| ////===- SampleProfileLoadBaseImpl.h - Profile loader base impl --*- C++-*-===// |
| // |
| // 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 |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| /// \file |
| /// This file provides the interface for the sampled PGO profile loader base |
| /// implementation. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #ifndef LLVM_TRANSFORMS_UTILS_SAMPLEPROFILELOADERBASEIMPL_H |
| #define LLVM_TRANSFORMS_UTILS_SAMPLEPROFILELOADERBASEIMPL_H |
| |
| #include "llvm/ADT/ArrayRef.h" |
| #include "llvm/ADT/DenseMap.h" |
| #include "llvm/ADT/DenseSet.h" |
| #include "llvm/ADT/SmallPtrSet.h" |
| #include "llvm/ADT/SmallSet.h" |
| #include "llvm/ADT/SmallVector.h" |
| #include "llvm/Analysis/LoopInfo.h" |
| #include "llvm/Analysis/OptimizationRemarkEmitter.h" |
| #include "llvm/Analysis/PostDominators.h" |
| #include "llvm/IR/BasicBlock.h" |
| #include "llvm/IR/CFG.h" |
| #include "llvm/IR/DebugInfoMetadata.h" |
| #include "llvm/IR/DebugLoc.h" |
| #include "llvm/IR/Dominators.h" |
| #include "llvm/IR/Function.h" |
| #include "llvm/IR/Instruction.h" |
| #include "llvm/IR/Instructions.h" |
| #include "llvm/IR/Module.h" |
| #include "llvm/ProfileData/SampleProf.h" |
| #include "llvm/ProfileData/SampleProfReader.h" |
| #include "llvm/Support/CommandLine.h" |
| #include "llvm/Support/GenericDomTree.h" |
| #include "llvm/Support/raw_ostream.h" |
| #include "llvm/Transforms/Utils/SampleProfileInference.h" |
| #include "llvm/Transforms/Utils/SampleProfileLoaderBaseUtil.h" |
| |
| namespace llvm { |
| using namespace sampleprof; |
| using namespace sampleprofutil; |
| using ProfileCount = Function::ProfileCount; |
| |
| #define DEBUG_TYPE "sample-profile-impl" |
| |
| namespace afdo_detail { |
| |
| template <typename BlockT> struct IRTraits; |
| template <> struct IRTraits<BasicBlock> { |
| using InstructionT = Instruction; |
| using BasicBlockT = BasicBlock; |
| using FunctionT = Function; |
| using BlockFrequencyInfoT = BlockFrequencyInfo; |
| using LoopT = Loop; |
| using LoopInfoPtrT = std::unique_ptr<LoopInfo>; |
| using DominatorTreePtrT = std::unique_ptr<DominatorTree>; |
| using PostDominatorTreeT = PostDominatorTree; |
| using PostDominatorTreePtrT = std::unique_ptr<PostDominatorTree>; |
| using OptRemarkEmitterT = OptimizationRemarkEmitter; |
| using OptRemarkAnalysisT = OptimizationRemarkAnalysis; |
| using PredRangeT = pred_range; |
| using SuccRangeT = succ_range; |
| static Function &getFunction(Function &F) { return F; } |
| static const BasicBlock *getEntryBB(const Function *F) { |
| return &F->getEntryBlock(); |
| } |
| static pred_range getPredecessors(BasicBlock *BB) { return predecessors(BB); } |
| static succ_range getSuccessors(BasicBlock *BB) { return successors(BB); } |
| }; |
| |
| } // end namespace afdo_detail |
| |
| extern cl::opt<bool> SampleProfileUseProfi; |
| |
| template <typename BT> class SampleProfileLoaderBaseImpl { |
| public: |
| SampleProfileLoaderBaseImpl(std::string Name, std::string RemapName) |
| : Filename(Name), RemappingFilename(RemapName) {} |
| void dump() { Reader->dump(); } |
| |
| using InstructionT = typename afdo_detail::IRTraits<BT>::InstructionT; |
| using BasicBlockT = typename afdo_detail::IRTraits<BT>::BasicBlockT; |
| using BlockFrequencyInfoT = |
| typename afdo_detail::IRTraits<BT>::BlockFrequencyInfoT; |
| using FunctionT = typename afdo_detail::IRTraits<BT>::FunctionT; |
| using LoopT = typename afdo_detail::IRTraits<BT>::LoopT; |
| using LoopInfoPtrT = typename afdo_detail::IRTraits<BT>::LoopInfoPtrT; |
