lib/ProfileData/SampleProfReader.cpp

//===- SampleProfReader.cpp - Read LLVM sample profile data ---------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
// This file implements the class that reads LLVM sample profiles. It
// supports three file formats: text, binary and gcov.
//
// The textual representation is useful for debugging and testing purposes. The
// binary representation is more compact, resulting in smaller file sizes.
//
// The gcov encoding is the one generated by GCC's AutoFDO profile creation
// tool (https://github.com/google/autofdo)
//
// All three encodings can be used interchangeably as an input sample profile.
//
//===----------------------------------------------------------------------===//

#include "llvm/ProfileData/SampleProfReader.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/IR/ProfileSummary.h"
#include "llvm/ProfileData/ProfileCommon.h"
#include "llvm/ProfileData/SampleProf.h"
#include "llvm/Support/Compression.h"
#include "llvm/Support/ErrorOr.h"
#include "llvm/Support/LEB128.h"
#include "llvm/Support/LineIterator.h"
#include "llvm/Support/MD5.h"
#include "llvm/Support/MemoryBuffer.h"
#include "llvm/Support/raw_ostream.h"
#include <algorithm>
#include <cstddef>
#include <cstdint>
#include <limits>
#include <memory>
#include <set>
#include <system_error>
#include <vector>

using namespace llvm;
using namespace sampleprof;

/// Dump the function profile for \p FName.
///
/// \param FName Name of the function to print.
/// \param OS Stream to emit the output to.
void SampleProfileReader::dumpFunctionProfile(StringRef FName,
                                              raw_ostream &OS) {
  OS << "Function: " << FName << ": " << Profiles[FName];
}

/// Dump all the function profiles found on stream \p OS.
void SampleProfileReader::dump(raw_ostream &OS) {
  for (const auto &I : Profiles)
    dumpFunctionProfile(I.getKey(), OS);
}

/// Parse \p Input as function head.
///
/// Parse one line of \p Input, and update function name in \p FName,
/// function's total sample count in \p NumSamples, function's entry
/// count in \p NumHeadSamples.
///
/// \returns true if parsing is successful.
static bool ParseHead(const StringRef &Input, StringRef &FName,
                      uint64_t &NumSamples, uint64_t &NumHeadSamples) {
  if (Input[0] == ' ')
    return false;
  size_t n2 = Input.rfind(':');
  size_t n1 = Input.rfind(':', n2 - 1);
  FName = Input.substr(0, n1);
  if (Input.substr(n1 + 1, n2 - n1 - 1).getAsInteger(10, NumSamples))
    return false;
  if (Input.substr(n2 + 1).getAsInteger(10, NumHeadSamples))
    return false;
  return true;
}

/// Returns true if line offset \p L is legal (only has 16 bits).
static bool isOffsetLegal(unsigned L) { return (L & 0xffff) == L; }

/// Parse \p Input that contains metadata.
/// Possible metadata:
/// - CFG Checksum information:
///     !CFGChecksum: 12345
/// Stores the FunctionHash (a.k.a. CFG Checksum) into \p FunctionHash.
static bool parseMetadata(const StringRef &Input, uint64_t &FunctionHash) {
  if (!Input.startswith("!CFGChecksum:"))
    return false;

  StringRef CFGInfo = Input.substr(strlen("!CFGChecksum:")).trim();
  return !CFGInfo.getAsInteger(10, FunctionHash);
}

enum class LineType {
  CallSiteProfile,
  BodyProfile,
  Metadata,
};

/// Parse \p Input as line sample.
///
/// \param Input input line.
/// \param LineTy Type of this line.
/// \param Depth the depth of the inline stack.
/// \param NumSamples total samples of the line/inlined callsite.
/// \param LineOffset line offset to the start of the function.
/// \param Discriminator discriminator of the line.
/// \param TargetCountMap map from indirect call target to count.
/// \param FunctionHash the function's CFG hash, used by pseudo probe.
///
/// returns true if parsing is successful.
static bool ParseLine(const StringRef &Input, LineType &LineTy, uint32_t &Depth,
                      uint64_t &NumSamples, uint32_t &LineOffset,
                      uint32_t &Discriminator, StringRef &CalleeName,
                      DenseMap<StringRef, uint64_t> &TargetCountMap,
                      uint64_t &FunctionHash) {
  for (Depth = 0; Input[Depth] == ' '; Depth++)
    ;
  if (Depth == 0)
    return false;

  if (Depth == 1 && Input[Depth] == '!') {
    LineTy = LineType::Metadata;
    return parseMetadata(Input.substr(Depth), FunctionHash);
  }

  size_t n1 = Input.find(':');
  StringRef Loc = Input.substr(Depth, n1 - Depth);
  size_t n2 = Loc.find('.');
  if (n2 == StringRef::npos) {
    if (Loc.getAsInteger(10, LineOffset) || !isOffsetLegal(LineOffset))
      return false;
    Discriminator = 0;
  } else {
    if (Loc.substr(0, n2).getAsInteger(10, LineOffset))
      return false;
    if (Loc.substr(n2 + 1).getAsInteger(10, Discriminator))
      return false;
  }

  StringRef Rest = Input.substr(n1 + 2);
  if (isDigit(Rest[0])) {
    LineTy = LineType::BodyProfile;
    size_t n3 = Rest.find(' ');
    if (n3 == StringRef::npos) {
      if (Rest.getAsInteger(10, NumSamples))
        return false;
    } else {
      if (Rest.substr(0, n3).getAsInteger(10, NumSamples))
        return false;
    }
    // Find call targets and their sample counts.
    // Note: In some cases, there are symbols in the profile which are not
    // mangled. To accommodate such cases, use colon + integer pairs as the
    // anchor points.
    // An example:
    // _M_construct<char *>:1000 string_view<std::allocator<char> >:437
    // ":1000" and ":437" are used as anchor points so the string above will
    // be interpreted as
    // target: _M_construct<char *>
    // count: 1000
    // target: string_view<std::allocator<char> >
    // count: 437
    while (n3 != StringRef::npos) {
      n3 += Rest.substr(n3).find_first_not_of(' ');
      Rest = Rest.substr(n3);
      n3 = Rest.find_first_of(':');
      if (n3 == StringRef::npos || n3 == 0)
        return false;

      StringRef Target;
      uint64_t count, n4;
      while (true) {
        // Get the segment after the current colon.
        StringRef AfterColon = Rest.substr(n3 + 1);
        // Get the target symbol before the current colon.
        Target = Rest.substr(0, n3);
        // Check if the word after the current colon is an integer.
        n4 = AfterColon.find_first_of(' ');
        n4 = (n4 != StringRef::npos) ? n3 + n4 + 1 : Rest.size();
        StringRef WordAfterColon = Rest.substr(n3 + 1, n4 - n3 - 1);
        if (!WordAfterColon.getAsInteger(10, count))
          break;

        // Try to find the next colon.
        uint64_t n5 = AfterColon.find_first_of(':');
        if (n5 == StringRef::npos)
          return false;
        n3 += n5 + 1;
      }

      // An anchor point is found. Save the {target, count} pair
      TargetCountMap[Target] = count;
      if (n4 == Rest.size())
        break;
      // Change n3 to the next blank space after colon + integer pair.
      n3 = n4;
    }
  } else {
    LineTy = LineType::CallSiteProfile;
    size_t n3 = Rest.find_last_of(':');
    CalleeName = Rest.substr(0, n3);
    if (Rest.substr(n3 + 1).getAsInteger(10, NumSamples))
      return false;
  }
  return true;
}

