1 //===- IndirectCallPromotion.cpp - Optimizations based on value profiling -===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 // 9 // This file implements the transformation that promotes indirect calls to 10 // conditional direct calls when the indirect-call value profile metadata is 11 // available. 12 // 13 //===----------------------------------------------------------------------===// 14 15 #include "llvm/ADT/ArrayRef.h" 16 #include "llvm/ADT/STLExtras.h" 17 #include "llvm/ADT/SmallVector.h" 18 #include "llvm/ADT/Statistic.h" 19 #include "llvm/ADT/StringRef.h" 20 #include "llvm/Analysis/IndirectCallPromotionAnalysis.h" 21 #include "llvm/Analysis/IndirectCallVisitor.h" 22 #include "llvm/Analysis/OptimizationRemarkEmitter.h" 23 #include "llvm/Analysis/ProfileSummaryInfo.h" 24 #include "llvm/IR/Attributes.h" 25 #include "llvm/IR/BasicBlock.h" 26 #include "llvm/IR/DerivedTypes.h" 27 #include "llvm/IR/DiagnosticInfo.h" 28 #include "llvm/IR/Function.h" 29 #include "llvm/IR/IRBuilder.h" 30 #include "llvm/IR/InstrTypes.h" 31 #include "llvm/IR/Instruction.h" 32 #include "llvm/IR/Instructions.h" 33 #include "llvm/IR/LLVMContext.h" 34 #include "llvm/IR/MDBuilder.h" 35 #include "llvm/IR/PassManager.h" 36 #include "llvm/IR/Type.h" 37 #include "llvm/IR/Value.h" 38 #include "llvm/InitializePasses.h" 39 #include "llvm/Pass.h" 40 #include "llvm/ProfileData/InstrProf.h" 41 #include "llvm/Support/Casting.h" 42 #include "llvm/Support/CommandLine.h" 43 #include "llvm/Support/Debug.h" 44 #include "llvm/Support/Error.h" 45 #include "llvm/Support/raw_ostream.h" 46 #include "llvm/Transforms/Instrumentation.h" 47 #include "llvm/Transforms/Instrumentation/PGOInstrumentation.h" 48 #include "llvm/Transforms/Utils/BasicBlockUtils.h" 49 #include "llvm/Transforms/Utils/CallPromotionUtils.h" 50 #include <cassert> 51 #include <cstdint> 52 #include <memory> 53 #include <string> 54 #include <utility> 55 #include <vector> 56 57 using namespace llvm; 58 59 #define DEBUG_TYPE "pgo-icall-prom" 60 61 STATISTIC(NumOfPGOICallPromotion, "Number of indirect call promotions."); 62 STATISTIC(NumOfPGOICallsites, "Number of indirect call candidate sites."); 63 64 // Command line option to disable indirect-call promotion with the default as 65 // false. This is for debug purpose. 66 static cl::opt<bool> DisableICP("disable-icp", cl::init(false), cl::Hidden, 67 cl::desc("Disable indirect call promotion")); 68 69 // Set the cutoff value for the promotion. If the value is other than 0, we 70 // stop the transformation once the total number of promotions equals the cutoff 71 // value. 72 // For debug use only. 73 static cl::opt<unsigned> 74 ICPCutOff("icp-cutoff", cl::init(0), cl::Hidden, cl::ZeroOrMore, 75 cl::desc("Max number of promotions for this compilation")); 76 77 // If ICPCSSkip is non zero, the first ICPCSSkip callsites will be skipped. 78 // For debug use only. 79 static cl::opt<unsigned> 80 ICPCSSkip("icp-csskip", cl::init(0), cl::Hidden, cl::ZeroOrMore, 81 cl::desc("Skip Callsite up to this number for this compilation")); 82 83 // Set if the pass is called in LTO optimization. The difference for LTO mode 84 // is the pass won't prefix the source module name to the internal linkage 85 // symbols. 