1 //===- SampleProfile.cpp - Incorporate sample profiles into the IR --------===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 // 10 // This file implements the SampleProfileLoader transformation. This pass 11 // reads a profile file generated by a sampling profiler (e.g. Linux Perf - 12 // http://perf.wiki.kernel.org/) and generates IR metadata to reflect the 13 // profile information in the given profile. 14 // 15 // This pass generates branch weight annotations on the IR: 16 // 17 // - prof: Represents branch weights. This annotation is added to branches 18 // to indicate the weights of each edge coming out of the branch. 19 // The weight of each edge is the weight of the target block for 20 // that edge. The weight of a block B is computed as the maximum 21 // number of samples found in B. 22 // 23 //===----------------------------------------------------------------------===// 24 25 #include "llvm/Transforms/IPO/SampleProfile.h" 26 #include "llvm/ADT/ArrayRef.h" 27 #include "llvm/ADT/DenseMap.h" 28 #include "llvm/ADT/DenseSet.h" 29 #include "llvm/ADT/None.h" 30 #include "llvm/ADT/SmallPtrSet.h" 31 #include "llvm/ADT/SmallSet.h" 32 #include "llvm/ADT/SmallVector.h" 33 #include "llvm/ADT/StringMap.h" 34 #include "llvm/ADT/StringRef.h" 35 #include "llvm/ADT/Twine.h" 36 #include "llvm/Analysis/AssumptionCache.h" 37 #include "llvm/Analysis/InlineCost.h" 38 #include "llvm/Analysis/LoopInfo.h" 39 #include "llvm/Analysis/OptimizationRemarkEmitter.h" 40 #include "llvm/Analysis/PostDominators.h" 41 #include "llvm/Analysis/ProfileSummaryInfo.h" 42 #include "llvm/Analysis/TargetTransformInfo.h" 43 #include "llvm/IR/BasicBlock.h" 44 #include "llvm/IR/CFG.h" 45 #include "llvm/IR/CallSite.h" 46 #include "llvm/IR/DebugInfoMetadata.h" 47 #include "llvm/IR/DebugLoc.h" 48 #include "llvm/IR/DiagnosticInfo.h" 49 #include "llvm/IR/Dominators.h" 50 #include "llvm/IR/Function.h" 51 #include "llvm/IR/GlobalValue.h" 52 #include "llvm/IR/InstrTypes.h" 53 #include "llvm/IR/Instruction.h" 54 #include "llvm/IR/Instructions.h" 55 #include "llvm/IR/IntrinsicInst.h" 56 #include "llvm/IR/LLVMContext.h" 57 #include "llvm/IR/MDBuilder.h" 58 #include "llvm/IR/Module.h" 59 #include "llvm/IR/PassManager.h" 60 #include "llvm/IR/ValueSymbolTable.h" 61 #include "llvm/Pass.h" 62 #include "llvm/ProfileData/InstrProf.h" 63 #include "llvm/ProfileData/SampleProf.h" 64 #include "llvm/ProfileData/SampleProfReader.h" 65 #include "llvm/Support/Casting.h" 66 #include "llvm/Support/CommandLine.h" 67 #include "llvm/Support/Debug.h" 68 #include "llvm/Support/ErrorHandling.h" 69 #include "llvm/Support/ErrorOr.h" 70 #include "llvm/Support/GenericDomTree.h" 71 #include "llvm/Support/raw_ostream.h" 72 #include "llvm/Transforms/IPO.h" 73 #include "llvm/Transforms/Instrumentation.h" 74 #include "llvm/Transforms/Utils/CallPromotionUtils.h" 75 #include "llvm/Transforms/Utils/Cloning.h" 76 #include <algorithm> 77 #include <cassert> 78 #include <cstdint> 79 #include <functional> 80 #include <limits> 81 #include <map> 82 #include <memory> 83 #include <string> 84 #include <system_error> 85 #include <utility> 86 #include <vector> 87 88 using namespace llvm; 89 using namespace sampleprof; 90 using ProfileCount = Function::ProfileCount; 91 #define DEBUG_TYPE "sample-profile" 92 93 // Command line option to specify the file to read samples from. This is 94 // mainly used for debugging. 95 static cl::opt<std::string> SampleProfileFile( 96 "sample-profile-file", cl::init(""), cl::value_desc("filename"), 97 cl::desc("Profile file loaded by -sample-profile"), cl::Hidden); 98 99 static cl::opt<unsigned> SampleProfileMaxPropagateIterations( 100 "sample-profile-max-propagate-iterations", cl::init(100), 101 cl::desc("Maximum number of iterations to go through when propagating " 102 "sample block/edge weights through the CFG.")); 103 104 static cl::opt<unsigned> SampleProfileRecordCoverage( 105 "sample-profile-check-record-coverage", cl::init(0), cl::value_desc("N"), 106 cl::desc("Emit a warning if less than N% of records in the input profile " 107 "are matched to the IR.")); 108 109 static cl::opt<unsigned> SampleProfileSampleCoverage( 110 "sample-profile-check-sample-coverage", cl::init(0), cl::value_desc("N"), 111 cl::desc("Emit a warning if less than N% of samples in the input profile " 112 "are matched to the IR.")); 113 114 static cl::opt<bool> NoWarnSampleUnused( 115 "no-warn-sample-unused", cl::init(false), cl::Hidden, 116 cl::desc("Use this option to turn off/on warnings about function with " 117 "samples but without debug information to use those samples. ")); 118 119 namespace { 120 121 using BlockWeightMap = DenseMap<const BasicBlock *, uint64_t>; 122 using EquivalenceClassMap = DenseMap<const BasicBlock *, const BasicBlock *>; 123 using Edge = std::pair<const BasicBlock *, const BasicBlock *>; 124 using EdgeWeightMap = DenseMap<Edge, uint64_t>; 125 using BlockEdgeMap = 126 DenseMap<const BasicBlock *, SmallVector<const BasicBlock *, 8>>; 127 128 class SampleCoverageTracker { 129 public: 130 SampleCoverageTracker() = default; 131 132 bool markSamplesUsed(const FunctionSamples *FS, uint32_t LineOffset, 133 uint32_t Discriminator, uint64_t Samples); 134 unsigned computeCoverage(unsigned Used, unsigned Total) const; 135 unsigned countUsedRecords(const FunctionSamples *FS, 136 ProfileSummaryInfo *PSI) const; 137 unsigned countBodyRecords(const FunctionSamples *FS, 138 ProfileSummaryInfo *PSI) const; 139 uint64_t getTotalUsedSamples() const { return TotalUsedSamples; } 140 uint64_t countBodySamples(const FunctionSamples *FS, 141 ProfileSummaryInfo *PSI) const; 142 143 void clear() { 144 SampleCoverage.clear(); 145 TotalUsedSamples = 0; 146 } 147 148 private: 149 using BodySampleCoverageMap = std::map<LineLocation, unsigned>; 150 using FunctionSamplesCoverageMap = 151 DenseMap<const FunctionSamples *, BodySampleCoverageMap>; 152 153 /// Coverage map for sampling records. 154 /// 155 /// This map keeps a record of sampling records that have been matched to 156 /// an IR instruction. This is used to detect some form of staleness in 157 /// profiles (see flag -sample-profile-check-coverage). 158 /// 159 /// Each entry in the map corresponds to a FunctionSamples instance. This is 160 /// another map that counts how many times the sample record at the 161 /// given location has been used. 162 FunctionSamplesCoverageMap SampleCoverage; 163 164 /// Number of samples used from the profile. 165 /// 166 /// When a sampling record is used for the first time, the samples from 167 /// that record are added to this accumulator. Coverage is later computed 168 /// based on the total number of samples available in this function and 169 /// its callsites. 170 /// 171 /// Note that this accumulator tracks samples used from a single function 172 /// and all the inlined callsites. Strictly, we should have a map of counters 173 /// keyed by FunctionSamples pointers, but these stats are cleared after 174 /// every function, so we just need to keep a single counter. 