attrs));
      Attrs.clear();
      break;
    }
  }
}

// Returns Attribute::None on unrecognized codes.
static Attribute::AttrKind getAttrFromCode(uint64_t Code) {
  switch (Code) {
  default:
    return Attribute::None;
  case bitc::ATTR_KIND_ALIGNMENT:
    return Attribute::Alignment;
  case bitc::ATTR_KIND_ALWAYS_INLINE:
    return Attribute::AlwaysInline;
  case bitc::ATTR_KIND_BUILTIN:
    return Attribute::Builtin;
  case bitc::ATTR_KIND_BY_VAL:
    return Attribute::ByVal;
  case bitc::ATTR_KIND_IN_ALLOCA:
    return Attribute::InAlloca;
  case bitc::ATTR_KIND_COLD:
    return Attribute::Cold;
  case bitc::ATTR_KIND_CONVERGENT:
    return Attribute::Convergent;
  case bitc::ATTR_KIND_DISABLE_SANITIZER_INSTRUMENTATION:
    return Attribute::DisableSanitizerInstrumentation;
  case bitc::ATTR_KIND_ELEMENTTYPE:
    return Attribute::ElementType;
  case bitc::ATTR_KIND_FNRETTHUNK_EXTERN:
    return Attribute::FnRetThunkExtern;
  case bitc::ATTR_KIND_INLINE_HINT:
    return Attribute::InlineHint;
  case bitc::ATTR_KIND_IN_REG:
    return Attribute::InReg;
  case bitc::ATTR_KIND_JUMP_TABLE:
    return Attribute::JumpTable;
  case bitc::ATTR_KIND_MEMORY:
    return Attribute::Memory;
  case bitc::ATTR_KIND_NOFPCLASS:
    return Attribute::NoFPClass;
  case bitc::ATTR_KIND_MIN_SIZE:
    return Attribute::MinSize;
  case bitc::ATTR_KIND_NAKED:
    return Attribute::Naked;
  case bitc::ATTR_KIND_NEST:
    return Attribute::Nest;
  case bitc::ATTR_KIND_NO_ALIAS:
    return Attribute::NoAlias;
  case bitc::ATTR_KIND_NO_BUILTIN:
    return Attribute::NoBuiltin;
  case bitc::ATTR_KIND_NO_CALLBACK:
    return Attribute::NoCallback;
  case bitc::ATTR_KIND_NO_DIVERGENCE_SOURCE:
    return Attribute::NoDivergenceSource;
  case bitc::ATTR_KIND_NO_DUPLICATE:
    return Attribute::NoDuplicate;
  case bitc::ATTR_KIND_NOFREE:
    return Attribute::NoFree;
  case bitc::ATTR_KIND_NO_IMPLICIT_FLOAT:
    return Attribute::NoImplicitFloat;
  case bitc::ATTR_KIND_NO_INLINE:
    return Attribute::NoInline;
  case bitc::ATTR_KIND_NO_RECURSE:
    return Attribute::NoRecurse;
  case bitc::ATTR_KIND_NO_MERGE:
    return Attribute::NoMerge;
  case bitc::ATTR_KIND_NON_LAZY_BIND:
    return Attribute::NonLazyBind;
  case bitc::ATTR_KIND_NON_NULL:
    return Attribute::NonNull;
  case bitc::ATTR_KIND_DEREFERENCEABLE:
    return Attribute::Dereferenceable;
  case bitc::ATTR_KIND_DEREFERENCEABLE_OR_NULL:
    return Attribute::DereferenceableOrNull;
  case bitc::ATTR_KIND_ALLOC_ALIGN:
    return Attribute::AllocAlign;
  case bitc::ATTR_KIND_ALLOC_KIND:
    return Attribute::AllocKind;
  case bitc::ATTR_KIND_ALLOC_SIZE:
    return Attribute::AllocSize;
  case bitc::ATTR_KIND_ALLOCATED_POINTER:
    return Attribute::AllocatedPointer;
  case bitc::ATTR_KIND_NO_RED_ZONE:
    return Attribute::NoRedZone;
  case bitc::ATTR_KIND_NO_RETURN:
    return Attribute::NoReturn;
  case bitc::ATTR_KIND_NOSYNC:
    return Attribute::NoSync;
  case bitc::ATTR_KIND_NOCF_CHECK:
    return Attribute::NoCfCheck;
  case bitc::ATTR_KIND_NO_PROFILE:
    return Attribute::NoProfile;
  case bitc::ATTR_KIND_SKIP_PROFILE:
    return Attribute::SkipProfile;
  case bitc::ATTR_KIND_NO_UNWIND:
    return Attribute::NoUnwind;
  case bitc::ATTR_KIND_NO_SANITIZE_BOUNDS:
    return Attribute::NoSanitizeBounds;
  case bitc::ATTR_KIND_NO_SANITIZE_COVERAGE:
    return Attribute::NoSanitizeCoverage;
  case bitc::ATTR_KIND_NULL_POINTER_IS_VALID:
    return Attribute::NullPointerIsValid;
  case bitc::ATTR_KIND_OPTIMIZE_FOR_DEBUGGING:
    return Attribute::OptimizeForDebugging;
  case bitc::ATTR_KIND_OPT_FOR_FUZZING:
    return Attribute::OptForFuzzing;