| using DominatorTreePtrT = |
| typename afdo_detail::IRTraits<BT>::DominatorTreePtrT; |
| using PostDominatorTreePtrT = |
| typename afdo_detail::IRTraits<BT>::PostDominatorTreePtrT; |
| using PostDominatorTreeT = |
| typename afdo_detail::IRTraits<BT>::PostDominatorTreeT; |
| using OptRemarkEmitterT = |
| typename afdo_detail::IRTraits<BT>::OptRemarkEmitterT; |
| using OptRemarkAnalysisT = |
| typename afdo_detail::IRTraits<BT>::OptRemarkAnalysisT; |
| using PredRangeT = typename afdo_detail::IRTraits<BT>::PredRangeT; |
| using SuccRangeT = typename afdo_detail::IRTraits<BT>::SuccRangeT; |
| |
| using BlockWeightMap = DenseMap<const BasicBlockT *, uint64_t>; |
| using EquivalenceClassMap = |
| DenseMap<const BasicBlockT *, const BasicBlockT *>; |
| using Edge = std::pair<const BasicBlockT *, const BasicBlockT *>; |
| using EdgeWeightMap = DenseMap<Edge, uint64_t>; |
| using BlockEdgeMap = |
| DenseMap<const BasicBlockT *, SmallVector<const BasicBlockT *, 8>>; |
| |
| protected: |
| ~SampleProfileLoaderBaseImpl() = default; |
| friend class SampleCoverageTracker; |
| |
| Function &getFunction(FunctionT &F) { |
| return afdo_detail::IRTraits<BT>::getFunction(F); |
| } |
| const BasicBlockT *getEntryBB(const FunctionT *F) { |
| return afdo_detail::IRTraits<BT>::getEntryBB(F); |
| } |
| PredRangeT getPredecessors(BasicBlockT *BB) { |
| return afdo_detail::IRTraits<BT>::getPredecessors(BB); |
| } |
| SuccRangeT getSuccessors(BasicBlockT *BB) { |
| return afdo_detail::IRTraits<BT>::getSuccessors(BB); |
| } |
| |
| unsigned getFunctionLoc(FunctionT &Func); |
| virtual ErrorOr<uint64_t> getInstWeight(const InstructionT &Inst); |
| ErrorOr<uint64_t> getInstWeightImpl(const InstructionT &Inst); |
| ErrorOr<uint64_t> getBlockWeight(const BasicBlockT *BB); |
| mutable DenseMap<const DILocation *, const FunctionSamples *> |
| DILocation2SampleMap; |
| virtual const FunctionSamples * |
| findFunctionSamples(const InstructionT &I) const; |
| void printEdgeWeight(raw_ostream &OS, Edge E); |
| void printBlockWeight(raw_ostream &OS, const BasicBlockT *BB) const; |
| void printBlockEquivalence(raw_ostream &OS, const BasicBlockT *BB); |
| bool computeBlockWeights(FunctionT &F); |
| void findEquivalenceClasses(FunctionT &F); |
| void findEquivalencesFor(BasicBlockT *BB1, |
| ArrayRef<BasicBlockT *> Descendants, |
| PostDominatorTreeT *DomTree); |
| void propagateWeights(FunctionT &F); |
| void applyProfi(FunctionT &F, BlockEdgeMap &Successors, |
| BlockWeightMap &SampleBlockWeights, |
| BlockWeightMap &BlockWeights, EdgeWeightMap &EdgeWeights); |
| uint64_t visitEdge(Edge E, unsigned *NumUnknownEdges, Edge *UnknownEdge); |
| void buildEdges(FunctionT &F); |
| bool propagateThroughEdges(FunctionT &F, bool UpdateBlockCount); |
| void clearFunctionData(bool ResetDT = true); |
| void computeDominanceAndLoopInfo(FunctionT &F); |
| bool |
| computeAndPropagateWeights(FunctionT &F, |
| const DenseSet<GlobalValue::GUID> &InlinedGUIDs); |
| void initWeightPropagation(FunctionT &F, |
| const DenseSet<GlobalValue::GUID> &InlinedGUIDs); |
| void |
| finalizeWeightPropagation(FunctionT &F, |
| const DenseSet<GlobalValue::GUID> &InlinedGUIDs); |
| void emitCoverageRemarks(FunctionT &F); |
| |
| /// 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 BasicBlockT *, 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; |
| |
| /// Dominance, post-dominance and loop information. |
| DominatorTreePtrT DT; |
| PostDominatorTreePtrT PDT; |
| LoopInfoPtrT LI; |
| |
| /// Predecessors for each basic block in the CFG. |
| BlockEdgeMap Predecessors; |
| |
