1 //===- IndirectCallPromotion.cpp - Optimizations based on value profiling -===// 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 transformation that promotes indirect calls to 11 // conditional direct calls when the indirect-call value profile metadata is 12 // available. 13 // 14 //===----------------------------------------------------------------------===// 15 16 #include "llvm/ADT/ArrayRef.h" 17 #include "llvm/ADT/STLExtras.h" 18 #include "llvm/ADT/SmallVector.h" 19 #include "llvm/ADT/Statistic.h" 20 #include "llvm/ADT/StringRef.h" 21 #include "llvm/Analysis/IndirectCallPromotionAnalysis.h" 22 #include "llvm/Analysis/IndirectCallSiteVisitor.h" 23 #include "llvm/Analysis/OptimizationRemarkEmitter.h" 24 #include "llvm/Analysis/ProfileSummaryInfo.h" 25 #include "llvm/IR/Attributes.h" 26 #include "llvm/IR/BasicBlock.h" 27 #include "llvm/IR/CallSite.h" 28 #include "llvm/IR/DerivedTypes.h" 29 #include "llvm/IR/DiagnosticInfo.h" 30 #include "llvm/IR/Function.h" 31 #include "llvm/IR/IRBuilder.h" 32 #include "llvm/IR/InstrTypes.h" 33 #include "llvm/IR/Instruction.h" 34 #include "llvm/IR/Instructions.h" 35 #include "llvm/IR/LLVMContext.h" 36 #include "llvm/IR/MDBuilder.h" 37 #include "llvm/IR/PassManager.h" 38 #include "llvm/IR/Type.h" 39 #include "llvm/IR/Value.h" 40 #include "llvm/Pass.h" 41 #include "llvm/ProfileData/InstrProf.h" 42 #include "llvm/Support/Casting.h" 43 #include "llvm/Support/CommandLine.h" 44 #include "llvm/Support/Error.h" 45 #include "llvm/Support/Debug.h" 46 #include "llvm/Support/raw_ostream.h" 47 #include "llvm/Transforms/Instrumentation.h" 48 #include "llvm/Transforms/Instrumentation/PGOInstrumentation.h" 49 #include "llvm/Transforms/Utils/BasicBlockUtils.h" 50 #include "llvm/Transforms/Utils/CallPromotionUtils.h" 51 #include <cassert> 52 #include <cstdint> 53 #include <memory> 54 #include <string> 55 #include <utility> 56 #include <vector> 57 58 using namespace llvm; 59 60 #define DEBUG_TYPE "pgo-icall-prom" 61 62 STATISTIC(NumOfPGOICallPromotion, "Number of indirect call promotions."); 63 STATISTIC(NumOfPGOICallsites, "Number of indirect call candidate sites."); 64 65 // Command line option to disable indirect-call promotion with the default as 66 // false. This is for debug purpose. 67 static cl::opt<bool> DisableICP("disable-icp", cl::init(false), cl::Hidden, 68 cl::desc("Disable indirect call promotion")); 69 70 // Set the cutoff value for the promotion. If the value is other than 0, we 71 // stop the transformation once the total number of promotions equals the cutoff 72 // value. 73 // For debug use only. 74 static cl::opt<unsigned> 75 ICPCutOff("icp-cutoff", cl::init(0), cl::Hidden, cl::ZeroOrMore, 76 cl::desc("Max number of promotions for this compilation")); 77 78 // If ICPCSSkip is non zero, the first ICPCSSkip callsites will be skipped. 79 // For debug use only. 80 static cl::opt<unsigned> 81 ICPCSSkip("icp-csskip", cl::init(0), cl::Hidden, cl::ZeroOrMore, 82 cl::desc("Skip Callsite up to this number for this compilation")); 83 84 // Set if the pass is called in LTO optimization. The difference for LTO mode 85 // is the pass won't prefix the source module name to the internal linkage 86 // symbols. 