  case bitc::ATTR_KIND_OPTIMIZE_FOR_SIZE:
    return Attribute::OptimizeForSize;
  case bitc::ATTR_KIND_OPTIMIZE_NONE:
    return Attribute::OptimizeNone;
  case bitc::ATTR_KIND_READ_NONE:
    return Attribute::ReadNone;
  case bitc::ATTR_KIND_READ_ONLY:
    return Attribute::ReadOnly;
  case bitc::ATTR_KIND_RETURNED:
    return Attribute::Returned;
  case bitc::ATTR_KIND_RETURNS_TWICE:
    return Attribute::ReturnsTwice;
  case bitc::ATTR_KIND_S_EXT:
    return Attribute::SExt;
  case bitc::ATTR_KIND_SPECULATABLE:
    return Attribute::Speculatable;
  case bitc::ATTR_KIND_STACK_ALIGNMENT:
    return Attribute::StackAlignment;
  case bitc::ATTR_KIND_STACK_PROTECT:
    return Attribute::StackProtect;
  case bitc::ATTR_KIND_STACK_PROTECT_REQ:
    return Attribute::StackProtectReq;
  case bitc::ATTR_KIND_STACK_PROTECT_STRONG:
    return Attribute::StackProtectStrong;
  case bitc::ATTR_KIND_SAFESTACK:
    return Attribute::SafeStack;
  case bitc::ATTR_KIND_SHADOWCALLSTACK:
    return Attribute::ShadowCallStack;
  case bitc::ATTR_KIND_STRICT_FP:
    return Attribute::StrictFP;
  case bitc::ATTR_KIND_STRUCT_RET:
    return Attribute::StructRet;
  case bitc::ATTR_KIND_SANITIZE_ADDRESS:
    return Attribute::SanitizeAddress;
  case bitc::ATTR_KIND_SANITIZE_HWADDRESS:
    return Attribute::SanitizeHWAddress;
  case bitc::ATTR_KIND_SANITIZE_THREAD:
    return Attribute::SanitizeThread;
  case bitc::ATTR_KIND_SANITIZE_TYPE:
    return Attribute::SanitizeType;
  case bitc::ATTR_KIND_SANITIZE_MEMORY:
    return Attribute::SanitizeMemory;
  case bitc::ATTR_KIND_SANITIZE_NUMERICAL_STABILITY:
    return Attribute::SanitizeNumericalStability;
  case bitc::ATTR_KIND_SANITIZE_REALTIME:
    return Attribute::SanitizeRealtime;
  case bitc::ATTR_KIND_SANITIZE_REALTIME_BLOCKING:
    return Attribute::SanitizeRealtimeBlocking;
  case bitc::ATTR_KIND_SPECULATIVE_LOAD_HARDENING:
    return Attribute::SpeculativeLoadHardening;
  case bitc::ATTR_KIND_SWIFT_ERROR:
    return Attribute::SwiftError;
  case bitc::ATTR_KIND_SWIFT_SELF:
    return Attribute::SwiftSelf;
  case bitc::ATTR_KIND_SWIFT_ASYNC:
    return Attribute::SwiftAsync;
  case bitc::ATTR_KIND_UW_TABLE:
    return Attribute::UWTable;
  case bitc::ATTR_KIND_VSCALE_RANGE:
    return Attribute::VScaleRange;
  case bitc::ATTR_KIND_WILLRETURN:
    return Attribute::WillReturn;
  case bitc::ATTR_KIND_WRITEONLY:
    return Attribute::WriteOnly;
  case bitc::ATTR_KIND_Z_EXT:
    return Attribute::ZExt;
  case bitc::ATTR_KIND_IMMARG:
    return Attribute::ImmArg;
  case bitc::ATTR_KIND_SANITIZE_MEMTAG:
    return Attribute::SanitizeMemTag;
  case bitc::ATTR_KIND_PREALLOCATED:
    return Attribute::Preallocated;
  case bitc::ATTR_KIND_NOUNDEF:
    return Attribute::NoUndef;
  case bitc::ATTR_KIND_BYREF:
    return Attribute::ByRef;
  case bitc::ATTR_KIND_MUSTPROGRESS:
    return Attribute::MustProgress;
  case bitc::ATTR_KIND_HOT:
    return Attribute::Hot;
  case bitc::ATTR_KIND_PRESPLIT_COROUTINE:
    return Attribute::PresplitCoroutine;
  case bitc::ATTR_KIND_WRITABLE:
    return Attribute::Writable;
  case bitc::ATTR_KIND_CORO_ONLY_DESTROY_WHEN_COMPLETE:
    return Attribute::CoroDestroyOnlyWhenComplete;
  case bitc::ATTR_KIND_DEAD_ON_UNWIND:
    return Attribute::DeadOnUnwind;
  case bitc::ATTR_KIND_RANGE:
    return Attribute::Range;
  case bitc::ATTR_KIND_INITIALIZES:
    return Attribute::Initializes;
  case bitc::ATTR_KIND_CORO_ELIDE_SAFE:
    return Attribute::CoroElideSafe;
  case bitc::ATTR_KIND_NO_EXT:
    return Attribute::NoExt;
  case bitc::ATTR_KIND_CAPTURES:
    return Attribute::Captures;
  case bitc::ATTR_KIND_DEAD_ON_RETURN:
    return Attribute::DeadOnReturn;
  }
}

