1 //===- bolt/Passes/IndirectCallPromotion.cpp ------------------------------===// 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 IndirectCallPromotion class. 10 // 11 //===----------------------------------------------------------------------===// 12 13 #include "bolt/Passes/IndirectCallPromotion.h" 14 #include "bolt/Passes/BinaryFunctionCallGraph.h" 15 #include "bolt/Passes/DataflowInfoManager.h" 16 #include "bolt/Passes/Inliner.h" 17 #include "llvm/ADT/STLExtras.h" 18 #include "llvm/Support/CommandLine.h" 19 #include <iterator> 20 21 #define DEBUG_TYPE "ICP" 22 #define DEBUG_VERBOSE(Level, X) \ 23 if (opts::Verbosity >= (Level)) { \ 24 X; \ 25 } 26 27 using namespace llvm; 28 using namespace bolt; 29 30 namespace opts { 31 32 extern cl::OptionCategory BoltOptCategory; 33 34 extern cl::opt<IndirectCallPromotionType> ICP; 35 extern cl::opt<unsigned> Verbosity; 36 extern cl::opt<unsigned> ExecutionCountThreshold; 37 38 static cl::opt<unsigned> ICPJTRemainingPercentThreshold( 39 "icp-jt-remaining-percent-threshold", 40 cl::desc("The percentage threshold against remaining unpromoted indirect " 41 "call count for the promotion for jump tables"), 42 cl::init(30), cl::ZeroOrMore, cl::Hidden, cl::cat(BoltOptCategory)); 43 44 static cl::opt<unsigned> ICPJTTotalPercentThreshold( 45 "icp-jt-total-percent-threshold", 46 cl::desc( 47 "The percentage threshold against total count for the promotion for " 48 "jump tables"), 49 cl::init(5), cl::Hidden, cl::cat(BoltOptCategory)); 50 51 static cl::opt<unsigned> ICPCallsRemainingPercentThreshold( 52 "icp-calls-remaining-percent-threshold", 53 cl::desc("The percentage threshold against remaining unpromoted indirect " 54 "call count for the promotion for calls"), 55 cl::init(50), cl::Hidden, cl::cat(BoltOptCategory)); 56 57 static cl::opt<unsigned> ICPCallsTotalPercentThreshold( 58 "icp-calls-total-percent-threshold", 59 cl::desc( 60 "The percentage threshold against total count for the promotion for " 61 "calls"), 62 cl::init(30), cl::Hidden, cl::cat(BoltOptCategory)); 63 64 static cl::opt<unsigned> ICPMispredictThreshold( 65 "indirect-call-promotion-mispredict-threshold", 66 cl::desc("misprediction threshold for skipping ICP on an " 67 "indirect call"), 68 cl::init(0), cl::cat(BoltOptCategory)); 69 70 static cl::alias ICPMispredictThresholdAlias( 71 "icp-mp-threshold", 72 cl::desc("alias for --indirect-call-promotion-mispredict-threshold"), 73 cl::aliasopt(ICPMispredictThreshold)); 74 75 static cl::opt<bool> ICPUseMispredicts( 76 "indirect-call-promotion-use-mispredicts", 77 cl::desc("use misprediction frequency for determining whether or not ICP " 78 "should be applied at a callsite. The " 79 "-indirect-call-promotion-mispredict-threshold value will be used " 80 "by this heuristic"), 81 cl::cat(BoltOptCategory)); 82 83 static cl::alias ICPUseMispredictsAlias( 84 "icp-use-mp", 85 cl::desc("alias for --indirect-call-promotion-use-mispredicts"), 86 cl::aliasopt(ICPUseMispredicts)); 87 88 static cl::opt<unsigned> 89 ICPTopN("indirect-call-promotion-topn", 90 cl::desc("limit number of targets to consider when doing indirect " 91 "call promotion. 0 = no limit"), 92 cl::init(3), cl::cat(BoltOptCategory)); 93 94 static cl::alias 95 ICPTopNAlias("icp-topn", 96 cl::desc("alias for --indirect-call-promotion-topn"), 97 cl::aliasopt(ICPTopN)); 98 99 static cl::opt<unsigned> ICPCallsTopN( 100 "indirect-call-promotion-calls-topn", 101 cl::desc("limit number of targets to consider when doing indirect " 102 "call promotion on calls. 0 = no limit"), 103 cl::init(0), cl::cat(BoltOptCategory)); 104 105 static cl::alias ICPCallsTopNAlias( 106 "icp-calls-topn", 107 cl::desc("alias for --indirect-call-promotion-calls-topn"), 108 cl::aliasopt(ICPCallsTopN)); 109 110 static cl::opt<unsigned> ICPJumpTablesTopN( 111 "indirect-call-promotion-jump-tables-topn", 112 cl::desc("limit number of targets to consider when doing indirect " 113 "call promotion on jump tables. 0 = no limit"), 114 cl::init(0), cl::cat(BoltOptCategory)); 115 116 static cl::alias ICPJumpTablesTopNAlias( 117 "icp-jt-topn", 118 cl::desc("alias for --indirect-call-promotion-jump-tables-topn"), 119 cl::aliasopt(ICPJumpTablesTopN)); 120 121 static cl::opt<bool> EliminateLoads( 122 "icp-eliminate-loads", 123 cl::desc("enable load elimination using memory profiling data when " 124 "performing ICP"), 125 cl::init(true), cl::cat(BoltOptCategory)); 126 127 static cl::opt<unsigned> ICPTopCallsites( 128 "icp-top-callsites", 129 cl::desc("optimize hottest calls until at least this percentage of all " 130 "indirect calls frequency is covered. 0 = all callsites"), 131 cl::init(99), cl::Hidden, cl::cat(BoltOptCategory)); 132 133 static cl::list<std::string> 134 ICPFuncsList("icp-funcs", cl::CommaSeparated, 135 cl::desc("list of functions to enable ICP for"), 136 cl::value_desc("func1,func2,func3,..."), cl::Hidden, 137 cl::cat(BoltOptCategory)); 138 139 static cl::opt<bool> 140 ICPOldCodeSequence("icp-old-code-sequence", 141 cl::desc("use old code sequence for promoted calls"), 142 cl::Hidden, cl::cat(BoltOptCategory)); 143 144 static cl::opt<bool> ICPJumpTablesByTarget( 145 "icp-jump-tables-targets", 146 cl::desc( 147 "for jump tables, optimize indirect jmp targets instead of indices"), 148 cl::Hidden, cl::cat(BoltOptCategory)); 149 150 static cl::alias 151 ICPJumpTablesByTargetAlias("icp-jt-targets", 152 cl::desc("alias for --icp-jump-tables-targets"), 153 cl::aliasopt(ICPJumpTablesByTarget)); 154 155 static cl::opt<bool> ICPPeelForInline( 156 "icp-inline", cl::desc("only promote call targets eligible for inlining"), 157 cl::Hidden, cl::cat(BoltOptCategory)); 158 159 } // namespace opts 160 161 #ifndef NDEBUG 162 static bool verifyProfile(std::map<uint64_t, BinaryFunction> &BFs) { 163 bool IsValid = true; 164 for (auto &BFI : BFs) { 165 BinaryFunction &BF = BFI.second; 166 if (!BF.isSimple()) 167 continue; 168 for (const BinaryBasicBlock &BB : BF) { 169 auto BI = BB.branch_info_begin(); 170 for (BinaryBasicBlock *SuccBB : BB.successors()) { 171 if (BI->Count != BinaryBasicBlock::COUNT_NO_PROFILE && BI->Count > 0) { 172 if (BB.getKnownExecutionCount() == 0 || 173 SuccBB->getKnownExecutionCount() == 0) { 174 errs() << "BOLT-WARNING: profile verification failed after ICP for " 175 "function " 176 << BF << '\n'; 177 IsValid = false; 178 } 179 } 180 ++BI; 181 } 182 } 183 } 184 return IsValid; 185 } 186 #endif 187 188 namespace llvm { 189 namespace bolt { 190 191 IndirectCallPromotion::Callsite::Callsite(BinaryFunction &BF, 192 const IndirectCallProfile &ICP) 193 : From(BF.getSymbol()), To(ICP.Offset), Mispreds(ICP.Mispreds), 194 Branches(ICP.Count) { 195 if (ICP.Symbol) { 196 To.Sym = ICP.Symbol; 197 To.Addr = 0; 198 } 199 } 200 201 void IndirectCallPromotion::printDecision( 202 llvm::raw_ostream &OS, 203 std::vector<IndirectCallPromotion::Callsite> &Targets, unsigned N) const { 204 uint64_t TotalCount = 0; 205 uint64_t TotalMispreds = 0; 206 for (const Callsite &S : Targets) { 207 TotalCount += S.Branches; 208 TotalMispreds += S.Mispreds; 209 } 210 if (!TotalCount) 211 TotalCount = 1; 212 if (!TotalMispreds) 213 TotalMispreds = 1; 214 215 OS << "BOLT-INFO: ICP decision for call site with " << Targets.size() 216 << " targets, Count = " << TotalCount << ", Mispreds = " << TotalMispreds 217 << "\n"; 218 219 size_t I = 0; 220 for (const Callsite &S : Targets) { 221 OS << "Count = " << S.Branches << ", " 222 << format("%.1f", (100.0 * S.Branches) / TotalCount) << ", " 223 << "Mispreds = " << S.Mispreds << ", " 224 << format("%.1f", (100.0 * S.Mispreds) / TotalMispreds); 225 if (I < N) 226 OS << " * to be optimized *"; 227 if (!S.JTIndices.empty()) { 228 OS << " Indices:"; 229 for (const uint64_t Idx : S.JTIndices) 230 OS << " " << Idx; 231 } 232 OS << "\n"; 233 I += S.JTIndices.empty() ? 