xref: /llvm-project-15.0.7/bolt/lib/Passes/BinaryPasses.cpp (revision aaa50e54)

//===- bolt/Passes/BinaryPasses.cpp - Binary-level passes -----------------===//
//
// 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 multiple passes for binary optimization and analysis.
//
//===----------------------------------------------------------------------===//

#include "bolt/Passes/BinaryPasses.h"
#include "bolt/Core/ParallelUtilities.h"
#include "bolt/Passes/ReorderAlgorithm.h"
#include "bolt/Passes/ReorderFunctions.h"
#include "llvm/Support/CommandLine.h"

#include <numeric>
#include <vector>

#define DEBUG_TYPE "bolt-opts"

using namespace llvm;
using namespace bolt;

namespace {

const char *dynoStatsOptName(const bolt::DynoStats::Category C) {
  if (C == bolt::DynoStats::FIRST_DYNO_STAT)
    return "none";
  else if (C == bolt::DynoStats::LAST_DYNO_STAT)
    return "all";

  static std::string OptNames[bolt::DynoStats::LAST_DYNO_STAT + 1];

  OptNames[C] = bolt::DynoStats::Description(C);

  std::replace(OptNames[C].begin(), OptNames[C].end(), ' ', '-');

  return OptNames[C].c_str();
}

const char *dynoStatsOptDesc(const bolt::DynoStats::Category C) {
  if (C == bolt::DynoStats::FIRST_DYNO_STAT)
    return "unsorted";
  else if (C == bolt::DynoStats::LAST_DYNO_STAT)
    return "sorted by all stats";

  return bolt::DynoStats::Description(C);
}

}

namespace opts {

extern cl::OptionCategory BoltCategory;
extern cl::OptionCategory BoltOptCategory;

extern cl::opt<bolt::MacroFusionType> AlignMacroOpFusion;
extern cl::opt<unsigned> Verbosity;
extern cl::opt<bool> EnableBAT;
extern cl::opt<unsigned> ExecutionCountThreshold;
extern cl::opt<bool> UpdateDebugSections;
extern cl::opt<bolt::ReorderFunctions::ReorderType> ReorderFunctions;

enum DynoStatsSortOrder : char {
  Ascending,
  Descending
};

static cl::opt<DynoStatsSortOrder>
DynoStatsSortOrderOpt("print-sorted-by-order",
  cl::desc("use ascending or descending order when printing functions "
           "ordered by dyno stats"),
  cl::ZeroOrMore,
  cl::init(DynoStatsSortOrder::Descending),
  cl::cat(BoltOptCategory));

cl::list<std::string>
HotTextMoveSections("hot-text-move-sections",
  cl::desc("list of sections containing functions used for hugifying hot text. "
           "BOLT makes sure these functions are not placed on the same page as "
           "the hot text. (default=\'.stub,.mover\')."),
  cl::value_desc("sec1,sec2,sec3,..."),
  cl::CommaSeparated,
  cl::ZeroOrMore,
  cl::cat(BoltCategory));

bool isHotTextMover(const BinaryFunction &Function) {
  for (std::string &SectionName : opts::HotTextMoveSections) {
    if (Function.getOriginSectionName() &&
        *Function.getOriginSectionName() == SectionName)
      return true;
  }

  return false;
}

static cl::opt<bool>
MinBranchClusters("min-branch-clusters",
  cl::desc("use a modified clustering algorithm geared towards minimizing "
           "branches"),
  cl::ZeroOrMore,
  cl::Hidden,
  cl::cat(BoltOptCategory));

enum PeepholeOpts : char {
  PEEP_NONE             = 0x0,
  PEEP_DOUBLE_JUMPS     = 0x2,
  PEEP_TAILCALL_TRAPS   = 0x4,
  PEEP_USELESS_BRANCHES = 0x8,
  PEEP_ALL              = 0xf
};

static cl::list<PeepholeOpts>
Peepholes("peepholes",
  cl::CommaSeparated,
  cl::desc("enable peephole optimizations"),
  cl::value_desc("opt1,opt2,opt3,..."),
  cl::values(
    clEnumValN(PEEP_NONE, "none", "disable peepholes"),
    clEnumValN(PEEP_DOUBLE_JUMPS, "double-jumps",
               "remove double jumps when able"),
    clEnumValN(PEEP_TAILCALL_TRAPS, "tailcall-traps", "insert tail call traps"),
    clEnumValN(PEEP_USELESS_BRANCHES, "useless-branches",
               "remove useless conditional branches"),
    clEnumValN(PEEP_ALL, "all", "enable all peephole optimizations")),
  cl::ZeroOrMore,
  cl::cat(BoltOptCategory));

static cl::opt<unsigned>
PrintFuncStat("print-function-statistics",
  cl::desc("print statistics about basic block ordering"),
  cl::init(0),
  cl::ZeroOrMore,
  cl::cat(BoltOptCategory));

static cl::list<bolt::DynoStats::Category>
PrintSortedBy("print-sorted-by",
  cl::CommaSeparated,
  cl::desc("print functions sorted by order of dyno stats"),
  cl::value_desc("key1,key2,key3,..."),
  cl::values(
#define D(name, ...)                                        \
    clEnumValN(bolt::DynoStats::name,                     \
               dynoStatsOptName(bolt::DynoStats::name),   \
               dynoStatsOptDesc(bolt::DynoStats::name)),
    DYNO_STATS
#undef D
    clEnumValN(0xffff, ".", ".")
    ),
  cl::ZeroOrMore,
  cl::cat(BoltOptCategory));

static cl::opt<bool>
PrintUnknown("print-unknown",
  cl::desc("print names of functions with unknown control flow"),
  cl::init(false),
  cl::ZeroOrMore,
  cl::cat(BoltCategory),
  cl::Hidden);

static cl::opt<bool>
PrintUnknownCFG("print-unknown-cfg",
  cl::desc("dump CFG of functions with unknown control flow"),
  cl::init(false),
  cl::ZeroOrMore,
  cl::cat(BoltCategory),
  cl::ReallyHidden);

cl::opt<bolt::ReorderBasicBlocks::LayoutType> ReorderBlocks(
    "reorder-blocks", cl::desc("change layout of basic blocks in a function"),
    cl::init(bolt::ReorderBasicBlocks::LT_NONE),
    cl::values(
        clEnumValN(bolt::ReorderBasicBlocks::LT_NONE, "none",
                   "do not reorder basic blocks"),
        clEnumValN(bolt::ReorderBasicBlocks::LT_REVERSE, "reverse",
                   "layout blocks in reverse order"),
        clEnumValN(bolt::ReorderBasicBlocks::LT_OPTIMIZE, "normal",
                   "perform optimal layout based on profile"),
        clEnumValN(bolt::ReorderBasicBlocks::LT_OPTIMIZE_BRANCH,
                   "branch-predictor",
                   "perform optimal layout prioritizing branch "
                   "predictions"),
        clEnumValN(bolt::ReorderBasicBlocks::LT_OPTIMIZE_CACHE, "cache",
                   "perform optimal layout prioritizing I-cache "
                   "behavior"),
        clEnumValN(bolt::ReorderBasicBlocks::LT_OPTIMIZE_EXT_TSP, "cache+",
                   "perform layout optimizing I-cache behavior"),
        clEnumValN(bolt::ReorderBasicBlocks::LT_OPTIMIZE_EXT_TSP, "ext-tsp",
                   "perform layout optimizing I-cache behavior"),
        clEnumValN(bolt::ReorderBasicBlocks::LT_OPTIMIZE_SHUFFLE,
                   "cluster-shuffle", "perform random layout of clusters")),
    cl::ZeroOrMore, cl::cat(BoltOptCategory));

static cl::opt<unsigned>
ReportBadLayout("report-bad-layout",
  cl::desc("print top <uint> functions with suboptimal code layout on input"),
  cl::init(0),
  cl::ZeroOrMore,
  cl::Hidden,
  cl::cat(BoltOptCategory));

static cl::opt<bool>
ReportStaleFuncs("report-stale",
  cl::desc("print the list of functions with stale profile"),
  cl::init(false),
  cl::ZeroOrMore,
  cl::Hidden,
  cl::cat(BoltOptCategory));

enum SctcModes : char {
  SctcAlways,
  SctcPreserveDirection,
  SctcHeuristic
};

static cl::opt<SctcModes>
SctcMode("sctc-mode",
  cl::desc("mode for simplify conditional tail calls"),
  cl::init(SctcAlways),
  cl::values(clEnumValN(SctcAlways, "always", "always perform sctc"),
    clEnumValN(SctcPreserveDirection,
      "preserve",
      "only perform sctc when branch direction is "
      "preserved"),
    clEnumValN(SctcHeuristic,
      "heuristic",
      "use branch prediction data to control sctc")),
  cl::ZeroOrMore,
  cl::cat(BoltOptCategory));

static cl::opt<unsigned>
StaleThreshold("stale-threshold",
    cl::desc(
      "maximum percentage of stale functions to tolerate (default: 100)"),
    cl::init(100),
    cl::Hidden,
    cl::cat(BoltOptCategory));

static cl::opt<unsigned>
TSPThreshold("tsp-threshold",
  cl::desc("maximum number of hot basic blocks in a function for which to use "
           "a precise TSP solution while re-ordering basic blocks"),
  cl::init(10),
  cl::ZeroOrMore,
  cl::Hidden,
  cl::cat(BoltOptCategory));

static cl::opt<unsigned>
TopCalledLimit("top-called-limit",
  cl::desc("maximum number of functions to print in top called "
           "functions section"),
  cl::init(100),
  cl::ZeroOrMore,
  cl::Hidden,
  cl::cat(BoltCategory));

