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Diffstat (limited to 'llvm/lib/Transforms/IPO/SampleProfile.cpp')
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diff --git a/llvm/lib/Transforms/IPO/SampleProfile.cpp b/llvm/lib/Transforms/IPO/SampleProfile.cpp new file mode 100644 index 000000000000..6184681db8a2 --- /dev/null +++ b/llvm/lib/Transforms/IPO/SampleProfile.cpp @@ -0,0 +1,1855 @@ +//===- SampleProfile.cpp - Incorporate sample profiles into the IR --------===// +// +// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. +// See https://llvm.org/LICENSE.txt for license information. +// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception +// +//===----------------------------------------------------------------------===// +// +// This file implements the SampleProfileLoader transformation. This pass +// reads a profile file generated by a sampling profiler (e.g. Linux Perf - +// http://perf.wiki.kernel.org/) and generates IR metadata to reflect the +// profile information in the given profile. +// +// This pass generates branch weight annotations on the IR: +// +// - prof: Represents branch weights. This annotation is added to branches +// to indicate the weights of each edge coming out of the branch. +// The weight of each edge is the weight of the target block for +// that edge. The weight of a block B is computed as the maximum +// number of samples found in B. +// +//===----------------------------------------------------------------------===// + +#include "llvm/Transforms/IPO/SampleProfile.h" +#include "llvm/ADT/ArrayRef.h" +#include "llvm/ADT/DenseMap.h" +#include "llvm/ADT/DenseSet.h" +#include "llvm/ADT/None.h" +#include "llvm/ADT/SmallPtrSet.h" +#include "llvm/ADT/SmallSet.h" +#include "llvm/ADT/SmallVector.h" +#include "llvm/ADT/StringMap.h" +#include "llvm/ADT/StringRef.h" +#include "llvm/ADT/Twine.h" +#include "llvm/Analysis/AssumptionCache.h" +#include "llvm/Analysis/InlineCost.h" +#include "llvm/Analysis/LoopInfo.h" +#include "llvm/Analysis/OptimizationRemarkEmitter.h" +#include "llvm/Analysis/PostDominators.h" +#include "llvm/Analysis/ProfileSummaryInfo.h" +#include "llvm/Analysis/TargetTransformInfo.h" +#include "llvm/IR/BasicBlock.h" +#include "llvm/IR/CFG.h" +#include "llvm/IR/CallSite.h" +#include "llvm/IR/DebugInfoMetadata.h" +#include "llvm/IR/DebugLoc.h" +#include "llvm/IR/DiagnosticInfo.h" +#include "llvm/IR/Dominators.h" +#include "llvm/IR/Function.h" +#include "llvm/IR/GlobalValue.h" +#include "llvm/IR/InstrTypes.h" +#include "llvm/IR/Instruction.h" +#include "llvm/IR/Instructions.h" +#include "llvm/IR/IntrinsicInst.h" +#include "llvm/IR/LLVMContext.h" +#include "llvm/IR/MDBuilder.h" +#include "llvm/IR/Module.h" +#include "llvm/IR/PassManager.h" +#include "llvm/IR/ValueSymbolTable.h" +#include "llvm/Pass.h" +#include "llvm/ProfileData/InstrProf.h" +#include "llvm/ProfileData/SampleProf.h" +#include "llvm/ProfileData/SampleProfReader.h" +#include "llvm/Support/Casting.h" +#include "llvm/Support/CommandLine.h" +#include "llvm/Support/Debug.h" +#include "llvm/Support/ErrorHandling.h" +#include "llvm/Support/ErrorOr.h" +#include "llvm/Support/GenericDomTree.h" +#include "llvm/Support/raw_ostream.h" +#include "llvm/Transforms/IPO.h" +#include "llvm/Transforms/Instrumentation.h" +#include "llvm/Transforms/Utils/CallPromotionUtils.h" +#include "llvm/Transforms/Utils/Cloning.h" +#include "llvm/Transforms/Utils/MisExpect.h" +#include <algorithm> +#include <cassert> +#include <cstdint> +#include <functional> +#include <limits> +#include <map> +#include <memory> +#include <queue> +#include <string> +#include <system_error> +#include <utility> +#include <vector> + +using namespace llvm; +using namespace sampleprof; +using ProfileCount = Function::ProfileCount; +#define DEBUG_TYPE "sample-profile" + +// Command line option to specify the file to read samples from. This is +// mainly used for debugging. +static cl::opt<std::string> SampleProfileFile( + "sample-profile-file", cl::init(""), cl::value_desc("filename"), + cl::desc("Profile file loaded by -sample-profile"), cl::Hidden); + +// The named file contains a set of transformations that may have been applied +// to the symbol names between the program from which the sample data was +// collected and the current program's symbols. +static cl::opt<std::string> SampleProfileRemappingFile( + "sample-profile-remapping-file", cl::init(""), cl::value_desc("filename"), + cl::desc("Profile remapping file loaded by -sample-profile"), cl::Hidden); + +static cl::opt<unsigned> SampleProfileMaxPropagateIterations( + "sample-profile-max-propagate-iterations", cl::init(100), + cl::desc("Maximum number of iterations to go through when propagating " + "sample block/edge weights through the CFG.")); + +static cl::opt<unsigned> SampleProfileRecordCoverage( + "sample-profile-check-record-coverage", cl::init(0), cl::value_desc("N"), + cl::desc("Emit a warning if less than N% of records in the input profile " + "are matched to the IR.")); + +static cl::opt<unsigned> SampleProfileSampleCoverage( + "sample-profile-check-sample-coverage", cl::init(0), cl::value_desc("N"), + cl::desc("Emit a warning if less than N% of samples in the input profile " + "are matched to the IR.")); + +static cl::opt<bool> NoWarnSampleUnused( + "no-warn-sample-unused", cl::init(false), cl::Hidden, + cl::desc("Use this option to turn off/on warnings about function with " + "samples but without debug information to use those samples. ")); + +static cl::opt<bool> ProfileSampleAccurate( + "profile-sample-accurate", cl::Hidden, cl::init(false), + cl::desc("If the sample profile is accurate, we will mark all un-sampled " + "callsite and function as having 0 samples. Otherwise, treat " + "un-sampled callsites and functions conservatively as unknown. ")); + +static cl::opt<bool> ProfileAccurateForSymsInList( + "profile-accurate-for-symsinlist", cl::Hidden, cl::ZeroOrMore, + cl::init(true), + cl::desc("For symbols in profile symbol list, regard their profiles to " + "be accurate. It may be overriden by profile-sample-accurate. ")); + +namespace { + +using BlockWeightMap = DenseMap<const BasicBlock *, uint64_t>; +using EquivalenceClassMap = DenseMap<const BasicBlock *, const BasicBlock *>; +using Edge = std::pair<const BasicBlock *, const BasicBlock *>; +using EdgeWeightMap = DenseMap<Edge, uint64_t>; +using BlockEdgeMap = + DenseMap<const BasicBlock *, SmallVector<const BasicBlock *, 8>>; + +class SampleProfileLoader; + +class SampleCoverageTracker { +public: + SampleCoverageTracker(SampleProfileLoader &SPL) : SPLoader(SPL){}; + + bool markSamplesUsed(const FunctionSamples *FS, uint32_t LineOffset, + uint32_t Discriminator, uint64_t Samples); + unsigned computeCoverage(unsigned Used, unsigned Total) const; + unsigned countUsedRecords(const FunctionSamples *FS, + ProfileSummaryInfo *PSI) const; + unsigned countBodyRecords(const FunctionSamples *FS, + ProfileSummaryInfo *PSI) const; + uint64_t getTotalUsedSamples() const { return TotalUsedSamples; } + uint64_t countBodySamples(const FunctionSamples *FS, + ProfileSummaryInfo *PSI) const; + + void clear() { + SampleCoverage.clear(); + TotalUsedSamples = 0; + } + +private: + using BodySampleCoverageMap = std::map<LineLocation, unsigned>; + using FunctionSamplesCoverageMap = + DenseMap<const FunctionSamples *, BodySampleCoverageMap>; + + /// Coverage map for sampling records. + /// + /// This map keeps a record of sampling records that have been matched to + /// an IR instruction. This is used to detect some form of staleness in + /// profiles (see flag -sample-profile-check-coverage). + /// + /// Each entry in the map corresponds to a FunctionSamples instance. This is + /// another map that counts how many times the sample record at the + /// given location has been used. + FunctionSamplesCoverageMap SampleCoverage; + + /// Number of samples used from the profile. + /// + /// When a sampling record is used for the first time, the samples from + /// that record are added to this accumulator. Coverage is later computed + /// based on the total number of samples available in this function and + /// its callsites. + /// + /// Note that this accumulator tracks samples used from a single function + /// and all the inlined callsites. Strictly, we should have a map of counters + /// keyed by FunctionSamples pointers, but these stats are cleared after + /// every function, so we just need to keep a single counter. + uint64_t TotalUsedSamples = 0; + + SampleProfileLoader &SPLoader; +}; + +class GUIDToFuncNameMapper { +public: + GUIDToFuncNameMapper(Module &M, SampleProfileReader &Reader, + DenseMap<uint64_t, StringRef> &GUIDToFuncNameMap) + : CurrentReader(Reader), CurrentModule(M), + CurrentGUIDToFuncNameMap(GUIDToFuncNameMap) { + if (CurrentReader.getFormat() != SPF_Compact_Binary) + return; + + for (const auto &F : CurrentModule) { + StringRef OrigName = F.getName(); + CurrentGUIDToFuncNameMap.insert( + {Function::getGUID(OrigName), OrigName}); + + // Local to global var promotion used by optimization like thinlto + // will rename the var and add suffix like ".llvm.xxx" to the + // original local name. In sample profile, the suffixes of function + // names are all stripped. Since it is possible that the mapper is + // built in post-thin-link phase and var promotion has been done, + // we need to add the substring of function name without the suffix + // into the GUIDToFuncNameMap. + StringRef CanonName = FunctionSamples::getCanonicalFnName(F); + if (CanonName != OrigName) + CurrentGUIDToFuncNameMap.insert( + {Function::getGUID(CanonName), CanonName}); + } + + // Update GUIDToFuncNameMap for each function including inlinees. + SetGUIDToFuncNameMapForAll(&CurrentGUIDToFuncNameMap); + } + + ~GUIDToFuncNameMapper() { + if (CurrentReader.getFormat() != SPF_Compact_Binary) + return; + + CurrentGUIDToFuncNameMap.clear(); + + // Reset GUIDToFuncNameMap for of each function as they're no + // longer valid at this point. + SetGUIDToFuncNameMapForAll(nullptr); + } + +private: + void SetGUIDToFuncNameMapForAll(DenseMap<uint64_t, StringRef> *Map) { + std::queue<FunctionSamples *> FSToUpdate; + for (auto &IFS : CurrentReader.getProfiles()) { + FSToUpdate.push(&IFS.second); + } + + while (!FSToUpdate.empty()) { + FunctionSamples *FS = FSToUpdate.front(); + FSToUpdate.pop(); + FS->GUIDToFuncNameMap = Map; + for (const auto &ICS : FS->getCallsiteSamples()) { + const FunctionSamplesMap &FSMap = ICS.second; + for (auto &IFS : FSMap) { + FunctionSamples &FS = const_cast<FunctionSamples &>(IFS.second); + FSToUpdate.push(&FS); + } + } + } + } + + SampleProfileReader &CurrentReader; + Module &CurrentModule; + DenseMap<uint64_t, StringRef> &CurrentGUIDToFuncNameMap; +}; + +/// Sample profile pass. +/// +/// This pass reads profile data from the file specified by +/// -sample-profile-file and annotates every affected function with the +/// profile information found in that file. +class SampleProfileLoader { +public: + SampleProfileLoader( + StringRef Name, StringRef RemapName, bool IsThinLTOPreLink, + std::function<AssumptionCache &(Function &)> GetAssumptionCache, + std::function<TargetTransformInfo &(Function &)> GetTargetTransformInfo) + : GetAC(std::move(GetAssumptionCache)), + GetTTI(std::move(GetTargetTransformInfo)), CoverageTracker(*this), + Filename(Name), RemappingFilename(RemapName), + IsThinLTOPreLink(IsThinLTOPreLink) {} + + bool doInitialization(Module &M); + bool runOnModule(Module &M, ModuleAnalysisManager *AM, + ProfileSummaryInfo *_PSI); + + void dump() { Reader->dump(); } + +protected: + friend class SampleCoverageTracker; + + bool runOnFunction(Function &F, ModuleAnalysisManager *AM); + unsigned getFunctionLoc(Function &F); + bool emitAnnotations(Function &F); + ErrorOr<uint64_t> getInstWeight(const Instruction &I); + ErrorOr<uint64_t> getBlockWeight(const BasicBlock *BB); + const FunctionSamples *findCalleeFunctionSamples(const Instruction &I) const; + std::vector<const FunctionSamples *> + findIndirectCallFunctionSamples(const Instruction &I, uint64_t &Sum) const; + mutable DenseMap<const DILocation *, const FunctionSamples *> DILocation2SampleMap; + const FunctionSamples *findFunctionSamples(const Instruction &I) const; + bool inlineCallInstruction(Instruction *I); + bool inlineHotFunctions(Function &F, + DenseSet<GlobalValue::GUID> &InlinedGUIDs); + void printEdgeWeight(raw_ostream &OS, Edge E); + void printBlockWeight(raw_ostream &OS, const BasicBlock *BB) const; + void printBlockEquivalence(raw_ostream &OS, const BasicBlock *BB); + bool computeBlockWeights(Function &F); + void findEquivalenceClasses(Function &F); + template <bool IsPostDom> + void findEquivalencesFor(BasicBlock *BB1, ArrayRef<BasicBlock *> Descendants, + DominatorTreeBase<BasicBlock, IsPostDom> *DomTree); + + void propagateWeights(Function &F); + uint64_t visitEdge(Edge E, unsigned *NumUnknownEdges, Edge *UnknownEdge); + void buildEdges(Function &F); + bool propagateThroughEdges(Function &F, bool UpdateBlockCount); + void computeDominanceAndLoopInfo(Function &F); + void clearFunctionData(); + bool callsiteIsHot(const FunctionSamples *CallsiteFS, + ProfileSummaryInfo *PSI); + + /// Map basic blocks to their computed weights. + /// + /// The weight of a basic block is defined to be the maximum + /// of all the instruction weights in that block. + BlockWeightMap BlockWeights; + + /// Map edges to their computed weights. + /// + /// Edge weights are computed by propagating basic block weights in + /// SampleProfile::propagateWeights. + EdgeWeightMap EdgeWeights; + + /// Set of visited blocks during propagation. + SmallPtrSet<const BasicBlock *, 32> VisitedBlocks; + + /// Set of visited edges during propagation. + SmallSet<Edge, 32> VisitedEdges; + + /// Equivalence classes for block weights. + /// + /// Two blocks BB1 and BB2 are in the same equivalence class if they + /// dominate and post-dominate each other, and they are in the same loop + /// nest. When this happens, the two blocks are guaranteed to execute + /// the same number of times. + EquivalenceClassMap EquivalenceClass; + + /// Map from function name to Function *. Used to find the function from + /// the function name. If the function name contains suffix, additional + /// entry is added to map from the stripped name to the function if there + /// is one-to-one mapping. + StringMap<Function *> SymbolMap; + + /// Dominance, post-dominance and loop information. + std::unique_ptr<DominatorTree> DT; + std::unique_ptr<PostDominatorTree> PDT; + std::unique_ptr<LoopInfo> LI; + + std::function<AssumptionCache &(Function &)> GetAC; + std::function<TargetTransformInfo &(Function &)> GetTTI; + + /// Predecessors for each basic block in the CFG. + BlockEdgeMap Predecessors; + + /// Successors for each basic block in the CFG. + BlockEdgeMap Successors; + + SampleCoverageTracker CoverageTracker; + + /// Profile reader object. + std::unique_ptr<SampleProfileReader> Reader; + + /// Samples collected for the body of this function. + FunctionSamples *Samples = nullptr; + + /// Name of the profile file to load. + std::string Filename; + + /// Name of the profile remapping file to load. + std::string RemappingFilename; + + /// Flag indicating whether the profile input loaded successfully. + bool ProfileIsValid = false; + + /// Flag indicating if the pass is invoked in ThinLTO compile phase. + /// + /// In this phase, in annotation, we should not promote indirect calls. + /// Instead, we will mark GUIDs that needs to be annotated to the function. + bool IsThinLTOPreLink; + + /// Profile Summary Info computed from sample profile. + ProfileSummaryInfo *PSI = nullptr; + + /// Profle Symbol list tells whether a function name appears in the binary + /// used to generate the current profile. + std::unique_ptr<ProfileSymbolList> PSL; + + /// Total number of samples collected in this profile. + /// + /// This is the sum of all the samples collected in all the functions executed + /// at runtime. + uint64_t TotalCollectedSamples = 0; + + /// Optimization Remark Emitter used to emit diagnostic remarks. + OptimizationRemarkEmitter *ORE = nullptr; + + // Information recorded when we declined to inline a call site + // because we have determined it is too cold is accumulated for + // each callee function. Initially this is just the entry count. + struct NotInlinedProfileInfo { + uint64_t entryCount; + }; + DenseMap<Function *, NotInlinedProfileInfo> notInlinedCallInfo; + + // GUIDToFuncNameMap saves the mapping from GUID to the symbol name, for + // all the function symbols defined or declared in current module. + DenseMap<uint64_t, StringRef> GUIDToFuncNameMap; + + // All the Names used in FunctionSamples including outline function + // names, inline instance names and call target names. + StringSet<> NamesInProfile; + + // For symbol in profile symbol list, whether to regard their profiles + // to be accurate. It is mainly decided by existance of profile symbol + // list and -profile-accurate-for-symsinlist flag, but it can be + // overriden by -profile-sample-accurate or profile-sample-accurate + // attribute. + bool ProfAccForSymsInList; +}; + +class SampleProfileLoaderLegacyPass : public ModulePass { +public: + // Class identification, replacement for typeinfo + static char ID; + + SampleProfileLoaderLegacyPass(StringRef Name = SampleProfileFile, + bool IsThinLTOPreLink = false) + : ModulePass(ID), + SampleLoader(Name, SampleProfileRemappingFile, IsThinLTOPreLink, + [&](Function &F) -> AssumptionCache & { + return ACT->getAssumptionCache(F); + }, + [&](Function &F) -> TargetTransformInfo & { + return TTIWP->getTTI(F); + }) { + initializeSampleProfileLoaderLegacyPassPass( + *PassRegistry::getPassRegistry()); + } + + void dump() { SampleLoader.dump(); } + + bool doInitialization(Module &M) override { + return SampleLoader.doInitialization(M); + } + + StringRef getPassName() const override { return "Sample profile pass"; } + bool runOnModule(Module &M) override; + + void getAnalysisUsage(AnalysisUsage &AU) const override { + AU.addRequired<AssumptionCacheTracker>(); + AU.addRequired<TargetTransformInfoWrapperPass>(); + AU.addRequired<ProfileSummaryInfoWrapperPass>(); + } + +private: + SampleProfileLoader SampleLoader; + AssumptionCacheTracker *ACT = nullptr; + TargetTransformInfoWrapperPass *TTIWP = nullptr; +}; + +} // end anonymous namespace + +/// Return true if the given callsite is hot wrt to hot cutoff threshold. +/// +/// Functions that were inlined in the original binary will be represented +/// in the inline stack in the sample profile. If the profile shows that +/// the original inline decision was "good" (i.e., the callsite is executed +/// frequently), then we will recreate the inline decision and apply the +/// profile from the inlined callsite. +/// +/// To decide whether an inlined callsite is hot, we compare the callsite +/// sample count with the hot cutoff computed by ProfileSummaryInfo, it is +/// regarded as hot if the count is above the cutoff value. +/// +/// When ProfileAccurateForSymsInList is enabled and profile symbol list +/// is present, functions in the profile symbol list but without profile will +/// be regarded as cold and much less inlining will happen in CGSCC inlining +/// pass, so we tend to lower the hot criteria here to allow more early +/// inlining to happen for warm callsites and it is helpful for performance. +bool SampleProfileLoader::callsiteIsHot(const FunctionSamples *CallsiteFS, + ProfileSummaryInfo *PSI) { + if (!CallsiteFS) + return false; // The callsite was not inlined in the original binary. + + assert(PSI && "PSI is expected to be non null"); + uint64_t CallsiteTotalSamples = CallsiteFS->getTotalSamples(); + if (ProfAccForSymsInList) + return !PSI->isColdCount(CallsiteTotalSamples); + else + return PSI->isHotCount(CallsiteTotalSamples); +} + +/// Mark as used the sample record for the given function samples at +/// (LineOffset, Discriminator). +/// +/// \returns true if this is the first time we mark the given record. +bool SampleCoverageTracker::markSamplesUsed(const FunctionSamples *FS, + uint32_t LineOffset, + uint32_t Discriminator, + uint64_t Samples) { + LineLocation Loc(LineOffset, Discriminator); + unsigned &Count = SampleCoverage[FS][Loc]; + bool FirstTime = (++Count == 1); + if (FirstTime) + TotalUsedSamples += Samples; + return FirstTime; +} + +/// Return the number of sample records that were applied from this profile. +/// +/// This count does not include records from cold inlined callsites. +unsigned +SampleCoverageTracker::countUsedRecords(const FunctionSamples *FS, + ProfileSummaryInfo *PSI) const { + auto I = SampleCoverage.find(FS); + + // The size of the coverage map for FS represents the number of records + // that were marked used at least once. + unsigned Count = (I != SampleCoverage.end()) ? I->second.size() : 0; + + // If there are inlined callsites in this function, count the samples found + // in the respective bodies. However, do not bother counting callees with 0 + // total samples, these are callees that were never invoked at runtime. + for (const auto &I : FS->getCallsiteSamples()) + for (const auto &J : I.second) { + const FunctionSamples *CalleeSamples = &J.second; + if (SPLoader.callsiteIsHot(CalleeSamples, PSI)) + Count += countUsedRecords(CalleeSamples, PSI); + } + + return Count; +} + +/// Return the number of sample records in the body of this profile. +/// +/// This count does not include records from cold inlined callsites. +unsigned +SampleCoverageTracker::countBodyRecords(const FunctionSamples *FS, + ProfileSummaryInfo *PSI) const { + unsigned Count = FS->getBodySamples().size(); + + // Only count records in hot callsites. + for (const auto &I : FS->getCallsiteSamples()) + for (const auto &J : I.second) { + const FunctionSamples *CalleeSamples = &J.second; + if (SPLoader.callsiteIsHot(CalleeSamples, PSI)) + Count += countBodyRecords(CalleeSamples, PSI); + } + + return Count; +} + +/// Return the number of samples collected in the body of this profile. +/// +/// This count does not include samples from cold inlined callsites. +uint64_t +SampleCoverageTracker::countBodySamples(const FunctionSamples *FS, + ProfileSummaryInfo *PSI) const { + uint64_t Total = 0; + for (const auto &I : FS->getBodySamples()) + Total += I.second.getSamples(); + + // Only count samples in hot callsites. + for (const auto &I : FS->getCallsiteSamples()) + for (const auto &J : I.second) { + const FunctionSamples *CalleeSamples = &J.second; + if (SPLoader.callsiteIsHot(CalleeSamples, PSI)) + Total += countBodySamples(CalleeSamples, PSI); + } + + return Total; +} + +/// Return the fraction of sample records used in this profile. +/// +/// The returned value is an unsigned integer in the range 0-100 indicating +/// the percentage of sample records that were used while applying this +/// profile to the associated function. +unsigned SampleCoverageTracker::computeCoverage(unsigned Used, + unsigned Total) const { + assert(Used <= Total && + "number of used records cannot exceed the total number of records"); + return Total > 0 ? Used * 100 / Total : 100; +} + +/// Clear all the per-function data used to load samples and propagate weights. +void SampleProfileLoader::clearFunctionData() { + BlockWeights.clear(); + EdgeWeights.clear(); + VisitedBlocks.clear(); + VisitedEdges.clear(); + EquivalenceClass.clear(); + DT = nullptr; + PDT = nullptr; + LI = nullptr; + Predecessors.clear(); + Successors.clear(); + CoverageTracker.clear(); +} + +#ifndef NDEBUG +/// Print the weight of edge \p E on stream \p OS. +/// +/// \param OS Stream to emit the output to. +/// \param E Edge to print. +void SampleProfileLoader::printEdgeWeight(raw_ostream &OS, Edge E) { + OS << "weight[" << E.first->getName() << "->" << E.second->getName() + << "]: " << EdgeWeights[E] << "\n"; +} + +/// Print the equivalence class of block \p BB on stream \p OS. +/// +/// \param OS Stream to emit the output to. +/// \param BB Block to print. +void SampleProfileLoader::printBlockEquivalence(raw_ostream &OS, + const BasicBlock *BB) { + const BasicBlock *Equiv = EquivalenceClass[BB]; + OS << "equivalence[" << BB->getName() + << "]: " << ((Equiv) ? EquivalenceClass[BB]->getName() : "NONE") << "\n"; +} + +/// Print the weight of block \p BB on stream \p OS. +/// +/// \param OS Stream to emit the output to. +/// \param BB Block to print. +void SampleProfileLoader::printBlockWeight(raw_ostream &OS, + const BasicBlock *BB) const { + const auto &I = BlockWeights.find(BB); + uint64_t W = (I == BlockWeights.end() ? 