86 static cl::opt<bool> ICPLTOMode("icp-lto", cl::init(false), cl::Hidden, 87 cl::desc("Run indirect-call promotion in LTO " 88 "mode")); 89 90 // Set if the pass is called in SamplePGO mode. The difference for SamplePGO 91 // mode is it will add prof metadatato the created direct call. 92 static cl::opt<bool> 93 ICPSamplePGOMode("icp-samplepgo", cl::init(false), cl::Hidden, 94 cl::desc("Run indirect-call promotion in SamplePGO mode")); 95 96 // If the option is set to true, only call instructions will be considered for 97 // transformation -- invoke instructions will be ignored. 98 static cl::opt<bool> 99 ICPCallOnly("icp-call-only", cl::init(false), cl::Hidden, 100 cl::desc("Run indirect-call promotion for call instructions " 101 "only")); 102 103 // If the option is set to true, only invoke instructions will be considered for 104 // transformation -- call instructions will be ignored. 105 static cl::opt<bool> ICPInvokeOnly("icp-invoke-only", cl::init(false), 106 cl::Hidden, 107 cl::desc("Run indirect-call promotion for " 108 "invoke instruction only")); 109 110 // Dump the function level IR if the transformation happened in this 111 // function. For debug use only. 112 static cl::opt<bool> 113 ICPDUMPAFTER("icp-dumpafter", cl::init(false), cl::Hidden, 114 cl::desc("Dump IR after transformation happens")); 115 116 namespace { 117 118 class PGOIndirectCallPromotionLegacyPass : public ModulePass { 119 public: 120 static char ID; 121 122 PGOIndirectCallPromotionLegacyPass(bool InLTO = false, bool SamplePGO = false) 123 : ModulePass(ID), InLTO(InLTO), SamplePGO(SamplePGO) { 124 initializePGOIndirectCallPromotionLegacyPassPass( 125 *PassRegistry::getPassRegistry()); 126 } 127 128 void getAnalysisUsage(AnalysisUsage &AU) const override { 129 AU.addRequired<ProfileSummaryInfoWrapperPass>(); 130 } 131 132 StringRef getPassName() const override { return "PGOIndirectCallPromotion"; } 133 134 private: 135 bool runOnModule(Module &M) override; 136 137 // If this pass is called in LTO. We need to special handling the PGOFuncName 138 // for the static variables due to LTO's internalization. 139 bool InLTO; 140 141 // If this pass is called in SamplePGO. We need to add the prof metadata to 142 // the promoted direct call. 143 bool SamplePGO; 144 }; 145 146 } // end anonymous namespace 147 148 char PGOIndirectCallPromotionLegacyPass::ID = 0; 149 150 INITIALIZE_PASS_BEGIN(PGOIndirectCallPromotionLegacyPass, "pgo-icall-prom", 151 "Use PGO instrumentation profile to promote indirect " 152 "calls to direct calls.", 153 false, false) 154 INITIALIZE_PASS_DEPENDENCY(ProfileSummaryInfoWrapperPass) 155 INITIALIZE_PASS_END(PGOIndirectCallPromotionLegacyPass, "pgo-icall-prom", 156 "Use PGO instrumentation profile to promote indirect " 157 "calls to direct calls.", 158 false, false) 159 160 ModulePass *llvm::createPGOIndirectCallPromotionLegacyPass(bool InLTO, 161 bool SamplePGO) { 162 return new PGOIndirectCallPromotionLegacyPass(InLTO, SamplePGO); 163 } 164 165 namespace { 166 167 // The class for main data structure to promote indirect calls to conditional 168 // direct calls. 