1 //===- ModuleSummaryAnalysis.cpp - Module summary index builder -----------===// 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 pass builds a ModuleSummaryIndex object for the module, to be written 10 // to bitcode or LLVM assembly. 11 // 12 //===----------------------------------------------------------------------===// 13 14 #include "llvm/Analysis/ModuleSummaryAnalysis.h" 15 #include "llvm/ADT/ArrayRef.h" 16 #include "llvm/ADT/DenseSet.h" 17 #include "llvm/ADT/MapVector.h" 18 #include "llvm/ADT/STLExtras.h" 19 #include "llvm/ADT/SetVector.h" 20 #include "llvm/ADT/SmallPtrSet.h" 21 #include "llvm/ADT/SmallVector.h" 22 #include "llvm/ADT/StringRef.h" 23 #include "llvm/Analysis/BlockFrequencyInfo.h" 24 #include "llvm/Analysis/BranchProbabilityInfo.h" 25 #include "llvm/Analysis/IndirectCallPromotionAnalysis.h" 26 #include "llvm/Analysis/LoopInfo.h" 27 #include "llvm/Analysis/ProfileSummaryInfo.h" 28 #include "llvm/Analysis/TypeMetadataUtils.h" 29 #include "llvm/IR/Attributes.h" 30 #include "llvm/IR/BasicBlock.h" 31 #include "llvm/IR/CallSite.h" 32 #include "llvm/IR/Constant.h" 33 #include "llvm/IR/Constants.h" 34 #include "llvm/IR/Dominators.h" 35 #include "llvm/IR/Function.h" 36 #include "llvm/IR/GlobalAlias.h" 37 #include "llvm/IR/GlobalValue.h" 38 #include "llvm/IR/GlobalVariable.h" 39 #include "llvm/IR/Instructions.h" 40 #include "llvm/IR/IntrinsicInst.h" 41 #include "llvm/IR/Intrinsics.h" 42 #include "llvm/IR/Metadata.h" 43 #include "llvm/IR/Module.h" 44 #include "llvm/IR/ModuleSummaryIndex.h" 45 #include "llvm/IR/Use.h" 46 #include "llvm/IR/User.h" 47 #include "llvm/Object/ModuleSymbolTable.h" 48 #include "llvm/Object/SymbolicFile.h" 49 #include "llvm/Pass.h" 50 #include "llvm/Support/Casting.h" 51 #include "llvm/Support/CommandLine.h" 52 #include <algorithm> 53 #include <cassert> 54 #include <cstdint> 55 #include <vector> 56 57 using namespace llvm; 58 59 #define DEBUG_TYPE "module-summary-analysis" 60 61 // Option to force edges cold which will block importing when the 62 // -import-cold-multiplier is set to 0. Useful for debugging. 63 FunctionSummary::ForceSummaryHotnessType ForceSummaryEdgesCold = 64 FunctionSummary::FSHT_None; 65 cl::opt<FunctionSummary::ForceSummaryHotnessType, true> FSEC( 66 "force-summary-edges-cold", cl::Hidden, cl::location(ForceSummaryEdgesCold), 67 cl::desc("Force all edges in the function summary to cold"), 68 cl::values(clEnumValN(FunctionSummary::FSHT_None, "none", "None."), 69 clEnumValN(FunctionSummary::FSHT_AllNonCritical, 70 "all-non-critical", "All non-critical edges."), 71 clEnumValN(FunctionSummary::FSHT_All, "all", "All edges."))); 72 73 cl::opt<std::string> ModuleSummaryDotFile( 74 "module-summary-dot-file", cl::init(""), cl::Hidden, 75 cl::value_desc("filename"), 76 cl::desc("File to emit dot graph of new summary into.")); 77 78 // Walk through the operands of a given User via worklist iteration and populate 79 // the set of GlobalValue references encountered. Invoked either on an 80 // Instruction or a GlobalVariable (which walks its initializer). 81 // Return true if any of the operands contains blockaddress. This is important 82 // to know when computing summary for global var, because if global variable 83 // references basic block address we can't import it separately from function 84 // containing that basic block. For simplicity we currently don't import such 85 // global vars at all. When importing function we aren't interested if any 86 // instruction in it takes an address of any basic block, because instruction 87 // can only take an address of basic block located in the same function. 88 static bool findRefEdges(ModuleSummaryIndex &Index, const User *CurUser, 89 SetVector<ValueInfo> &RefEdges, 90 SmallPtrSet<const User *, 8> &Visited) { 91 bool HasBlockAddress = false; 92 SmallVector<const User *, 32> Worklist; 93 Worklist.push_back(CurUser); 94 95 while (!Worklist.empty()) { 96 const User *U = Worklist.pop_back_val(); 97 98 if (!Visited.insert(U).second) 99 continue; 100 101 ImmutableCallSite CS(U); 102 103 for (const auto &OI : U->operands()) { 104 const User *Operand = dyn_cast<User>(OI); 105 if (!Operand) 106 continue; 107 if (isa<BlockAddress>(Operand)) { 108 HasBlockAddress = true; 109 continue; 110 } 111 if (auto *GV = dyn_cast<GlobalValue>(Operand)) { 112 // We have a reference to a global value. This should be added to 113 // the reference set unless it is a callee. Callees are handled 114 // specially by WriteFunction and are added to a separate list. 115 if (!