0 : I->second); + OS << "weight[" << BB->getName() << "]: " << W << "\n"; +} +#endif + +/// Get the weight for an instruction. +/// +/// The "weight" of an instruction \p Inst is the number of samples +/// collected on that instruction at runtime. To retrieve it, we +/// need to compute the line number of \p Inst relative to the start of its +/// function. We use HeaderLineno to compute the offset. We then +/// look up the samples collected for \p Inst using BodySamples. +/// +/// \param Inst Instruction to query. +/// +/// \returns the weight of \p Inst. +ErrorOr<uint64_t> SampleProfileLoader::getInstWeight(const Instruction &Inst) { + const DebugLoc &DLoc = Inst.getDebugLoc(); + if (!DLoc) + return std::error_code(); + + const FunctionSamples *FS = findFunctionSamples(Inst); + if (!FS) + return std::error_code(); + + // Ignore all intrinsics, phinodes and branch instructions. + // Branch and phinodes instruction usually contains debug info from sources outside of + // the residing basic block, thus we ignore them during annotation. + if (isa<BranchInst>(Inst) || isa<IntrinsicInst>(Inst) || isa<PHINode>(Inst)) + return std::error_code(); + + // If a direct call/invoke instruction is inlined in profile + // (findCalleeFunctionSamples returns non-empty result), but not inlined here, + // it means that the inlined callsite has no sample, thus the call + // instruction should have 0 count. + if ((isa<CallInst>(Inst) || isa<InvokeInst>(Inst)) && + !ImmutableCallSite(&Inst).isIndirectCall() && + findCalleeFunctionSamples(Inst)) + return 0; + + const DILocation *DIL = DLoc; + uint32_t LineOffset = FunctionSamples::getOffset(DIL); + uint32_t Discriminator = DIL->getBaseDiscriminator(); + ErrorOr<uint64_t> R = FS->findSamplesAt(LineOffset, Discriminator); + if (R) { + bool FirstMark = + CoverageTracker.markSamplesUsed(FS, LineOffset, Discriminator, R.get()); + if (FirstMark) { + ORE->emit([&]() { + OptimizationRemarkAnalysis Remark(DEBUG_TYPE, "AppliedSamples", &Inst); + Remark << "Applied " << ore::NV("NumSamples", *R); + Remark << " samples from profile (offset: "; + Remark << ore::NV("LineOffset", LineOffset); + if (Discriminator) { + Remark << "."; + Remark << ore::NV("Discriminator", Discriminator); + } + Remark << ")"; + return Remark; + }); + } + LLVM_DEBUG(dbgs() << " " << DLoc.getLine() << "." + << DIL->getBaseDiscriminator() << ":" << Inst + << " (line offset: " << LineOffset << "." + << DIL->getBaseDiscriminator() << " - weight: " << R.get() + << ")\n"); + } + return R; +} + +/// Compute the weight of a basic block. +/// +/// The weight of basic block \p BB is the maximum weight of all the +/// instructions in BB. +/// +/// \param BB The basic block to query. +/// +/// \returns the weight for \p BB. +ErrorOr<uint64_t> SampleProfileLoader::getBlockWeight(const BasicBlock *BB) { + uint64_t Max = 0; + bool HasWeight = false; + for (auto &I : BB->getInstList()) { + const ErrorOr<uint64_t> &R = getInstWeight(I); + if (R) { + Max = std::max(Max, R.get()); + HasWeight = true; + } + } + return HasWeight ? ErrorOr<uint64_t>(Max) : std::error_code(); +} + +/// Compute and store the weights of every basic block. +/// +/// This populates the BlockWeights map by computing +/// the weights of every basic block in the CFG. +/// +/// \param F The function to query. +bool SampleProfileLoader::computeBlockWeights(Function &F) { + bool Changed = false; + LLVM_DEBUG(dbgs() << "Block weights\n"); + for (const auto &BB : F) { + ErrorOr<uint64_t> Weight = getBlockWeight(&BB); + if (Weight) { + BlockWeights[&BB] = Weight.get(); + VisitedBlocks.insert(&BB); + Changed = true; + } + LLVM_DEBUG(printBlockWeight(dbgs(), &BB)); + } + + return Changed; +} + +/// Get the FunctionSamples for a call instruction. +/// +/// The FunctionSamples of a call/invoke instruction \p Inst is the inlined +/// instance in which that call instruction is calling to. It contains +/// all samples that resides in the inlined instance. We first find the +/// inlined instance in which the call instruction is from, then we +/// traverse its children to find the callsite with the matching +/// location. +/// +/// \param Inst Call/Invoke instruction to query. +/// +/// \returns The FunctionSamples pointer to the inlined instance. +const FunctionSamples * +SampleProfileLoader::findCalleeFunctionSamples(const Instruction &Inst) const { + const DILocation *DIL = Inst.getDebugLoc(); + if (!DIL) { + return nullptr; + } + + StringRef CalleeName; + if (const CallInst *CI = dyn_cast<CallInst>(&Inst)) + if (Function *Callee = CI->getCalledFunction()) + CalleeName = Callee->getName(); + + const FunctionSamples *FS = findFunctionSamples(Inst); + if (FS == nullptr) + return nullptr; + + return FS->findFunctionSamplesAt(LineLocation(FunctionSamples::getOffset(DIL), + DIL->getBaseDiscriminator()), + CalleeName); +} + +/// Returns a vector of FunctionSamples that are the indirect call targets +/// of \p Inst. The vector is sorted by the total number of samples. Stores +/// the total call count of the indirect call in \p Sum. +std::vector<const FunctionSamples *> +SampleProfileLoader::findIndirectCallFunctionSamples( + const Instruction &Inst, uint64_t &Sum) const { + const DILocation *DIL = Inst.getDebugLoc(); + std::vector<const FunctionSamples *> R; + + if (!DIL) { + return R; + } + + const FunctionSamples *FS = findFunctionSamples(Inst); + if (FS == nullptr) + return R; + + uint32_t LineOffset = FunctionSamples::getOffset(DIL); + uint32_t Discriminator = DIL->getBaseDiscriminator(); + + auto T = FS->findCallTargetMapAt(LineOffset, Discriminator); + Sum = 0; + if (T) + for (const auto &T_C : T.get()) + Sum += T_C.second; + if (const FunctionSamplesMap *M = FS->findFunctionSamplesMapAt(LineLocation( + FunctionSamples::getOffset(DIL), DIL->getBaseDiscriminator()))) { + if (M->empty()) + return R; + for (const auto &NameFS : *M) { + Sum += NameFS.second.getEntrySamples(); + R.push_back(&NameFS.second); + } + llvm::sort(R, [](const FunctionSamples *L, const FunctionSamples *R) { + if (L->getEntrySamples() != R->getEntrySamples()) + return L->getEntrySamples() > R->getEntrySamples(); + return FunctionSamples::getGUID(L->getName()) < + FunctionSamples::getGUID(R->getName()); + }); + } + return R; +} + +/// Get the FunctionSamples for an instruction. +/// +/// The FunctionSamples of an instruction \p Inst is the inlined instance +/// in which that instruction is coming from. We traverse the inline stack +/// of that instruction, and match it with the tree nodes in the profile. +/// +/// \param Inst Instruction to query. +/// +/// \returns the FunctionSamples pointer to the inlined instance. +const FunctionSamples * +SampleProfileLoader::findFunctionSamples(const Instruction &Inst) const { + const DILocation *DIL = Inst.getDebugLoc(); + if (!DIL) + return Samples; + + auto it = DILocation2SampleMap.try_emplace(DIL,nullptr); + if (it.second) + it.first->second = Samples->findFunctionSamples(DIL); + return it.first->second; +} + +bool SampleProfileLoader::inlineCallInstruction(Instruction *I) { + assert(isa<CallInst>(I) || isa<InvokeInst>(I)); + CallSite CS(I); + Function *CalledFunction = CS.getCalledFunction(); + assert(CalledFunction); + DebugLoc DLoc = I->getDebugLoc(); + BasicBlock *BB = I->getParent(); + InlineParams Params = getInlineParams(); + Params.ComputeFullInlineCost = true; + // Checks if there is anything in the reachable portion of the callee at + // this callsite that makes this inlining potentially illegal. Need to + // set ComputeFullInlineCost, otherwise getInlineCost may return early + // when cost exceeds threshold without checking all IRs in the callee. + // The acutal cost does not matter because we only checks isNever() to + // see if it is legal to inline the callsite. + InlineCost Cost = + getInlineCost(cast<CallBase>(*I), Params, GetTTI(*CalledFunction), GetAC, + None, nullptr, nullptr); + if (Cost.isNever()) { + ORE->emit(OptimizationRemark(DEBUG_TYPE, "Not inline", DLoc, BB) + << "incompatible inlining"); + return false; + } + InlineFunctionInfo IFI(nullptr, &GetAC); + if (InlineFunction(CS, IFI)) { + // The call to InlineFunction erases I, so we can't pass it here. + ORE->emit(OptimizationRemark(DEBUG_TYPE, "HotInline", DLoc, BB) + << "inlined hot callee '" << ore::NV("Callee", CalledFunction) + << "' into '" << ore::NV("Caller", BB->getParent()) << "'"); + return true; + } + return false; +} + +/// Iteratively inline hot callsites of a function. +/// +/// Iteratively traverse all callsites of the function \p F, and find if +/// the corresponding inlined instance exists and is hot in profile. If +/// it is hot enough, inline the callsites and adds new callsites of the +/// callee into the caller. If the call is an indirect call, first promote +/// it to direct call. Each indirect call is limited with a single target. +/// +/// \param F function to perform iterative inlining. +/// \param InlinedGUIDs a set to be updated to include all GUIDs that are +/// inlined in the profiled binary. +/// +/// \returns True if there is any inline happened. +bool SampleProfileLoader::inlineHotFunctions( + Function &F, DenseSet<GlobalValue::GUID> &InlinedGUIDs) { + DenseSet<Instruction *> PromotedInsns; + + // ProfAccForSymsInList is used in callsiteIsHot. The assertion makes sure + // Profile symbol list is ignored when profile-sample-accurate is on. + assert((!ProfAccForSymsInList || + (!ProfileSampleAccurate && + !F.hasFnAttribute("profile-sample-accurate"))) && + "ProfAccForSymsInList should be false when profile-sample-accurate " + "is enabled"); + + DenseMap<Instruction *, const FunctionSamples *> localNotInlinedCallSites; + bool Changed = false; + while (true) { + bool LocalChanged = false; + SmallVector<Instruction *, 10> CIS; + for (auto &BB : F) { + bool Hot = false; + SmallVector<Instruction *, 10> Candidates; + for (auto &I : BB.getInstList()) { + const FunctionSamples *FS = nullptr; + if ((isa<CallInst>(I) || isa<InvokeInst>(I)) && + !isa<IntrinsicInst>(I) && (FS = findCalleeFunctionSamples(I))) { + Candidates.push_back(&I); + if (FS->getEntrySamples() > 0) + localNotInlinedCallSites.try_emplace(&I, FS); + if (callsiteIsHot(FS, PSI)) + Hot = true; + } + } + if (Hot) { + CIS.insert(CIS.begin(), Candidates.begin(), Candidates.end()); + } + } + for (auto I : CIS) { + Function *CalledFunction = CallSite(I).getCalledFunction(); + // Do not inline recursive calls. + if (CalledFunction == &F) + continue; + if (CallSite(I).isIndirectCall()) { + if (PromotedInsns.count(I)) + continue; + uint64_t Sum; + for (const auto *FS : findIndirectCallFunctionSamples(*I, Sum)) { + if (IsThinLTOPreLink) { + FS->findInlinedFunctions(InlinedGUIDs, F.getParent(), + PSI->getOrCompHotCountThreshold()); + continue; + } + auto CalleeFunctionName = FS->getFuncNameInModule(F.getParent()); + // If it is a recursive call, we do not inline it as it could bloat + // the code exponentially. There is way to better handle this, e.g. + // clone the caller first, and inline the cloned caller if it is + // recursive. As llvm does not inline recursive calls, we will + // simply ignore it instead of handling it explicitly. + if (CalleeFunctionName == F.getName()) + continue; + + if (!callsiteIsHot(FS, PSI)) + continue; + + const char *Reason = "Callee function not available"; + auto R = SymbolMap.find(CalleeFunctionName); + if (R != SymbolMap.end() && R->getValue() && + !R->getValue()->isDeclaration() && + R->getValue()->getSubprogram() && + isLegalToPromote(CallSite(I), R->getValue(), &Reason)) { + uint64_t C = FS->getEntrySamples(); + Instruction *DI = + pgo::promoteIndirectCall(I, R->getValue(), C, Sum, false, ORE); + Sum -= C; + PromotedInsns.insert(I); + // If profile mismatches, we should not attempt to inline DI. + if ((isa<CallInst>(DI) || isa<InvokeInst>(DI)) && + inlineCallInstruction(DI)) { + localNotInlinedCallSites.erase(I); + LocalChanged = true; + } + } else { + LLVM_DEBUG(dbgs() + << "\nFailed to promote indirect call to " + << CalleeFunctionName << " because " << Reason << "\n"); + } + } + } else if (CalledFunction && CalledFunction->getSubprogram() && + !CalledFunction->isDeclaration()) { + if (inlineCallInstruction(I)) { + localNotInlinedCallSites.erase(I); + LocalChanged = true; + } + } else if (IsThinLTOPreLink) { + findCalleeFunctionSamples(*I)->findInlinedFunctions( + InlinedGUIDs, F.getParent(), PSI->getOrCompHotCountThreshold()); + } + } + if (LocalChanged) { + Changed = true; + } else { + break; + } + } + + // Accumulate not inlined callsite information into notInlinedSamples + for (const auto &Pair : localNotInlinedCallSites) { + Instruction *I = Pair.getFirst(); + Function *Callee = CallSite(I).getCalledFunction(); + if (!Callee || Callee->isDeclaration()) + continue; + const FunctionSamples *FS = Pair.getSecond(); + auto pair = + notInlinedCallInfo.try_emplace(Callee, NotInlinedProfileInfo{0}); + pair.first->second.entryCount += FS->getEntrySamples(); + } + return Changed; +} + +/// Find equivalence classes for the given block. +/// +/// This finds all the blocks that are guaranteed to execute the same +/// number of times as \p BB1. To do this, it traverses all the +/// descendants of \p BB1 in the dominator or post-dominator tree. +/// +/// A block BB2 will be in the same equivalence class as \p BB1 if +/// the following holds: +/// +/// 1- \p BB1 is a descendant of BB2 in the opposite tree. So, if BB2 +/// is a descendant of \p BB1 in the dominator tree, then BB2 should +/// dominate BB1 in the post-dominator tree. +/// +/// 2- Both BB2 and \p BB1 must be in the same loop. +/// +/// For every block BB2 that meets those two requirements, we set BB2's +/// equivalence class to \p BB1. +/// +/// \param BB1 Block to check. +/// \param Descendants Descendants of \p BB1 in either the dom or pdom tree. +/// \param DomTree Opposite dominator tree. If \p Descendants is filled +/// with blocks from \p BB1's dominator tree, then +/// this is the post-dominator tree, and vice versa. +template <bool IsPostDom> +void SampleProfileLoader::findEquivalencesFor( + BasicBlock *BB1, ArrayRef<BasicBlock *> Descendants, + DominatorTreeBase<BasicBlock, IsPostDom> *DomTree) { + const BasicBlock *EC = EquivalenceClass[BB1]; + uint64_t Weight = BlockWeights[EC]; + for (const auto *BB2 : Descendants) { + bool IsDomParent = DomTree->dominates(BB2, BB1); + bool IsInSameLoop = LI->getLoopFor(BB1) == LI->getLoopFor(BB2); + if (BB1 != BB2 && IsDomParent && IsInSameLoop) { + EquivalenceClass[BB2] = EC; + // If BB2 is visited, then the entire EC should be marked as visited. + if (VisitedBlocks.count(BB2)) { + VisitedBlocks.insert(EC); + } + + // If BB2 is heavier than BB1, make BB2 have the same weight + // as BB1. + // + // Note that we don't worry about the opposite situation here + // (when BB2 is lighter than BB1). We will deal with this + // during the propagation phase. Right now, we just want to + // make sure that BB1 has the largest weight of all the + // members of its equivalence set. + Weight = std::max(Weight, BlockWeights[BB2]); + } + } + if (EC == &EC->getParent()->getEntryBlock()) { + BlockWeights[EC] = Samples->getHeadSamples() + 1; + } else { + BlockWeights[EC] = Weight; + } +} + +/// Find equivalence classes. +/// +/// Since samples may be missing from blocks, we can fill in the gaps by setting +/// the weights of all the blocks in the same equivalence class to the same +/// weight. To compute the concept of equivalence, we use dominance and loop +/// information. Two blocks B1 and B2 are in the same equivalence class if B1 +/// dominates B2, B2 post-dominates B1 and both are in the same loop. +/// +/// \param F The function to query. +void SampleProfileLoader::findEquivalenceClasses(Function &F) { + SmallVector<BasicBlock *, 8> DominatedBBs; + LLVM_DEBUG(dbgs() << "\nBlock equivalence classes\n"); + // Find equivalence sets based on dominance and post-dominance information. + for (auto &BB : F) { + BasicBlock *BB1 = &BB; + + // Compute BB1's equivalence class once. + if (EquivalenceClass.count(BB1)) { + LLVM_DEBUG(printBlockEquivalence(dbgs(), BB1)); + continue; + } + + // By default, blocks are in their own equivalence class. + EquivalenceClass[BB1] = BB1; + + // Traverse all the blocks dominated by BB1. We are looking for + // every basic block BB2 such that: + // + // 1- BB1 dominates BB2. + // 2- BB2 post-dominates BB1. + // 3- BB1 and BB2 are in the same loop nest. + // + // If all those conditions hold, it means that BB2 is executed + // as many times as BB1, so they are placed in the same equivalence + // class by making BB2's equivalence class be BB1. + DominatedBBs.clear(); + DT->getDescendants(BB1, DominatedBBs); + findEquivalencesFor(BB1, DominatedBBs, PDT.get()); + + LLVM_DEBUG(printBlockEquivalence(dbgs(), BB1)); + } + + // Assign weights to equivalence classes. + // + // All the basic blocks in the same equivalence class will execute + // the same number of times. Since we know that the head block in + // each equivalence class has the largest weight, assign that weight + // to all the blocks in that equivalence class. + LLVM_DEBUG( + dbgs() << "\nAssign the same weight to all blocks in the same class\n"); + for (auto &BI : F) { + const BasicBlock *BB = &BI; + const BasicBlock *EquivBB = EquivalenceClass[BB]; + if (BB != EquivBB) + BlockWeights[BB] = BlockWeights[EquivBB]; + LLVM_DEBUG(printBlockWeight(dbgs(), BB)); + } +} + +/// Visit the given edge to decide if it has a valid weight. +/// +/// If \p E has not been visited before, we copy to \p UnknownEdge +/// and increment the count of unknown edges. +/// +/// \param E Edge to visit. +/// \param NumUnknownEdges Current number of unknown edges. +/// \param UnknownEdge Set if E has not been visited before. +/// +/// \returns E's weight, if known. Otherwise, return 0. +uint64_t SampleProfileLoader::visitEdge(Edge E, unsigned *NumUnknownEdges, + Edge *UnknownEdge) { + if (!VisitedEdges.count(E)) { + (*NumUnknownEdges)++; + *UnknownEdge = E; + return 0; + } + + return EdgeWeights[E]; +} + +/// Propagate weights through incoming/outgoing edges. +/// +/// If the weight of a basic block is known, and there is only one edge +/// with an unknown weight, we can calculate the weight of that edge. +/// +/// Similarly, if all the edges have a known count, we can calculate the +/// count of the basic block, if needed. +/// +/// \param F Function to