} // namespace opts

namespace llvm {
namespace bolt {

bool BinaryFunctionPass::shouldOptimize(const BinaryFunction &BF) const {
  return BF.isSimple() && BF.getState() == BinaryFunction::State::CFG &&
         !BF.isIgnored();
}

bool BinaryFunctionPass::shouldPrint(const BinaryFunction &BF) const {
  return BF.isSimple() && !BF.isIgnored();
}

void NormalizeCFG::runOnFunction(BinaryFunction &BF) {
  uint64_t NumRemoved = 0;
  uint64_t NumDuplicateEdges = 0;
  uint64_t NeedsFixBranches = 0;
  for (BinaryBasicBlock &BB : BF) {
    if (!BB.empty())
      continue;

    if (BB.isEntryPoint() || BB.isLandingPad())
      continue;

    // Handle a dangling empty block.
    if (BB.succ_size() == 0) {
      // If an empty dangling basic block has a predecessor, it could be a
      // result of codegen for __builtin_unreachable. In such case, do not
      // remove the block.
      if (BB.pred_size() == 0) {
        BB.markValid(false);
        ++NumRemoved;
      }
      continue;
    }

    // The block should have just one successor.
    BinaryBasicBlock *Successor = BB.getSuccessor();
    assert(Successor && "invalid CFG encountered");

    // Redirect all predecessors to the successor block.
    while (!BB.pred_empty()) {
      BinaryBasicBlock *Predecessor = *BB.pred_begin();
      if (Predecessor->hasJumpTable())
        break;

      if (Predecessor == Successor)
        break;

      BinaryBasicBlock::BinaryBranchInfo &BI = Predecessor->getBranchInfo(BB);
      Predecessor->replaceSuccessor(&BB, Successor, BI.Count,
                                    BI.MispredictedCount);
      // We need to fix branches even if we failed to replace all successors
      // and remove the block.
      NeedsFixBranches = true;
    }

    if (BB.pred_empty()) {
      BB.removeAllSuccessors();
      BB.markValid(false);
      ++NumRemoved;
    }
  }

  if (NumRemoved)
    BF.eraseInvalidBBs();

  // Check for duplicate successors. Do it after the empty block elimination as
  // we can get more duplicate successors.
  for (BinaryBasicBlock &BB : BF)
    if (!BB.hasJumpTable() && BB.succ_size() == 2 &&
        BB.getConditionalSuccessor(false) == BB.getConditionalSuccessor(true))
      ++NumDuplicateEdges;

  // fixBranches() will get rid of duplicate edges and update jump instructions.
  if (NumDuplicateEdges || NeedsFixBranches)
    BF.fixBranches();

  NumDuplicateEdgesMerged += NumDuplicateEdges;
  NumBlocksRemoved += NumRemoved;
}

void NormalizeCFG::runOnFunctions(BinaryContext &BC) {
  ParallelUtilities::runOnEachFunction(
      BC, ParallelUtilities::SchedulingPolicy::SP_BB_LINEAR,
      [&](BinaryFunction &BF) { runOnFunction(BF); },
      [&](const BinaryFunction &BF) { return !shouldOptimize(BF); },
      "NormalizeCFG");
  if (NumBlocksRemoved)
    outs() << "BOLT-INFO: removed " << NumBlocksRemoved << " empty block"
           << (NumBlocksRemoved == 1 ? "" : "s") << '\n';
  if (NumDuplicateEdgesMerged)
    outs() << "BOLT-INFO: merged " << NumDuplicateEdgesMerged
           << " duplicate CFG edge" << (NumDuplicateEdgesMerged == 1 ? "" : "s")
           << '\n';
}

void EliminateUnreachableBlocks::runOnFunction(BinaryFunction &Function) {
  if (Function.layout_size() > 0) {
    unsigned Count;
    uint64_t Bytes;
    Function.markUnreachableBlocks();
    LLVM_DEBUG({
      for (BinaryBasicBlock *BB : Function.layout()) {
        if (!BB->isValid()) {
          dbgs() << "BOLT-INFO: UCE found unreachable block " << BB->getName()
                 << " in function " << Function << "\n";
          Function.dump();
        }
      }
    });
    std::tie(Count, Bytes) = Function.eraseInvalidBBs();
    DeletedBlocks += Count;
    DeletedBytes += Bytes;
    if (Count) {
      Modified.insert(&Function);
      if (opts::Verbosity > 0)
        outs() << "BOLT-INFO: Removed " << Count
               << " dead basic block(s) accounting for " << Bytes
               << " bytes in function " << Function << '\n';
    }
  }
}

void EliminateUnreachableBlocks::runOnFunctions(BinaryContext &BC) {
  for (auto &It : BC.getBinaryFunctions()) {
    BinaryFunction &Function = It.second;
    if (shouldOptimize(Function))
      runOnFunction(Function);
  }

  outs() << "BOLT-INFO: UCE removed " << DeletedBlocks << " blocks and "
         << DeletedBytes << " bytes of code.\n";
}

bool ReorderBasicBlocks::shouldPrint(const BinaryFunction &BF) const {
  return (BinaryFunctionPass::shouldPrint(BF) &&
          opts::ReorderBlocks != ReorderBasicBlocks::LT_NONE);
}

bool ReorderBasicBlocks::shouldOptimize(const BinaryFunction &BF) const {
  // Apply execution count threshold
  if (BF.getKnownExecutionCount() < opts::ExecutionCountThreshold)
    return false;

  return BinaryFunctionPass::shouldOptimize(BF);
}

void ReorderBasicBlocks::runOnFunctions(BinaryContext &BC) {
  if (opts::ReorderBlocks == ReorderBasicBlocks::LT_NONE)
    return;

  std::atomic<uint64_t> ModifiedFuncCount{0};

  ParallelUtilities::WorkFuncTy WorkFun = [&](BinaryFunction &BF) {
    modifyFunctionLayout(BF, opts::ReorderBlocks, opts::MinBranchClusters);
    if (BF.hasLayoutChanged())
      ++ModifiedFuncCount;
  };

  ParallelUtilities::PredicateTy SkipFunc = [&](const BinaryFunction &BF) {
    return !shouldOptimize(BF);
  };

  ParallelUtilities::runOnEachFunction(
      BC, ParallelUtilities::SchedulingPolicy::SP_BB_LINEAR, WorkFun, SkipFunc,
      "ReorderBasicBlocks");

  outs() << "BOLT-INFO: basic block reordering modified layout of "
         << format("%zu (%.2lf%%) functions\n", ModifiedFuncCount.load(),
                   100.0 * ModifiedFuncCount.load() /
                       BC.getBinaryFunctions().size());

  if (opts::PrintFuncStat > 0) {
    raw_ostream &OS = outs();
    // Copy all the values into vector in order to sort them
    std::map<uint64_t, BinaryFunction &> ScoreMap;
    auto &BFs = BC.getBinaryFunctions();
    for (auto It = BFs.begin(); It != BFs.end(); ++It)
      ScoreMap.insert(std::pair<uint64_t, BinaryFunction &>(
          It->second.getFunctionScore(), It->second));

    OS << "\nBOLT-INFO: Printing Function Statistics:\n\n";
    OS << "           There are " << BFs.size() << " functions in total. \n";
    OS << "           Number of functions being modified: "
       << ModifiedFuncCount.load() << "\n";
    OS << "           User asks for detailed information on top "
       << opts::PrintFuncStat << " functions. (Ranked by function score)"
       << "\n\n";
    uint64_t I = 0;
    for (std::map<uint64_t, BinaryFunction &>::reverse_iterator Rit =
             ScoreMap.rbegin();
         Rit != ScoreMap.rend() && I < opts::PrintFuncStat; ++Rit, ++I) {
      BinaryFunction &Function = Rit->second;

      OS << "           Information for function of top: " << (I + 1) << ": \n";
      OS << "             Function Score is: " << Function.getFunctionScore()
         << "\n";
      OS << "             There are " << Function.size()
         << " number of blocks in this function.\n";
      OS << "             There are " << Function.getInstructionCount()
         << " number of instructions in this function.\n";
      OS << "             The edit distance for this function is: "
         << Function.getEditDistance() << "\n\n";
    }
  }
}

void ReorderBasicBlocks::modifyFunctionLayout(BinaryFunction &BF,
                                              LayoutType Type,
                                              bool MinBranchClusters) const {
  if (BF.size() == 0 || Type == LT_NONE)
    return;

  BinaryFunction::BasicBlockOrderType NewLayout;
  std::unique_ptr<ReorderAlgorithm> Algo;