1 : S.JTIndices.size(); 234 } 235 } 236 237 // Get list of targets for a given call sorted by most frequently 238 // called first. 239 std::vector<IndirectCallPromotion::Callsite> 240 IndirectCallPromotion::getCallTargets(BinaryBasicBlock &BB, 241 const MCInst &Inst) const { 242 BinaryFunction &BF = *BB.getFunction(); 243 const BinaryContext &BC = BF.getBinaryContext(); 244 std::vector<Callsite> Targets; 245 246 if (const JumpTable *JT = BF.getJumpTable(Inst)) { 247 // Don't support PIC jump tables for now 248 if (!opts::ICPJumpTablesByTarget && JT->Type == JumpTable::JTT_PIC) 249 return Targets; 250 const Location From(BF.getSymbol()); 251 const std::pair<size_t, size_t> Range = 252 JT->getEntriesForAddress(BC.MIB->getJumpTable(Inst)); 253 assert(JT->Counts.empty() || JT->Counts.size() >= Range.second); 254 JumpTable::JumpInfo DefaultJI; 255 const JumpTable::JumpInfo *JI = 256 JT->Counts.empty() ? &DefaultJI : &JT->Counts[Range.first]; 257 const size_t JIAdj = JT->Counts.empty() ? 0 : 1; 258 assert(JT->Type == JumpTable::JTT_PIC || 259 JT->EntrySize == BC.AsmInfo->getCodePointerSize()); 260 for (size_t I = Range.first; I < Range.second; ++I, JI += JIAdj) { 261 MCSymbol *Entry = JT->Entries[I]; 262 const BinaryBasicBlock *ToBB = BF.getBasicBlockForLabel(Entry); 263 assert(ToBB || Entry == BF.getFunctionEndLabel() || 264 Entry == BF.getFunctionEndLabel(FragmentNum::cold())); 265 if (Entry == BF.getFunctionEndLabel() || 266 Entry == BF.getFunctionEndLabel(FragmentNum::cold())) 267 continue; 268 const Location To(Entry); 269 const BinaryBasicBlock::BinaryBranchInfo &BI = BB.getBranchInfo(*ToBB); 270 Targets.emplace_back(From, To, BI.MispredictedCount, BI.Count, 271 I - Range.first); 272 } 273 274 // Sort by symbol then addr. 275 llvm::sort(Targets, [](const Callsite &A, const Callsite &B) { 276 if (A.To.Sym && B.To.Sym) 277 return A.To.Sym < B.To.Sym; 278 else if (A.To.Sym && !B.To.Sym) 279 return true; 280 else if (!A.To.Sym && B.To.Sym) 281 return false; 282 else 283 return A.To.Addr < B.To.Addr; 284 }); 285 286 // Targets may contain multiple entries to the same target, but using 287 // different indices. Their profile will report the same number of branches 288 // for different indices if the target is the same. That's because we don't 289 // profile the index value, but only the target via LBR. 290 auto First = Targets.begin(); 291 auto Last = Targets.end(); 292 auto Result = First; 293 while (++First != Last) { 294 Callsite &A = *Result; 295 const Callsite &B = *First; 296 if (A.To.Sym && B.To.Sym && A.To.Sym == B.To.Sym) 297 A.JTIndices.insert(A.JTIndices.end(), B.JTIndices.begin(), 298 B.JTIndices.end()); 299 else 300 *(++Result) = *First; 301 } 302 ++Result; 303 304 LLVM_DEBUG(if (Targets.end() - Result > 0) { 305 dbgs() << "BOLT-INFO: ICP: " << (Targets.end() - Result) 306 << " duplicate targets removed\n"; 307 }); 308 309 Targets.erase(Result, Targets.end()); 310 } else { 311 // Don't try to optimize PC relative indirect calls. 312 if (Inst.getOperand(0).isReg() && 313 Inst.getOperand(0).getReg() == BC.MRI->getProgramCounter()) 314 return Targets; 315 316 const auto ICSP = BC.MIB->tryGetAnnotationAs<IndirectCallSiteProfile>( 317 Inst, "CallProfile"); 318 if (ICSP) { 319 for (const IndirectCallProfile &CSP : ICSP.get()) { 320 Callsite Site(BF, CSP); 321 if (Site.isValid()) 322 Targets.emplace_back(std::move(Site)); 323 } 324 } 325 } 326 327 // Sort by target count, number of indices in case of jump table, and 328 // mispredicts. We prioritize targets with high count, small number of indices 329 // and high mispredicts. Break ties by selecting targets with lower addresses. 330 llvm::stable_sort(Targets, [](const Callsite &A, const Callsite &B) { 331 if (A.Branches != B.Branches) 332 return A.Branches > B.Branches; 333 if (A.JTIndices.size() != B.JTIndices.size()) 334 return A.JTIndices.size() < B.JTIndices.size(); 335 if (A.Mispreds != B.Mispreds) 336 return A.Mispreds > B.Mispreds; 337 return A.To.Addr < B.To.Addr; 338 }); 339 340 // Remove non-symbol targets 341 llvm::erase_if(Targets, [](const Callsite &CS) { return !CS.To.Sym; }); 342 343 LLVM_DEBUG(if (BF.getJumpTable(Inst)) { 344 uint64_t TotalCount = 0; 345 uint64_t TotalMispreds = 0; 346 for (const Callsite &S : Targets) { 347 TotalCount += S.Branches; 348 TotalMispreds += S.Mispreds; 349 } 350 if (!TotalCount) 351 TotalCount = 1; 352 if (!TotalMispreds) 353 TotalMispreds = 1; 354 355 dbgs() << "BOLT-INFO: ICP: jump table size = " << Targets.size() 356 << ", Count = " << TotalCount << ", Mispreds = " << TotalMispreds 357 << "\n"; 358 359 size_t I = 0; 360 for (const Callsite &S : Targets) { 361 dbgs() << "Count[" << I << "] = " << S.Branches << ", " 362 << format("%.1f", (100.0 * S.Branches) / TotalCount) << ", " 363 << "Mispreds[" << I << "] = " << S.Mispreds << ", " 364 << format("%.1f", (100.0 * S.Mispreds) / TotalMispreds) << "\n"; 365 ++I; 366 } 367 }); 368 369 return Targets; 370 } 371 372 IndirectCallPromotion::JumpTableInfoType 373 IndirectCallPromotion::maybeGetHotJumpTableTargets(BinaryBasicBlock &BB, 374 MCInst &CallInst, 375 MCInst *&TargetFetchInst, 376 const JumpTable *JT) const { 377 assert(JT && "Can't get jump table addrs for non-jump tables."); 378 379 BinaryFunction &Function = *BB.getFunction(); 380 BinaryContext &BC = Function.getBinaryContext(); 381 382 if (!Function.hasMemoryProfile() || !opts::EliminateLoads) 383 return JumpTableInfoType(); 384 385 JumpTableInfoType HotTargets; 386 MCInst *MemLocInstr; 387 MCInst *PCRelBaseOut; 388 unsigned BaseReg, IndexReg; 389 int64_t DispValue; 390 const MCExpr *DispExpr; 391 MutableArrayRef<MCInst> Insts(&BB.front(), &CallInst); 392 const IndirectBranchType Type = BC.MIB->analyzeIndirectBranch( 393 CallInst, Insts.begin(), Insts.end(), BC.AsmInfo->getCodePointerSize(), 