process. +/// \param UpdateBlockCount Whether we should update basic block counts that +/// has already been annotated. +/// +/// \returns True if new weights were assigned to edges or blocks. +bool SampleProfileLoader::propagateThroughEdges(Function &F, + bool UpdateBlockCount) { + bool Changed = false; + LLVM_DEBUG(dbgs() << "\nPropagation through edges\n"); + for (const auto &BI : F) { + const BasicBlock *BB = &BI; + const BasicBlock *EC = EquivalenceClass[BB]; + + // Visit all the predecessor and successor edges to determine + // which ones have a weight assigned already. Note that it doesn't + // matter that we only keep track of a single unknown edge. The + // only case we are interested in handling is when only a single + // edge is unknown (see setEdgeOrBlockWeight). + for (unsigned i = 0; i < 2; i++) { + uint64_t TotalWeight = 0; + unsigned NumUnknownEdges = 0, NumTotalEdges = 0; + Edge UnknownEdge, SelfReferentialEdge, SingleEdge; + + if (i == 0) { + // First, visit all predecessor edges. + NumTotalEdges = Predecessors[BB].size(); + for (auto *Pred : Predecessors[BB]) { + Edge E = std::make_pair(Pred, BB); + TotalWeight += visitEdge(E, &NumUnknownEdges, &UnknownEdge); + if (E.first == E.second) + SelfReferentialEdge = E; + } + if (NumTotalEdges == 1) { + SingleEdge = std::make_pair(Predecessors[BB][0], BB); + } + } else { + // On the second round, visit all successor edges. + NumTotalEdges = Successors[BB].size(); + for (auto *Succ : Successors[BB]) { + Edge E = std::make_pair(BB, Succ); + TotalWeight += visitEdge(E, &NumUnknownEdges, &UnknownEdge); + } + if (NumTotalEdges == 1) { + SingleEdge = std::make_pair(BB, Successors[BB][0]); + } + } + + // After visiting all the edges, there are three cases that we + // can handle immediately: + // + // - All the edge weights are known (i.e., NumUnknownEdges == 0). + // In this case, we simply check that the sum of all the edges + // is the same as BB's weight. If not, we change BB's weight + // to match. Additionally, if BB had not been visited before, + // we mark it visited. + // + // - Only one edge is unknown and BB has already been visited. + // In this case, we can compute the weight of the edge by + // subtracting the total block weight from all the known + // edge weights. If the edges weight more than BB, then the + // edge of the last remaining edge is set to zero. + // + // - There exists a self-referential edge and the weight of BB is + // known. In this case, this edge can be based on BB's weight. + // We add up all the other known edges and set the weight on + // the self-referential edge as we did in the previous case. + // + // In any other case, we must continue iterating. Eventually, + // all edges will get a weight, or iteration will stop when + // it reaches SampleProfileMaxPropagateIterations. + if (NumUnknownEdges <= 1) { + uint64_t &BBWeight = BlockWeights[EC]; + if (NumUnknownEdges == 0) { + if (!VisitedBlocks.count(EC)) { + // If we already know the weight of all edges, the weight of the + // basic block can be computed. It should be no larger than the sum + // of all edge weights. + if (TotalWeight > BBWeight) { + BBWeight = TotalWeight; + Changed = true; + LLVM_DEBUG(dbgs() << "All edge weights for " << BB->getName() + << " known. Set weight for block: "; + printBlockWeight(dbgs(), BB);); + } + } else if (NumTotalEdges == 1 && + EdgeWeights[SingleEdge] < BlockWeights[EC]) { + // If there is only one edge for the visited basic block, use the + // block weight to adjust edge weight if edge weight is smaller. + EdgeWeights[SingleEdge] = BlockWeights[EC]; + Changed = true; + } + } else if (NumUnknownEdges == 1 && VisitedBlocks.count(EC)) { + // If there is a single unknown edge and the block has been + // visited, then we can compute E's weight. + if (BBWeight >= TotalWeight) + EdgeWeights[UnknownEdge] = BBWeight - TotalWeight; + else + EdgeWeights[UnknownEdge] = 0; + const BasicBlock *OtherEC; + if (i == 0) + OtherEC = EquivalenceClass[UnknownEdge.first]; + else + OtherEC = EquivalenceClass[UnknownEdge.second]; + // Edge weights should never exceed the BB weights it connects. + if (VisitedBlocks.count(OtherEC) && + EdgeWeights[UnknownEdge] > BlockWeights[OtherEC]) + EdgeWeights[UnknownEdge] = BlockWeights[OtherEC]; + VisitedEdges.insert(UnknownEdge); + Changed = true; + LLVM_DEBUG(dbgs() << "Set weight for edge: "; + printEdgeWeight(dbgs(), UnknownEdge)); + } + } else if (VisitedBlocks.count(EC) && BlockWeights[EC] == 0) { + // If a block Weights 0, all its in/out edges should weight 0. + if (i == 0) { + for (auto *Pred : Predecessors[BB]) { + Edge E = std::make_pair(Pred, BB); + EdgeWeights[E] = 0; + VisitedEdges.insert(E); + } + } else { + for (auto *Succ : Successors[BB]) { + Edge E = std::make_pair(BB, Succ); + EdgeWeights[E] = 0; + VisitedEdges.insert(E); + } + } + } else if (SelfReferentialEdge.first && VisitedBlocks.count(EC)) { + uint64_t &BBWeight = BlockWeights[BB]; + // We have a self-referential edge and the weight of BB is known. + if (BBWeight >= TotalWeight) + EdgeWeights[SelfReferentialEdge] = BBWeight - TotalWeight; + else + EdgeWeights[SelfReferentialEdge] = 0; + VisitedEdges.insert(SelfReferentialEdge); + Changed = true; + LLVM_DEBUG(dbgs() << "Set self-referential edge weight to: "; + printEdgeWeight(dbgs(), SelfReferentialEdge)); + } + if (UpdateBlockCount && !VisitedBlocks.count(EC) && TotalWeight > 0) { + BlockWeights[EC] = TotalWeight; + VisitedBlocks.insert(EC); + Changed = true; + } + } + } + + return Changed; +} + +/// Build in/out edge lists for each basic block in the CFG. +/// +/// We are interested in unique edges. If a block B1 has multiple +/// edges to another block B2, we only add a single B1->B2 edge. +void SampleProfileLoader::buildEdges(Function &F) { + for (auto &BI : F) { + BasicBlock *B1 = &BI; + + // Add predecessors for B1. + SmallPtrSet<BasicBlock *, 16> Visited; + if (!Predecessors[B1].empty()) + llvm_unreachable("Found a stale predecessors list in a basic block."); + for (pred_iterator PI = pred_begin(B1), PE = pred_end(B1); PI != PE; ++PI) { + BasicBlock *B2 = *PI; + if (Visited.insert(B2).second) + Predecessors[B1].push_back(B2); + } + + // Add successors for B1. + Visited.clear(); + if (!Successors[B1].empty()) + llvm_unreachable("Found a stale successors list in a basic block."); + for (succ_iterator SI = succ_begin(B1), SE = succ_end(B1); SI != SE; ++SI) { + BasicBlock *B2 = *SI; + if (Visited.insert(B2).second) + Successors[B1].push_back(B2); + } + } +} + +/// Returns the sorted CallTargetMap \p M by count in descending order. +static SmallVector<InstrProfValueData, 2> GetSortedValueDataFromCallTargets( + const SampleRecord::CallTargetMap & M) { + SmallVector<InstrProfValueData, 2> R; + for (const auto &I : SampleRecord::SortCallTargets(M)) { + R.emplace_back(InstrProfValueData{FunctionSamples::getGUID(I.first), I.second}); + } + return R; +} + +/// Propagate weights into edges +/// +/// The following rules are applied to every block BB in the CFG: +/// +/// - If BB has a single predecessor/successor, then the weight +/// of that edge is the weight of the block. +/// +/// - If all incoming or outgoing edges are known except one, and the +/// weight of the block is already known, the weight of the unknown +/// edge will be the weight of the block minus the sum of all the known +/// edges. If the sum of all the known edges is larger than BB's weight, +/// we set the unknown edge weight to zero. +/// +/// - If there is a self-referential edge, and the weight of the block is +/// known, the weight for that edge is set to the weight of the block +/// minus the weight of the other incoming edges to that block (if +/// known). +void SampleProfileLoader::propagateWeights(Function &F) { + bool Changed = true; + unsigned I = 0; + + // If BB weight is larger than its corresponding loop's header BB weight, + // use the BB weight to replace the loop header BB weight. + for (auto &BI : F) { + BasicBlock *BB = &BI; + Loop *L = LI->getLoopFor(BB); + if (!L) { + continue; + } + BasicBlock *Header = L->getHeader(); + if (Header && BlockWeights[BB] > BlockWeights[Header]) { + BlockWeights[Header] = BlockWeights[BB]; + } + } + + // Before propagation starts, build, for each block, a list of + // unique predecessors and successors. This is necessary to handle + // identical edges in multiway branches. Since we visit all blocks and all + // edges of the CFG, it is cleaner to build these lists once at the start + // of the pass. + buildEdges(F); + + // Propagate until we converge or we go past the iteration limit. + while (Changed && I++ < SampleProfileMaxPropagateIterations) { + Changed = propagateThroughEdges(F, false); + } + + // The first propagation propagates BB counts from annotated BBs to unknown + // BBs. The 2nd propagation pass resets edges weights, and use all BB weights + // to propagate edge weights. + VisitedEdges.clear(); + Changed = true; + while (Changed && I++ < SampleProfileMaxPropagateIterations) { + Changed = propagateThroughEdges(F, false); + } + + // The 3rd propagation pass allows adjust annotated BB weights that are + // obviously wrong. + Changed = true; + while (Changed && I++ < SampleProfileMaxPropagateIterations) { + Changed = propagateThroughEdges(F, true); + } + + // Generate MD_prof metadata for every branch instruction using the + // edge weights computed during propagation. + LLVM_DEBUG(dbgs() << "\nPropagation complete. Setting branch weights\n"); + LLVMContext &Ctx = F.getContext(); + MDBuilder MDB(Ctx); + for (auto &BI : F) { + BasicBlock *BB = &BI; + + if (BlockWeights[BB]) { + for (auto &I : BB->getInstList()) { + if (!isa<CallInst>(I) && !isa<InvokeInst>(I)) + continue; + CallSite CS(&I); + if (!CS.getCalledFunction()) { + const DebugLoc &DLoc = I.getDebugLoc(); + if (!DLoc) + continue; + const DILocation *DIL = DLoc; + uint32_t LineOffset = FunctionSamples::getOffset(DIL); + uint32_t Discriminator = DIL->getBaseDiscriminator(); + + const FunctionSamples *FS = findFunctionSamples(I); + if (!FS) + continue; + auto T = FS->findCallTargetMapAt(LineOffset, Discriminator); + if (!T || T.get().empty()) + continue; + SmallVector<InstrProfValueData, 2> SortedCallTargets = + GetSortedValueDataFromCallTargets(T.get()); + uint64_t Sum; + findIndirectCallFunctionSamples(I, Sum); + annotateValueSite(*I.getParent()->getParent()->getParent(), I, + SortedCallTargets, Sum, IPVK_IndirectCallTarget, + SortedCallTargets.size()); + } else if (!isa<IntrinsicInst>(&I)) { + I.setMetadata(LLVMContext::MD_prof, + MDB.createBranchWeights( + {static_cast<uint32_t>(BlockWeights[BB])})); + } + } + } + Instruction *TI = BB->getTerminator(); + if (TI->getNumSuccessors() == 1) + continue; + if (!isa<BranchInst>(TI) && !isa<SwitchInst>(TI)) + continue; + + DebugLoc BranchLoc = TI->getDebugLoc(); + LLVM_DEBUG(dbgs() << "\nGetting weights for branch at line " + << ((BranchLoc) ? Twine(BranchLoc.getLine()) + : Twine("<UNKNOWN LOCATION>")) + << ".\n"); + SmallVector<uint32_t, 4> Weights; + uint32_t MaxWeight = 0; + Instruction *MaxDestInst; + for (unsigned I = 0; I < TI->getNumSuccessors(); ++I) { + BasicBlock *Succ = TI->getSuccessor(I); + Edge E = std::make_pair(BB, Succ); + uint64_t Weight = EdgeWeights[E]; + LLVM_DEBUG(dbgs() << "\t"; printEdgeWeight(dbgs(), E)); + // Use uint32_t saturated arithmetic to adjust the incoming weights, + // if needed. Sample counts in profiles are 64-bit unsigned values, + // but internally branch weights are expressed as 32-bit values. + if (Weight > std::numeric_limits<uint32_t>::max()) { + LLVM_DEBUG(dbgs() << " (saturated due to uint32_t overflow)"); + Weight = std::numeric_limits<uint32_t>::max(); + } + // Weight is added by one to avoid propagation errors introduced by + // 0 weights. + Weights.push_back(static_cast<uint32_t>(Weight + 1)); + if (Weight != 0) { + if (Weight > MaxWeight) { + MaxWeight = Weight; + MaxDestInst = Succ->getFirstNonPHIOrDbgOrLifetime(); + } + } + } + + misexpect::verifyMisExpect(TI, Weights, TI->getContext()); + + uint64_t TempWeight; + // Only set weights if there is at least one non-zero weight. + // In any other case, let the analyzer set weights. + // Do not set weights if the weights are present. In ThinLTO, the profile + // annotation is done twice. If the first annotation already set the + // weights, the second pass does not need to set it. + if (MaxWeight > 0 && !TI->extractProfTotalWeight(TempWeight)) { + LLVM_DEBUG(dbgs() << "SUCCESS. Found non-zero weights.\n"); + TI->setMetadata(LLVMContext::MD_prof, + MDB.createBranchWeights(Weights)); + ORE->emit([&]() { + return OptimizationRemark(DEBUG_TYPE, "PopularDest", MaxDestInst) + << "most popular destination for conditional branches at " + << ore::NV("CondBranchesLoc", BranchLoc); + }); + } else { + LLVM_DEBUG(dbgs() << "SKIPPED. All branch weights are zero.\n"); + } + } +} + +/// Get the line number for the function header. +/// +/// This looks up function \p F in the current compilation unit and +/// retrieves the line number where the function is defined. This is +/// line 0 for all the samples read from the profile file. Every line +/// number is relative to this line. +/// +/// \param F Function object to query. +/// +/// \returns the line number where \p F is defined. If it returns 0, +/// it means that there is no debug information available for \p F. +unsigned SampleProfileLoader::getFunctionLoc(Function &F) { + if (DISubprogram *S = F.getSubprogram()) + return S->getLine(); + + if (NoWarnSampleUnused) + return 0; + + // If the start of \p F is missing, emit a diagnostic to inform the user + // about the missed opportunity. + F.getContext().diagnose(DiagnosticInfoSampleProfile( + "No debug information found in function " + F.getName() + + ": Function profile not used", + DS_Warning)); + return 0; +} + +void SampleProfileLoader::computeDominanceAndLoopInfo(Function &F) { + DT.reset(new DominatorTree); + DT->recalculate(F); + + PDT.reset(new PostDominatorTree(F)); + + LI.reset(new LoopInfo); + LI->analyze(*DT); +} + +/// Generate branch weight metadata for all branches in \p F. +/// +/// Branch weights are computed out of instruction samples using a +/// propagation heuristic. Propagation proceeds in 3 phases: +/// +/// 1- Assignment of block weights. All the basic blocks in the function +/// are initial assigned the same weight as their most frequently +/// executed instruction. +/// +/// 2- Creation of equivalence classes. Since samples may be missing from +/// blocks, we can fill in the gaps by setting the weights of all the +/// blocks in the same equivalence class to the same weight. To compute +/// the concept of equivalence, we use dominance and loop information. +/// Two blocks B1 and B2 are in the same equivalence class if B1 +/// dominates B2, B2 post-dominates B1 and both are in the same loop. +/// +/// 3- Propagation of block weights into edges. This uses a simple +/// propagation heuristic. The following rules are applied to every +/// block BB in the CFG: +/// +/// - If BB has a single predecessor/successor, then the weight +/// of that edge is the weight of the block. +/// +/// - If all the edges are known except one, and the weight of the +/// block is already known, the weight of the unknown edge will +/// be the weight of the block minus the sum of all the known +/// edges. If the sum of all the known edges is larger than BB's weight, +/// we set the unknown edge weight to zero. +/// +/// - If there is a self-referential edge, and the weight of the block is +/// known, the weight for that edge is set to the weight of the block +/// minus the weight of the other incoming edges to that block (if +/// known). +/// +/// Since this propagation is not guaranteed to finalize for every CFG, we +/// only allow it to proceed for a limited number of iterations (controlled +/// by -sample-profile-max-propagate-iterations). +/// +/// FIXME: Try to replace this propagation heuristic with a scheme +/// that is guaranteed to finalize. A work-list approach similar to +/// the standard value propagation algorithm used by SSA-CCP might +/// work here. +/// +/// Once all the branch weights are computed, we emit the MD_prof +/// metadata on BB using the computed values for each of its branches. +/// +/// \param F The function to query. +/// +/// \returns true if \p F was modified. Returns false, otherwise. +bool SampleProfileLoader::emitAnnotations(Function &F) { + bool Changed = false; + + if (getFunctionLoc(F) == 0) + return false; + + LLVM_DEBUG(dbgs() << "Line number for the first instruction in " + << F.getName() << ": " << getFunctionLoc(F) << "\n"); + + DenseSet<GlobalValue::GUID> InlinedGUIDs; + Changed |= inlineHotFunctions(F, InlinedGUIDs); + + // Compute basic block weights. + Changed |= computeBlockWeights(F); + + if (Changed) { + // Add an entry count to the function using the samples gathered at the + // function entry. + // Sets the GUIDs that are inlined in the profiled binary. This is used + // for ThinLink to make correct liveness analysis, and also make the IR + // match the profiled binary before annotation. + F.setEntryCount( + ProfileCount(Samples->getHeadSamples() + 1, Function::PCT_Real), + &InlinedGUIDs); + + // Compute