  // Cannot do optimal layout without profile.
  if (Type != LT_REVERSE && !BF.hasValidProfile())
    return;

  if (Type == LT_REVERSE) {
    Algo.reset(new ReverseReorderAlgorithm());
  } else if (BF.size() <= opts::TSPThreshold && Type != LT_OPTIMIZE_SHUFFLE) {
    // Work on optimal solution if problem is small enough
    LLVM_DEBUG(dbgs() << "finding optimal block layout for " << BF << "\n");
    Algo.reset(new TSPReorderAlgorithm());
  } else {
    LLVM_DEBUG(dbgs() << "running block layout heuristics on " << BF << "\n");

    std::unique_ptr<ClusterAlgorithm> CAlgo;
    if (MinBranchClusters)
      CAlgo.reset(new MinBranchGreedyClusterAlgorithm());
    else
      CAlgo.reset(new PHGreedyClusterAlgorithm());

    switch (Type) {
    case LT_OPTIMIZE:
      Algo.reset(new OptimizeReorderAlgorithm(std::move(CAlgo)));
      break;

    case LT_OPTIMIZE_BRANCH:
      Algo.reset(new OptimizeBranchReorderAlgorithm(std::move(CAlgo)));
      break;

    case LT_OPTIMIZE_CACHE:
      Algo.reset(new OptimizeCacheReorderAlgorithm(std::move(CAlgo)));
      break;

    case LT_OPTIMIZE_EXT_TSP:
      Algo.reset(new ExtTSPReorderAlgorithm());
      break;

    case LT_OPTIMIZE_SHUFFLE:
      Algo.reset(new RandomClusterReorderAlgorithm(std::move(CAlgo)));
      break;

    default:
      llvm_unreachable("unexpected layout type");
    }
  }

  Algo->reorderBasicBlocks(BF, NewLayout);

  BF.updateBasicBlockLayout(NewLayout);
}

void FixupBranches::runOnFunctions(BinaryContext &BC) {
  for (auto &It : BC.getBinaryFunctions()) {
    BinaryFunction &Function = It.second;
    if (!BC.shouldEmit(Function) || !Function.isSimple())
      continue;

    Function.fixBranches();
  }
}

void FinalizeFunctions::runOnFunctions(BinaryContext &BC) {
  ParallelUtilities::WorkFuncTy WorkFun = [&](BinaryFunction &BF) {
    if (!BF.finalizeCFIState()) {
      if (BC.HasRelocations) {
        errs() << "BOLT-ERROR: unable to fix CFI state for function " << BF
               << ". Exiting.\n";
        exit(1);
      }
      BF.setSimple(false);
      return;
    }

    BF.setFinalized();

    // Update exception handling information.
    BF.updateEHRanges();
  };

  ParallelUtilities::PredicateTy SkipPredicate = [&](const BinaryFunction &BF) {
    return !BC.shouldEmit(BF);
  };

  ParallelUtilities::runOnEachFunction(
      BC, ParallelUtilities::SchedulingPolicy::SP_CONSTANT, WorkFun,
      SkipPredicate, "FinalizeFunctions");
}

void CheckLargeFunctions::runOnFunctions(BinaryContext &BC) {
  if (BC.HasRelocations)
    return;

  if (!opts::UpdateDebugSections)
    return;

  // If the function wouldn't fit, mark it as non-simple. Otherwise, we may emit
  // incorrect debug info.
  ParallelUtilities::WorkFuncTy WorkFun = [&](BinaryFunction &BF) {
    uint64_t HotSize, ColdSize;
    std::tie(HotSize, ColdSize) =
        BC.calculateEmittedSize(BF, /*FixBranches=*/false);
    if (HotSize > BF.getMaxSize())
      BF.setSimple(false);
  };

  ParallelUtilities::PredicateTy SkipFunc = [&](const BinaryFunction &BF) {
    return !shouldOptimize(BF);
  };

  ParallelUtilities::runOnEachFunction(
      BC, ParallelUtilities::SchedulingPolicy::SP_INST_LINEAR, WorkFun,
      SkipFunc, "CheckLargeFunctions");
}

bool CheckLargeFunctions::shouldOptimize(const BinaryFunction &BF) const {
  // Unlike other passes, allow functions in non-CFG state.
  return BF.isSimple() && !BF.isIgnored();
}

void LowerAnnotations::runOnFunctions(BinaryContext &BC) {
  std::vector<std::pair<MCInst *, uint32_t>> PreservedOffsetAnnotations;

  for (auto &It : BC.getBinaryFunctions()) {
    BinaryFunction &BF = It.second;
    int64_t CurrentGnuArgsSize = 0;

    // Have we crossed hot/cold border for split functions?
    bool SeenCold = false;

    for (BinaryBasicBlock *BB : BF.layout()) {
      if (BB->isCold() && !SeenCold) {
        SeenCold = true;
        CurrentGnuArgsSize = 0;
      }

      // First convert GnuArgsSize annotations into CFIs. This may change instr
      // pointers, so do it before recording ptrs for preserved annotations
      if (BF.usesGnuArgsSize()) {
        for (auto II = BB->begin(); II != BB->end(); ++II) {
          if (!BC.MIB->isInvoke(*II))
            continue;
          const int64_t NewGnuArgsSize = BC.MIB->getGnuArgsSize(*II);
          assert(NewGnuArgsSize >= 0 && "expected non-negative GNU_args_size");
          if (NewGnuArgsSize != CurrentGnuArgsSize) {
            auto InsertII = BF.addCFIInstruction(
                BB, II,
                MCCFIInstruction::createGnuArgsSize(nullptr, NewGnuArgsSize));
            CurrentGnuArgsSize = NewGnuArgsSize;
            II = std::next(InsertII);
          }
        }
      }

      // Now record preserved annotations separately and then strip annotations.
      for (auto II = BB->begin(); II != BB->end(); ++II) {
        if (BF.requiresAddressTranslation() && BC.MIB->getOffset(*II))
          PreservedOffsetAnnotations.emplace_back(&(*II),
                                                  *BC.MIB->getOffset(*II));
        BC.MIB->stripAnnotations(*II);
      }
    }
  }
  for (BinaryFunction *BF : BC.getInjectedBinaryFunctions())
    for (BinaryBasicBlock &BB : *BF)
      for (MCInst &Instruction : BB)
        BC.MIB->stripAnnotations(Instruction);

  // Release all memory taken by annotations
  BC.MIB->freeAnnotations();

  // Reinsert preserved annotations we need during code emission.
  for (const std::pair<MCInst *, uint32_t> &Item : PreservedOffsetAnnotations)
    BC.MIB->setOffset(*Item.first, Item.second);
}

namespace {

// This peephole fixes jump instructions that jump to another basic
// block with a single jump instruction, e.g.
//
// B0: ...
//     jmp  B1   (or jcc B1)
//
// B1: jmp  B2
//
// ->
//
// B0: ...
//     jmp  B2   (or jcc B2)
//
uint64_t fixDoubleJumps(BinaryFunction &Function, bool MarkInvalid) {
  uint64_t NumDoubleJumps = 0;

  MCContext *Ctx = Function.getBinaryContext().Ctx.get();
  MCPlusBuilder *MIB = Function.getBinaryContext().MIB.get();
  for (BinaryBasicBlock &BB : Function) {
    auto checkAndPatch = [&](BinaryBasicBlock *Pred, BinaryBasicBlock *Succ,
                             const MCSymbol *SuccSym) {
      // Ignore infinite loop jumps or fallthrough tail jumps.
      if (Pred == Succ || Succ == &BB)
        return false;

      if (Succ) {
        const MCSymbol *TBB = nullptr;
        const MCSymbol *FBB = nullptr;
        MCInst *CondBranch = nullptr;
        MCInst *UncondBranch = nullptr;
        bool Res = Pred->analyzeBranch(TBB, FBB, CondBranch, UncondBranch);
        if (!Res) {
          LLVM_DEBUG(dbgs() << "analyzeBranch failed in peepholes in block:\n";
                     Pred->dump());
          return false;
        }
        Pred->replaceSuccessor(&BB, Succ);

        // We must patch up any existing branch instructions to match up
        // with the new successor.
        assert((CondBranch || (!CondBranch && Pred->succ_size() == 1)) &&
               "Predecessor block has inconsistent number of successors");
        if (CondBranch && MIB->getTargetSymbol(*CondBranch) == BB.getLabel()) {
          MIB->replaceBranchTarget(*CondBranch, Succ->getLabel(), Ctx);
        } else if (UncondBranch &&
                   MIB->getTargetSymbol(*UncondBranch) == BB.getLabel()) {
          MIB->replaceBranchTarget(*UncondBranch, Succ->getLabel(), Ctx);
        } else if (!UncondBranch) {
          assert(Function.getBasicBlockAfter(Pred, false) != Succ &&
                 "Don't add an explicit jump to a fallthrough block.");
          Pred->addBranchInstruction(Succ);
        }
      } else {
        // Succ will be null in the tail call case.  In this case we
        // need to explicitly add a tail call instruction.
        MCInst *Branch = Pred->getLastNonPseudoInstr();
        if (Branch && MIB->isUnconditionalBranch(*Branch)) {
          assert(MIB->getTargetSymbol(*Branch) == BB.getLabel());
          Pred->removeSuccessor(&BB);
          Pred->eraseInstruction(Pred->findInstruction(Branch));
          Pred->addTailCallInstruction(SuccSym);
        } else {
          return false;
        }
      }