175 uint64_t TotalUsedSamples = 0; 176 }; 177 178 /// Sample profile pass. 179 /// 180 /// This pass reads profile data from the file specified by 181 /// -sample-profile-file and annotates every affected function with the 182 /// profile information found in that file. 183 class SampleProfileLoader { 184 public: 185 SampleProfileLoader( 186 StringRef Name, bool IsThinLTOPreLink, 187 std::function<AssumptionCache &(Function &)> GetAssumptionCache, 188 std::function<TargetTransformInfo &(Function &)> GetTargetTransformInfo) 189 : GetAC(std::move(GetAssumptionCache)), 190 GetTTI(std::move(GetTargetTransformInfo)), Filename(Name), 191 IsThinLTOPreLink(IsThinLTOPreLink) {} 192 193 bool doInitialization(Module &M); 194 bool runOnModule(Module &M, ModuleAnalysisManager *AM, 195 ProfileSummaryInfo *_PSI); 196 197 void dump() { Reader->dump(); } 198 199 protected: 200 bool runOnFunction(Function &F, ModuleAnalysisManager *AM); 201 unsigned getFunctionLoc(Function &F); 202 bool emitAnnotations(Function &F); 203 ErrorOr<uint64_t> getInstWeight(const Instruction &I); 204 ErrorOr<uint64_t> getBlockWeight(const BasicBlock *BB); 205 const FunctionSamples *findCalleeFunctionSamples(const Instruction &I) const; 206 std::vector<const FunctionSamples *> 207 findIndirectCallFunctionSamples(const Instruction &I, uint64_t &Sum) const; 208 const FunctionSamples *findFunctionSamples(const Instruction &I) const; 209 bool inlineCallInstruction(Instruction *I); 210 bool inlineHotFunctions(Function &F, 211 DenseSet<GlobalValue::GUID> &InlinedGUIDs); 212 void printEdgeWeight(raw_ostream &OS, Edge E); 213 void printBlockWeight(raw_ostream &OS, const BasicBlock *BB) const; 214 void printBlockEquivalence(raw_ostream &OS, const BasicBlock *BB); 215 bool computeBlockWeights(Function &F); 216 void findEquivalenceClasses(Function &F); 217 template <bool IsPostDom> 218 void findEquivalencesFor(BasicBlock *BB1, ArrayRef<BasicBlock *> Descendants, 219 DominatorTreeBase<BasicBlock, IsPostDom> *DomTree); 220 221 void propagateWeights(Function &F); 222 uint64_t visitEdge(Edge E, unsigned *NumUnknownEdges, Edge *UnknownEdge); 223 void buildEdges(Function &F); 224 bool propagateThroughEdges(Function &F, bool UpdateBlockCount); 225 void computeDominanceAndLoopInfo(Function &F); 226 void clearFunctionData(); 227 228 /// Map basic blocks to their computed weights. 229 /// 230 /// The weight of a basic block is defined to be the maximum 231 /// of all the instruction weights in that block. 232 BlockWeightMap BlockWeights; 233 234 /// Map edges to their computed weights. 235 /// 236 /// Edge weights are computed by propagating basic block weights in 237 /// SampleProfile::propagateWeights. 238 EdgeWeightMap EdgeWeights; 239 240 /// Set of visited blocks during propagation. 241 SmallPtrSet<const BasicBlock *, 32> VisitedBlocks; 242 243 /// Set of visited edges during propagation. 244 SmallSet<Edge, 32> VisitedEdges; 245 246 /// Equivalence classes for block weights. 247 /// 248 /// Two blocks BB1 and BB2 are in the same equivalence class if they 249 /// dominate and post-dominate each other, and they are in the same loop 250 /// nest. When this happens, the two blocks are guaranteed to execute 251 /// the same number of times. 252 EquivalenceClassMap EquivalenceClass; 253 254 /// Map from function name to Function *. Used to find the function from 255 /// the function name. If the function name contains suffix, additional 256 /// entry is added to map from the stripped name to the function if there 257 /// is one-to-one mapping. 258 StringMap<Function *> SymbolMap; 259 260 /// Dominance, post-dominance and loop information. 261 std::unique_ptr<DominatorTree> DT; 262 std::unique_ptr<PostDominatorTree> PDT; 263 std::unique_ptr<LoopInfo> LI; 264 265 std::function<AssumptionCache &(Function &)> GetAC; 266 std::function<TargetTransformInfo &(Function &)> GetTTI; 267 268 /// Predecessors for each basic block in the CFG. 269 BlockEdgeMap Predecessors; 270 271 /// Successors for each basic block in the CFG. 272 BlockEdgeMap Successors; 273 274 SampleCoverageTracker CoverageTracker; 275 276 /// Profile reader object. 277 std::unique_ptr<SampleProfileReader> Reader; 278 279 /// Samples collected for the body of this function. 280 FunctionSamples *Samples = nullptr; 281 282 /// Name of the profile file to load. 283 std::string Filename; 284 285 /// Flag indicating whether the profile input loaded successfully. 286 bool ProfileIsValid = false; 287 288 /// Flag indicating if the pass is invoked in ThinLTO compile phase. 289 /// 290 /// In this phase, in annotation, we should not promote indirect calls. 291 /// Instead, we will mark GUIDs that needs to be annotated to the function. 292 bool IsThinLTOPreLink; 293 294 /// Profile Summary Info computed from sample profile. 295 ProfileSummaryInfo *PSI = nullptr; 296 297 /// Total number of samples collected in this profile. 298 /// 299 /// This is the sum of all the samples collected in all the functions executed 300 /// at runtime. 301 uint64_t TotalCollectedSamples = 0; 302 303 /// Optimization Remark Emitter used to emit diagnostic remarks. 304 OptimizationRemarkEmitter *ORE = nullptr; 305 }; 306 307 class SampleProfileLoaderLegacyPass : public ModulePass { 308 public: 309 // Class identification, replacement for typeinfo 310 static char ID; 311 312 SampleProfileLoaderLegacyPass(StringRef Name = SampleProfileFile, 313 bool IsThinLTOPreLink = false) 314 : ModulePass(ID), SampleLoader(Name, IsThinLTOPreLink, 315 [&](Function &F) -> AssumptionCache & { 316 return ACT->getAssumptionCache(F); 317 }, 318 [&](Function &F) -> TargetTransformInfo & { 319 return TTIWP->getTTI(F); 320 }) { 321 initializeSampleProfileLoaderLegacyPassPass( 322 *PassRegistry::getPassRegistry()); 323 } 324 325 void dump() { SampleLoader.dump(); } 326 327 bool doInitialization(Module &M) override { 328 return SampleLoader.doInitialization(M); 329 } 330 331 StringRef getPassName() const override { return "Sample profile pass"; } 332 bool runOnModule(Module &M) override; 333 334 void getAnalysisUsage(AnalysisUsage &AU) const override { 335 AU.addRequired<AssumptionCacheTracker>(); 336 AU.addRequired<TargetTransformInfoWrapperPass>(); 337 AU.addRequired<ProfileSummaryInfoWrapperPass>(); 338 } 339 340 private: 341 SampleProfileLoader SampleLoader; 342 AssumptionCacheTracker *ACT = nullptr; 343 TargetTransformInfoWrapperPass *TTIWP = nullptr; 344 }; 345 346 } // end anonymous namespace 347 348 /// Return true if the given callsite is hot wrt to hot cutoff threshold. 349 /// 350 /// Functions that were inlined in the original binary will be represented 351 /// in the inline stack in the sample profile. If the profile shows that 352 /// the original inline decision was "good" (i.e., the callsite is executed 353 /// frequently), then we will recreate the inline decision and apply the 354 /// profile from the inlined callsite. 355 /// 356 /// To decide whether an inlined callsite is hot, we compare the callsite 357 /// sample count with the hot cutoff computed by ProfileSummaryInfo, it is 358 /// regarded as hot if the count is above the cutoff value. 359 static bool callsiteIsHot(const FunctionSamples *CallsiteFS, 360 ProfileSummaryInfo *PSI) { 361 if (!CallsiteFS) 362 return false; // The callsite was not inlined in the original binary. 363 364 assert(PSI && "PSI is expected to be non null"); 365 uint64_t CallsiteTotalSamples = CallsiteFS->getTotalSamples(); 366 return PSI->isHotCount(CallsiteTotalSamples); 367 } 368 369 /// Mark as used the sample record for the given function samples at 370 /// (LineOffset, Discriminator). 371 /// 372 /// \returns true if this is the first time we mark the given record. 373 bool SampleCoverageTracker::markSamplesUsed(const FunctionSamples *FS, 374 uint32_t LineOffset, 375 uint32_t Discriminator, 376 uint64_t Samples) { 377 LineLocation Loc(LineOffset, Discriminator); 378 unsigned &Count = SampleCoverage[FS][Loc]; 379 bool FirstTime = (++Count == 1); 380 if (FirstTime) 381 TotalUsedSamples += Samples; 382 return FirstTime; 383 } 384 385 /// Return the number of sample records that were applied from this profile. 386 /// 387 /// This count does not include records from cold inlined callsites. 388 unsigned 389 SampleCoverageTracker::countUsedRecords(const FunctionSamples *FS, 390 ProfileSummaryInfo *PSI) const { 391 auto I = SampleCoverage.find(FS); 392 393 // The size of the coverage map for FS represents the number of records 394 // that were marked used at least once. 395 unsigned Count = (I != SampleCoverage.end()) ? I->second.size() : 0; 396 397 // If there are inlined callsites in this function, count the samples found 398 // in the respective bodies. However, do not bother counting callees with 0 399 // total samples, these are callees that were never invoked at runtime. 