/// Load samples from a text file.
///
/// See the documentation at the top of the file for an explanation of
/// the expected format.
///
/// \returns true if the file was loaded successfully, false otherwise.
std::error_code SampleProfileReaderText::readImpl() {
  line_iterator LineIt(*Buffer, /*SkipBlanks=*/true, '#');
  sampleprof_error Result = sampleprof_error::success;

  InlineCallStack InlineStack;
  uint32_t ProbeProfileCount = 0;

  // SeenMetadata tracks whether we have processed metadata for the current
  // top-level function profile.
  bool SeenMetadata = false;

  for (; !LineIt.is_at_eof(); ++LineIt) {
    if ((*LineIt)[(*LineIt).find_first_not_of(' ')] == '#')
      continue;
    // Read the header of each function.
    //
    // Note that for function identifiers we are actually expecting
    // mangled names, but we may not always get them. This happens when
    // the compiler decides not to emit the function (e.g., it was inlined
    // and removed). In this case, the binary will not have the linkage
    // name for the function, so the profiler will emit the function's
    // unmangled name, which may contain characters like ':' and '>' in its
    // name (member functions, templates, etc).
    //
    // The only requirement we place on the identifier, then, is that it
    // should not begin with a number.
    if ((*LineIt)[0] != ' ') {
      uint64_t NumSamples, NumHeadSamples;
      StringRef FName;
      if (!ParseHead(*LineIt, FName, NumSamples, NumHeadSamples)) {
        reportError(LineIt.line_number(),
                    "Expected 'mangled_name:NUM:NUM', found " + *LineIt);
        return sampleprof_error::malformed;
      }
      SeenMetadata = false;
      SampleContext FContext(FName);
      if (FContext.hasContext())
        ++CSProfileCount;
      Profiles[FContext] = FunctionSamples();
      FunctionSamples &FProfile = Profiles[FContext];
      FProfile.setName(FContext.getNameWithoutContext());
      FProfile.setContext(FContext);
      MergeResult(Result, FProfile.addTotalSamples(NumSamples));
      MergeResult(Result, FProfile.addHeadSamples(NumHeadSamples));
      InlineStack.clear();
      InlineStack.push_back(&FProfile);
    } else {
      uint64_t NumSamples;
      StringRef FName;
      DenseMap<StringRef, uint64_t> TargetCountMap;
      uint32_t Depth, LineOffset, Discriminator;
      LineType LineTy;
      uint64_t FunctionHash;
      if (!ParseLine(*LineIt, LineTy, Depth, NumSamples, LineOffset,
                     Discriminator, FName, TargetCountMap, FunctionHash)) {
        reportError(LineIt.line_number(),
                    "Expected 'NUM[.NUM]: NUM[ mangled_name:NUM]*', found " +
                        *LineIt);
        return sampleprof_error::malformed;
      }
      if (SeenMetadata && LineTy != LineType::Metadata) {
        // Metadata must be put at the end of a function profile.
        reportError(LineIt.line_number(),
                    "Found non-metadata after metadata: " + *LineIt);
        return sampleprof_error::malformed;
      }
      while (InlineStack.size() > Depth) {
        InlineStack.pop_back();
      }
      switch (LineTy) {
      case LineType::CallSiteProfile: {
        FunctionSamples &FSamples = InlineStack.back()->functionSamplesAt(
            LineLocation(LineOffset, Discriminator))[std::string(FName)];
        FSamples.setName(FName);
        MergeResult(Result, FSamples.addTotalSamples(NumSamples));
        InlineStack.push_back(&FSamples);
        break;
      }
      case LineType::BodyProfile: {
        while (InlineStack.size() > Depth) {
          InlineStack.pop_back();
        }
        FunctionSamples &FProfile = *InlineStack.back();
        for (const auto &name_count : TargetCountMap) {
          MergeResult(Result, FProfile.addCalledTargetSamples(
                                  LineOffset, Discriminator, name_count.first,
                                  name_count.second));
        }
        MergeResult(Result, FProfile.addBodySamples(LineOffset, Discriminator,
                                                    NumSamples));
        break;
      }
      case LineType::Metadata: {
        FunctionSamples &FProfile = *InlineStack.back();
        FProfile.setFunctionHash(FunctionHash);
        ++ProbeProfileCount;
        SeenMetadata = true;
        break;
      }
      }
    }
  }

  assert((CSProfileCount == 0 || CSProfileCount == Profiles.size()) &&
         "Cannot have both context-sensitive and regular profile");
  ProfileIsCS = (CSProfileCount > 0);
  assert((ProbeProfileCount == 0 || ProbeProfileCount == Profiles.size()) &&
         "Cannot have both probe-based profiles and regular profiles");
  ProfileIsProbeBased = (ProbeProfileCount > 0);
  FunctionSamples::ProfileIsProbeBased = ProfileIsProbeBased;
  FunctionSamples::ProfileIsCS = ProfileIsCS;

  if (Result == sampleprof_error::success)
    computeSummary();

  return Result;
}

bool SampleProfileReaderText::hasFormat(const MemoryBuffer &Buffer) {
  bool result = false;

  // Check that the first non-comment line is a valid function header.
  line_iterator LineIt(Buffer, /*SkipBlanks=*/true, '#');
  if (!LineIt.is_at_eof()) {
    if ((*LineIt)[0] != ' ') {
      uint64_t NumSamples, NumHeadSamples;
      StringRef FName;
      result = ParseHead(*LineIt, FName, NumSamples, NumHeadSamples);
    }
  }

  return result;
}

template <typename T> ErrorOr<T> SampleProfileReaderBinary::readNumber() {
  unsigned NumBytesRead = 0;
  std::error_code EC;
  uint64_t Val = decodeULEB128(Data, &NumBytesRead);

  if (Val > std::numeric_limits<T>::max())
    EC = sampleprof_error::malformed;
  else if (Data + NumBytesRead > End)
    EC = sampleprof_error::truncated;
  else
    EC = sampleprof_error::success;

  if (EC) {
    reportError(0, EC.message());
    return EC;
  }

  Data += NumBytesRead;
  return static_cast<T>(Val);
}

ErrorOr<StringRef> SampleProfileReaderBinary::readString() {
  std::error_code EC;
  StringRef Str(reinterpret_cast<const char *>(Data));
  if (Data + Str.size() + 1 > End) {
    EC = sampleprof_error::truncated;
    reportError(0, EC.message());
    return EC;
  }

  Data += Str.size() + 1;
  return Str;
}

template <typename T>
ErrorOr<T> SampleProfileReaderBinary::readUnencodedNumber() {
  std::error_code EC;

  if (Data + sizeof(T) > End) {
    EC = sampleprof_error::truncated;
    reportError(0, EC.message());
    return EC;
  }

  using namespace support;
  T Val = endian::readNext<T, little, unaligned>(Data);
  return Val;
}

template <typename T>
inline ErrorOr<uint32_t> SampleProfileReaderBinary::readStringIndex(T &Table) {
  std::error_code EC;
  auto Idx = readNumber<uint32_t>();
  if (std::error_code EC = Idx.getError())
    return EC;
  if (*Idx >= Table.size())
    return sampleprof_error::truncated_name_table;
  return *Idx;
}

ErrorOr<StringRef> SampleProfileReaderBinary::readStringFromTable() {
  auto Idx = readStringIndex(NameTable);
  if (std::error_code EC = Idx.getError())
    return EC;

  return NameTable[*Idx];
}

ErrorOr<StringRef> SampleProfileReaderExtBinaryBase::readStringFromTable() {
  if (!FixedLengthMD5)
    return SampleProfileReaderBinary::readStringFromTable();