Error BitcodeReader::parseAlignmentValue(uint64_t Exponent,
                                         MaybeAlign &Alignment) {
  // 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 = decodeMaybeAlign(Exponent);
  return Error::success();
}

Error BitcodeReader::parseAttrKind(uint64_t Code, Attribute::AttrKind *Kind) {
  *Kind = getAttrFromCode(Code);
  if (*Kind == Attribute::None)
    return error("Unknown attribute kind (" + Twine(Code) + ")");
  return Error::success();
}

static bool upgradeOldMemoryAttribute(MemoryEffects &ME, uint64_t EncodedKind) {
  switch (EncodedKind) {
  case bitc::ATTR_KIND_READ_NONE:
    ME &= MemoryEffects::none();
    return true;
  case bitc::ATTR_KIND_READ_ONLY:
    ME &= MemoryEffects::readOnly();
    return true;
  case bitc::ATTR_KIND_WRITEONLY:
    ME &= MemoryEffects::writeOnly();
    return true;
  case bitc::ATTR_KIND_ARGMEMONLY:
    ME &= MemoryEffects::argMemOnly();
    return true;
  case bitc::ATTR_KIND_INACCESSIBLEMEM_ONLY:
    ME &= MemoryEffects::inaccessibleMemOnly();
    return true;
  case bitc::ATTR_KIND_INACCESSIBLEMEM_OR_ARGMEMONLY:
    ME &= MemoryEffects::inaccessibleOrArgMemOnly();
    return true;
  default:
    return false;
  }
}

Error BitcodeReader::parseAttributeGroupBlock() {
  if (Error Err = Stream.EnterSubBlock(bitc::PARAMATTR_GROUP_BLOCK_ID))
    return Err;

  if (!MAttributeGroups.empty())
    return error("Invalid multiple blocks");

  SmallVector<uint64_t, 64> Record;

  // Read all the records.
  while (true) {
    Expected<BitstreamEntry> MaybeEntry = Stream.advanceSkippingSubblocks();
    if (!MaybeEntry)
      return MaybeEntry.takeError();
    BitstreamEntry Entry = MaybeEntry.get();

    switch (Entry.Kind) {
    case BitstreamEntry::SubBlock: // Handled for us already.
    case BitstreamEntry::Error:
      return error("Malformed block");
    case BitstreamEntry::EndBlock:
      return Error::success();
    case BitstreamEntry::Record:
      // The interesting case.
      break;
    }

    // Read a record.
    Record.clear();
    Expected<unsigned> MaybeRecord = Stream.readRecord(Entry.ID, Record);
    if (!MaybeRecord)
      return MaybeRecord.takeError();
    switch (MaybeRecord.get()) {
    default:  // Default behavior: ignore.
      break;
    case bitc::PARAMATTR_GRP_CODE_ENTRY: { // ENTRY: [grpid, idx, a0, a1, ...]
      if (Record.size() < 3)
        return error("Invalid grp record");

      uint64_t GrpID = Record[0];
      uint64_t Idx = Record[1]; // Index of the object this attribute refers to.

      AttrBuilder B(Context);
      MemoryEffects ME = MemoryEffects::unknown();
      for (unsigned i = 2, e = Record.size(); i != e; ++i) {
        if (Record[i] == 0) {        // Enum attribute
          Attribute::AttrKind Kind;
          uint64_t EncodedKind = Record[++i];
          if (Idx == AttributeList::FunctionIndex &&
              upgradeOldMemoryAttribute(ME, EncodedKind))
            continue;

          if (EncodedKind == bitc::ATTR_KIND_NO_CAPTURE) {
            B.addCapturesAttr(CaptureInfo::none());
            continue;
          }

          if (Error Err = parseAttrKind(EncodedKind, &Kind))
            return Err;

          // Upgrade old-style byval attribute to one with a type, even if it's
          // nullptr. We will have to insert the real type when we associate
          // this AttributeList with a function.
          if (Kind == Attribute::ByVal)
            B.addByValAttr(nullptr);
          else if (Kind == Attribute::StructRet)
            B.addStructRetAttr(nullptr);
          else if (Kind == Attribute::InAlloca)
            B.addInAllocaAttr(nullptr);
          else if (Kind == Attribute::UWTable)
            B.addUWTableAttr(UWTableKind::Default);
          else if (Attribute::isEnumAttrKind(Kind))
            B.addAttribute(Kind);
          else
            return error("Not an enum attribute");
        } else if (Record[i] == 1) { // Integer attribute
          Attribute::AttrKind Kind;
          if (Error Err = parseAttrKind(Record[++i], &Kind))
            return Err;
          if (!Attribute::isIntAttrKind(Kind))
            return error("Not an int attribute");
          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]);
          else if (Kind == Attribute::AllocSize)
            B.addAllocSizeAttrFromRawRepr(Record[++i]);
          else if (Kind == Attribute::VScaleRange)
            B.addVScaleRangeAttrFromRawRepr(Record[++i]);
          else if (Kind == Attribute::UWTable)
            B.addUWTableAttr(UWTableKind(Record[++i]));
          else if (Kind == Attribute::AllocKind)
            B.addAllocKindAttr(static_cast<AllocFnKind>(Record[++i]));
          else if (Kind == Attribute::Memory) {
            uint64_t EncodedME = Record[++i];
            const uint8_t Version = (EncodedME >> 56);
            if (Version == 0) {
              // Errno memory location was previously encompassed into default
              // memory. Ensure this is taken into account while reconstructing
              // the memory attribute prior to its introduction.
              ModRefInfo ArgMem = ModRefInfo((EncodedME >> 0) & 3);
              ModRefInfo InaccessibleMem = ModRefInfo((EncodedME >> 2) & 3);
              ModRefInfo OtherMem = ModRefInfo((EncodedME >> 4) & 3);
              auto ME = MemoryEffects::inaccessibleMemOnly(InaccessibleMem) |
                        MemoryEffects::argMemOnly(ArgMem) |
                        MemoryEffects::errnoMemOnly(OtherMem) |
                        MemoryEffects::otherMemOnly(OtherMem);
              B.addMemoryAttr(ME);
            } else {
              // Construct the memory attribute directly from the encoded base
              // on newer versions.
              B.addMemoryAttr(MemoryEffects::createFromIntValue(
                  EncodedME & 0x00FFFFFFFFFFFFFFULL));
            }
          } else if (Kind == Attribute::Captures)
            B.addCapturesAttr(CaptureInfo::createFromIntValue(Record[++i]));
          else if (Kind == Attribute::NoFPClass)
            B.addNoFPClassAttr(
                static_cast<FPClassTest>(Record[++i] & fcAllFlags));
        } else if (Record[i] == 3 || Record[i] == 4) { // String attribute
          bool HasValue = (Record[i++] == 4);
          SmallString<64> KindStr;
          SmallString<64> ValStr;

          while (Record[i] != 0 && i != e)
            KindStr += Record[i++];
          assert(Record[i] == 0 && "Kind string not null terminated");

          if (HasValue) {
            // Has a value associated with it.
            ++i; // Skip the '0' that terminates the "kind" string.
            while (Record[i] != 0 && i != e)
              ValStr += Record[i++];
            assert(Record[i] == 0 && "Value string not null terminated");
          }