394 MemLocInstr, BaseReg, IndexReg, DispValue, DispExpr, PCRelBaseOut); 395 396 assert(MemLocInstr && "There should always be a load for jump tables"); 397 if (!MemLocInstr) 398 return JumpTableInfoType(); 399 400 LLVM_DEBUG({ 401 dbgs() << "BOLT-INFO: ICP attempting to find memory profiling data for " 402 << "jump table in " << Function << " at @ " 403 << (&CallInst - &BB.front()) << "\n" 404 << "BOLT-INFO: ICP target fetch instructions:\n"; 405 BC.printInstruction(dbgs(), *MemLocInstr, 0, &Function); 406 if (MemLocInstr != &CallInst) 407 BC.printInstruction(dbgs(), CallInst, 0, &Function); 408 }); 409 410 DEBUG_VERBOSE(1, { 411 dbgs() << "Jmp info: Type = " << (unsigned)Type << ", " 412 << "BaseReg = " << BC.MRI->getName(BaseReg) << ", " 413 << "IndexReg = " << BC.MRI->getName(IndexReg) << ", " 414 << "DispValue = " << Twine::utohexstr(DispValue) << ", " 415 << "DispExpr = " << DispExpr << ", " 416 << "MemLocInstr = "; 417 BC.printInstruction(dbgs(), *MemLocInstr, 0, &Function); 418 dbgs() << "\n"; 419 }); 420 421 ++TotalIndexBasedCandidates; 422 423 auto ErrorOrMemAccessProfile = 424 BC.MIB->tryGetAnnotationAs<MemoryAccessProfile>(*MemLocInstr, 425 "MemoryAccessProfile"); 426 if (!ErrorOrMemAccessProfile) { 427 DEBUG_VERBOSE(1, dbgs() 428 << "BOLT-INFO: ICP no memory profiling data found\n"); 429 return JumpTableInfoType(); 430 } 431 MemoryAccessProfile &MemAccessProfile = ErrorOrMemAccessProfile.get(); 432 433 uint64_t ArrayStart; 434 if (DispExpr) { 435 ErrorOr<uint64_t> DispValueOrError = 436 BC.getSymbolValue(*BC.MIB->getTargetSymbol(DispExpr)); 437 assert(DispValueOrError && "global symbol needs a value"); 438 ArrayStart = *DispValueOrError; 439 } else { 440 ArrayStart = static_cast<uint64_t>(DispValue); 441 } 442 443 if (BaseReg == BC.MRI->getProgramCounter()) 444 ArrayStart += Function.getAddress() + MemAccessProfile.NextInstrOffset; 445 446 // This is a map of [symbol] -> [count, index] and is used to combine indices 447 // into the jump table since there may be multiple addresses that all have the 448 // same entry. 449 std::map<MCSymbol *, std::pair<uint64_t, uint64_t>> HotTargetMap; 450 const std::pair<size_t, size_t> Range = JT->getEntriesForAddress(ArrayStart); 451 452 for (const AddressAccess &AccessInfo : MemAccessProfile.AddressAccessInfo) { 453 size_t Index; 454 // Mem data occasionally includes nullprs, ignore them. 455 if (!AccessInfo.MemoryObject && !AccessInfo.Offset) 456 continue; 457 458 if (AccessInfo.Offset % JT->EntrySize != 0) // ignore bogus data 459 return JumpTableInfoType(); 460 461 if (AccessInfo.MemoryObject) { 462 // Deal with bad/stale data 463 if (!AccessInfo.MemoryObject->getName().starts_with( 464 "JUMP_TABLE/" + Function.getOneName().str())) 465 return JumpTableInfoType(); 466 Index = 467 (AccessInfo.Offset - (ArrayStart - JT->getAddress())) / JT->EntrySize; 468 } else { 469 Index = (AccessInfo.Offset - ArrayStart) / JT->EntrySize; 470 } 471 472 // If Index is out of range it probably means the memory profiling data is 473 // wrong for this instruction, bail out. 474 if (Index >= Range.second) { 475 LLVM_DEBUG(dbgs() << "BOLT-INFO: Index out of range of " << Range.first 476 << ", " << Range.second << "\n"); 477 return JumpTableInfoType(); 478 } 479 480 // Make sure the hot index points at a legal label corresponding to a BB, 481 // e.g. not the end of function (unreachable) label. 482 if (!Function.getBasicBlockForLabel(JT->Entries[Index + Range.first])) { 483 LLVM_DEBUG({ 484 dbgs() << "BOLT-INFO: hot index " << Index << " pointing at bogus " 485 << "label " << JT->Entries[Index + Range.first]->getName() 486 << " in jump table:\n"; 487 JT->print(dbgs()); 488 dbgs() << "HotTargetMap:\n"; 489 for (std::pair<MCSymbol *const, std::pair<uint64_t, uint64_t>> &HT : 490 HotTargetMap) 491 dbgs() << "BOLT-INFO: " << HT.first->getName() 492 << " = (count=" << HT.second.first 493 << ", index=" << HT.second.second << ")\n"; 494 }); 495 return JumpTableInfoType(); 496 } 497 498 std::pair<uint64_t, uint64_t> &HotTarget = 499 HotTargetMap[JT->Entries[Index + Range.first]]; 500 HotTarget.first += AccessInfo.Count; 501 HotTarget.second = Index; 502 } 503 504 llvm::copy(llvm::make_second_range(HotTargetMap), 505 std::back_inserter(HotTargets)); 506 507 // Sort with highest counts first. 508 llvm::sort(reverse(HotTargets)); 509 510 LLVM_DEBUG({ 511 dbgs() << "BOLT-INFO: ICP jump table hot targets:\n"; 512 for (const std::pair<uint64_t, uint64_t> &Target : HotTargets) 513 dbgs() << "BOLT-INFO: Idx = " << Target.second << ", " 514 << "Count = " << Target.first << "\n"; 515 }); 516 517 BC.MIB->getOrCreateAnnotationAs<uint16_t>(CallInst, "JTIndexReg") = IndexReg; 518 519 TargetFetchInst = MemLocInstr; 520 521 return HotTargets; 522 } 523 524 IndirectCallPromotion::SymTargetsType 525 IndirectCallPromotion::findCallTargetSymbols(std::vector<Callsite> &Targets, 526 size_t &N, BinaryBasicBlock &BB, 527 MCInst &CallInst, 528 MCInst *&TargetFetchInst) const { 529 const JumpTable *JT = BB.getFunction()->getJumpTable(CallInst); 530 SymTargetsType SymTargets; 531 532 if (!JT) { 533 for (size_t I = 0; I < N; ++I) { 534 assert(Targets[I].To.Sym && "All ICP targets must be to known symbols"); 535 assert(Targets[I].JTIndices.empty() && 536 "Can't have jump table indices for non-jump tables"); 537 SymTargets.emplace_back(Targets[I].To.Sym, 0); 538 } 539 return SymTargets; 540 } 541 542 // Use memory profile to select hot targets. 543 JumpTableInfoType HotTargets = 544 maybeGetHotJumpTableTargets(BB, CallInst, TargetFetchInst, JT); 545 546 auto findTargetsIndex = [&](uint64_t JTIndex) { 547 for (size_t I = 0; I < Targets.size(); ++I) 548 if (llvm::is_contained(Targets[I].JTIndices, JTIndex)) 549 return I; 550 LLVM_DEBUG(dbgs() << "BOLT-ERROR: Unable to find target index for hot jump " 551 << " table entry in " << *BB.getFunction() << "\n"); 552 llvm_unreachable("Hot indices must be referred to by at least one " 553 "callsite"); 554 }; 555 556 if (!HotTargets.empty()) { 557 if (opts::Verbosity >= 1) 558 for (size_t I = 0; I < HotTargets.size(); ++I) 559 outs() << "BOLT-INFO: HotTarget[" << I << "] = (" << HotTargets[I].first 560 << ", " << HotTargets[I].second << ")\n"; 561 562 // Recompute hottest targets, now discriminating which index is hot 563 // NOTE: This is a tradeoff. On one hand, we get index information. On the 564 // other hand, info coming from the memory profile is much less accurate 565 // than LBRs. So we may actually end up working with more coarse 566 // profile granularity in exchange for information about indices. 