169 class ICallPromotionFunc { 170 private: 171 Function &F; 172 Module *M; 173 174 // Symtab that maps indirect call profile values to function names and 175 // defines. 176 InstrProfSymtab *Symtab; 177 178 bool SamplePGO; 179 180 OptimizationRemarkEmitter &ORE; 181 182 // A struct that records the direct target and it's call count. 183 struct PromotionCandidate { 184 Function *TargetFunction; 185 uint64_t Count; 186 187 PromotionCandidate(Function *F, uint64_t C) : TargetFunction(F), Count(C) {} 188 }; 189 190 // Check if the indirect-call call site should be promoted. Return the number 191 // of promotions. Inst is the candidate indirect call, ValueDataRef 192 // contains the array of value profile data for profiled targets, 193 // TotalCount is the total profiled count of call executions, and 194 // NumCandidates is the number of candidate entries in ValueDataRef. 195 std::vector<PromotionCandidate> getPromotionCandidatesForCallSite( 196 const CallBase &CB, const ArrayRef<InstrProfValueData> &ValueDataRef, 197 uint64_t TotalCount, uint32_t NumCandidates); 198 199 // Promote a list of targets for one indirect-call callsite. Return 200 // the number of promotions. 201 uint32_t tryToPromote(CallBase &CB, 202 const std::vector<PromotionCandidate> &Candidates, 203 uint64_t &TotalCount); 204 205 public: 206 ICallPromotionFunc(Function &Func, Module *Modu, InstrProfSymtab *Symtab, 207 bool SamplePGO, OptimizationRemarkEmitter &ORE) 208 : F(Func), M(Modu), Symtab(Symtab), SamplePGO(SamplePGO), ORE(ORE) {} 209 ICallPromotionFunc(const ICallPromotionFunc &) = delete; 210 ICallPromotionFunc &operator=(const ICallPromotionFunc &) = delete; 211 212 bool processFunction(ProfileSummaryInfo *PSI); 213 }; 214 215 } // end anonymous namespace 216 217 // Indirect-call promotion heuristic. The direct targets are sorted based on 218 // the count. Stop at the first target that is not promoted. 219 std::vector<ICallPromotionFunc::PromotionCandidate> 220 ICallPromotionFunc::getPromotionCandidatesForCallSite( 221 const CallBase &CB, const ArrayRef<InstrProfValueData> &ValueDataRef, 222 uint64_t TotalCount, uint32_t NumCandidates) { 223 std::vector<PromotionCandidate> Ret; 224 225 LLVM_DEBUG(dbgs() << " \nWork on callsite #" << NumOfPGOICallsites << CB 226 << " Num_targets: " << ValueDataRef.size() 227 << " Num_candidates: " << NumCandidates << "\n"); 228 NumOfPGOICallsites++; 229 if (ICPCSSkip != 0 && NumOfPGOICallsites <= ICPCSSkip) { 230 LLVM_DEBUG(dbgs() << " Skip: User options.\n"); 231 return Ret; 232 } 233 234 for (uint32_t I = 0; I < NumCandidates; I++) { 235 uint64_t Count = ValueDataRef[I].Count; 236 assert(Count <= TotalCount); 237 uint64_t Target = ValueDataRef[I].Value; 238 LLVM_DEBUG(dbgs() << " Candidate " << I << " Count=" << Count 239 << " Target_func: " << Target << "\n"); 240 241 if (ICPInvokeOnly && isa<CallInst>(CB)) { 242 LLVM_DEBUG(dbgs() << " Not promote: User options.\n"); 243 ORE.emit([&]() { 244 return OptimizationRemarkMissed(DEBUG_TYPE, "UserOptions", &CB) 245 << " Not promote: User options"; 246 }); 247 break; 248 } 249 if (ICPCallOnly && isa<InvokeInst>(CB)) { 250 LLVM_DEBUG(dbgs() << " Not promote: User option.