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.getCount());
 116 }
 117
 118 /// Returns true if the function contains hot code. This can include a hot
 119 /// function entry count, hot basic block, or (in the case of Sample PGO)
 120 /// hot total call edge count.
 121 /// If it returns false, it either means it is not hot or it is unknown
 122 /// (for example, no profile data is available).
 123 bool ProfileSummaryInfo::isFunctionHotInCallGraph(const Function *F,
 124                                                   BlockFrequencyInfo &BFI) {
 125   if (!F || !computeSummary())
 126     return false;
 127   if (auto FunctionCount = F->getEntryCount())
 128     if (isHotCount(FunctionCount.getCount()))
 129       return true;
 130
 131   if (hasSampleProfile()) {
 132     uint64_t TotalCallCount = 0;
 133     for (const auto &BB : *F)
 134       for (const auto &I : BB)
 135         if (isa<CallInst>(I) || isa<InvokeInst>(I))
 136           if (auto CallCount = getProfileCount(&I, nullptr))
 137             TotalCallCount += CallCount.getValue();
 138     if (isHotCount(TotalCallCount))
 139       return true;
 140   }
 141   for (const auto &BB : *F)
 142     if (isHotBB(&BB, &BFI))
 143       return true;
 144   return false;
 145 }
 146
 147 /// Returns true if the function only contains cold code. This means that
 148 /// the function entry and blocks are all cold, and (in the case of Sample PGO)
 149 /// the total call edge count is cold.
 150 /// If it returns false, it either means it is not cold or it is unknown
 151 /// (for example, no profile data is available).
 152 bool ProfileSummaryInfo::isFunctionColdInCallGraph(const Function *F,
 153                                                    BlockFrequencyInfo &BFI) {
 154   if (!F || !computeSummary())
 155     return false;
 156   if (auto FunctionCount = F->getEntryCount())
 157     if (!isColdCount(FunctionCount.getCount()))
 158       return false;
 159
 160   if (hasSampleProfile()) {
 161     uint64_t TotalCallCount = 0;
 162     for (const auto &BB : *F)
 163       for (const auto &I : BB)
 164         if (isa<CallInst>(I) || isa<InvokeInst>(I))
 165           if (auto CallCount = getProfileCount(&I, nullptr))
 166             TotalCallCount += CallCount.getValue();
 167     if (!isColdCount(TotalCallCount))
 168       return false;
 169   }
 170   for (const auto &BB : *F)
 171     if (!isColdBB(&BB, &BFI))
 172       return false;
 173   return true;
 174 }
 175
 176 /// Returns true if the function's entry is a cold. If it returns false, it
 177 /// either means it is not cold or it is unknown whether it is cold or not (for
 178 /// example, no profile data is available).
 179 bool ProfileSummaryInfo::isFunctionEntryCold(const Function *F) {
 180   if (!F)
 181     return false;
 182   if (F->hasFnAttribute(Attribute::Cold))
 183     return true;
 184   if (!computeSummary())
 185     return false;
 186   auto FunctionCount = F->getEntryCount();
 187   // FIXME: The heuristic used below for determining coldness is based on
 188   // preliminary SPEC tuning for inliner. This will eventually be a
 189   // convenience method that calls isHotCount.
 190   return FunctionCount && isColdCount(FunctionCount.getCount());
 191 }
 192
 193 /// Compute the hot and cold thresholds.
