xref: /llvm-project/bolt/lib/Passes/ReorderFunctions.cpp (revision aa9cc721e58f086ba6a3f9711fefdb61a184f786)

//===- bolt/Passes/ReorderFunctions.cpp - Function reordering pass --------===//
//
// 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 ReorderFunctions class.
//
//===----------------------------------------------------------------------===//

#include "bolt/Passes/ReorderFunctions.h"
#include "bolt/Passes/HFSort.h"
#include "bolt/Utils/Utils.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Transforms/Utils/CodeLayout.h"
#include <fstream>

#define DEBUG_TYPE "hfsort"

using namespace llvm;

namespace opts {

extern cl::OptionCategory BoltOptCategory;
extern cl::opt<unsigned> Verbosity;
extern cl::opt<uint32_t> RandomSeed;

extern size_t padFunctionBefore(const bolt::BinaryFunction &Function);
extern size_t padFunctionAfter(const bolt::BinaryFunction &Function);

extern cl::opt<bolt::ReorderFunctions::ReorderType> ReorderFunctions;
cl::opt<bolt::ReorderFunctions::ReorderType> ReorderFunctions(
    "reorder-functions",
    cl::desc("reorder and cluster functions (works only with relocations)"),
    cl::init(bolt::ReorderFunctions::RT_NONE),
    cl::values(clEnumValN(bolt::ReorderFunctions::RT_NONE, "none",
                          "do not reorder functions"),
               clEnumValN(bolt::ReorderFunctions::RT_EXEC_COUNT, "exec-count",
                          "order by execution count"),
               clEnumValN(bolt::ReorderFunctions::RT_HFSORT, "hfsort",
                          "use hfsort algorithm"),
               clEnumValN(bolt::ReorderFunctions::RT_HFSORT_PLUS, "hfsort+",
                          "use cache-directed sort"),
               clEnumValN(bolt::ReorderFunctions::RT_CDSORT, "cdsort",
                          "use cache-directed sort"),
               clEnumValN(bolt::ReorderFunctions::RT_PETTIS_HANSEN,
                          "pettis-hansen", "use Pettis-Hansen algorithm"),
               clEnumValN(bolt::ReorderFunctions::RT_RANDOM, "random",
                          "reorder functions randomly"),
               clEnumValN(bolt::ReorderFunctions::RT_USER, "user",
                          "use function order specified by -function-order")),
    cl::ZeroOrMore, cl::cat(BoltOptCategory),
    cl::callback([](const bolt::ReorderFunctions::ReorderType &option) {
      if (option == bolt::ReorderFunctions::RT_HFSORT_PLUS) {
        errs() << "BOLT-WARNING: '-reorder-functions=hfsort+' is deprecated,"
               << " please use '-reorder-functions=cdsort' instead\n";
        ReorderFunctions = bolt::ReorderFunctions::RT_CDSORT;
      }
    }));

static cl::opt<bool> ReorderFunctionsUseHotSize(
    "reorder-functions-use-hot-size",
    cl::desc("use a function's hot size when doing clustering"), cl::init(true),
    cl::cat(BoltOptCategory));

static cl::opt<std::string> FunctionOrderFile(
    "function-order",
    cl::desc("file containing an ordered list of functions to use for function "
             "reordering"),
    cl::cat(BoltOptCategory));

static cl::opt<std::string> GenerateFunctionOrderFile(
    "generate-function-order",
    cl::desc("file to dump the ordered list of functions to use for function "
             "reordering"),
    cl::cat(BoltOptCategory));

static cl::opt<std::string> LinkSectionsFile(
    "generate-link-sections",
    cl::desc("generate a list of function sections in a format suitable for "
             "inclusion in a linker script"),
    cl::cat(BoltOptCategory));

static cl::opt<bool>
    UseEdgeCounts("use-edge-counts",
                  cl::desc("use edge count data when doing clustering"),
                  cl::init(true), cl::cat(BoltOptCategory));

static cl::opt<bool> CgFromPerfData(
    "cg-from-perf-data",
    cl::desc("use perf data directly when constructing the call graph"
             " for stale functions"),
    cl::init(true), cl::ZeroOrMore, cl::cat(BoltOptCategory));

static cl::opt<bool> CgIgnoreRecursiveCalls(
    "cg-ignore-recursive-calls",
    cl::desc("ignore recursive calls when constructing the call graph"),
    cl::init(true), cl::cat(BoltOptCategory));

static cl::opt<bool> CgUseSplitHotSize(
    "cg-use-split-hot-size",
    cl::desc("use hot/cold data on basic blocks to determine hot sizes for "
             "call graph functions"),
    cl::init(false), cl::ZeroOrMore, cl::cat(BoltOptCategory));

