llvm/lib/Analysis/ProfileSummaryInfo.cpp

//===- ProfileSummaryInfo.cpp - Global profile summary information --------===//
//
// 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 contains a pass that provides access to the global profile summary
// information.
//
//===----------------------------------------------------------------------===//

#include "llvm/Analysis/ProfileSummaryInfo.h"
#include "llvm/Analysis/BlockFrequencyInfo.h"
#include "llvm/IR/BasicBlock.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/ProfileSummary.h"
#include "llvm/InitializePasses.h"
#include "llvm/ProfileData/ProfileCommon.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Compiler.h"
#include <optional>
using namespace llvm;

namespace llvm {

static cl::opt<bool> PartialProfile(
    "partial-profile", cl::Hidden, cl::init(false),
    cl::desc("Specify the current profile is used as a partial profile."));

LLVM_ABI cl::opt<bool> ScalePartialSampleProfileWorkingSetSize(
    "scale-partial-sample-profile-working-set-size", cl::Hidden, cl::init(true),
    cl::desc(
        "If true, scale the working set size of the partial sample profile "
        "by the partial profile ratio to reflect the size of the program "
        "being compiled."));

static cl::opt<double> PartialSampleProfileWorkingSetSizeScaleFactor(
    "partial-sample-profile-working-set-size-scale-factor", cl::Hidden,
    cl::init(0.008),
    cl::desc("The scale factor used to scale the working set size of the "
             "partial sample profile along with the partial profile ratio. "
             "This includes the factor of the profile counter per block "
             "and the factor to scale the working set size to use the same "
             "shared thresholds as PGO."));

} // end namespace llvm

// The profile summary metadata may be attached either by the frontend or by
// any backend passes (IR level instrumentation, for example). This method
// checks if the Summary is null and if so checks if the summary metadata is now
// available in the module and parses it to get the Summary object.
void ProfileSummaryInfo::refresh(std::unique_ptr<ProfileSummary> &&Other) {
  if (Other) {
    Summary.swap(Other);
    return;
  }
  if (hasProfileSummary())
    return;
  // First try to get context sensitive ProfileSummary.
  auto *SummaryMD = M->getProfileSummary(/* IsCS */ true);
  if (SummaryMD)
    Summary.reset(ProfileSummary::getFromMD(SummaryMD));

  if (!hasProfileSummary()) {
    // This will actually return PSK_Instr or PSK_Sample summary.
    SummaryMD = M->getProfileSummary(/* IsCS */ false);
    if (SummaryMD)
      Summary.reset(ProfileSummary::getFromMD(SummaryMD));
  }
  if (!hasProfileSummary())
    return;
  computeThresholds();
}

std::optional<uint64_t>
ProfileSummaryInfo::getProfileCount(const CallBase &Call,
                                    BlockFrequencyInfo *BFI) const {
  assert((isa<CallInst>(Call) || isa<InvokeInst>(Call)) &&
         "We can only get profile count for call/invoke instruction.");
  if (hasSampleProfile()) {
    // In sample PGO mode, check if there is a profile metadata on the
    // instruction. If it is present, determine hotness solely based on that,
    // since the sampled entry count may not be accurate. If there is no
    // annotated on the instruction, return std::nullopt.
    uint64_t TotalCount;
    if (Call.extractProfTotalWeight(TotalCount))
      return TotalCount;
    return std::nullopt;
  }
  if (BFI)
    return BFI->getBlockProfileCount(Call.getParent());
  return std::nullopt;
}

bool ProfileSummaryInfo::isFunctionHotnessUnknown(const Function &F) const {
  assert(hasPartialSampleProfile() && "Expect partial sample profile");
  return !F.getEntryCount();
}

/// Returns true if the function's entry is a cold. If it returns false, it
/// either means it is not cold or it is unknown whether it is cold or not (for
/// example, no profile data is available).
bool ProfileSummaryInfo::isFunctionEntryCold(const Function *F) const {
  if (!F)
    return false;
  if (F->hasFnAttribute(Attribute::Cold))
    return true;
  if (!hasProfileSummary())
    return false;
  auto FunctionCount = F->getEntryCount();
  // FIXME: The heuristic used below for determining coldness is based on
  // preliminary SPEC tuning for inliner. This will eventually be a
  // convenience method that calls isHotCount.
  return FunctionCount && isColdCount(*FunctionCount);
}

/// Compute the hot and cold thresholds.
void ProfileSummaryInfo::computeThresholds() {
  auto &DetailedSummary = Summary->getDetailedSummary();
  auto &HotEntry = ProfileSummaryBuilder::getEntryForPercentile(
      DetailedSummary, ProfileSummaryCutoffHot);
  HotCountThreshold =
      ProfileSummaryBuilder::getHotCountThreshold(DetailedSummary);
  ColdCountThreshold =
      ProfileSummaryBuilder::getColdCountThreshold(DetailedSummary);
  // When the hot and cold thresholds are identical, we would classify
  // a count value as both hot and cold since we are doing an inclusive check
  // (see ::is{Hot|Cold}Count(). To avoid this undesirable overlap, ensure the
  // thresholds are distinct.
  if (HotCountThreshold == ColdCountThreshold) {
    if (ColdCountThreshold > 0)
      (*ColdCountThreshold)--;
    else
      (*HotCountThreshold)++;
  }
  assert(ColdCountThreshold < HotCountThreshold &&
         "Cold count threshold should be less than hot count threshold!");
  if (!hasPartialSampleProfile() || !ScalePartialSampleProfileWorkingSetSize) {
    HasHugeWorkingSetSize =
        HotEntry.NumCounts > ProfileSummaryHugeWorkingSetSizeThreshold;
    HasLargeWorkingSetSize =
        HotEntry.NumCounts > ProfileSummaryLargeWorkingSetSizeThreshold;
  } else {
    // Scale the working set size of the partial sample profile to reflect the
    // size of the program being compiled.
    double PartialProfileRatio = Summary->getPartialProfileRatio();
    uint64_t ScaledHotEntryNumCounts =
        static_cast<uint64_t>(HotEntry.NumCounts * PartialProfileRatio *
                              PartialSampleProfileWorkingSetSizeScaleFactor);
    HasHugeWorkingSetSize =
        ScaledHotEntryNumCounts > ProfileSummaryHugeWorkingSetSizeThreshold;
    HasLargeWorkingSetSize =
        ScaledHotEntryNumCounts > ProfileSummaryLargeWorkingSetSizeThreshold;
  }
}