567 std::vector<Callsite> NewTargets; 568 std::map<const MCSymbol *, uint32_t> IndicesPerTarget; 569 uint64_t TotalMemAccesses = 0; 570 for (size_t I = 0; I < HotTargets.size(); ++I) { 571 const uint64_t TargetIndex = findTargetsIndex(HotTargets[I].second); 572 ++IndicesPerTarget[Targets[TargetIndex].To.Sym]; 573 TotalMemAccesses += HotTargets[I].first; 574 } 575 uint64_t RemainingMemAccesses = TotalMemAccesses; 576 const size_t TopN = 577 opts::ICPJumpTablesTopN ? opts::ICPJumpTablesTopN : opts::ICPTopN; 578 size_t I = 0; 579 for (; I < HotTargets.size(); ++I) { 580 const uint64_t MemAccesses = HotTargets[I].first; 581 if (100 * MemAccesses < 582 TotalMemAccesses * opts::ICPJTTotalPercentThreshold) 583 break; 584 if (100 * MemAccesses < 585 RemainingMemAccesses * opts::ICPJTRemainingPercentThreshold) 586 break; 587 if (TopN && I >= TopN) 588 break; 589 RemainingMemAccesses -= MemAccesses; 590 591 const uint64_t JTIndex = HotTargets[I].second; 592 Callsite &Target = Targets[findTargetsIndex(JTIndex)]; 593 594 NewTargets.push_back(Target); 595 std::vector<uint64_t>({JTIndex}).swap(NewTargets.back().JTIndices); 596 llvm::erase(Target.JTIndices, JTIndex); 597 598 // Keep fixCFG counts sane if more indices use this same target later 599 assert(IndicesPerTarget[Target.To.Sym] > 0 && "wrong map"); 600 NewTargets.back().Branches = 601 Target.Branches / IndicesPerTarget[Target.To.Sym]; 602 NewTargets.back().Mispreds = 603 Target.Mispreds / IndicesPerTarget[Target.To.Sym]; 604 assert(Target.Branches >= NewTargets.back().Branches); 605 assert(Target.Mispreds >= NewTargets.back().Mispreds); 606 Target.Branches -= NewTargets.back().Branches; 607 Target.Mispreds -= NewTargets.back().Mispreds; 608 } 609 llvm::copy(Targets, std::back_inserter(NewTargets)); 610 std::swap(NewTargets, Targets); 611 N = I; 612 613 if (N == 0 && opts::Verbosity >= 1) { 614 outs() << "BOLT-INFO: ICP failed in " << *BB.getFunction() << " in " 615 << BB.getName() << ": failed to meet thresholds after memory " 616 << "profile data was loaded.\n"; 617 return SymTargets; 618 } 619 } 620 621 for (size_t I = 0, TgtIdx = 0; I < N; ++TgtIdx) { 622 Callsite &Target = Targets[TgtIdx]; 623 assert(Target.To.Sym && "All ICP targets must be to known symbols"); 624 assert(!Target.JTIndices.empty() && "Jump tables must have indices"); 625 for (uint64_t Idx : Target.JTIndices) { 626 SymTargets.emplace_back(Target.To.Sym, Idx); 627 ++I; 628 } 629 } 630 631 return SymTargets; 632 } 633 634 IndirectCallPromotion::MethodInfoType IndirectCallPromotion::maybeGetVtableSyms( 635 BinaryBasicBlock &BB, MCInst &Inst, 636 const SymTargetsType &SymTargets) const { 637 BinaryFunction &Function = *BB.getFunction(); 638 BinaryContext &BC = Function.getBinaryContext(); 639 std::vector<std::pair<MCSymbol *, uint64_t>> VtableSyms; 640 std::vector<MCInst *> MethodFetchInsns; 641 unsigned VtableReg, MethodReg; 642 uint64_t MethodOffset; 643 644 assert(!Function.getJumpTable(Inst) && 645 "Can't get vtable addrs for jump tables."); 646 647 if (!Function.hasMemoryProfile() || !opts::EliminateLoads) 648 return MethodInfoType(); 649 650 MutableArrayRef<MCInst> Insts(&BB.front(), &Inst + 1); 651 if (!BC.MIB->analyzeVirtualMethodCall(Insts.begin(), Insts.end(), 652 MethodFetchInsns, VtableReg, MethodReg, 653 MethodOffset)) { 654 DEBUG_VERBOSE( 655 1, dbgs() << "BOLT-INFO: ICP unable to analyze method call in " 656 << Function << " at @ " << (&Inst - &BB.front()) << "\n"); 657 return MethodInfoType(); 658 } 659 660 ++TotalMethodLoadEliminationCandidates; 661 662 DEBUG_VERBOSE(1, { 663 dbgs() << "BOLT-INFO: ICP found virtual method call in " << Function 664 << " at @ " << (&Inst - &BB.front()) << "\n"; 665 dbgs() << "BOLT-INFO: ICP method fetch instructions:\n"; 666 for (MCInst *Inst : MethodFetchInsns) 667 BC.printInstruction(dbgs(), *Inst, 0, &Function); 668 669 if (MethodFetchInsns.back() != &Inst) 670 BC.printInstruction(dbgs(), Inst, 0, &Function); 671 }); 672 673 // Try to get value profiling data for the method load instruction. 674 auto ErrorOrMemAccessProfile = 675 BC.MIB->tryGetAnnotationAs<MemoryAccessProfile>(*MethodFetchInsns.back(), 676 "MemoryAccessProfile"); 677 if (!ErrorOrMemAccessProfile) { 678 DEBUG_VERBOSE(1, dbgs() 679 << "BOLT-INFO: ICP no memory profiling data found\n"); 680 return MethodInfoType(); 681 } 682 MemoryAccessProfile &MemAccessProfile = ErrorOrMemAccessProfile.get(); 683 684 // Find the vtable that each method belongs to. 685 std::map<const MCSymbol *, uint64_t> MethodToVtable; 686 687 for (const AddressAccess &AccessInfo : MemAccessProfile.AddressAccessInfo) { 688 uint64_t Address = AccessInfo.Offset; 689 if (AccessInfo.MemoryObject) 690 Address += AccessInfo.MemoryObject->getAddress(); 691 692 // Ignore bogus data. 693 if (!Address) 694 continue; 695 696 const uint64_t VtableBase = Address - MethodOffset; 697 698 DEBUG_VERBOSE(1, dbgs() << "BOLT-INFO: ICP vtable = " 699 << Twine::utohexstr(VtableBase) << "+" 700 << MethodOffset << "/" << AccessInfo.Count << "\n"); 701 702 if (ErrorOr<uint64_t> MethodAddr = BC.getPointerAtAddress(Address)) { 703 BinaryData *MethodBD = BC.getBinaryDataAtAddress(MethodAddr.get()); 704 if (!MethodBD) // skip unknown methods 705 continue; 706 MCSymbol *MethodSym = MethodBD->getSymbol(); 707 MethodToVtable[MethodSym] = VtableBase; 708 DEBUG_VERBOSE(1, { 709 const BinaryFunction *Method = BC.getFunctionForSymbol(MethodSym); 710 dbgs() << "BOLT-INFO: ICP found method = " 711 << Twine::utohexstr(MethodAddr.get()) << "/" 712 << (Method ? Method->getPrintName() : "") << "\n"; 713 }); 714 } 715 } 716 717 // Find the vtable for each target symbol. 718 for (size_t I = 0; I < SymTargets.size(); ++I) { 719 auto Itr = MethodToVtable.find(SymTargets[I].first); 720 if (Itr != MethodToVtable.end()) { 721 if (BinaryData *BD = BC.getBinaryDataContainingAddress(Itr->second)) { 722 const uint64_t Addend = Itr->second - BD->getAddress(); 723 VtableSyms.emplace_back(BD->getSymbol(), Addend); 724 continue; 725 } 726 } 727 // Give up if we can't find the vtable for a method. 728 DEBUG_VERBOSE(1, dbgs() << "BOLT-INFO: ICP can't find vtable for " 729 << SymTargets[I].first->getName() << "\n"); 730 return MethodInfoType(); 731 } 732 733 // Make sure the vtable reg is not clobbered by the argument passing code 734 if (VtableReg != MethodReg) { 735 for (MCInst *CurInst = MethodFetchInsns.front(); CurInst < &Inst; 736 ++CurInst) { 737 const MCInstrDesc &InstrInfo = BC.MII->get(CurInst->getOpcode()); 738 if (InstrInfo.hasDefOfPhysReg(*CurInst, VtableReg, *BC.MRI)) 739 return MethodInfoType(); 740 } 741 } 742 743 return MethodInfoType(VtableSyms, MethodFetchInsns); 744 } 745 746 std::vector<std::unique_ptr<BinaryBasicBlock>> 747 IndirectCallPromotion::rewriteCall( 748 BinaryBasicBlock &IndCallBlock, const MCInst &CallInst, 749 MCPlusBuilder::BlocksVectorTy &&ICPcode, 750 const std::vector<MCInst *> &MethodFetchInsns) const { 751 BinaryFunction &Function = *IndCallBlock.getFunction(); 752 MCPlusBuilder *MIB = Function.getBinaryContext().MIB.get(); 753 754 // Create new basic blocks with correct code in each one first. 