400 for (const auto &I : FS->getCallsiteSamples()) 401 for (const auto &J : I.second) { 402 const FunctionSamples *CalleeSamples = &J.second; 403 if (callsiteIsHot(CalleeSamples, PSI)) 404 Count += countUsedRecords(CalleeSamples, PSI); 405 } 406 407 return Count; 408 } 409 410 /// Return the number of sample records in the body of this profile. 411 /// 412 /// This count does not include records from cold inlined callsites. 413 unsigned 414 SampleCoverageTracker::countBodyRecords(const FunctionSamples *FS, 415 ProfileSummaryInfo *PSI) const { 416 unsigned Count = FS->getBodySamples().size(); 417 418 // Only count records in hot callsites. 419 for (const auto &I : FS->getCallsiteSamples()) 420 for (const auto &J : I.second) { 421 const FunctionSamples *CalleeSamples = &J.second; 422 if (callsiteIsHot(CalleeSamples, PSI)) 423 Count += countBodyRecords(CalleeSamples, PSI); 424 } 425 426 return Count; 427 } 428 429 /// Return the number of samples collected in the body of this profile. 430 /// 431 /// This count does not include samples from cold inlined callsites. 432 uint64_t 433 SampleCoverageTracker::countBodySamples(const FunctionSamples *FS, 434 ProfileSummaryInfo *PSI) const { 435 uint64_t Total = 0; 436 for (const auto &I : FS->getBodySamples()) 437 Total += I.second.getSamples(); 438 439 // Only count samples in hot callsites. 440 for (const auto &I : FS->getCallsiteSamples()) 441 for (const auto &J : I.second) { 442 const FunctionSamples *CalleeSamples = &J.second; 443 if (callsiteIsHot(CalleeSamples, PSI)) 444 Total += countBodySamples(CalleeSamples, PSI); 445 } 446 447 return Total; 448 } 449 450 /// Return the fraction of sample records used in this profile. 451 /// 452 /// The returned value is an unsigned integer in the range 0-100 indicating 453 /// the percentage of sample records that were used while applying this 454 /// profile to the associated function. 455 unsigned SampleCoverageTracker::computeCoverage(unsigned Used, 456 unsigned Total) const { 457 assert(Used <= Total && 458 "number of used records cannot exceed the total number of records"); 459 return Total > 0 ? Used * 100 / Total : 100; 460 } 461 462 /// Clear all the per-function data used to load samples and propagate weights. 463 void SampleProfileLoader::clearFunctionData() { 464 BlockWeights.clear(); 465 EdgeWeights.clear(); 466 VisitedBlocks.clear(); 467 VisitedEdges.clear(); 468 EquivalenceClass.clear(); 469 DT = nullptr; 470 PDT = nullptr; 471 LI = nullptr; 472 Predecessors.clear(); 473 Successors.clear(); 474 CoverageTracker.clear(); 475 } 476 477 #ifndef NDEBUG 478 /// Print the weight of edge \p E on stream \p OS. 479 /// 480 /// \param OS Stream to emit the output to. 481 /// \param E Edge to print. 482 void SampleProfileLoader::printEdgeWeight(raw_ostream &OS, Edge E) { 483 OS << "weight[" << E.first->getName() << "->" << E.second->getName() 484 << "]: " << EdgeWeights[E] << "\n"; 485 } 486 487 /// Print the equivalence class of block \p BB on stream \p OS. 488 /// 489 /// \param OS Stream to emit the output to. 490 /// \param BB Block to print. 491 void SampleProfileLoader::printBlockEquivalence(raw_ostream &OS, 492 const BasicBlock *BB) { 493 const BasicBlock *Equiv = EquivalenceClass[BB]; 494 OS << "equivalence[" << BB->getName() 495 << "]: " << ((Equiv) ? EquivalenceClass[BB]->getName() : "NONE") << "\n"; 496 } 497 498 /// Print the weight of block \p BB on stream \p OS. 499 /// 500 /// \param OS Stream to emit the output to. 501 /// \param BB Block to print. 502 void SampleProfileLoader::printBlockWeight(raw_ostream &OS, 503 const BasicBlock *BB) const { 504 const auto &I = BlockWeights.find(BB); 505 uint64_t W = (I == BlockWeights.end() ? 0 : I->second); 506 OS << "weight[" << BB->getName() << "]: " << W << "\n"; 507 } 508 #endif 509 510 /// Get the weight for an instruction. 511 /// 512 /// The "weight" of an instruction \p Inst is the number of samples 513 /// collected on that instruction at runtime. To retrieve it, we 514 /// need to compute the line number of \p Inst relative to the start of its 515 /// function. We use HeaderLineno to compute the offset. We then 516 /// look up the samples collected for \p Inst using BodySamples. 517 /// 518 /// \param Inst Instruction to query. 519 /// 520 /// \returns the weight of \p Inst. 521 ErrorOr<uint64_t> SampleProfileLoader::getInstWeight(const Instruction &Inst) { 522 const DebugLoc &DLoc = Inst.getDebugLoc(); 523 if (!DLoc) 524 return std::error_code(); 525 526 const FunctionSamples *FS = findFunctionSamples(Inst); 527 if (!FS) 528 return std::error_code(); 529 530 // Ignore all intrinsics and branch instructions. 531 // Branch instruction usually contains debug info from sources outside of 532 // the residing basic block, thus we ignore them during annotation. 533 if (isa<BranchInst>(Inst) || isa<IntrinsicInst>(Inst)) 534 return std::error_code(); 535 536 // If a direct call/invoke instruction is inlined in profile 537 // (findCalleeFunctionSamples returns non-empty result), but not inlined here, 538 // it means that the inlined callsite has no sample, thus the call 539 // instruction should have 0 count. 540 if ((isa<CallInst>(Inst) || isa<InvokeInst>(Inst)) && 541 !ImmutableCallSite(&Inst).isIndirectCall() && 542 findCalleeFunctionSamples(Inst)) 543 return 0; 544 545 const DILocation *DIL = DLoc; 546 uint32_t LineOffset = FunctionSamples::getOffset(DIL); 547 uint32_t Discriminator = DIL->getBaseDiscriminator(); 548 ErrorOr<uint64_t> R = FS->findSamplesAt(LineOffset, Discriminator); 549 if (R) { 550 bool FirstMark = 551 CoverageTracker.markSamplesUsed(FS, LineOffset, Discriminator, R.get()); 552 if (FirstMark) { 553 ORE->emit([&]() { 554 OptimizationRemarkAnalysis Remark(DEBUG_TYPE, "AppliedSamples", &Inst); 555 Remark << "Applied " << ore::NV("NumSamples", *R); 556 Remark << " samples from profile (offset: "; 557 Remark << ore::NV("LineOffset", LineOffset); 558 if (Discriminator) { 559 Remark << "."; 560 Remark << ore::NV("Discriminator", Discriminator); 561 } 562 Remark << ")"; 563 return Remark; 564 }); 565 } 566 LLVM_DEBUG(dbgs() << " " << DLoc.getLine() << "." 567 << DIL->getBaseDiscriminator() << ":" << Inst 568 << " (line offset: " << LineOffset << "." 569 << DIL->getBaseDiscriminator() << " - weight: " << R.get() 570 << ")\n"); 571 } 572 return R; 573 } 574 575 /// Compute the weight of a basic block. 576 /// 577 /// The weight of basic block \p BB is the maximum weight of all the 578 /// instructions in BB. 579 /// 580 /// \param BB The basic block to query. 581 /// 582 /// \returns the weight for \p BB. 583 ErrorOr<uint64_t> SampleProfileLoader::getBlockWeight(const BasicBlock *BB) { 584 uint64_t Max = 0; 585 bool HasWeight = false; 586 for (auto &I : BB->getInstList()) { 587 const ErrorOr<uint64_t> &R = getInstWeight(I); 588 if (R) { 589 Max = std::max(Max, R.get()); 590 HasWeight = true; 591 } 592 } 593 return HasWeight ? ErrorOr<uint64_t>(Max) : std::error_code(); 594 } 595 596 /// Compute and store the weights of every basic block. 597 /// 598 /// This populates the BlockWeights map by computing 599 /// the weights of every basic block in the CFG. 600 /// 601 /// \param F The function to query. 602 bool SampleProfileLoader::computeBlockWeights(Function &F) { 603 bool Changed = false; 604 LLVM_DEBUG(dbgs() << "Block weights\n"); 605 for (const auto &BB : F) { 606 ErrorOr<uint64_t> Weight = getBlockWeight(&BB); 607 if (Weight) { 608 BlockWeights[&BB] = Weight.get(); 609 VisitedBlocks.insert(&BB); 610 Changed = true; 611 } 612 LLVM_DEBUG(printBlockWeight(dbgs(), &BB)); 613 } 614 615 return Changed; 616 } 617 618 /// Get the FunctionSamples for a call instruction. 