(CS && CS.isCallee(&OI))) 116 RefEdges.insert(Index.getOrInsertValueInfo(GV)); 117 continue; 118 } 119 Worklist.push_back(Operand); 120 } 121 } 122 return HasBlockAddress; 123 } 124 125 static CalleeInfo::HotnessType getHotness(uint64_t ProfileCount, 126 ProfileSummaryInfo *PSI) { 127 if (!PSI) 128 return CalleeInfo::HotnessType::Unknown; 129 if (PSI->isHotCount(ProfileCount)) 130 return CalleeInfo::HotnessType::Hot; 131 if (PSI->isColdCount(ProfileCount)) 132 return CalleeInfo::HotnessType::Cold; 133 return CalleeInfo::HotnessType::None; 134 } 135 136 static bool isNonRenamableLocal(const GlobalValue &GV) { 137 return GV.hasSection() && GV.hasLocalLinkage(); 138 } 139 140 /// Determine whether this call has all constant integer arguments (excluding 141 /// "this") and summarize it to VCalls or ConstVCalls as appropriate. 142 static void addVCallToSet(DevirtCallSite Call, GlobalValue::GUID Guid, 143 SetVector<FunctionSummary::VFuncId> &VCalls, 144 SetVector<FunctionSummary::ConstVCall> &ConstVCalls) { 145 std::vector<uint64_t> Args; 146 // Start from the second argument to skip the "this" pointer. 147 for (auto &Arg : make_range(Call.CS.arg_begin() + 1, Call.CS.arg_end())) { 148 auto *CI = dyn_cast<ConstantInt>(Arg); 149 if (!CI || CI->getBitWidth() > 64) { 150 VCalls.insert({Guid, Call.Offset}); 151 return; 152 } 153 Args.push_back(CI->getZExtValue()); 154 } 155 ConstVCalls.insert({{Guid, Call.Offset}, std::move(Args)}); 156 } 157 158 /// If this intrinsic call requires that we add information to the function 159 /// summary, do so via the non-constant reference arguments. 160 static void addIntrinsicToSummary( 161 const CallInst *CI, SetVector<GlobalValue::GUID> &TypeTests, 162 SetVector<FunctionSummary::VFuncId> &TypeTestAssumeVCalls, 163 SetVector<FunctionSummary::VFuncId> &TypeCheckedLoadVCalls, 164 SetVector<FunctionSummary::ConstVCall> &TypeTestAssumeConstVCalls, 165 SetVector<FunctionSummary::ConstVCall> &TypeCheckedLoadConstVCalls, 166 DominatorTree &DT) { 167 switch (CI->getCalledFunction()->getIntrinsicID()) { 168 case Intrinsic::type_test: { 169 auto *TypeMDVal = cast<MetadataAsValue>(CI->getArgOperand(1)); 170 auto *TypeId = dyn_cast<MDString>(TypeMDVal->getMetadata()); 171 if (!TypeId) 172 break; 173 GlobalValue::GUID Guid = GlobalValue::getGUID(TypeId->getString()); 174 175 // Produce a summary from type.test intrinsics. We only summarize type.test 176 // intrinsics that are used other than by an llvm.assume intrinsic. 177 // Intrinsics that are assumed are relevant only to the devirtualization 178 // pass, not the type test lowering pass. 179 bool HasNonAssumeUses = llvm::any_of(CI->uses(), [](const Use &CIU) { 180 auto *AssumeCI = dyn_cast<CallInst>(CIU.getUser()); 181 if (!AssumeCI) 182 return true; 183 Function *F = AssumeCI->getCalledFunction(); 184 return !F || F->getIntrinsicID() != Intrinsic::assume; 185 }); 186 if (HasNonAssumeUses) 187 TypeTests.insert(Guid); 188 189 SmallVector<DevirtCallSite, 4> DevirtCalls; 190 SmallVector<CallInst *, 4> Assumes; 191 findDevirtualizableCallsForTypeTest(DevirtCalls, Assumes, CI, DT); 192 for (auto &Call : DevirtCalls) 193 addVCallToSet(Call, Guid, TypeTestAssumeVCalls, 194 TypeTestAssumeConstVCalls); 195 196 break; 197 } 198 199 case Intrinsic::type_checked_load: { 200 auto *TypeMDVal = cast<MetadataAsValue>(CI->getArgOperand(2)); 201 auto *TypeId = dyn_cast<MDString>(TypeMDVal->getMetadata()); 202 if (!TypeId) 203 break; 204 GlobalValue::GUID Guid = GlobalValue::getGUID(TypeId->getString()); 205 206 SmallVector<DevirtCallSite, 4> DevirtCalls; 207 SmallVector<Instruction *, 4> LoadedPtrs; 208 SmallVector<Instruction *, 4> Preds; 209 bool HasNonCallUses = false; 210 findDevirtualizableCallsForTypeCheckedLoad(DevirtCalls, LoadedPtrs, Preds, 211 HasNonCallUses, CI, DT); 212 // Any non-call uses of the result of llvm.type.checked.load will 213 // prevent us from optimizing away the llvm.type.test. 214 if (HasNonCallUses) 215 TypeTests.insert(Guid); 216 for (auto &Call : DevirtCalls) 217 addVCallToSet(Call, Guid, TypeCheckedLoadVCalls, 218 TypeCheckedLoadConstVCalls); 219 220 break; 221 } 222 default: 223 break; 224 } 225 } 226 227 static bool isNonVolatileLoad(const