755 std::vector<std::unique_ptr<BinaryBasicBlock>> NewBBs; 756 const bool IsTailCallOrJT = 757 (MIB->isTailCall(CallInst) || Function.getJumpTable(CallInst)); 758 759 // If we are tracking the indirect call/jump address, propagate the address to 760 // the ICP code. 761 const std::optional<uint32_t> IndirectInstrOffset = MIB->getOffset(CallInst); 762 if (IndirectInstrOffset) { 763 for (auto &[Symbol, Instructions] : ICPcode) 764 for (MCInst &Inst : Instructions) 765 MIB->setOffset(Inst, *IndirectInstrOffset); 766 } 767 768 // Move instructions from the tail of the original call block 769 // to the merge block. 770 771 // Remember any pseudo instructions following a tail call. These 772 // must be preserved and moved to the original block. 773 InstructionListType TailInsts; 774 const MCInst *TailInst = &CallInst; 775 if (IsTailCallOrJT) 776 while (TailInst + 1 < &(*IndCallBlock.end()) && 777 MIB->isPseudo(*(TailInst + 1))) 778 TailInsts.push_back(*++TailInst); 779 780 InstructionListType MovedInst = IndCallBlock.splitInstructions(&CallInst); 781 // Link new BBs to the original input offset of the indirect call site or its 782 // containing BB, so we can map samples recorded in new BBs back to the 783 // original BB seen in the input binary (if using BAT). 784 const uint32_t OrigOffset = IndirectInstrOffset 785 ? *IndirectInstrOffset 786 : IndCallBlock.getInputOffset(); 787 788 IndCallBlock.eraseInstructions(MethodFetchInsns.begin(), 789 MethodFetchInsns.end()); 790 if (IndCallBlock.empty() || 791 (!MethodFetchInsns.empty() && MethodFetchInsns.back() == &CallInst)) 792 IndCallBlock.addInstructions(ICPcode.front().second.begin(), 793 ICPcode.front().second.end()); 794 else 795 IndCallBlock.replaceInstruction(std::prev(IndCallBlock.end()), 796 ICPcode.front().second); 797 IndCallBlock.addInstructions(TailInsts.begin(), TailInsts.end()); 798 799 for (auto Itr = ICPcode.begin() + 1; Itr != ICPcode.end(); ++Itr) { 800 MCSymbol *&Sym = Itr->first; 801 InstructionListType &Insts = Itr->second; 802 assert(Sym); 803 std::unique_ptr<BinaryBasicBlock> TBB = Function.createBasicBlock(Sym); 804 TBB->setOffset(OrigOffset); 805 for (MCInst &Inst : Insts) // sanitize new instructions. 806 if (MIB->isCall(Inst)) 807 MIB->removeAnnotation(Inst, "CallProfile"); 808 TBB->addInstructions(Insts.begin(), Insts.end()); 809 NewBBs.emplace_back(std::move(TBB)); 810 } 811 812 // Move tail of instructions from after the original call to 813 // the merge block. 814 if (!IsTailCallOrJT) 815 NewBBs.back()->addInstructions(MovedInst.begin(), MovedInst.end()); 816 817 return NewBBs; 818 } 819 820 BinaryBasicBlock * 821 IndirectCallPromotion::fixCFG(BinaryBasicBlock &IndCallBlock, 822 const bool IsTailCall, const bool IsJumpTable, 823 IndirectCallPromotion::BasicBlocksVector &&NewBBs, 824 const std::vector<Callsite> &Targets) const { 825 BinaryFunction &Function = *IndCallBlock.getFunction(); 826 using BinaryBranchInfo = BinaryBasicBlock::BinaryBranchInfo; 827 BinaryBasicBlock *MergeBlock = nullptr; 828 829 // Scale indirect call counts to the execution count of the original 830 // basic block containing the indirect call. 831 uint64_t TotalCount = IndCallBlock.getKnownExecutionCount(); 832 uint64_t TotalIndirectBranches = 0; 833 for (const Callsite &Target : Targets) 834 TotalIndirectBranches += Target.Branches; 835 if (TotalIndirectBranches == 0) 836 TotalIndirectBranches = 1; 837 BinaryBasicBlock::BranchInfoType BBI; 838 BinaryBasicBlock::BranchInfoType ScaledBBI; 839 for (const Callsite &Target : Targets) { 840 const size_t NumEntries = 841 std::max(static_cast<std::size_t>(1UL), Target.JTIndices.size()); 842 for (size_t I = 0; I < NumEntries; ++I) { 843 BBI.push_back( 844 BinaryBranchInfo{(Target.Branches + NumEntries - 1) / NumEntries, 845 (Target.Mispreds + NumEntries - 1) / NumEntries}); 846 ScaledBBI.push_back( 847 BinaryBranchInfo{uint64_t(TotalCount * Target.Branches / 848 (NumEntries * TotalIndirectBranches)), 849 uint64_t(TotalCount * Target.Mispreds / 850 (NumEntries * TotalIndirectBranches))}); 851 } 852 } 853 854 if (IsJumpTable) { 855 BinaryBasicBlock *NewIndCallBlock = NewBBs.back().get(); 856 IndCallBlock.moveAllSuccessorsTo(NewIndCallBlock); 857 858 std::vector<MCSymbol *> SymTargets; 859 for (const Callsite &Target : Targets) { 860 const size_t NumEntries = 861 std::max(static_cast<std::size_t>(1UL), Target.JTIndices.size()); 862 for (size_t I = 0; I < NumEntries; ++I) 863 SymTargets.push_back(Target.To.Sym); 864 } 865 assert(SymTargets.size() > NewBBs.size() - 1 && 866 "There must be a target symbol associated with each new BB."); 867 868 for (uint64_t I = 0; I < NewBBs.size(); ++I) { 869 BinaryBasicBlock *SourceBB = I ? NewBBs[I - 1].get() : &IndCallBlock; 870 SourceBB->setExecutionCount(TotalCount); 871 872 BinaryBasicBlock *TargetBB = 873 Function.getBasicBlockForLabel(SymTargets[I]); 874 SourceBB->addSuccessor(TargetBB, ScaledBBI[I]); // taken 875 876 TotalCount -= ScaledBBI[I].Count; 877 SourceBB->addSuccessor(NewBBs[I].get(), TotalCount); // fall-through 878 879 // Update branch info for the indirect jump. 880 BinaryBasicBlock::BinaryBranchInfo &BranchInfo = 881 NewIndCallBlock->getBranchInfo(*TargetBB); 882 if (BranchInfo.Count > BBI[I].Count) 883 BranchInfo.Count -= BBI[I].Count; 884 else 885 BranchInfo.Count = 0; 886 887 if (BranchInfo.MispredictedCount > BBI[I].MispredictedCount) 888 BranchInfo.MispredictedCount -= BBI[I].MispredictedCount; 889 else 890 BranchInfo.MispredictedCount = 0; 891 } 892 } else { 893 assert(NewBBs.size() >= 2); 894 assert(NewBBs.size() % 2 == 1 || IndCallBlock.succ_empty()); 895 assert(NewBBs.size() % 2 == 1 || IsTailCall); 896 897 auto ScaledBI = ScaledBBI.begin(); 898 auto updateCurrentBranchInfo = [&] { 899 assert(ScaledBI != ScaledBBI.end()); 900 TotalCount -= ScaledBI->Count; 901 ++ScaledBI; 902 }; 903 904 if (!IsTailCall) { 905 MergeBlock = NewBBs.back().get(); 906 IndCallBlock.moveAllSuccessorsTo(MergeBlock); 907 } 908 909 // Fix up successors and execution counts. 910 updateCurrentBranchInfo(); 911 IndCallBlock.addSuccessor(NewBBs[1].get(), TotalCount); 912 IndCallBlock.addSuccessor(NewBBs[0].get(), ScaledBBI[0]); 913 914 const size_t Adj = IsTailCall ? 1 : 2; 915 for (size_t I = 0; I < NewBBs.size() - Adj; ++I) { 916 assert(TotalCount <= IndCallBlock.getExecutionCount() || 917 TotalCount <= uint64_t(TotalIndirectBranches)); 918 uint64_t ExecCount = ScaledBBI[(I + 1) / 2].Count; 919 if (I % 2 == 0) { 920 if (MergeBlock) 921 NewBBs[I]->addSuccessor(MergeBlock, ScaledBBI[(I + 1) / 2].Count); 922 } else { 923 assert(I + 2 < NewBBs.size()); 924 updateCurrentBranchInfo(); 925 NewBBs[I]->addSuccessor(NewBBs[I + 2].get(), TotalCount); 926 NewBBs[I]->addSuccessor(NewBBs[I + 1].get(), ScaledBBI[(I + 1) / 2]); 927 ExecCount += TotalCount; 928 } 929 NewBBs[I]->setExecutionCount(ExecCount); 930 } 931 932 if (MergeBlock) { 933 // Arrange for the MergeBlock to be the fallthrough for the first 934 // promoted call block. 