      ++NumDoubleJumps;
      LLVM_DEBUG(dbgs() << "Removed double jump in " << Function << " from "
                        << Pred->getName() << " -> " << BB.getName() << " to "
                        << Pred->getName() << " -> " << SuccSym->getName()
                        << (!Succ ? " (tail)\n" : "\n"));

      return true;
    };

    if (BB.getNumNonPseudos() != 1 || BB.isLandingPad())
      continue;

    MCInst *Inst = BB.getFirstNonPseudoInstr();
    const bool IsTailCall = MIB->isTailCall(*Inst);

    if (!MIB->isUnconditionalBranch(*Inst) && !IsTailCall)
      continue;

    // If we operate after SCTC make sure it's not a conditional tail call.
    if (IsTailCall && MIB->isConditionalBranch(*Inst))
      continue;

    const MCSymbol *SuccSym = MIB->getTargetSymbol(*Inst);
    BinaryBasicBlock *Succ = BB.getSuccessor();

    if (((!Succ || &BB == Succ) && !IsTailCall) || (IsTailCall && !SuccSym))
      continue;

    std::vector<BinaryBasicBlock *> Preds = {BB.pred_begin(), BB.pred_end()};

    for (BinaryBasicBlock *Pred : Preds) {
      if (Pred->isLandingPad())
        continue;

      if (Pred->getSuccessor() == &BB ||
          (Pred->getConditionalSuccessor(true) == &BB && !IsTailCall) ||
          Pred->getConditionalSuccessor(false) == &BB)
        if (checkAndPatch(Pred, Succ, SuccSym) && MarkInvalid)
          BB.markValid(BB.pred_size() != 0 || BB.isLandingPad() ||
                       BB.isEntryPoint());
    }
  }

  return NumDoubleJumps;
}
} // namespace

bool SimplifyConditionalTailCalls::shouldRewriteBranch(
    const BinaryBasicBlock *PredBB, const MCInst &CondBranch,
    const BinaryBasicBlock *BB, const bool DirectionFlag) {
  if (BeenOptimized.count(PredBB))
    return false;

  const bool IsForward = BinaryFunction::isForwardBranch(PredBB, BB);

  if (IsForward)
    ++NumOrigForwardBranches;
  else
    ++NumOrigBackwardBranches;

  if (opts::SctcMode == opts::SctcAlways)
    return true;

  if (opts::SctcMode == opts::SctcPreserveDirection)
    return IsForward == DirectionFlag;

  const ErrorOr<std::pair<double, double>> Frequency =
      PredBB->getBranchStats(BB);

  // It's ok to rewrite the conditional branch if the new target will be
  // a backward branch.

  // If no data available for these branches, then it should be ok to
  // do the optimization since it will reduce code size.
  if (Frequency.getError())
    return true;

  // TODO: should this use misprediction frequency instead?
  const bool Result = (IsForward && Frequency.get().first >= 0.5) ||
                      (!IsForward && Frequency.get().first <= 0.5);

  return Result == DirectionFlag;
}

uint64_t SimplifyConditionalTailCalls::fixTailCalls(BinaryFunction &BF) {
  // Need updated indices to correctly detect branch' direction.
  BF.updateLayoutIndices();
  BF.markUnreachableBlocks();

  MCPlusBuilder *MIB = BF.getBinaryContext().MIB.get();
  MCContext *Ctx = BF.getBinaryContext().Ctx.get();
  uint64_t NumLocalCTCCandidates = 0;
  uint64_t NumLocalCTCs = 0;
  uint64_t LocalCTCTakenCount = 0;
  uint64_t LocalCTCExecCount = 0;
  std::vector<std::pair<BinaryBasicBlock *, const BinaryBasicBlock *>>
      NeedsUncondBranch;

  // Will block be deleted by UCE?
  auto isValid = [](const BinaryBasicBlock *BB) {
    return (BB->pred_size() != 0 || BB->isLandingPad() || BB->isEntryPoint());
  };

  for (BinaryBasicBlock *BB : BF.layout()) {
    // Locate BB with a single direct tail-call instruction.
    if (BB->getNumNonPseudos() != 1)
      continue;

    MCInst *Instr = BB->getFirstNonPseudoInstr();
    if (!MIB->isTailCall(*Instr) || MIB->isConditionalBranch(*Instr))
      continue;

    const MCSymbol *CalleeSymbol = MIB->getTargetSymbol(*Instr);
    if (!CalleeSymbol)
      continue;

    // Detect direction of the possible conditional tail call.
    const bool IsForwardCTC = BF.isForwardCall(CalleeSymbol);

    // Iterate through all predecessors.
    for (BinaryBasicBlock *PredBB : BB->predecessors()) {
      BinaryBasicBlock *CondSucc = PredBB->getConditionalSuccessor(true);
      if (!CondSucc)
        continue;

      ++NumLocalCTCCandidates;

      const MCSymbol *TBB = nullptr;
      const MCSymbol *FBB = nullptr;
      MCInst *CondBranch = nullptr;
      MCInst *UncondBranch = nullptr;
      bool Result = PredBB->analyzeBranch(TBB, FBB, CondBranch, UncondBranch);

      // analyzeBranch() can fail due to unusual branch instructions, e.g. jrcxz
      if (!Result) {
        LLVM_DEBUG(dbgs() << "analyzeBranch failed in SCTC in block:\n";
                   PredBB->dump());
        continue;
      }

      assert(Result && "internal error analyzing conditional branch");
      assert(CondBranch && "conditional branch expected");

      // It's possible that PredBB is also a successor to BB that may have
      // been processed by a previous iteration of the SCTC loop, in which
      // case it may have been marked invalid.  We should skip rewriting in
      // this case.
      if (!PredBB->isValid()) {
        assert(PredBB->isSuccessor(BB) &&
               "PredBB should be valid if it is not a successor to BB");
        continue;
      }

      // We don't want to reverse direction of the branch in new order
      // without further profile analysis.
      const bool DirectionFlag = CondSucc == BB ? IsForwardCTC : !IsForwardCTC;
      if (!shouldRewriteBranch(PredBB, *CondBranch, BB, DirectionFlag))
        continue;

      // Record this block so that we don't try to optimize it twice.
      BeenOptimized.insert(PredBB);

      uint64_t Count = 0;
      if (CondSucc != BB) {
        // Patch the new target address into the conditional branch.
        MIB->reverseBranchCondition(*CondBranch, CalleeSymbol, Ctx);
        // Since we reversed the condition on the branch we need to change
        // the target for the unconditional branch or add a unconditional
        // branch to the old target.  This has to be done manually since
        // fixupBranches is not called after SCTC.
        NeedsUncondBranch.emplace_back(PredBB, CondSucc);
        Count = PredBB->getFallthroughBranchInfo().Count;
      } else {
        // Change destination of the conditional branch.
        MIB->replaceBranchTarget(*CondBranch, CalleeSymbol, Ctx);
        Count = PredBB->getTakenBranchInfo().Count;
      }
      const uint64_t CTCTakenFreq =
          Count == BinaryBasicBlock::COUNT_NO_PROFILE ? 0 : Count;

      // Annotate it, so "isCall" returns true for this jcc
      MIB->setConditionalTailCall(*CondBranch);
      // Add info abount the conditional tail call frequency, otherwise this
      // info will be lost when we delete the associated BranchInfo entry
      auto &CTCAnnotation =
          MIB->getOrCreateAnnotationAs<uint64_t>(*CondBranch, "CTCTakenCount");
      CTCAnnotation = CTCTakenFreq;

      // Remove the unused successor which may be eliminated later
      // if there are no other users.
      PredBB->removeSuccessor(BB);
      // Update BB execution count
      if (CTCTakenFreq && CTCTakenFreq <= BB->getKnownExecutionCount())
        BB->setExecutionCount(BB->getExecutionCount() - CTCTakenFreq);
      else if (CTCTakenFreq > BB->getKnownExecutionCount())
        BB->setExecutionCount(0);

      ++NumLocalCTCs;
      LocalCTCTakenCount += CTCTakenFreq;
      LocalCTCExecCount += PredBB->getKnownExecutionCount();
    }

    // Remove the block from CFG if all predecessors were removed.
    BB->markValid(isValid(BB));
  }

  // Add unconditional branches at the end of BBs to new successors
  // as long as the successor is not a fallthrough.
  for (auto &Entry : NeedsUncondBranch) {
    BinaryBasicBlock *PredBB = Entry.first;
    const BinaryBasicBlock *CondSucc = Entry.second;

    const MCSymbol *TBB = nullptr;
    const MCSymbol *FBB = nullptr;
    MCInst *CondBranch = nullptr;
    MCInst *UncondBranch = nullptr;
    PredBB->analyzeBranch(TBB, FBB, CondBranch, UncondBranch);

