lib/Analysis/ProfileSummaryInfo.cpp

   1 //===- ProfileSummaryInfo.cpp - Global profile summary information --------===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file is distributed under the University of Illinois Open Source
   6 // License. See LICENSE.TXT for details.
   7 //
   8 //===----------------------------------------------------------------------===//
   9 //
  10 // This file contains a pass that provides access to the global profile summary
  11 // information.
  12 //
  13 //===----------------------------------------------------------------------===//
  14
  15 #include "llvm/Analysis/ProfileSummaryInfo.h"
  16 #include "llvm/Analysis/BlockFrequencyInfo.h"
  17 #include "llvm/IR/BasicBlock.h"
  18 #include "llvm/IR/CallSite.h"
  19 #include "llvm/IR/Metadata.h"
  20 #include "llvm/IR/Module.h"
  21 #include "llvm/IR/ProfileSummary.h"
  22 using namespace llvm;
  23
  24 // The following two parameters determine the threshold for a count to be
  25 // considered hot/cold. These two parameters are percentile values (multiplied
  26 // by 10000). If the counts are sorted in descending order, the minimum count to
  27 // reach ProfileSummaryCutoffHot gives the threshold to determine a hot count.
  28 // Similarly, the minimum count to reach ProfileSummaryCutoffCold gives the
  29 // threshold for determining cold count (everything <= this threshold is
  30 // considered cold).
  31
  32 static cl::opt<int> ProfileSummaryCutoffHot(
  33     "profile-summary-cutoff-hot", cl::Hidden, cl::init(990000), cl::ZeroOrMore,
  34     cl::desc("A count is hot if it exceeds the minimum count to"
  35              " reach this percentile of total counts."));
  36
  37 static cl::opt<int> ProfileSummaryCutoffCold(
  38     "profile-summary-cutoff-cold", cl::Hidden, cl::init(999999), cl::ZeroOrMore,
  39     cl::desc("A count is cold if it is below the minimum count"
  40              " to reach this percentile of total counts."));
  41
  42 static cl::opt<bool> ProfileSampleAccurate(
  43     "profile-sample-accurate", cl::Hidden, cl::init(false),
  44     cl::desc("If the sample profile is accurate, we will mark all un-sampled "
  45              "callsite as cold. Otherwise, treat un-sampled callsites as if "
  46              "we have no profile."));
  47 static cl::opt<unsigned> ProfileSummaryHugeWorkingSetSizeThreshold(
  48     "profile-summary-huge-working-set-size-threshold", cl::Hidden,
  49     cl::init(15000), cl::ZeroOrMore,
  50     cl::desc("The code working set size is considered huge if the number of"
  51              " blocks required to reach the -profile-summary-cutoff-hot"
  52              " percentile exceeds this count."));
  53
  54 // Find the summary entry for a desired percentile of counts.
  55 static const ProfileSummaryEntry &getEntryForPercentile(SummaryEntryVector &DS,
  56                                                         uint64_t Percentile) {
  57   auto Compare = [](const ProfileSummaryEntry &Entry, uint64_t Percentile) {
  58     return Entry.Cutoff < Percentile;
  59   };
  60   auto It = std::lower_bound(DS.begin(), DS.end(), Percentile, Compare);
  61   // The required percentile has to be <= one of the percentiles in the
  62   // detailed summary.
  63   if (It == DS.end())
  64     report_fatal_error("Desired percentile exceeds the maximum cutoff");
  65   return *It;
  66 }
  67
  68 // The profile summary metadata may be attached either by the frontend or by
  69 // any backend passes (IR level instrumentation, for example). This method
  70 // checks if the Summary is null and if so checks if the summary metadata is now
  71 // available in the module and parses it to get the Summary object. Returns true
  72 // if a valid Summary is available.
  73 bool ProfileSummaryInfo::computeSummary() {
  74   if (Summary)
  75     return true;
  76   auto *SummaryMD = M.getProfileSummary();
  77   if (!SummaryMD)
  78     return false;
  79   Summary.reset(ProfileSummary::getFromMD(SummaryMD));
  80   return true;
  81 }
  82
  83 Optional<uint64_t>
  84 ProfileSummaryInfo::getProfileCount(const Instruction *Inst,
  85                                     BlockFrequencyInfo *BFI) {
  86   if (!Inst)
  87     return None;
  88   assert((isa<CallInst>(Inst) || isa<InvokeInst>(Inst)) &&
  89          "We can only get profile count for call/invoke instruction.");
  90   if (hasSampleProfile()) {
  91     // In sample PGO mode, check if there is a profile metadata on the
  92     // instruction. If it is present, determine hotness solely based on that,
  93     // since the sampled entry count may not be accurate. If there is no
  94     // annotated on the instruction, return None.