935 std::unique_ptr<BinaryBasicBlock> MBPtr; 936 std::swap(MBPtr, NewBBs.back()); 937 NewBBs.pop_back(); 938 NewBBs.emplace(NewBBs.begin() + 1, std::move(MBPtr)); 939 // TODO: is COUNT_FALLTHROUGH_EDGE the right thing here? 940 NewBBs.back()->addSuccessor(MergeBlock, TotalCount); // uncond branch 941 } 942 } 943 944 // Update the execution count. 945 NewBBs.back()->setExecutionCount(TotalCount); 946 947 // Update BB and BB layout. 948 Function.insertBasicBlocks(&IndCallBlock, std::move(NewBBs)); 949 assert(Function.validateCFG()); 950 951 return MergeBlock; 952 } 953 954 size_t IndirectCallPromotion::canPromoteCallsite( 955 const BinaryBasicBlock &BB, const MCInst &Inst, 956 const std::vector<Callsite> &Targets, uint64_t NumCalls) { 957 BinaryFunction *BF = BB.getFunction(); 958 const BinaryContext &BC = BF->getBinaryContext(); 959 960 if (BB.getKnownExecutionCount() < opts::ExecutionCountThreshold) 961 return 0; 962 963 const bool IsJumpTable = BF->getJumpTable(Inst); 964 965 auto computeStats = [&](size_t N) { 966 for (size_t I = 0; I < N; ++I) 967 if (IsJumpTable) 968 TotalNumFrequentJmps += Targets[I].Branches; 969 else 970 TotalNumFrequentCalls += Targets[I].Branches; 971 }; 972 973 // If we have no targets (or no calls), skip this callsite. 974 if (Targets.empty() || !NumCalls) { 975 if (opts::Verbosity >= 1) { 976 const ptrdiff_t InstIdx = &Inst - &(*BB.begin()); 977 outs() << "BOLT-INFO: ICP failed in " << *BF << " @ " << InstIdx << " in " 978 << BB.getName() << ", calls = " << NumCalls 979 << ", targets empty or NumCalls == 0.\n"; 980 } 981 return 0; 982 } 983 984 size_t TopN = opts::ICPTopN; 985 if (IsJumpTable) 986 TopN = opts::ICPJumpTablesTopN ? opts::ICPJumpTablesTopN : TopN; 987 else 988 TopN = opts::ICPCallsTopN ? opts::ICPCallsTopN : TopN; 989 990 const size_t TrialN = TopN ? std::min(TopN, Targets.size()) : Targets.size(); 991 992 if (opts::ICPTopCallsites && !BC.MIB->hasAnnotation(Inst, "DoICP")) 993 return 0; 994 995 // Pick the top N targets. 996 uint64_t TotalMispredictsTopN = 0; 997 size_t N = 0; 998 999 if (opts::ICPUseMispredicts && 1000 (!IsJumpTable || opts::ICPJumpTablesByTarget)) { 1001 // Count total number of mispredictions for (at most) the top N targets. 1002 // We may choose a smaller N (TrialN vs. N) if the frequency threshold 1003 // is exceeded by fewer targets. 1004 double Threshold = double(opts::ICPMispredictThreshold); 1005 for (size_t I = 0; I < TrialN && Threshold > 0; ++I, ++N) { 1006 Threshold -= (100.0 * Targets[I].Mispreds) / NumCalls; 1007 TotalMispredictsTopN += Targets[I].Mispreds; 1008 } 1009 computeStats(N); 1010 1011 // Compute the misprediction frequency of the top N call targets. If this 1012 // frequency is greater than the threshold, we should try ICP on this 1013 // callsite. 1014 const double TopNFrequency = (100.0 * TotalMispredictsTopN) / NumCalls; 1015 if (TopNFrequency == 0 || TopNFrequency < opts::ICPMispredictThreshold) { 1016 if (opts::Verbosity >= 1) { 1017 const ptrdiff_t InstIdx = &Inst - &(*BB.begin()); 1018 outs() << "BOLT-INFO: ICP failed in " << *BF << " @ " << InstIdx 1019 << " in " << BB.getName() << ", calls = " << NumCalls 1020 << ", top N mis. frequency " << format("%.1f", TopNFrequency) 1021 << "% < " << opts::ICPMispredictThreshold << "%\n"; 1022 } 1023 return 0; 1024 } 1025 } else { 1026 size_t MaxTargets = 0; 1027 1028 // Count total number of calls for (at most) the top N targets. 1029 // We may choose a smaller N (TrialN vs. N) if the frequency threshold 1030 // is exceeded by fewer targets. 1031 const unsigned TotalThreshold = IsJumpTable 1032 ? opts::ICPJTTotalPercentThreshold 1033 : opts::ICPCallsTotalPercentThreshold; 1034 const unsigned RemainingThreshold = 1035 IsJumpTable ? opts::ICPJTRemainingPercentThreshold 1036 : opts::ICPCallsRemainingPercentThreshold; 1037 uint64_t NumRemainingCalls = NumCalls; 1038 for (size_t I = 0; I < TrialN; ++I, ++MaxTargets) { 1039 if (100 * Targets[I].Branches < NumCalls * TotalThreshold) 1040 break; 1041 if (100 * Targets[I].Branches < NumRemainingCalls * RemainingThreshold) 1042 break; 1043 if (N + (Targets[I].JTIndices.empty() ? 1 : Targets[I].JTIndices.size()) > 1044 TrialN) 1045 break; 1046 TotalMispredictsTopN += Targets[I].Mispreds; 1047 NumRemainingCalls -= Targets[I].Branches; 1048 N += Targets[I].JTIndices.empty() ? 1 : Targets[I].JTIndices.size(); 1049 } 1050 computeStats(MaxTargets); 1051 1052 // Don't check misprediction frequency for jump tables -- we don't really 1053 // care as long as we are saving loads from the jump table. 1054 if (!IsJumpTable || opts::ICPJumpTablesByTarget) { 1055 // Compute the misprediction frequency of the top N call targets. If 1056 // this frequency is less than the threshold, we should skip ICP at 1057 // this callsite. 1058 const double TopNMispredictFrequency = 1059 (100.0 * TotalMispredictsTopN) / NumCalls; 1060 1061 if (TopNMispredictFrequency < opts::ICPMispredictThreshold) { 1062 if (opts::Verbosity >= 1) { 1063 const ptrdiff_t InstIdx = &Inst - &(*BB.begin()); 1064 outs() << "BOLT-INFO: ICP failed in " << *BF << " @ " << InstIdx 1065 << " in " << BB.getName() << ", calls = " << NumCalls 1066 << ", top N mispredict frequency " 1067 << format("%.1f", TopNMispredictFrequency) << "% < " 1068 << opts::ICPMispredictThreshold << "%\n"; 1069 } 1070 return 0; 1071 } 1072 } 1073 } 1074 1075 // Filter by inline-ability of target functions, stop at first target that 1076 // can't be inlined. 1077 if (!IsJumpTable && opts::ICPPeelForInline) { 1078 for (size_t I = 0; I < N; ++I) { 1079 const MCSymbol *TargetSym = Targets[I].To.Sym; 1080 const BinaryFunction *TargetBF = BC.getFunctionForSymbol(TargetSym); 1081 if (!TargetBF || !BinaryFunctionPass::shouldOptimize(*TargetBF) || 1082 getInliningInfo(*TargetBF).Type == InliningType::INL_NONE) { 1083 N = I; 1084 break; 1085 } 1086 } 1087 } 1088 1089 // Filter functions that can have ICP applied (for debugging) 1090 if (!opts::ICPFuncsList.empty()) { 1091 for (std::string &Name : opts::ICPFuncsList) 1092 if (BF->hasName(Name)) 1093 return N; 1094 return 0; 1095 } 1096 1097 return N; 1098 } 1099 1100 void IndirectCallPromotion::printCallsiteInfo( 1101 const BinaryBasicBlock &BB, const MCInst &Inst, 1102 const std::vector<Callsite> &Targets, const size_t N, 1103 uint64_t NumCalls) const { 1104 BinaryContext &BC = BB.getFunction()->getBinaryContext(); 1105 const bool IsTailCall = BC.MIB->isTailCall(Inst); 1106 const bool IsJumpTable = BB.getFunction()->getJumpTable(Inst); 1107 const ptrdiff_t InstIdx = &Inst - &(*BB.begin()); 