| /// Successors for each basic block in the CFG. |
| BlockEdgeMap Successors; |
| |
| /// Profile coverage tracker. |
| 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; |
| |
| /// Profile Summary Info computed from sample profile. |
| ProfileSummaryInfo *PSI = nullptr; |
| |
| /// Optimization Remark Emitter used to emit diagnostic remarks. |
| OptRemarkEmitterT *ORE = nullptr; |
| }; |
| |
| /// Clear all the per-function data used to load samples and propagate weights. |
| template <typename BT> |
| void SampleProfileLoaderBaseImpl<BT>::clearFunctionData(bool ResetDT) { |
| BlockWeights.clear(); |
| EdgeWeights.clear(); |
| VisitedBlocks.clear(); |
| VisitedEdges.clear(); |
| EquivalenceClass.clear(); |
| if (ResetDT) { |
| 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. |
| template <typename BT> |
| void SampleProfileLoaderBaseImpl<BT>::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. |
| template <typename BT> |
| void SampleProfileLoaderBaseImpl<BT>::printBlockEquivalence( |
| raw_ostream &OS, const BasicBlockT *BB) { |
| const BasicBlockT *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. |
| template <typename BT> |
| void SampleProfileLoaderBaseImpl<BT>::printBlockWeight( |
| raw_ostream &OS, const BasicBlockT *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. |
| template <typename BT> |
| ErrorOr<uint64_t> |
| SampleProfileLoaderBaseImpl<BT>::getInstWeight(const InstructionT &Inst) { |
| return getInstWeightImpl(Inst); |
| } |
| |
| template <typename BT> |
| ErrorOr<uint64_t> |
| SampleProfileLoaderBaseImpl<BT>::getInstWeightImpl(const InstructionT &Inst) { |
| const FunctionSamples *FS = findFunctionSamples(Inst); |
| if (!FS) |
| return std::error_code(); |
| |
| const DebugLoc &DLoc = Inst.getDebugLoc(); |
| if (!DLoc) |
| return std::error_code(); |
| |
| const DILocation *DIL = DLoc; |
| uint32_t LineOffset = FunctionSamples::getOffset(DIL); |
| uint32_t Discriminator; |
| if (EnableFSDiscriminator) |
| Discriminator = DIL->getDiscriminator(); |
| else |
| 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([&]() { |
| OptRemarkAnalysisT 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() << "." << Discriminator << ":" |
| << Inst << " (line offset: " << LineOffset << "." |
| << Discriminator << " - 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. |
| template <typename BT> |
| ErrorOr<uint64_t> |
| SampleProfileLoaderBaseImpl<BT>::getBlockWeight(const BasicBlockT *BB) { |
| uint64_t Max = 0; |
| bool HasWeight = false; |
| for (auto &I : *BB) { |
| 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. |
| template <typename BT> |
| bool SampleProfileLoaderBaseImpl<BT>::computeBlockWeights(FunctionT &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 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. |
| template <typename BT> |
| const FunctionSamples *SampleProfileLoaderBaseImpl<BT>::findFunctionSamples( |
| const InstructionT &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, Reader->getRemapper()); |
| } |
| return it.first->second; |
| } |
| |
| /// 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 <typename BT> |
| void SampleProfileLoaderBaseImpl<BT>::findEquivalencesFor( |
| BasicBlockT *BB1, ArrayRef<BasicBlockT *> Descendants, |
| PostDominatorTreeT *DomTree) { |
| const BasicBlockT *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]); |
| } |
| } |
| const BasicBlockT *EntryBB = getEntryBB(EC->getParent()); |
| if (EC == EntryBB) { |
| 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. |
| template <typename BT> |