87 static cl::opt<bool> ICPLTOMode("icp-lto", cl::init(false), cl::Hidden, 88 cl::desc("Run indirect-call promotion in LTO " 89 "mode")); 90 91 // Set if the pass is called in SamplePGO mode. The difference for SamplePGO 92 // mode is it will add prof metadatato the created direct call. 93 static cl::opt<bool> 94 ICPSamplePGOMode("icp-samplepgo", cl::init(false), cl::Hidden, 95 cl::desc("Run indirect-call promotion in SamplePGO mode")); 96 97 // If the option is set to true, only call instructions will be considered for 98 // transformation -- invoke instructions will be ignored. 99 static cl::opt<bool> 100 ICPCallOnly("icp-call-only", cl::init(false), cl::Hidden, 101 cl::desc("Run indirect-call promotion for call instructions " 102 "only")); 103 104 // If the option is set to true, only invoke instructions will be considered for 105 // transformation -- call instructions will be ignored. 106 static cl::opt<bool> ICPInvokeOnly("icp-invoke-only", cl::init(false), 107 cl::Hidden, 108 cl::desc("Run indirect-call promotion for " 109 "invoke instruction only")); 110 111 // Dump the function level IR if the transformation happened in this 112 // function. For debug use only. 113 static cl::opt<bool> 114 ICPDUMPAFTER("icp-dumpafter", cl::init(false), cl::Hidden, 115 cl::desc("Dump IR after transformation happens")); 116 117 namespace { 118 119 class PGOIndirectCallPromotionLegacyPass : public ModulePass { 120 public: 121 static char ID; 122 123 PGOIndirectCallPromotionLegacyPass(bool InLTO = false, bool SamplePGO = false) 124 : ModulePass(ID), InLTO(InLTO), SamplePGO(SamplePGO) { 125 initializePGOIndirectCallPromotionLegacyPassPass( 126 *PassRegistry::getPassRegistry()); 127 } 128 129 void getAnalysisUsage(AnalysisUsage &AU) const override { 130 AU.addRequired<ProfileSummaryInfoWrapperPass>(); 131 } 132 133 StringRef getPassName() const override { return "PGOIndirectCallPromotion"; } 134 135 private: 136 bool runOnModule(Module &M) override; 137 138 // If this pass is called in LTO. We need to special handling the PGOFuncName 139 // for the static variables due to LTO's internalization. 140 bool InLTO; 141 142 // If this pass is called in SamplePGO. We need to add the prof metadata to 143 // the promoted direct call. 144 bool SamplePGO; 145 }; 146 147 } // end anonymous namespace 148 149 char PGOIndirectCallPromotionLegacyPass::ID = 0; 150 151 INITIALIZE_PASS_BEGIN(PGOIndirectCallPromotionLegacyPass, "pgo-icall-prom", 152 "Use PGO instrumentation profile to promote indirect " 153 "calls to direct calls.", 154 false, false) 155 INITIALIZE_PASS_DEPENDENCY(ProfileSummaryInfoWrapperPass) 156 INITIALIZE_PASS_END(PGOIndirectCallPromotionLegacyPass, "pgo-icall-prom", 157 "Use PGO instrumentation profile to promote indirect " 158 "calls to direct calls.", 159 false, false) 160 161 ModulePass *llvm::createPGOIndirectCallPromotionLegacyPass(bool InLTO, 162 bool SamplePGO) { 163 return new PGOIndirectCallPromotionLegacyPass(InLTO, SamplePGO); 164 } 165 166 namespace { 167 168 // The class for main data structure to promote indirect calls to conditional 169 // direct calls. 170 class ICallPromotionFunc { 171 private: 172 Function &F; 173 Module *M; 174 175 // Symtab that maps indirect call profile values to function names and 176 // defines. 