619 /// 620 /// The FunctionSamples of a call/invoke instruction \p Inst is the inlined 621 /// instance in which that call instruction is calling to. It contains 622 /// all samples that resides in the inlined instance. We first find the 623 /// inlined instance in which the call instruction is from, then we 624 /// traverse its children to find the callsite with the matching 625 /// location. 626 /// 627 /// \param Inst Call/Invoke instruction to query. 628 /// 629 /// \returns The FunctionSamples pointer to the inlined instance. 630 const FunctionSamples * 631 SampleProfileLoader::findCalleeFunctionSamples(const Instruction &Inst) const { 632 const DILocation *DIL = Inst.getDebugLoc(); 633 if (!DIL) { 634 return nullptr; 635 } 636 637 StringRef CalleeName; 638 if (const CallInst *CI = dyn_cast<CallInst>(&Inst)) 639 if (Function *Callee = CI->getCalledFunction()) 640 CalleeName = Callee->getName(); 641 642 const FunctionSamples *FS = findFunctionSamples(Inst); 643 if (FS == nullptr) 644 return nullptr; 645 646 std::string CalleeGUID; 647 CalleeName = getRepInFormat(CalleeName, Reader->getFormat(), CalleeGUID); 648 return FS->findFunctionSamplesAt(LineLocation(FunctionSamples::getOffset(DIL), 649 DIL->getBaseDiscriminator()), 650 CalleeName); 651 } 652 653 /// Returns a vector of FunctionSamples that are the indirect call targets 654 /// of \p Inst. The vector is sorted by the total number of samples. Stores 655 /// the total call count of the indirect call in \p Sum. 656 std::vector<const FunctionSamples *> 657 SampleProfileLoader::findIndirectCallFunctionSamples( 658 const Instruction &Inst, uint64_t &Sum) const { 659 const DILocation *DIL = Inst.getDebugLoc(); 660 std::vector<const FunctionSamples *> R; 661 662 if (!DIL) { 663 return R; 664 } 665 666 const FunctionSamples *FS = findFunctionSamples(Inst); 667 if (FS == nullptr) 668 return R; 669 670 uint32_t LineOffset = FunctionSamples::getOffset(DIL); 671 uint32_t Discriminator = DIL->getBaseDiscriminator(); 672 673 auto T = FS->findCallTargetMapAt(LineOffset, Discriminator); 674 Sum = 0; 675 if (T) 676 for (const auto &T_C : T.get()) 677 Sum += T_C.second; 678 if (const FunctionSamplesMap *M = FS->findFunctionSamplesMapAt(LineLocation( 679 FunctionSamples::getOffset(DIL), DIL->getBaseDiscriminator()))) { 680 if (M->empty()) 681 return R; 682 for (const auto &NameFS : *M) { 683 Sum += NameFS.second.getEntrySamples(); 684 R.push_back(&NameFS.second); 685 } 686 llvm::sort(R.begin(), R.end(), 687 [](const FunctionSamples *L, const FunctionSamples *R) { 688 return L->getEntrySamples() > R->getEntrySamples(); 689 }); 690 } 691 return R; 692 } 693 694 /// Get the FunctionSamples for an instruction. 695 /// 696 /// The FunctionSamples of an instruction \p Inst is the inlined instance 697 /// in which that instruction is coming from. We traverse the inline stack 698 /// of that instruction, and match it with the tree nodes in the profile. 699 /// 700 /// \param Inst Instruction to query. 701 /// 702 /// \returns the FunctionSamples pointer to the inlined instance. 703 const FunctionSamples * 704 SampleProfileLoader::findFunctionSamples(const Instruction &Inst) const { 705 SmallVector<std::pair<LineLocation, StringRef>, 10> S; 706 const DILocation *DIL = Inst.getDebugLoc(); 707 if (!DIL) 708 return Samples; 709 710 return Samples->findFunctionSamples(DIL); 711 } 712 713 bool SampleProfileLoader::inlineCallInstruction(Instruction *I) { 714 assert(isa<CallInst>(I) || isa<InvokeInst>(I)); 715 CallSite CS(I); 716 Function *CalledFunction = CS.getCalledFunction(); 717 assert(CalledFunction); 718 DebugLoc DLoc = I->getDebugLoc(); 719 BasicBlock *BB = I->getParent(); 720 InlineParams Params = getInlineParams(); 721 Params.ComputeFullInlineCost = true; 722 // Checks if there is anything in the reachable portion of the callee at 723 // this callsite that makes this inlining potentially illegal. Need to 724 // set ComputeFullInlineCost, otherwise getInlineCost may return early 725 // when cost exceeds threshold without checking all IRs in the callee. 726 // The acutal cost does not matter because we only checks isNever() to 727 // see if it is legal to inline the callsite. 728 InlineCost Cost = getInlineCost(CS, Params, GetTTI(*CalledFunction), GetAC, 729 None, nullptr, nullptr); 730 if (Cost.isNever()) { 731 ORE->emit(OptimizationRemark(DEBUG_TYPE, "Not inline", DLoc, BB) 732 << "incompatible inlining"); 733 return false; 734 } 735 InlineFunctionInfo IFI(nullptr, &GetAC); 736 if (InlineFunction(CS, IFI)) { 737 // The call to InlineFunction erases I, so we can't pass it here. 738 ORE->emit(OptimizationRemark(DEBUG_TYPE, "HotInline", DLoc, BB) 739 << "inlined hot callee '" << ore::NV("Callee", CalledFunction) 740 << "' into '" << ore::NV("Caller", BB->getParent()) << "'"); 741 return true; 742 } 743 return false; 744 } 745 746 /// Iteratively inline hot callsites of a function. 747 /// 748 /// Iteratively traverse all callsites of the function \p F, and find if 749 /// the corresponding inlined instance exists and is hot in profile. If 750 /// it is hot enough, inline the callsites and adds new callsites of the 751 /// callee into the caller. If the call is an indirect call, first promote 752 /// it to direct call. Each indirect call is limited with a single target. 753 /// 754 /// \param F function to perform iterative inlining. 755 /// \param InlinedGUIDs a set to be updated to include all GUIDs that are 756 /// inlined in the profiled binary. 757 /// 758 /// \returns True if there is any inline happened. 759 bool SampleProfileLoader::inlineHotFunctions( 760 Function &F, DenseSet<GlobalValue::GUID> &InlinedGUIDs) { 761 DenseSet<Instruction *> PromotedInsns; 762 bool Changed = false; 763 bool isCompact = (Reader->getFormat() == SPF_Compact_Binary); 764 while (true) { 765 bool LocalChanged = false; 766 SmallVector<Instruction *, 10> CIS; 767 for (auto &BB : F) { 768 bool Hot = false; 769 SmallVector<Instruction *, 10> Candidates; 770 for (auto &I : BB.getInstList()) { 771 const FunctionSamples *FS = nullptr; 772 if ((isa<CallInst>(I) || isa<InvokeInst>(I)) && 773 !isa<IntrinsicInst>(I) && (FS = findCalleeFunctionSamples(I))) { 774 Candidates.push_back(&I); 775 if (callsiteIsHot(FS, PSI)) 776 Hot = true; 777 } 778 } 779 if (Hot) { 780 CIS.insert(CIS.begin(), Candidates.begin(), Candidates.end()); 781 } 782 } 783 for (auto I : CIS) { 784 Function *CalledFunction = CallSite(I).getCalledFunction(); 785 // Do not inline recursive calls. 786 if (CalledFunction == &F) 787 continue; 788 if (CallSite(I).isIndirectCall()) { 789 if (PromotedInsns.count(I)) 790 continue; 791 uint64_t Sum; 792 for (const auto *FS : findIndirectCallFunctionSamples(*I, Sum)) { 793 if (IsThinLTOPreLink) { 794 FS->findInlinedFunctions(InlinedGUIDs, F.getParent(), 795 PSI->getOrCompHotCountThreshold(), 796 isCompact); 797 continue; 798 } 799 auto CalleeFunctionName = FS->getName(); 800 // If it is a recursive call, we do not inline it as it could bloat 801 // the code exponentially. There is way to better handle this, e.g. 802 // clone the caller first, and inline the cloned caller if it is 803 // recursive. As llvm does not inline recursive calls, we will 804 // simply ignore it instead of handling it explicitly. 805 std::string FGUID; 806 auto Fname = getRepInFormat(F.getName(), Reader->getFormat(), FGUID); 807 if (CalleeFunctionName == Fname) 808 continue; 809 810 const char *Reason = "Callee function not available"; 811 auto R = SymbolMap.find(CalleeFunctionName); 812 if (R != SymbolMap.end() && R->getValue() && 813 !R->getValue()->isDeclaration() && 814 R->getValue()->getSubprogram() && 815 isLegalToPromote(CallSite(I), R->getValue(), &Reason)) { 816 uint64_t C = FS->getEntrySamples(); 817 Instruction *DI = 818 pgo::promoteIndirectCall(I, R->getValue(), C, Sum, false, ORE); 819 Sum -= C; 820 PromotedInsns.insert(I); 821 // If profile mismatches, we should not attempt to inline DI. 822 if ((isa<CallInst>(DI) || isa<InvokeInst>(DI)) && 823 inlineCallInstruction(DI)) 824 LocalChanged = true; 825 } else { 826 LLVM_DEBUG(dbgs() 827 << "\nFailed to promote indirect call to " 828 << CalleeFunctionName << " because " << Reason << "\n"); 829 } 830 } 831 } else if (CalledFunction && CalledFunction->getSubprogram() && 832 !CalledFunction->isDeclaration()) { 833 if (inlineCallInstruction(I)) 834 LocalChanged = true; 835 } else if (IsThinLTOPreLink) { 836 findCalleeFunctionSamples(*I)->findInlinedFunctions( 837 InlinedGUIDs, F.getParent(), PSI->getOrCompHotCountThreshold(), 838 isCompact); 839 } 840 } 841 if (LocalChanged) { 842 Changed = true; 843 } else { 844 break; 845 } 846 } 847 return Changed; 848 } 849 850 /// Find equivalence classes for the given block. 