          B.addAttribute(KindStr.str(), ValStr.str());
        } else if (Record[i] == 5 || Record[i] == 6) {
          bool HasType = Record[i] == 6;
          Attribute::AttrKind Kind;
          if (Error Err = parseAttrKind(Record[++i], &Kind))
            return Err;
          if (!Attribute::isTypeAttrKind(Kind))
            return error("Not a type attribute");

          B.addTypeAttr(Kind, HasType ? getTypeByID(Record[++i]) : nullptr);
        } else if (Record[i] == 7) {
          Attribute::AttrKind Kind;

          i++;
          if (Error Err = parseAttrKind(Record[i++], &Kind))
            return Err;
          if (!Attribute::isConstantRangeAttrKind(Kind))
            return error("Not a ConstantRange attribute");

          Expected<ConstantRange> MaybeCR =
              readBitWidthAndConstantRange(Record, i);
          if (!MaybeCR)
            return MaybeCR.takeError();
          i--;

          B.addConstantRangeAttr(Kind, MaybeCR.get());
        } else if (Record[i] == 8) {
          Attribute::AttrKind Kind;

          i++;
          if (Error Err = parseAttrKind(Record[i++], &Kind))
            return Err;
          if (!Attribute::isConstantRangeListAttrKind(Kind))
            return error("Not a constant range list attribute");

          SmallVector<ConstantRange, 2> Val;
          if (i + 2 > e)
            return error("Too few records for constant range list");
          unsigned RangeSize = Record[i++];
          unsigned BitWidth = Record[i++];
          for (unsigned Idx = 0; Idx < RangeSize; ++Idx) {
            Expected<ConstantRange> MaybeCR =
                readConstantRange(Record, i, BitWidth);
            if (!MaybeCR)
              return MaybeCR.takeError();
            Val.push_back(MaybeCR.get());
          }
          i--;

          if (!ConstantRangeList::isOrderedRanges(Val))
            return error("Invalid (unordered or overlapping) range list");
          B.addConstantRangeListAttr(Kind, Val);
        } else {
          return error("Invalid attribute group entry");
        }
      }

      if (ME != MemoryEffects::unknown())
        B.addMemoryAttr(ME);

      UpgradeAttributes(B);
      MAttributeGroups[GrpID] = AttributeList::get(Context, Idx, B);
      break;
    }
    }
  }
}

Error BitcodeReader::parseTypeTable() {
  if (Error Err = Stream.EnterSubBlock(bitc::TYPE_BLOCK_ID_NEW))
    return Err;

  return 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) {
    Expected<BitstreamEntry> MaybeEntry = Stream.advanceSkippingSubblocks();
    if (!MaybeEntry)
      return MaybeEntry.takeError();
    BitstreamEntry Entry = MaybeEntry.get();

    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 Error::success();
    case BitstreamEntry::Record:
      // The interesting case.
      break;
    }

    // Read a record.
    Record.clear();
    Type *ResultTy = nullptr;
    SmallVector<unsigned> ContainedIDs;
    Expected<unsigned> MaybeRecord = Stream.readRecord(Entry.ID, Record);
    if (!MaybeRecord)
      return MaybeRecord.takeError();
    switch (MaybeRecord.get()) {
    default:
      return error("Invalid value");
    case bitc::TYPE_CODE_NUMENTRY: // TYPE_CODE_NUMENTRY: [numentries]
      // TYPE_CODE_NUMENTRY contains a count of the number of types in the
      // type list.  This allows us to reserve space.
      if (Record.empty())
        return error("Invalid numentry record");
      TypeList.resize(Record[0]);
      continue;
    case bitc::TYPE_CODE_VOID:      // VOID
      ResultTy = Type::getVoidTy(Context);
      break;
    case bitc::TYPE_CODE_HALF:     // HALF
      ResultTy = Type::getHalfTy(Context);
      break;
    case bitc::TYPE_CODE_BFLOAT:    // BFLOAT
      ResultTy = Type::getBFloatTy(Context);
      break;
    case bitc::TYPE_CODE_FLOAT:     // FLOAT
      ResultTy = Type::getFloatTy(Context);
      break;
    case bitc::TYPE_CODE_DOUBLE:    // DOUBLE
      ResultTy = Type::getDoubleTy(Context);
      break;
    case bitc::TYPE_CODE_X86_FP80:  // X86_FP80
      ResultTy = Type::getX86_FP80Ty(Context);
      break;
    case bitc::TYPE_CODE_FP128:     // FP128
      ResultTy = Type::getFP128Ty(Context);
      break;
    case bitc::TYPE_CODE_PPC_FP128: // PPC_FP128
      ResultTy = Type::getPPC_FP128Ty(Context);
      break;
    case bitc::TYPE_CODE_LABEL:     // LABEL
      ResultTy = Type::getLabelTy(Context);
      break;
    case bitc::TYPE_CODE_METADATA:  // METADATA
      ResultTy = Type::getMetadataTy(Context);
      break;
    case bitc::TYPE_CODE_X86_MMX:   // X86_MMX
      // Deprecated: decodes as <1 x i64>
      ResultTy =
          llvm::FixedVectorType::get(llvm::IntegerType::get(Context, 64), 1);
      break;
    case bitc::TYPE_CODE_X86_AMX:   // X86_AMX
      ResultTy = Type::getX86_AMXTy(Context);
      break;
    case bitc::TYPE_CODE_TOKEN:     // TOKEN
      ResultTy = Type::getTokenTy(Context);
      break;
    case bitc::TYPE_CODE_INTEGER: { // INTEGER: [width]
      if (Record.empty())
        return error("Invalid integer record");

