Successfully identified regression in *llvm* in CI configuration tcwg_bmk_llvm_tk1/llvm-release-arm-spec2k6-O3_LTO. So far, this commit has regressed CI configurations: - tcwg_bmk_llvm_tk1/llvm-release-arm-spec2k6-O3_LTO

Culprit: <cut> commit 310b35304cdf5a230c042904655583c5532d3e91 Author: Rong Xu xur@google.com Date: Tue Feb 16 10:53:38 2021 -0800

[SampleFDO][NFC] Refactor SampleProfile.cpp

Refactor SampleProfile.cpp to use the core code in CodeGen. The main changes are: (1) Move SampleProfileLoaderBaseImpl class to a header file. (2) Split SampleCoverageTracker to a head file and a cpp file. (3) Move the common codes (common options and callsiteIsHot()) to the common cpp file.

Differential Revision: https://reviews.llvm.org/D96455 </cut>

Results regressed to (for first_bad == 310b35304cdf5a230c042904655583c5532d3e91) # reset_artifacts: -10 # build_abe binutils: -9 # build_abe stage1 -- --set gcc_override_configure=--with-mode=arm --set gcc_override_configure=--disable-libsanitizer: -8 # build_abe linux: -7 # build_abe glibc: -6 # build_abe stage2 -- --set gcc_override_configure=--with-mode=arm --set gcc_override_configure=--disable-libsanitizer: -5 # build_llvm true: -3 # true: 0 # benchmark -- -O3_LTO_marm artifacts/build-310b35304cdf5a230c042904655583c5532d3e91/results_id: 1 # 482.sphinx3,sphinx_livepretend_base.default regressed by 106

from (for last_good == cddc53ef088b68586094c9841a76b41bee3994a4) # reset_artifacts: -10 # build_abe binutils: -9 # build_abe stage1 -- --set gcc_override_configure=--with-mode=arm --set gcc_override_configure=--disable-libsanitizer: -8 # build_abe linux: -7 # build_abe glibc: -6 # build_abe stage2 -- --set gcc_override_configure=--with-mode=arm --set gcc_override_configure=--disable-libsanitizer: -5 # build_llvm true: -3 # true: 0 # benchmark -- -O3_LTO_marm artifacts/build-cddc53ef088b68586094c9841a76b41bee3994a4/results_id: 1

Artifacts of last_good build: https://ci.linaro.org/job/tcwg_bmk_ci_llvm-bisect-tcwg_bmk_tk1-llvm-release-... Results ID of last_good: tk1_32/tcwg_bmk_llvm_tk1/bisect-llvm-release-arm-spec2k6-O3_LTO/3917 Artifacts of first_bad build: https://ci.linaro.org/job/tcwg_bmk_ci_llvm-bisect-tcwg_bmk_tk1-llvm-release-... Results ID of first_bad: tk1_32/tcwg_bmk_llvm_tk1/bisect-llvm-release-arm-spec2k6-O3_LTO/3930 Build top page/logs: https://ci.linaro.org/job/tcwg_bmk_ci_llvm-bisect-tcwg_bmk_tk1-llvm-release-...

Configuration details:

Reproduce builds: <cut> mkdir investigate-llvm-310b35304cdf5a230c042904655583c5532d3e91 cd investigate-llvm-310b35304cdf5a230c042904655583c5532d3e91

git clone https://git.linaro.org/toolchain/jenkins-scripts

mkdir -p artifacts/manifests curl -o artifacts/manifests/build-baseline.sh https://ci.linaro.org/job/tcwg_bmk_ci_llvm-bisect-tcwg_bmk_tk1-llvm-release-... --fail curl -o artifacts/manifests/build-parameters.sh https://ci.linaro.org/job/tcwg_bmk_ci_llvm-bisect-tcwg_bmk_tk1-llvm-release-... --fail curl -o artifacts/test.sh https://ci.linaro.org/job/tcwg_bmk_ci_llvm-bisect-tcwg_bmk_tk1-llvm-release-... --fail chmod +x artifacts/test.sh

# Reproduce the baseline build (build all pre-requisites) ./jenkins-scripts/tcwg_bmk-build.sh @@ artifacts/manifests/build-baseline.sh

# Save baseline build state (which is then restored in artifacts/test.sh) mkdir -p ./bisect rsync -a --del --delete-excluded --exclude /bisect/ --exclude /artifacts/ --exclude /llvm/ ./ ./bisect/baseline/

cd llvm

# Reproduce first_bad build git checkout --detach 310b35304cdf5a230c042904655583c5532d3e91 ../artifacts/test.sh

# Reproduce last_good build git checkout --detach cddc53ef088b68586094c9841a76b41bee3994a4 ../artifacts/test.sh

cd .. </cut>

History of pending regressions and results: https://git.linaro.org/toolchain/ci/base-artifacts.git/log/?h=linaro-local/c...