\n"); 251 ORE.emit([&]() { 252 return OptimizationRemarkMissed(DEBUG_TYPE, "UserOptions", &CB) 253 << " Not promote: User options"; 254 }); 255 break; 256 } 257 if (ICPCutOff != 0 && NumOfPGOICallPromotion >= ICPCutOff) { 258 LLVM_DEBUG(dbgs() << " Not promote: Cutoff reached.\n"); 259 ORE.emit([&]() { 260 return OptimizationRemarkMissed(DEBUG_TYPE, "CutOffReached", &CB) 261 << " Not promote: Cutoff reached"; 262 }); 263 break; 264 } 265 266 Function *TargetFunction = Symtab->getFunction(Target); 267 if (TargetFunction == nullptr) { 268 LLVM_DEBUG(dbgs() << " Not promote: Cannot find the target\n"); 269 ORE.emit([&]() { 270 return OptimizationRemarkMissed(DEBUG_TYPE, "UnableToFindTarget", &CB) 271 << "Cannot promote indirect call: target with md5sum " 272 << ore::NV("target md5sum", Target) << " not found"; 273 }); 274 break; 275 } 276 277 const char *Reason = nullptr; 278 if (!isLegalToPromote(CB, TargetFunction, &Reason)) { 279 using namespace ore; 280 281 ORE.emit([&]() { 282 return OptimizationRemarkMissed(DEBUG_TYPE, "UnableToPromote", &CB) 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 CallBase &llvm::pgo::promoteIndirectCall(CallBase &CB, Function *DirectCallee, 297 uint64_t Count, uint64_t TotalCount, 298 bool AttachProfToDirectCall, 299 OptimizationRemarkEmitter *ORE) { 300 301 uint64_t ElseCount = TotalCount - Count; 302 uint64_t MaxCount = (Count >= ElseCount ? Count : ElseCount); 303 uint64_t Scale = calculateCountScale(MaxCount); 304 MDBuilder MDB(CB.getContext()); 305 MDNode *BranchWeights = MDB.createBranchWeights( 306 scaleBranchCount(Count, Scale), scaleBranchCount(ElseCount, Scale)); 307 308 CallBase &NewInst = 309 promoteCallWithIfThenElse(CB, DirectCallee, BranchWeights); 310 311 if (AttachProfToDirectCall) { 312 MDBuilder MDB(NewInst.getContext()); 313 NewInst.setMetadata( 314 LLVMContext::MD_prof, 315 MDB.createBranchWeights({static_cast<uint32_t>(Count)})); 316 } 317 318 using namespace ore; 319 320 if (ORE) 321 ORE->emit([&]() { 322 return OptimizationRemark(DEBUG_TYPE, "Promoted", &CB) 323 << "Promote indirect call to " << NV("DirectCallee", DirectCallee) 324 << " with count " << NV("Count", Count) << " out of " 325 << NV("TotalCount", TotalCount); 326 }); 327 return NewInst; 328 } 329 330 // Promote indirect-call to conditional direct-call for one callsite. 331 uint32_t ICallPromotionFunc::tryToPromote( 332 CallBase &CB, const std::vector<PromotionCandidate> &Candidates, 333 uint64_t &TotalCount) { 334 uint32_t NumPromoted = 0; 335 336 for (auto &C : Candidates) { 337 uint64_t Count = C.Count; 338 pgo::promoteIndirectCall(CB, C.TargetFunction, Count, TotalCount, SamplePGO, 339 &ORE); 340 assert(TotalCount >= Count); 341 TotalCount -= Count; 342 NumOfPGOICallPromotion++; 343 NumPromoted++; 344 } 345 return NumPromoted; 346 } 347 348 // Traverse all the indirect-call callsite and get the value profile 349 // annotation to perform indirect-call promotion. 