Instruction *I) { 228 if (const auto *LI = dyn_cast<LoadInst>(I)) 229 return !LI->isVolatile(); 230 231 return false; 232 } 233 234 static bool isNonVolatileStore(const Instruction *I) { 235 if (const auto *SI = dyn_cast<StoreInst>(I)) 236 return !SI->isVolatile(); 237 238 return false; 239 } 240 241 static void computeFunctionSummary(ModuleSummaryIndex &Index, const Module &M, 242 const Function &F, BlockFrequencyInfo *BFI, 243 ProfileSummaryInfo *PSI, DominatorTree &DT, 244 bool HasLocalsInUsedOrAsm, 245 DenseSet<GlobalValue::GUID> &CantBePromoted, 246 bool IsThinLTO) { 247 // Summary not currently supported for anonymous functions, they should 248 // have been named. 249 assert(F.hasName()); 250 251 unsigned NumInsts = 0; 252 // Map from callee ValueId to profile count. Used to accumulate profile 253 // counts for all static calls to a given callee. 254 MapVector<ValueInfo, CalleeInfo> CallGraphEdges; 255 SetVector<ValueInfo> RefEdges, LoadRefEdges, StoreRefEdges; 256 SetVector<GlobalValue::GUID> TypeTests; 257 SetVector<FunctionSummary::VFuncId> TypeTestAssumeVCalls, 258 TypeCheckedLoadVCalls; 259 SetVector<FunctionSummary::ConstVCall> TypeTestAssumeConstVCalls, 260 TypeCheckedLoadConstVCalls; 261 ICallPromotionAnalysis ICallAnalysis; 262 SmallPtrSet<const User *, 8> Visited; 263 264 // Add personality function, prefix data and prologue data to function's ref 265 // list. 266 findRefEdges(Index, &F, RefEdges, Visited); 267 std::vector<const Instruction *> NonVolatileLoads; 268 std::vector<const Instruction *> NonVolatileStores; 269 270 bool HasInlineAsmMaybeReferencingInternal = false; 271 for (const BasicBlock &BB : F) 272 for (const Instruction &I : BB) { 273 if (isa<DbgInfoIntrinsic>(I)) 274 continue; 275 ++NumInsts; 276 // Regular LTO module doesn't participate in ThinLTO import, 277 // so no reference from it can be read/writeonly, since this 278 // would require importing variable as local copy 279 if (IsThinLTO) { 280 if (isNonVolatileLoad(&I)) { 281 // Postpone processing of non-volatile load instructions 282 // See comments below 283 Visited.insert(&I); 284 NonVolatileLoads.push_back(&I); 285 continue; 286 } else if (isNonVolatileStore(&I)) { 287 Visited.insert(&I); 288 NonVolatileStores.push_back(&I); 289 // All references from second operand of store (destination address) 290 // can be considered write-only if they're not referenced by any 291 // non-store instruction. References from first operand of store 292 // (stored value) can't be treated either as read- or as write-only 293 // so we add them to RefEdges as we do with all other instructions 294 // except non-volatile load. 295 Value *Stored = I.getOperand(0); 296 if (auto *GV = dyn_cast<GlobalValue>(Stored)) 297 // findRefEdges will try to examine GV operands, so instead 298 // of calling it we should add GV to RefEdges directly. 299 RefEdges.insert(Index.getOrInsertValueInfo(GV)); 300 else if (auto *U = dyn_cast<User>(Stored)) 301 findRefEdges(Index, U, RefEdges, Visited); 302 continue; 303 } 304 } 305 findRefEdges(Index, &I, RefEdges, Visited); 306 auto CS = ImmutableCallSite(&I); 307 if (!CS) 308 continue; 309 310 const auto *CI = dyn_cast<CallInst>(&I); 311 // Since we don't know exactly which local values are referenced in inline 312 // assembly, conservatively mark the function as possibly referencing 313 // a local value from inline assembly to ensure we don't export a 314 // reference (which would require renaming and promotion of the 315 // referenced value). 316 if (HasLocalsInUsedOrAsm && CI && CI->isInlineAsm()) 317 HasInlineAsmMaybeReferencingInternal = true; 318 319 auto *CalledValue = CS.getCalledValue(); 320 auto *CalledFunction = CS.getCalledFunction(); 321 if (CalledValue && !CalledFunction) { 322 CalledValue = CalledValue->stripPointerCastsNoFollowAliases(); 323 // Stripping pointer casts can reveal a called function. 324 CalledFunction = dyn_cast<Function>(CalledValue); 325 } 326 // Check if this is an alias to a function. If so, get the 327 // called aliasee for the checks below. 