1108 1109 outs() << "BOLT-INFO: ICP candidate branch info: " << *BB.getFunction() 1110 << " @ " << InstIdx << " in " << BB.getName() 1111 << " -> calls = " << NumCalls 1112 << (IsTailCall ? " (tail)" : (IsJumpTable ? " (jump table)" : "")) 1113 << "\n"; 1114 for (size_t I = 0; I < N; I++) { 1115 const double Frequency = 100.0 * Targets[I].Branches / NumCalls; 1116 const double MisFrequency = 100.0 * Targets[I].Mispreds / NumCalls; 1117 outs() << "BOLT-INFO: "; 1118 if (Targets[I].To.Sym) 1119 outs() << Targets[I].To.Sym->getName(); 1120 else 1121 outs() << Targets[I].To.Addr; 1122 outs() << ", calls = " << Targets[I].Branches 1123 << ", mispreds = " << Targets[I].Mispreds 1124 << ", taken freq = " << format("%.1f", Frequency) << "%" 1125 << ", mis. freq = " << format("%.1f", MisFrequency) << "%"; 1126 bool First = true; 1127 for (uint64_t JTIndex : Targets[I].JTIndices) { 1128 outs() << (First ? ", indices = " : ", ") << JTIndex; 1129 First = false; 1130 } 1131 outs() << "\n"; 1132 } 1133 1134 LLVM_DEBUG({ 1135 dbgs() << "BOLT-INFO: ICP original call instruction:"; 1136 BC.printInstruction(dbgs(), Inst, Targets[0].From.Addr, nullptr, true); 1137 }); 1138 } 1139 1140 Error IndirectCallPromotion::runOnFunctions(BinaryContext &BC) { 1141 if (opts::ICP == ICP_NONE) 1142 return Error::success(); 1143 1144 auto &BFs = BC.getBinaryFunctions(); 1145 1146 const bool OptimizeCalls = (opts::ICP == ICP_CALLS || opts::ICP == ICP_ALL); 1147 const bool OptimizeJumpTables = 1148 (opts::ICP == ICP_JUMP_TABLES || opts::ICP == ICP_ALL); 1149 1150 std::unique_ptr<RegAnalysis> RA; 1151 std::unique_ptr<BinaryFunctionCallGraph> CG; 1152 if (OptimizeJumpTables) { 1153 CG.reset(new BinaryFunctionCallGraph(buildCallGraph(BC))); 1154 RA.reset(new RegAnalysis(BC, &BFs, &*CG)); 1155 } 1156 1157 // If icp-top-callsites is enabled, compute the total number of indirect 1158 // calls and then optimize the hottest callsites that contribute to that 1159 // total. 1160 SetVector<BinaryFunction *> Functions; 1161 if (opts::ICPTopCallsites == 0) { 1162 for (auto &KV : BFs) 1163 Functions.insert(&KV.second); 1164 } else { 1165 using IndirectCallsite = std::tuple<uint64_t, MCInst *, BinaryFunction *>; 1166 std::vector<IndirectCallsite> IndirectCalls; 1167 size_t TotalIndirectCalls = 0; 1168 1169 // Find all the indirect callsites. 1170 for (auto &BFIt : BFs) { 1171 BinaryFunction &Function = BFIt.second; 1172 1173 if (!shouldOptimize(Function)) 1174 continue; 1175 1176 const bool HasLayout = !Function.getLayout().block_empty(); 1177 1178 for (BinaryBasicBlock &BB : Function) { 1179 if (HasLayout && Function.isSplit() && BB.isCold()) 1180 continue; 1181 1182 for (MCInst &Inst : BB) { 1183 const bool IsJumpTable = Function.getJumpTable(Inst); 1184 const bool HasIndirectCallProfile = 1185 BC.MIB->hasAnnotation(Inst, "CallProfile"); 1186 const bool IsDirectCall = 1187 (BC.MIB->isCall(Inst) && BC.MIB->getTargetSymbol(Inst, 0)); 1188 1189 if (!IsDirectCall && 1190 ((HasIndirectCallProfile && !IsJumpTable && OptimizeCalls) || 1191 (IsJumpTable && OptimizeJumpTables))) { 1192 uint64_t NumCalls = 0; 1193 for (const Callsite &BInfo : getCallTargets(BB, Inst)) 1194 NumCalls += BInfo.Branches; 1195 IndirectCalls.push_back( 1196 std::make_tuple(NumCalls, &Inst, &Function)); 1197 TotalIndirectCalls += NumCalls; 1198 } 1199 } 1200 } 1201 } 1202 1203 // Sort callsites by execution count. 1204 llvm::sort(reverse(IndirectCalls)); 1205 1206 // Find callsites that contribute to the top "opts::ICPTopCallsites"% 1207 // number of calls. 1208 const float TopPerc = opts::ICPTopCallsites / 100.0f; 1209 int64_t MaxCalls = TotalIndirectCalls * TopPerc; 1210 uint64_t LastFreq = std::numeric_limits<uint64_t>::max(); 1211 size_t Num = 0; 1212 for (const IndirectCallsite &IC : IndirectCalls) { 1213 const uint64_t CurFreq = std::get<0>(IC); 1214 // Once we decide to stop, include at least all branches that share the 1215 // same frequency of the last one to avoid non-deterministic behavior 1216 // (e.g. turning on/off ICP depending on the order of functions) 1217 if (MaxCalls <= 0 && CurFreq != LastFreq) 1218 break; 1219 MaxCalls -= CurFreq; 1220 LastFreq = CurFreq; 1221 BC.MIB->addAnnotation(*std::get<1>(IC), "DoICP", true); 1222 Functions.insert(std::get<2>(IC)); 1223 ++Num; 1224 } 1225 outs() << "BOLT-INFO: ICP Total indirect calls = " << TotalIndirectCalls 1226 << ", " << Num << " callsites cover " << opts::ICPTopCallsites 1227 << "% of all indirect calls\n"; 1228 } 1229 1230 for (BinaryFunction *FuncPtr : Functions) { 1231 BinaryFunction &Function = *FuncPtr; 1232 1233 if (!shouldOptimize(Function)) 1234 continue; 1235 1236 const bool HasLayout = !Function.getLayout().block_empty(); 1237 1238 // Total number of indirect calls issued from the current Function. 1239 // (a fraction of TotalIndirectCalls) 1240 uint64_t FuncTotalIndirectCalls = 0; 1241 uint64_t FuncTotalIndirectJmps = 0; 1242 1243 std::vector<BinaryBasicBlock *> BBs; 1244 for (BinaryBasicBlock &BB : Function) { 1245 // Skip indirect calls in cold blocks. 1246 if (!HasLayout || !Function.isSplit() || !BB.isCold()) 1247 BBs.push_back(&BB); 1248 } 1249 if (BBs.empty()) 1250 continue; 1251 1252 DataflowInfoManager Info(Function, RA.get(), nullptr); 1253 while (!BBs.empty()) { 1254 BinaryBasicBlock *BB = BBs.back(); 1255 BBs.pop_back(); 1256 1257 for (unsigned Idx = 0; Idx < BB->size(); ++Idx) { 1258 MCInst &Inst = BB->getInstructionAtIndex(Idx); 1259 const ptrdiff_t InstIdx = &Inst - &(*BB->begin()); 1260 const bool IsTailCall = BC.MIB->isTailCall(Inst); 1261 const bool HasIndirectCallProfile = 1262 BC.MIB->hasAnnotation(Inst, "CallProfile"); 1263 const bool IsJumpTable = Function.getJumpTable(Inst); 1264 1265 if (BC.MIB->isCall(Inst)) 1266 TotalCalls += BB->getKnownExecutionCount(); 1267 1268 if (IsJumpTable && !OptimizeJumpTables) 1269 continue; 1270 1271 if (!IsJumpTable && (!HasIndirectCallProfile || !OptimizeCalls)) 1272 continue; 1273 1274 // Ignore direct calls. 1275 if (BC.MIB->isCall(Inst) && BC.MIB->getTargetSymbol(Inst, 0)) 1276 continue; 1277 1278 assert((BC.MIB->isCall(Inst) || BC.MIB->isIndirectBranch(Inst)) && 1279 "expected a call or an indirect jump instruction"); 1280 1281 if (IsJumpTable) 1282 ++TotalJumpTableCallsites; 1283 else 1284 ++TotalIndirectCallsites; 1285 1286 std::vector<Callsite> Targets = getCallTargets(*BB, Inst); 1287 1288 // Compute the total number of calls from this particular callsite. 1289 uint64_t NumCalls = 0; 1290 for (const Callsite &BInfo : Targets) 1291 NumCalls += BInfo.Branches; 1292 if (!IsJumpTable) 1293 FuncTotalIndirectCalls += NumCalls; 1294 else 1295 FuncTotalIndirectJmps += NumCalls; 1296 1297 // If FLAGS regs is alive after this jmp site, do not try 1298 // promoting because we will clobber FLAGS. 