} // namespace opts

namespace llvm {
namespace bolt {

using NodeId = CallGraph::NodeId;
using Arc = CallGraph::Arc;
using Node = CallGraph::Node;

void ReorderFunctions::reorder(BinaryContext &BC,
                               std::vector<Cluster> &&Clusters,
                               std::map<uint64_t, BinaryFunction> &BFs) {
  std::vector<uint64_t> FuncAddr(Cg.numNodes()); // Just for computing stats
  uint64_t TotalSize = 0;
  uint32_t Index = 0;

  // Set order of hot functions based on clusters.
  for (const Cluster &Cluster : Clusters) {
    for (const NodeId FuncId : Cluster.targets()) {
      Cg.nodeIdToFunc(FuncId)->setIndex(Index++);
      FuncAddr[FuncId] = TotalSize;
      TotalSize += Cg.size(FuncId);
    }
  }

  // Assign valid index for functions with valid profile.
  for (auto &It : BFs) {
    BinaryFunction &BF = It.second;
    if (!BF.hasValidIndex() && BF.hasValidProfile())
      BF.setIndex(Index++);
  }

  if (opts::ReorderFunctions == RT_NONE)
    return;

  printStats(BC, Clusters, FuncAddr);
}

void ReorderFunctions::printStats(BinaryContext &BC,
                                  const std::vector<Cluster> &Clusters,
                                  const std::vector<uint64_t> &FuncAddr) {
  if (opts::Verbosity == 0) {
#ifndef NDEBUG
    if (!DebugFlag || !isCurrentDebugType("hfsort"))
      return;
#else
    return;
#endif
  }

  bool PrintDetailed = opts::Verbosity > 1;
#ifndef NDEBUG
  PrintDetailed |=
      (DebugFlag && isCurrentDebugType("hfsort") && opts::Verbosity > 0);
#endif
  uint64_t TotalSize = 0;
  uint64_t CurPage = 0;
  uint64_t Hotfuncs = 0;
  double TotalDistance = 0;
  double TotalCalls = 0;
  double TotalCalls64B = 0;
  double TotalCalls4KB = 0;
  double TotalCalls2MB = 0;
  if (PrintDetailed)
    BC.outs() << "BOLT-INFO: Function reordering page layout\n"
              << "BOLT-INFO: ============== page 0 ==============\n";
  for (const Cluster &Cluster : Clusters) {
    if (PrintDetailed)
      BC.outs() << format(
          "BOLT-INFO: -------- density = %.3lf (%u / %u) --------\n",
          Cluster.density(), Cluster.samples(), Cluster.size());

    for (NodeId FuncId : Cluster.targets()) {
      if (Cg.samples(FuncId) > 0) {
        Hotfuncs++;

        if (PrintDetailed)
          BC.outs() << "BOLT-INFO: hot func " << *Cg.nodeIdToFunc(FuncId)
                    << " (" << Cg.size(FuncId) << ")\n";

        uint64_t Dist = 0;
        uint64_t Calls = 0;
        for (NodeId Dst : Cg.successors(FuncId)) {
          if (FuncId == Dst) // ignore recursive calls in stats
            continue;
          const Arc &Arc = *Cg.findArc(FuncId, Dst);
          const auto D = std::abs(FuncAddr[Arc.dst()] -
                                  (FuncAddr[FuncId] + Arc.avgCallOffset()));
          const double W = Arc.weight();
          if (D < 64 && PrintDetailed && opts::Verbosity > 2)
            BC.outs() << "BOLT-INFO: short (" << D << "B) call:\n"
                      << "BOLT-INFO:   Src: " << *Cg.nodeIdToFunc(FuncId)
                      << "\n"
                      << "BOLT-INFO:   Dst: " << *Cg.nodeIdToFunc(Dst) << "\n"
                      << "BOLT-INFO:   Weight = " << W << "\n"
                      << "BOLT-INFO:   AvgOffset = " << Arc.avgCallOffset()
                      << "\n";
          Calls += W;
          if (D < 64)
            TotalCalls64B += W;
          if (D < 4096)
            TotalCalls4KB += W;
          if (D < (2 << 20))
            TotalCalls2MB += W;
          Dist += Arc.weight() * D;
          if (PrintDetailed)
            BC.outs() << format("BOLT-INFO: arc: %u [@%lu+%.1lf] -> %u [@%lu]: "
                                "weight = %.0lf, callDist = %f\n",
                                Arc.src(), FuncAddr[Arc.src()],
                                Arc.avgCallOffset(), Arc.dst(),
                                FuncAddr[Arc.dst()], Arc.weight(), D);
        }
        TotalCalls += Calls;
        TotalDistance += Dist;
        TotalSize += Cg.size(FuncId);