328 if (auto *GA = dyn_cast<GlobalAlias>(CalledValue)) { 329 assert(!CalledFunction && "Expected null called function in callsite for alias"); 330 CalledFunction = dyn_cast<Function>(GA->getBaseObject()); 331 } 332 // Check if this is a direct call to a known function or a known 333 // intrinsic, or an indirect call with profile data. 334 if (CalledFunction) { 335 if (CI && CalledFunction->isIntrinsic()) { 336 addIntrinsicToSummary( 337 CI, TypeTests, TypeTestAssumeVCalls, TypeCheckedLoadVCalls, 338 TypeTestAssumeConstVCalls, TypeCheckedLoadConstVCalls, DT); 339 continue; 340 } 341 // We should have named any anonymous globals 342 assert(CalledFunction->hasName()); 343 auto ScaledCount = PSI->getProfileCount(&I, BFI); 344 auto Hotness = ScaledCount ? getHotness(ScaledCount.getValue(), PSI) 345 : CalleeInfo::HotnessType::Unknown; 346 if (ForceSummaryEdgesCold != FunctionSummary::FSHT_None) 347 Hotness = CalleeInfo::HotnessType::Cold; 348 349 // Use the original CalledValue, in case it was an alias. We want 350 // to record the call edge to the alias in that case. Eventually 351 // an alias summary will be created to associate the alias and 352 // aliasee. 353 auto &ValueInfo = CallGraphEdges[Index.getOrInsertValueInfo( 354 cast<GlobalValue>(CalledValue))]; 355 ValueInfo.updateHotness(Hotness); 356 // Add the relative block frequency to CalleeInfo if there is no profile 357 // information. 358 if (BFI != nullptr && Hotness == CalleeInfo::HotnessType::Unknown) { 359 uint64_t BBFreq = BFI->getBlockFreq(&BB).getFrequency(); 360 uint64_t EntryFreq = BFI->getEntryFreq(); 361 ValueInfo.updateRelBlockFreq(BBFreq, EntryFreq); 362 } 363 } else { 364 // Skip inline assembly calls. 365 if (CI && CI->isInlineAsm()) 366 continue; 367 // Skip direct calls. 368 if (!CalledValue || isa<Constant>(CalledValue)) 369 continue; 370 371 // Check if the instruction has a callees metadata. If so, add callees 372 // to CallGraphEdges to reflect the references from the metadata, and 373 // to enable importing for subsequent indirect call promotion and 374 // inlining. 375 if (auto *MD = I.getMetadata(LLVMContext::MD_callees)) { 376 for (auto &Op : MD->operands()) { 377 Function *Callee = mdconst::extract_or_null<Function>(Op); 378 if (Callee) 379 CallGraphEdges[Index.getOrInsertValueInfo(Callee)]; 380 } 381 } 382 383 uint32_t NumVals, NumCandidates; 384 uint64_t TotalCount; 385 auto CandidateProfileData = 386 ICallAnalysis.getPromotionCandidatesForInstruction( 387 &I, NumVals, TotalCount, NumCandidates); 388 for (auto &Candidate : CandidateProfileData) 389 CallGraphEdges[Index.getOrInsertValueInfo(Candidate.Value)] 390 .updateHotness(getHotness(Candidate.Count, PSI)); 391 } 392 } 393 394 std::vector<ValueInfo> Refs; 395 if (IsThinLTO) { 396 auto AddRefEdges = [&](const std::vector<const Instruction *> &Instrs, 397 SetVector<ValueInfo> &Edges, 398 SmallPtrSet<const User *, 8> &Cache) { 399 for (const auto *I : Instrs) { 400 Cache.erase(I); 401 findRefEdges(Index, I, Edges, Cache); 402 } 403 }; 404 405 // By now we processed all instructions in a function, except 406 // non-volatile loads and non-volatile value stores. Let's find 407 // ref edges for both of instruction sets 408 AddRefEdges(NonVolatileLoads, LoadRefEdges, Visited); 409 // We can add some values to the Visited set when processing load 410 // instructions which are also used by stores in NonVolatileStores. 411 // For example this can happen if we have following code: 412 // 413 // store %Derived* @foo, %Derived** bitcast (%Base** @bar to %Derived**) 414 // %42 = load %Derived*, %Derived** bitcast (%Base** @bar to %Derived**) 415 // 416 // After processing loads we'll add bitcast to the Visited set, and if 417 // we use the same set while processing stores, we'll never see store 418 // to @bar and @bar will be mistakenly treated as readonly. 419 SmallPtrSet<const llvm::User *, 8> StoreCache; 420 AddRefEdges(NonVolatileStores, StoreRefEdges, StoreCache); 421 422 // If both load and store instruction reference the same variable 423 // we won't be able to optimize it. Add all such reference edges 424 // to RefEdges set. 425 for (auto &VI : StoreRefEdges) 426 if (LoadRefEdges.remove(VI)) 427 RefEdges.insert(VI); 428 429 unsigned RefCnt = RefEdges.size(); 430 // All new reference edges inserted in two loops below are either 431 // read or write only. They will be grouped in the end of RefEdges 432 // vector, so we can use a single integer value to identify them. 433 for (auto &VI : LoadRefEdges) 434 RefEdges.insert(VI); 435 436 unsigned FirstWORef = RefEdges.size(); 437 for (auto &VI : StoreRefEdges) 438 RefEdges.insert(VI); 439 440 Refs = RefEdges.takeVector(); 441 for (; RefCnt < FirstWORef; ++RefCnt) 442 Refs[RefCnt].setReadOnly(); 443 444 for (; RefCnt < Refs.size(); ++RefCnt) 445 Refs[RefCnt].setWriteOnly(); 446 } else { 447 Refs = RefEdges.takeVector(); 448 } 449 // Explicit add hot edges to enforce importing for designated GUIDs for 450 // sample PGO, to enable the same inlines as the profiled optimized binary. 