  95     uint64_t TotalCount;
  96     if (Inst->extractProfTotalWeight(TotalCount))
  97       return TotalCount;
  98     return None;
  99   }
 100   if (BFI)
 101     return BFI->getBlockProfileCount(Inst->getParent());
 102   return None;
 103 }
 104
 105 /// Returns true if the function's entry is hot. If it returns false, it
 106 /// either means it is not hot or it is unknown whether it is hot or not (for
 107 /// example, no profile data is available).
 108 bool ProfileSummaryInfo::isFunctionEntryHot(const Function *F) {
 109   if (!F || !computeSummary())
 110     return false;
 111   auto FunctionCount = F->getEntryCount();
 112   // FIXME: The heuristic used below for determining hotness is based on
 113   // preliminary SPEC tuning for inliner. This will eventually be a
 114   // convenience method that calls isHotCount.
 115   return FunctionCount && isHotCount(FunctionCount.getValue());
 116 }
 117
 118 /// Returns true if the function's entry or total call edge count is hot.
 119 /// If it returns false, it either means it is not hot or it is unknown
 120 /// whether it is hot or not (for example, no profile data is available).
 121 bool ProfileSummaryInfo::isFunctionHotInCallGraph(const Function *F) {
 122   if (!F || !computeSummary())
 123     return false;
 124   if (auto FunctionCount = F->getEntryCount())
 125     if (isHotCount(FunctionCount.getValue()))
 126       return true;
 127
 128   uint64_t TotalCallCount = 0;
 129   for (const auto &BB : *F)
 130     for (const auto &I : BB)
 131       if (isa<CallInst>(I) || isa<InvokeInst>(I))
 132         if (auto CallCount = getProfileCount(&I, nullptr))
 133           TotalCallCount += CallCount.getValue();
 134   return isHotCount(TotalCallCount);
 135 }
 136
 137 /// Returns true if the function's entry and total call edge count is cold.
 138 /// If it returns false, it either means it is not cold or it is unknown
 139 /// whether it is cold or not (for example, no profile data is available).
 140 bool ProfileSummaryInfo::isFunctionColdInCallGraph(const Function *F) {
 141   if (!F || !computeSummary())
 142     return false;
 143   if (auto FunctionCount = F->getEntryCount())
 144     if (!isColdCount(FunctionCount.getValue()))
 145       return false;
 146
 147   uint64_t TotalCallCount = 0;
 148   for (const auto &BB : *F)
 149     for (const auto &I : BB)
 150       if (isa<CallInst>(I) || isa<InvokeInst>(I))
 151         if (auto CallCount = getProfileCount(&I, nullptr))
 152           TotalCallCount += CallCount.getValue();
 153   return isColdCount(TotalCallCount);
 154 }
 155
 156 /// Returns true if the function's entry is a cold. If it returns false, it
 157 /// either means it is not cold or it is unknown whether it is cold or not (for
 158 /// example, no profile data is available).
 159 bool ProfileSummaryInfo::isFunctionEntryCold(const Function *F) {
 160   if (!F)
 161     return false;
 162   if (F->hasFnAttribute(Attribute::Cold))
 163     return true;
 164   if (!computeSummary())
 165     return false;
 166   auto FunctionCount = F->getEntryCount();
 167   // FIXME: The heuristic used below for determining coldness is based on
 168   // preliminary SPEC tuning for inliner. This will eventually be a
 169   // convenience method that calls isHotCount.
 170   return FunctionCount && isColdCount(FunctionCount.getValue());
 171 }
 172
 173 /// Compute the hot and cold thresholds.
