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