Artifacts: https://ci.linaro.org/job/tcwg_bmk_ci_llvm-bisect-tcwg_bmk_tk1-llvm-release-... Build log: https://ci.linaro.org/job/tcwg_bmk_ci_llvm-bisect-tcwg_bmk_tk1-llvm-release-...

Full commit (up to 1000 lines): <cut> commit 310b35304cdf5a230c042904655583c5532d3e91 Author: Rong Xu xur@google.com Date: Tue Feb 16 10:53:38 2021 -0800

[SampleFDO][NFC] Refactor SampleProfile.cpp

Refactor SampleProfile.cpp to use the core code in CodeGen. The main changes are: (1) Move SampleProfileLoaderBaseImpl class to a header file. (2) Split SampleCoverageTracker to a head file and a cpp file. (3) Move the common codes (common options and callsiteIsHot()) to the common cpp file.

Differential Revision: https://reviews.llvm.org/D96455 --- .../llvm/ProfileData/SampleProfileLoaderBaseImpl.h | 862 +++++++++++++++++ .../llvm/ProfileData/SampleProfileLoaderBaseUtil.h | 97 ++ llvm/lib/ProfileData/CMakeLists.txt | 1 + .../ProfileData/SampleProfileLoaderBaseUtil.cpp | 192 ++++ llvm/lib/Transforms/IPO/SampleProfile.cpp | 1001 +------------------- 5 files changed, 1161 insertions(+), 992 deletions(-)