dominance and loop info needed for propagation. + computeDominanceAndLoopInfo(F); + + // Find equivalence classes. + findEquivalenceClasses(F); + + // Propagate weights to all edges. + propagateWeights(F); + } + + // If coverage checking was requested, compute it now. + if (SampleProfileRecordCoverage) { + unsigned Used = CoverageTracker.countUsedRecords(Samples, PSI); + unsigned Total = CoverageTracker.countBodyRecords(Samples, PSI); + unsigned Coverage = CoverageTracker.computeCoverage(Used, Total); + if (Coverage < SampleProfileRecordCoverage) { + F.getContext().diagnose(DiagnosticInfoSampleProfile( + F.getSubprogram()->getFilename(), getFunctionLoc(F), + Twine(Used) + " of " + Twine(Total) + " available profile records (" + + Twine(Coverage) + "%) were applied", + DS_Warning)); + } + } + + if (SampleProfileSampleCoverage) { + uint64_t Used = CoverageTracker.getTotalUsedSamples(); + uint64_t Total = CoverageTracker.countBodySamples(Samples, PSI); + unsigned Coverage = CoverageTracker.computeCoverage(Used, Total); + if (Coverage < SampleProfileSampleCoverage) { + F.getContext().diagnose(DiagnosticInfoSampleProfile( + F.getSubprogram()->getFilename(), getFunctionLoc(F), + Twine(Used) + " of " + Twine(Total) + " available profile samples (" + + Twine(Coverage) + "%) were applied", + DS_Warning)); + } + } + return Changed; +} + +char SampleProfileLoaderLegacyPass::ID = 0; + +INITIALIZE_PASS_BEGIN(SampleProfileLoaderLegacyPass, "sample-profile", + "Sample Profile loader", false, false) +INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker) +INITIALIZE_PASS_DEPENDENCY(TargetTransformInfoWrapperPass) +INITIALIZE_PASS_DEPENDENCY(ProfileSummaryInfoWrapperPass) +INITIALIZE_PASS_END(SampleProfileLoaderLegacyPass, "sample-profile", + "Sample Profile loader", false, false) + +bool SampleProfileLoader::doInitialization(Module &M) { + auto &Ctx = M.getContext(); + + std::unique_ptr<SampleProfileReaderItaniumRemapper> RemapReader; + auto ReaderOrErr = + SampleProfileReader::create(Filename, Ctx, RemappingFilename); + if (std::error_code EC = ReaderOrErr.getError()) { + std::string Msg = "Could not open profile: " + EC.message(); + Ctx.diagnose(DiagnosticInfoSampleProfile(Filename, Msg)); + return false; + } + Reader = std::move(ReaderOrErr.get()); + Reader->collectFuncsFrom(M); + ProfileIsValid = (Reader->read() == sampleprof_error::success); + PSL = Reader->getProfileSymbolList(); + + // While profile-sample-accurate is on, ignore symbol list. + ProfAccForSymsInList = + ProfileAccurateForSymsInList && PSL && !ProfileSampleAccurate; + if (ProfAccForSymsInList) { + NamesInProfile.clear(); + if (auto NameTable = Reader->getNameTable()) + NamesInProfile.insert(NameTable->begin(), NameTable->end()); + } + + return true; +} + +ModulePass *llvm::createSampleProfileLoaderPass() { + return new SampleProfileLoaderLegacyPass(); +} + +ModulePass *llvm::createSampleProfileLoaderPass(StringRef Name) { + return new SampleProfileLoaderLegacyPass(Name); +} + +bool SampleProfileLoader::runOnModule(Module &M, ModuleAnalysisManager *AM, + ProfileSummaryInfo *_PSI) { + GUIDToFuncNameMapper Mapper(M, *Reader, GUIDToFuncNameMap); + if (!ProfileIsValid) + return false; + + PSI = _PSI; + if (M.getProfileSummary(/* IsCS */ false) == nullptr) + M.setProfileSummary(Reader->getSummary().getMD(M.getContext()), + ProfileSummary::PSK_Sample); + + // Compute the total number of samples collected in this profile. + for (const auto &I : Reader->getProfiles()) + TotalCollectedSamples += I.second.getTotalSamples(); + + // Populate the symbol map. + for (const auto &N_F : M.getValueSymbolTable()) { + StringRef OrigName = N_F.getKey(); + Function *F = dyn_cast<Function>(N_F.getValue()); + if (F == nullptr) + continue; + SymbolMap[OrigName] = F; + auto pos = OrigName.find('.'); + if (pos != StringRef::npos) { + StringRef NewName = OrigName.substr(0, pos); + auto r = SymbolMap.insert(std::make_pair(NewName, F)); + // Failiing to insert means there is already an entry in SymbolMap, + // thus there are multiple functions that are mapped to the same + // stripped name. In this case of name conflicting, set the value + // to nullptr to avoid confusion. + if (!r.second) + r.first->second = nullptr; + } + } + + bool retval = false; + for (auto &F : M) + if (!F.isDeclaration()) { + clearFunctionData(); + retval |= runOnFunction(F, AM); + } + + // Account for cold calls not inlined.... + for (const std::pair<Function *, NotInlinedProfileInfo> &pair : + notInlinedCallInfo) + updateProfileCallee(pair.first, pair.second.entryCount); + + return retval; +} + +bool SampleProfileLoaderLegacyPass::runOnModule(Module &M) { + ACT = &getAnalysis<AssumptionCacheTracker>(); + TTIWP = &getAnalysis<TargetTransformInfoWrapperPass>(); + ProfileSummaryInfo *PSI = + &getAnalysis<ProfileSummaryInfoWrapperPass>().getPSI(); + return SampleLoader.runOnModule(M, nullptr, PSI); +} + +bool SampleProfileLoader::runOnFunction(Function &F, ModuleAnalysisManager *AM) { + + DILocation2SampleMap.clear(); + // By default the entry count is initialized to -1, which will be treated + // conservatively by getEntryCount as the same as unknown (None). This is + // to avoid newly added code to be treated as cold. If we have samples + // this will be overwritten in emitAnnotations. + uint64_t initialEntryCount = -1; + + ProfAccForSymsInList = ProfileAccurateForSymsInList && PSL; + if (ProfileSampleAccurate || F.hasFnAttribute("profile-sample-accurate")) { + // initialize all the function entry counts to 0. It means all the + // functions without profile will be regarded as cold. + initialEntryCount = 0; + // profile-sample-accurate is a user assertion which has a higher precedence + // than symbol list. When profile-sample-accurate is on, ignore symbol list. + ProfAccForSymsInList = false; + } + + // PSL -- profile symbol list include all the symbols in sampled binary. + // If ProfileAccurateForSymsInList is enabled, PSL is used to treat + // old functions without samples being cold, without having to worry + // about new and hot functions being mistakenly treated as cold. + if (ProfAccForSymsInList) { + // Initialize the entry count to 0 for functions in the list. + if (PSL->contains(F.getName())) + initialEntryCount = 0; + + // Function in the symbol list but without sample will be regarded as + // cold. To minimize the potential negative performance impact it could + // have, we want to be a little conservative here saying if a function + // shows up in the profile, no matter as outline function, inline instance + // or call targets, treat the function as not being cold. This will handle + // the cases such as most callsites of a function are inlined in sampled + // binary but not inlined in current build (because of source code drift, + // imprecise debug information, or the callsites are all cold individually + // but not cold accumulatively...), so the outline function showing up as + // cold in sampled binary will actually not be cold after current build. + StringRef CanonName = FunctionSamples::getCanonicalFnName(F); + if (NamesInProfile.count(CanonName)) + initialEntryCount = -1; + } + + F.setEntryCount(ProfileCount(initialEntryCount, Function::PCT_Real)); + std::unique_ptr<OptimizationRemarkEmitter> OwnedORE; + if (AM) { + auto &FAM = + AM->getResult<FunctionAnalysisManagerModuleProxy>(*F.getParent()) + .getManager(); + ORE = &FAM.getResult<OptimizationRemarkEmitterAnalysis>(F); + } else { + OwnedORE = std::make_unique<OptimizationRemarkEmitter>(&F); + ORE = OwnedORE.get(); + } + Samples = Reader->getSamplesFor(F); + if (Samples && !Samples->empty()) + return emitAnnotations(F); + return false; +} + +PreservedAnalyses SampleProfileLoaderPass::run(Module &M, + ModuleAnalysisManager &AM) { + FunctionAnalysisManager &FAM = + AM.getResult<FunctionAnalysisManagerModuleProxy>(M).getManager(); + + auto GetAssumptionCache = [&](Function &F) -> AssumptionCache & { + return FAM.getResult<AssumptionAnalysis>(F); + }; + auto GetTTI = [&](Function &F) -> TargetTransformInfo & { + return FAM.getResult<TargetIRAnalysis>(F); + }; + + SampleProfileLoader SampleLoader( + ProfileFileName.empty() ? SampleProfileFile : ProfileFileName, + ProfileRemappingFileName.empty() ? SampleProfileRemappingFile + : ProfileRemappingFileName, + IsThinLTOPreLink, GetAssumptionCache, GetTTI); + + SampleLoader.doInitialization(M); + + ProfileSummaryInfo *PSI = &AM.getResult<ProfileSummaryAnalysis>(M); + if (!SampleLoader.runOnModule(M, &AM, PSI)) + return PreservedAnalyses::all(); + + return PreservedAnalyses::none(); +} |