std::optional<uint64_t>
ProfileSummaryInfo::computeThreshold(int PercentileCutoff) const {
  if (!hasProfileSummary())
    return std::nullopt;
  auto [Iter, Inserted] = ThresholdCache.try_emplace(PercentileCutoff);
  if (!Inserted)
    return Iter->second;
  auto &DetailedSummary = Summary->getDetailedSummary();
  auto &Entry = ProfileSummaryBuilder::getEntryForPercentile(DetailedSummary,
                                                             PercentileCutoff);
  uint64_t CountThreshold = Entry.MinCount;
  Iter->second = CountThreshold;
  return CountThreshold;
}

bool ProfileSummaryInfo::hasHugeWorkingSetSize() const {
  return HasHugeWorkingSetSize && *HasHugeWorkingSetSize;
}

bool ProfileSummaryInfo::hasLargeWorkingSetSize() const {
  return HasLargeWorkingSetSize && *HasLargeWorkingSetSize;
}

bool ProfileSummaryInfo::isHotCount(uint64_t C) const {
  return HotCountThreshold && C >= *HotCountThreshold;
}

bool ProfileSummaryInfo::isColdCount(uint64_t C) const {
  return ColdCountThreshold && C <= *ColdCountThreshold;
}

template <bool isHot>
bool ProfileSummaryInfo::isHotOrColdCountNthPercentile(int PercentileCutoff,
                                                       uint64_t C) const {
  auto CountThreshold = computeThreshold(PercentileCutoff);
  if (isHot)
    return CountThreshold && C >= *CountThreshold;
  else
    return CountThreshold && C <= *CountThreshold;
}

bool ProfileSummaryInfo::isHotCountNthPercentile(int PercentileCutoff,
                                                 uint64_t C) const {
  return isHotOrColdCountNthPercentile<true>(PercentileCutoff, C);
}

bool ProfileSummaryInfo::isColdCountNthPercentile(int PercentileCutoff,
                                                  uint64_t C) const {
  return isHotOrColdCountNthPercentile<false>(PercentileCutoff, C);
}

uint64_t ProfileSummaryInfo::getOrCompHotCountThreshold() const {
  return HotCountThreshold.value_or(UINT64_MAX);
}

uint64_t ProfileSummaryInfo::getOrCompColdCountThreshold() const {
  return ColdCountThreshold.value_or(0);
}

bool ProfileSummaryInfo::isHotCallSite(const CallBase &CB,
                                       BlockFrequencyInfo *BFI) const {
  auto C = getProfileCount(CB, BFI);
  return C && isHotCount(*C);
}

bool ProfileSummaryInfo::isColdCallSite(const CallBase &CB,
                                        BlockFrequencyInfo *BFI) const {
  auto C = getProfileCount(CB, BFI);
  if (C)
    return isColdCount(*C);

  // In SamplePGO, if the caller has been sampled, and there is no profile
  // annotated on the callsite, we consider the callsite as cold.
  return hasSampleProfile() && CB.getCaller()->hasProfileData();
}

bool ProfileSummaryInfo::hasPartialSampleProfile() const {
  return hasProfileSummary() &&
         Summary->getKind() == ProfileSummary::PSK_Sample &&
         (PartialProfile || Summary->isPartialProfile());
}

INITIALIZE_PASS(ProfileSummaryInfoWrapperPass, "profile-summary-info",
                "Profile summary info", false, true)

ProfileSummaryInfoWrapperPass::ProfileSummaryInfoWrapperPass()
    : ImmutablePass(ID) {}

bool ProfileSummaryInfoWrapperPass::doInitialization(Module &M) {
  PSI.reset(new ProfileSummaryInfo(M));
  return false;
}

bool ProfileSummaryInfoWrapperPass::doFinalization(Module &M) {
  PSI.reset();
  return false;
}

AnalysisKey ProfileSummaryAnalysis::Key;
ProfileSummaryInfo ProfileSummaryAnalysis::run(Module &M,
                                               ModuleAnalysisManager &) {
  return ProfileSummaryInfo(M);
}

PreservedAnalyses ProfileSummaryPrinterPass::run(Module &M,
                                                 ModuleAnalysisManager &AM) {
  ProfileSummaryInfo &PSI = AM.getResult<ProfileSummaryAnalysis>(M);

  OS << "Functions in " << M.getName() << " with hot/cold annotations: \n";
  for (auto &F : M) {
    OS << F.getName();
    if (PSI.isFunctionEntryHot(&F))
      OS << " :hot entry ";
    else if (PSI.isFunctionEntryCold(&F))
      OS << " :cold entry ";
    OS << "\n";
  }
  return PreservedAnalyses::all();
}

char ProfileSummaryInfoWrapperPass::ID = 0;