  // read NameTable index.
  auto Idx = readStringIndex(NameTable);
  if (std::error_code EC = Idx.getError())
    return EC;

  // Check whether the name to be accessed has been accessed before,
  // if not, read it from memory directly.
  StringRef &SR = NameTable[*Idx];
  if (SR.empty()) {
    const uint8_t *SavedData = Data;
    Data = MD5NameMemStart + ((*Idx) * sizeof(uint64_t));
    auto FID = readUnencodedNumber<uint64_t>();
    if (std::error_code EC = FID.getError())
      return EC;
    // Save the string converted from uint64_t in MD5StringBuf. All the
    // references to the name are all StringRefs refering to the string
    // in MD5StringBuf.
    MD5StringBuf->push_back(std::to_string(*FID));
    SR = MD5StringBuf->back();
    Data = SavedData;
  }
  return SR;
}

ErrorOr<StringRef> SampleProfileReaderCompactBinary::readStringFromTable() {
  auto Idx = readStringIndex(NameTable);
  if (std::error_code EC = Idx.getError())
    return EC;

  return StringRef(NameTable[*Idx]);
}

std::error_code
SampleProfileReaderBinary::readProfile(FunctionSamples &FProfile) {
  auto NumSamples = readNumber<uint64_t>();
  if (std::error_code EC = NumSamples.getError())
    return EC;
  FProfile.addTotalSamples(*NumSamples);

  // Read the samples in the body.
  auto NumRecords = readNumber<uint32_t>();
  if (std::error_code EC = NumRecords.getError())
    return EC;

  for (uint32_t I = 0; I < *NumRecords; ++I) {
    auto LineOffset = readNumber<uint64_t>();
    if (std::error_code EC = LineOffset.getError())
      return EC;

    if (!isOffsetLegal(*LineOffset)) {
      return std::error_code();
    }

    auto Discriminator = readNumber<uint64_t>();
    if (std::error_code EC = Discriminator.getError())
      return EC;

    auto NumSamples = readNumber<uint64_t>();
    if (std::error_code EC = NumSamples.getError())
      return EC;

    auto NumCalls = readNumber<uint32_t>();
    if (std::error_code EC = NumCalls.getError())
      return EC;

    for (uint32_t J = 0; J < *NumCalls; ++J) {
      auto CalledFunction(readStringFromTable());
      if (std::error_code EC = CalledFunction.getError())
        return EC;

      auto CalledFunctionSamples = readNumber<uint64_t>();
      if (std::error_code EC = CalledFunctionSamples.getError())
        return EC;

      FProfile.addCalledTargetSamples(*LineOffset, *Discriminator,
                                      *CalledFunction, *CalledFunctionSamples);
    }

    FProfile.addBodySamples(*LineOffset, *Discriminator, *NumSamples);
  }

  // Read all the samples for inlined function calls.
  auto NumCallsites = readNumber<uint32_t>();
  if (std::error_code EC = NumCallsites.getError())
    return EC;

  for (uint32_t J = 0; J < *NumCallsites; ++J) {
    auto LineOffset = readNumber<uint64_t>();
    if (std::error_code EC = LineOffset.getError())
      return EC;

    auto Discriminator = readNumber<uint64_t>();
    if (std::error_code EC = Discriminator.getError())
      return EC;

    auto FName(readStringFromTable());
    if (std::error_code EC = FName.getError())
      return EC;

    FunctionSamples &CalleeProfile = FProfile.functionSamplesAt(
        LineLocation(*LineOffset, *Discriminator))[std::string(*FName)];
    CalleeProfile.setName(*FName);
    if (std::error_code EC = readProfile(CalleeProfile))
      return EC;
  }

  return sampleprof_error::success;
}

std::error_code
SampleProfileReaderBinary::readFuncProfile(const uint8_t *Start) {
  Data = Start;
  auto NumHeadSamples = readNumber<uint64_t>();
  if (std::error_code EC = NumHeadSamples.getError())
    return EC;

  auto FName(readStringFromTable());
  if (std::error_code EC = FName.getError())
    return EC;

  SampleContext FContext(*FName);
  Profiles[FContext] = FunctionSamples();
  FunctionSamples &FProfile = Profiles[FContext];
  FProfile.setName(FContext.getNameWithoutContext());
  FProfile.setContext(FContext);
  FProfile.addHeadSamples(*NumHeadSamples);

  if (FContext.hasContext())
    CSProfileCount++;

  if (std::error_code EC = readProfile(FProfile))
    return EC;
  return sampleprof_error::success;
}

std::error_code SampleProfileReaderBinary::readImpl() {
  while (!at_eof()) {
    if (std::error_code EC = readFuncProfile(Data))
      return EC;
  }

  return sampleprof_error::success;
}

std::error_code SampleProfileReaderExtBinaryBase::readOneSection(
    const uint8_t *Start, uint64_t Size, const SecHdrTableEntry &Entry) {
  Data = Start;
  End = Start + Size;
  switch (Entry.Type) {
  case SecProfSummary:
    if (std::error_code EC = readSummary())
      return EC;
    if (hasSecFlag(Entry, SecProfSummaryFlags::SecFlagPartial))
      Summary->setPartialProfile(true);
    if (hasSecFlag(Entry, SecProfSummaryFlags::SecFlagFullContext))
      FunctionSamples::ProfileIsCS = ProfileIsCS = true;
    break;
  case SecNameTable: {
    FixedLengthMD5 =
        hasSecFlag(Entry, SecNameTableFlags::SecFlagFixedLengthMD5);
    bool UseMD5 = hasSecFlag(Entry, SecNameTableFlags::SecFlagMD5Name);
    assert((!FixedLengthMD5 || UseMD5) &&
           "If FixedLengthMD5 is true, UseMD5 has to be true");
    FunctionSamples::HasUniqSuffix =
        hasSecFlag(Entry, SecNameTableFlags::SecFlagUniqSuffix);
    if (std::error_code EC = readNameTableSec(UseMD5))
      return EC;
    break;
  }
  case SecLBRProfile:
    if (std::error_code EC = readFuncProfiles())
      return EC;
    break;
  case SecFuncOffsetTable:
    if (std::error_code EC = readFuncOffsetTable())
      return EC;
    break;
  case SecFuncMetadata:
    ProfileIsProbeBased =
        hasSecFlag(Entry, SecFuncMetadataFlags::SecFlagIsProbeBased);
    FunctionSamples::ProfileIsProbeBased = ProfileIsProbeBased;
    if (std::error_code EC = readFuncMetadata())
      return EC;
    break;
  case SecProfileSymbolList:
    if (std::error_code EC = readProfileSymbolList())
      return EC;
    break;
  default:
    if (std::error_code EC = readCustomSection(Entry))
      return EC;
    break;
  }
  return sampleprof_error::success;
}

bool SampleProfileReaderExtBinaryBase::collectFuncsFromModule() {
  if (!M)
    return false;
  FuncsToUse.clear();
  for (auto &F : *M)
    FuncsToUse.insert(FunctionSamples::getCanonicalFnName(F));
  return true;
}

std::error_code SampleProfileReaderExtBinaryBase::readFuncOffsetTable() {
  // If there are more than one FuncOffsetTable, the profile read associated
  // with previous FuncOffsetTable has to be done before next FuncOffsetTable
  // is read.
  FuncOffsetTable.clear();

  auto Size = readNumber<uint64_t>();
  if (std::error_code EC = Size.getError())
    return EC;