      uint64_t NumBits = Record[0];
      if (NumBits < IntegerType::MIN_INT_BITS ||
          NumBits > IntegerType::MAX_INT_BITS)
        return error("Bitwidth for integer type out of range");
      ResultTy = IntegerType::get(Context, NumBits);
      break;
    }
    case bitc::TYPE_CODE_POINTER: { // POINTER: [pointee type] or
                                    //          [pointee type, address space]
      if (Record.empty())
        return error("Invalid pointer record");
      unsigned AddressSpace = 0;
      if (Record.size() == 2)
        AddressSpace = Record[1];
      ResultTy = getTypeByID(Record[0]);
      if (!ResultTy ||
          !PointerType::isValidElementType(ResultTy))
        return error("Invalid type");
      ContainedIDs.push_back(Record[0]);
      ResultTy = PointerType::get(ResultTy->getContext(), AddressSpace);
      break;
    }
    case bitc::TYPE_CODE_OPAQUE_POINTER: { // OPAQUE_POINTER: [addrspace]
      if (Record.size() != 1)
        return error("Invalid opaque pointer record");
      unsigned AddressSpace = Record[0];
      ResultTy = PointerType::get(Context, AddressSpace);
      break;
    }
    case bitc::TYPE_CODE_FUNCTION_OLD: {
      // Deprecated, but still needed to read old bitcode files.
      // FUNCTION: [vararg, attrid, retty, paramty x N]
      if (Record.size() < 3)
        return error("Invalid function record");
      SmallVector<Type*, 8> ArgTys;
      for (unsigned i = 3, e = Record.size(); i != e; ++i) {
        if (Type *T = getTypeByID(Record[i]))
          ArgTys.push_back(T);
        else
          break;
      }

      ResultTy = getTypeByID(Record[2]);
      if (!ResultTy || ArgTys.size() < Record.size()-3)
        return error("Invalid type");

      ContainedIDs.append(Record.begin() + 2, Record.end());
      ResultTy = FunctionType::get(ResultTy, ArgTys, Record[0]);
      break;
    }
    case bitc::TYPE_CODE_FUNCTION: {
      // FUNCTION: [vararg, retty, paramty x N]
      if (Record.size() < 2)
        return error("Invalid function record");
      SmallVector<Type*, 8> ArgTys;
      for (unsigned i = 2, e = Record.size(); i != e; ++i) {
        if (Type *T = getTypeByID(Record[i])) {
          if (!FunctionType::isValidArgumentType(T))
            return error("Invalid function argument type");
          ArgTys.push_back(T);
        }
        else
          break;
      }

      ResultTy = getTypeByID(Record[1]);
      if (!ResultTy || ArgTys.size() < Record.size()-2)
        return error("Invalid type");

      ContainedIDs.append(Record.begin() + 1, Record.end());
      ResultTy = FunctionType::get(ResultTy, ArgTys, Record[0]);
      break;
    }
    case bitc::TYPE_CODE_STRUCT_ANON: {  // STRUCT: [ispacked, eltty x N]
      if (Record.empty())
        return error("Invalid anon struct record");
      SmallVector<Type*, 8> EltTys;
      for (unsigned i = 1, e = Record.size(); i != e; ++i) {
        if (Type *T = getTypeByID(Record[i]))
          EltTys.push_back(T);
        else
          break;
      }
      if (EltTys.size() != Record.size()-1)
        return error("Invalid type");
      ContainedIDs.append(Record.begin() + 1, Record.end());
      ResultTy = StructType::get(Context, EltTys, Record[0]);
      break;
    }
    case bitc::TYPE_CODE_STRUCT_NAME:   // STRUCT_NAME: [strchr x N]
      if (convertToString(Record, 0, TypeName))
        return error("Invalid struct name record");
      continue;

    case bitc::TYPE_CODE_STRUCT_NAMED: { // STRUCT: [ispacked, eltty x N]
      if (Record.empty())
        return error("Invalid named struct record");

      if (NumRecords >= TypeList.size())
        return error("Invalid TYPE table");

      // Check to see if this was forward referenced, if so fill in the temp.
      StructType *Res = cast_or_null<StructType>(TypeList[NumRecords]);
      if (Res) {
        Res->setName(TypeName);
        TypeList[NumRecords] = nullptr;
      } else  // Otherwise, create a new struct.
        Res = createIdentifiedStructType(Context, TypeName);
      TypeName.clear();

      SmallVector<Type*, 8> EltTys;
      for (unsigned i = 1, e = Record.size(); i != e; ++i) {
        if (Type *T = getTypeByID(Record[i]))
          EltTys.push_back(T);
        else
          break;
      }
      if (EltTys.size() != Record.size()-1)
        return error("Invalid named struct record");
      if (auto E = Res->setBodyOrError(EltTys, Record[0]))
        return E;
      ContainedIDs.append(Record.begin() + 1, Record.end());
      ResultTy = Res;
      break;
    }
    case bitc::TYPE_CODE_OPAQUE: {       // OPAQUE: []
      if (Record.size() != 1)
        return error("Invalid opaque type record");

      if (NumRecords >= TypeList.size())
        return error("Invalid TYPE table");