    // Find the next valid block.  Invalid blocks will be deleted
    // so they shouldn't be considered fallthrough targets.
    const BinaryBasicBlock *NextBlock = BF.getBasicBlockAfter(PredBB, false);
    while (NextBlock && !isValid(NextBlock))
      NextBlock = BF.getBasicBlockAfter(NextBlock, false);

    // Get the unconditional successor to this block.
    const BinaryBasicBlock *PredSucc = PredBB->getSuccessor();
    assert(PredSucc && "The other branch should be a tail call");

    const bool HasFallthrough = (NextBlock && PredSucc == NextBlock);

    if (UncondBranch) {
      if (HasFallthrough)
        PredBB->eraseInstruction(PredBB->findInstruction(UncondBranch));
      else
        MIB->replaceBranchTarget(*UncondBranch, CondSucc->getLabel(), Ctx);
    } else if (!HasFallthrough) {
      MCInst Branch;
      MIB->createUncondBranch(Branch, CondSucc->getLabel(), Ctx);
      PredBB->addInstruction(Branch);
    }
  }

  if (NumLocalCTCs > 0) {
    NumDoubleJumps += fixDoubleJumps(BF, true);
    // Clean-up unreachable tail-call blocks.
    const std::pair<unsigned, uint64_t> Stats = BF.eraseInvalidBBs();
    DeletedBlocks += Stats.first;
    DeletedBytes += Stats.second;

    assert(BF.validateCFG());
  }

  LLVM_DEBUG(dbgs() << "BOLT: created " << NumLocalCTCs
                    << " conditional tail calls from a total of "
                    << NumLocalCTCCandidates << " candidates in function " << BF
                    << ". CTCs execution count for this function is "
                    << LocalCTCExecCount << " and CTC taken count is "
                    << LocalCTCTakenCount << "\n";);

  NumTailCallsPatched += NumLocalCTCs;
  NumCandidateTailCalls += NumLocalCTCCandidates;
  CTCExecCount += LocalCTCExecCount;
  CTCTakenCount += LocalCTCTakenCount;

  return NumLocalCTCs > 0;
}

void SimplifyConditionalTailCalls::runOnFunctions(BinaryContext &BC) {
  if (!BC.isX86())
    return;

  for (auto &It : BC.getBinaryFunctions()) {
    BinaryFunction &Function = It.second;

    if (!shouldOptimize(Function))
      continue;

    if (fixTailCalls(Function)) {
      Modified.insert(&Function);
      Function.setHasCanonicalCFG(false);
    }
  }

  outs() << "BOLT-INFO: SCTC: patched " << NumTailCallsPatched
         << " tail calls (" << NumOrigForwardBranches << " forward)"
         << " tail calls (" << NumOrigBackwardBranches << " backward)"
         << " from a total of " << NumCandidateTailCalls << " while removing "
         << NumDoubleJumps << " double jumps"
         << " and removing " << DeletedBlocks << " basic blocks"
         << " totalling " << DeletedBytes
         << " bytes of code. CTCs total execution count is " << CTCExecCount
         << " and the number of times CTCs are taken is " << CTCTakenCount
         << ".\n";
}

uint64_t ShortenInstructions::shortenInstructions(BinaryFunction &Function) {
  uint64_t Count = 0;
  const BinaryContext &BC = Function.getBinaryContext();
  for (BinaryBasicBlock &BB : Function) {
    for (MCInst &Inst : BB) {
      MCInst OriginalInst;
      if (opts::Verbosity > 2)
        OriginalInst = Inst;

      if (!BC.MIB->shortenInstruction(Inst))
        continue;

      if (opts::Verbosity > 2) {
        outs() << "BOLT-INFO: shortening:\nBOLT-INFO:    ";
        BC.printInstruction(outs(), OriginalInst, 0, &Function);
        outs() << "BOLT-INFO: to:";
        BC.printInstruction(outs(), Inst, 0, &Function);
      }

      ++Count;
    }
  }

  return Count;
}

void ShortenInstructions::runOnFunctions(BinaryContext &BC) {
  std::atomic<uint64_t> NumShortened{0};
  if (!BC.isX86())
    return;

  ParallelUtilities::runOnEachFunction(
      BC, ParallelUtilities::SchedulingPolicy::SP_INST_LINEAR,
      [&](BinaryFunction &BF) { NumShortened += shortenInstructions(BF); },
      nullptr, "ShortenInstructions");

  outs() << "BOLT-INFO: " << NumShortened << " instructions were shortened\n";
}

void Peepholes::addTailcallTraps(BinaryFunction &Function) {
  MCPlusBuilder *MIB = Function.getBinaryContext().MIB.get();
  for (BinaryBasicBlock &BB : Function) {
    MCInst *Inst = BB.getLastNonPseudoInstr();
    if (Inst && MIB->isTailCall(*Inst) && MIB->isIndirectBranch(*Inst)) {
      MCInst Trap;
      if (MIB->createTrap(Trap)) {
        BB.addInstruction(Trap);
        ++TailCallTraps;
      }
    }
  }
}

void Peepholes::removeUselessCondBranches(BinaryFunction &Function) {
  for (BinaryBasicBlock &BB : Function) {
    if (BB.succ_size() != 2)
      continue;

    BinaryBasicBlock *CondBB = BB.getConditionalSuccessor(true);
    BinaryBasicBlock *UncondBB = BB.getConditionalSuccessor(false);
    if (CondBB != UncondBB)
      continue;

    const MCSymbol *TBB = nullptr;
    const MCSymbol *FBB = nullptr;
    MCInst *CondBranch = nullptr;
    MCInst *UncondBranch = nullptr;
    bool Result = BB.analyzeBranch(TBB, FBB, CondBranch, UncondBranch);

    // analyzeBranch() can fail due to unusual branch instructions,
    // e.g. jrcxz, or jump tables (indirect jump).
    if (!Result || !CondBranch)
      continue;

    BB.removeDuplicateConditionalSuccessor(CondBranch);
    ++NumUselessCondBranches;
  }
}

void Peepholes::runOnFunctions(BinaryContext &BC) {
  const char Opts = std::accumulate(
      opts::Peepholes.begin(), opts::Peepholes.end(), 0,
      [](const char A, const opts::PeepholeOpts B) { return A | B; });
  if (Opts == opts::PEEP_NONE || !BC.isX86())
    return;

  for (auto &It : BC.getBinaryFunctions()) {
    BinaryFunction &Function = It.second;
    if (shouldOptimize(Function)) {
      if (Opts & opts::PEEP_DOUBLE_JUMPS)
        NumDoubleJumps += fixDoubleJumps(Function, false);
      if (Opts & opts::PEEP_TAILCALL_TRAPS)
        addTailcallTraps(Function);
      if (Opts & opts::PEEP_USELESS_BRANCHES)
        removeUselessCondBranches(Function);
      assert(Function.validateCFG());
    }
  }
  outs() << "BOLT-INFO: Peephole: " << NumDoubleJumps
         << " double jumps patched.\n"
         << "BOLT-INFO: Peephole: " << TailCallTraps
         << " tail call traps inserted.\n"
         << "BOLT-INFO: Peephole: " << NumUselessCondBranches
         << " useless conditional branches removed.\n";
}

bool SimplifyRODataLoads::simplifyRODataLoads(BinaryFunction &BF) {
  BinaryContext &BC = BF.getBinaryContext();
  MCPlusBuilder *MIB = BC.MIB.get();

  uint64_t NumLocalLoadsSimplified = 0;
  uint64_t NumDynamicLocalLoadsSimplified = 0;
  uint64_t NumLocalLoadsFound = 0;
  uint64_t NumDynamicLocalLoadsFound = 0;

  for (BinaryBasicBlock *BB : BF.layout()) {
    for (MCInst &Inst : *BB) {
      unsigned Opcode = Inst.getOpcode();
      const MCInstrDesc &Desc = BC.MII->get(Opcode);

      // Skip instructions that do not load from memory.
      if (!Desc.mayLoad())
        continue;

      // Try to statically evaluate the target memory address;
      uint64_t TargetAddress;

      if (MIB->hasPCRelOperand(Inst)) {
        // Try to find the symbol that corresponds to the PC-relative operand.
        MCOperand *DispOpI = MIB->getMemOperandDisp(Inst);
        assert(DispOpI != Inst.end() && "expected PC-relative displacement");
        assert(DispOpI->isExpr() &&
               "found PC-relative with non-symbolic displacement");

        // Get displacement symbol.
        const MCSymbol *DisplSymbol;
        uint64_t DisplOffset;

        std::tie(DisplSymbol, DisplOffset) =
            MIB->getTargetSymbolInfo(DispOpI->getExpr());

        if (!DisplSymbol)
          continue;

        // Look up the symbol address in the global symbols map of the binary
        // context object.
        BinaryData *BD = BC.getBinaryDataByName(DisplSymbol->getName());
        if (!BD)
          continue;
        TargetAddress = BD->getAddress() + DisplOffset;
      } else if (!MIB->evaluateMemOperandTarget(Inst, TargetAddress)) {
        continue;
      }