  FuncOffsetTable.reserve(*Size);
  for (uint32_t I = 0; I < *Size; ++I) {
    auto FName(readStringFromTable());
    if (std::error_code EC = FName.getError())
      return EC;

    auto Offset = readNumber<uint64_t>();
    if (std::error_code EC = Offset.getError())
      return EC;

    FuncOffsetTable[*FName] = *Offset;
  }
  return sampleprof_error::success;
}

std::error_code SampleProfileReaderExtBinaryBase::readFuncProfiles() {
  // Collect functions used by current module if the Reader has been
  // given a module.
  // collectFuncsFromModule uses FunctionSamples::getCanonicalFnName
  // which will query FunctionSamples::HasUniqSuffix, so it has to be
  // called after FunctionSamples::HasUniqSuffix is set, i.e. after
  // NameTable section is read.
  bool LoadFuncsToBeUsed = collectFuncsFromModule();

  // When LoadFuncsToBeUsed is false, load all the function profiles.
  const uint8_t *Start = Data;
  if (!LoadFuncsToBeUsed) {
    while (Data < End) {
      if (std::error_code EC = readFuncProfile(Data))
        return EC;
    }
    assert(Data == End && "More data is read than expected");
  } else {
    // Load function profiles on demand.
    if (Remapper) {
      for (auto Name : FuncsToUse) {
        Remapper->insert(Name);
      }
    }

    if (useMD5()) {
      for (auto Name : FuncsToUse) {
        auto GUID = std::to_string(MD5Hash(Name));
        auto iter = FuncOffsetTable.find(StringRef(GUID));
        if (iter == FuncOffsetTable.end())
          continue;
        const uint8_t *FuncProfileAddr = Start + iter->second;
        assert(FuncProfileAddr < End && "out of LBRProfile section");
        if (std::error_code EC = readFuncProfile(FuncProfileAddr))
          return EC;
      }
    } else if (FunctionSamples::ProfileIsCS) {
      // Compute the ordered set of names, so we can
      // get all context profiles under a subtree by
      // iterating through the ordered names.
      struct Comparer {
        // Ignore the closing ']' when ordering context
        bool operator()(const StringRef &L, const StringRef &R) const {
          return L.substr(0, L.size() - 1) < R.substr(0, R.size() - 1);
        }
      };
      std::set<StringRef, Comparer> OrderedNames;
      for (auto Name : FuncOffsetTable) {
        OrderedNames.insert(Name.first);
      }

      // For each function in current module, load all
      // context profiles for the function.
      for (auto NameOffset : FuncOffsetTable) {
        StringRef ContextName = NameOffset.first;
        SampleContext FContext(ContextName);
        auto FuncName = FContext.getNameWithoutContext();
        if (!FuncsToUse.count(FuncName) &&
            (!Remapper || !Remapper->exist(FuncName)))
          continue;

        // For each context profile we need, try to load
        // all context profile in the subtree. This can
        // help profile guided importing for ThinLTO.
        auto It = OrderedNames.find(ContextName);
        while (It != OrderedNames.end() &&
               It->startswith(ContextName.substr(0, ContextName.size() - 1))) {
          const uint8_t *FuncProfileAddr = Start + FuncOffsetTable[*It];
          assert(FuncProfileAddr < End && "out of LBRProfile section");
          if (std::error_code EC = readFuncProfile(FuncProfileAddr))
            return EC;
          // Remove loaded context profile so we won't
          // load it repeatedly.
          It = OrderedNames.erase(It);
        }
      }
    } else {
      for (auto NameOffset : FuncOffsetTable) {
        SampleContext FContext(NameOffset.first);
        auto FuncName = FContext.getNameWithoutContext();
        if (!FuncsToUse.count(FuncName) &&
            (!Remapper || !Remapper->exist(FuncName)))
          continue;
        const uint8_t *FuncProfileAddr = Start + NameOffset.second;
        assert(FuncProfileAddr < End && "out of LBRProfile section");
        if (std::error_code EC = readFuncProfile(FuncProfileAddr))
          return EC;
      }
    }
    Data = End;
  }
  assert((CSProfileCount == 0 || CSProfileCount == Profiles.size()) &&
         "Cannot have both context-sensitive and regular profile");
  assert(ProfileIsCS == (CSProfileCount > 0) &&
         "Section flag should be consistent with actual profile");
  return sampleprof_error::success;
}

std::error_code SampleProfileReaderExtBinaryBase::readProfileSymbolList() {
  if (!ProfSymList)
    ProfSymList = std::make_unique<ProfileSymbolList>();

  if (std::error_code EC = ProfSymList->read(Data, End - Data))
    return EC;

  Data = End;
  return sampleprof_error::success;
}

std::error_code SampleProfileReaderExtBinaryBase::decompressSection(
    const uint8_t *SecStart, const uint64_t SecSize,
    const uint8_t *&DecompressBuf, uint64_t &DecompressBufSize) {
  Data = SecStart;
  End = SecStart + SecSize;
  auto DecompressSize = readNumber<uint64_t>();
  if (std::error_code EC = DecompressSize.getError())
    return EC;
  DecompressBufSize = *DecompressSize;

  auto CompressSize = readNumber<uint64_t>();
  if (std::error_code EC = CompressSize.getError())
    return EC;

  if (!llvm::zlib::isAvailable())
    return sampleprof_error::zlib_unavailable;

  StringRef CompressedStrings(reinterpret_cast<const char *>(Data),
                              *CompressSize);
  char *Buffer = Allocator.Allocate<char>(DecompressBufSize);
  size_t UCSize = DecompressBufSize;
  llvm::Error E =
      zlib::uncompress(CompressedStrings, Buffer, UCSize);
  if (E)
    return sampleprof_error::uncompress_failed;
  DecompressBuf = reinterpret_cast<const uint8_t *>(Buffer);
  return sampleprof_error::success;
}

std::error_code SampleProfileReaderExtBinaryBase::readImpl() {
  const uint8_t *BufStart =
      reinterpret_cast<const uint8_t *>(Buffer->getBufferStart());

  for (auto &Entry : SecHdrTable) {
    // Skip empty section.
    if (!Entry.Size)
      continue;

    // Skip sections without context when SkipFlatProf is true.
    if (SkipFlatProf && hasSecFlag(Entry, SecCommonFlags::SecFlagFlat))
      continue;

    const uint8_t *SecStart = BufStart + Entry.Offset;
    uint64_t SecSize = Entry.Size;

    // If the section is compressed, decompress it into a buffer
    // DecompressBuf before reading the actual data. The pointee of
    // 'Data' will be changed to buffer hold by DecompressBuf
    // temporarily when reading the actual data.
    bool isCompressed = hasSecFlag(Entry, SecCommonFlags::SecFlagCompress);
    if (isCompressed) {
      const uint8_t *DecompressBuf;
      uint64_t DecompressBufSize;
      if (std::error_code EC = decompressSection(
              SecStart, SecSize, DecompressBuf, DecompressBufSize))
        return EC;
      SecStart = DecompressBuf;
      SecSize = DecompressBufSize;
    }

    if (std::error_code EC = readOneSection(SecStart, SecSize, Entry))
      return EC;
    if (Data != SecStart + SecSize)
      return sampleprof_error::malformed;