851 /// 852 /// This finds all the blocks that are guaranteed to execute the same 853 /// number of times as \p BB1. To do this, it traverses all the 854 /// descendants of \p BB1 in the dominator or post-dominator tree. 855 /// 856 /// A block BB2 will be in the same equivalence class as \p BB1 if 857 /// the following holds: 858 /// 859 /// 1- \p BB1 is a descendant of BB2 in the opposite tree. So, if BB2 860 /// is a descendant of \p BB1 in the dominator tree, then BB2 should 861 /// dominate BB1 in the post-dominator tree. 862 /// 863 /// 2- Both BB2 and \p BB1 must be in the same loop. 864 /// 865 /// For every block BB2 that meets those two requirements, we set BB2's 866 /// equivalence class to \p BB1. 867 /// 868 /// \param BB1 Block to check. 869 /// \param Descendants Descendants of \p BB1 in either the dom or pdom tree. 870 /// \param DomTree Opposite dominator tree. If \p Descendants is filled 871 /// with blocks from \p BB1's dominator tree, then 872 /// this is the post-dominator tree, and vice versa. 873 template <bool IsPostDom> 874 void SampleProfileLoader::findEquivalencesFor( 875 BasicBlock *BB1, ArrayRef<BasicBlock *> Descendants, 876 DominatorTreeBase<BasicBlock, IsPostDom> *DomTree) { 877 const BasicBlock *EC = EquivalenceClass[BB1]; 878 uint64_t Weight = BlockWeights[EC]; 879 for (const auto *BB2 : Descendants) { 880 bool IsDomParent = DomTree->dominates(BB2, BB1); 881 bool IsInSameLoop = LI->getLoopFor(BB1) == LI->getLoopFor(BB2); 882 if (BB1 != BB2 && IsDomParent && IsInSameLoop) { 883 EquivalenceClass[BB2] = EC; 884 // If BB2 is visited, then the entire EC should be marked as visited. 885 if (VisitedBlocks.count(BB2)) { 886 VisitedBlocks.insert(EC); 887 } 888 889 // If BB2 is heavier than BB1, make BB2 have the same weight 890 // as BB1. 891 // 892 // Note that we don't worry about the opposite situation here 893 // (when BB2 is lighter than BB1). We will deal with this 894 // during the propagation phase. Right now, we just want to 895 // make sure that BB1 has the largest weight of all the 896 // members of its equivalence set. 897 Weight = std::max(Weight, BlockWeights[BB2]); 898 } 899 } 900 if (EC == &EC->getParent()->getEntryBlock()) { 901 BlockWeights[EC] = Samples->getHeadSamples() + 1; 902 } else { 903 BlockWeights[EC] = Weight; 904 } 905 } 906 907 /// Find equivalence classes. 908 /// 909 /// Since samples may be missing from blocks, we can fill in the gaps by setting 910 /// the weights of all the blocks in the same equivalence class to the same 911 /// weight. To compute the concept of equivalence, we use dominance and loop 912 /// information. Two blocks B1 and B2 are in the same equivalence class if B1 913 /// dominates B2, B2 post-dominates B1 and both are in the same loop. 914 /// 915 /// \param F The function to query. 916 void SampleProfileLoader::findEquivalenceClasses(Function &F) { 917 SmallVector<BasicBlock *, 8> DominatedBBs; 918 LLVM_DEBUG(dbgs() << "\nBlock equivalence classes\n"); 919 // Find equivalence sets based on dominance and post-dominance information. 920 for (auto &BB : F) { 921 BasicBlock *BB1 = &BB; 922 923 // Compute BB1's equivalence class once. 924 if (EquivalenceClass.count(BB1)) { 925 LLVM_DEBUG(printBlockEquivalence(dbgs(), BB1)); 926 continue; 927 } 928 929 // By default, blocks are in their own equivalence class. 930 EquivalenceClass[BB1] = BB1; 931 932 // Traverse all the blocks dominated by BB1. We are looking for 933 // every basic block BB2 such that: 934 // 935 // 1- BB1 dominates BB2. 936 // 2- BB2 post-dominates BB1. 937 // 3- BB1 and BB2 are in the same loop nest. 938 // 939 // If all those conditions hold, it means that BB2 is executed 940 // as many times as BB1, so they are placed in the same equivalence 941 // class by making BB2's equivalence class be BB1. 942 DominatedBBs.clear(); 943 DT->getDescendants(BB1, DominatedBBs); 944 findEquivalencesFor(BB1, DominatedBBs, PDT.get()); 945 946 LLVM_DEBUG(printBlockEquivalence(dbgs(), BB1)); 947 } 948 949 // Assign weights to equivalence classes. 950 // 951 // All the basic blocks in the same equivalence class will execute 952 // the same number of times. Since we know that the head block in 953 // each equivalence class has the largest weight, assign that weight 954 // to all the blocks in that equivalence class. 955 LLVM_DEBUG( 956 dbgs() << "\nAssign the same weight to all blocks in the same class\n"); 957 for (auto &BI : F) { 958 const BasicBlock *BB = &BI; 959 const BasicBlock *EquivBB = EquivalenceClass[BB]; 960 if (BB != EquivBB) 961 BlockWeights[BB] = BlockWeights[EquivBB]; 962 LLVM_DEBUG(printBlockWeight(dbgs(), BB)); 963 } 964 } 965 966 /// Visit the given edge to decide if it has a valid weight. 967 /// 968 /// If \p E has not been visited before, we copy to \p UnknownEdge 969 /// and increment the count of unknown edges. 970 /// 971 /// \param E Edge to visit. 972 /// \param NumUnknownEdges Current number of unknown edges. 973 /// \param UnknownEdge Set if E has not been visited before. 974 /// 975 /// \returns E's weight, if known. Otherwise, return 0. 976 uint64_t SampleProfileLoader::visitEdge(Edge E, unsigned *NumUnknownEdges, 977 Edge *UnknownEdge) { 978 if (!VisitedEdges.count(E)) { 979 (*NumUnknownEdges)++; 980 *UnknownEdge = E; 981 return 0; 982 } 983 984 return EdgeWeights[E]; 985 } 986 987 /// Propagate weights through incoming/outgoing edges. 988 /// 989 /// If the weight of a basic block is known, and there is only one edge 990 /// with an unknown weight, we can calculate the weight of that edge. 991 /// 992 /// Similarly, if all the edges have a known count, we can calculate the 993 /// count of the basic block, if needed. 994 /// 995 /// \param F Function to process. 996 /// \param UpdateBlockCount Whether we should update basic block counts that 997 /// has already been annotated. 998 /// 999 /// \returns True if new weights were assigned to edges or blocks. 1000 bool SampleProfileLoader::propagateThroughEdges(Function &F, 1001 bool UpdateBlockCount) { 1002 bool Changed = false; 1003 LLVM_DEBUG(dbgs() << "\nPropagation through edges\n"); 1004 for (const auto &BI : F) { 1005 const BasicBlock *BB = &BI; 1006 const BasicBlock *EC = EquivalenceClass[BB]; 1007 1008 // Visit all the predecessor and successor edges to determine 1009 // which ones have a weight assigned already. Note that it doesn't 1010 // matter that we only keep track of a single unknown edge. The 1011 // only case we are interested in handling is when only a single 1012 // edge is unknown (see setEdgeOrBlockWeight). 1013 for (unsigned i = 0; i < 2; i++) { 1014 uint64_t TotalWeight = 0; 1015 unsigned NumUnknownEdges = 0, NumTotalEdges = 0; 1016 Edge UnknownEdge, SelfReferentialEdge, SingleEdge; 1017 1018 if (i == 0) { 1019 // First, visit all predecessor edges. 1020 NumTotalEdges = Predecessors[BB].size(); 1021 for (auto *Pred : Predecessors[BB]) { 1022 Edge E = std::make_pair(Pred, BB); 1023 TotalWeight += visitEdge(E, &NumUnknownEdges, &UnknownEdge); 1024 if (E.first == E.second) 1025 SelfReferentialEdge = E; 1026 } 1027 if (NumTotalEdges == 1) { 1028 SingleEdge = std::make_pair(Predecessors[BB][0], BB); 1029 } 1030 } else { 1031 // On the second round, visit all successor edges. 