| void SampleProfileLoaderBaseImpl<BT>::findEquivalenceClasses(FunctionT &F) { |
| SmallVector<BasicBlockT *, 8> DominatedBBs; |
| LLVM_DEBUG(dbgs() << "\nBlock equivalence classes\n"); |
| // Find equivalence sets based on dominance and post-dominance information. |
| for (auto &BB : F) { |
| BasicBlockT *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); |
| |
| 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 BasicBlockT *BB = &BI; |
| const BasicBlockT *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. |
| template <typename BT> |
| uint64_t SampleProfileLoaderBaseImpl<BT>::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. |
| template <typename BT> |
| bool SampleProfileLoaderBaseImpl<BT>::propagateThroughEdges( |
| FunctionT &F, bool UpdateBlockCount) { |
| bool Changed = false; |
| LLVM_DEBUG(dbgs() << "\nPropagation through edges\n"); |
| for (const auto &BI : F) { |
| const BasicBlockT *BB = &BI; |
| const BasicBlockT *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 BasicBlockT *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. |
| template <typename BT> |
| void SampleProfileLoaderBaseImpl<BT>::buildEdges(FunctionT &F) { |
| for (auto &BI : F) { |
| BasicBlockT *B1 = &BI; |
| |
| // Add predecessors for B1. |
| SmallPtrSet<BasicBlockT *, 16> Visited; |
| if (!Predecessors[B1].empty()) |
| llvm_unreachable("Found a stale predecessors list in a basic block."); |
| for (auto *B2 : getPredecessors(B1)) |
| 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 (auto *B2 : getSuccessors(B1)) |
| if (Visited.insert(B2).second) |
| Successors[B1].push_back(B2); |
| } |
| } |
| |
| /// 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). |
| template <typename BT> |
| void SampleProfileLoaderBaseImpl<BT>::propagateWeights(FunctionT &F) { |
| // Flow-based profile inference is only usable with BasicBlock instantiation |
| // of SampleProfileLoaderBaseImpl. |
| if (SampleProfileUseProfi) { |
| // Prepare block sample counts for inference. |
| BlockWeightMap SampleBlockWeights; |
| for (const auto &BI : F) { |
| ErrorOr<uint64_t> Weight = getBlockWeight(&BI); |
| if (Weight) |
| SampleBlockWeights[&BI] = Weight.get(); |
| } |
| // Fill in BlockWeights and EdgeWeights using an inference algorithm. |
| applyProfi(F, Successors, SampleBlockWeights, BlockWeights, EdgeWeights); |
| } else { |
| 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) { |
| BasicBlockT *BB = &BI; |
| LoopT *L = LI->getLoopFor(BB); |
| if (!L) { |
| continue; |
| } |
| BasicBlockT *Header = L->getHeader(); |
| if (Header && BlockWeights[BB] > BlockWeights[Header]) { |
| BlockWeights[Header] = BlockWeights[BB]; |
| } |
| } |
| |
| // 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); |
| } |
| } |
| } |
| |
| template <typename BT> |
| void SampleProfileLoaderBaseImpl<BT>::applyProfi( |
| FunctionT &F, BlockEdgeMap &Successors, BlockWeightMap &SampleBlockWeights, |
| BlockWeightMap &BlockWeights, EdgeWeightMap &EdgeWeights) { |
| auto Infer = SampleProfileInference<BT>(F, Successors, SampleBlockWeights); |
| Infer.apply(BlockWeights, EdgeWeights); |
| } |
| |
| /// 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. |
| /// |
| /// \param F The function to query. |
| /// |
| /// \returns true if \p F was modified. Returns false, otherwise. |
| template <typename BT> |
| bool SampleProfileLoaderBaseImpl<BT>::computeAndPropagateWeights( |
| FunctionT &F, const DenseSet<GlobalValue::GUID> &InlinedGUIDs) { |
| bool Changed = (InlinedGUIDs.size() != 0); |
| |
| // Compute basic block weights. |
| Changed |= computeBlockWeights(F); |
| |