    // Change the pointee of 'Data' from DecompressBuf to original Buffer.
    if (isCompressed) {
      Data = BufStart + Entry.Offset;
      End = BufStart + Buffer->getBufferSize();
    }
  }

  return sampleprof_error::success;
}

std::error_code SampleProfileReaderCompactBinary::readImpl() {
  // Collect functions used by current module if the Reader has been
  // given a module.
  bool LoadFuncsToBeUsed = collectFuncsFromModule();

  std::vector<uint64_t> OffsetsToUse;
  if (!LoadFuncsToBeUsed) {
    // load all the function profiles.
    for (auto FuncEntry : FuncOffsetTable) {
      OffsetsToUse.push_back(FuncEntry.second);
    }
  } else {
    // load function profiles on demand.
    for (auto Name : FuncsToUse) {
      auto GUID = std::to_string(MD5Hash(Name));
      auto iter = FuncOffsetTable.find(StringRef(GUID));
      if (iter == FuncOffsetTable.end())
        continue;
      OffsetsToUse.push_back(iter->second);
    }
  }

  for (auto Offset : OffsetsToUse) {
    const uint8_t *SavedData = Data;
    if (std::error_code EC = readFuncProfile(
            reinterpret_cast<const uint8_t *>(Buffer->getBufferStart()) +
            Offset))
      return EC;
    Data = SavedData;
  }
  return sampleprof_error::success;
}

std::error_code SampleProfileReaderRawBinary::verifySPMagic(uint64_t Magic) {
  if (Magic == SPMagic())
    return sampleprof_error::success;
  return sampleprof_error::bad_magic;
}

std::error_code SampleProfileReaderExtBinary::verifySPMagic(uint64_t Magic) {
  if (Magic == SPMagic(SPF_Ext_Binary))
    return sampleprof_error::success;
  return sampleprof_error::bad_magic;
}

std::error_code
SampleProfileReaderCompactBinary::verifySPMagic(uint64_t Magic) {
  if (Magic == SPMagic(SPF_Compact_Binary))
    return sampleprof_error::success;
  return sampleprof_error::bad_magic;
}

std::error_code SampleProfileReaderBinary::readNameTable() {
  auto Size = readNumber<uint32_t>();
  if (std::error_code EC = Size.getError())
    return EC;
  NameTable.reserve(*Size + NameTable.size());
  for (uint32_t I = 0; I < *Size; ++I) {
    auto Name(readString());
    if (std::error_code EC = Name.getError())
      return EC;
    NameTable.push_back(*Name);
  }

  return sampleprof_error::success;
}

std::error_code SampleProfileReaderExtBinaryBase::readMD5NameTable() {
  auto Size = readNumber<uint64_t>();
  if (std::error_code EC = Size.getError())
    return EC;
  MD5StringBuf = std::make_unique<std::vector<std::string>>();
  MD5StringBuf->reserve(*Size);
  if (FixedLengthMD5) {
    // Preallocate and initialize NameTable so we can check whether a name
    // index has been read before by checking whether the element in the
    // NameTable is empty, meanwhile readStringIndex can do the boundary
    // check using the size of NameTable.
    NameTable.resize(*Size + NameTable.size());

    MD5NameMemStart = Data;
    Data = Data + (*Size) * sizeof(uint64_t);
    return sampleprof_error::success;
  }
  NameTable.reserve(*Size);
  for (uint32_t I = 0; I < *Size; ++I) {
    auto FID = readNumber<uint64_t>();
    if (std::error_code EC = FID.getError())
      return EC;
    MD5StringBuf->push_back(std::to_string(*FID));
    // NameTable is a vector of StringRef. Here it is pushing back a
    // StringRef initialized with the last string in MD5stringBuf.
    NameTable.push_back(MD5StringBuf->back());
  }
  return sampleprof_error::success;
}

std::error_code SampleProfileReaderExtBinaryBase::readNameTableSec(bool IsMD5) {
  if (IsMD5)
    return readMD5NameTable();
  return SampleProfileReaderBinary::readNameTable();
}

std::error_code SampleProfileReaderExtBinaryBase::readFuncMetadata() {
  if (!ProfileIsProbeBased)
    return sampleprof_error::success;
  while (Data < End) {
    auto FName(readStringFromTable());
    if (std::error_code EC = FName.getError())
      return EC;

    auto Checksum = readNumber<uint64_t>();
    if (std::error_code EC = Checksum.getError())
      return EC;

    SampleContext FContext(*FName);
    // No need to load metadata for profiles that are not loaded in the current
    // module.
    if (Profiles.count(FContext))
      Profiles[FContext].setFunctionHash(*Checksum);
  }

  assert(Data == End && "More data is read than expected");
  return sampleprof_error::success;
}

std::error_code SampleProfileReaderCompactBinary::readNameTable() {
  auto Size = readNumber<uint64_t>();
  if (std::error_code EC = Size.getError())
    return EC;
  NameTable.reserve(*Size);
  for (uint32_t I = 0; I < *Size; ++I) {
    auto FID = readNumber<uint64_t>();
    if (std::error_code EC = FID.getError())
      return EC;
    NameTable.push_back(std::to_string(*FID));
  }
  return sampleprof_error::success;
}

std::error_code
SampleProfileReaderExtBinaryBase::readSecHdrTableEntry(uint32_t Idx) {
  SecHdrTableEntry Entry;
  auto Type = readUnencodedNumber<uint64_t>();
  if (std::error_code EC = Type.getError())
    return EC;
  Entry.Type = static_cast<SecType>(*Type);

  auto Flags = readUnencodedNumber<uint64_t>();
  if (std::error_code EC = Flags.getError())
    return EC;
  Entry.Flags = *Flags;

  auto Offset = readUnencodedNumber<uint64_t>();
  if (std::error_code EC = Offset.getError())
    return EC;
  Entry.Offset = *Offset;

  auto Size = readUnencodedNumber<uint64_t>();
  if (std::error_code EC = Size.getError())
    return EC;
  Entry.Size = *Size;

  Entry.LayoutIndex = Idx;
  SecHdrTable.push_back(std::move(Entry));
  return sampleprof_error::success;
}

std::error_code SampleProfileReaderExtBinaryBase::readSecHdrTable() {
  auto EntryNum = readUnencodedNumber<uint64_t>();
  if (std::error_code EC = EntryNum.getError())
    return EC;

  for (uint32_t i = 0; i < (*EntryNum); i++)
    if (std::error_code EC = readSecHdrTableEntry(i))
      return EC;

  return sampleprof_error::success;
}

std::error_code SampleProfileReaderExtBinaryBase::readHeader() {
  const uint8_t *BufStart =
      reinterpret_cast<const uint8_t *>(Buffer->getBufferStart());
  Data = BufStart;
  End = BufStart + Buffer->getBufferSize();

  if (std::error_code EC = readMagicIdent())
    return EC;

  if (std::error_code EC = readSecHdrTable())
    return EC;

  return sampleprof_error::success;
}

uint64_t SampleProfileReaderExtBinaryBase::getSectionSize(SecType Type) {
  uint64_t Size = 0;
  for (auto &Entry : SecHdrTable) {
    if (Entry.Type == Type)
      Size += Entry.Size;
  }
  return Size;
}

uint64_t SampleProfileReaderExtBinaryBase::getFileSize() {
  // Sections in SecHdrTable is not necessarily in the same order as
  // sections in the profile because section like FuncOffsetTable needs
  // to be written after section LBRProfile but needs to be read before
  // section LBRProfile, so we cannot simply use the last entry in
  // SecHdrTable to calculate the file size.
  uint64_t FileSize = 0;
  for (auto &Entry : SecHdrTable) {
    FileSize = std::max(Entry.Offset + Entry.Size, FileSize);
  }
  return FileSize;
}