1032 NumTotalEdges = Successors[BB].size(); 1033 for (auto *Succ : Successors[BB]) { 1034 Edge E = std::make_pair(BB, Succ); 1035 TotalWeight += visitEdge(E, &NumUnknownEdges, &UnknownEdge); 1036 } 1037 if (NumTotalEdges == 1) { 1038 SingleEdge = std::make_pair(BB, Successors[BB][0]); 1039 } 1040 } 1041 1042 // After visiting all the edges, there are three cases that we 1043 // can handle immediately: 1044 // 1045 // - All the edge weights are known (i.e., NumUnknownEdges == 0). 1046 // In this case, we simply check that the sum of all the edges 1047 // is the same as BB's weight. If not, we change BB's weight 1048 // to match. Additionally, if BB had not been visited before, 1049 // we mark it visited. 1050 // 1051 // - Only one edge is unknown and BB has already been visited. 1052 // In this case, we can compute the weight of the edge by 1053 // subtracting the total block weight from all the known 1054 // edge weights. If the edges weight more than BB, then the 1055 // edge of the last remaining edge is set to zero. 1056 // 1057 // - There exists a self-referential edge and the weight of BB is 1058 // known. In this case, this edge can be based on BB's weight. 1059 // We add up all the other known edges and set the weight on 1060 // the self-referential edge as we did in the previous case. 1061 // 1062 // In any other case, we must continue iterating. Eventually, 1063 // all edges will get a weight, or iteration will stop when 1064 // it reaches SampleProfileMaxPropagateIterations. 1065 if (NumUnknownEdges <= 1) { 1066 uint64_t &BBWeight = BlockWeights[EC]; 1067 if (NumUnknownEdges == 0) { 1068 if (!VisitedBlocks.count(EC)) { 1069 // If we already know the weight of all edges, the weight of the 1070 // basic block can be computed. It should be no larger than the sum 1071 // of all edge weights. 1072 if (TotalWeight > BBWeight) { 1073 BBWeight = TotalWeight; 1074 Changed = true; 1075 LLVM_DEBUG(dbgs() << "All edge weights for " << BB->getName() 1076 << " known. Set weight for block: "; 1077 printBlockWeight(dbgs(), BB);); 1078 } 1079 } else if (NumTotalEdges == 1 && 1080 EdgeWeights[SingleEdge] < BlockWeights[EC]) { 1081 // If there is only one edge for the visited basic block, use the 1082 // block weight to adjust edge weight if edge weight is smaller. 1083 EdgeWeights[SingleEdge] = BlockWeights[EC]; 1084 Changed = true; 1085 } 1086 } else if (NumUnknownEdges == 1 && VisitedBlocks.count(EC)) { 1087 // If there is a single unknown edge and the block has been 1088 // visited, then we can compute E's weight. 1089 if (BBWeight >= TotalWeight) 1090 EdgeWeights[UnknownEdge] = BBWeight - TotalWeight; 1091 else 1092 EdgeWeights[UnknownEdge] = 0; 1093 const BasicBlock *OtherEC; 1094 if (i == 0) 1095 OtherEC = EquivalenceClass[UnknownEdge.first]; 1096 else 1097 OtherEC = EquivalenceClass[UnknownEdge.second]; 1098 // Edge weights should never exceed the BB weights it connects. 1099 if (VisitedBlocks.count(OtherEC) && 1100 EdgeWeights[UnknownEdge] > BlockWeights[OtherEC]) 1101 EdgeWeights[UnknownEdge] = BlockWeights[OtherEC]; 1102 VisitedEdges.insert(UnknownEdge); 1103 Changed = true; 1104 LLVM_DEBUG(dbgs() << "Set weight for edge: "; 1105 printEdgeWeight(dbgs(), UnknownEdge)); 1106 } 1107 } else if (VisitedBlocks.count(EC) && BlockWeights[EC] == 0) { 1108 // If a block Weights 0, all its in/out edges should weight 0. 1109 if (i == 0) { 1110 for (auto *Pred : Predecessors[BB]) { 1111 Edge E = std::make_pair(Pred, BB); 1112 EdgeWeights[E] = 0; 1113 VisitedEdges.insert(E); 1114 } 1115 } else { 1116 for (auto *Succ : Successors[BB]) { 1117 Edge E = std::make_pair(BB, Succ); 1118 EdgeWeights[E] = 0; 1119 VisitedEdges.insert(E); 1120 } 1121 } 1122 } else if (SelfReferentialEdge.first && VisitedBlocks.count(EC)) { 1123 uint64_t &BBWeight = BlockWeights[BB]; 1124 // We have a self-referential edge and the weight of BB is known. 1125 if (BBWeight >= TotalWeight) 1126 EdgeWeights[SelfReferentialEdge] = BBWeight - TotalWeight; 1127 else 1128 EdgeWeights[SelfReferentialEdge] = 0; 1129 VisitedEdges.insert(SelfReferentialEdge); 1130 Changed = true; 1131 LLVM_DEBUG(dbgs() << "Set self-referential edge weight to: "; 1132 printEdgeWeight(dbgs(), SelfReferentialEdge)); 1133 } 1134 if (UpdateBlockCount && !VisitedBlocks.count(EC) && TotalWeight > 0) { 1135 BlockWeights[EC] = TotalWeight; 1136 VisitedBlocks.insert(EC); 1137 Changed = true; 1138 } 1139 } 1140 } 1141 1142 return Changed; 1143 } 1144 1145 /// Build in/out edge lists for each basic block in the CFG. 1146 /// 1147 /// We are interested in unique edges. If a block B1 has multiple 1148 /// edges to another block B2, we only add a single B1->B2 edge. 1149 void SampleProfileLoader::buildEdges(Function &F) { 1150 for (auto &BI : F) { 1151 BasicBlock *B1 = &BI; 1152 1153 // Add predecessors for B1. 1154 SmallPtrSet<BasicBlock *, 16> Visited; 1155 if (!Predecessors[B1].empty()) 1156 llvm_unreachable("Found a stale predecessors list in a basic block."); 1157 for (pred_iterator PI = pred_begin(B1), PE = pred_end(B1); PI != PE; ++PI) { 1158 BasicBlock *B2 = *PI; 1159 if (Visited.insert(B2).second) 1160 Predecessors[B1].push_back(B2); 1161 } 1162 1163 // Add successors for B1. 1164 Visited.clear(); 1165 if (!Successors[B1].empty()) 1166 llvm_unreachable("Found a stale successors list in a basic block."); 1167 for (succ_iterator SI = succ_begin(B1), SE = succ_end(B1); SI != SE; ++SI) { 1168 BasicBlock *B2 = *SI; 1169 if (Visited.insert(B2).second) 1170 Successors[B1].push_back(B2); 1171 } 1172 } 1173 } 1174 1175 /// Returns the sorted CallTargetMap \p M by count in descending order. 1176 static SmallVector<InstrProfValueData, 2> SortCallTargets( 1177 const SampleRecord::CallTargetMap &M) { 1178 SmallVector<InstrProfValueData, 2> R; 1179 for (auto I = M.begin(); I != M.end(); ++I) 1180 R.push_back({Function::getGUID(I->getKey()), I->getValue()}); 1181 llvm::sort(R.begin(), R.end(), 1182 [](const InstrProfValueData &L, const InstrProfValueData &R) { 1183 if (L.Count == R.Count) 1184 return L.Value > R.Value; 1185 else 1186 return L.Count > R.Count; 1187 }); 1188 return R; 1189 } 1190 1191 /// Propagate weights into edges 1192 /// 1193 /// The following rules are applied to every block BB in the CFG: 1194 /// 1195 /// - If BB has a single predecessor/successor, then the weight 1196 /// of that edge is the weight of the block. 1197 /// 1198 /// - If all incoming or outgoing edges are known except one, and the 1199 /// weight of the block is already known, the weight of the unknown 1200 /// edge will be the weight of the block minus the sum of all the known 1201 /// edges. If the sum of all the known edges is larger than BB's weight, 1202 /// we set the unknown edge weight to zero. 1203 /// 1204 /// - If there is a self-referential edge, and the weight of the block is 1205 /// known, the weight for that edge is set to the weight of the block 1206 /// minus the weight of the other incoming edges to that block (if 1207 /// known). 1208 void SampleProfileLoader::propagateWeights(Function &F) { 1209 bool Changed = true; 1210 unsigned I = 0; 1211 1212 // If BB weight is larger than its corresponding loop's header BB weight, 1213 // use the BB weight to replace the loop header BB weight. 1214 for (auto &BI : F) { 1215 BasicBlock *BB = &BI; 1216 Loop *L = LI->getLoopFor(BB); 1217 if (!L) { 1218 continue; 1219 } 1220 BasicBlock *Header = L->getHeader(); 1221 if (Header && BlockWeights[BB] > BlockWeights[Header]) { 1222 BlockWeights[Header] = BlockWeights[BB]; 1223 } 1224 } 1225 1226 // Before propagation starts, build, for each block, a list of 1227 // unique predecessors and successors. This is necessary to handle 1228 // identical edges in multiway branches. Since we visit all blocks and all 1229 // edges of the CFG, it is cleaner to build these lists once at the start 1230 // of the pass. 1231 buildEdges(F); 1232 1233 // Propagate until we converge or we go past the iteration limit. 