 194 void ProfileSummaryInfo::computeThresholds() {
 195   if (!computeSummary())
 196     return;
 197   auto &DetailedSummary = Summary->getDetailedSummary();
 198   auto &HotEntry =
 199       getEntryForPercentile(DetailedSummary, ProfileSummaryCutoffHot);
 200   HotCountThreshold = HotEntry.MinCount;
 201   auto &ColdEntry =
 202       getEntryForPercentile(DetailedSummary, ProfileSummaryCutoffCold);
 203   ColdCountThreshold = ColdEntry.MinCount;
 204   HasHugeWorkingSetSize =
 205       HotEntry.NumCounts > ProfileSummaryHugeWorkingSetSizeThreshold;
 206 }
 207
 208 bool ProfileSummaryInfo::hasHugeWorkingSetSize() {
 209   if (!HasHugeWorkingSetSize)
 210     computeThresholds();
 211   return HasHugeWorkingSetSize && HasHugeWorkingSetSize.getValue();
 212 }
 213
 214 bool ProfileSummaryInfo::isHotCount(uint64_t C) {
 215   if (!HotCountThreshold)
 216     computeThresholds();
 217   return HotCountThreshold && C >= HotCountThreshold.getValue();
 218 }
 219
 220 bool ProfileSummaryInfo::isColdCount(uint64_t C) {
 221   if (!ColdCountThreshold)
 222     computeThresholds();
 223   return ColdCountThreshold && C <= ColdCountThreshold.getValue();
 224 }
 225
 226 uint64_t ProfileSummaryInfo::getOrCompHotCountThreshold() {
 227   if (!HotCountThreshold)
 228     computeThresholds();
 229   return HotCountThreshold ? HotCountThreshold.getValue() : UINT64_MAX;
 230 }
 231
 232 uint64_t ProfileSummaryInfo::getOrCompColdCountThreshold() {
 233   if (!ColdCountThreshold)
 234     computeThresholds();
 235   return ColdCountThreshold ? ColdCountThreshold.getValue() : 0;
 236 }
 237
 238 bool ProfileSummaryInfo::isHotBB(const BasicBlock *B, BlockFrequencyInfo *BFI) {
 239   auto Count = BFI->getBlockProfileCount(B);
 240   return Count && isHotCount(*Count);
 241 }
 242
 243 bool ProfileSummaryInfo::isColdBB(const BasicBlock *B,
 244                                   BlockFrequencyInfo *BFI) {
 245   auto Count = BFI->getBlockProfileCount(B);
 246   return Count && isColdCount(*Count);
 247 }
 248
 249 bool ProfileSummaryInfo::isHotCallSite(const CallSite &CS,
 250                                        BlockFrequencyInfo *BFI) {
 251   auto C = getProfileCount(CS.getInstruction(), BFI);
 252   return C && isHotCount(*C);
 253 }
 254
 255 bool ProfileSummaryInfo::isColdCallSite(const CallSite &CS,
 256                                         BlockFrequencyInfo *BFI) {
 257   auto C = getProfileCount(CS.getInstruction(), BFI);
 258   if (C)
 259     return isColdCount(*C);
 260
 261   // In SamplePGO, if the caller has been sampled, and there is no profile
 262   // annotated on the callsite, we consider the callsite as cold.
 263   // If there is no profile for the caller, and we know the profile is
 264   // accurate, we consider the callsite as cold.
 265   return (hasSampleProfile() &&
 266           (CS.getCaller()->hasProfileData() || ProfileSampleAccurate ||
 267            CS.getCaller()->hasFnAttribute("profile-sample-accurate")));
 268 }
 269
 270 INITIALIZE_PASS(ProfileSummaryInfoWrapperPass, "profile-summary-info",
 271                 "Profile summary info", false, true)
 272
 273 ProfileSummaryInfoWrapperPass::ProfileSummaryInfoWrapperPass()
 274     : ImmutablePass(ID) {
 275   initializeProfileSummaryInfoWrapperPassPass(*PassRegistry::getPassRegistry());
 276 }
 277
 278 bool ProfileSummaryInfoWrapperPass::doInitialization(Module &M) {
 279   PSI.reset(new ProfileSummaryInfo(M));
 280   return false;
 281 }
 282
 283 bool ProfileSummaryInfoWrapperPass::doFinalization(Module &M) {
 284   PSI.reset();
 285   return false;
 286 }
 287
 288 AnalysisKey ProfileSummaryAnalysis::Key;
 289 ProfileSummaryInfo ProfileSummaryAnalysis::run(Module &M,
 290                                                ModuleAnalysisManager &) {
 291   return ProfileSummaryInfo(M);
 292 }
 293
 294 PreservedAnalyses ProfileSummaryPrinterPass::run(Module &M,
 295                                                  ModuleAnalysisManager &AM) {
 296   ProfileSummaryInfo &PSI = AM.getResult<ProfileSummaryAnalysis>(M);
 297
 298   OS << "Functions in " << M.getName() << " with hot/cold annotations: \n";
 299   for (auto &F : M) {
 300     OS << F.getName();
 301     if (PSI.isFunctionEntryHot(&F))
 302       OS << " :hot entry ";
 303     else if (PSI.isFunctionEntryCold(&F))
 304       OS << " :cold entry ";
 305     OS << "\n";
 306   }
 307   return PreservedAnalyses::all();
 308 }
 309
 310 char ProfileSummaryInfoWrapperPass::ID = 0;