static std::string getSecFlagsStr(const SecHdrTableEntry &Entry) {
  std::string Flags;
  if (hasSecFlag(Entry, SecCommonFlags::SecFlagCompress))
    Flags.append("{compressed,");
  else
    Flags.append("{");

  if (hasSecFlag(Entry, SecCommonFlags::SecFlagFlat))
    Flags.append("flat,");

  switch (Entry.Type) {
  case SecNameTable:
    if (hasSecFlag(Entry, SecNameTableFlags::SecFlagFixedLengthMD5))
      Flags.append("fixlenmd5,");
    else if (hasSecFlag(Entry, SecNameTableFlags::SecFlagMD5Name))
      Flags.append("md5,");
    if (hasSecFlag(Entry, SecNameTableFlags::SecFlagUniqSuffix))
      Flags.append("uniq,");
    break;
  case SecProfSummary:
    if (hasSecFlag(Entry, SecProfSummaryFlags::SecFlagPartial))
      Flags.append("partial,");
    if (hasSecFlag(Entry, SecProfSummaryFlags::SecFlagFullContext))
      Flags.append("context,");
    break;
  default:
    break;
  }
  char &last = Flags.back();
  if (last == ',')
    last = '}';
  else
    Flags.append("}");
  return Flags;
}

bool SampleProfileReaderExtBinaryBase::dumpSectionInfo(raw_ostream &OS) {
  uint64_t TotalSecsSize = 0;
  for (auto &Entry : SecHdrTable) {
    OS << getSecName(Entry.Type) << " - Offset: " << Entry.Offset
       << ", Size: " << Entry.Size << ", Flags: " << getSecFlagsStr(Entry)
       << "\n";
    ;
    TotalSecsSize += Entry.Size;
  }
  uint64_t HeaderSize = SecHdrTable.front().Offset;
  assert(HeaderSize + TotalSecsSize == getFileSize() &&
         "Size of 'header + sections' doesn't match the total size of profile");

  OS << "Header Size: " << HeaderSize << "\n";
  OS << "Total Sections Size: " << TotalSecsSize << "\n";
  OS << "File Size: " << getFileSize() << "\n";
  return true;
}

std::error_code SampleProfileReaderBinary::readMagicIdent() {
  // Read and check the magic identifier.
  auto Magic = readNumber<uint64_t>();
  if (std::error_code EC = Magic.getError())
    return EC;
  else if (std::error_code EC = verifySPMagic(*Magic))
    return EC;

  // Read the version number.
  auto Version = readNumber<uint64_t>();
  if (std::error_code EC = Version.getError())
    return EC;
  else if (*Version != SPVersion())
    return sampleprof_error::unsupported_version;

  return sampleprof_error::success;
}

std::error_code SampleProfileReaderBinary::readHeader() {
  Data = reinterpret_cast<const uint8_t *>(Buffer->getBufferStart());
  End = Data + Buffer->getBufferSize();

  if (std::error_code EC = readMagicIdent())
    return EC;

  if (std::error_code EC = readSummary())
    return EC;

  if (std::error_code EC = readNameTable())
    return EC;
  return sampleprof_error::success;
}

std::error_code SampleProfileReaderCompactBinary::readHeader() {
  SampleProfileReaderBinary::readHeader();
  if (std::error_code EC = readFuncOffsetTable())
    return EC;
  return sampleprof_error::success;
}

std::error_code SampleProfileReaderCompactBinary::readFuncOffsetTable() {
  auto TableOffset = readUnencodedNumber<uint64_t>();
  if (std::error_code EC = TableOffset.getError())
    return EC;

  const uint8_t *SavedData = Data;
  const uint8_t *TableStart =
      reinterpret_cast<const uint8_t *>(Buffer->getBufferStart()) +
      *TableOffset;
  Data = TableStart;

  auto Size = readNumber<uint64_t>();
  if (std::error_code EC = Size.getError())
    return EC;

  FuncOffsetTable.reserve(*Size);
  for (uint32_t I = 0; I < *Size; ++I) {
    auto FName(readStringFromTable());
    if (std::error_code EC = FName.getError())
      return EC;

    auto Offset = readNumber<uint64_t>();
    if (std::error_code EC = Offset.getError())
      return EC;

    FuncOffsetTable[*FName] = *Offset;
  }
  End = TableStart;
  Data = SavedData;
  return sampleprof_error::success;
}

bool SampleProfileReaderCompactBinary::collectFuncsFromModule() {
  if (!M)
    return false;
  FuncsToUse.clear();
  for (auto &F : *M)
    FuncsToUse.insert(FunctionSamples::getCanonicalFnName(F));
  return true;
}

std::error_code SampleProfileReaderBinary::readSummaryEntry(
    std::vector<ProfileSummaryEntry> &Entries) {
  auto Cutoff = readNumber<uint64_t>();
  if (std::error_code EC = Cutoff.getError())
    return EC;

  auto MinBlockCount = readNumber<uint64_t>();
  if (std::error_code EC = MinBlockCount.getError())
    return EC;

  auto NumBlocks = readNumber<uint64_t>();
  if (std::error_code EC = NumBlocks.getError())
    return EC;

  Entries.emplace_back(*Cutoff, *MinBlockCount, *NumBlocks);
  return sampleprof_error::success;
}

std::error_code SampleProfileReaderBinary::readSummary() {
  auto TotalCount = readNumber<uint64_t>();
  if (std::error_code EC = TotalCount.getError())
    return EC;

  auto MaxBlockCount = readNumber<uint64_t>();
  if (std::error_code EC = MaxBlockCount.getError())
    return EC;

  auto MaxFunctionCount = readNumber<uint64_t>();
  if (std::error_code EC = MaxFunctionCount.getError())
    return EC;

  auto NumBlocks = readNumber<uint64_t>();
  if (std::error_code EC = NumBlocks.getError())
    return EC;

  auto NumFunctions = readNumber<uint64_t>();
  if (std::error_code EC = NumFunctions.getError())
    return EC;

  auto NumSummaryEntries = readNumber<uint64_t>();
  if (std::error_code EC = NumSummaryEntries.getError())
    return EC;

  std::vector<ProfileSummaryEntry> Entries;
  for (unsigned i = 0; i < *NumSummaryEntries; i++) {
    std::error_code EC = readSummaryEntry(Entries);
    if (EC != sampleprof_error::success)
      return EC;
  }
  Summary = std::make_unique<ProfileSummary>(
      ProfileSummary::PSK_Sample, Entries, *TotalCount, *MaxBlockCount, 0,
      *MaxFunctionCount, *NumBlocks, *NumFunctions);

  return sampleprof_error::success;
}

bool SampleProfileReaderRawBinary::hasFormat(const MemoryBuffer &Buffer) {
  const uint8_t *Data =
      reinterpret_cast<const uint8_t *>(Buffer.getBufferStart());
  uint64_t Magic = decodeULEB128(Data);
  return Magic == SPMagic();
}

bool SampleProfileReaderExtBinary::hasFormat(const MemoryBuffer &Buffer) {
  const uint8_t *Data =
      reinterpret_cast<const uint8_t *>(Buffer.getBufferStart());
  uint64_t Magic = decodeULEB128(Data);
  return Magic == SPMagic(SPF_Ext_Binary);
}

bool SampleProfileReaderCompactBinary::hasFormat(const MemoryBuffer &Buffer) {
  const uint8_t *Data =
      reinterpret_cast<const uint8_t *>(Buffer.getBufferStart());
  uint64_t Magic = decodeULEB128(Data);
  return Magic == SPMagic(SPF_Compact_Binary);
}

std::error_code SampleProfileReaderGCC::skipNextWord() {
  uint32_t dummy;
  if (!GcovBuffer.readInt(dummy))
    return sampleprof_error::truncated;
  return sampleprof_error::success;
}

template <typename T> ErrorOr<T> SampleProfileReaderGCC::readNumber() {
  if (sizeof(T) <= sizeof(uint32_t)) {
    uint32_t Val;
    if (GcovBuffer.readInt(Val) && Val <= std::numeric_limits<T>::max())
      return static_cast<T>(Val);
  } else if (sizeof(T) <= sizeof(uint64_t)) {
    uint64_t Val;
    if (GcovBuffer.readInt64(Val) && Val <= std::numeric_limits<T>::max())
      return static_cast<T>(Val);
  }

  std::error_code EC = sampleprof_error::malformed;
  reportError(0, EC.message());
  return EC;
}