451 for (auto &I : F.getImportGUIDs()) 452 CallGraphEdges[Index.getOrInsertValueInfo(I)].updateHotness( 453 ForceSummaryEdgesCold == FunctionSummary::FSHT_All 454 ? CalleeInfo::HotnessType::Cold 455 : CalleeInfo::HotnessType::Critical); 456 457 bool NonRenamableLocal = isNonRenamableLocal(F); 458 bool NotEligibleForImport = 459 NonRenamableLocal || HasInlineAsmMaybeReferencingInternal; 460 GlobalValueSummary::GVFlags Flags(F.getLinkage(), NotEligibleForImport, 461 /* Live = */ false, F.isDSOLocal(), 462 F.hasLinkOnceODRLinkage() && F.hasGlobalUnnamedAddr()); 463 FunctionSummary::FFlags FunFlags{ 464 F.hasFnAttribute(Attribute::ReadNone), 465 F.hasFnAttribute(Attribute::ReadOnly), 466 F.hasFnAttribute(Attribute::NoRecurse), F.returnDoesNotAlias(), 467 // FIXME: refactor this to use the same code that inliner is using. 468 // Don't try to import functions with noinline attribute. 469 F.getAttributes().hasFnAttribute(Attribute::NoInline)}; 470 auto FuncSummary = llvm::make_unique<FunctionSummary>( 471 Flags, NumInsts, FunFlags, /*EntryCount=*/0, std::move(Refs), 472 CallGraphEdges.takeVector(), TypeTests.takeVector(), 473 TypeTestAssumeVCalls.takeVector(), TypeCheckedLoadVCalls.takeVector(), 474 TypeTestAssumeConstVCalls.takeVector(), 475 TypeCheckedLoadConstVCalls.takeVector()); 476 if (NonRenamableLocal) 477 CantBePromoted.insert(F.getGUID()); 478 Index.addGlobalValueSummary(F, std::move(FuncSummary)); 479 } 480 481 /// Find function pointers referenced within the given vtable initializer 482 /// (or subset of an initializer) \p I. The starting offset of \p I within 483 /// the vtable initializer is \p StartingOffset. Any discovered function 484 /// pointers are added to \p VTableFuncs along with their cumulative offset 485 /// within the initializer. 486 static void findFuncPointers(const Constant *I, uint64_t StartingOffset, 487 const Module &M, ModuleSummaryIndex &Index, 488 VTableFuncList &VTableFuncs) { 489 // First check if this is a function pointer. 490 if (I->getType()->isPointerTy()) { 491 auto Fn = dyn_cast<Function>(I->stripPointerCasts()); 492 // We can disregard __cxa_pure_virtual as a possible call target, as 493 // calls to pure virtuals are UB. 494 if (Fn && Fn->getName() != "__cxa_pure_virtual") 495 VTableFuncs.push_back({Index.getOrInsertValueInfo(Fn), StartingOffset}); 496 return; 497 } 498 499 // Walk through the elements in the constant struct or array and recursively 500 // look for virtual function pointers. 501 const DataLayout &DL = M.getDataLayout(); 502 if (auto *C = dyn_cast<ConstantStruct>(I)) { 503 StructType *STy = dyn_cast<StructType>(C->getType()); 504 assert(STy); 505 const StructLayout *SL = DL.getStructLayout(C->getType()); 506 507 for (StructType::element_iterator EB = STy->element_begin(), EI = EB, 508 EE = STy->element_end(); 509 EI != EE; ++EI) { 510 auto Offset = SL->getElementOffset(EI - EB); 511 unsigned Op = SL->getElementContainingOffset(Offset); 512 findFuncPointers(cast<Constant>(I->getOperand(Op)), 513 StartingOffset + Offset, M, Index, VTableFuncs); 514 } 515 } else if (auto *C = dyn_cast<ConstantArray>(I)) { 516 ArrayType *ATy = C->getType(); 517 Type *EltTy = ATy->getElementType(); 518 uint64_t EltSize = DL.getTypeAllocSize(EltTy); 519 for (unsigned i = 0, e = ATy->getNumElements(); i != e; ++i) { 520 findFuncPointers(cast<Constant>(I->getOperand(i)), 521 StartingOffset + i * EltSize, M, Index, VTableFuncs); 522 } 523 } 524 } 525 526 // Identify the function pointers referenced by vtable definition \p V. 527 static void computeVTableFuncs(ModuleSummaryIndex &Index, 528 const GlobalVariable &V, const Module &M, 529 VTableFuncList &VTableFuncs) { 530 if (!V.isConstant()) 531 return; 532 533 findFuncPointers(V.getInitializer(), /*StartingOffset=*/0, M, Index, 534 VTableFuncs); 535 536 #ifndef NDEBUG 537 // Validate that the VTableFuncs list is ordered by offset. 538 uint64_t PrevOffset = 0; 539 for (auto &P : VTableFuncs) { 540 // The findVFuncPointers traversal should have encountered the 541 // functions in offset order. We need to use ">=" since PrevOffset 542 // starts at 0. 