177 InstrProfSymtab *Symtab; 178 179 bool SamplePGO; 180 181 OptimizationRemarkEmitter &ORE; 182 183 // A struct that records the direct target and it's call count. 184 struct PromotionCandidate { 185 Function *TargetFunction; 186 uint64_t Count; 187 188 PromotionCandidate(Function *F, uint64_t C) : TargetFunction(F), Count(C) {} 189 }; 190 191 // Check if the indirect-call call site should be promoted. Return the number 192 // of promotions. Inst is the candidate indirect call, ValueDataRef 193 // contains the array of value profile data for profiled targets, 194 // TotalCount is the total profiled count of call executions, and 195 // NumCandidates is the number of candidate entries in ValueDataRef. 196 std::vector<PromotionCandidate> getPromotionCandidatesForCallSite( 197 Instruction *Inst, const ArrayRef<InstrProfValueData> &ValueDataRef, 198 uint64_t TotalCount, uint32_t NumCandidates); 199 200 // Promote a list of targets for one indirect-call callsite. Return 201 // the number of promotions. 202 uint32_t tryToPromote(Instruction *Inst, 203 const std::vector<PromotionCandidate> &Candidates, 204 uint64_t &TotalCount); 205 206 public: 207 ICallPromotionFunc(Function &Func, Module *Modu, InstrProfSymtab *Symtab, 208 bool SamplePGO, OptimizationRemarkEmitter &ORE) 209 : F(Func), M(Modu), Symtab(Symtab), SamplePGO(SamplePGO), ORE(ORE) {} 210 ICallPromotionFunc(const ICallPromotionFunc &) = delete; 211 ICallPromotionFunc &operator=(const ICallPromotionFunc &) = delete; 212 213 bool processFunction(ProfileSummaryInfo *PSI); 214 }; 215 216 } // end anonymous namespace 217 218 // Indirect-call promotion heuristic. The direct targets are sorted based on 219 // the count. Stop at the first target that is not promoted. 220 std::vector<ICallPromotionFunc::PromotionCandidate> 221 ICallPromotionFunc::getPromotionCandidatesForCallSite( 222 Instruction *Inst, const ArrayRef<InstrProfValueData> &ValueDataRef, 223 uint64_t TotalCount, uint32_t NumCandidates) { 224 std::vector<PromotionCandidate> Ret; 225 226 LLVM_DEBUG(dbgs() << " \nWork on callsite #" << NumOfPGOICallsites << *Inst 227 << " Num_targets: " << ValueDataRef.size() 228 << " Num_candidates: " << NumCandidates << "\n"); 229 NumOfPGOICallsites++; 230 if (ICPCSSkip != 0 && NumOfPGOICallsites <= ICPCSSkip) { 231 LLVM_DEBUG(dbgs() << " Skip: User options.\n"); 232 return Ret; 233 } 234 235 for (uint32_t I = 0; I < NumCandidates; I++) { 236 uint64_t Count = ValueDataRef[I].Count; 237 assert(Count <= TotalCount); 238 uint64_t Target = ValueDataRef[I].Value; 239 LLVM_DEBUG(dbgs() << " Candidate " << I << " Count=" << Count 240 << " Target_func: " << Target << "\n"); 241 242 if (ICPInvokeOnly && dyn_cast<CallInst>(Inst)) { 243 LLVM_DEBUG(dbgs() << " Not promote: User options.\n"); 244 ORE.emit([&]() { 245 return OptimizationRemarkMissed(DEBUG_TYPE, "UserOptions", Inst) 246 << " Not promote: User options"; 247 }); 248 break; 249 } 250 if (ICPCallOnly && dyn_cast<InvokeInst>(Inst)) { 251 LLVM_DEBUG(dbgs() << " Not promote: User option.\n"); 252 ORE.emit([&]() { 253 return OptimizationRemarkMissed(DEBUG_TYPE, "UserOptions", Inst) 254 << " Not promote: User options"; 255 }); 256 break; 257 } 258 if (ICPCutOff != 0 && NumOfPGOICallPromotion >= ICPCutOff) { 259 LLVM_DEBUG(dbgs() << " Not promote: Cutoff reached.