| if (Changed) { |
| // Initialize propagation. |
| initWeightPropagation(F, InlinedGUIDs); |
| |
| // Propagate weights to all edges. |
| propagateWeights(F); |
| |
| // Post-process propagated weights. |
| finalizeWeightPropagation(F, InlinedGUIDs); |
| } |
| |
| return Changed; |
| } |
| |
| template <typename BT> |
| void SampleProfileLoaderBaseImpl<BT>::initWeightPropagation( |
| FunctionT &F, const DenseSet<GlobalValue::GUID> &InlinedGUIDs) { |
| // 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. |
| getFunction(F).setEntryCount( |
| ProfileCount(Samples->getHeadSamples() + 1, Function::PCT_Real), |
| &InlinedGUIDs); |
| |
| if (!SampleProfileUseProfi) { |
| // Compute dominance and loop info needed for propagation. |
| computeDominanceAndLoopInfo(F); |
| |
| // Find equivalence classes. |
| findEquivalenceClasses(F); |
| } |
| |
| // 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); |
| } |
| |
| template <typename BT> |
| void SampleProfileLoaderBaseImpl<BT>::finalizeWeightPropagation( |
| FunctionT &F, const DenseSet<GlobalValue::GUID> &InlinedGUIDs) { |
| // If we utilize a flow-based count inference, then we trust the computed |
| // counts and set the entry count as computed by the algorithm. This is |
| // primarily done to sync the counts produced by profi and BFI inference, |
| // which uses the entry count for mass propagation. |
| // If profi produces a zero-value for the entry count, we fallback to |
| // Samples->getHeadSamples() + 1 to avoid functions with zero count. |
| if (SampleProfileUseProfi) { |
| const BasicBlockT *EntryBB = getEntryBB(&F); |
| if (BlockWeights[EntryBB] > 0) { |
| getFunction(F).setEntryCount( |
| ProfileCount(BlockWeights[EntryBB], Function::PCT_Real), |
| &InlinedGUIDs); |
| } |
| } |
| } |
| |
| template <typename BT> |
| void SampleProfileLoaderBaseImpl<BT>::emitCoverageRemarks(FunctionT &F) { |
| // If coverage checking was requested, compute it now. |
| const Function &Func = getFunction(F); |
| if (SampleProfileRecordCoverage) { |
| unsigned Used = CoverageTracker.countUsedRecords(Samples, PSI); |
| unsigned Total = CoverageTracker.countBodyRecords(Samples, PSI); |
| unsigned Coverage = CoverageTracker.computeCoverage(Used, Total); |
| if (Coverage < SampleProfileRecordCoverage) { |
| Func.getContext().diagnose(DiagnosticInfoSampleProfile( |
| Func.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) { |
| Func.getContext().diagnose(DiagnosticInfoSampleProfile( |
| Func.getSubprogram()->getFilename(), getFunctionLoc(F), |
| Twine(Used) + " of " + Twine(Total) + " available profile samples (" + |
| Twine(Coverage) + "%) were applied", |
| DS_Warning)); |
| } |
| } |
| } |
| |
| /// 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. |
| template <typename BT> |
| unsigned SampleProfileLoaderBaseImpl<BT>::getFunctionLoc(FunctionT &F) { |
| const Function &Func = getFunction(F); |
| if (DISubprogram *S = Func.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. |
| Func.getContext().diagnose(DiagnosticInfoSampleProfile( |
| "No debug information found in function " + Func.getName() + |
| ": Function profile not used", |
| DS_Warning)); |
| return 0; |
| } |
| |
| template <typename BT> |
| void SampleProfileLoaderBaseImpl<BT>::computeDominanceAndLoopInfo( |
| FunctionT &F) { |
| DT.reset(new DominatorTree); |
| DT->recalculate(F); |
| |
| PDT.reset(new PostDominatorTree(F)); |
| |
| LI.reset(new LoopInfo); |
| LI->analyze(*DT); |
| } |
| |
| #undef DEBUG_TYPE |
| |
| } // namespace llvm |
| #endif // LLVM_TRANSFORMS_UTILS_SAMPLEPROFILELOADERBASEIMPL_H |