 174 void ProfileSummaryInfo::computeThresholds() {
 175   if (!computeSummary())
 176     return;
 177   auto &DetailedSummary = Summary->getDetailedSummary();
 178   auto &HotEntry =
 179       getEntryForPercentile(DetailedSummary, ProfileSummaryCutoffHot);
 180   HotCountThreshold = HotEntry.MinCount;
 181   auto &ColdEntry =
 182       getEntryForPercentile(DetailedSummary, ProfileSummaryCutoffCold);
 183   ColdCountThreshold = ColdEntry.MinCount;
 184   HasHugeWorkingSetSize =
 185       HotEntry.NumCounts > ProfileSummaryHugeWorkingSetSizeThreshold;
 186 }
 187
 188 bool ProfileSummaryInfo::hasHugeWorkingSetSize() {
 189   if (!HasHugeWorkingSetSize)
 190     computeThresholds();
 191   return HasHugeWorkingSetSize && HasHugeWorkingSetSize.getValue();
 192 }
 193
 194 bool ProfileSummaryInfo::isHotCount(uint64_t C) {
 195   if (!HotCountThreshold)
 196     computeThresholds();
 197   return HotCountThreshold && C >= HotCountThreshold.getValue();
 198 }
 199
 200 bool ProfileSummaryInfo::isColdCount(uint64_t C) {
 201   if (!ColdCountThreshold)
 202     computeThresholds();
 203   return ColdCountThreshold && C <= ColdCountThreshold.getValue();
 204 }
 205
 206 bool ProfileSummaryInfo::isHotBB(const BasicBlock *B, BlockFrequencyInfo *BFI) {
 207   auto Count = BFI->getBlockProfileCount(B);
 208   return Count && isHotCount(*Count);
 209 }
 210
 211 bool ProfileSummaryInfo::isColdBB(const BasicBlock *B,
 212                                   BlockFrequencyInfo *BFI) {
 213   auto Count = BFI->getBlockProfileCount(B);
 214   return Count && isColdCount(*Count);
 215 }
 216
 217 bool ProfileSummaryInfo::isHotCallSite(const CallSite &CS,
 218                                        BlockFrequencyInfo *BFI) {
 219   auto C = getProfileCount(CS.getInstruction(), BFI);
 220   return C && isHotCount(*C);
 221 }
 222
 223 bool ProfileSummaryInfo::isColdCallSite(const CallSite &CS,
 224                                         BlockFrequencyInfo *BFI) {
 225   auto C = getProfileCount(CS.getInstruction(), BFI);
 226   if (C)
 227     return isColdCount(*C);
 228
 229   // In SamplePGO, if the caller has been sampled, and there is no profile
 230   // annotatedon the callsite, we consider the callsite as cold.
 231   // If there is no profile for the caller, and we know the profile is
 232   // accurate, we consider the callsite as cold.
 233   return (hasSampleProfile() &&
 234           (CS.getCaller()->getEntryCount() || ProfileSampleAccurate ||
 235            CS.getCaller()->hasFnAttribute("profile-sample-accurate")));
 236 }
 237
 238 INITIALIZE_PASS(ProfileSummaryInfoWrapperPass, "profile-summary-info",
 239                 "Profile summary info", false, true)
 240
 241 ProfileSummaryInfoWrapperPass::ProfileSummaryInfoWrapperPass()
 242     : ImmutablePass(ID) {
 243   initializeProfileSummaryInfoWrapperPassPass(*PassRegistry::getPassRegistry());
 244 }
 245
 246 bool ProfileSummaryInfoWrapperPass::doInitialization(Module &M) {
 247   PSI.reset(new ProfileSummaryInfo(M));
 248   return false;
 249 }
 250
 251 bool ProfileSummaryInfoWrapperPass::doFinalization(Module &M) {
 252   PSI.reset();
 253   return false;
 254 }
 255
 256 AnalysisKey ProfileSummaryAnalysis::Key;
 257 ProfileSummaryInfo ProfileSummaryAnalysis::run(Module &M,
 258                                                ModuleAnalysisManager &) {
 259   return ProfileSummaryInfo(M);
 260 }
 261
 262 PreservedAnalyses ProfileSummaryPrinterPass::run(Module &M,
 263                                                  ModuleAnalysisManager &AM) {
 264   ProfileSummaryInfo &PSI = AM.getResult<ProfileSummaryAnalysis>(M);
 265
 266   OS << "Functions in " << M.getName() << " with hot/cold annotations: \n";
 267   for (auto &F : M) {
 268     OS << F.getName();
 269     if (PSI.isFunctionEntryHot(&F))
 270       OS << " :hot entry ";
 271     else if (PSI.isFunctionEntryCold(&F))
 272       OS << " :cold entry ";
 273     OS << "\n";
 274   }
 275   return PreservedAnalyses::all();
 276 }
 277
 278 char ProfileSummaryInfoWrapperPass::ID = 0;