\n"); 260 ORE.emit([&]() { 261 return OptimizationRemarkMissed(DEBUG_TYPE, "CutOffReached", Inst) 262 << " Not promote: Cutoff reached"; 263 }); 264 break; 265 } 266 267 Function *TargetFunction = Symtab->getFunction(Target); 268 if (TargetFunction == nullptr) { 269 LLVM_DEBUG(dbgs() << " Not promote: Cannot find the target\n"); 270 ORE.emit([&]() { 271 return OptimizationRemarkMissed(DEBUG_TYPE, "UnableToFindTarget", Inst) 272 << "Cannot promote indirect call: target not found"; 273 }); 274 break; 275 } 276 277 const char *Reason = nullptr; 278 if (!isLegalToPromote(CallSite(Inst), TargetFunction, &Reason)) { 279 using namespace ore; 280 281 ORE.emit([&]() { 282 return OptimizationRemarkMissed(DEBUG_TYPE, "UnableToPromote", Inst) 283 << "Cannot promote indirect call to " 284 << NV("TargetFunction", TargetFunction) << " with count of " 285 << NV("Count", Count) << ": " << Reason; 286 }); 287 break; 288 } 289 290 Ret.push_back(PromotionCandidate(TargetFunction, Count)); 291 TotalCount -= Count; 292 } 293 return Ret; 294 } 295 296 Instruction *llvm::pgo::promoteIndirectCall(Instruction *Inst, 297 Function *DirectCallee, 298 uint64_t Count, uint64_t TotalCount, 299 bool AttachProfToDirectCall, 300 OptimizationRemarkEmitter *ORE) { 301 302 uint64_t ElseCount = TotalCount - Count; 303 uint64_t MaxCount = (Count >= ElseCount ? Count : ElseCount); 304 uint64_t Scale = calculateCountScale(MaxCount); 305 MDBuilder MDB(Inst->getContext()); 306 MDNode *BranchWeights = MDB.createBranchWeights( 307 scaleBranchCount(Count, Scale), scaleBranchCount(ElseCount, Scale)); 308 309 Instruction *NewInst = 310 promoteCallWithIfThenElse(CallSite(Inst), DirectCallee, BranchWeights); 311 312 if (AttachProfToDirectCall) { 313 SmallVector<uint32_t, 1> Weights; 314 Weights.push_back(Count); 315 MDBuilder MDB(NewInst->getContext()); 316 NewInst->setMetadata(LLVMContext::MD_prof, MDB.createBranchWeights(Weights)); 317 } 318 319 using namespace ore; 320 321 if (ORE) 322 ORE->emit([&]() { 323 return OptimizationRemark(DEBUG_TYPE, "Promoted", Inst) 324 << "Promote indirect call to " << NV("DirectCallee", DirectCallee) 325 << " with count " << NV("Count", Count) << " out of " 326 << NV("TotalCount", TotalCount); 327 }); 328 return NewInst; 329 } 330 331 // Promote indirect-call to conditional direct-call for one callsite. 332 uint32_t ICallPromotionFunc::tryToPromote( 333 Instruction *Inst, const std::vector<PromotionCandidate> &Candidates, 334 uint64_t &TotalCount) { 335 uint32_t NumPromoted = 0; 336 337 for (auto &C : Candidates) { 338 uint64_t Count = C.Count; 339 pgo::promoteIndirectCall(Inst, C.TargetFunction, Count, TotalCount, 340 SamplePGO, &ORE); 341 assert(TotalCount >= Count); 342 TotalCount -= Count; 343 NumOfPGOICallPromotion++; 344 NumPromoted++; 345 } 346 return NumPromoted; 347 } 348 349 // Traverse all the indirect-call callsite and get the value profile 350 // annotation to perform indirect-call promotion. 