        if (PrintDetailed) {
          BC.outs() << format("BOLT-INFO: start = %6u : avgCallDist = %lu : ",
                              TotalSize, Calls ? Dist / Calls : 0)
                    << Cg.nodeIdToFunc(FuncId)->getPrintName() << '\n';
          const uint64_t NewPage = TotalSize / HugePageSize;
          if (NewPage != CurPage) {
            CurPage = NewPage;
            BC.outs() << format(
                "BOLT-INFO: ============== page %u ==============\n", CurPage);
          }
        }
      }
    }
  }
  BC.outs() << "BOLT-INFO: Function reordering stats\n"
            << format("BOLT-INFO:  Number of hot functions: %u\n"
                      "BOLT-INFO:  Number of clusters: %lu\n",
                      Hotfuncs, Clusters.size())
            << format("BOLT-INFO:  Final average call distance = %.1lf "
                      "(%.0lf / %.0lf)\n",
                      TotalCalls ? TotalDistance / TotalCalls : 0,
                      TotalDistance, TotalCalls)
            << format("BOLT-INFO:  Total Calls = %.0lf\n", TotalCalls);
  if (TotalCalls)
    BC.outs()
        << format("BOLT-INFO:  Total Calls within 64B = %.0lf (%.2lf%%)\n",
                  TotalCalls64B, 100 * TotalCalls64B / TotalCalls)
        << format("BOLT-INFO:  Total Calls within 4KB = %.0lf (%.2lf%%)\n",
                  TotalCalls4KB, 100 * TotalCalls4KB / TotalCalls)
        << format("BOLT-INFO:  Total Calls within 2MB = %.0lf (%.2lf%%)\n",
                  TotalCalls2MB, 100 * TotalCalls2MB / TotalCalls);
}

Error ReorderFunctions::readFunctionOrderFile(
    std::vector<std::string> &FunctionNames) {
  std::ifstream FuncsFile(opts::FunctionOrderFile, std::ios::in);
  if (!FuncsFile)
    return createFatalBOLTError(Twine("Ordered functions file \"") +
                                Twine(opts::FunctionOrderFile) +
                                Twine("\" can't be opened."));

  std::string FuncName;
  while (std::getline(FuncsFile, FuncName))
    FunctionNames.push_back(FuncName);
  return Error::success();
}

Error ReorderFunctions::runOnFunctions(BinaryContext &BC) {
  auto &BFs = BC.getBinaryFunctions();
  if (opts::ReorderFunctions != RT_NONE &&
      opts::ReorderFunctions != RT_EXEC_COUNT &&
      opts::ReorderFunctions != RT_USER) {
    Cg = buildCallGraph(
        BC,
        [](const BinaryFunction &BF) {
          if (!BF.hasProfile())
            return true;
          if (BF.getState() != BinaryFunction::State::CFG)
            return true;
          return false;
        },
        opts::CgFromPerfData,
        /*IncludeSplitCalls=*/false, opts::ReorderFunctionsUseHotSize,
        opts::CgUseSplitHotSize, opts::UseEdgeCounts,
        opts::CgIgnoreRecursiveCalls);
    Cg.normalizeArcWeights();
  }

  std::vector<Cluster> Clusters;