543 assert(P.VTableOffset >= PrevOffset); 544 PrevOffset = P.VTableOffset; 545 } 546 #endif 547 } 548 549 /// Record vtable definition \p V for each type metadata it references. 550 static void 551 recordTypeIdCompatibleVtableReferences(ModuleSummaryIndex &Index, 552 const GlobalVariable &V, 553 SmallVectorImpl<MDNode *> &Types) { 554 for (MDNode *Type : Types) { 555 auto TypeID = Type->getOperand(1).get(); 556 557 uint64_t Offset = 558 cast<ConstantInt>( 559 cast<ConstantAsMetadata>(Type->getOperand(0))->getValue()) 560 ->getZExtValue(); 561 562 if (auto *TypeId = dyn_cast<MDString>(TypeID)) 563 Index.getOrInsertTypeIdCompatibleVtableSummary(TypeId->getString()) 564 .push_back({Offset, Index.getOrInsertValueInfo(&V)}); 565 } 566 } 567 568 static void computeVariableSummary(ModuleSummaryIndex &Index, 569 const GlobalVariable &V, 570 DenseSet<GlobalValue::GUID> &CantBePromoted, 571 const Module &M, 572 SmallVectorImpl<MDNode *> &Types) { 573 SetVector<ValueInfo> RefEdges; 574 SmallPtrSet<const User *, 8> Visited; 575 bool HasBlockAddress = findRefEdges(Index, &V, RefEdges, Visited); 576 bool NonRenamableLocal = isNonRenamableLocal(V); 577 GlobalValueSummary::GVFlags Flags(V.getLinkage(), NonRenamableLocal, 578 /* Live = */ false, V.isDSOLocal(), 579 V.hasLinkOnceODRLinkage() && V.hasGlobalUnnamedAddr()); 580 581 VTableFuncList VTableFuncs; 582 // If splitting is not enabled, then we compute the summary information 583 // necessary for index-based whole program devirtualization. 584 if (!Index.enableSplitLTOUnit()) { 585 Types.clear(); 586 V.getMetadata(LLVMContext::MD_type, Types); 587 if (!Types.empty()) { 588 // Identify the function pointers referenced by this vtable definition. 589 computeVTableFuncs(Index, V, M, VTableFuncs); 590 591 // Record this vtable definition for each type metadata it references. 592 recordTypeIdCompatibleVtableReferences(Index, V, Types); 593 } 594 } 595 596 // Don't mark variables we won't be able to internalize as read/write-only. 597 bool CanBeInternalized = 598 !V.hasComdat() && !V.hasAppendingLinkage() && !V.isInterposable() && 599 !V.hasAvailableExternallyLinkage() && !V.hasDLLExportStorageClass(); 600 GlobalVarSummary::GVarFlags VarFlags(CanBeInternalized, CanBeInternalized); 601 auto GVarSummary = llvm::make_unique<GlobalVarSummary>(Flags, VarFlags, 602 RefEdges.takeVector()); 603 if (NonRenamableLocal) 604 CantBePromoted.insert(V.getGUID()); 605 if (HasBlockAddress) 606 GVarSummary->setNotEligibleToImport(); 607 if (!VTableFuncs.empty()) 608 GVarSummary->setVTableFuncs(VTableFuncs); 609 Index.addGlobalValueSummary(V, std::move(GVarSummary)); 610 } 611 612 static void 613 computeAliasSummary(ModuleSummaryIndex &Index, const GlobalAlias &A, 614 DenseSet<GlobalValue::GUID> &CantBePromoted) { 615 bool NonRenamableLocal = isNonRenamableLocal(A); 616 GlobalValueSummary::GVFlags Flags(A.getLinkage(), NonRenamableLocal, 617 /* Live = */ false, A.isDSOLocal(), 618 A.hasLinkOnceODRLinkage() && A.hasGlobalUnnamedAddr()); 619 auto AS = llvm::make_unique<AliasSummary>(Flags); 620 auto *Aliasee = A.getBaseObject(); 621 auto AliaseeVI = Index.getValueInfo(Aliasee->getGUID()); 622 assert(AliaseeVI && "Alias expects aliasee summary to be available"); 623 assert(AliaseeVI.getSummaryList().size() == 1 && 624 "Expected a single entry per aliasee in per-module index"); 625 AS->setAliasee(AliaseeVI, AliaseeVI.getSummaryList()[0].get()); 626 if (NonRenamableLocal) 627 CantBePromoted.insert(A.getGUID()); 628 Index.addGlobalValueSummary(A, std::move(AS)); 629 } 630 631 // Set LiveRoot flag on entries matching the given value name. 632 static void setLiveRoot(ModuleSummaryIndex &Index, StringRef Name) { 633 if (ValueInfo VI = Index.getValueInfo(GlobalValue::getGUID(Name))) 634 for (auto &Summary : VI.getSummaryList()) 635 Summary->setLive(true); 636 } 637 638 ModuleSummaryIndex llvm::buildModuleSummaryIndex( 639 const Module &M, 640 std::function<BlockFrequencyInfo *(const Function &F)> GetBFICallback, 641 ProfileSummaryInfo *PSI) { 642 assert(PSI); 643 bool EnableSplitLTOUnit = false; 644 if (auto *MD = mdconst::extract_or_null<ConstantInt>( 645 M.getModuleFlag("EnableSplitLTOUnit"))) 646 EnableSplitLTOUnit = MD->getZExtValue(); 647 ModuleSummaryIndex Index(/*HaveGVs=*/true, EnableSplitLTOUnit); 648 649 // Identify the local values in the llvm.used and llvm.compiler.used sets, 650 // which should not be exported as they would then require renaming and 651 // promotion, but we may have opaque uses e.g. in inline asm. We collect them 652 // here because we use this information to mark functions containing inline 653 // assembly calls as not importable. 