ErrorOr<StringRef> SampleProfileReaderGCC::readString() {
  StringRef Str;
  if (!GcovBuffer.readString(Str))
    return sampleprof_error::truncated;
  return Str;
}

std::error_code SampleProfileReaderGCC::readHeader() {
  // Read the magic identifier.
  if (!GcovBuffer.readGCDAFormat())
    return sampleprof_error::unrecognized_format;

  // Read the version number. Note - the GCC reader does not validate this
  // version, but the profile creator generates v704.
  GCOV::GCOVVersion version;
  if (!GcovBuffer.readGCOVVersion(version))
    return sampleprof_error::unrecognized_format;

  if (version != GCOV::V407)
    return sampleprof_error::unsupported_version;

  // Skip the empty integer.
  if (std::error_code EC = skipNextWord())
    return EC;

  return sampleprof_error::success;
}

std::error_code SampleProfileReaderGCC::readSectionTag(uint32_t Expected) {
  uint32_t Tag;
  if (!GcovBuffer.readInt(Tag))
    return sampleprof_error::truncated;

  if (Tag != Expected)
    return sampleprof_error::malformed;

  if (std::error_code EC = skipNextWord())
    return EC;

  return sampleprof_error::success;
}

std::error_code SampleProfileReaderGCC::readNameTable() {
  if (std::error_code EC = readSectionTag(GCOVTagAFDOFileNames))
    return EC;

  uint32_t Size;
  if (!GcovBuffer.readInt(Size))
    return sampleprof_error::truncated;

  for (uint32_t I = 0; I < Size; ++I) {
    StringRef Str;
    if (!GcovBuffer.readString(Str))
      return sampleprof_error::truncated;
    Names.push_back(std::string(Str));
  }

  return sampleprof_error::success;
}

std::error_code SampleProfileReaderGCC::readFunctionProfiles() {
  if (std::error_code EC = readSectionTag(GCOVTagAFDOFunction))
    return EC;

  uint32_t NumFunctions;
  if (!GcovBuffer.readInt(NumFunctions))
    return sampleprof_error::truncated;

  InlineCallStack Stack;
  for (uint32_t I = 0; I < NumFunctions; ++I)
    if (std::error_code EC = readOneFunctionProfile(Stack, true, 0))
      return EC;

  computeSummary();
  return sampleprof_error::success;
}

std::error_code SampleProfileReaderGCC::readOneFunctionProfile(
    const InlineCallStack &InlineStack, bool Update, uint32_t Offset) {
  uint64_t HeadCount = 0;
  if (InlineStack.size() == 0)
    if (!GcovBuffer.readInt64(HeadCount))
      return sampleprof_error::truncated;

  uint32_t NameIdx;
  if (!GcovBuffer.readInt(NameIdx))
    return sampleprof_error::truncated;

  StringRef Name(Names[NameIdx]);

  uint32_t NumPosCounts;
  if (!GcovBuffer.readInt(NumPosCounts))
    return sampleprof_error::truncated;

  uint32_t NumCallsites;
  if (!GcovBuffer.readInt(NumCallsites))
    return sampleprof_error::truncated;

  FunctionSamples *FProfile = nullptr;
  if (InlineStack.size() == 0) {
    // If this is a top function that we have already processed, do not
    // update its profile again.  This happens in the presence of
    // function aliases.  Since these aliases share the same function
    // body, there will be identical replicated profiles for the
    // original function.  In this case, we simply not bother updating
    // the profile of the original function.
    FProfile = &Profiles[Name];
    FProfile->addHeadSamples(HeadCount);
    if (FProfile->getTotalSamples() > 0)
      Update = false;
  } else {
    // Otherwise, we are reading an inlined instance. The top of the
    // inline stack contains the profile of the caller. Insert this
    // callee in the caller's CallsiteMap.
    FunctionSamples *CallerProfile = InlineStack.front();
    uint32_t LineOffset = Offset >> 16;
    uint32_t Discriminator = Offset & 0xffff;
    FProfile = &CallerProfile->functionSamplesAt(
        LineLocation(LineOffset, Discriminator))[std::string(Name)];
  }
  FProfile->setName(Name);

  for (uint32_t I = 0; I < NumPosCounts; ++I) {
    uint32_t Offset;
    if (!GcovBuffer.readInt(Offset))
      return sampleprof_error::truncated;

    uint32_t NumTargets;
    if (!GcovBuffer.readInt(NumTargets))
      return sampleprof_error::truncated;

    uint64_t Count;
    if (!GcovBuffer.readInt64(Count))
      return sampleprof_error::truncated;

    // The line location is encoded in the offset as:
    //   high 16 bits: line offset to the start of the function.
    //   low 16 bits: discriminator.
    uint32_t LineOffset = Offset >> 16;
    uint32_t Discriminator = Offset & 0xffff;

    InlineCallStack NewStack;
    NewStack.push_back(FProfile);
    llvm::append_range(NewStack, InlineStack);
    if (Update) {
      // Walk up the inline stack, adding the samples on this line to
      // the total sample count of the callers in the chain.
      for (auto CallerProfile : NewStack)
        CallerProfile->addTotalSamples(Count);

      // Update the body samples for the current profile.
      FProfile->addBodySamples(LineOffset, Discriminator, Count);
    }

    // Process the list of functions called at an indirect call site.
    // These are all the targets that a function pointer (or virtual
    // function) resolved at runtime.
    for (uint32_t J = 0; J < NumTargets; J++) {
      uint32_t HistVal;
      if (!GcovBuffer.readInt(HistVal))
        return sampleprof_error::truncated;

      if (HistVal != HIST_TYPE_INDIR_CALL_TOPN)
        return sampleprof_error::malformed;

      uint64_t TargetIdx;
      if (!GcovBuffer.readInt64(TargetIdx))
        return sampleprof_error::truncated;
      StringRef TargetName(Names[TargetIdx]);

      uint64_t TargetCount;
      if (!GcovBuffer.readInt64(TargetCount))
        return sampleprof_error::truncated;

      if (Update)
        FProfile->addCalledTargetSamples(LineOffset, Discriminator,
                                         TargetName, TargetCount);
    }
  }

  // Process all the inlined callers into the current function. These
  // are all the callsites that were inlined into this function.
  for (uint32_t I = 0; I < NumCallsites; I++) {
    // The offset is encoded as:
    //   high 16 bits: line offset to the start of the function.
    //   low 16 bits: discriminator.
    uint32_t Offset;
    if (!GcovBuffer.readInt(Offset))
      return sampleprof_error::truncated;
    InlineCallStack NewStack;
    NewStack.push_back(FProfile);
    llvm::append_range(NewStack, InlineStack);
    if (std::error_code EC = readOneFunctionProfile(NewStack, Update, Offset))
      return EC;
  }

  return sampleprof_error::success;
}

/// Read a GCC AutoFDO profile.
///
/// This format is generated by the Linux Perf conversion tool at
/// https://github.com/google/autofdo.
std::error_code SampleProfileReaderGCC::readImpl() {
  // Read the string table.
  if (std::error_code EC = readNameTable())
    return EC;