  switch (opts::ReorderFunctions) {
  case RT_NONE:
    break;
  case RT_EXEC_COUNT: {
    std::vector<BinaryFunction *> SortedFunctions(BFs.size());
    llvm::transform(llvm::make_second_range(BFs), SortedFunctions.begin(),
                    [](BinaryFunction &BF) { return &BF; });
    llvm::stable_sort(SortedFunctions,
                      [&](const BinaryFunction *A, const BinaryFunction *B) {
                        if (A->isIgnored())
                          return false;
                        if (B->isIgnored())
                          return true;
                        const size_t PadA = opts::padFunctionBefore(*A) +
                                            opts::padFunctionAfter(*A);
                        const size_t PadB = opts::padFunctionBefore(*B) +
                                            opts::padFunctionAfter(*B);
                        if (!PadA || !PadB) {
                          if (PadA)
                            return true;
                          if (PadB)
                            return false;
                        }
                        if (!A->hasProfile())
                          return false;
                        if (!B->hasProfile())
                          return true;
                        return A->getExecutionCount() > B->getExecutionCount();
                      });
    uint32_t Index = 0;
    for (BinaryFunction *BF : SortedFunctions)
      if (BF->hasProfile()) {
        BF->setIndex(Index++);
        LLVM_DEBUG(if (opts::Verbosity > 1) {
          dbgs() << "BOLT-INFO: hot func " << BF->getPrintName() << " ("
                 << BF->getExecutionCount() << ")\n";
        });
      }
  } break;
  case RT_HFSORT:
    Clusters = clusterize(Cg);
    break;
  case RT_CDSORT: {
    // It is required that the sum of incoming arc weights is not greater
    // than the number of samples for every function. Ensuring the call graph
    // obeys the property before running the algorithm.
    Cg.adjustArcWeights();

    // Initialize CFG nodes and their data
    std::vector<uint64_t> FuncSizes;
    std::vector<uint64_t> FuncCounts;
    std::vector<codelayout::EdgeCount> CallCounts;
    std::vector<uint64_t> CallOffsets;
    for (NodeId F = 0; F < Cg.numNodes(); ++F) {
      FuncSizes.push_back(Cg.size(F));
      FuncCounts.push_back(Cg.samples(F));
      for (NodeId Succ : Cg.successors(F)) {
        const Arc &Arc = *Cg.findArc(F, Succ);
        CallCounts.push_back({F, Succ, uint64_t(Arc.weight())});
        CallOffsets.push_back(uint64_t(Arc.avgCallOffset()));
      }
    }

    // Run the layout algorithm.
    std::vector<uint64_t> Result = codelayout::computeCacheDirectedLayout(
        FuncSizes, FuncCounts, CallCounts, CallOffsets);

    // Create a single cluster from the computed order of hot functions.
    std::vector<CallGraph::NodeId> NodeOrder(Result.begin(), Result.end());
    Clusters.emplace_back(Cluster(NodeOrder, Cg));
  } break;
  case RT_PETTIS_HANSEN:
    Clusters = pettisAndHansen(Cg);
    break;
  case RT_RANDOM:
    std::srand(opts::RandomSeed);
    Clusters = randomClusters(Cg);
    break;
  case RT_USER: {
    // Build LTOCommonNameMap
    StringMap<std::vector<uint64_t>> LTOCommonNameMap;
    for (const BinaryFunction &BF : llvm::make_second_range(BFs))
      for (StringRef Name : BF.getNames())
        if (std::optional<StringRef> LTOCommonName = getLTOCommonName(Name))
          LTOCommonNameMap[*LTOCommonName].push_back(BF.getAddress());

    uint32_t Index = 0;
    uint32_t InvalidEntries = 0;
    std::vector<std::string> FunctionNames;
    if (Error E = readFunctionOrderFile(FunctionNames))
      return Error(std::move(E));

    for (const std::string &Function : FunctionNames) {
      std::vector<uint64_t> FuncAddrs;