654 SmallPtrSet<GlobalValue *, 8> LocalsUsed; 655 SmallPtrSet<GlobalValue *, 8> Used; 656 // First collect those in the llvm.used set. 657 collectUsedGlobalVariables(M, Used, /*CompilerUsed*/ false); 658 // Next collect those in the llvm.compiler.used set. 659 collectUsedGlobalVariables(M, Used, /*CompilerUsed*/ true); 660 DenseSet<GlobalValue::GUID> CantBePromoted; 661 for (auto *V : Used) { 662 if (V->hasLocalLinkage()) { 663 LocalsUsed.insert(V); 664 CantBePromoted.insert(V->getGUID()); 665 } 666 } 667 668 bool HasLocalInlineAsmSymbol = false; 669 if (!M.getModuleInlineAsm().empty()) { 670 // Collect the local values defined by module level asm, and set up 671 // summaries for these symbols so that they can be marked as NoRename, 672 // to prevent export of any use of them in regular IR that would require 673 // renaming within the module level asm. Note we don't need to create a 674 // summary for weak or global defs, as they don't need to be flagged as 675 // NoRename, and defs in module level asm can't be imported anyway. 676 // Also, any values used but not defined within module level asm should 677 // be listed on the llvm.used or llvm.compiler.used global and marked as 678 // referenced from there. 679 ModuleSymbolTable::CollectAsmSymbols( 680 M, [&](StringRef Name, object::BasicSymbolRef::Flags Flags) { 681 // Symbols not marked as Weak or Global are local definitions. 682 if (Flags & (object::BasicSymbolRef::SF_Weak | 683 object::BasicSymbolRef::SF_Global)) 684 return; 685 HasLocalInlineAsmSymbol = true; 686 GlobalValue *GV = M.getNamedValue(Name); 687 if (!GV) 688 return; 689 assert(GV->isDeclaration() && "Def in module asm already has definition"); 690 GlobalValueSummary::GVFlags GVFlags(GlobalValue::InternalLinkage, 691 /* NotEligibleToImport = */ true, 692 /* Live = */ true, 693 /* Local */ GV->isDSOLocal(), 694 GV->hasLinkOnceODRLinkage() && GV->hasGlobalUnnamedAddr()); 695 CantBePromoted.insert(GV->getGUID()); 696 // Create the appropriate summary type. 697 if (Function *F = dyn_cast<Function>(GV)) { 698 std::unique_ptr<FunctionSummary> Summary = 699 llvm::make_unique<FunctionSummary>( 700 GVFlags, /*InstCount=*/0, 701 FunctionSummary::FFlags{ 702 F->hasFnAttribute(Attribute::ReadNone), 703 F->hasFnAttribute(Attribute::ReadOnly), 704 F->hasFnAttribute(Attribute::NoRecurse), 705 F->returnDoesNotAlias(), 706 /* NoInline = */ false}, 707 /*EntryCount=*/0, ArrayRef<ValueInfo>{}, 708 ArrayRef<FunctionSummary::EdgeTy>{}, 709 ArrayRef<GlobalValue::GUID>{}, 710 ArrayRef<FunctionSummary::VFuncId>{}, 711 ArrayRef<FunctionSummary::VFuncId>{}, 712 ArrayRef<FunctionSummary::ConstVCall>{}, 713 ArrayRef<FunctionSummary::ConstVCall>{}); 714 Index.addGlobalValueSummary(*GV, std::move(Summary)); 715 } else { 716 std::unique_ptr<GlobalVarSummary> Summary = 717 llvm::make_unique<GlobalVarSummary>( 718 GVFlags, GlobalVarSummary::GVarFlags(false, false), 719 ArrayRef<ValueInfo>{}); 720 Index.addGlobalValueSummary(*GV, std::move(Summary)); 721 } 722 }); 723 } 724 725 bool IsThinLTO = true; 726 if (auto *MD = 727 mdconst::extract_or_null<ConstantInt>(M.getModuleFlag("ThinLTO"))) 728 IsThinLTO = MD->getZExtValue(); 729 730 // Compute summaries for all functions defined in module, and save in the 731 // index. 732 for (auto &F : M) { 733 if (F.isDeclaration()) 734 continue; 735 736 DominatorTree DT(const_cast<Function &>(F)); 737 BlockFrequencyInfo *BFI = nullptr; 738 std::unique_ptr<BlockFrequencyInfo> BFIPtr; 739 if (GetBFICallback) 740 BFI = GetBFICallback(F); 741 else if (F.hasProfileData()) { 742 LoopInfo LI{DT}; 743 BranchProbabilityInfo BPI{F, LI}; 744 BFIPtr = llvm::make_unique<BlockFrequencyInfo>(F, BPI, LI); 745 BFI = BFIPtr.get(); 746 } 747 748 computeFunctionSummary(Index, M, F, BFI, PSI, DT, 749 !LocalsUsed.empty() || HasLocalInlineAsmSymbol, 750 CantBePromoted, IsThinLTO); 751 } 752 753 // Compute summaries for all variables defined in module, and save in the 754 // index. 