1299 if (IsJumpTable) { 1300 ErrorOr<const BitVector &> State = 1301 Info.getLivenessAnalysis().getStateBefore(Inst); 1302 if (!State || (State && (*State)[BC.MIB->getFlagsReg()])) { 1303 if (opts::Verbosity >= 1) 1304 outs() << "BOLT-INFO: ICP failed in " << Function << " @ " 1305 << InstIdx << " in " << BB->getName() 1306 << ", calls = " << NumCalls 1307 << (State ? ", cannot clobber flags reg.\n" 1308 : ", no liveness data available.\n"); 1309 continue; 1310 } 1311 } 1312 1313 // Should this callsite be optimized? Return the number of targets 1314 // to use when promoting this call. A value of zero means to skip 1315 // this callsite. 1316 size_t N = canPromoteCallsite(*BB, Inst, Targets, NumCalls); 1317 1318 // If it is a jump table and it failed to meet our initial threshold, 1319 // proceed to findCallTargetSymbols -- it may reevaluate N if 1320 // memory profile is present 1321 if (!N && !IsJumpTable) 1322 continue; 1323 1324 if (opts::Verbosity >= 1) 1325 printCallsiteInfo(*BB, Inst, Targets, N, NumCalls); 1326 1327 // Find MCSymbols or absolute addresses for each call target. 1328 MCInst *TargetFetchInst = nullptr; 1329 const SymTargetsType SymTargets = 1330 findCallTargetSymbols(Targets, N, *BB, Inst, TargetFetchInst); 1331 1332 // findCallTargetSymbols may have changed N if mem profile is available 1333 // for jump tables 1334 if (!N) 1335 continue; 1336 1337 LLVM_DEBUG(printDecision(dbgs(), Targets, N)); 1338 1339 // If we can't resolve any of the target symbols, punt on this callsite. 1340 // TODO: can this ever happen? 1341 if (SymTargets.size() < N) { 1342 const size_t LastTarget = SymTargets.size(); 1343 if (opts::Verbosity >= 1) 1344 outs() << "BOLT-INFO: ICP failed in " << Function << " @ " 1345 << InstIdx << " in " << BB->getName() 1346 << ", calls = " << NumCalls 1347 << ", ICP failed to find target symbol for " 1348 << Targets[LastTarget].To.Sym->getName() << "\n"; 1349 continue; 1350 } 1351 1352 MethodInfoType MethodInfo; 1353 1354 if (!IsJumpTable) { 1355 MethodInfo = maybeGetVtableSyms(*BB, Inst, SymTargets); 1356 TotalMethodLoadsEliminated += MethodInfo.first.empty() ? 0 : 1; 1357 LLVM_DEBUG(dbgs() 1358 << "BOLT-INFO: ICP " 1359 << (!MethodInfo.first.empty() ? "found" : "did not find") 1360 << " vtables for all methods.\n"); 1361 } else if (TargetFetchInst) { 1362 ++TotalIndexBasedJumps; 1363 MethodInfo.second.push_back(TargetFetchInst); 1364 } 1365 1366 // Generate new promoted call code for this callsite. 1367 MCPlusBuilder::BlocksVectorTy ICPcode = 1368 (IsJumpTable && !opts::ICPJumpTablesByTarget) 1369 ? BC.MIB->jumpTablePromotion(Inst, SymTargets, 1370 MethodInfo.second, BC.Ctx.get()) 1371 : BC.MIB->indirectCallPromotion( 1372 Inst, SymTargets, MethodInfo.first, MethodInfo.second, 1373 opts::ICPOldCodeSequence, BC.Ctx.get()); 1374 1375 if (ICPcode.empty()) { 1376 if (opts::Verbosity >= 1) 1377 outs() << "BOLT-INFO: ICP failed in " << Function << " @ " 1378 << InstIdx << " in " << BB->getName() 1379 << ", calls = " << NumCalls 1380 << ", unable to generate promoted call code.\n"; 1381 continue; 1382 } 1383 1384 LLVM_DEBUG({ 1385 uint64_t Offset = Targets[0].From.Addr; 1386 dbgs() << "BOLT-INFO: ICP indirect call code:\n"; 1387 for (const auto &entry : ICPcode) { 1388 const MCSymbol *const &Sym = entry.first; 1389 const InstructionListType &Insts = entry.second; 1390 if (Sym) 1391 dbgs() << Sym->getName() << ":\n"; 1392 Offset = BC.printInstructions(dbgs(), Insts.begin(), Insts.end(), 1393 Offset); 1394 } 1395 dbgs() << "---------------------------------------------------\n"; 1396 }); 1397 1398 // Rewrite the CFG with the newly generated ICP code. 1399 std::vector<std::unique_ptr<BinaryBasicBlock>> NewBBs = 1400 rewriteCall(*BB, Inst, std::move(ICPcode), MethodInfo.second); 1401 1402 // Fix the CFG after inserting the new basic blocks. 1403 BinaryBasicBlock *MergeBlock = 1404 fixCFG(*BB, IsTailCall, IsJumpTable, std::move(NewBBs), Targets); 1405 1406 // Since the tail of the original block was split off and it may contain 1407 // additional indirect calls, we must add the merge block to the set of 1408 // blocks to process. 1409 if (MergeBlock) 1410 BBs.push_back(MergeBlock); 1411 1412 if (opts::Verbosity >= 1) 1413 outs() << "BOLT-INFO: ICP succeeded in " << Function << " @ " 1414 << InstIdx << " in " << BB->getName() 1415 << " -> calls = " << NumCalls << "\n"; 1416 1417 if (IsJumpTable) 1418 ++TotalOptimizedJumpTableCallsites; 1419 else 1420 ++TotalOptimizedIndirectCallsites; 1421 1422 Modified.insert(&Function); 1423 } 1424 } 1425 TotalIndirectCalls += FuncTotalIndirectCalls; 1426 TotalIndirectJmps += FuncTotalIndirectJmps; 1427 } 1428 1429 outs() << "BOLT-INFO: ICP total indirect callsites with profile = " 1430 << TotalIndirectCallsites << "\n" 1431 << "BOLT-INFO: ICP total jump table callsites = " 1432 << TotalJumpTableCallsites << "\n" 1433 << "BOLT-INFO: ICP total number of calls = " << TotalCalls << "\n" 1434 << "BOLT-INFO: ICP percentage of calls that are indirect = " 1435 << format("%.1f", (100.0 * TotalIndirectCalls) / TotalCalls) << "%\n" 1436 << "BOLT-INFO: ICP percentage of indirect calls that can be " 1437 "optimized = " 1438 << format("%.1f", (100.0 * TotalNumFrequentCalls) / 1439 std::max<size_t>(TotalIndirectCalls, 1)) 1440 << "%\n" 1441 << "BOLT-INFO: ICP percentage of indirect callsites that are " 1442 "optimized = " 1443 << format("%.1f", (100.0 * TotalOptimizedIndirectCallsites) / 1444 std::max<uint64_t>(TotalIndirectCallsites, 1)) 1445 << "%\n" 1446 << "BOLT-INFO: ICP number of method load elimination candidates = " 1447 << TotalMethodLoadEliminationCandidates << "\n" 1448 << "BOLT-INFO: ICP percentage of method calls candidates that have " 1449 "loads eliminated = " 1450 << format("%.1f", (100.0 * TotalMethodLoadsEliminated) / 1451 std::max<uint64_t>( 1452 TotalMethodLoadEliminationCandidates, 1)) 1453 << "%\n" 1454 << "BOLT-INFO: ICP percentage of indirect branches that are " 1455 "optimized = " 1456 << format("%.1f", (100.0 * TotalNumFrequentJmps) / 1457 std::max<uint64_t>(TotalIndirectJmps, 1)) 1458 << "%\n" 1459 << "BOLT-INFO: ICP percentage of jump table callsites that are " 1460 << "optimized = " 1461 << format("%.1f", (100.0 * TotalOptimizedJumpTableCallsites) / 1462 std::max<uint64_t>(TotalJumpTableCallsites, 1)) 1463 << "%\n" 1464 << "BOLT-INFO: ICP number of jump table callsites that can use hot " 1465 << "indices = " << TotalIndexBasedCandidates << "\n" 1466 << "BOLT-INFO: ICP percentage of jump table callsites that use hot " 1467 "indices = " 1468 << format("%.1f", (100.0 * TotalIndexBasedJumps) / 1469 std::max<uint64_t>(TotalIndexBasedCandidates, 1)) 1470 << "%\n"; 1471 1472 #ifndef NDEBUG 1473 verifyProfile(BFs); 1474 #endif 1475 return Error::success(); 1476 } 1477 1478 } // namespace bolt 1479 } // namespace llvm 1480