      // Get the contents of the section containing the target address of the
      // memory operand. We are only interested in read-only sections.
      ErrorOr<BinarySection &> DataSection =
          BC.getSectionForAddress(TargetAddress);
      if (!DataSection || !DataSection->isReadOnly())
        continue;

      if (BC.getRelocationAt(TargetAddress) ||
          BC.getDynamicRelocationAt(TargetAddress))
        continue;

      uint32_t Offset = TargetAddress - DataSection->getAddress();
      StringRef ConstantData = DataSection->getContents();

      ++NumLocalLoadsFound;
      if (BB->hasProfile())
        NumDynamicLocalLoadsFound += BB->getExecutionCount();

      if (MIB->replaceMemOperandWithImm(Inst, ConstantData, Offset)) {
        ++NumLocalLoadsSimplified;
        if (BB->hasProfile())
          NumDynamicLocalLoadsSimplified += BB->getExecutionCount();
      }
    }
  }

  NumLoadsFound += NumLocalLoadsFound;
  NumDynamicLoadsFound += NumDynamicLocalLoadsFound;
  NumLoadsSimplified += NumLocalLoadsSimplified;
  NumDynamicLoadsSimplified += NumDynamicLocalLoadsSimplified;

  return NumLocalLoadsSimplified > 0;
}

void SimplifyRODataLoads::runOnFunctions(BinaryContext &BC) {
  for (auto &It : BC.getBinaryFunctions()) {
    BinaryFunction &Function = It.second;
    if (shouldOptimize(Function) && simplifyRODataLoads(Function))
      Modified.insert(&Function);
  }

  outs() << "BOLT-INFO: simplified " << NumLoadsSimplified << " out of "
         << NumLoadsFound << " loads from a statically computed address.\n"
         << "BOLT-INFO: dynamic loads simplified: " << NumDynamicLoadsSimplified
         << "\n"
         << "BOLT-INFO: dynamic loads found: " << NumDynamicLoadsFound << "\n";
}

void AssignSections::runOnFunctions(BinaryContext &BC) {
  for (BinaryFunction *Function : BC.getInjectedBinaryFunctions()) {
    Function->setCodeSectionName(BC.getInjectedCodeSectionName());
    Function->setColdCodeSectionName(BC.getInjectedColdCodeSectionName());
  }

  // In non-relocation mode functions have pre-assigned section names.
  if (!BC.HasRelocations)
    return;

  const bool UseColdSection =
      BC.NumProfiledFuncs > 0 ||
      opts::ReorderFunctions == ReorderFunctions::RT_USER;
  for (auto &BFI : BC.getBinaryFunctions()) {
    BinaryFunction &Function = BFI.second;
    if (opts::isHotTextMover(Function)) {
      Function.setCodeSectionName(BC.getHotTextMoverSectionName());
      Function.setColdCodeSectionName(BC.getHotTextMoverSectionName());
      continue;
    }

    if (!UseColdSection || Function.hasValidIndex() ||
        Function.hasValidProfile())
      Function.setCodeSectionName(BC.getMainCodeSectionName());
    else
      Function.setCodeSectionName(BC.getColdCodeSectionName());

    if (Function.isSplit())
      Function.setColdCodeSectionName(BC.getColdCodeSectionName());
  }
}

void PrintProfileStats::runOnFunctions(BinaryContext &BC) {
  double FlowImbalanceMean = 0.0;
  size_t NumBlocksConsidered = 0;
  double WorstBias = 0.0;
  const BinaryFunction *WorstBiasFunc = nullptr;

  // For each function CFG, we fill an IncomingMap with the sum of the frequency
  // of incoming edges for each BB. Likewise for each OutgoingMap and the sum
  // of the frequency of outgoing edges.
  using FlowMapTy = std::unordered_map<const BinaryBasicBlock *, uint64_t>;
  std::unordered_map<const BinaryFunction *, FlowMapTy> TotalIncomingMaps;
  std::unordered_map<const BinaryFunction *, FlowMapTy> TotalOutgoingMaps;

  // Compute mean
  for (const auto &BFI : BC.getBinaryFunctions()) {
    const BinaryFunction &Function = BFI.second;
    if (Function.empty() || !Function.isSimple())
      continue;
    FlowMapTy &IncomingMap = TotalIncomingMaps[&Function];
    FlowMapTy &OutgoingMap = TotalOutgoingMaps[&Function];
    for (const BinaryBasicBlock &BB : Function) {
      uint64_t TotalOutgoing = 0ULL;
      auto SuccBIIter = BB.branch_info_begin();
      for (BinaryBasicBlock *Succ : BB.successors()) {
        uint64_t Count = SuccBIIter->Count;
        if (Count == BinaryBasicBlock::COUNT_NO_PROFILE || Count == 0) {
          ++SuccBIIter;
          continue;
        }
        TotalOutgoing += Count;
        IncomingMap[Succ] += Count;
        ++SuccBIIter;
      }
      OutgoingMap[&BB] = TotalOutgoing;
    }

    size_t NumBlocks = 0;
    double Mean = 0.0;
    for (const BinaryBasicBlock &BB : Function) {
      // Do not compute score for low frequency blocks, entry or exit blocks
      if (IncomingMap[&BB] < 100 || OutgoingMap[&BB] == 0 || BB.isEntryPoint())
        continue;
      ++NumBlocks;
      const double Difference = (double)OutgoingMap[&BB] - IncomingMap[&BB];
      Mean += fabs(Difference / IncomingMap[&BB]);
    }

    FlowImbalanceMean += Mean;
    NumBlocksConsidered += NumBlocks;
    if (!NumBlocks)
      continue;
    double FuncMean = Mean / NumBlocks;
    if (FuncMean > WorstBias) {
      WorstBias = FuncMean;
      WorstBiasFunc = &Function;
    }
  }
  if (NumBlocksConsidered > 0)
    FlowImbalanceMean /= NumBlocksConsidered;

  // Compute standard deviation
  NumBlocksConsidered = 0;
  double FlowImbalanceVar = 0.0;
  for (const auto &BFI : BC.getBinaryFunctions()) {
    const BinaryFunction &Function = BFI.second;
    if (Function.empty() || !Function.isSimple())
      continue;
    FlowMapTy &IncomingMap = TotalIncomingMaps[&Function];
    FlowMapTy &OutgoingMap = TotalOutgoingMaps[&Function];
    for (const BinaryBasicBlock &BB : Function) {
      if (IncomingMap[&BB] < 100 || OutgoingMap[&BB] == 0)
        continue;
      ++NumBlocksConsidered;
      const double Difference = (double)OutgoingMap[&BB] - IncomingMap[&BB];
      FlowImbalanceVar +=
          pow(fabs(Difference / IncomingMap[&BB]) - FlowImbalanceMean, 2);
    }
  }
  if (NumBlocksConsidered) {
    FlowImbalanceVar /= NumBlocksConsidered;
    FlowImbalanceVar = sqrt(FlowImbalanceVar);
  }

  // Report to user
  outs() << format("BOLT-INFO: Profile bias score: %.4lf%% StDev: %.4lf%%\n",
                   (100.0 * FlowImbalanceMean), (100.0 * FlowImbalanceVar));
  if (WorstBiasFunc && opts::Verbosity >= 1) {
    outs() << "Worst average bias observed in " << WorstBiasFunc->getPrintName()
           << "\n";
    LLVM_DEBUG(WorstBiasFunc->dump());
  }
}

void PrintProgramStats::runOnFunctions(BinaryContext &BC) {
  uint64_t NumRegularFunctions = 0;
  uint64_t NumStaleProfileFunctions = 0;
  uint64_t NumNonSimpleProfiledFunctions = 0;
  uint64_t NumUnknownControlFlowFunctions = 0;
  uint64_t TotalSampleCount = 0;
  uint64_t StaleSampleCount = 0;
  std::vector<const BinaryFunction *> ProfiledFunctions;
  const char *StaleFuncsHeader = "BOLT-INFO: Functions with stale profile:\n";
  for (auto &BFI : BC.getBinaryFunctions()) {
    const BinaryFunction &Function = BFI.second;

    // Ignore PLT functions for stats.
    if (Function.isPLTFunction())
      continue;

    ++NumRegularFunctions;

    if (!Function.isSimple()) {
      if (Function.hasProfile())
        ++NumNonSimpleProfiledFunctions;
      continue;
    }

    if (Function.hasUnknownControlFlow()) {
      if (opts::PrintUnknownCFG)
        Function.dump();
      else if (opts::PrintUnknown)
        errs() << "function with unknown control flow: " << Function << '\n';