1234 while (Changed && I++ < SampleProfileMaxPropagateIterations) { 1235 Changed = propagateThroughEdges(F, false); 1236 } 1237 1238 // The first propagation propagates BB counts from annotated BBs to unknown 1239 // BBs. The 2nd propagation pass resets edges weights, and use all BB weights 1240 // to propagate edge weights. 1241 VisitedEdges.clear(); 1242 Changed = true; 1243 while (Changed && I++ < SampleProfileMaxPropagateIterations) { 1244 Changed = propagateThroughEdges(F, false); 1245 } 1246 1247 // The 3rd propagation pass allows adjust annotated BB weights that are 1248 // obviously wrong. 1249 Changed = true; 1250 while (Changed && I++ < SampleProfileMaxPropagateIterations) { 1251 Changed = propagateThroughEdges(F, true); 1252 } 1253 1254 // Generate MD_prof metadata for every branch instruction using the 1255 // edge weights computed during propagation. 1256 LLVM_DEBUG(dbgs() << "\nPropagation complete. Setting branch weights\n"); 1257 LLVMContext &Ctx = F.getContext(); 1258 MDBuilder MDB(Ctx); 1259 for (auto &BI : F) { 1260 BasicBlock *BB = &BI; 1261 1262 if (BlockWeights[BB]) { 1263 for (auto &I : BB->getInstList()) { 1264 if (!isa<CallInst>(I) && !isa<InvokeInst>(I)) 1265 continue; 1266 CallSite CS(&I); 1267 if (!CS.getCalledFunction()) { 1268 const DebugLoc &DLoc = I.getDebugLoc(); 1269 if (!DLoc) 1270 continue; 1271 const DILocation *DIL = DLoc; 1272 uint32_t LineOffset = FunctionSamples::getOffset(DIL); 1273 uint32_t Discriminator = DIL->getBaseDiscriminator(); 1274 1275 const FunctionSamples *FS = findFunctionSamples(I); 1276 if (!FS) 1277 continue; 1278 auto T = FS->findCallTargetMapAt(LineOffset, Discriminator); 1279 if (!T || T.get().empty()) 1280 continue; 1281 SmallVector<InstrProfValueData, 2> SortedCallTargets = 1282 SortCallTargets(T.get()); 1283 uint64_t Sum; 1284 findIndirectCallFunctionSamples(I, Sum); 1285 annotateValueSite(*I.getParent()->getParent()->getParent(), I, 1286 SortedCallTargets, Sum, IPVK_IndirectCallTarget, 1287 SortedCallTargets.size()); 1288 } else if (!dyn_cast<IntrinsicInst>(&I)) { 1289 SmallVector<uint32_t, 1> Weights; 1290 Weights.push_back(BlockWeights[BB]); 1291 I.setMetadata(LLVMContext::MD_prof, MDB.createBranchWeights(Weights)); 1292 } 1293 } 1294 } 1295 TerminatorInst *TI = BB->getTerminator(); 1296 if (TI->getNumSuccessors() == 1) 1297 continue; 1298 if (!isa<BranchInst>(TI) && !isa<SwitchInst>(TI)) 1299 continue; 1300 1301 DebugLoc BranchLoc = TI->getDebugLoc(); 1302 LLVM_DEBUG(dbgs() << "\nGetting weights for branch at line " 1303 << ((BranchLoc) ? Twine(BranchLoc.getLine()) 1304 : Twine("<UNKNOWN LOCATION>")) 1305 << ".\n"); 1306 SmallVector<uint32_t, 4> Weights; 1307 uint32_t MaxWeight = 0; 1308 Instruction *MaxDestInst; 1309 for (unsigned I = 0; I < TI->getNumSuccessors(); ++I) { 1310 BasicBlock *Succ = TI->getSuccessor(I); 1311 Edge E = std::make_pair(BB, Succ); 1312 uint64_t Weight = EdgeWeights[E]; 1313 LLVM_DEBUG(dbgs() << "\t"; printEdgeWeight(dbgs(), E)); 1314 // Use uint32_t saturated arithmetic to adjust the incoming weights, 1315 // if needed. Sample counts in profiles are 64-bit unsigned values, 1316 // but internally branch weights are expressed as 32-bit values. 1317 if (Weight > std::numeric_limits<uint32_t>::max()) { 1318 LLVM_DEBUG(dbgs() << " (saturated due to uint32_t overflow)"); 1319 Weight = std::numeric_limits<uint32_t>::max(); 1320 } 1321 // Weight is added by one to avoid propagation errors introduced by 1322 // 0 weights. 1323 Weights.push_back(static_cast<uint32_t>(Weight + 1)); 1324 if (Weight != 0) { 1325 if (Weight > MaxWeight) { 1326 MaxWeight = Weight; 1327 MaxDestInst = Succ->getFirstNonPHIOrDbgOrLifetime(); 1328 } 1329 } 1330 } 1331 1332 uint64_t TempWeight; 1333 // Only set weights if there is at least one non-zero weight. 1334 // In any other case, let the analyzer set weights. 1335 // Do not set weights if the weights are present. In ThinLTO, the profile 1336 // annotation is done twice. If the first annotation already set the 1337 // weights, the second pass does not need to set it. 1338 if (MaxWeight > 0 && !TI->extractProfTotalWeight(TempWeight)) { 1339 LLVM_DEBUG(dbgs() << "SUCCESS. Found non-zero weights.\n"); 1340 TI->setMetadata(LLVMContext::MD_prof, 1341 MDB.createBranchWeights(Weights)); 1342 ORE->emit([&]() { 1343 return OptimizationRemark(DEBUG_TYPE, "PopularDest", MaxDestInst) 1344 << "most popular destination for conditional branches at " 1345 << ore::NV("CondBranchesLoc", BranchLoc); 1346 }); 1347 } else { 1348 LLVM_DEBUG(dbgs() << "SKIPPED. All branch weights are zero.\n"); 1349 } 1350 } 1351 } 1352 1353 /// Get the line number for the function header. 1354 /// 1355 /// This looks up function \p F in the current compilation unit and 1356 /// retrieves the line number where the function is defined. This is 1357 /// line 0 for all the samples read from the profile file. Every line 1358 /// number is relative to this line. 1359 /// 1360 /// \param F Function object to query. 1361 /// 1362 /// \returns the line number where \p F is defined. If it returns 0, 1363 /// it means that there is no debug information available for \p F. 1364 unsigned SampleProfileLoader::getFunctionLoc(Function &F) { 1365 if (DISubprogram *S = F.getSubprogram()) 1366 return S->getLine(); 1367 1368 if (NoWarnSampleUnused) 1369 return 0; 1370 1371 // If the start of \p F is missing, emit a diagnostic to inform the user 1372 // about the missed opportunity. 1373 F.getContext().diagnose(DiagnosticInfoSampleProfile( 1374 "No debug information found in function " + F.getName() + 1375 ": Function profile not used", 1376 DS_Warning)); 1377 return 0; 1378 } 1379 1380 void SampleProfileLoader::computeDominanceAndLoopInfo(Function &F) { 1381 DT.reset(new DominatorTree); 1382 DT->recalculate(F); 1383 1384 PDT.reset(new PostDominatorTree(F)); 1385 1386 LI.reset(new LoopInfo); 1387 LI->analyze(*DT); 1388 } 1389 1390 /// Generate branch weight metadata for all branches in \p F. 1391 /// 1392 /// Branch weights are computed out of instruction samples using a 1393 /// propagation heuristic. Propagation proceeds in 3 phases: 1394 /// 1395 /// 1- Assignment of block weights. All the basic blocks in the function 1396 /// are initial assigned the same weight as their most frequently 1397 /// executed instruction. 1398 /// 1399 /// 2- Creation of equivalence classes. Since samples may be missing from 1400 /// blocks, we can fill in the gaps by setting the weights of all the 1401 /// blocks in the same equivalence class to the same weight. To compute 1402 /// the concept of equivalence, we use dominance and loop information. 1403 /// Two blocks B1 and B2 are in the same equivalence class if B1 1404 /// dominates B2, B2 post-dominates B1 and both are in the same loop. 1405 /// 1406 /// 3- Propagation of block weights into edges. This uses a simple 1407 /// propagation heuristic. The following rules are applied to every 1408 /// block BB in the CFG: 1409 /// 1410 /// - If BB has a single predecessor/successor, then the weight 1411 /// of that edge is the weight of the block. 1412 /// 1413 /// - If all the edges are known except one, and the weight of the 1414 /// block is already known, the weight of the unknown edge will 1415 /// be the weight of the block minus the sum of all the known 1416 /// edges. If the sum of all the known edges is larger than BB's weight, 1417 /// we set the unknown edge weight to zero. 1418 /// 1419 /// - If there is a self-referential edge, and the weight of the block is 1420 /// known, the weight for that edge is set to the weight of the block 1421 /// minus the weight of the other incoming edges to that block (if 1422 /// known). 