      // Check to see if this was forward referenced, if so fill in the temp.
      StructType *Res = cast_or_null<StructType>(TypeList[NumRecords]);
      if (Res) {
        Res->setName(TypeName);
        TypeList[NumRecords] = nullptr;
      } else  // Otherwise, create a new struct with no body.
        Res = createIdentifiedStructType(Context, TypeName);
      TypeName.clear();
      ResultTy = Res;
      break;
    }
    case bitc::TYPE_CODE_TARGET_TYPE: { // TARGET_TYPE: [NumTy, Tys..., Ints...]
      if (Record.size() < 1)
        return error("Invalid target extension type record");

      if (NumRecords >= TypeList.size())
        return error("Invalid TYPE table");

      if (Record[0] >= Record.size())
        return error("Too many type parameters");

      unsigned NumTys = Record[0];
      SmallVector<Type *, 4> TypeParams;
      SmallVector<unsigned, 8> IntParams;
      for (unsigned i = 0; i < NumTys; i++) {
        if (Type *T = getTypeByID(Record[i + 1]))
          TypeParams.push_back(T);
        else
          return error("Invalid type");
      }

      for (unsigned i = NumTys + 1, e = Record.size(); i < e; i++) {
        if (Record[i] > UINT_MAX)
          return error("Integer parameter too large");
        IntParams.push_back(Record[i]);
      }
      auto TTy =
          TargetExtType::getOrError(Context, TypeName, TypeParams, IntParams);
      if (auto E = TTy.takeError())
        return E;
      ResultTy = *TTy;
      TypeName.clear();
      break;
    }
    case bitc::TYPE_CODE_ARRAY:     // ARRAY: [numelts, eltty]
      if (Record.size() < 2)
        return error("Invalid array type record");
      ResultTy = getTypeByID(Record[1]);
      if (!ResultTy || !ArrayType::isValidElementType(ResultTy))
        return error("Invalid type");
      ContainedIDs.push_back(Record[1]);
      ResultTy = ArrayType::get(ResultTy, Record[0]);
      break;
    case bitc::TYPE_CODE_VECTOR:    // VECTOR: [numelts, eltty] or
                                    //         [numelts, eltty, scalable]
      if (Record.size() < 2)
        return error("Invalid vector type record");
      if (Record[0] == 0)
        return error("Invalid vector length");
      ResultTy = getTypeByID(Record[1]);
      if (!ResultTy || !VectorType::isValidElementType(ResultTy))
        return error("Invalid type");
      bool Scalable = Record.size() > 2 ? Record[2] : false;
      ContainedIDs.push_back(Record[1]);
      ResultTy = VectorType::get(ResultTy, Record[0], Scalable);
      break;
    }

    if (NumRecords >= TypeList.size())
      return error("Invalid TYPE table");
    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;
    if (!ContainedIDs.empty())
      ContainedTypeIDs[NumRecords] = std::move(ContainedIDs);
    ++NumRecords;
  }
}

Error BitcodeReader::parseOperandBundleTags() {
  if (Error Err = Stream.EnterSubBlock(bitc::OPERAND_BUNDLE_TAGS_BLOCK_ID))
    return Err;

  if (!BundleTags.empty())
    return error("Invalid multiple blocks");

  SmallVector<uint64_t, 64> Record;

  while (true) {
    Expected<BitstreamEntry> MaybeEntry = Stream.advanceSkippingSubblocks();
    if (!MaybeEntry)
      return MaybeEntry.takeError();
    BitstreamEntry Entry = MaybeEntry.get();

    switch (Entry.Kind) {
    case BitstreamEntry::SubBlock: // Handled for us already.
    case BitstreamEntry::Error:
      return error("Malformed block");
    case BitstreamEntry::EndBlock:
      return Error::success();
    case BitstreamEntry::Record:
      // The interesting case.
      break;
    }

    // Tags are implicitly mapped to integers by their order.

    Expected<unsigned> MaybeRecord = Stream.readRecord(Entry.ID, Record);
    if (!MaybeRecord)
      return MaybeRecord.takeError();
    if (MaybeRecord.get() != bitc::OPERAND_BUNDLE_TAG)
      return error("Invalid operand bundle record");

    // OPERAND_BUNDLE_TAG: [strchr x N]
    BundleTags.emplace_back();
    if (convertToString(Record, 0, BundleTags.back()))
      return error("Invalid operand bundle record");
    Record.clear();
  }
}

Error BitcodeReader::parseSyncScopeNames() {
  if (Error Err = Stream.EnterSubBlock(bitc::SYNC_SCOPE_NAMES_BLOCK_ID))
    return Err;

  if (!SSIDs.empty())
    return error("Invalid multiple synchronization scope names blocks");

  SmallVector<uint64_t, 64> Record;
  while (true) {
    Expected<BitstreamEntry> MaybeEntry = Stream.advanceSkippingSubblocks();
    if (!MaybeEntry)
      return MaybeEntry.takeError();
    BitstreamEntry Entry = MaybeEntry.get();

    switch (Entry.Kind) {
    case BitstreamEntry::SubBlock: // Handled for us already.
    case BitstreamEntry::Error:
      return error("Malformed block");
    case BitstreamEntry::EndBlock:
      if (SSIDs.empty())
        return error("Invalid empty synchronization scope names block");
      return Error::success();
    case BitstreamEntry::Record:
      // The interesting case.
      break;
    }

    // Synchronization scope names are implicitly mapped to synchronization
    // scope IDs by their order.