      ++NumUnknownControlFlowFunctions;
    }

    if (!Function.hasProfile())
      continue;

    uint64_t SampleCount = Function.getRawBranchCount();
    TotalSampleCount += SampleCount;

    if (Function.hasValidProfile()) {
      ProfiledFunctions.push_back(&Function);
    } else {
      if (opts::ReportStaleFuncs) {
        outs() << StaleFuncsHeader;
        StaleFuncsHeader = "";
        outs() << "  " << Function << '\n';
      }
      ++NumStaleProfileFunctions;
      StaleSampleCount += SampleCount;
    }
  }
  BC.NumProfiledFuncs = ProfiledFunctions.size();

  const size_t NumAllProfiledFunctions =
      ProfiledFunctions.size() + NumStaleProfileFunctions;
  outs() << "BOLT-INFO: " << NumAllProfiledFunctions << " out of "
         << NumRegularFunctions << " functions in the binary ("
         << format("%.1f", NumAllProfiledFunctions /
                               (float)NumRegularFunctions * 100.0f)
         << "%) have non-empty execution profile\n";
  if (NumNonSimpleProfiledFunctions) {
    outs() << "BOLT-INFO: " << NumNonSimpleProfiledFunctions << " function"
           << (NumNonSimpleProfiledFunctions == 1 ? "" : "s")
           << " with profile could not be optimized\n";
  }
  if (NumStaleProfileFunctions) {
    const float PctStale =
        NumStaleProfileFunctions / (float)NumAllProfiledFunctions * 100.0f;
    auto printErrorOrWarning = [&]() {
      if (PctStale > opts::StaleThreshold)
        errs() << "BOLT-ERROR: ";
      else
        errs() << "BOLT-WARNING: ";
    };
    printErrorOrWarning();
    errs() << NumStaleProfileFunctions
           << format(" (%.1f%% of all profiled)", PctStale) << " function"
           << (NumStaleProfileFunctions == 1 ? "" : "s")
           << " have invalid (possibly stale) profile."
              " Use -report-stale to see the list.\n";
    if (TotalSampleCount > 0) {
      printErrorOrWarning();
      errs() << StaleSampleCount << " out of " << TotalSampleCount
             << " samples in the binary ("
             << format("%.1f", ((100.0f * StaleSampleCount) / TotalSampleCount))
             << "%) belong to functions with invalid"
                " (possibly stale) profile.\n";
    }
    if (PctStale > opts::StaleThreshold) {
      errs() << "BOLT-ERROR: stale functions exceed specified threshold of "
             << opts::StaleThreshold << "%. Exiting.\n";
      exit(1);
    }
  }

  if (const uint64_t NumUnusedObjects = BC.getNumUnusedProfiledObjects()) {
    outs() << "BOLT-INFO: profile for " << NumUnusedObjects
           << " objects was ignored\n";
  }

  if (ProfiledFunctions.size() > 10) {
    if (opts::Verbosity >= 1) {
      outs() << "BOLT-INFO: top called functions are:\n";
      std::sort(ProfiledFunctions.begin(), ProfiledFunctions.end(),
                [](const BinaryFunction *A, const BinaryFunction *B) {
                  return B->getExecutionCount() < A->getExecutionCount();
                });
      auto SFI = ProfiledFunctions.begin();
      auto SFIend = ProfiledFunctions.end();
      for (unsigned I = 0u; I < opts::TopCalledLimit && SFI != SFIend;
           ++SFI, ++I)
        outs() << "  " << **SFI << " : " << (*SFI)->getExecutionCount() << '\n';
    }
  }

  if (!opts::PrintSortedBy.empty() &&
      std::find(opts::PrintSortedBy.begin(), opts::PrintSortedBy.end(),
                DynoStats::FIRST_DYNO_STAT) == opts::PrintSortedBy.end()) {

    std::vector<const BinaryFunction *> Functions;
    std::map<const BinaryFunction *, DynoStats> Stats;

    for (const auto &BFI : BC.getBinaryFunctions()) {
      const BinaryFunction &BF = BFI.second;
      if (shouldOptimize(BF) && BF.hasValidProfile()) {
        Functions.push_back(&BF);
        Stats.emplace(&BF, getDynoStats(BF));
      }
    }

    const bool SortAll =
        std::find(opts::PrintSortedBy.begin(), opts::PrintSortedBy.end(),
                  DynoStats::LAST_DYNO_STAT) != opts::PrintSortedBy.end();

    const bool Ascending =
        opts::DynoStatsSortOrderOpt == opts::DynoStatsSortOrder::Ascending;

    if (SortAll) {
      std::stable_sort(Functions.begin(), Functions.end(),
                       [Ascending, &Stats](const BinaryFunction *A,
                                           const BinaryFunction *B) {
                         return Ascending ? Stats.at(A) < Stats.at(B)
                                          : Stats.at(B) < Stats.at(A);
                       });
    } else {
      std::stable_sort(
          Functions.begin(), Functions.end(),
          [Ascending, &Stats](const BinaryFunction *A,
                              const BinaryFunction *B) {
            const DynoStats &StatsA = Stats.at(A);
            const DynoStats &StatsB = Stats.at(B);
            return Ascending ? StatsA.lessThan(StatsB, opts::PrintSortedBy)
                             : StatsB.lessThan(StatsA, opts::PrintSortedBy);
          });
    }

    outs() << "BOLT-INFO: top functions sorted by ";
    if (SortAll) {
      outs() << "dyno stats";
    } else {
      outs() << "(";
      bool PrintComma = false;
      for (const DynoStats::Category Category : opts::PrintSortedBy) {
        if (PrintComma)
          outs() << ", ";
        outs() << DynoStats::Description(Category);
        PrintComma = true;
      }
      outs() << ")";
    }

    outs() << " are:\n";
    auto SFI = Functions.begin();
    for (unsigned I = 0; I < 100 && SFI != Functions.end(); ++SFI, ++I) {
      const DynoStats Stats = getDynoStats(**SFI);
      outs() << "  " << **SFI;
      if (!SortAll) {
        outs() << " (";
        bool PrintComma = false;
        for (const DynoStats::Category Category : opts::PrintSortedBy) {
          if (PrintComma)
            outs() << ", ";
          outs() << dynoStatsOptName(Category) << "=" << Stats[Category];
          PrintComma = true;
        }
        outs() << ")";
      }
      outs() << "\n";
    }
  }

  if (!BC.TrappedFunctions.empty()) {
    errs() << "BOLT-WARNING: " << BC.TrappedFunctions.size() << " function"
           << (BC.TrappedFunctions.size() > 1 ? "s" : "")
           << " will trap on entry. Use -trap-avx512=0 to disable"
              " traps.";
    if (opts::Verbosity >= 1 || BC.TrappedFunctions.size() <= 5) {
      errs() << '\n';
      for (const BinaryFunction *Function : BC.TrappedFunctions)
        errs() << "  " << *Function << '\n';
    } else {
      errs() << " Use -v=1 to see the list.\n";
    }
  }

  // Print information on missed macro-fusion opportunities seen on input.
  if (BC.MissedMacroFusionPairs) {
    outs() << "BOLT-INFO: the input contains " << BC.MissedMacroFusionPairs
           << " (dynamic count : " << BC.MissedMacroFusionExecCount
           << ") opportunities for macro-fusion optimization";
    switch (opts::AlignMacroOpFusion) {
    case MFT_NONE:
      outs() << ". Use -align-macro-fusion to fix.\n";
      break;
    case MFT_HOT:
      outs() << ". Will fix instances on a hot path.\n";
      break;
    case MFT_ALL:
      outs() << " that are going to be fixed\n";
      break;
    }
  }

  // Collect and print information about suboptimal code layout on input.
  if (opts::ReportBadLayout) {
    std::vector<const BinaryFunction *> SuboptimalFuncs;
    for (auto &BFI : BC.getBinaryFunctions()) {
      const BinaryFunction &BF = BFI.second;
      if (!BF.hasValidProfile())
        continue;

      const uint64_t HotThreshold =
          std::max<uint64_t>(BF.getKnownExecutionCount(), 1);
      bool HotSeen = false;
      for (const BinaryBasicBlock *BB : BF.rlayout()) {
        if (!HotSeen && BB->getKnownExecutionCount() > HotThreshold) {
          HotSeen = true;
          continue;
        }
        if (HotSeen && BB->getKnownExecutionCount() == 0) {
          SuboptimalFuncs.push_back(&BF);
          break;
        }
      }
    }

    if (!SuboptimalFuncs.empty()) {
      std::sort(SuboptimalFuncs.begin(), SuboptimalFuncs.end(),
                [](const BinaryFunction *A, const BinaryFunction *B) {
                  return A->getKnownExecutionCount() / A->getSize() >
                         B->getKnownExecutionCount() / B->getSize();
                });

      outs() << "BOLT-INFO: " << SuboptimalFuncs.size()
             << " functions have "
                "cold code in the middle of hot code. Top functions are:\n";
      for (unsigned I = 0;
           I < std::min(static_cast<size_t>(opts::ReportBadLayout),
                        SuboptimalFuncs.size());
           ++I)
        SuboptimalFuncs[I]->print(outs());
    }
  }

  if (NumUnknownControlFlowFunctions) {
    outs() << "BOLT-INFO: " << NumUnknownControlFlowFunctions
           << " functions have instructions with unknown control flow";
    if (!opts::PrintUnknown)
      outs() << ". Use -print-unknown to see the list.";
    outs() << '\n';
  }
}

void InstructionLowering::runOnFunctions(BinaryContext &BC) {
  for (auto &BFI : BC.getBinaryFunctions())
    for (BinaryBasicBlock &BB : BFI.second)
      for (MCInst &Instruction : BB)
        BC.MIB->lowerTailCall(Instruction);
}

void StripRepRet::runOnFunctions(BinaryContext &BC) {
  uint64_t NumPrefixesRemoved = 0;
  uint64_t NumBytesSaved = 0;
  for (auto &BFI : BC.getBinaryFunctions()) {
    for (BinaryBasicBlock &BB : BFI.second) {
      auto LastInstRIter = BB.getLastNonPseudo();
      if (LastInstRIter == BB.rend() || !BC.MIB->isReturn(*LastInstRIter) ||
          !BC.MIB->deleteREPPrefix(*LastInstRIter))
        continue;