1423 /// 1424 /// Since this propagation is not guaranteed to finalize for every CFG, we 1425 /// only allow it to proceed for a limited number of iterations (controlled 1426 /// by -sample-profile-max-propagate-iterations). 1427 /// 1428 /// FIXME: Try to replace this propagation heuristic with a scheme 1429 /// that is guaranteed to finalize. A work-list approach similar to 1430 /// the standard value propagation algorithm used by SSA-CCP might 1431 /// work here. 1432 /// 1433 /// Once all the branch weights are computed, we emit the MD_prof 1434 /// metadata on BB using the computed values for each of its branches. 1435 /// 1436 /// \param F The function to query. 1437 /// 1438 /// \returns true if \p F was modified. Returns false, otherwise. 1439 bool SampleProfileLoader::emitAnnotations(Function &F) { 1440 bool Changed = false; 1441 1442 if (getFunctionLoc(F) == 0) 1443 return false; 1444 1445 LLVM_DEBUG(dbgs() << "Line number for the first instruction in " 1446 << F.getName() << ": " << getFunctionLoc(F) << "\n"); 1447 1448 DenseSet<GlobalValue::GUID> InlinedGUIDs; 1449 Changed |= inlineHotFunctions(F, InlinedGUIDs); 1450 1451 // Compute basic block weights. 1452 Changed |= computeBlockWeights(F); 1453 1454 if (Changed) { 1455 // Add an entry count to the function using the samples gathered at the 1456 // function entry. 1457 // Sets the GUIDs that are inlined in the profiled binary. This is used 1458 // for ThinLink to make correct liveness analysis, and also make the IR 1459 // match the profiled binary before annotation. 1460 F.setEntryCount( 1461 ProfileCount(Samples->getHeadSamples() + 1, Function::PCT_Real), 1462 &InlinedGUIDs); 1463 1464 // Compute dominance and loop info needed for propagation. 1465 computeDominanceAndLoopInfo(F); 1466 1467 // Find equivalence classes. 1468 findEquivalenceClasses(F); 1469 1470 // Propagate weights to all edges. 1471 propagateWeights(F); 1472 } 1473 1474 // If coverage checking was requested, compute it now. 1475 if (SampleProfileRecordCoverage) { 1476 unsigned Used = CoverageTracker.countUsedRecords(Samples, PSI); 1477 unsigned Total = CoverageTracker.countBodyRecords(Samples, PSI); 1478 unsigned Coverage = CoverageTracker.computeCoverage(Used, Total); 1479 if (Coverage < SampleProfileRecordCoverage) { 1480 F.getContext().diagnose(DiagnosticInfoSampleProfile( 1481 F.getSubprogram()->getFilename(), getFunctionLoc(F), 1482 Twine(Used) + " of " + Twine(Total) + " available profile records (" + 1483 Twine(Coverage) + "%) were applied", 1484 DS_Warning)); 1485 } 1486 } 1487 1488 if (SampleProfileSampleCoverage) { 1489 uint64_t Used = CoverageTracker.getTotalUsedSamples(); 1490 uint64_t Total = CoverageTracker.countBodySamples(Samples, PSI); 1491 unsigned Coverage = CoverageTracker.computeCoverage(Used, Total); 1492 if (Coverage < SampleProfileSampleCoverage) { 1493 F.getContext().diagnose(DiagnosticInfoSampleProfile( 1494 F.getSubprogram()->getFilename(), getFunctionLoc(F), 1495 Twine(Used) + " of " + Twine(Total) + " available profile samples (" + 1496 Twine(Coverage) + "%) were applied", 1497 DS_Warning)); 1498 } 1499 } 1500 return Changed; 1501 } 1502 1503 char SampleProfileLoaderLegacyPass::ID = 0; 1504 1505 INITIALIZE_PASS_BEGIN(SampleProfileLoaderLegacyPass, "sample-profile", 1506 "Sample Profile loader", false, false) 1507 INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker) 1508 INITIALIZE_PASS_DEPENDENCY(TargetTransformInfoWrapperPass) 1509 INITIALIZE_PASS_DEPENDENCY(ProfileSummaryInfoWrapperPass) 1510 INITIALIZE_PASS_END(SampleProfileLoaderLegacyPass, "sample-profile", 1511 "Sample Profile loader", false, false) 1512 1513 bool SampleProfileLoader::doInitialization(Module &M) { 1514 auto &Ctx = M.getContext(); 1515 auto ReaderOrErr = SampleProfileReader::create(Filename, Ctx); 1516 if (std::error_code EC = ReaderOrErr.getError()) { 1517 std::string Msg = "Could not open profile: " + EC.message(); 1518 Ctx.diagnose(DiagnosticInfoSampleProfile(Filename, Msg)); 1519 return false; 1520 } 1521 Reader = std::move(ReaderOrErr.get()); 1522 ProfileIsValid = (Reader->read() == sampleprof_error::success); 1523 return true; 1524 } 1525 1526 ModulePass *llvm::createSampleProfileLoaderPass() { 1527 return new SampleProfileLoaderLegacyPass(SampleProfileFile); 1528 } 1529 1530 ModulePass *llvm::createSampleProfileLoaderPass(StringRef Name) { 1531 return new SampleProfileLoaderLegacyPass(Name); 1532 } 1533 1534 bool SampleProfileLoader::runOnModule(Module &M, ModuleAnalysisManager *AM, 1535 ProfileSummaryInfo *_PSI) { 1536 if (!ProfileIsValid) 1537 return false; 1538 1539 PSI = _PSI; 1540 if (M.getProfileSummary() == nullptr) 1541 M.setProfileSummary(Reader->getSummary().getMD(M.getContext())); 1542 1543 // Compute the total number of samples collected in this profile. 1544 for (const auto &I : Reader->getProfiles()) 1545 TotalCollectedSamples += I.second.getTotalSamples(); 1546 1547 // Populate the symbol map. 1548 for (const auto &N_F : M.getValueSymbolTable()) { 1549 StringRef OrigName = N_F.getKey(); 1550 Function *F = dyn_cast<Function>(N_F.getValue()); 1551 if (F == nullptr) 1552 continue; 1553 SymbolMap[OrigName] = F; 1554 auto pos = OrigName.find('.'); 1555 if (pos != StringRef::npos) { 1556 StringRef NewName = OrigName.substr(0, pos); 1557 auto r = SymbolMap.insert(std::make_pair(NewName, F)); 1558 // Failiing to insert means there is already an entry in SymbolMap, 1559 // thus there are multiple functions that are mapped to the same 1560 // stripped name. In this case of name conflicting, set the value 1561 // to nullptr to avoid confusion. 1562 if (!r.second) 1563 r.first->second = nullptr; 1564 } 1565 } 1566 1567 bool retval = false; 1568 for (auto &F : M) 1569 if (!F.isDeclaration()) { 1570 clearFunctionData(); 1571 retval |= runOnFunction(F, AM); 1572 } 1573 return retval; 1574 } 1575 1576 bool SampleProfileLoaderLegacyPass::runOnModule(Module &M) { 1577 ACT = &getAnalysis<AssumptionCacheTracker>(); 1578 TTIWP = &getAnalysis<TargetTransformInfoWrapperPass>(); 1579 ProfileSummaryInfo *PSI = 1580 getAnalysis<ProfileSummaryInfoWrapperPass>().getPSI(); 1581 return SampleLoader.runOnModule(M, nullptr, PSI); 1582 } 1583 1584 bool SampleProfileLoader::runOnFunction(Function &F, ModuleAnalysisManager *AM) { 1585 // Initialize the entry count to -1, which will be treated conservatively 1586 // by getEntryCount as the same as unknown (None). If we have samples this 1587 // will be overwritten in emitAnnotations. 1588 F.setEntryCount(ProfileCount(-1, Function::PCT_Real)); 1589 std::unique_ptr<OptimizationRemarkEmitter> OwnedORE; 1590 if (AM) { 1591 auto &FAM = 1592 AM->getResult<FunctionAnalysisManagerModuleProxy>(*F.getParent()) 1593 .getManager(); 1594 ORE = &FAM.getResult<OptimizationRemarkEmitterAnalysis>(F); 1595 } else { 1596 OwnedORE = make_unique<OptimizationRemarkEmitter>(&F); 1597 ORE = OwnedORE.get(); 1598 } 1599 Samples = Reader->getSamplesFor(F); 1600 if (Samples && !Samples->empty()) 1601 return emitAnnotations(F); 1602 return false; 1603 } 1604 1605 PreservedAnalyses SampleProfileLoaderPass::run(Module &M, 1606 ModuleAnalysisManager &AM) { 1607 FunctionAnalysisManager &FAM = 1608 AM.getResult<FunctionAnalysisManagerModuleProxy>(M).getManager(); 1609 1610 auto GetAssumptionCache = [&](Function &F) -> AssumptionCache & { 1611 return FAM.getResult<AssumptionAnalysis>(F); 1612 }; 1613 auto GetTTI = [&](Function &F) -> TargetTransformInfo & { 1614 return FAM.getResult<TargetIRAnalysis>(F); 1615 }; 1616 1617 SampleProfileLoader SampleLoader( 1618 ProfileFileName.empty() ? SampleProfileFile : ProfileFileName, 1619 IsThinLTOPreLink, GetAssumptionCache, GetTTI); 1620 1621 SampleLoader.doInitialization(M); 1622 1623 ProfileSummaryInfo *PSI = &AM.getResult<ProfileSummaryAnalysis>(M); 1624 if (!SampleLoader.runOnModule(M, &AM, PSI)) 1625 return PreservedAnalyses::all(); 1626 1627 return PreservedAnalyses::none(); 1628 } 1629