    Expected<unsigned> MaybeRecord = Stream.readRecord(Entry.ID, Record);
    if (!MaybeRecord)
      return MaybeRecord.takeError();
    if (MaybeRecord.get() != bitc::SYNC_SCOPE_NAME)
      return error("Invalid sync scope record");

    SmallString<16> SSN;
    if (convertToString(Record, 0, SSN))
      return error("Invalid sync scope record");

    SSIDs.push_back(Context.getOrInsertSyncScopeID(SSN));
    Record.clear();
  }
}

/// Associate a value with its name from the given index in the provided 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];

  StringRef NameStr(ValueName.data(), ValueName.size());
  if (NameStr.contains(0))
    return error("Invalid value name");
  V->setName(NameStr);
  auto *GO = dyn_cast<GlobalObject>(V);
  if (GO && ImplicitComdatObjects.contains(GO) && TT.supportsCOMDAT())
    GO->setComdat(TheModule->getOrInsertComdat(V->getName()));
  return V;
}

/// Helper to note and return the current location, and jump to the given
/// offset.
static Expected<uint64_t> jumpToValueSymbolTable(uint64_t Offset,
                                                 BitstreamCursor &Stream) {
  // Save the current parsing location so we can jump back at the end
  // of the VST read.
  uint64_t CurrentBit = Stream.GetCurrentBitNo();
  if (Error JumpFailed = Stream.JumpToBit(Offset * 32))
    return std::move(JumpFailed);
  Expected<BitstreamEntry> MaybeEntry = Stream.advance();
  if (!MaybeEntry)
    return MaybeEntry.takeError();
  if (MaybeEntry.get().Kind != BitstreamEntry::SubBlock ||
      MaybeEntry.get().ID != bitc::VALUE_SYMTAB_BLOCK_ID)
    return error("Expected value symbol table subblock");
  return CurrentBit;
}

void BitcodeReader::setDeferredFunctionInfo(unsigned FuncBitcodeOffsetDelta,
                                            Function *F,
                                            ArrayRef<uint64_t> Record) {
  // Note that we subtract 1 here because the offset is relative to one word
  // before the start of the identification or module block, which was
  // historically always the start of the regular bitcode header.
  uint64_t FuncWordOffset = Record[1] - 1;
  uint64_t FuncBitOffset = FuncWordOffset * 32;
  DeferredFunctionInfo[F] = FuncBitOffset + FuncBitcodeOffsetDelta;
  // Set the LastFunctionBlockBit to point to the last function block.
  // Later when parsing is resumed after function materialization,
  // we can simply skip that last function block.
  if (FuncBitOffset > LastFunctionBlockBit)
    LastFunctionBlockBit = FuncBitOffset;
}

/// Read a new-style GlobalValue symbol table.
Error BitcodeReader::parseGlobalValueSymbolTable() {
  unsigned FuncBitcodeOffsetDelta =
      Stream.getAbbrevIDWidth() + bitc::BlockIDWidth;

  if (Error Err = Stream.EnterSubBlock(bitc::VALUE_SYMTAB_BLOCK_ID))
    return Err;

  SmallVector<uint64_t, 64> Record;
  while (true) {
    Expected<BitstreamEntry> MaybeEntry = Stream.advanceSkippingSubblocks();
    if (!MaybeEntry)
      return MaybeEntry.takeError();
    BitstreamEntry Entry = MaybeEntry.get();

    switch (Entry.Kind) {
    case BitstreamEntry::SubBlock:
    case BitstreamEntry::Error:
      return error("Malformed block");
    case BitstreamEntry::EndBlock:
      return Error::success();
    case BitstreamEntry::Record:
      break;
    }

    Record.clear();
    Expected<unsigned> MaybeRecord = Stream.readRecord(Entry.ID, Record);
    if (!MaybeRecord)
      return MaybeRecord.takeError();
    switch (MaybeRecord.get()) {
    case bitc::VST_CODE_FNENTRY: { // [valueid, offset]
      unsigned ValueID = Record[0];
      if (ValueID >= ValueList.size() || !ValueList[ValueID])
        return error("Invalid value reference in symbol table");
      setDeferredFunctionInfo(FuncBitcodeOffsetDelta,
                              cast<Function>(ValueList[ValueID]), Record);
      break;
    }
    }
  }
}

/// Parse the value symbol table at either the current parsing location or
/// at the given bit offset if provided.
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) {
    Expected<uint64_t> MaybeCurrentBit = jumpToValueSymbolTable(Offset, Stream);
    if (!MaybeCurrentBit)
      return MaybeCurrentBit.takeError();
    CurrentBit = MaybeCurrentBit.get();
    // If this module uses a string table, read this as a module-level VST.
    if (UseStrtab) {
      if (Error Err = parseGlobalValueSymbolTable())
        return Err;
      if (Error JumpFailed = Stream.JumpToBit(CurrentBit))
        return JumpFailed;
      return Error::success();
    }
    // Otherwise, the VST will be in a similar format to a function-level VST,
    // and will contain symbol names.
  }

  // Compute the delta between the bitcode indices in the VST (the word offset
  // to the word-aligned ENTER_SUBBLOCK for the function block, and that
  // expected by the lazy reader. The reader's EnterSubBlock expects to have
  // already read the ENTER_SUBBLOCK code (size getAbbrevIDWidth) and BlockID
  // (size BlockIDWidth). Note that we access the stream's AbbrevID width here
  // just before entering the VST subblock because: 1) the EnterSubBlock
  // changes the AbbrevID width; 2) the VST block is nested within the same
  // outer MODULE_BLOCK as the FUNCTION_BLOCKs and therefore have the same
  // AbbrevID width before calling EnterSubBlock; and 3) when we want to
  // jump to the FUNCTION_BLOCK using this offset later, we don't want
  // to rely on the stream's AbbrevID width being that of the MODULE_BLOCK.
  unsigned FuncBitcodeOffsetDelta =
      Stream.getAbbrevIDWidth() + bitc::BlockIDWidth;

  if (Error Err = Stream.EnterSubBlock(bitc::VALUE_SYMTAB_BLOCK_ID))
    return Err;