  // Read the source profile.
  if (std::error_code EC = readFunctionProfiles())
    return EC;

  return sampleprof_error::success;
}

bool SampleProfileReaderGCC::hasFormat(const MemoryBuffer &Buffer) {
  StringRef Magic(reinterpret_cast<const char *>(Buffer.getBufferStart()));
  return Magic == "adcg*704";
}

void SampleProfileReaderItaniumRemapper::applyRemapping(LLVMContext &Ctx) {
  // If the reader uses MD5 to represent string, we can't remap it because
  // we don't know what the original function names were.
  if (Reader.useMD5()) {
    Ctx.diagnose(DiagnosticInfoSampleProfile(
        Reader.getBuffer()->getBufferIdentifier(),
        "Profile data remapping cannot be applied to profile data "
        "in compact format (original mangled names are not available).",
        DS_Warning));
    return;
  }

  // CSSPGO-TODO: Remapper is not yet supported.
  // We will need to remap the entire context string.
  assert(Remappings && "should be initialized while creating remapper");
  for (auto &Sample : Reader.getProfiles()) {
    DenseSet<StringRef> NamesInSample;
    Sample.second.findAllNames(NamesInSample);
    for (auto &Name : NamesInSample)
      if (auto Key = Remappings->insert(Name))
        NameMap.insert({Key, Name});
  }

  RemappingApplied = true;
}

Optional<StringRef>
SampleProfileReaderItaniumRemapper::lookUpNameInProfile(StringRef Fname) {
  if (auto Key = Remappings->lookup(Fname))
    return NameMap.lookup(Key);
  return None;
}

/// Prepare a memory buffer for the contents of \p Filename.
///
/// \returns an error code indicating the status of the buffer.
static ErrorOr<std::unique_ptr<MemoryBuffer>>
setupMemoryBuffer(const Twine &Filename) {
  auto BufferOrErr = MemoryBuffer::getFileOrSTDIN(Filename);
  if (std::error_code EC = BufferOrErr.getError())
    return EC;
  auto Buffer = std::move(BufferOrErr.get());

  // Sanity check the file.
  if (uint64_t(Buffer->getBufferSize()) > std::numeric_limits<uint32_t>::max())
    return sampleprof_error::too_large;

  return std::move(Buffer);
}

/// Create a sample profile reader based on the format of the input file.
///
/// \param Filename The file to open.
///
/// \param C The LLVM context to use to emit diagnostics.
///
/// \param RemapFilename The file used for profile remapping.
///
/// \returns an error code indicating the status of the created reader.
ErrorOr<std::unique_ptr<SampleProfileReader>>
SampleProfileReader::create(const std::string Filename, LLVMContext &C,
                            const std::string RemapFilename) {
  auto BufferOrError = setupMemoryBuffer(Filename);
  if (std::error_code EC = BufferOrError.getError())
    return EC;
  return create(BufferOrError.get(), C, RemapFilename);
}

/// Create a sample profile remapper from the given input, to remap the
/// function names in the given profile data.
///
/// \param Filename The file to open.
///
/// \param Reader The profile reader the remapper is going to be applied to.
///
/// \param C The LLVM context to use to emit diagnostics.
///
/// \returns an error code indicating the status of the created reader.
ErrorOr<std::unique_ptr<SampleProfileReaderItaniumRemapper>>
SampleProfileReaderItaniumRemapper::create(const std::string Filename,
                                           SampleProfileReader &Reader,
                                           LLVMContext &C) {
  auto BufferOrError = setupMemoryBuffer(Filename);
  if (std::error_code EC = BufferOrError.getError())
    return EC;
  return create(BufferOrError.get(), Reader, C);
}

/// Create a sample profile remapper from the given input, to remap the
/// function names in the given profile data.
///
/// \param B The memory buffer to create the reader from (assumes ownership).
///
/// \param C The LLVM context to use to emit diagnostics.
///
/// \param Reader The profile reader the remapper is going to be applied to.
///
/// \returns an error code indicating the status of the created reader.
ErrorOr<std::unique_ptr<SampleProfileReaderItaniumRemapper>>
SampleProfileReaderItaniumRemapper::create(std::unique_ptr<MemoryBuffer> &B,
                                           SampleProfileReader &Reader,
                                           LLVMContext &C) {
  auto Remappings = std::make_unique<SymbolRemappingReader>();
  if (Error E = Remappings->read(*B.get())) {
    handleAllErrors(
        std::move(E), [&](const SymbolRemappingParseError &ParseError) {
          C.diagnose(DiagnosticInfoSampleProfile(B->getBufferIdentifier(),
                                                 ParseError.getLineNum(),
                                                 ParseError.getMessage()));
        });
    return sampleprof_error::malformed;
  }

  return std::make_unique<SampleProfileReaderItaniumRemapper>(
      std::move(B), std::move(Remappings), Reader);
}

/// Create a sample profile reader based on the format of the input data.
///
/// \param B The memory buffer to create the reader from (assumes ownership).
///
/// \param C The LLVM context to use to emit diagnostics.
///
/// \param RemapFilename The file used for profile remapping.
///
/// \returns an error code indicating the status of the created reader.
ErrorOr<std::unique_ptr<SampleProfileReader>>
SampleProfileReader::create(std::unique_ptr<MemoryBuffer> &B, LLVMContext &C,
                            const std::string RemapFilename) {
  std::unique_ptr<SampleProfileReader> Reader;
  if (SampleProfileReaderRawBinary::hasFormat(*B))
    Reader.reset(new SampleProfileReaderRawBinary(std::move(B), C));
  else if (SampleProfileReaderExtBinary::hasFormat(*B))
    Reader.reset(new SampleProfileReaderExtBinary(std::move(B), C));
  else if (SampleProfileReaderCompactBinary::hasFormat(*B))
    Reader.reset(new SampleProfileReaderCompactBinary(std::move(B), C));
  else if (SampleProfileReaderGCC::hasFormat(*B))
    Reader.reset(new SampleProfileReaderGCC(std::move(B), C));
  else if (SampleProfileReaderText::hasFormat(*B))
    Reader.reset(new SampleProfileReaderText(std::move(B), C));
  else
    return sampleprof_error::unrecognized_format;

  if (!RemapFilename.empty()) {
    auto ReaderOrErr =
        SampleProfileReaderItaniumRemapper::create(RemapFilename, *Reader, C);
    if (std::error_code EC = ReaderOrErr.getError()) {
      std::string Msg = "Could not create remapper: " + EC.message();
      C.diagnose(DiagnosticInfoSampleProfile(RemapFilename, Msg));
      return EC;
    }
    Reader->Remapper = std::move(ReaderOrErr.get());
  }

  FunctionSamples::Format = Reader->getFormat();
  if (std::error_code EC = Reader->readHeader()) {
    return EC;
  }

  return std::move(Reader);
}

// For text and GCC file formats, we compute the summary after reading the
// profile. Binary format has the profile summary in its header.
void SampleProfileReader::computeSummary() {
  SampleProfileSummaryBuilder Builder(ProfileSummaryBuilder::DefaultCutoffs);
  Summary = Builder.computeSummaryForProfiles(Profiles);
}