diff --git a/llvm/include/llvm/ProfileData/SampleProfileLoaderBaseImpl.h b/llvm/include/llvm/ProfileData/SampleProfileLoaderBaseImpl.h new file mode 100644 index 000000000000..f02bacb6edc3 --- /dev/null +++ b/llvm/include/llvm/ProfileData/SampleProfileLoaderBaseImpl.h @@ -0,0 +1,862 @@ +////===- 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_IPO_SAMPLEPROFILELOADERIMPL_H +#define LLVM_TRANSFORMS_IPO_SAMPLEPROFILELOADERIMPL_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/Analysis/ProfileSummaryInfo.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/ProfileData/SampleProfileLoaderBaseUtil.h" +#include "llvm/Support/CommandLine.h" +#include "llvm/Support/GenericDomTree.h" +#include "llvm/Support/raw_ostream.h" + +namespace llvm { +using namespace llvm; +using namespace sampleprof; +using ProfileCount = Function::ProfileCount; +namespace sampleprofutil { +bool callsiteIsHot(const SampleCoverageTracker *CT, + const FunctionSamples *CallsiteFS, ProfileSummaryInfo *PSI, + bool ProfAccForSymsInList); +} // namespace sampleprofutil +using namespace sampleprofutil; + +#define DEBUG_TYPE "sample-profile-impl" + +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>>; + +extern cl::opt<unsigned> SampleProfileMaxPropagateIterations; +extern cl::opt<unsigned> SampleProfileRecordCoverage; +extern cl::opt<unsigned> SampleProfileSampleCoverage; +extern cl::opt<bool> NoWarnSampleUnused; + +class SampleProfileLoaderBaseImpl { +public: + SampleProfileLoaderBaseImpl(std::string Name) : Filename(Name) {} + void dump() { Reader->dump(); } + +protected: + friend class SampleCoverageTracker; + + unsigned getFunctionLoc(Function &F); + virtual ErrorOr<uint64_t> getInstWeight(const Instruction &Inst); + ErrorOr<uint64_t> getInstWeightImpl(const Instruction &Inst); + ErrorOr<uint64_t> getBlockWeight(const BasicBlock *BB); + mutable DenseMap<const DILocation *, const FunctionSamples *> + DILocation2SampleMap; + virtual const FunctionSamples * + findFunctionSamples(const Instruction &I) const; + 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 clearFunctionData(); + void computeDominanceAndLoopInfo(Function &F); + bool + computeAndPropagateWeights(Function &F, + const DenseSetGlobalValue::GUID &InlinedGUIDs); + void emitCoverageRemarks(Function &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 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; + + /// Dominance, post-dominance and loop information. + std::unique_ptr<DominatorTree> DT; + std::unique_ptr<PostDominatorTree> PDT; + std::unique_ptr<LoopInfo> 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; + + /// Profile Summary Info computed from sample profile. + ProfileSummaryInfo *PSI = nullptr; + + /// Optimization Remark Emitter used to emit diagnostic remarks. + OptimizationRemarkEmitter *ORE = nullptr; +}; + +/// Clear all the per-function data used to load samples and propagate weights. +void SampleProfileLoaderBaseImpl::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 SampleProfileLoaderBaseImpl::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 SampleProfileLoaderBaseImpl::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 SampleProfileLoaderBaseImpl::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> +SampleProfileLoaderBaseImpl::getInstWeight(const Instruction &Inst) { + return getInstWeightImpl(Inst); +} + +ErrorOr<uint64_t> +SampleProfileLoaderBaseImpl::getInstWeightImpl(const Instruction &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 = 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> +SampleProfileLoaderBaseImpl::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 SampleProfileLoaderBaseImpl::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 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 *SampleProfileLoaderBaseImpl::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, 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 <bool IsPostDom> +void SampleProfileLoaderBaseImpl::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 SampleProfileLoaderBaseImpl::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 SampleProfileLoaderBaseImpl::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 SampleProfileLoaderBaseImpl::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 SampleProfileLoaderBaseImpl::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 (BasicBlock *B2 : predecessors(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 (BasicBlock *B2 : successors(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). +void SampleProfileLoaderBaseImpl::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 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. +bool SampleProfileLoaderBaseImpl::computeAndPropagateWeights( + Function &F, const DenseSetGlobalValue::GUID &InlinedGUIDs) { + bool Changed = (InlinedGUIDs.size() != 0); + + // 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); + } + + return Changed; +} + +void SampleProfileLoaderBaseImpl::emitCoverageRemarks(Function &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)); + } + } +} + +/// 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 SampleProfileLoaderBaseImpl::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 SampleProfileLoaderBaseImpl::computeDominanceAndLoopInfo(Function &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_IPO_SAMPLEPROFILELOADERIMPL_H diff --git a/llvm/include/llvm/ProfileData/SampleProfileLoaderBaseUtil.h b/llvm/include/llvm/ProfileData/SampleProfileLoaderBaseUtil.h new file mode 100644 index 000000000000..37dc8d8187d9 --- /dev/null +++ b/llvm/include/llvm/ProfileData/SampleProfileLoaderBaseUtil.h @@ -0,0 +1,97 @@ +////===- SampleProfileLoadBaseUtil.h - Profile loader util func --*- 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 utility functions for the sampled PGO loader base +/// implementation. +// +//===----------------------------------------------------------------------===// + +#ifndef LLVM_TRANSFORMS_IPO_SAMPLEPROFILELOADERUTIL_H +#define LLVM_TRANSFORMS_IPO_SAMPLEPROFILELOADERUTIL_H + +#include "llvm/ADT/DenseMap.h" +#include "llvm/Analysis/ProfileSummaryInfo.h" +#include "llvm/IR/BasicBlock.h" +#include "llvm/IR/CFG.h" +#include "llvm/IR/DebugLoc.h" +#include "llvm/IR/Function.h" +#include "llvm/ProfileData/SampleProf.h" +#include "llvm/Support/CommandLine.h" + +namespace llvm { +using namespace sampleprof; + +extern cl::opt<unsigned> SampleProfileMaxPropagateIterations; +extern cl::opt<unsigned> SampleProfileRecordCoverage; +extern cl::opt<unsigned> SampleProfileSampleCoverage; +extern cl::opt<bool> NoWarnSampleUnused; + +namespace sampleprofutil { + +class SampleCoverageTracker { +public: + 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; + } + void setProfAccForSymsInList(bool V) { ProfAccForSymsInList = V; } + +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; + + // For symbol in profile symbol list, whether to regard their profiles + // to be accurate. This is passed from the SampleLoader instance. + bool ProfAccForSymsInList = false; +}; + +/// Return true if the given callsite is hot wrt to hot cutoff threshold. +bool callsiteIsHot(const FunctionSamples *CallsiteFS, ProfileSummaryInfo *PSI, + bool ProfAccForSymsInList); + +} // end of namespace sampleprofutil +} // end of namespace llvm + +#endif // LLVM_TRANSFORMS_IPO_SAMPLEPROFILELOADERUTIL_H diff --git a/llvm/lib/ProfileData/CMakeLists.txt b/llvm/lib/ProfileData/CMakeLists.txt index 2a377e4d74d3..4125fac918ab 100644 --- a/llvm/lib/ProfileData/CMakeLists.txt +++ b/llvm/lib/ProfileData/CMakeLists.txt @@ -5,6 +5,7 @@ add_llvm_component_library(LLVMProfileData InstrProfWriter.cpp ProfileSummaryBuilder.cpp </cut>