  SmallVector<uint64_t, 64> Record;

  Triple TT(TheModule->getTargetTriple());

  // Read all the records for this value table.
  SmallString<128> ValueName;

  while (true) {
    Expected<BitstreamEntry> MaybeEntry = Stream.advanceSkippingSubblocks();
    if (!MaybeEntry)
      return MaybeEntry.takeError();
    BitstreamEntry Entry = MaybeEntry.get();

    switch (Entry.Kind) {
    case BitstreamEntry::SubBlock: // Handled for us already.
    case BitstreamEntry::Error:
      return error("Malformed block");
    case BitstreamEntry::EndBlock:
      if (Offset > 0)
        if (Error JumpFailed = Stream.JumpToBit(CurrentBit))
          return JumpFailed;
      return Error::success();
    case BitstreamEntry::Record:
      // The interesting case.
      break;
    }

    // Read a record.
    Record.clear();
    Expected<unsigned> MaybeRecord = Stream.readRecord(Entry.ID, Record);
    if (!MaybeRecord)
      return MaybeRecord.takeError();
    switch (MaybeRecord.get()) {
    default:  // Default behavior: unknown type.
      break;
    case bitc::VST_CODE_ENTRY: {  // VST_CODE_ENTRY: [valueid, namechar x N]
      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]
      Expected<Value *> ValOrErr = recordValue(Record, 2, TT);
      if (Error Err = ValOrErr.takeError())
        return Err;
      Value *V = ValOrErr.get();

      // Ignore function offsets emitted for aliases of functions in older
      // versions of LLVM.
      if (auto *F = dyn_cast<Function>(V))
        setDeferredFunctionInfo(FuncBitcodeOffsetDelta, F, Record);
      break;
    }
    case bitc::VST_CODE_BBENTRY: {
      if (convertToString(Record, 1, ValueName))
        return error("Invalid bbentry record");
      BasicBlock *BB = getBasicBlock(Record[0]);
      if (!BB)
        return error("Invalid bbentry record");

      BB->setName(ValueName.str());
      ValueName.clear();
      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.
Error BitcodeReader::resolveGlobalAndIndirectSymbolInits() {
  std::vector<std::pair<GlobalVariable *, unsigned>> GlobalInitWorklist;
  std::vector<std::pair<GlobalValue *, unsigned>> IndirectSymbolInitWorklist;
  std::vector<FunctionOperandInfo> FunctionOperandWorklist;

  GlobalInitWorklist.swap(GlobalInits);
  IndirectSymbolInitWorklist.swap(IndirectSymbolInits);
  FunctionOperandWorklist.swap(FunctionOperands);

  while (!GlobalInitWorklist.empty()) {
    unsigned ValID = GlobalInitWorklist.back().second;
    if (ValID >= ValueList.size()) {
      // Not ready to resolve this yet, it requires something later in the file.
      GlobalInits.push_back(GlobalInitWorklist.back());
    } else {
      Expected<Constant *> MaybeC = getValueForInitializer(ValID);
      if (!MaybeC)
        return MaybeC.takeError();
      GlobalInitWorklist.back().first->setInitializer(MaybeC.get());
    }
    GlobalInitWorklist.pop_back();
  }

  while (!IndirectSymbolInitWorklist.empty()) {
    unsigned ValID = IndirectSymbolInitWorklist.back().second;
    if (ValID >= ValueList.size()) {
      IndirectSymbolInits.push_back(IndirectSymbolInitWorklist.back());
    } else {
      Expected<Constant *> MaybeC = getValueForInitializer(ValID);
      if (!MaybeC)
        return MaybeC.takeError();
      Constant *C = MaybeC.get();
      GlobalValue *GV = IndirectSymbolInitWorklist.back().first;
      if (auto *GA = dyn_cast<GlobalAlias>(GV)) {
        if (C->getType() != GV->getType())
          return error("Alias and aliasee types don't match");
        GA->setAliasee(C);
      } else if (auto *GI = dyn_cast<GlobalIFunc>(GV)) {
        GI->setResolver(C);
      } else {
        return error("Expected an alias or an ifunc");
      }
    }
    IndirectSymbolInitWorklist.pop_back();
  }

  while (!FunctionOperandWorklist.empty()) {
    FunctionOperandInfo &Info = FunctionOperandWorklist.back();
    if (Info.PersonalityFn) {
      unsigned ValID = Info.PersonalityFn - 1;
      if (ValID < ValueList.size()) {
        Expected<Constant *> MaybeC = getValueForInitializer(ValID);
        if (!MaybeC)
          return MaybeC.takeError();
        Info.F->setPersonalityFn(MaybeC.get());
        Info.PersonalityFn = 0;
      }
    }
    if (Info.Prefix) {
      unsigned ValID = Info.Prefix - 1;
      if (ValID < ValueList.size()) {
        Expected<Constant *> MaybeC = getValueForInitializer(ValID);
        if (!MaybeC)
          return MaybeC.takeError();
        Info.F->setPrefixData(MaybeC.get());
        Info.Prefix = 0;
      }
    }
    if (Info.Prologue) {
      unsigned ValID = Info.Prologue - 1;
      if (ValID < ValueList.size()) {
        Expected<Constant *> MaybeC = getValueForInitializer(ValID);
        if (!MaybeC)
          return MaybeC.takeError();