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