      BinaryData *BD = BC.getBinaryDataByName(Function);
      if (!BD) {
        // If we can't find the main symbol name, look for alternates.
        uint32_t LocalID = 1;
        while (true) {
          const std::string FuncName = Function + "/" + std::to_string(LocalID);
          BD = BC.getBinaryDataByName(FuncName);
          if (BD)
            FuncAddrs.push_back(BD->getAddress());
          else
            break;
          LocalID++;
        }
        // Strip LTO suffixes
        if (std::optional<StringRef> CommonName = getLTOCommonName(Function))
          if (LTOCommonNameMap.contains(*CommonName))
            llvm::append_range(FuncAddrs, LTOCommonNameMap[*CommonName]);
      } else {
        FuncAddrs.push_back(BD->getAddress());
      }

      if (FuncAddrs.empty()) {
        if (opts::Verbosity >= 1)
          BC.errs() << "BOLT-WARNING: Reorder functions: can't find function "
                    << "for " << Function << "\n";
        ++InvalidEntries;
        continue;
      }

      for (const uint64_t FuncAddr : FuncAddrs) {
        const BinaryData *FuncBD = BC.getBinaryDataAtAddress(FuncAddr);
        assert(FuncBD);

        BinaryFunction *BF = BC.getFunctionForSymbol(FuncBD->getSymbol());
        if (!BF) {
          if (opts::Verbosity >= 1)
            BC.errs() << "BOLT-WARNING: Reorder functions: can't find function "
                      << "for " << Function << "\n";
          ++InvalidEntries;
          break;
        }
        if (!BF->hasValidIndex())
          BF->setIndex(Index++);
        else if (opts::Verbosity > 0)
          BC.errs() << "BOLT-WARNING: Duplicate reorder entry for " << Function
                    << "\n";
      }
    }
    if (InvalidEntries)
      BC.errs() << "BOLT-WARNING: Reorder functions: can't find functions for "
                << InvalidEntries << " entries in -function-order list\n";
  } break;

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

  reorder(BC, std::move(Clusters), BFs);

  BC.HasFinalizedFunctionOrder = true;

  std::unique_ptr<std::ofstream> FuncsFile;
  if (!opts::GenerateFunctionOrderFile.empty()) {
    FuncsFile = std::make_unique<std::ofstream>(opts::GenerateFunctionOrderFile,
                                                std::ios::out);
    if (!FuncsFile) {
      BC.errs() << "BOLT-ERROR: ordered functions file "
                << opts::GenerateFunctionOrderFile << " cannot be opened\n";
      return createFatalBOLTError("");
    }
  }

  std::unique_ptr<std::ofstream> LinkSectionsFile;
  if (!opts::LinkSectionsFile.empty()) {
    LinkSectionsFile =
        std::make_unique<std::ofstream>(opts::LinkSectionsFile, std::ios::out);
    if (!LinkSectionsFile) {
      BC.errs() << "BOLT-ERROR: link sections file " << opts::LinkSectionsFile
                << " cannot be opened\n";
      return createFatalBOLTError("");
    }
  }

  if (FuncsFile || LinkSectionsFile) {
    std::vector<BinaryFunction *> SortedFunctions(BFs.size());
    llvm::transform(llvm::make_second_range(BFs), SortedFunctions.begin(),
                    [](BinaryFunction &BF) { return &BF; });

    // Sort functions by index.
    llvm::stable_sort(SortedFunctions, compareBinaryFunctionByIndex);

    for (const BinaryFunction *Func : SortedFunctions) {
      if (!Func->hasValidIndex())
        break;
      if (Func->isPLTFunction())
        continue;

      if (FuncsFile)
        *FuncsFile << Func->getOneName().str() << '\n';

      if (LinkSectionsFile) {
        const char *Indent = "";
        std::vector<StringRef> AllNames = Func->getNames();
        llvm::sort(AllNames);
        for (StringRef Name : AllNames) {
          const size_t SlashPos = Name.find('/');
          if (SlashPos != std::string::npos) {
            // Avoid duplicates for local functions.
            if (Name.find('/', SlashPos + 1) != std::string::npos)
              continue;
            Name = Name.substr(0, SlashPos);
          }
          *LinkSectionsFile << Indent << ".text." << Name.str() << '\n';
          Indent = " ";
        }
      }
    }

    if (FuncsFile) {
      FuncsFile->close();
      BC.outs() << "BOLT-INFO: dumped function order to "
                << opts::GenerateFunctionOrderFile << '\n';
    }

    if (LinkSectionsFile) {
      LinkSectionsFile->close();
      BC.outs() << "BOLT-INFO: dumped linker section order to "
                << opts::LinkSectionsFile << '\n';
    }
  }
  return Error::success();
}

} // namespace bolt
} // namespace llvm