      NumPrefixesRemoved += BB.getKnownExecutionCount();
      ++NumBytesSaved;
    }
  }

  if (NumBytesSaved)
    outs() << "BOLT-INFO: removed " << NumBytesSaved
           << " 'repz' prefixes"
              " with estimated execution count of "
           << NumPrefixesRemoved << " times.\n";
}

void InlineMemcpy::runOnFunctions(BinaryContext &BC) {
  if (!BC.isX86())
    return;

  uint64_t NumInlined = 0;
  uint64_t NumInlinedDyno = 0;
  for (auto &BFI : BC.getBinaryFunctions()) {
    for (BinaryBasicBlock &BB : BFI.second) {
      for (auto II = BB.begin(); II != BB.end(); ++II) {
        MCInst &Inst = *II;

        if (!BC.MIB->isCall(Inst) || MCPlus::getNumPrimeOperands(Inst) != 1 ||
            !Inst.getOperand(0).isExpr())
          continue;

        const MCSymbol *CalleeSymbol = BC.MIB->getTargetSymbol(Inst);
        if (CalleeSymbol->getName() != "memcpy" &&
            CalleeSymbol->getName() != "memcpy@PLT" &&
            CalleeSymbol->getName() != "_memcpy8")
          continue;

        const bool IsMemcpy8 = (CalleeSymbol->getName() == "_memcpy8");
        const bool IsTailCall = BC.MIB->isTailCall(Inst);

        const InstructionListType NewCode =
            BC.MIB->createInlineMemcpy(IsMemcpy8);
        II = BB.replaceInstruction(II, NewCode);
        std::advance(II, NewCode.size() - 1);
        if (IsTailCall) {
          MCInst Return;
          BC.MIB->createReturn(Return);
          II = BB.insertInstruction(std::next(II), std::move(Return));
        }

        ++NumInlined;
        NumInlinedDyno += BB.getKnownExecutionCount();
      }
    }
  }

  if (NumInlined) {
    outs() << "BOLT-INFO: inlined " << NumInlined << " memcpy() calls";
    if (NumInlinedDyno)
      outs() << ". The calls were executed " << NumInlinedDyno
             << " times based on profile.";
    outs() << '\n';
  }
}

bool SpecializeMemcpy1::shouldOptimize(const BinaryFunction &Function) const {
  if (!BinaryFunctionPass::shouldOptimize(Function))
    return false;

  for (const std::string &FunctionSpec : Spec) {
    StringRef FunctionName = StringRef(FunctionSpec).split(':').first;
    if (Function.hasNameRegex(FunctionName))
      return true;
  }

  return false;
}

std::set<size_t> SpecializeMemcpy1::getCallSitesToOptimize(
    const BinaryFunction &Function) const {
  StringRef SitesString;
  for (const std::string &FunctionSpec : Spec) {
    StringRef FunctionName;
    std::tie(FunctionName, SitesString) = StringRef(FunctionSpec).split(':');
    if (Function.hasNameRegex(FunctionName))
      break;
    SitesString = "";
  }

  std::set<size_t> Sites;
  SmallVector<StringRef, 4> SitesVec;
  SitesString.split(SitesVec, ':');
  for (StringRef SiteString : SitesVec) {
    if (SiteString.empty())
      continue;
    size_t Result;
    if (!SiteString.getAsInteger(10, Result))
      Sites.emplace(Result);
  }

  return Sites;
}

void SpecializeMemcpy1::runOnFunctions(BinaryContext &BC) {
  if (!BC.isX86())
    return;

  uint64_t NumSpecialized = 0;
  uint64_t NumSpecializedDyno = 0;
  for (auto &BFI : BC.getBinaryFunctions()) {
    BinaryFunction &Function = BFI.second;
    if (!shouldOptimize(Function))
      continue;

    std::set<size_t> CallsToOptimize = getCallSitesToOptimize(Function);
    auto shouldOptimize = [&](size_t N) {
      return CallsToOptimize.empty() || CallsToOptimize.count(N);
    };

    std::vector<BinaryBasicBlock *> Blocks(Function.pbegin(), Function.pend());
    size_t CallSiteID = 0;
    for (BinaryBasicBlock *CurBB : Blocks) {
      for (auto II = CurBB->begin(); II != CurBB->end(); ++II) {
        MCInst &Inst = *II;

        if (!BC.MIB->isCall(Inst) || MCPlus::getNumPrimeOperands(Inst) != 1 ||
            !Inst.getOperand(0).isExpr())
          continue;

        const MCSymbol *CalleeSymbol = BC.MIB->getTargetSymbol(Inst);
        if (CalleeSymbol->getName() != "memcpy" &&
            CalleeSymbol->getName() != "memcpy@PLT")
          continue;

        if (BC.MIB->isTailCall(Inst))
          continue;

        ++CallSiteID;

        if (!shouldOptimize(CallSiteID))
          continue;

        // Create a copy of a call to memcpy(dest, src, size).
        MCInst MemcpyInstr = Inst;

        BinaryBasicBlock *OneByteMemcpyBB = CurBB->splitAt(II);

        BinaryBasicBlock *NextBB = nullptr;
        if (OneByteMemcpyBB->getNumNonPseudos() > 1) {
          NextBB = OneByteMemcpyBB->splitAt(OneByteMemcpyBB->begin());
          NextBB->eraseInstruction(NextBB->begin());
        } else {
          NextBB = OneByteMemcpyBB->getSuccessor();
          OneByteMemcpyBB->eraseInstruction(OneByteMemcpyBB->begin());
          assert(NextBB && "unexpected call to memcpy() with no return");
        }

        BinaryBasicBlock *MemcpyBB =
            Function.addBasicBlock(CurBB->getInputOffset());
        InstructionListType CmpJCC =
            BC.MIB->createCmpJE(BC.MIB->getIntArgRegister(2), 1,
                                OneByteMemcpyBB->getLabel(), BC.Ctx.get());
        CurBB->addInstructions(CmpJCC);
        CurBB->addSuccessor(MemcpyBB);

        MemcpyBB->addInstruction(std::move(MemcpyInstr));
        MemcpyBB->addSuccessor(NextBB);
        MemcpyBB->setCFIState(NextBB->getCFIState());
        MemcpyBB->setExecutionCount(0);

        // To prevent the actual call from being moved to cold, we set its
        // execution count to 1.
        if (CurBB->getKnownExecutionCount() > 0)
          MemcpyBB->setExecutionCount(1);

        InstructionListType OneByteMemcpy = BC.MIB->createOneByteMemcpy();
        OneByteMemcpyBB->addInstructions(OneByteMemcpy);

        ++NumSpecialized;
        NumSpecializedDyno += CurBB->getKnownExecutionCount();

        CurBB = NextBB;

        // Note: we don't expect the next instruction to be a call to memcpy.
        II = CurBB->begin();
      }
    }
  }

  if (NumSpecialized) {
    outs() << "BOLT-INFO: specialized " << NumSpecialized
           << " memcpy() call sites for size 1";
    if (NumSpecializedDyno)
      outs() << ". The calls were executed " << NumSpecializedDyno
             << " times based on profile.";
    outs() << '\n';
  }
}

void RemoveNops::runOnFunction(BinaryFunction &BF) {
  const BinaryContext &BC = BF.getBinaryContext();
  for (BinaryBasicBlock &BB : BF) {
    for (int64_t I = BB.size() - 1; I >= 0; --I) {
      MCInst &Inst = BB.getInstructionAtIndex(I);
      if (BC.MIB->isNoop(Inst) && BC.MIB->hasAnnotation(Inst, "NOP"))
        BB.eraseInstructionAtIndex(I);
    }
  }
}

void RemoveNops::runOnFunctions(BinaryContext &BC) {
  ParallelUtilities::WorkFuncTy WorkFun = [&](BinaryFunction &BF) {
    runOnFunction(BF);
  };

  ParallelUtilities::PredicateTy SkipFunc = [&](const BinaryFunction &BF) {
    return BF.shouldPreserveNops();
  };

  ParallelUtilities::runOnEachFunction(
      BC, ParallelUtilities::SchedulingPolicy::SP_INST_LINEAR, WorkFun,
      SkipFunc, "RemoveNops");
}

} // namespace bolt
} // namespace llvm