351 bool ICallPromotionFunc::processFunction(ProfileSummaryInfo *PSI) { 352 bool Changed = false; 353 ICallPromotionAnalysis ICallAnalysis; 354 for (auto &I : findIndirectCallSites(F)) { 355 uint32_t NumVals, NumCandidates; 356 uint64_t TotalCount; 357 auto ICallProfDataRef = ICallAnalysis.getPromotionCandidatesForInstruction( 358 I, NumVals, TotalCount, NumCandidates); 359 if (!NumCandidates || 360 (PSI && PSI->hasProfileSummary() && !PSI->isHotCount(TotalCount))) 361 continue; 362 auto PromotionCandidates = getPromotionCandidatesForCallSite( 363 I, ICallProfDataRef, TotalCount, NumCandidates); 364 uint32_t NumPromoted = tryToPromote(I, PromotionCandidates, TotalCount); 365 if (NumPromoted == 0) 366 continue; 367 368 Changed = true; 369 // Adjust the MD.prof metadata. First delete the old one. 370 I->setMetadata(LLVMContext::MD_prof, nullptr); 371 // If all promoted, we don't need the MD.prof metadata. 372 if (TotalCount == 0 || NumPromoted == NumVals) 373 continue; 374 // Otherwise we need update with the un-promoted records back. 375 annotateValueSite(*M, *I, ICallProfDataRef.slice(NumPromoted), TotalCount, 376 IPVK_IndirectCallTarget, NumCandidates); 377 } 378 return Changed; 379 } 380 381 // A wrapper function that does the actual work. 382 static bool promoteIndirectCalls(Module &M, ProfileSummaryInfo *PSI, 383 bool InLTO, bool SamplePGO, 384 ModuleAnalysisManager *AM = nullptr) { 385 if (DisableICP) 386 return false; 387 InstrProfSymtab Symtab; 388 if (Error E = Symtab.create(M, InLTO)) { 389 std::string SymtabFailure = toString(std::move(E)); 390 LLVM_DEBUG(dbgs() << "Failed to create symtab: " << SymtabFailure << "\n"); 391 (void)SymtabFailure; 392 return false; 393 } 394 bool Changed = false; 395 for (auto &F : M) { 396 if (F.isDeclaration()) 397 continue; 398 if (F.hasFnAttribute(Attribute::OptimizeNone)) 399 continue; 400 401 std::unique_ptr<OptimizationRemarkEmitter> OwnedORE; 402 OptimizationRemarkEmitter *ORE; 403 if (AM) { 404 auto &FAM = 405 AM->getResult<FunctionAnalysisManagerModuleProxy>(M).getManager(); 406 ORE = &FAM.getResult<OptimizationRemarkEmitterAnalysis>(F); 407 } else { 408 OwnedORE = llvm::make_unique<OptimizationRemarkEmitter>(&F); 409 ORE = OwnedORE.get(); 410 } 411 412 ICallPromotionFunc ICallPromotion(F, &M, &Symtab, SamplePGO, *ORE); 413 bool FuncChanged = ICallPromotion.processFunction(PSI); 414 if (ICPDUMPAFTER && FuncChanged) { 415 LLVM_DEBUG(dbgs() << "\n== IR Dump After =="; F.print(dbgs())); 416 LLVM_DEBUG(dbgs() << "\n"); 417 } 418 Changed |= FuncChanged; 419 if (ICPCutOff != 0 && NumOfPGOICallPromotion >= ICPCutOff) { 420 LLVM_DEBUG(dbgs() << " Stop: Cutoff reached.\n"); 421 break; 422 } 423 } 424 return Changed; 425 } 426 427 bool PGOIndirectCallPromotionLegacyPass::runOnModule(Module &M) { 428 ProfileSummaryInfo *PSI = 429 getAnalysis<ProfileSummaryInfoWrapperPass>().getPSI(); 430 431 // Command-line option has the priority for InLTO. 432 return promoteIndirectCalls(M, PSI, InLTO | ICPLTOMode, 433 SamplePGO | ICPSamplePGOMode); 434 } 435 436 PreservedAnalyses PGOIndirectCallPromotion::run(Module &M, 437 ModuleAnalysisManager &AM) { 438 ProfileSummaryInfo *PSI = &AM.getResult<ProfileSummaryAnalysis>(M); 439 440 if (!promoteIndirectCalls(M, PSI, InLTO | ICPLTOMode, 441 SamplePGO | ICPSamplePGOMode, &AM)) 442 return PreservedAnalyses::all(); 443 444 return PreservedAnalyses::none(); 445 } 446