350 bool ICallPromotionFunc::processFunction(ProfileSummaryInfo *PSI) { 351 bool Changed = false; 352 ICallPromotionAnalysis ICallAnalysis; 353 for (auto *CB : findIndirectCalls(F)) { 354 uint32_t NumVals, NumCandidates; 355 uint64_t TotalCount; 356 auto ICallProfDataRef = ICallAnalysis.getPromotionCandidatesForInstruction( 357 CB, NumVals, TotalCount, NumCandidates); 358 if (!NumCandidates || 359 (PSI && PSI->hasProfileSummary() && !PSI->isHotCount(TotalCount))) 360 continue; 361 auto PromotionCandidates = getPromotionCandidatesForCallSite( 362 *CB, ICallProfDataRef, TotalCount, NumCandidates); 363 uint32_t NumPromoted = tryToPromote(*CB, PromotionCandidates, TotalCount); 364 if (NumPromoted == 0) 365 continue; 366 367 Changed = true; 368 // Adjust the MD.prof metadata. First delete the old one. 369 CB->setMetadata(LLVMContext::MD_prof, nullptr); 370 // If all promoted, we don't need the MD.prof metadata. 371 if (TotalCount == 0 || NumPromoted == NumVals) 372 continue; 373 // Otherwise we need update with the un-promoted records back. 374 annotateValueSite(*M, *CB, ICallProfDataRef.slice(NumPromoted), TotalCount, 375 IPVK_IndirectCallTarget, NumCandidates); 376 } 377 return Changed; 378 } 379 380 // A wrapper function that does the actual work. 381 static bool promoteIndirectCalls(Module &M, ProfileSummaryInfo *PSI, 382 bool InLTO, bool SamplePGO, 383 ModuleAnalysisManager *AM = nullptr) { 384 if (DisableICP) 385 return false; 386 InstrProfSymtab Symtab; 387 if (Error E = Symtab.create(M, InLTO)) { 388 std::string SymtabFailure = toString(std::move(E)); 389 LLVM_DEBUG(dbgs() << "Failed to create symtab: " << SymtabFailure << "\n"); 390 (void)SymtabFailure; 391 return false; 392 } 393 bool Changed = false; 394 for (auto &F : M) { 395 if (F.isDeclaration() || F.hasOptNone()) 396 continue; 397 398 std::unique_ptr<OptimizationRemarkEmitter> OwnedORE; 399 OptimizationRemarkEmitter *ORE; 400 if (AM) { 401 auto &FAM = 402 AM->getResult<FunctionAnalysisManagerModuleProxy>(M).getManager(); 403 ORE = &FAM.getResult<OptimizationRemarkEmitterAnalysis>(F); 404 } else { 405 OwnedORE = std::make_unique<OptimizationRemarkEmitter>(&F); 406 ORE = OwnedORE.get(); 407 } 408 409 ICallPromotionFunc ICallPromotion(F, &M, &Symtab, SamplePGO, *ORE); 410 bool FuncChanged = ICallPromotion.processFunction(PSI); 411 if (ICPDUMPAFTER && FuncChanged) { 412 LLVM_DEBUG(dbgs() << "\n== IR Dump After =="; F.print(dbgs())); 413 LLVM_DEBUG(dbgs() << "\n"); 414 } 415 Changed |= FuncChanged; 416 if (ICPCutOff != 0 && NumOfPGOICallPromotion >= ICPCutOff) { 417 LLVM_DEBUG(dbgs() << " Stop: Cutoff reached.\n"); 418 break; 419 } 420 } 421 return Changed; 422 } 423 424 bool PGOIndirectCallPromotionLegacyPass::runOnModule(Module &M) { 425 ProfileSummaryInfo *PSI = 426 &getAnalysis<ProfileSummaryInfoWrapperPass>().getPSI(); 427 428 // Command-line option has the priority for InLTO. 429 return promoteIndirectCalls(M, PSI, InLTO | ICPLTOMode, 430 SamplePGO | ICPSamplePGOMode); 431 } 432 433 PreservedAnalyses PGOIndirectCallPromotion::run(Module &M, 434 ModuleAnalysisManager &AM) { 435 ProfileSummaryInfo *PSI = &AM.getResult<ProfileSummaryAnalysis>(M); 436 437 if (!promoteIndirectCalls(M, PSI, InLTO | ICPLTOMode, 438 SamplePGO | ICPSamplePGOMode, &AM)) 439 return PreservedAnalyses::all(); 440 441 return PreservedAnalyses::none(); 442 } 443