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 186