text: //=-- InstrProfWriter.cpp - Instrumented profiling writer -------------------=//
  //
  //                     The LLVM Compiler Infrastructure
  //
  // This file is distributed under the University of Illinois Open Source
  // License. See LICENSE.TXT for details.
  //
  //===----------------------------------------------------------------------===//
  //
  // This file contains support for writing profiling data for clang's
  // instrumentation based PGO and coverage.
  //
  //===----------------------------------------------------------------------===//
  
  #include "llvm/ProfileData/InstrProfWriter.h"
  #include "InstrProfIndexed.h"
  #include "llvm/ADT/StringExtras.h"
  #include "llvm/Support/EndianStream.h"
  #include "llvm/Support/OnDiskHashTable.h"
  
  using namespace llvm;
  
  namespace {
  class InstrProfRecordTrait {
  public:
    typedef StringRef key_type;
    typedef StringRef key_type_ref;
  
    typedef const InstrProfWriter::CounterData *const data_type;
    typedef const InstrProfWriter::CounterData *const data_type_ref;
  
    typedef uint64_t hash_value_type;
    typedef uint64_t offset_type;
  
    static hash_value_type ComputeHash(key_type_ref K) {
      return IndexedInstrProf::ComputeHash(IndexedInstrProf::HashType, K);
    }
  
    static std::pair<offset_type, offset_type>
    EmitKeyDataLength(raw_ostream &Out, key_type_ref K, data_type_ref V) {
      using namespace llvm::support;
      endian::Writer<little> LE(Out);
  
      offset_type N = K.size();
      LE.write<offset_type>(N);
  
      offset_type M = 0;
      for (const auto &Counts : *V)
        M += (2 + Counts.second.size()) * sizeof(uint64_t);
      LE.write<offset_type>(M);
  
      return std::make_pair(N, M);
    }
  
    static void EmitKey(raw_ostream &Out, key_type_ref K, offset_type N){
      Out.write(K.data(), N);
    }
  
    static void EmitData(raw_ostream &Out, key_type_ref, data_type_ref V,
                         offset_type) {
      using namespace llvm::support;
      endian::Writer<little> LE(Out);
  
      for (const auto &Counts : *V) {
        LE.write<uint64_t>(Counts.first);
        LE.write<uint64_t>(Counts.second.size());
        for (uint64_t I : Counts.second)
          LE.write<uint64_t>(I);
      }
    }
  };
  }
  
  std::error_code
  InstrProfWriter::addFunctionCounts(StringRef FunctionName,
                                     uint64_t FunctionHash,
                                     ArrayRef<uint64_t> Counters) {
    auto &CounterData = FunctionData[FunctionName];
  
    auto Where = CounterData.find(FunctionHash);
    if (Where == CounterData.end()) {
      // We've never seen a function with this name and hash, add it.
      CounterData[FunctionHash] = Counters;
      // We keep track of the max function count as we go for simplicity.
      if (Counters[0] > MaxFunctionCount)
        MaxFunctionCount = Counters[0];
      return instrprof_error::success;
    }
  
    // We're updating a function we've seen before.
    auto &FoundCounters = Where->second;
    // If the number of counters doesn't match we either have bad data or a hash
    // collision.
    if (FoundCounters.size() != Counters.size())
      return instrprof_error::count_mismatch;
  
    for (size_t I = 0, E = Counters.size(); I < E; ++I) {
      if (FoundCounters[I] + Counters[I] < FoundCounters[I])
        return instrprof_error::counter_overflow;
      FoundCounters[I] += Counters[I];
    }
    // We keep track of the max function count as we go for simplicity.
    if (FoundCounters[0] > MaxFunctionCount)
      MaxFunctionCount = FoundCounters[0];
  
    return instrprof_error::success;
  }
  
  void InstrProfWriter::write(raw_fd_ostream &OS) {
    OnDiskChainedHashTableGenerator<InstrProfRecordTrait> Generator;
  
    // Populate the hash table generator.
    for (const auto &I : FunctionData)
      Generator.insert(I.getKey(), &I.getValue());
  
    using namespace llvm::support;
    endian::Writer<little> LE(OS);
  
    // Write the header.
    LE.write<uint64_t>(IndexedInstrProf::Magic);
    LE.write<uint64_t>(IndexedInstrProf::Version);
    LE.write<uint64_t>(MaxFunctionCount);
    LE.write<uint64_t>(static_cast<uint64_t>(IndexedInstrProf::HashType));
  
    // Save a space to write the hash table start location.
    uint64_t HashTableStartLoc = OS.tell();
    LE.write<uint64_t>(0);
    // Write the hash table.
    uint64_t HashTableStart = Generator.Emit(OS);
  
    // Go back and fill in the hash table start.
    OS.seek(HashTableStartLoc);
    LE.write<uint64_t>(HashTableStart);
  }
  