llvm/lib/Transforms/Utils/SampleProfileLoaderBaseUtil.cpp

   1 //===- SampleProfileLoaderBaseUtil.cpp - Profile loader Util func ---------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // This file implements the SampleProfileLoader base utility functions.
  10 //
  11 //===----------------------------------------------------------------------===//
  12
  13 #include "llvm/Transforms/Utils/SampleProfileLoaderBaseUtil.h"
  14 #include "llvm/Analysis/ProfileSummaryInfo.h"
  15 #include "llvm/IR/Constants.h"
  16 #include "llvm/IR/Module.h"
  17 #include "llvm/Transforms/Utils/ModuleUtils.h"
  18
  19 namespace llvm {
  20
  21 cl::opt<unsigned> SampleProfileMaxPropagateIterations(
  22     "sample-profile-max-propagate-iterations", cl::init(100),
  23     cl::desc("Maximum number of iterations to go through when propagating "
  24              "sample block/edge weights through the CFG."));
  25
  26 cl::opt<unsigned> SampleProfileRecordCoverage(
  27     "sample-profile-check-record-coverage", cl::init(0), cl::value_desc("N"),
  28     cl::desc("Emit a warning if less than N% of records in the input profile "
  29              "are matched to the IR."));
  30
  31 cl::opt<unsigned> SampleProfileSampleCoverage(
  32     "sample-profile-check-sample-coverage", cl::init(0), cl::value_desc("N"),
  33     cl::desc("Emit a warning if less than N% of samples in the input profile "
  34              "are matched to the IR."));
  35
  36 cl::opt<bool> NoWarnSampleUnused(
  37     "no-warn-sample-unused", cl::init(false), cl::Hidden,
  38     cl::desc("Use this option to turn off/on warnings about function with "
  39              "samples but without debug information to use those samples. "));
  40
  41 cl::opt<bool> SampleProfileUseProfi(
  42     "sample-profile-use-profi", cl::Hidden,
  43     cl::desc("Use profi to infer block and edge counts."));
  44
  45 namespace sampleprofutil {
  46
  47 /// Return true if the given callsite is hot wrt to hot cutoff threshold.
  48 ///
  49 /// Functions that were inlined in the original binary will be represented
  50 /// in the inline stack in the sample profile. If the profile shows that
  51 /// the original inline decision was "good" (i.e., the callsite is executed
  52 /// frequently), then we will recreate the inline decision and apply the
  53 /// profile from the inlined callsite.
  54 ///
  55 /// To decide whether an inlined callsite is hot, we compare the callsite
  56 /// sample count with the hot cutoff computed by ProfileSummaryInfo, it is
  57 /// regarded as hot if the count is above the cutoff value.
  58 ///
  59 /// When ProfileAccurateForSymsInList is enabled and profile symbol list
  60 /// is present, functions in the profile symbol list but without profile will
  61 /// be regarded as cold and much less inlining will happen in CGSCC inlining
  62 /// pass, so we tend to lower the hot criteria here to allow more early
  63 /// inlining to happen for warm callsites and it is helpful for performance.
  64 bool callsiteIsHot(const FunctionSamples *CallsiteFS, ProfileSummaryInfo *PSI,
  65                    bool ProfAccForSymsInList) {
  66   if (!CallsiteFS)
  67     return false; // The callsite was not inlined in the original binary.
  68
  69   assert(PSI && "PSI is expected to be non null");
  70   uint64_t CallsiteTotalSamples = CallsiteFS->getTotalSamples();
  71   if (ProfAccForSymsInList)
  72     return !PSI->isColdCount(CallsiteTotalSamples);
  73   else
  74     return PSI->isHotCount(CallsiteTotalSamples);
  75 }
  76
  77 /// Mark as used the sample record for the given function samples at
  78 /// (LineOffset, Discriminator).
  79 ///
  80 /// \returns true if this is the first time we mark the given record.
  81 bool SampleCoverageTracker::markSamplesUsed(const FunctionSamples *FS,
  82                                             uint32_t LineOffset,
  83                                             uint32_t Discriminator,
  84                                             uint64_t Samples) {
  85   LineLocation Loc(LineOffset, Discriminator);
  86   unsigned &Count = SampleCoverage[FS][Loc];
  87   bool FirstTime = (++Count == 1);
  88   if (FirstTime)
  89     TotalUsedSamples += Samples;
  90   return FirstTime;
  91 }
  92
  93 /// Return the number of sample records that were applied from this profile.