755 SmallVector<MDNode *, 2> Types; 756 for (const GlobalVariable &G : M.globals()) { 757 if (G.isDeclaration()) 758 continue; 759 computeVariableSummary(Index, G, CantBePromoted, M, Types); 760 } 761 762 // Compute summaries for all aliases defined in module, and save in the 763 // index. 764 for (const GlobalAlias &A : M.aliases()) 765 computeAliasSummary(Index, A, CantBePromoted); 766 767 for (auto *V : LocalsUsed) { 768 auto *Summary = Index.getGlobalValueSummary(*V); 769 assert(Summary && "Missing summary for global value"); 770 Summary->setNotEligibleToImport(); 771 } 772 773 // The linker doesn't know about these LLVM produced values, so we need 774 // to flag them as live in the index to ensure index-based dead value 775 // analysis treats them as live roots of the analysis. 776 setLiveRoot(Index, "llvm.used"); 777 setLiveRoot(Index, "llvm.compiler.used"); 778 setLiveRoot(Index, "llvm.global_ctors"); 779 setLiveRoot(Index, "llvm.global_dtors"); 780 setLiveRoot(Index, "llvm.global.annotations"); 781 782 for (auto &GlobalList : Index) { 783 // Ignore entries for references that are undefined in the current module. 784 if (GlobalList.second.SummaryList.empty()) 785 continue; 786 787 assert(GlobalList.second.SummaryList.size() == 1 && 788 "Expected module's index to have one summary per GUID"); 789 auto &Summary = GlobalList.second.SummaryList[0]; 790 if (!IsThinLTO) { 791 Summary->setNotEligibleToImport(); 792 continue; 793 } 794 795 bool AllRefsCanBeExternallyReferenced = 796 llvm::all_of(Summary->refs(), [&](const ValueInfo &VI) { 797 return !CantBePromoted.count(VI.getGUID()); 798 }); 799 if (!AllRefsCanBeExternallyReferenced) { 800 Summary->setNotEligibleToImport(); 801 continue; 802 } 803 804 if (auto *FuncSummary = dyn_cast<FunctionSummary>(Summary.get())) { 805 bool AllCallsCanBeExternallyReferenced = llvm::all_of( 806 FuncSummary->calls(), [&](const FunctionSummary::EdgeTy &Edge) { 807 return !CantBePromoted.count(Edge.first.getGUID()); 808 }); 809 if (!AllCallsCanBeExternallyReferenced) 810 Summary->setNotEligibleToImport(); 811 } 812 } 813 814 if (!ModuleSummaryDotFile.empty()) { 815 std::error_code EC; 816 raw_fd_ostream OSDot(ModuleSummaryDotFile, EC, sys::fs::OpenFlags::F_None); 817 if (EC) 818 report_fatal_error(Twine("Failed to open dot file ") + 819 ModuleSummaryDotFile + ": " + EC.message() + "\n"); 820 Index.exportToDot(OSDot); 821 } 822 823 return Index; 824 } 825 826 AnalysisKey ModuleSummaryIndexAnalysis::Key; 827 828 ModuleSummaryIndex 829 ModuleSummaryIndexAnalysis::run(Module &M, ModuleAnalysisManager &AM) { 830 ProfileSummaryInfo &PSI = AM.getResult<ProfileSummaryAnalysis>(M); 831 auto &FAM = AM.getResult<FunctionAnalysisManagerModuleProxy>(M).getManager(); 832 return buildModuleSummaryIndex( 833 M, 834 [&FAM](const Function &F) { 835 return &FAM.getResult<BlockFrequencyAnalysis>( 836 *const_cast<Function *>(&F)); 837 }, 838 &PSI); 839 } 840 841 char ModuleSummaryIndexWrapperPass::ID = 0; 842 843 INITIALIZE_PASS_BEGIN(ModuleSummaryIndexWrapperPass, "module-summary-analysis", 844 "Module Summary Analysis", false, true) 845 INITIALIZE_PASS_DEPENDENCY(BlockFrequencyInfoWrapperPass) 846 INITIALIZE_PASS_DEPENDENCY(ProfileSummaryInfoWrapperPass) 847 INITIALIZE_PASS_END(ModuleSummaryIndexWrapperPass, "module-summary-analysis", 848 "Module Summary Analysis", false, true) 849 850 ModulePass *llvm::createModuleSummaryIndexWrapperPass() { 851 return new ModuleSummaryIndexWrapperPass(); 852 } 853 854 ModuleSummaryIndexWrapperPass::ModuleSummaryIndexWrapperPass() 855 : ModulePass(ID) { 856 initializeModuleSummaryIndexWrapperPassPass(*PassRegistry::getPassRegistry()); 857 } 858 859 bool ModuleSummaryIndexWrapperPass::runOnModule(Module &M) { 860 auto *PSI = &getAnalysis<ProfileSummaryInfoWrapperPass>().getPSI(); 861 Index.emplace(buildModuleSummaryIndex( 862 M, 863 [this](const Function &F) { 864 return &(this->getAnalysis<BlockFrequencyInfoWrapperPass>( 865 *const_cast<Function *>(&F)) 866 .getBFI()); 867 }, 868 PSI)); 869 return false; 870 } 871 872 bool ModuleSummaryIndexWrapperPass::doFinalization(Module &M) { 873 Index.reset(); 874 return false; 875 } 876 877 void ModuleSummaryIndexWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const { 878 AU.setPreservesAll(); 879 AU.addRequired<BlockFrequencyInfoWrapperPass>(); 880 AU.addRequired<ProfileSummaryInfoWrapperPass>(); 881 } 882