llvm/bolt/DataReader.cpp

//===-- DataReader.cpp - Perf data reader -----------------------*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This family of functions reads profile data written by the perf2bolt
// utility and stores it in memory for llvm-bolt consumption.
//
//===----------------------------------------------------------------------===//


#include "DataReader.h"

namespace llvm {
namespace bolt {

ErrorOr<const BranchInfo &> FuncBranchData::getBranch(uint64_t From,
                                                      uint64_t To) const {
  for (const auto &I : Data) {
    if (I.From.Offset == From && I.To.Offset == To)
      return I;
  }
  return make_error_code(llvm::errc::invalid_argument);
}

ErrorOr<std::unique_ptr<DataReader>>
DataReader::readPerfData(StringRef Path, raw_ostream &Diag) {
  ErrorOr<std::unique_ptr<MemoryBuffer>> MB =
      MemoryBuffer::getFileOrSTDIN(Path);
  if (std::error_code EC = MB.getError()) {
    Diag << "Cannot open " << Path << ": " << EC.message() << "\n";
  }
  auto DR = make_unique<DataReader>(std::move(MB.get()), Diag);
  DR->parse();
  return std::move(DR);
}

void DataReader::reportError(StringRef ErrorMsg) {
  Diag << "Error reading bolt data input file: line " << Line << ", column "
       << Col << ": " << ErrorMsg << '\n';
}

bool DataReader::expectAndConsumeFS() {
  if (ParsingBuf[0] != FieldSeparator) {
    reportError("expected field separator");
    return false;
  }
  ParsingBuf = ParsingBuf.drop_front(1);
  Col += 1;
  return true;
}

ErrorOr<StringRef> DataReader::parseString(char EndChar) {
  auto StringEnd = ParsingBuf.find(EndChar);
  if (StringEnd == StringRef::npos || StringEnd == 0) {
    reportError("malformed field");
    return make_error_code(llvm::errc::io_error);
  }
  StringRef Str = ParsingBuf.substr(0, StringEnd);
  ParsingBuf = ParsingBuf.drop_front(StringEnd + 1);
  Col += StringEnd + 1;
  return Str;
}

ErrorOr<int64_t> DataReader::parseNumberField(char EndChar) {
  auto NumStrRes = parseString(EndChar);
  if (std::error_code EC = NumStrRes.getError())
    return EC;
  StringRef NumStr = NumStrRes.get();
  int64_t Num;
  if (NumStr.getAsInteger(10, Num)) {
    reportError("expected decimal number");
    Diag << "Found: " << NumStr << "\n";
    return make_error_code(llvm::errc::io_error);
  }
  return Num;
}

ErrorOr<Location> DataReader::parseLocation() {
  // Read whether the location of the branch should be DSO or a symbol
  // 0 means it is a DSO. 1 means it is a global symbol. 2 means it is a local
  // symbol.
  if (ParsingBuf[0] != '0' && ParsingBuf[0] != '1' && ParsingBuf[0] != '2') {
    reportError("expected 0, 1 or 2");
    return make_error_code(llvm::errc::io_error);
  }

  bool IsSymbol = ParsingBuf[0] == '1' || ParsingBuf[0] == '2';
  ParsingBuf = ParsingBuf.drop_front(1);
  Col += 1;

  if (!expectAndConsumeFS())
    return make_error_code(llvm::errc::io_error);

  // Read the string containing the symbol or the DSO name
  auto NameRes = parseString(FieldSeparator);
  if (std::error_code EC = NameRes.getError())
    return EC;
  StringRef Name = NameRes.get();

  // Read the offset
  auto OffsetStrRes = parseString(FieldSeparator);
  if (std::error_code EC = OffsetStrRes.getError())
    return EC;
  StringRef OffsetStr = OffsetStrRes.get();
  uint64_t Offset;
  if (OffsetStr.getAsInteger(16, Offset)) {
    reportError("expected hexadecimal number");
    Diag << "Found: " << OffsetStr << "\n";
    return make_error_code(llvm::errc::io_error);
  }

  return Location(IsSymbol, Name, Offset);
}

ErrorOr<BranchInfo> DataReader::parseBranchInfo() {
  auto Res = parseLocation();
  if (std::error_code EC = Res.getError())
    return EC;
  Location From = Res.get();

  Res = parseLocation();
  if (std::error_code EC = Res.getError())
    return EC;
  Location To = Res.get();

  auto MRes = parseNumberField(FieldSeparator);
  if (std::error_code EC = MRes.getError())
    return EC;
  int64_t NumMispreds = MRes.get();

  auto BRes = parseNumberField('\n');
  if (std::error_code EC = BRes.getError())
    return EC;
  int64_t NumBranches = BRes.get();

  return BranchInfo(std::move(From), std::move(To), NumMispreds, NumBranches);
}

bool DataReader::hasData() {
  if (ParsingBuf.size() == 0)
    return false;

  if (ParsingBuf[0] == '0' || ParsingBuf[0] == '1' || ParsingBuf[0] == '2')
    return true;
  return false;
}

std::error_code DataReader::parse() {
  auto GetOrCreateFuncEntry = [&](StringRef Name) {
    auto I = FuncsMap.find(Name);
    if (I == FuncsMap.end()) {
      bool success;
      std::tie(I, success) = FuncsMap.insert(
          std::make_pair(Name, FuncBranchData(Name,
                                              FuncBranchData::ContainerTy())));
      assert(success && "unexpected result of insert");
    }
    return I;
  };

  Col = 0;
  Line = 1;
  while (hasData()) {
    auto Res = parseBranchInfo();
    if (std::error_code EC = Res.getError())
      return EC;
    Col = 0;
    Line += 1;

    BranchInfo BI = Res.get();

    // Ignore branches not involving known location.
    if (!BI.From.IsSymbol && !BI.To.IsSymbol)
      continue;

    auto I = GetOrCreateFuncEntry(BI.From.Name);
    I->getValue().Data.emplace_back(std::move(BI));

    // If destination is the function start - update execution count.
    // NB: the data is skewed since we cannot tell tail recursion from
    //     branches to the function start.
    if (BI.To.IsSymbol && BI.To.Offset == 0) {
      I = GetOrCreateFuncEntry(BI.To.Name);
      I->getValue().ExecutionCount += BI.Branches;
    }

  }
  return std::error_code();
}

ErrorOr<const FuncBranchData &>
DataReader::getFuncBranchData(StringRef FuncName) const {
  const auto I = FuncsMap.find(FuncName);
  if (I == FuncsMap.end()) {
    return make_error_code(llvm::errc::invalid_argument);
  }
  return I->getValue();
}

void DataReader::dump() const {
  for (const auto &Func : FuncsMap) {
    for (const auto &BI : Func.getValue().Data) {
      Diag << BI.From.Name << " " << BI.From.Offset << " " << BI.To.Name << " "
           << BI.To.Offset << " " << BI.Mispreds << " " << BI.Branches << "\n";
    }
  }
}
}
}