  94 ///
  95 /// This count does not include records from cold inlined callsites.
  96 unsigned
  97 SampleCoverageTracker::countUsedRecords(const FunctionSamples *FS,
  98                                         ProfileSummaryInfo *PSI) const {
  99   auto I = SampleCoverage.find(FS);
 100
 101   // The size of the coverage map for FS represents the number of records
 102   // that were marked used at least once.
 103   unsigned Count = (I != SampleCoverage.end()) ? I->second.size() : 0;
 104
 105   // If there are inlined callsites in this function, count the samples found
 106   // in the respective bodies. However, do not bother counting callees with 0
 107   // total samples, these are callees that were never invoked at runtime.
 108   for (const auto &I : FS->getCallsiteSamples())
 109     for (const auto &J : I.second) {
 110       const FunctionSamples *CalleeSamples = &J.second;
 111       if (callsiteIsHot(CalleeSamples, PSI, ProfAccForSymsInList))
 112         Count += countUsedRecords(CalleeSamples, PSI);
 113     }
 114
 115   return Count;
 116 }
 117
 118 /// Return the number of sample records in the body of this profile.
 119 ///
 120 /// This count does not include records from cold inlined callsites.
 121 unsigned
 122 SampleCoverageTracker::countBodyRecords(const FunctionSamples *FS,
 123                                         ProfileSummaryInfo *PSI) const {
 124   unsigned Count = FS->getBodySamples().size();
 125
 126   // Only count records in hot callsites.
 127   for (const auto &I : FS->getCallsiteSamples())
 128     for (const auto &J : I.second) {
 129       const FunctionSamples *CalleeSamples = &J.second;
 130       if (callsiteIsHot(CalleeSamples, PSI, ProfAccForSymsInList))
 131         Count += countBodyRecords(CalleeSamples, PSI);
 132     }
 133
 134   return Count;
 135 }
 136
 137 /// Return the number of samples collected in the body of this profile.
 138 ///
 139 /// This count does not include samples from cold inlined callsites.
 140 uint64_t
 141 SampleCoverageTracker::countBodySamples(const FunctionSamples *FS,
 142                                         ProfileSummaryInfo *PSI) const {
 143   uint64_t Total = 0;
 144   for (const auto &I : FS->getBodySamples())
 145     Total += I.second.getSamples();
 146
 147   // Only count samples in hot callsites.
 148   for (const auto &I : FS->getCallsiteSamples())
 149     for (const auto &J : I.second) {
 150       const FunctionSamples *CalleeSamples = &J.second;
 151       if (callsiteIsHot(CalleeSamples, PSI, ProfAccForSymsInList))
 152         Total += countBodySamples(CalleeSamples, PSI);
 153     }
 154
 155   return Total;
 156 }
 157
 158 /// Return the fraction of sample records used in this profile.
 159 ///
 160 /// The returned value is an unsigned integer in the range 0-100 indicating
 161 /// the percentage of sample records that were used while applying this
 162 /// profile to the associated function.
 163 unsigned SampleCoverageTracker::computeCoverage(unsigned Used,
 164                                                 unsigned Total) const {
 165   assert(Used <= Total &&
 166          "number of used records cannot exceed the total number of records");
 167   return Total > 0 ? Used * 100 / Total : 100;
 168 }
 169
 170 /// Create a global variable to flag FSDiscriminators are used.
 171 void createFSDiscriminatorVariable(Module *M) {
 172   const char *FSDiscriminatorVar = "__llvm_fs_discriminator__";
 173   if (M->getGlobalVariable(FSDiscriminatorVar))
 174     return;
 175
 176   auto &Context = M->getContext();
 177   // Place this variable to llvm.used so it won't be GC'ed.
 178   appendToUsed(*M, {new GlobalVariable(*M, Type::getInt1Ty(Context), true,
 179                                        GlobalValue::WeakODRLinkage,
 180                                        ConstantInt::getTrue(Context),
 181                                        FSDiscriminatorVar)});
 182 }
 183
 184 } // end of namespace sampleprofutil
 185 } // end of namespace llvm